Laboratory studies on the role of an egg predator,Blattisocius tarsalis(Berlese) (Acari: Ascidae), in relation to the natural control ofEphestia Cautella(Walker) (Lepidoptera: Pyralidae) in Warehouses

Abstract

AbstractEffective control ofEphestia cautella(Wlk.) byBlattisocius tarsalis(Berl.) has occasionally been observed in warehouses. It has been postulated that this control is negated by fumigation under sheets, because of differential effects on the moth and its predator, and removal of alternative prey. The biology ofB. tarsaliswas studied at 27°C and 73% RH. On eggs ofE. cautella, development took 5·9 days and there was 7% mortality; on eggs ofTribolium oastaneum(Hbst.), development took 7·4 days and there was 48% mortality. When offered a choice of eggs of the two pest species, the mites very rarely preyed on those ofT. castaneum. The number ofE. cautellaeggs consumed (after correction for partial consumption) was 3·8 (total) by nymphs, 2·4/day by ovipositing females, 1·5/day by non-ovipositing females, and 0·8/day by males. The sex ratio (female: male) was 2·5:1. Adult life-span averaged about 55 days (maximum 153 days), and the oviposition period lasted about 20 days. Females laid up to 5 eggs/day at peak oviposition. The potential rate of increase ofB. tarsalisonE. cautellaeggs was very high, far exceeding that of its prey. These data confirm previous postulates concerning the role ofB. tarsalisin natural control ofE. cautella, and support the hypothesis that fumigation reduces predator-effectiveness. Modification of control regimes might allow greater natural control by the mite and reduce the increasing pest status of the moth.