Interactive effects of cultivation, insect control, and fungal disease control in organic peanut production

Authors: Johnson, Wiley - Carroll; CULBREATH, ALBERT - University Of Georgia; LUO, XUELIN - University Of Georgia

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2018
Publication Date: 7/30/2018
Citation: Johnson, W.C., Culbreath, A.K., Luo, X. 2018. Interactive effects of cultivation, insect control, and fungal disease control in organic peanut production. Peanut Science. 45:38-44.

Interpretive Summary: In conventional peanut production, there are numerous pesticide applications to control common peanut pests, adding to the cost of peanut production. During previous organic peanut weed management trials, maintenance pesticides were not applied and it was observed that insect infestations and disease epidemics were not problematic. It was hypothesized that components in the organic peanut production system could be integrated into conventional peanut production and reduce pest management inputs. Research trials were conducted from 2012 through 2014 to determine interactions among three levels of weed control, two levels of insect control, and three levels of fungal disease control in organic peanut production. Weed control treatments were weed-free using handweeding, cultivation with a tine weeder, and a non-cultivated (weedy) control. Insect control treatments were two early-season applications of spinosad (OMRI approved) and a nontreated control. Fungal disease control treatments were applications of cupric oxide plus sulfur (Cu+S) at three-week intervals, the conventional fungicide azoxystrobin at three-week intervals, and a nontreated control. The peanut cultivar GA-04S was planted each year of the study. Compared to the non-cultivated control, cultivation with a tine weeder consistently reduced weed densities, and yields were equivalent to handweeded peanut two years of three. Intensive cultivation with a tine weeder did not increase disease epidemics and reduce peanut yield, which is contradictory to long-standing peanut production recommendations. Spinosad applications did not affect any of the parameters measured, including incidence of thrips-vectored spotted wilt and peanut yield. Cu+S controlled peanut diseases equal to azoxystrobin two years out of three, but peanut yields did not consistently respond to better disease control from the conventional fungicide. Ideal crop rotations to reduce disease inoculum and modern peanut cultivars with improved disease tolerance are factors that allow the use of these reduced pest control inputs, which offers potential to reduce pesticide use in conventional peanut production.

Technical Abstract: During previous organic peanut weed management trials, maintenance pesticides were not applied and it was observed that insect infestations and disease epidemics were not problematic. This was surprising considering that conventional peanut are routinely treated with insecticides and fungicides to control common peanut pests. It was hypothesized that components in the organic peanut production system could be integrated into conventional peanut production. Research trials were conducted from 2012 through 2014 to determine interactions among three levels of weed control, two levels of insect control, and three levels of fungal disease control in organic peanut production. Weed control treatments were weed-free using handweeding, cultivation with a tine weeder, and a non-cultivated (weedy) control. Insect control treatments were two early-season applications of spinosad (OMRI approved) and a nontreated control. Fungal disease control treatments were applications of cupric oxide plus sulfur (Cu+S) at three-week intervals, the conventional fungicide azoxystrobin at three-week intervals, and a nontreated control. The peanut cultivar GA-04S was planted each year of the study. Compared to the non-cultivated control, cultivation with a tine weeder consistently reduced weed densities, and yields were equivalent to handweeded peanut two years of three. Intensive cultivation with a tine weeder did not increase disease epidemics and reduce peanut yield, which is contradictory to long-standing peanut production recommendations. Spinosad applications did not affect any of the parameters measured, including incidence of thrips-vectored spotted wilt and peanut yield. Cupric oxide plus sulfur controlled peanut diseases equal to azoxystrobin two years out of three, but peanut yields did not consistently respond to better disease control from the conventional fungicide. Ideal crop rotations to reduce disease inoculum and modern peanut cultivars with improved disease tolerance are factors that allow the use of these reduced pest control inputs.