Vaccination in Poultry

Vaccines

Vaccines

Vaccine

A vaccine is in essence, a fluid suspension of antigen, capable of stimulating the production of corresponding antibodies.

There are two types:

Vaccines are generally species specific, sometimes they are strain specific. It is essential that the proper strain is used against an infection when there are strain differences. For example, vaccination against type A foot and mouth disease will only control type A foot and mouth disease in the animal.

Vaccines are issued from laboratories either as fluids ready for immediate use, or in a freeze-dried state, in which case it is necessary for them to be suspended in sterile normal saline or sterile distilled water before injection. The advantage of freeze-dried vaccine is that they can survive transport and adverse environmental condition better than wet vaccine. In all cases the greatest care is necessary in handling a vaccine between manufacture and actual use on an animal. The shortest time possible between the two is best.

Usually, vaccines have a limited life, and the date of manufacture and expiry are usually plainly stamped on the label. Vaccines outside the expiry date should not be used. Unless the directions for use specifically states otherwise, they should be kept in refrigeration. A few are capable of being kept in a cool place, but this is the exception. The instructions on the container are usually clear on these points. With every vaccine, the administration route should be clearly indicated by the manufacturer. With most, the subcutaneous route is preferred and often the location on the body in which the injection should be given is also indicated. With some the intra-muscular route is more effective because entry into the circulation is delayed thus minimizing the chance of tissue breakdown leading to ulceration or abscess formation.

Where vaccination of poultry is concerned, the vaccine is actually mixed with the food or water and ingested.

The dose rate must always be carefully observed. Very often the size, bread, age and sex of an animal have vital bearing on the dose and the strain of vaccine to be used. The manufacturer’s recommendation should always be followed.

Vaccination Methods in Poultry

  1. Vaccination Through Drinking Water

In this method, the vaccine can be put in the chicks’ drinking water. However, tap water contains chlorine which affects the effectiveness of the vaccine. It is advisable to use water direct from the river, well or borehole drawn with a bucket.

In case there is only tap water available, add some powdered milk to tap water before putting in the vaccine, so that chlorine is neutralized. For example, for 100 chickens, a sachet of cowbell milk weighing 40g should be added to 15 litres of drinking water and mixed with the vaccine. Never use tap water!!!!

Steps To Follow When Using Drinking Water Method

  • Withdraw water from the chickens for 3 hours to make them thirsty. This will help to ensure that the vaccine is taken as quickly as possible when presented to them because high temperatures also affect the effectiveness of the vaccine.
  • Add milk to water to be used and put the milk solution under a shade and wait for 30 minutes.
  • While you are waiting, wash the drinkers thoroughly with clean water.
  • Then ensure that birds take equal amounts of vaccine water. Distribute the vaccine water in the drinkers equally. In the poultry house, the drinkers should also be placed evenly.
  • After they have finished the vaccine water, wait for at least an hour before putting back the previous water they had been drinking, to ensure that the vaccine water taken has been absorbed into their bodies.

Example of Calculations Used In Vaccination

Technical starting points;

  • Every bird should receive 1 dose of the vaccine
  • The vaccine should be dissolved in the drinking water, using 1L of water per day of age for every 1000 birds.
  • Assuming you have bought a vial of vaccine containing 500 doses and you want to prepare the vaccine for 300 birds which are 4 weeks old.

Procedure

  1. It is very difficult to get 300 doses of vaccine out of vial of 500, so first prepare a solution for 500 doses. Then take as much vaccine as required and throw away the rest.
  2. 500 doses are enough or meant for 500 birds.
  3. The amount of drinking water needed must be calculated first.
  4. Since the birds are 4 weeks old (28 days), you need 28L of water if they are 1000 in number.
  5. If you have 500 birds you need 14L (half of the 28L)

1 day         ——–‣ 1 litre for 1000 birds

28 days     ——–‣ 28 litres for 1000 birds

1000 birds ——–‣ 28 litres

500 birds  ———‣ 14 litres

  1. Mix the vaccine with 14 litres of water. You have a solution which is sufficient for vaccinating 500 birds aged 28 days.
  2. How much of this solution do you need?

You only have 300 birds and not 500 birds.

Solution

500 birds   ———‣ 14L of solution

300 birds ———‣ X

X = 300 x 14/500 = 8.4L

  1. This means you have to use only 8.4 litres of the prepared vaccine solution.
  2. The remaining 5.6 (14 – 8.4) litres should be disposed of.
  3. Vaccination Through The Eyes, Nostrils or Mouth

This method involves placing the vaccine in the eye or nostril of the chicken, in order for the vaccine to get into the digestive system. There is a bottle called dropper to use in this method. This is channelled into the throat. Vaccine can even be dropped into the mouths, but this is time consuming.

When using this method, be careful not to let the tip of the dropper bottle you are using, touch the surface of the chick’s eyes or else it will damage it. Also, do not hold the bottle with full palm of your hand because this will warm-up the vaccine quickly and affect its effectiveness.

  1. Through The Chicken’s Muscle Skin or Blood Veins

This method is done by injection and is commonly used when vaccinating Layers and it requires people who are trained. So ensure that you know the method well, or call a veterinary doctor or an agricultural extension officer to administer it.

  1. Spray Method

For the first three weeks, the birds are not drinking enough water. So the spray method is the most effective.

Vaccination Schedule and Report

Age to be vaccinated Date to be vaccinated Date of actual vaccination Person who vaccinated Vaccinated against Type of vaccine Method of vaccination Vaccine No.
               
               
               
               

Table 1. Vaccination schedule and report for poultry

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Disease Control and Biosecurity in Broiler Chickens

Today I want to share my experience in poultry on disease control and biosecurity on farms.
Most diseases are brought on the farm. Very rarely do disease emerge on the farm. This is why biosecurity is very important.

