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Title: Effects of A Killed-Cover Crop Mulching System on Sweetpotato Production, Soil Pests, and Insect Predators in South Carolina

Author
item Jackson, D
item Harrison Jr, Howard

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2008
Publication Date: 12/1/2008
Citation: Jackson, D.M., Harrison Jr, H.F. 2008. Effects of A Killed-Cover Crop Mulching System on Sweetpotato Production, Soil Pests, and Insect Predators in South Carolina. Journal of Economic Entomology. 101:1871-1880.

Interpretive Summary: Sweetpotatoes are typically grown on bare soil where weeds and soil erosion can be problems. Conservation tillage systems using cover crop residues as mulch can help reduce these problems, but little is known about how killed-cover crops affect sweetpotato production or population levels of pest and beneficial insects. In this study, we evaluated a conservation tillage system for sweetpotatoes that utilized a killed-cover crop. Three sweetpotato genotypes were grown in either conventionally tilled plots or in a killed-cover crop tillage system in which the weeds were either controlled by hand weeding or left uncontrolled. In general, yields were as high or higher in the killed-cover crop plots than in the conventional tillage plots, while injury to sweetpotato roots by soil insect pests was lower in the conservation tillage plots than in the conventional tillage plots. This study indicates that killed-cover crop mulches can be used in sweetpotato production without causing increased insect damage or reduced yields.

Technical Abstract: Sweetpotato, Ipomoea batatas (L.) Lam., is typically grown bare soils where weeds and erosion can be problematic before plants become established. Conservation tillage systems for sweetpotato may help alleviate these problems. Therefore, one insect-resistant (‘Ruddy’) and two insect-susceptible (‘SC1149-19’ and ‘Beauregard’) sweetpotato genotypes were grown in either conventionally tilled plots (CT) or in a killed-cover crop (KCC) tillage system at the US Vegetable Laboratory, Charleston, SC, in 2002-2004. The four tillage treatments were: (1) conventional tillage, hand-weeded (CT-HW), (2) killed-cover crop, hand-weeded (KCC-HW), (3) conventional tillage, weedy (CT-WE), and (4) killed-cover crop, weedy (KCC-WE). In the fall, one-half of the pre-formed beds were planted to a winter cover crop of an oat and crimson clover mixture, while the other one-half of the beds were left fallow then bedded before sweetpotato slips were planted. One-half of each 4-row plot (100 plants per plot) was hand-weeded while the other one-half was not. The CT-WE plots had 10 times as many monocots and 3 times as many dicots as the KCC-WE plots. The center-two rows of sweetpotatoes from each plot were harvested, weighed, and rated for insect damage. The insect resistance of Ruddy held up well under the killed-cover crop conditions, and this cultivar had significantly higher percent of clean roots and lower infestations by WDS (Wireworm-Diabrotica-Systena complex), sweetpotato flea beetles, grubs, and sweetpotato weevils than the two susceptible genotypes. In general, injury to sweetpotato roots by soil insect pests was significantly lower in the KCC plots than in the CT plots. Also, injury by sweetpotato weevils was significantly less in the weedy than in the hand-weeded plots. Pitfall traps and fire ant sampling indicated that more beneficial predators were present in the killed cover crop plots.