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Agricultural Science Notes

Pests Of Crops

CONTENT

  • Meaning of crop pest
  • Types of crop pest
  • Classification of insect pest

MEANING OF CROP PEST

A crop pest can be defined as any organism capable of causing damage to the crop.

TYPES OF CROP PEST

Important crop pest are grouped in to the following classes;

  1. Insects
  2. Birds
  3. Rodents
  4. Monkeys
  5. Man
  6. Nematodes

CLASSIFICATION OF INSECT PEST

  1. Biting and chewing insects: they possess strong mandible and maxillae (mouth parts) which enable them to bite and chew plant parts e.g termites, grasshoppers, leafworm, mantids, locusts and beetles.
  2. Piercing and sucking insects: they possess stong mouthparts called proboscis which enable them to pierce through plants and suck liquid materials from them. Examples are aphids, cotton strainers, mealy bugs, scale insects, capsids, mirids and white flies.
  3. Burrowing insects: they and their larva stage are capable of burrowing the tissue of the plant parts or fruits or seeds. Examples are bean beetles, stem borers, maize weevils and rice weevils.

EVALUATION

  1. What are crop pests?
  2. List the three classes of insect pests.

IMPORTANT PESTS OF MAJOR CROPS
PestCrops AttackedNatures of Damages and Economic ImportancePrevention and Control Measures
Stem burrowerCereals e.g. rice, maize, guinea corn.Larvae bore holes into stemsThey eat up the tissuesThey weaken the plantUproot and burn infected plantSpray with insecticides e.g. Gammalin 20 Reduced growth and yieldEarly planting Crop rotation
Army WormCereals e.g. maizeLarvae invade and eat up leaves and stemReduce photosynthesisRetarded growthReduced yieldHand pickingSpray with insecticides. E.g. DDT  
Pod burrowerLegumes e.g. cowpea, soyabeansLarvae bore into the podThey eat up the seedsReduced yieldCrop rotationEarly harvesting  Spray with insecticidesIntroduce diseases.
AphidsLegumes e.g. cowpea, soyabeansStunted growthGalls on leavesVectors of disease e.g. rosette, mosaic disease of cowpeaSpray with insecticides to kill vectorUproot and burn infected plant  
Leaf beetleLegumes e.g. cowpea, soyabeansThey eat up the leavesReduce photosynthesisReduced yieldSpray with insecticidesUse pest-resistant varieties.
Cocoa mirids (capsids)Beverages e.g. CocoaThey inject toxic saliva into plantTransmits fungal diseasesReduced yieldStunted growthSpray with insecticides e.g. Gammalin 20Regular Weeding
Yam beetlesTubers e.g yamBoreholes into yam tubersReduced yieldReduction in quality and market valueDust yam setts with Adrin dust before plantingCrop rotation
Cassava MealybugsTubers e.g cassavaTwisting of stem and reduced internodesSwelling of shootsReduced yieldEarly planting Use pest-resistant varieties.Cutting treatmentSpray with insecticides
Green SpidermiteTubers e.g cassavaThey feed on the leavesReduce rate of photosynthesisReduced yieldUse biological controlSpray with insecticides
Variegated GrasshopperTubers e.g Cassava, yamAdults and larvae eat up the leaves and stemReduce the rate of photosynthesisReduced growthReduced yieldHand pickingSpray with insecticides e.g. Adrex 40
Cotton StainerCottonThey pierce and suck sap from plantsProduce toxic salivaTransmit diseasesReduce quality of boll Leaf distortionHand pickingSpray with insecticides
Cotton bollwormCottonLarvae feeds on the seeds of cottonCrop rotationDestroy the lint and reduce its qualityPremature fall of cotton bollSpray with insecticides to kill insectsBurn cotton plant debris after harvesting.
ThripsVegetables e.g. Onion, tomatoBrowning of leavesWilting of plantReduced yieldSpray with insecticides
Leaf rollersVegetableRolling and twisting of leaves Reduction in rate of photosynthesisReduced yieldSpray with insecticides e.g. Vetox 85
Leaf beetleVegetables e.g. pepper, okra and tomatoThey eat up leaves and stemsReduced photosynthesis Reduction in yield and qualitySpray with appropriate insecticides e.g. Vetox 85
Bean beetle, grain weevilsStored produce e.g. rice, cowpea and maize.Boreholes into grains and eat them upReduce the quality of stored produceReduced farmer’s incomeReduce the market value of grainsReduce viability of insfested grainsEarly harvestingProper storage of produceProper cleaning and fumigation of store with phostoxin tablets or with lindane dust.Store grains over fire placesProper drying of seeds to reduce moisture content and kill the eggs and larva of pests.
BirdsRice, maize, millets and sorghumFeed on grains in the fieldReduction in quality and yieldReduction in income of farmersUse of bird scarer or scare crowUse of cage traps with baitsShooting with catapultDrumming or noise making on the farmUse of explosive mechanism at regular intervalsUse of avicidesFencing /Screening farms in greenhouse
Rodents e.g. bush rabbit, rats and squirrelRice, yam, cassava and fruitsThey feed on cropsDestroy whole plantReduction in yieldIncrease in cost of productionTrapping with braits.Use of rodenticidesUse of string/wire trapsUse of predators e.g. dogs and catsClean weeding of farmsShooting and fencing Use of pit traps
MonkeysCocoa mango, banana, and orangeThey eat up the fruits Reduce the quality of fruitsLosses to the farmerUse trapsShooting with gun where possible.

EVALUATION

  1. List two ways of controlling cocoa mirids
  2. List two ways of controlling monkeys

ECONOMIC IMPORTANCE OF INSECT PESTS IN CROP PRODUCTION

  1. They destroy crops in the fields through their biting, chewing, boring, sucking and defoliation activities.
  2. They cause reduction in viability of stored produce
  3. Spot of injuries by insect pests predispose crops to pathogen attack
  4. They increase the cost of production as they are being controlled
  5. They render vegetables and fruits unattractive and unmarketable
  6. Some are of vectors of disease
  7. The profits of farmers are reduced
  8. They reduce the quality of produce either in the store or in the field
  9. They generally reduce the yield of crops
  10. They can also cause total death of crop plants.

GENERAL EVALUATION

  1. What are pathogens?
  2. List five pathogens you know
  3. List four economic importance of insect pest

READING ASSIGNMENT

Revision questions 3 and 8 Essential Agricultural Science for Senior Secondary Schools Chapter 26, page 247

WEEKEND ASSIGNMENT

SECTION A

  1. _____ is responsible for damages in crops. A. weeds B. water C. air D. pests
  2. The following are rodents except _____. ?A. rat B. grasscutter C.squirrel D.monkey
  3. The following are bitting and chewing insect except ____. A. termites B. capsids C.locust  D. beetles
  4. Stem burrowers will attack A. cereals B. legumes C. tubers D. spices
  5. Cotton strainers and meleabugs are examples of _____ insects. A. biting B. chewing C. piercing D. burrowing

SECTION B

  1. A. What are pests

B. List the five types of pests

2.   A. List five effects of pests in crop production

B. List three control measures of plant disease

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