Disease can be defined as lack of ease; any abnormality in the state of normal health is in effect disease.

Sometimes in our excitement to show off our progress, we have allowed visitors into or near our chicken runs without carrying out proper biosecurity safety measures:

  • Do not allow visitors or anyone not working at the poultry house have access to your chickens.
  • All poultry workers should have uniforms, two pairs. One for working inside the poultry houses; only take it home for washing and another for outside the poultry house. Same with boots.
  • Encourage poultry workers to bath before they start a new day. If possible provide bath facilities and soap at the farm.
  • Put footbaths at entry pointes to poultry houses and also for vehicles at the farm gate. You can also have a sprayer for vehicles entering the farm.
  • Change disinfectants in the footbaths regularly. I change mine every third day depending on traffic!

As stated earlier, most diseases are brought from outside the farm. We shall now try to identify who in particular are the likely agents:

  • Our visitors, some of whom also rear chickens. It is not advisable to allow these near the chickens if biosecurity measures have not been taken i.e. Bath and change of clothing.
  • Our so called consultants who visit several farms. Because we trust them a lot, we tend to relax on biosecurity.
  • The people we hire to come and help with tasks like vaccinations and debeaking. These too visit several farms and pose a lot of risk. If they come with their equipment, make sure you sterilise it yourself. It’s actually advisable to buy disposable syringes and needles.
  • The customers who come to buy our products. These should not be allowed near the poultry houses. The most risky are times we are cropping, especially the Layers. Those vehicles and cages need to be thoroughly disinfected. If possible don’t allow them on the farm.

We allow buyers in our chicken houses to choose at very great risk to our remaining flock.
What I have written above is from personal experience and I would appreciate others also sharing their experiences and expertise.

Disease Control and Treatment in Poultry

Introduction

Disease can be defined as any change or impairment of normal body function that affects the chickens’ ability to survive, grow or reproduce. An understanding of the cause of a disease and its method of spread (transmission) will assist in controlling it. Knowledge of the clinical signs of a disease and the characteristics of lesions found at Post-mortem will help in its diagnosis and instituting preventative measures.

Signs of Unhealthy Birds/Sick Birds

  • Tiredness and lifelessness
  • Dull eyes and comb
  • Abnormalities in gait
  • Sit or lie down
  • Eat and drink less
  • Lay less or stop laying eggs
  • Ruffled and loose feathers
  • Wet droppings with blood or worms, diarrhoea
  • Cough, sneeze and breathe noisily

Common Poultry Diseases

Infectious diseases are caused by organisms that can be transmitted from one bird to another. Such organisms include; viruses, bacteria, fungi and protozoans. Other infectious organisms are external (lice, fleas and ticks) or internal (roundworms, tapeworms, flukes) parasites.

  1. New Castle Disease. This disease is zoonosis i.e. it infects both humans and birds. In humans it causes conjunctivitis. It was imported to Zambia.

Cause: Virus

Host: Birds

Transmission: Contact with infective materials including secretions and excretions

Signs: Respiratory difficulties, digestive problems, drop in laying eggs, high and low mortality

Diagnosis: Signs, history, viral isolation from trachea or cloaca swab, gross lesions (enlarged spleen)

Treatment: N/A

Prevention: Biosecurity, proper hygiene and feed management, vaccination

New Castle Disease

New Castle Disease

  1. Marek’s Disease. This disease affects the nervous system. Chicks cannot stand because of nervous problem. Mortality rate varies.

Cause: Virus

Host: Chickens

Transmission: Inhalation of virus which is in scurf

Signs: Paralysis of legs

Diagnosis: signs, swollen nerve or liver, tumour of lymph nodes in post-mortem exam

Treatment: N/A

Prevention: Biosecurity, proper hygiene control and feed management, vaccination

Marek Disease

Marek Disease

  1. Infectious Bursal Disease (Gamboro). It is called Gumboro because it was discovered in a city called Gumboro. Mortality rate varies.

Cause: Virus

Host: Chickens

Transmission: Oral transmission of virus in faeces

Signs: Dullness, diarrhoea

Diagnosis: serum, sampling bursa of fabricius

Treatment: N/A

When poultry recovers naturally, it does not grow well because they do not have strong immunity.

Prevention: Biosecurity, proper hygiene control and feed management, vaccination

Gumboro Symptoms in Male Chicken

Gumboro Symptoms in Male Chicken

  1. Fowl Cholera

Cause: Bacteria (Pasteurella multocida)

Host: Poultry

Transmission: Inhalation of bacteria in secretion

Signs: Respiratory difficulties, diarrhoea

Diagnosis: Signs, isolation from necropsy specimen

Treatment: N/A

Prevention: Vaccination

Fowl Cholera

Fowl Cholera

  1. Coccidiosis

Cause: Eimeria tenella (destroys membrane and cells of intestines)

Host: Chickens

Transmission: Oral transmission

Signs: Diarrhoea

Diagnosis: Faecal examination, signs

Treatment: Sulpha drug

Prevention: Clean pen using boiling water to destroy oocyst

Coccidiosis in Chickens

Coccidiosis in Chickens

In many cases, disease results from a combination of factors such as, nutrition, environmental factors and flock management. All these have a direct and important influence on the health and productivity of chickens.

Factors That Can Easily Lead To Disease

  1. General Condition
    • Age
    • Stress
    • Inherited characteristics
    • Susceptibility to disease
  2. Environment
    • Climate (temperature, rain, wind)
    • Housing Conditions
    • Availability of water and feed
    • Feed Quality
    • Air Quality
  3. Infectious Agents
    • Viruses
    • Bacteria
    • Mycoplasmas
    • Fungi
    • Parasites

Costs Associated with Disease

  • Mortality
  • Morbidity
  • Reduced productivity- weight gain/egg production
  • Downgrading at processing

Some important takeaways are:

  • Separate chicks from adult birds except from the mother hen
  • Vaccinate chicks against the most important diseases and revaccinate where necessary
  • Isolate and treat sick birds – if medication is not available then kill the sick birds
  • Burn or bury killed birds
  • Keep different species of poultry for example hens, turkeys, pigeons, ducks and guinea fowls separate

This guide is available to download as a free PDF. Download Disease Control and Treatment in Poultry now. Feel free to copy and share this with your friends and family.

