BP Singh

176 Sltashi Bhallacoffee stem borer, Xylotrechus quadripes, bore into the main stem,make tunnels into the lower part of stem and into the main root.The tunnels made in the bark appear as ridges and plants may wilt.m. case of shot hole borer of coffee, Xylosandrus compactus, infestedbranches gradually wilt and turn yellow and fall off. The grubs ofcotton stem weevil, Pemphesulus offinis Fst., tunnel round the stemfeeding on the soft tissues and result in the formation of gall likeswelling at the'site of injury. In pink boll worm affected crops,flowers fail to open, squares fall and bolls are eaten out. The mangostem borer, Batocera rufomaculata grubs feed by tunnelling throughthe bark of branches and cause wilting. There are abol,lt 20 borers(caterpillars) that attack sugarcane in India. A few beetles havealso been found boring into growing canes and decaying stems.In some cases one larva bores inside the plant and kills thegrowing point resulting in dead heart and then moves to adjacentshoots causing several dead hearts in a clump.Gall makersThere are ~ertain insects which in their immature or adultstage live in the plant tissues and their activities lead to the plantdeformities. These may be r.2!:!!!£l, ~..heJ:,ical, and e.!mJ.g~.ted· ors..l?in~uitr,"!ls~~res and are ~own as gall~", which are :R-est spes;ific.These galls provide shelt~r and food to the insects. The gallforming insects include many '!:.l2!:!ids, ~les, lJlic;!g"es, ~igslt@lps, ~ps and some w.,g!'l:~d1s. Due to the formation of galls thegrowth of the' plant may be impaired and setting of fruits, grainsand seeds may be adversely affected. The galls may be simple a:scurling of leaves or simple enlargements of affected portions or ofcomplex structures as some galls produced by rollid _Q-ggs.Mostly some species belonging to families Cecidomyiidae,Cynipidae, Aphididae, Psyllidae and Aleyrodidae and orderThrysanoptera (Thrips) cause galls on the differen~ parts of theplant. The rice gall midge causes damage by producing tubulargalls popularly: known as Silver shoots which are the leaf sheathsand tillers produced into galls. 1;'hese do not bear any panicles.Early infestation results in P!ofuse tillering of plants and new tillersget infested. Infestation at later ,stage results in branching athigher nodes, just below the silver shoots. On bitter gourd, stemgalls are formed by Lasioptera falcata. Flower galls are producedby midges, Contarinia sorghicola on sorghum and,by'blossom midgeon mango.