BP Singh

172 Shashi Bhallathese symptoms of insect damage to collect healthy ger:rJ.1.plasmmaterial. As pest risk is involved in the import of both vegetativelypropagated material and ~~eds, the symptoms of insect damage arevery important for the quarantine worker to detect infestation inthe germplasm under exchange to prevent the introduction offoreign pests into the country. The damage due to insect pests maybe direct or indirect. .Direct damage is caused by biting and chewing off the plant parts,piercing of plant tissues and sucking of plant juices. Much of thedamage from seed infesting insects is done directly to the kernels.Grain is reduced in weight due to consumption by adults andimmature stages.Indirect damage is due to the secondary invasion of host plantsthrough the wounds caused by feeding ~nd other activities of theinsect. Piercing and sucking of the plant juices results in fungusand virus develop,ment followed by plant decay, wilting, systemicyellowing, blotching or mosaicing etc. Insects and mites serve asvectors of a number of virus diseases. In storage, they produc~heat and change the humidity. Germination is impaired bydamage either to germ or endosperm.On the ~asis of insect feeding and its effect on external andinternal plant tissues or parts, these have been categorized asExternal feeders and Internal feeders.'External feeders: Either they feed on the plant tissues from outsideand produce eaten out areas of different extents or they roll or webtogether the plant parts as leaves, flowers and flower buds theyinfest and feed within.Internal feeders: They cause damage by remaining within theplant tissues during a part or all of their destructive stages. Thisis accomplished by adult thrusting their eggs into the tissues eitherby ovipositor or the larvae gain entry by eating/boring their wayin. These include leaf-miners/.borers (stem-borers, fruit-borer), gallmakers, gallery makers, and seed feeders.On the basis of the feeding habits of the insects, they can becategorized as biting and chewing type which bite and chew offthe plant parts and sap feeders (piercing and sucking type) whichpierce the plant tissue and suck the sap.