Sustainable Integrated Pest Management for Tomato

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Tomato damaged by Black Mold

INTRODUCTION

Integrated Pest Management (IPM) is the coordinated use of pest and environmental information with available pest control methods to prevent unacceptable levels of pest damage by the most economical means and with the least possible hazard to people, property, and the environment. IPM is a sustainable approach to pest management that uses knowledge of pest, crop and environmental conditions to select the best combination of the following IPM tactics:

  • Cultural control – modifying farming practices to decrease pest problems
  • Biological control – use of beneficial organisms to regulate pests
  • Chemical control – use of chemical pesticides appropriately
  • Physical control – killing pests directly or by disrupting their environments

TOMATO PESTS AND THEIR CONTROL

Insects - Nematodes Affecting Tomatoes

Insects/ Nematodes Affecting Tomatoes

Cutworms are green or brown caterpillars that curl into a C shape when disturbed. They eat young plants at the soil line at night, and can leave a healthy seedling cut off entirely and lying on the ground.

Controls: Eliminate weeds around garden beds at least two weeks before planting. Hand-picking cutworms at night may help, or you can protect seedlings with cardboard collars or one or more toothpicks (inserted close and parallel to the stem).

Aphids affect tomatoes, especially vigorously growing ones.

Controls: A handful of aphids won’t hurt a healthy tomato plant, but if new leaves are curling or the shoots are coated in aphids, crushing aphids by hand or blasting them off with a strong jet of water will control them.

Hornworms are voracious eaters of tomato plants and fruit. They are large (1” to 4”) green caterpillars with a prominent horn on the tail end; they will eat leaves, small stems, and fruit, sometimes stripping young plants entirely. The mature caterpillars drop to the ground and pupate in the soil over the winter.

Fruitworms, also known as corn earworms, are about an inch long, pale green or brown, sometimes striped. They burrow under the stem end of tomato fruit to create messy warrens full of brown frass.

Controls: Hand-picking caterpillars in the early evening, when they are most active, is quite effective.

Rototill or thickly sheet-mulch beds to destroy pupae between seasons. Bacillus thuringiensis or spinosad sprays, both organic, can help with control. General predators, such as praying mantises or wasps, also reduce populations.

Stinkbugs are an annoyance to tomato growers, as their feeding can cause corky white patches under the skin of ripe tomatoes. These patches don’t peel easily when cooking or canning the fruit.

Controls: Hand-pick stinkbugs or snip them with garden shears; a bucket of soapy water held under them can help, as they often drop when disturbed. Eliminate weeds around garden beds at least two weeks before planting. Insecticides are not recommended.

Snails and Slugs can be a problem, especially if plants are on or near the ground. They rarely bother foliage on mature tomatoes, but they can eat large chunks of ripening fruit if they have easy access.

Controls: Keep tomato plants and especially fruit off the ground by using cages or staking.

TOMATO DISEASES AND THEIR CONTROL

Fungal and Bacterial Pathogens of Tomatoes

Fungal and Bacterial Pathogens of Tomato

Early Blight is a common leaf spot caused by the fungus Alternaria solani. Dark brown spots with broad yellow haloes appear on the leaves, and concentric rings can be found in the spots under bright light.

Stems and fruit can also be infected. It often progresses from the bottom of the plant upward. Cool humid weather or overhead irrigation encourage Early Blight, which is spread by splashing water and germinates on moist leaves.

Controls: Avoid getting water on the leaves whenever possible, change the locations where you plant your tomatoes, mulch well around each plant, and clear away all dead or infected plant material at the end of each season. Picking off infected leaves may slow the progression of the disease until the weather is more favourable.

Speck and Spot are bacterial diseases with similar symptoms, causing small black specks or patches on leaves, stems, and fruit. They can be distinguished from Early Blight by the water-soaked appearance of the spots, and the fact that the spots don’t cross the larger veins. Like Early Blight, these bacterial diseases are spread by water, and they can overwinter in soil and on debris from the previous season.

Controls: Prevent and control these diseases as you would Early Blight, above. Bacterial spots stop spreading in dry, warm weather. Chemical controls are usually not needed.

Late Blight is caused by Phytophthora infestans, a fungal disease most famous for the Irish potato famine. It is just as serious in tomatoes, causing dark green to purple-brown water-soaked spots that grow quickly on leaves and stems. The underside of infected leaves will sometimes have whitish powdery spores. Fruit turns brown but stays firm. The fungus thrives during periods of high humidity and mild temperatures (60-78° F). Once it gets going, it can kill a plant very rapidly and spread to other tomatoes, peppers, or potatoes.

Controls: Avoid sprinkler irrigation, very dense planting, or other things which keep humidity high.

Remove volunteer potatoes or tomatoes, and clean up debris at the end of the season. Mulching may help prevent initial infection.

Fusarium Wilt is caused by a soil-borne fungus (Fusarium oxysporum) which infects the roots and stems of tomatoes. Leaves yellow and wilt without spots, sometimes only on one side of the plant, and brownish streaks creep up the inside of the main stem and into the branches. Symptoms are worst in warm weather, especially as the first fruits are getting large. It is usually fatal to infected plants.

Controls: Fusarium can survive a long time in the soil, and it is spread by shoes, garden tools, and anything else which moves soil around. The typical solution in an infected garden is to grow resistant varieties (look for an F or FF on the variety label); no systematic resistance trials have been done for heirloom varieties. Cleaning up all tomato debris, including old roots, and solarizing the soil may help.

