CONTROL OF TYROGLYPHOID MITES IN STORED GRAIN BY THE PREDATORY MITE CHEYLETUS ERUDITUS (SCHRANK)

Abstract

The authors deal with the problem of mite infestation of stored grain in Czechoslovakia, where more than 10% of the grain is infested by Acarus siro L. and Glycyphagus destructor (Schr.). The methods of mite control hitherto used (fumigants CH3Br, HCN, and ALP) were poor and of short duration. Accordingly, the authors investigated the possibility of biological control using the predacious mite Cheyletus eruditus (Schr.). Some observations showed spontaneous biological control, culminating in the complete eradication of the grain mites. The investigation covered eight grain storages. Details are given of the characteristic course of observations in one grain store, and the results of seven other stores are summarized. In three other stores was studied the influence of cleanliness and moisture contents of grain on the development of mites. The authors found that the mites multiplied on uncleaned wheat (16% moisture content), on cleaned wheat (16% moisture content), and on dry, uncleaned wheat (14% moisture content) in the ratio of 100:10:1.Further details are given about two semioperational trials following the introduction of the predacious mite Cheyletus eruditus (Schr.). These trials were generally successful with the complete eradication of harmful mites.The authors report successful results on the introduction of the predacious mite into uninfested grain destined for long-term storage. They discuss 28 experiments with its artificial introduction (25 successful in biological control) and the course of an operational trial which showed good results as well. Experiences and results from semioperational and operational trials form the basis of a set of technological principles as a guide to practice. It is recommended that the predacious mite be collected from natural biotopes where complete eradication of harmful mites has already been completed. For successful results, the authors recommend artificial introduction in spring or autumn (temperature 5–10 °C) on the surface of grain in the proportion 1:100 to 1:1000 (Cheyletus eruditus Schr.: Acarus siro L. + Glycyphagus destructor Schr.).