Wednesday, November 10, 2010

POST- HARVEST COCOA PEST- THEIR BIOLOGY, DAMAGES AND CONTROL

By
DENNIS OWUSU BOATENG

+233(0)240-296835
polonium90@yahoo.com

Introduction
• Post-harvest cocoa is mostly affected be a lot of constrains. Some of these constrains are caused by insect pest and other rodents. Others are chemical, physical and microbial damages. Pest in general can be defined as an organism that causes a problem in agriculture.
• It can also be said that pest is an organism that reduces the availability, quality, or value of some human resource. This resource may be a plant or animal used for food, fiber, or recreational purposes. Pest can be either regarded as agricultural, medical or Aesthetic.
How an Insect Becomes a Pest
• An insect becomes a pest first, by changing or manipulating their environment together with a change in their biology. One way of changing their environment is by the introduction of new agricultural farming methods. This may change their feeding habit and ecological interactions.
Post-Harvest Cocoa Pest
• The majority of stored pest insects that attack most stored cocoa beans and products come from only two of the roughly 26 orders of the class Insecta;

1. Coleoptera and 2. Lepidoptera.
The order Rodentia is also considered pest of post - harvest cocoa.
• On the other hand, predator and parasitoid of stored insect pest comes from the order Hemiptera, Hymenoptera, and Diptera. Some well known Post-harvest pest of cocoa are listed below.
1. Tropical warehouse moth-Ephestia cautella
2. Cigarette beetle-Lasioderma serricone
3. Corn sap beetle-Carpophilus dimidiatus
4. Rusty grain beetle-Cryptolestes ferrugineus
5. Coffee bean weevil-Araeocerus fasciculatus
6. Red flour beetles-Tribolium castaneum
7. Rodent-Rattus spp.

Tropical warehouse moth-Ephestia cautella
• Biology
Eggs are laid over or near the products. Larvae are mobile over products, where they feed and produced silk which may form large webs. When fully grown, they leave the products and move towards the package openings. Pupae may be immediately formed, becoming adult moths. Adults are short lived and do not feed. They are active at night. They live for 13 to 14 days and a female may lay 279 eggs. Life cycle takes 50 - 90 days under optimum temperature Conditions.
• Alternative Host
Nuts, tobacco, almonds and dried fruit (it is a major pest and also damages flours, milled cereal products.

• Damages
1. Presence of 'worms' in the chocolate.
2. The moths in the grain result in reduced grain weight and dockage because of contamination by fecal material and webbing.
3.
• Control
1. Pheromone traps are commercially available for inspection, monitoring, and pinpointing infestations of adult moths
2. Fumigation but this can be done only on emergency.

Cigarette beetle-Lasioderma serricone
• Biology
The female beetle lays around 100 eggs loosely on the commodity. The hatching larvae are the "grow bag" stage of the insect are active and will move around on and bore into the product, feeding as they go. The complete life cycle takes 26 days at 37 °C and 120 days at 20 °C. L. serricorne cannot tolerate the cold; adults die within 6 days at 4 °C, and eggs survive 5 days at 0–5 °C.
• Alternative Host
Sweet potato, cassava, tobacco, maize, pulses, spices, fruit, processed flour and some animal products
• Damages
Larval feeding causes direct damage to foodstuffs and non-food items. These products are contaminated by the presence of beetles, larvae, pupae, cocoons, frass (fecal material), and insect parts. Beetles chewing through cardboard boxes and containers, and packaging cause indirect damage. Cocoons are often attached to a solid substrate and in severe infestations form large clusters. Larvae will sometimes bore their way through cardboard boxes and other packaging in search of a place to pupate.
• Control
1. Use of Pheromones
2. Use of Fungicides such as methyl bromide and phosphine
3. Use of Insecticides such as Cypermethrin

Corn sap beetle-Carpophilus dimidiatus
• Biology
Adults lay eggs in rotting or damaged fruit on the orchard floor. Mature larvae emerge from the fruit and pupate in the ground. Adults emerge from the pupae and attack fruit in late spring and summer. If no hosts are available they overwinter in cracks in the tree, under bark or in mummified fruit. It takes about a month in summer to develop from egg to adult. Summer rainfall and rotting of fruit provides the best conditions for beetle breeding. Dry summer and autumn reduces breeding condition.
• Alternative Host
Stone fruit, persimmons, fallen citrus, apples, and figs.
• Damages
They penetrate the ripening fruit and can mechanically transmit spores of the brown rot fungus. The disease is carried on the body of the insect; the fruit can become diseases without the beetle sucking on it. They enter through splits.
• Control
Sweeping fruit from under the drip line and mulching it is an option will break it’s life cycle. Growers should inspect fallen fruit to assess beetle activity and the potential for damage. Spray with insecticide such as carbaryl. Good hygiene is the only effective control of this pest.

