Cover Crop Effects on Insect Dynamics in Cropping Systems of the Southeastern U.S.

Abstract

Evidence suggests winter cover crops could be useful for augmenting conservation biological control of insect pests in southeastern row crop systems. Management decisions such as selection of cover crop species and irrigation management can potentially influence insect populations, since cover crop species may vary in their ability to attract and sustain complexes of natural enemies. Research is needed to understand the effect of various winter cover crop mixtures on the in-field insect dynamics in Alabama soybean (Glycine max), peanut (Arachis hypogea), and cotton (Gossypium hirsutum) production systems. A study was established at the Tennessee Valley Research and Extension Center (Belle Mina, AL) and the Wiregrass Research and Extension Center (Headland, AL) to assess the effect of crimson clover (Trifolium incarnatum), cereal rye (Secale cereale), and forage radish (Raphanus sativus) cover crops on pest and beneficial insect presence. All cover crops were fall planted and chemically terminated at least two to three weeks prior to cash crop planting. Insect presence was recorded using sweep nets, beat sheets, and visual observations of damage in cash crops. Results showed that crimson clover and radish-clover cover crops can increase beneficial insects such as big eyed bugs (Geocoris punctipes) and lady beetles (Coccinellidae) in north AL. Clover-containing cover crops were also preferable to winter fallow for harboring greater numbers of beneficials in south AL. Rye, clover, and radish-clover cover crops all generally harbored more pest insects than fallow and radish monocultures. Crimson clover cover crops can increase numbers of three cornered alfalfa hoppers (Spissistilus festinus) and bean leaf beetles (Cerotoma trifurcata), while tarnished plant bug (Lygus lineolaris) pests seem to prefer radish-clover bicultures. Winter cover crops are unlikely to enhance beneficial insect persistence during soybean or peanut growing seasons if terminated two to three weeks ahead of cash crop planting. Cover crops had weak impacts on beneficial insects during the cotton growing season in north AL, while rye residue promoted beneficial insect persistence in south AL cotton better than radish cover crops. Soybeans planted into rye-radish-clover mixture residue may benefit from lower amounts of bean leaf beetle pests during the growing season. Center pivot irrigation may increase populations of certain peanut pests such as spotted cucumber beetles (Diabrotica undecimpunctata) and three cornered alfalfa hoppers. Crimson clover cover crops may increase the presence of grasshoppers (Acrididae) and leafhoppers (Cicadellidae) early in the cotton growing season in north AL. While cover crops like crimson clover may attract greater numbers of beneficial and pest insects during the cover crop growing season, they have minimal influence on insect populations during the cash crop growing season in Alabama row crop production systems.