 |
||||
 |
Back to Predators Table of Contents
Geocoris spp. by James Hagler, USDA-ARS, Arid-Land Agricultural Research Center (ALARC), 21881 N. Cardon Lane, Maricopa, AZ 85138 and Nicole Sanchez, Area Specialized Agent, Commercial Horticulture, NCSU-CES, 110 S. Market St, Trenton, NC 28585. Bigeyed bugs, Geocoris spp., are among the most abundant and important predaceous insects in many cropping systems in the U.S. They are also found in lawns and ornamental plantings. There are approximately 19 species that inhabit North America. Of these, G. punctipes and G. pallens are the most common. Geocoris spp. are known to feed on plants; however they rarely cause economic damage.
The most common species found in North America are:
Adults and nymphs have oval bodies and broad heads. Their most distinguishing characteristic is their large, bulging eyes. They have relatively short antennae that are slightly enlarged at the tip. Bigeyed bugs walk with a distinctive "waggle" and omit a fowl odor when handled. Adults are about 3/16th inch long and silver/gray in appearance (G. punctipes). The immatures look similar to small adults, but lighter and without fully developed wings. "Hot dog"-shaped eggs are laid singly on leaves (typically on undersides) and stems of many crops. They are white to tan with a distinctive red spot. Both the adults and immatures feed by sucking juices from their prey through a needle-like beak. The beak is folded under the insect’s body when it is not feeding. Beware: chinch bugs, a pest of turfgrass, resemble bigeyed bugs and managers sometimes mistakenly spray when the biological control agent is found.
Habitat Geocoris spp. are commonly found throughout the southern regions of the U.S. in most cropping systems. G. punctipes and G. pallens are the most common species along the cotton belt. G. uliginosis is frequently found in lawns. G. punctipes is also found in ornamental plantings and vegetables. Look among leaf litter at the base of plants to detect bigeyed bugs. G. punctipes is frequently found in strawberries and vegetables grown in plasticulture in GA and NC.
Bigeyed bugs feed on a wide variety of prey smaller than themselves. They are among the most important natural enemies in cotton. They feed on eggs and small larvae of most lepidopteran pests (bollworm, pink bollworm, tobacco budworm), on the eggs and nymphs of plant bugs (e.g., lygus), and on all life stages of whiteflies, mites and aphids. There are 67 species included in a list of prey organisms fed on by bigeyed bugs (Crocker and Whitcomb 1980). Cohen and Byrne (1992) observed that Geocoris use salivary secretions to adhere whitefly wings to a stable surface to allow feeding.
Life Cycle Bigeyed bugs overwinter as adults. As with any insects, life cycle is dependent on temperature. Eggs that are laid singly on leaves or stems hatch in approximately one week. Bigeyed bugs have five nymphal instars, each of which lasts from 4 to 6 days. Both nymphs and adults are predaceous. Adults live approximately one month and a female can lay up to 300 eggs during her adult life span. Several generations may occur during a crop growing season.
Relative Effectiveness The potential for Geocoris spp. as biological controls is well founded. Adults and immatures can consume dozens of prey per day (Hagler and Cohen 1991). However, due to the small size and cryptic nature of this beneficial, quantification of predation in the field is difficult (Hagler and Naranjo 1994). Cover crops such as crimson clover and vetch may enhance populations of bigeyed bug and improve predation against pests in some crops (Bugg et al. 1991). Other studies have demonstrated the potential for effectiveness against various pests in greenhouse crops (Tamaki and Weeks 1972, Pendleton 2002).
Conservation Geocoris spp. are ideal candidates for conservation. Since bigeyed bugs are also seed feeders, refuge crops can be planted that harbor large populations of Geocoris. For example, Tamaki and Weeks (1972) investigated the possibility of increasing bigeyed bug populations in crop lands by planting sunflowers. Their results were very encouraging. It is suggested that the ability to obtain some nutrition from plants further increases bigeyed bug potential as a useful biological control agent because it provides feeding flexibility during times of low pest populations, allowing populations to remain stable and ready to address further pest outbreaks (Eubanks and Denno 1999, Naranjo and Stimac 1985). Exploiting the potential of Geocoris spp. as a native biological control agent deserves further study. Polycropping, use of pest-specific insecticides (e.g., microbials, insect growth regulators, Bt cotton, etc.), and use of economic thresholds to minimize pesticide applications are all practical recommendations for preserving Geocoris (and other natural enemies) populations.