Verticillium Wilt (Verticillium dahliae) is similar to Fusarium Wilt, and it can be difficult to tell them apart, though Verticillium prefers cool temperatures rather than warmth.

Controls: Management is the same as for Fusarium Wilt; resistant varieties carry a V on the label.

Powdery Mildew can appear in late summer or fall as the nights cool, but it rarely causes much damage.

Irregular yellow blotches with a faint coating of white powder form on the leaves, and eventually cause brown dead patches.

Controls: No control is necessary on mature plants, but in the case of young or severely affected plants, sulphur dust provides good control.

SUMMARY

Pesticides and application costs are nearly 25% of tomato grower’s expenses. Despite all the planning and preparation that goes into planting a garden, insects and diseases can still frustrate even the best gardeners.

REFERENCES

Integrated Pest Management (IPM)- Rodents

Pests and Diseases for Home Gardeners

Precautions & Application Tips on Specific Pesticides

This guide is available to download as a free PDF. Download Sustainable-Integrated-Pest-Management-for-Tomato now. Feel free to copy and share this with your friends and family.

Plant Breeding, Genetic Engineering and Quality of Cultivars

INTRODUCTION

AMONG the variety of agricultural and technical factors that determine the quality of field crops, fruit and vegetables, the choice of a specific cultivar by the grower, i.e., the choice and combination of genes controlling economically important traits, may be considered the most initial step for defining quality and productivity. It is the factor that determines farmers’ potential output long before any other agricultural measures are taken and even before the seed is sown in the field or greenhouse. As a consequence, the breeding of a cultivar that is adapted to specific demands of the farmer and the consumer may be considered as a preharvest factor per se, even if certain quality characters of this cultivar apply to postharvest stages.

The classical approach for breeding cultivars is to select suitable phenotypes or mutants, which are then crossed, selfed, cloned or combined with populations depending on their reproductive biology (Table 2.1). A major drawback of this approach is that for most agronomically important traits, the phenotypic variance is the base for selection, which, however, is not only composed of the genotypic variance but also comprises an environmental component as well as interactions between genotypes and environment. This tends to obscure selection progress and is one of the reasons why breeding for quantitatively or polygenically inherited traits is so tedious and time-consuming.

Table 2.1. Approaches in Plant Breeding

Classical Breeding

• Selection of phenotypes

• Intercrossing, selfing, vegetative cloning of favourable phenotypes

• Inbred line or population or clonal varieties

Marker-Assisted Selection

• Mapping of quantitative trait loci (QTL) (e.g., solids content and pH of

tomato pulp, chips quality of potato, β-glucan content of barley)

• Selection of genotypes instead of phenotypes

Genetic Engineering

• Gene suppression by antisense or cosuppression

• Expression of foreign genes (constitutive or tissue-specific)

• Overexpression of native genes

 

In addition, a combination of positively acting polygenes of one specific genetic background is difficult if not impossible because of recombinational dispersion of genes in each sexual generation. Biotechnology and molecular biology have provided exciting new tools to the plant breeder, which may help to circumvent some of the obstacles in the breeding of complex traits.

BIOTECHNOLOGY AND PLANT BREEDING

Plant breeding has been impacted during the last two decades by a number of technological developments that may enrich plant breeders’ repertoire to achieve breeding progress more quickly or conveniently or even allow them to design plant traits that were impossible to create by classical breeding methods. Besides classical breeding methods, biotechnological breakthroughs like in vitro fusion and regeneration of plant cells, and marker-assisted selection (MAS) of monogenic traits as well as the tracing of quantitative trait loci (QTL) by use of molecular genomic markers have gained increased importance for plant breeding (Table 2.1). In tomato, e.g., QTL for quality traits such as soluble solids content, fruit mass, fruit pH, and fruit shape have been mapped (Grandillo et al., 1996). In potato, traits such as chip colour, tuberization and tuber dormancy may be traced by molecular markers. For these characters, between 5 and 13 QTL have been identified. In some cases relatively high individual effects of a single QTL were found. Also, the total phenotypic variation of a given trait that could be accounted for by combined assessment of these QTLs was in the range of 50% or higher, which demonstrates the potential of molecular markers as a selection tool for tracing quantitatively inherited traits.

Limitations of MAS relate to the fact that applicability of these markers often depends heavily on the specific experimental population in which they were identified, as well as on the extent of marker polymorphism, linkage disequilibria and linkage phases among the individuals under selection. In addition, specific marker technology and know-how is required for routine marker-assisted selection programs, rendering the cost efficiency of MAS uncertain for crops that are not of major economic importance.

As a more recent achievement, transformation methods enabling the transfer of any isolated gene into virtually any important cultivated plant species have opened the toolbox of genetic engineering as a novel opportunity to the plant breeder. Plant transformation technology allows breeders to circumvent some restrictions of classical breeding methods.

