Qualities of A Good Pesticide

It shouldnot be translocated in plant tissues i.e it shouldnot have a residual effect which affect human life e.g DDT

It should be ozone friendly i.e should not pollute the environment

It should be harmless to the crops being sprayed

It should not be poisonous to human and other animals

It should persist in the soil to avoid frequent applications

It should not be toxic to predators,parasites and pollinators like bees that are more useful to the crop

Advantages of Chemical Pest Control

  • It is a faster method of controlling crop pests in the garden
  • It is more effective than other methods of pest control
  • It does not reqire alo of labour compared to either mechanical or cultural
  • It only applies where mechanical and cultural methods are not possibly applicable e.g topography

Disadvantages of Chemical Pest Control

  • Pesticides can pollute the environment since some are non bio degradable
  • Pesticides may be toxic to plants if poorly applied
  • Chemicals may kill non targeted and useful organisms e.g pollinators,predators
  • some chemicals may leave their residues on the crop products which may affect the farmers
  • Some pests require reistance to some pesticides if they are persistently used
  • Some pesticides may be poisonous to man and must be handled properly
  • Technical knowledge is needed when applying the pesticides
  • Chemicals are expensive and may not be afforded by small scale farmers

Ways through Which Chemicals Affect The Pests

By direct contact;This is when the chemical enters through the skin or the cuticle of a pest and then kills it

Breathing System;This is when the chemical passes through the insect breathing pores and then affect it

Ingestion;This is when pests eat some of the toxic or poisonous chemicals and die by poisoning

Sucking;pesticides which pass through the plant stream may be sucked in by insects obtining their food in this way.such pesticides are called systemic chemicals that are used to kill piercing and sucking insects like aphids

Common insect pests and their effects on crop plants


Have biting and chewing mouth parts,Adults and nymphs defoliate the plants e.g yams,casava,cereals


Have biting and chewing mouth parts,eat up timber,cutdown growing plants e.g maize,citrusetc


Larva and adults bore,pupate in and feed on seed reducing grain quality e.g maize,beans,sorghum,peas etc

Maize stalk borer(lepidoptera)

Boring and chewing larva into stems,leaf sheaths and weaken the stems of maize,sugarcanes,rice etc

Army worms(lepidoptera)

Bting and chewing larva which attack and destroy large hectares with in a short period of time

Cotton stainers(hemiptera)

Have piercing and sucking mouth parts,destroy leaves and transmit viral diseases to cotton,tomatoes,maize and yams

White flies(hemiptera)

Have piercing and sucking mouth parts,distortion of leaves transmitting viral diseases to cocoa,citrus,rubber and tobacco

scale insects(hemiptera)

piercing and sucking mouth parts,feeding on cell content,folliage turns yellow and falling of young fruits


Have piercing and sucking mouth parts