Field Crops News

Predatory Bugs Prefer Different Crops

Understanding how predators interact with crop monocultures, and the degree of crop specificity they exhibit may allow us to predict the response of predators to different cropping systems, help us understand the constraints on predators in different crops, and provide insights into methods for enhancing the level of predation on pest insects.

The abundance of predatory Hemiptera within 4 crops (soybean, corn, tomato and tobacco) was studied in replicated small plots during 1992-1993 in Kentucky. Despite the close proximity of the plots, abundance of bugs varied among the crops. Three damsel bugs -- Nabis roseipennis, N. americoferus, and N. rufusculus -- were found primarily in soybeans; only small numbers were found in the other three crops. The bigeyed bug, Geocoris punctipes, was common on both soybean and tobacco, although immature stages were more abundant on soybeans, suggesting that greater reproduction occurred in this crop. Both Nabis and Geocoris are common predators of lepidopteran eggs and small larvae.

The minute pirate bug, Orius insidious, was abundant on soybeans early in the season-when thrips are abundant in that crop. By mid-July Orius numbers were declining in soybeans and increasing in corn. In previous studies, high Orius populations in a variety of crops have often been associated with abundant thrips or flowering of the crop. A stilt bug, Jalysus wickhami, was found on tomatoes and tobacco and only rarely on the other crops.

It is interesting that even in small plots adjacent to each other, predatory Hemiptera showed distinct preferences for different crops, suggesting differing requirements among these species. These predators are often referred to as generalists, but this study suggests that may be an inappropriate term for these predators, at least in terms of their habitat preferences.

Source:

Pfannenstiel, R. S. and K. V. Yeargan. 1998. Associations of predaceous Hemiptera with selected crops. Environ. Entomol. 27: 232-239.


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