Rusty grain beetle-Cryptolestes ferrugineus
• Biology
Each female is capable of laying 200 to 500 eggs, which are deposited loosely on or among the grain kernels and hatch in 3 to 5 days in a temperature of 30 degrees. In feeding they penetrate the germ-end where they pupate. Under conditions of 15% grain moisture content and temperature of 32 degrees, the transition from egg to adult beetle takes about 4 weeks. The beetle will not develop in dry grain with a moisture content of less than 12% or when the relative humidity is less than 40%. Temperature limits for complete development are 20 to 40 degrees.
• Alternative Host
1. Wheat
2. Grain

• Damages
Grain damage is caused by both the larvae and the adults of this species when they attack the kernels. The larvae and adults feed on the germ and endosperm. Heavy infestations of the insects also contribute to other damage by causing the grain to heat and spoil, and by spreading fungal spores in the stored grain.
• Control
To prevent an infestation, thoroughly clean empty bins before loading new grain into them. To prevent re-infestation since the insect can fly on warm days, old residual grain should be destroyed by burning or by disposal in a sanitary fill. Drying and cooling grain shortly after harvesting is a valuable precaution. Infestations in bins can be controlled by treating the grain with a recommended fumigant or, in winter, by cooling the grain to - 7 degrees and holding it at this temperature for at least 6 weeks.

Coffee bean weevil-Araeocerus fasciculatus
• Biology
The female lays about 50 eggs and the larvae burrow into seed upon hatching. The life cycle is completed in 30 to 70 days but may take longer in cooler areas of the world, and 8 to 10 generations per year can occur. The coffee bean weevil also lays its eggs in the soft kernels of corn in the field and then breeds in it after harvest.

• Alternative Host
Sweet potato, coffee, nutmeg, maize, yam, cassava, legumes, groundnuts, nuts
• Damages
It causes little damage to stored corn as the kernels become too hard. The coffee bean weevils are a strong flier. Infestation often first becomes noticeable when adult weevils appear in windows. The coffee bean weevil can be a serious pest in the tropical and subtropical areas of the world where these crops are grown.
• Control
Wrap infested product in another plastic bag before throwing it outside in a trans-container. When large numbers of bean weevils are flying about after emerging from infested material, a space treatment may be needed. Removing these beetles from shelves, counters and window sills with a vacuum device, however may be an easier solution to adult beetles in many situations.

Red flour beetles-Tribolium castaneum
• Biology
Female beetles each lay 300 to 400 eggs in flour or other foods during a period of five to eight months. Within 5 to 12 days, these eggs hatch into cylindrical, white larvae tinged with yellow. The length of the larval period varies from 22 to more than 100 days; the pupal period is about 8 days. Fully grown larvae transform to naked pupae, and in a week adults emerge. The life cycle requires 7 to 12 weeks, with adults living for 3 years or more. Ideally this type of beetle prefers temperatures of ca. 30°C and will not develop or breed at temperatures lower than 18°C.
• Alternative Host
Sweet potato, cassava, maize, wheat, sorghum, groundnuts, nuts, spices, coffee, processed cereal flours, dried fruit
• Damages
Give the product a foul smell which may also cause market losses to the stored product.
• Control
Dispose of heavily infested foods in wrapped, heavy plastic bags or in sealed containers and leave for garbage disposal service. If you detect these beetles early, disposal alone may solve the problem. Careful sanitation is the best method to avoid any stored-product pests. In the case of industrial problems e.g. food factories, grain silos, bulk flour stores etc., as well as carrying out the procedures above, which should be an on-going task anyway, fumigation may have to be considered.

Rodent-Rattus spp
• Biology
The lady rat is only pregnant for 3 weeks (Gestation period). The litter size can vary from 7 to 8.This lady can have between 3 to 6 litters per year, depending upon food availability and harborages. After a period of 10 to 12 weeks, the babies aren't anymore, and so they breed on. Thank God the natural mortality rate is about 90%. They also leave about 40 droppings/day. A squirrels nest is called a drey and is made up of a ball of twigs, leaves attached, and lined with grass, moss and fur
• Alternative Host
Buds, shoots, ripe and unripe fruits, nuts, bulbs, seeds, (peas, beans, maize, wheat), eggs and young of both songbirds and game birds.
• Damages
Bark damage is greatest during the months of May to July. They also chew the seed making it loss it’s market value .Defecation can give foul smell to cocoa in storage.
• Control
1. Use of cage traps
2. Use of spring traps.
3. Poison bait.
4. Shooting/Drey poking
• NOTE
– Drey poking is removal of the nests with long poles.

References
• Lyon, William F.. "Confused and Red Flour Beetles". Ohio State University Extension Fact Sheet. The Ohio State University. http://ohioline.osu.edu/hyg-fact/2000/2087.html. Retrieved 2008-03-05.
• "Team Contributes to Red Flour Beetle Genome Sequencing". Newswise (Kansas State University). 2008-03-23. http://www.newswise.com/articles/view/538914/?sc=rssn. Retrieved 2008-03-23.
• Baur FJ. 1991. Chemical methods to control insect pests of processed foods. pp. 427-440. In J. R. Gorham (ed.), Ecology and Management of Food-Industry Pests. FDA Technical Bulletin 4.
• Pedigo, Larry P. 1989. Entomology and Pest Management. New York: Macmillan Publishing Company.
• USDA Office of Pest Management Policy & Pesticide Impact Assessment Program: (crop profiles).
• Olkowski, W.; Daar, S.; Olkowski, H. (1995): The gardener’s guide to common-sense pest control. The Taunton Press. USA.

2 comments:

  1. A fine piece of academic study. very informative
    as we now have (in Bali Indonesia) a seeming outbreak of cocoa pests! Thank you.

    ReplyDelete
  2. Thank u very much Opah Ibrahim for recommending me.

    ReplyDelete