Abstract
Simple SummaryAccording to USA organic standards, farmers can apply a certified allowable insecticide when all non-chemical practices fail to control pests. However, there exists a lack of control efficacy information to enable decision-making about which organic product works best for a given target pest. In this study, we conducted 153 field trials on different host crops to evaluate the control efficacy of common active ingredients in organic insecticides against insect pest groups considered difficult to control in organic production. The performance of organic products Entrust (spinosad), Azera (pyrethrin and azadirachtin), PyGanic (pyrethrin) and Neemix (azadirachtin) varied widely among pest groups, as well as among pest species within a group, providing an overall reduction in pest infestations by 73.9%, 61.7%, 48.6% and 46.1%, respectively. Those insect pests that were particularly difficult to control included thrips, stinkbugs, cucumber beetles and fruitworms. Several caveats pertaining to the application of the results are discussed.There exists a lack of control efficacy information to enable decision-making about which organic insecticide product works best for a given insect pest. Here, we summarize results of 153 field trials on the control efficacy of common active ingredients in organic insecticides against 12 groups of the most difficult to control insect pests. These trials evaluated primarily the organic products Entrust (spinosad), Azera (pyrethrin and azadirachtin), PyGanic (pyrethrin) and Neemix (azadirachtin), which reduced pest infestations by an overall 73.9%, 61.7%, 48.6% and 46.1% respectively, averaged across all trials. Entrust was the most effective control option for many insect pests, particularly providing >75% control of flea beetles, Colorado potato beetle, cabbageworms and alfalfa weevil, but was relatively ineffective against true bugs and aphids. Azera provided >75% control of green peach aphid, flea beetles, Japanese beetle, Mexican bean beetle, potato leafhopper and cabbageworms. PyGanic was less effective than Entrust and Azera but still provided >75% control of green peach aphid, flea beetles and potato leafhopper. The growth inhibition effects of azadirachtin in Neemix were particularly effective against larvae of Mexican bean beetle and Colorado potato beetle but was generally less effective in trials with insect infestations consisting mainly of adult stages. Those insect pests that were particularly difficult to control included thrips, stinkbugs, cucumber beetles and fruitworms. Several caveats pertaining to the application of the results are discussed.
Highlights
Organic production in the U.S has experienced phenomenal growth since the 1990s, with double-digit increases in the number of certified farms during most years and current productionInsects 2020, 11, 614; doi:10.3390/insects11090614 www.mdpi.com/journal/insectsInsects 2020, 11, 614 accounting for 5.8% of total food sales in 2019 [1]
We focused on 12 pest groups that are considered difficult to control in organic production, as indicated in several farmer surveys [20,21] and identified by Caldwell et al [15] as important pests that lack organic insecticide efficacy data
Percent control among treatments was not statistically different based on overlapping 95% CL, except for PyGanic, which gave significantly higher control of harlequin bug (HB) compared to the other insecticides
Summary
Organic production in the U.S has experienced phenomenal growth since the 1990s, with double-digit increases in the number of certified farms during most years and current productionInsects 2020, 11, 614; doi:10.3390/insects11090614 www.mdpi.com/journal/insectsInsects 2020, 11, 614 accounting for 5.8% of total food sales in 2019 [1]. In dealing with pest management, organic farmers are challenged with the same insect pests confronting conventional farmers; they must rely first on a system-based use of biological, cultural, mechanical and physical practices to reduce or avoid pest problems. Three major categories of insecticides widely used in organic production include products formulated with spinosad, pyrethrin and neem derivatives. These active ingredients are contained in about one third of the insecticidal products allowed for organic use. Spinosad is a natural product composed of a mixture of spinosyns A and D fermentation metabolites of a soil-dwelling actinomycete, Saccharopolyspora spinosa [4] It has broad-spectrum activity against many major lepidopteran pests, thrips, leaf miners and certain beetle species, and is an active ingredient in several conventional insecticides. Depending on the formulation and application method, neem constituents can be absorbed through plant roots and leaves [11,12,13,14], providing some level of systemic activity on certain insect pests
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