In particular, gene technology offers the breeder the following promises:

  1. The manipulation of native and the introduction of foreign specific genes not only allow for modification of simply inherited traits like herbicide tolerance and virus and insect resistance, they also open new horizons for directed adjustment of even traits that display very complex inheritance in native systems. Thus, in some instances approaches of factorial instead of quantitative genetics may be sufficient for the breeder to cope with the improvement of specific quality or even yield-determining characters.
  2. Genetic engineering provides “added value” by transferring specific genes to cultivars that have been subject to intensive breeding efforts and, thus, are highbred already with respect to yield, uniformity, disease resistance, and so on. This aspect cannot be underestimated since any modern cultivar is defined by a complex of characteristics that have been assembled during years or decades of breeding work. In classical breeding new or better characteristics have to be introduced by crosses, giving rise to sexual recombination and, as a consequence, to dispersion of the valuable trait complexes in the progeny. In addition, undesired genes from the donor cross parent are also introduced, which have to be eliminated by successive backcrosses to the cultivar parent. It is for this reason that plant breeders tend to prevent the introduction of “exotic,” i.e., agronomically unadapted donor genotypes into their highbred elite gene pools. The addition or modification of single genes to elite lines by genetic engineering would help to alleviate these difficulties.
  3. Genetic engineering speeds up the breeding process and provides better cultivars to farmers and consumers with less effort of labour and time. There is expectation that the concerted use of biotechnological methods may substantially shorten the breeding cycle for a given crop, which presently is in the range of 10–15 years or, for some woody fruit species, extends to 25 years. This time span appears quite large if one considers the need for the breeder to adapt his breeding goals to the rapidly changing requirements by growers, industry, traders and consumers.

CONCLUSION

It should be stressed, however, that biotechnological methods such as genetic engineering are not, and most probably will not become, self-sufficient in breeding better cultivars. Rather, they may provide additional tools to the breeder who will still have to apply classical breeding methods, which continue to constitute the backbone of plant breeding.

The genetic engineering approach relies on (1) a detailed knowledge of the biochemical pathways that generate the quality trait, (2) the isolation of genes that have an impact on these pathways, and (3) the transfer and expression of one or several of these genes into crops in order to specifically modify the trait of interest. A number of strategies are available to genetically engineer a trait.

First, if the plant to be modified expresses a gene leading to undesirable characteristics, this gene may be shut down by introducing the same gene once more into the plant but in the opposite direction so that transcription of the native gene is neutralized by its antisense counterpart.

Gene silencing can also be achieved by introducing a truncated version of the native gene in either direction, a phenomenon that is called cosuppression. Second, if expression and not suppression of genes is desired, then novel genes that are not originally owned by the plant may be introduced from any source organism and may be expressed either constitutively or specifically in a tissue or developmental stage. Finally, the plant’s own genes may be expressed more abundantly by inserting additional copies of them or by combining these genes with different promotors which drive gene expression more efficiently than the gene’s native promotor.

REFERENCES

Shewfelt, R. L. 1985. Postharvest treatment for extending the shelf life of fruits and vegetables. Food Technol., 40(5): 70–72,74,76–78, 80 and 89.

Shewfelt, R. L. 1999. Fruit and vegetable quality, in Fruit and Vegetable Quality:

An Integrated Approach, R. L. Shewfelt and B. Brückner, eds., Technomic

Publishing Co., Inc., Lancaster, PA.

Shewfelt, R. L., Erickson, M. E., Hung, Y-C. and Malundo, T. M. M. 1997. Applying quality concepts in frozen food development. Food Technol., 51(2):

56–59.

Simmonds, N. W. 1979. Principles of Crop Improvement, Longman, London.

Sloof, M., Tijskens, L. M. M. and Wilkinson, E. C. 1996. Concepts for modelling the quality of perishable products. Trends Food Science Tecnol., 7: 165–171.

Steenkamp, J. B. E. M. 1989. Product Quality: an Investigation into the Concept and How It Is Perceived by Consumers. Ph.D. thesis, Agricultural University

Wageningen, The Netherlands.

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Economic Impact of Aflatoxin Contamination in Groundnuts Production

Introduction

Aflatoxin is known in chemistry science as a mycotoxin that, thus a micro dangerous chemical substance produced as a secondary metabolites by Aspergillus Flavus and Aspergillus parasiticus fungi. These fungi are widely studied due to their effect on humans and animals, as well as the economic implications thereof (Galvez et al, 2003; Chinnan & Resurreccion, 2013; Kaaya, 2014).

Aflatoxin, like foot-and-mouth disease, hinders the export of African products and agricultural produce to lucrative European, US and rich Asian markets. Often the communities have little knowledge of the existence of such problems and their socio-economic impact. In general, the communities do not have solutions to the problems caused by these diseases, as they do not fully understand them.

Economic Impact of Aflatoxin Contamination in Groundnuts Production

Aflatoxin has been identified as the major problem in groundnuts trade for African countries who are losing about $760 million annually due to contamination of groundnuts (FAO, 1997; Kaaya, 2014).

Smallholder producers suffer the biggest losses both socially and economically, as they lose much of their produce to rotting and contamination caused by moulds and fungi. They are also prone to diseases caused by consuming higher level of aflatoxin.  About 40 percent of burden of diseases in Africa South of Sahara are related to consumption of high levels of Aflatoxin (Kaaya, 2014; Williams et al, 2004).

It is expensive to remove aflatoxin in contaminated groundnuts, raising processing costs. This promotes cost transfer behaviour amongst value chain actors. On the other hand, about 40 percent of disease burden in Africa is related to Aflatoxin contamination, affecting farm labour especially for smallholder farmers, reducing their time and cash investment in their farming businesses, and a threat to their health. Aflatoxin is linked to liver cancer, kwashiorkor, retarded growth in kids and animals, malaria and HIV. Due to pronounced health risks, many countries and trading blocs have imposed strict control measures on international groundnuts trading to safeguard their citizens and improve food safety. However, aflatoxin contamination can be reduced to acceptable levels through raising awareness amongst smallholder producers, investing in quality management as well as crafting and implementing favourable policies that encourage investment in aflatoxin mitigation.

Aflatoxin as a chemical substance is difficult to destroy without destroying the contaminated food. Once groundnuts are contaminated, it will be difficult to eliminate aflatoxin from them. Food processing usually requires low to medium temperatures of between 0 to 180° to cook or roast. Aflatoxin can only be eliminated at temperatures of over 480° (Kaaya, 2014).

