Geocoris pallens Found to be Predaceous on Microlarinus spp. Introduced to California for the Biological Control of Puncture Vine, Tribulus terrestris123

Abstract

The lygaeid bug Geocoris pallens Stål was identified as an egg predator of the weevils Microlarinus lareynii (Jacquelin duVal and M. typriformis (Wollaston), introduced to California in 1961 for the biological control of puncture vine,Tribulus terrestris L. Though generally considered a beneficial species, G. pallens has assumed unique injurious status by adopting these useful, weed-feeding insects as hosts. Insectary exclusion cagings plus field and laboratory observations positively identified G. pallens as attacking Microlarinus spp. eggs. Substantial G. pallensincited egg mortality was detected throughout the range of weed and weevils in southern California. The nature of natural enemies found attacking phytophagous insects introduced to various countries for biological weed control is reviewed.