Seasonal Abundance of Red Spider Mite and Its Predators on Selected Cassava Accessions


Author(s): Emiliana N. Bernardo and Nelson M. Esguerra

Abstract

In an unsprayed cassava planting, the cassava red spider mite population fluctuated in lesser magnitude in moderately resistant Accessions 8, 12 and 46 than in Golden Yellow and susceptible Accessions 35, 36 and 38. Irrespective of the susceptibility level, population buildup of the spider mite in ViSCA occurred during low rainfall months which, during the two-year period covered, were from December 1978 to April 1979, August and September 1979 and in May, June and July 1980. In some instances, factors other than rainfall seemed to reduce mite population. Temperature and relative humidity did not show adverse effect on spider mite population. Predaceous insects such as coccinellid and staphylinid beetles, cecidomyiid fly and thrips (in decreasing order of abundance) and predaceous phytoseiid mites fluctuated in population density only slightly and showed minimum buildup despite the presence of high mite population. Factors other than predators could have helped also in reducing mite population in certain months. It is suggested that field planting should be planned such that the critical stage of growth of cassava which usually occurs during the third to the fifth month from planting will not coincide with the population peaks of the cassava red spider mite to avoid significant loss in tuber yield.

Keywords : Cassava. Cassava red spider mite. Population densities. Predators. Rainfall. Susceptible or resistant accession. Golden Yellow cassava. Time of planting.

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