Processing aflatoxin contaminated nuts into consumer ready products does not eliminate aflatoxin in groundnuts. If the groundnuts have high levels of contamination, then the end product will also contain higher levels of toxic substances. This in turn exposes the consumers of such products to higher levels of intoxication by aflatoxin and increases the risks of contracting aflatoxin related diseases.

The major economic effect of aflatoxin contamination in groundnuts to smallholder groundnuts farmers in developing countries, including Mozambique is poor marketability of their produce in international markets and poor prices in domestic markets that lead to lower net income to producers and other chain actors.

Taking the case of Zambia, groundnuts is considered one of the most important legumes cultivated on larger farm land area and as a replacement cash crop in place of tobacco that is now facing more stringent regulation in the international markets. Groundnuts are considered a very important source of protein for lower income families in both urban and rural areas, as well as smallholder producers (Times media group, September, 2014). However, higher levels of aflatoxin contamination hinder the exportation of surplus or tradable groundnuts to lucrative markets. Like in Mozambique, less than 5 percent of groundnuts produced are controlled for aflatoxin in the domestic markets, exposing domestic consumers to higher negative health risks (Times media group, 2014). Lack of control by the ineffective Bureau of standards in Zambia and Mozambique means that aflatoxin contaminated ready-to-eat products, floods the domestic markets in both countries. These products can be locally produced or imported.

Aflatoxin contamination lowers the net revenue of all market participants, in an effort to reduce contamination and improve quality of the groundnuts available for processing. This is caused by purchase price dynamics and sorting cost, as in most cases off grades are discarded. Poor post harvesting practices by smallholder producers increases the risk of purchasing sorted but aflatoxin contaminated nuts that will require further processing. The risk factor forces most traders to buy unsorted nuts at lower prices and do the sorting and grading. Higher costs often lead the traders to engage in cost shifting behaviour (Economic Research International, 2012).

Price shifting behaviour often affects two ends; the producer-end through lower prices for their produce and the consumer end through higher product prices due to higher production costs. However, in organic produce marketing linked to ‘fair trade’ markets (often), smallholder groundnuts farmers get higher prices and a premium for supplying quality graded produce that are traceable  back to the producer to certify for quality compliance. Consumers consider organically produce food to be safe and are often willing to pay a higher price for the right quality.

Recommendations

To improve competitiveness in African groundnuts value chains, a number of sticking issues affecting both domestic and international trades must be resolved. The most critical issues border on raising awareness of aflatoxin contamination on groundnuts and the socio-economic impact to smallholder producers.

Smallholder farmers’ awareness and understanding of aflatoxin issues and how they affect their livelihood is critical to aflatoxin mitigation. At present, only 5 percent of groundnuts smallholder producers are knowledgeable on the effect of aflatoxin to their health and rural economies. Health issues can be a driver of behaviour change amongst smallholder farmers, especially aflatoxin links to liver cancer and HIV, two well-known killers in rural Mozambique (SATH, 2014).

A three pronged approach to reduce the impact of aflatoxin contamination can help reduce the socio-economic impact on the whole chain actors. The approach may focus on raising awareness amongst smallholder groundnuts farmers and equipping them with post-harvest knowledge to reduce contamination and infection throughout drying, sorting, selecting, de-shelling and storage. Post-harvesting handling techniques must also be perfected by transporters, traders and processors of consumer ready goods.

Several measures can be applied to reduce contamination, including good agricultural practices, control of moisture and temperature in storage. Total Quality Management toolkit, also known as the ‘Blue Box’ has been successful used by Intertek on World Food Program consignments to keep aflatoxin contamination to desired levels (SATH, 2013; Intertek, 2012).

Quality control by traders and processors is critical in improving aflatoxin compliance in groundnuts. If all trades enforce quality guidance in their business processes including buying policies and practices. It is paramount to incentivize quality compliance when purchasing groundnuts from smallholder producers. This will complement the knowledge empowerment programs aimed at raising awareness of the existence of aflatoxin and its socio-economic impact to smallholder producers and all other actors in the groundnuts value chains.

Governments and regional regulatory institutions must critically look at policy measures that can be used to incentivize or encourage investment in aflatoxin mitigation, improvement of trading in aflatoxin compliant groundnuts, both internationally and intra-regionally. This might include harmonization of aflatoxin maximum acceptable levels applied in the region, as well as procedures for sampling and testing. Administrative documentation can also be simplified to improve free flow of groundnuts in the region.

Policies by individual countries might be used to incentivize private sector companies’ engagement in aflatoxin mitigation by investing in the whole groundnuts subsector to become aflatoxin compliant. This will speed up sector-wide compliance and improve competitiveness in both domestic and international markets. Holistic aflatoxin mitigation, though it will not completely eliminate contamination, will reduce the level of contamination of acceptable regulated levels that reduces health risks and increase Africa groundnuts acceptability in international markets. This will boost Mozambican and Zambian economies through increase forex inflows from exports.

Conclusion

Aflatoxin contamination is the major challenge on groundnuts trading by African countries that produce about 95 percent of the world groundnuts crop. In Southern Africa, in particular Mozambique and Zambia, there is poor awareness of aflatoxin contamination and its socio-economic effects to smallholder farmers. Contaminations that emanate from farm gate affect the whole supply chain. However, more contamination occurs on post-harvest handling and management of groundnuts at all levels of the supply chain. The more the produce exchanges hands and change storage conditions, the more the produce is exposed to contamination risks.

Contaminated nuts fetches less in local markets and are not accepted in the international markets due to strict control levels by the individual countries and trade blocs like the EU and South Africa. Reducing contamination and correct management of the crop at both farm levels will increase the value of the crop, acceptability and quality of final products produced from safer groundnuts. Farmers can do more by improving their farming practises and post-harvesting handling of their produce.

