Field Crops News

Larger Pirate Bug for Stored Grain Insect Control

Stored grain environments contain a complex of insect pest species. Biological control agents, including predators, parasitoids, and microbials can be used for insect control, but many natural enemies attack only one host species. A proposed solution to this problem is to release generalist predators which posses the ability to exploit a wide range of prey species.

The larger pirate bug, Lyctocoris campestris, is a generalist predator which was recently documented in stored corn in Wisconsin. Several aspects of this predator's development, reproduction, predation rate, and seasonal abundance have been researched, but only with corn as a grain habitat. Is this bug as effective in other stored grains, such as wheat or oats?

Researchers at the University of Minnesota examined the effectiveness of the larger pirate bug as a biological control agent against older Indianmeal moth (IMM) larvae in different stored commodities during 1995. They measured predation rate for each sex by placing a single predator in a pint-sized jar with approximately 300 grams of either shelled corn, hard red spring wheat, or rolled oats. Varying numbers of IMM larvae (2, 4, 8, 12, 16, 24, or 32) were placed in the jars 2 hours prior to the predator. The predator was allowed to disperse and feed for 24 hours, then the total number of prey killed or attacked was recorded.

Overall, female predators attacked more prey than males. And as expected, higher numbers of prey were attacked with increasing prey densities. In these experiments the bugs had a harder time either finding or attacking prey in oats than in corn or wheat.

Although it could be as effective in stored wheat as in stored corn environments, this bug is probably not a good option in oats. Unfortunately the larger pirate bug has several biological limitations to its use in stored grain compared to some other generalist predators. These include a lower reproductive potential and requirement for a moist environment for oviposition and egg survival.

More research needs to be conducted in large grain masses or empty commodity storages to determine the potential of this predator in commercial grain storages.

- Leslie Locke and Robert L. Meagher, University of Minnesota
(based on a poster presented at the 1996 North Central Branch Ent. Soc. Amer. meeting).

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