As with most beneficial insects, Geocoris spp. are very susceptible to broad spectrum pesticides. Conservation of bigeyed bugs and the use of broad spectrum pesticides are not compatible. Because bigeyed bugs are known to feed on plants, systemic pesticides may have negative effects on Geocoris populations. Boyd and Boethel (1998) showed that leaf residues of foliar applications of some insecticides were lethal to bigeyed bugs. Among a variety of cotton insecticides, Elzen, Elzen and King (1998) found that cyfluthrin, profenofos, endosulfan, oxamyl and spinosad were most favorable to conservation of bigeyed bugs, while malathion, chlorfenapyr and fipronil caused the most Geocoris mortality. Similar results were found in another study of insecticide residues in soybean (Boyd and Boethel 1998).
Commercial Availability It has been demonstrated that repeated generations of bigeyed bugs can be reared on an artifical diet, and that commercially-reared bigeyed bugs had similar effectiveness as predators to their wild counterparts (Hagler and Cohen 1991, Cohen 2000, Pendleton 2002), suggesting that they have great potential as biological control agents. An artificial, meat-based diet for rearing Geocoris was first developed by Allen Cohen (Cohen 1985). An extensive survey of suppliers of beneficial insects and research scientists familiar with Geocoris indicate that the insects arenot in commercial production at the time of this writing (late 2011).
Boyd, M.L. and D.J. Boethel. 1998. Residual toxicity of selected insecticides to Heteropteran predaceous species (Heteroptera: Lygaeidae, Nabidae, Pentatomidae) on soybean. Biol. Control 27: 154-60. Bugg, R. L., F. L. Wackers, K. E. Brunson, J.D. Dutcher. and S.C. Phatak. 1991. Cool-season cover crops relay intercropped with cantaloupe: Influence on a generalist predator, Geocoris punctipes (Hemiptera: Lygaeidae). J. Econ. Entomol. 84: 408-416. Cohen, A.C. 1985. A simple method for rearing the insect predator Geocoris punctipes on a meat diet. J. Econ. Entomol. 7: 1173-1175. Cohen, A.C. 2000 Feeding fitness and quality of domesticated and feral predators: Effects of long term rearing on artificial diet. Biol. Control 17: 50-54. Cohen, A. C. and D.N. Byrne. 1992. Geocoris punctipes as a predator of Bemisa tabaci. Entomol. Exp. et Crocker, Robert L. and W. H. Whitcomb. 1980. Feeding niches of the Big-Eyed Bugs Geocoris bullatus, G. punctipes, and G. uliginosis (Hemiptera: Lygaeidae: Geocorinae). Environ. Entomol. 9: 508-513. Elzen, G. W., P.J. Elzen, and E. G. King. 1998. Laboratory toxicity of insecticide residues to Orius insidiosus, Geocoris punctipes, Hippodamia convergens, and Chrysoperla carnea. Proc. Beltwide Cotton Conf. 2: 1235-1238. Eubanks, M.D. and R. F. Denno. 1999. The ecological consequences of variation in plants and prey for an omnivorous insect. Ecology 80: 1253-1266. Hagler, J.R. and A.C. Cohen. 1991. Prey selection by in vitro- and field-reared Geocoris punctipes. Entomol. Exp. et Appl. 59: 201-205. Hagler, J.R. and S.E. Naranjo. 1994. Determining the frequency of heteropteran predation on sweetpotato whitefly and pink bollworm using multiple ELISAs. Entomol. Exp. et Appl. 72: 63-70. Mengersen, E. 1997. Personal communication. Naranjo, S. E. and J. L. Stimac. 1985. Development, survival, and reproduction of Geocoris punctipes (Hemiptera: Lygaeidae): Effects of plant feeding on soybean and associated weeds. Environ. Entomol. 14: 523-530. Pendleton, Nicole D. 2002. Development and Impact of Geocoris punctipes (Say) (Hemiptera; Lygaeidae) on Selected Pests of Greenhouse Ornamentals. Master’s Thesis, University of Tennessee, Knoxville. Tamaki, G. and R.E. Weeks. 1972. Efficiency of three predators, Geocoris bullatus, Nabis americoferus and Cocinella transversogutata, used alone or in combination against three insect prey species, Myzus persicae, Ceramica picta, and Manastra configurata, in a greenhouse study. Environ. Entomol. 1: 258-263.
Back to Predators Table of Contents
|
|
||
 |
||||