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BASIC SCIENCE OF PLANT DISEASES

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INTRODUCTION
A disease in plants can be defined as any disturbance brought about by an agency/factor which interferes with manufacture, translocation or utilization of food, mineral nutrients and water in such a way that the affected plant changes in appearance and or yields less than a normal, healthy plant of the same variety.
CAUSES OF PLANT DISEASES
Plant diseases are of two types viz., infectious and non-infectious. The infectious type are caused by fungi, bacteria and viruses. Nutritional deficiencies, mineral toxicities, lack or excess of soil moisture and light, low or too high temperatures, soil acidity or alkalinity constitute the non-infectious type.

Usually, a disease causes a progressive and continuous disturbance of cellular activities that eventually become manifest as symptoms. A symptom is a visible or otherwise detectable abnormality arising from disease. Disease symptoms should be closely observed, as they often give indications about the cause of the disease and thus have a diagnostic value. Environmental factors must always be taken into account. Symptoms may either be mild in terms of extension or intensity, or they may be acute or severe, the latter usually leading to the death of plants or plant parts. The spreading of a disease depends on two factors, i.e. time and environment. The time determines the course of the disease as the pathogen population increases with the passage of time. Environmental factors, such as climatic and soil conditions, and cultivation methods, have a great influence on the expression of the disease’s symptoms.
(1) NON-INFECTIOUS DISEASES
Many serious disorders are caused by external physical factors which adversely affect the proper growth of plants. Very often, the disorder is a direct result of a deficient or excessive supply of an essential growth factor, such as light, oxygen, soil moisture and heat. These are indispensable for the various life processes in plants including water and nutrient uptake, respiration and photosynthesis. A strong interaction exists between these growth factors. Generally, each plant has the capacity to balance its requirement for each of them. However, abrupt changes in environmental conditions or a severe deficiency or injurious overabundance of one or more of the growth factors may disrupt a plant’s life process and bring about disease symptoms. Since these disorders are not caused by parasites, they are not infectious.

Light: The requirement for light is very variable, some plant species prefer shade, others full sunlight. In many species the total hours of daylight – long day versus short day varieties determine the transgression from the vegetative to the generative phase. However, too much light, especially in combination with high temperature and lack of water, produces wilting or scalding in broad-leaved plants. Too little light produces chlorosis and etiolated or “lanky” growth.

Oxygen: An adequate supply of oxygen to above – ground parts of the plants is essential for effective respiration. A shortage of oxygen in the soil owing to poor soil structure, compaction or water-logging hampers the development of a healthy root system.

Water: Regular availability of water is essential for photosynthesis and metabolic processes in the plants. Plants absorb water mainly through the root hairs, this assists in the uptake of nutrients from the soil and their distribution throughout the plant. Evaporation of water from the leaves aids in cooling of leaf surfaces. Water contained within the walls of plant cells lends firmness (turgor) to plants, juicy fruits and succulent leaves may contain more than 90% water. A low relative humidity (dry air) may accelerate evaporation of water from the leaves and cause wilting when water pressure (turgor) cannot be maintained in the plant by replenishment from the roots. Early stages of wilting may be irreversible and the tissues may be damaged permanently.

Temperature: The supply of heat, or the lack of it, determines to a large extent the functioning of life processes in plants. Plants have an optimum temperature range for healthy development and a particular total requirement for heat in order to reach their full productivity.

Nutrients: Overabundance and deficiency of nutrients may cause a whole range of symptoms from discoloration to rot, die-back or stunted growth. Commonly, the productivity of a plant is lowered and its resistance to parasites weakened. The appearance of characteristic deficiency symptoms on leaves does not necessarily mean that the nutrient is in short supply in the soil. In fact, it might be sufficiently available, but its uptake may be impaired by an unfavourable acidity rate (pH) or by the shortage of another element. Soil salinity or alkalinity are serious problems threatening irrigated agriculture, where no possibilities exist to flush and drain the salt from the top layer of the soil. Continued fertilizing with ammonium sulphate may lead to high acidity of the soil and in time to toxic accumulation of elements such as iron, manganese and aluminium.

SYMPTOMS OF PLANT DISEASES
The way plant diseases express themselves by way of specific symptoms often holds important clues for diagnosis and treatment. The diagnosis must, however, take into account all environmental conditions, since these affect symptom expression. For instance, soil-borne diseases and nematodes may inhibit root development and thus cause poor growth. Likewise, a hard and compact soil structure near the surface may prevent the development of plant roots with a similar result. The following are the symptoms that generally occur with plant diseases:

Damping off– Sudden collapse and death of seedlings in the seed bed or field, e.g. damping off in tomato, cabbage and cotton.

Wilt– Sudden or gradual wilting and death of grown up plants as a result of disturbance in the vascular systems e.g. cotton wilt, green beans wilt, fusarium/bacterial wilt in peas.

Spot– Localised necrotic lesions on leaves/fruits consisting of dead or collapsed tissues, e.g. Brown spot of rice.

Blight– General and extremely rapid browning of leaves, branches, twigs and floral parts resulting in scorching and death of affected part.

Mildew– White, grey, brownish patches of varying size on leaves, stem and fruit usually covered with mycelium and fructification of the fungus e.g. Downy mildew of rose cut flowers and powdery mildew of cucurbits.

Canker– sunken out growths on leaves, stem, fruit which may be either smooth or rough e.g. citrus canker.

Scab– Roughed or crust like lesion giving a freckled appearance of the diseased organ e.g. potato scab.

Galls– Malformations of globose, elongated or irregular shape as a result fo excessive cell division and cell enlargement e.g. crown galls on rose cut flowers.

Mosaic– Alteration of light green, yellow, or white patches with the normal green of the leaves or fruits e.g. tomato mosaic.

Yellows– Uniform discolouration or chlorosis of the foliage without any sporting pattern.

Leaf curl– Distortion, thickening and curling of leaves e.g. tomato leaf curl.

