Location: Crop Protection and Management Research
Title: Use of winter legumes as banker plants for beneficial insect species in a sorghum and cotton rotation system. Authors
Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 2012
Publication Date: July 15, 2012
Citation: Olson, D.M., Webster, T.M., Scully, B.T., Strickland, T.C., Davis, R.F., Knoll, J.E., Anderson, W.F. 2012. Use of winter legumes as banker plants for beneficial insect species in a sorghum and cotton rotation system. Journal of Entomological Science. 47:350-359. Interpretive Summary: Use of novel crops for bio-fuel production requires evaluating the potential for sound ecological and economical implementation in a particular region. We examined the pest and generalist beneficial insect species associated with various winter cover crops (including narrowleaf lupin, white vetch, Austrian winter pea, crimson clover, faba bean, and rye) as sources of colonists in two subsequent summer crops, sorghum and cotton. Sorghum is a potential cellulosic bio-fuel crop and cotton is commonly grown in the region and could be a viable low-input rotation for biofuel sorghum. Insects were sampled weekly over three years in winter cover plots beginning in early spring and in the later planted crop plots beginning at the 15 cm height stage of the crops and continuing for 3-6 weeks. Of the predators, coccinellids dominated and were consistently abundant in vetch, faba and lupin, as was the pea aphid, Acyrthosiphon pisum and the aphid parasitoid, Lysiphlebus testaceipes. Orius spp. dominated in lupin. Of the pest species, thrips spp. were highest in lupin and pea, and stink bugs were highest in clover. No differences in chinch bugs were found among the covers. There was a ‘relay’ of these species into all of the summer crop plots from living winter crops. Boll damage from stink bugs was highest in the cotton following lupin, pea and fallow with fertilizer; there was no damage from chinch bugs in sorghum. Faba beans had declining stands over the three years, suggesting that this species would not be a reliable winter crop in this system. Vetch and lupin may be the best candidates as banker plants because of their ability to consistently sustain pea aphids and coccinellids, the former which is a non-pest of sorghum and cotton.
Technical Abstract: Agricultural practices that use conservation tillage and cover crops are promoted for their benefits to soil quality, weed suppression and water conservation. They are also noted for the ability to encourage biological control. We examined the pest and generalist beneficial insect species associated with various leguminous winter cover crops as sources of colonists in two subsequent summer crops, sorghum and cotton. A sorghum and cotton rotation system would fit well in the region for bio-fuel and cotton production. Covers were planted in November and insects were sampled for 3-5 weeks prior to the summer crop. The summer crop was sampled for 3 weeks beginning when the plants were 6 cm tall. Coccinellid predators consistently dominated in the vetch, faba and lupin, along with their prey, the pea aphid, Acyrthosiphon pisum. The pest species, thrips spp. were highest in lupin and pea, and their predator, Orius spp. also dominated in lupin. The pea aphid is not a pest of cotton or sorghum and population build-up of the generalist predators, coccinellids and Orius spp. may be useful for biological control of pests species in the cotton and sorghum summer crops.