Graus de resistência de trinta e cinco cultivares de mandioca (Manihot esculenta Crantz) a insetos e ao ácaro, Mononychellus tanajoa (Bondar, 1938) em Pacajus, Ceará, Brasil

Abstract

This work was carried out with the objectives of: 1) identifying both the insects and mites existing in the cassava crop ; 2) determinating their incidence period; 3) verifying the degree of resistance of 35 cultivars of cassava to both insects and the mite Mononychellus tanajoa. This work was carried out under field conditions at the "Unidade de Pesquisa do Litoral" in Pacajus-Cearã-Brazil, - from February 1986 to February 1987. Samples were taken every fifteen days throughought the crop growing period (12 months) in order to determine the population leveis of both insects and mites . The randomized blocks design arranged in a subdivided plot scheme with three replications in which the plots were made up by the cultivars and the subplots by the sampling periods was utilized . Aleurothixus aepim, Phenácoccus sp., Vatiga illudens, Erinnyis ello ello, latrophobia brasiliensis and M. tanajoa were the most frequently observed insects. Ali the insects but Erinnyis ello ello had their population peacs in periods of high temperature and low rainfali. The cassava cultivars which showed some degree of resis tance to M. tanajoa were those from the "Centro Nacional de Pes quisa de Mandioca e Fruticultura/EMBRAPA", Bahia, where such a fact had already been observed. The natural anemies acting to control the cassava phytophagous insects in the field were: Trichogramma sp., Telenomus sp., Belvosia sp. Euphorocera sp., Cryptophion sp., Ocyptamus sp., Coptocycla undecimpunctata (F. , 17 81), Metriona sexpunctata (F., 17 81), Chrysopa sp., Polybia sp., Acrosternum sp., Zelurus sp., and Ammophila sp.