Ring spot– Appearance of chlorotic or necrotic rings on the leaves and fruit e.g. tomato sported wilt virus.

Vein banding– Retention of bands of green tissue along the veins while the tissue between the veins is chlorotic e.g. vein banding mosaic.

Vein clearing– Destruction of chlorophyll adjacent or in the veinal tissue e.g. yellow vein mosaic

Witches broom– Profuse upward branching of twigs e.g. potato witches broom.

(2) INFECTIOUS DISEASES
1. PLANT PATHOGEN FUNGI
Fungi are nucleated, spore bearing, achlorophyllous organisms which generally reproduce sexually and whose usually filamentous, branched somatic structures are typically surrounded by cell walls containing cellulose or chitin or both. Fungi reproduce by means of spores which are specialised propagated or reproductive bodies which are formed asexually or sexually. Asexual reproduction is more important for the propagation of the species, as it results in production of numerous individuals and is usually repeated several times during the season. The spread of the disease mainly takes place with the help of asexually formed spores like zoospores, conidia and oidia. Sexual reproduction normally results in the production of resting spores like oospores, ascospores etc, which help the pathogen in tiding over unfavourable conditions. sexual stage of many fungi is produced once in a crop season. In general, it is the imperfect state that is the active pathogen, the perfect state (sexual) occurring in the terminal stages of the fungus spore and certain amount of growth which in turn depend moisture, temperature etc, which vary for different pathogens. Some fungi penetrate directly through cuticle and epidermis, others through stomata and wounds. The success of a fungus as a pathogen also depends on efficient transmission. Seed or other vegetative propagules, soil debris of a previous crop, weed hosts, alternate hosts are the major means of survival of the fungal pathogens. Dissemination (local and long distance) occurs through irrigation water, wind and insects. Effective means of control depends on the knowledge of the various means of survival and dissemination. Fungal pathogens are registered among many orders of fungi, their identification is done by using standard descriptions and keys.
2. PLANT PATHOGENIC BACTERIA
Bacteria are an extremely small, microscopic, unicellular micro-organisms that reproduce by fission. They exhibit three shapes viz, spherical or cocci, rods or bacilli and spiral or spirilli. The improant genera of bacteria that cause diseases in crop plants are:
Xanthomonas, Pseudomonas, Erwinia, Corynebacterium, Agrobacterium and Streptomyces). They enter the plants through wounds or natural openings (stomata) and interfere with physiological functions by destruction of structural integrity by acting upon cell wall components, interference with transport system by mechanical plugging or by producing toxins, interference with host metabolism or by alteration of genetic control mechanisms. These physiological disturbances at the cell level are expressed externally on plant by producing symptoms such as spots, blights, wilts, rots, cankers, galls etc. They are transmitted by a variety of agencies in or on seed and other planting material, soil, wind, rain, insects and nematodes and by cultural practices. The importance of these methods of transmission varies with the host and the pathogen and sometimes more than one method may be involved in any one disease. With regard to control, many seed borne bacterial pathogens can be eliminated either by heat/hot water treatment or by pre-treating the seed with suitable seed dressing chemicals.
3. PLANT PATHOGENIC VIRUSES
Viruses are subicroscopic organisms, multiply only inside living cells and have ability to cause disease. All viruses are parasitic in cells and cause a multitude of diseases to all forms of living organisms. Viruses are much smaller than fungi and bacteria and as such they cannot be visualised under microscope. Viruses can be observed under electronic microscope.
VIRUS TRANSMISSION
Viruses cannot actively penetrate their host cells. Some agency should directly introduce them into the host cell to cause infection. A virus is commonly transferred from an infected host to a non-infected one by a vector, which is often an insect, mite or nematode, but may also be fungus or parasitic flowering plant (e.g. Cuscuta spp, dodder). Sucking insects, such as aphids, leaf and plant hoppers, thrips and whitefly, dominate among the insect vectors, whereas nematodes and fungi play a role in the transmission of soil-borne virus disease. One particular vector may be able to transmit only one virus or many viruses. One particular virus may have one or more vectors. Some viruses may also be transmitted mechanically without the intervention of a vector insect. The sap of an infected plant can reach a healthy one either by means of tools used in cutting and grafting, by rubbing one plant against another.

SYMPTOMS OF VIRUS-INDUCED DISEASES
The symptoms of diseases caused by viruses are numerous and highly variable as their expression is influenced by the condition of the plant and environmental factors such as light, temperature and humidity. Visible symptoms may include local necrotic lesions, mosaic or mottled pattern of lighter and darker green leaf-tissues (chlorosis), yellowing or other discolouration including ring-spots or other distinct patterns, virescence (greening), vein clearing, reduction of plant growth leading to dwarding or stunting, distortion due to unequal growth of cells, excessive tillering, flower and fruit variegations, wilting eventually followed by defoliation and yield depression. A plant may be infected by several viruses at the same time, the symptoms of which may be manifested concurrently and thereby reinforce or mask one another. The study of symptoms may be used for diagnosing the virus disease, but one must take into account that similar symptoms may be caused by different viruses, or even by nutrient deficiencies and genetic disorders. The severity of the symptoms depends on the sensitivity of the plant and virulence of the virus.

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Lufenuron – A Miracle Pesticide

 

Lufenuron

Lufenuron

Lufenuron, a new pesticide on the market is a benzoylurea pesticide that inhibits the production of Chitin in insects. Without Chitin, a larval flea will never develop a hard outer shell (exoskeleton). With its inner organs exposed to air, the insect dies from dehydration soon after hatching or molting (shedding of its old, small shell).

Lufenuron is also used to fight fungal infections, since fungus cell walls are about one third Chitin.
Lufenuron is also sold as an agricultural pesticide against Lepidopteranseriophid mites, and western flower thrips. It is an effective anti fungal in plants.

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