the Symposium on Wheats for More Tropical Environments - cimmyt

152Insect Pests and Diseasesof Wheat in <strong>the</strong> PhilippinesD.B. Lapis, Institute for Plant Breeding, University of <strong>the</strong>Philippines, Los Baiios, PhilippinesAbstractFor <strong>the</strong> Philippines, producing wheat would be an ideal approachfor reducingwheat importation andfor savingforeign exchange. Insect pests and diseasesare two of <strong>the</strong> constraints to its production and to crop acceptability by <strong>the</strong>farmer. Based on observations in areas where wheat is being targetedforcommercial production, helminthosporium seems to be <strong>the</strong> most limitingfactorto producing wheat with desirable yield on a commercial scale;foot rots areobserved only occasionally and sporadically. Work on wheat pests has onlybegun in <strong>the</strong> Philippines; principal research efforts will be in breedingforresistant cultivars to control <strong>the</strong> pests and diseases ofprimary economicimportance.Although wheat was under cultivationin <strong>the</strong> Philippines as early as 1664,commercial production is still in itsinfancy. with only about 69 hectares ofcommercial production in <strong>the</strong> 1983cropping season. However, a great dealof wheat is consumed in <strong>the</strong>Philippines. In 1983, wheat importationamounted to about US$ 20 million.second only to petroleum. and thusconstituted a tremendous foreignexchange drain.Even though producing wheat would bean ideal approach for reducing wheatimportation and saving foreignexchange, <strong>the</strong>re are at presentconstraints which make wheat growingeconomically unfeasible. The crop does,however. offer promise for futureproduction. Insect pests and diseasesare two of <strong>the</strong> production constraintswhich limit its acceptance by <strong>the</strong>farmer.Wheat DiseasesThe two diseases of major importancein <strong>the</strong> Philippines are helminthosporiumleaf spot and foot rots. Leafspot is caused by Helminthosporiumsativum, and <strong>the</strong>re are several o<strong>the</strong>rreported helminthosporium species.Foot rots are caused by Sclerotiumrolfstt, Rhizoctonia solani, Fusariumroseum, Phythium spp., Phytophthoraspp. and H. sativum.Several species of Helminthosporiumare suspected of causing leaf spot, leafstripe and net blotch. which arepresently attacking wheat. It is obviousthat <strong>the</strong>y are caused by differentspecies, because of <strong>the</strong> observeddifferences in <strong>the</strong> characteristics of <strong>the</strong>lesions present on <strong>the</strong> diseased plants.The different root rot pathogens infectplants, ei<strong>the</strong>r alone or in combination.Based on observations made at <strong>the</strong>different areas where wheat is beingtargeted for commercial production. <strong>the</strong>disease caused by <strong>the</strong> Helminthosporiumspp. is believed to be <strong>the</strong> mostlimiting factor in <strong>the</strong> effort to producewheat with desirable yield on acommercial scale. Wheat in those areasis planted in November and December.so that <strong>the</strong> early vegetative stagecoincides with <strong>the</strong> cooler months(December and January). Previousobservations in <strong>the</strong> field have shownthat leaf spot is always present onwheat. but usually <strong>the</strong> disease becomessevere only at <strong>the</strong> later growth stages,between late January and late