Geocoris (Geocoridae family) are important predators found throughout the U.S. in agricultural crops. They are commonly known as ‘big-eyed bugs’ due to the characteristic large, prominent, and widely separated eyes on the sides of the head.
Geocoris actively hunt victims, and the big eyes provide a wide field of vision and boost the ability to locate prey.
The predator uses its long straw-like beak to stab and kill prey before sucking up the liquefied contents, leaving behind a hollow cadaver.
Geocoris deposit eggs singly and horizontally on leaf or stem surfaces. The hot-dog shaped eggs are distinguished from other insect eggs by the presence of two red eyespots near the tip.
Predatory stages include five nymphal instars and a winged adult. Nymphs appear similar to adults but have smaller and lack wings.
False chinch bugs, a closely related insect with decidedly plant-feeding tendencies, can be confused with Geocoris. False chinch bugs are more slender than big-eyed bugs and have less pronounced eyes.
In Arizona cotton, Geocoris feed on all stages of whitefly, lygus nymphs, thrips, lepidopteran eggs and small larvae, and mites, plus other beneficial species. Two Geocoris species are routinely found in our summer crops: G. pallens and G. punctipes.
These can be separated by color and size. G. pallens tends to be a slightly smaller and darker species. Both species feed similarly, but G. punctipes generally consumes more prey, and in most years is the more abundant species in cotton.
Research suggests they are important mid-to-late season predators with significant impact on whitefly and lygus populations. However, they are sensitive to many broad-spectrum insecticides.
Geocoris is a key natural enemy with a ‘work-horse’ reputation in cotton fields. Geocoris eggs and nymphs found in the field indicate a healthy, reproducing population with excellent potential for biological control.
The selective chemistries recommended in our cotton IPM guidelines conserve Geocoris and maintain the ‘free control’ offered by this important predator.
The ratio of Geocoris to whitefly large nymphs is a good indicator of the bio-control potential in a cotton system and can be used in whitefly management. This ratio is formed by the number of Geocoris (adults and nymphs) per 100 sweeps to whitefly large nymphs per leaf disc.
When at least 1.5 Geocoris to 1 whitefly large nymph are present in a field (1.5:1), a whitefly control spray may be deferred.
For the complete brochure including photos, go online to http://ag.arizona.edu/crops/cotton/files/GeocorisRatio.pdf.