Swede Midge, Diamondback Moth, and Imported Cabbageworm Control With Insecticides Allowed for Organic Production, 2014 *

This trial was conducted to evaluate insecticides approved for use in organic production. The trial was conducted on a field managed using practices allowed for organic production since 2008 at Cornell’s New York State Experiment Station in Geneva, NY. Broccoli ‘Belstar F1’ with 3–4 true leaves was transplanted on 2 Jun 2014. The transplants were set by hand using a Water Wheel transplanter (Rain-Flo Irrigation, Lancaster, PA) with a solution of 0.5oz/gal Fertrell fish oil emulsion into raised beds with 1.25 mil black polyethylene and drip irrigation tape. Annual ryegrass was seeded between the rows for weed control and mowed as needed. Six treatments and an untreated check were arranged in a RCB design with four replications. Each plot consisted of six plants spaced 12 inch apart with 7 ft between rows and 2 ft between treatments. Sprays (with the exception of Surround) were applied with a CO ₂ pressurized backpack sprayer at 40 psi delivering 40 gpa through two TeeJet 8002VS flat fan nozzles spaced 19 inch apart. Surround was applied to thoroughly cover the foliage, using a hand pump pressurized sprayer with a single nozzle. Treatments included Azera (pyrethrum plus azadirachtin) at 3.5 pt/acre, Grandevo ( Chromobacterium substugae strain PRAA4-1 and spent fermentation media) at 3 lb/acre, Surround (kaolin clay) at 0.5 lb/gal, Venerate (heat-killed Burkholderia sp.) at 4 qt/acre, Veratran D (Sabadilla alkaloids) at 15 lb/acre, a Nu-film P only check, and an untreated check. Nu Film P (6 oz/acre) was added to all treatments to improve spray adhesion. The first spray was applied 18 Jun. Five more sprays were applied on 26 Jun, 3, 10, 16, and 24 Jul. The last application occurred just before head formation. On 10 Jul, lepidopteran larvae were counted on all plants. Bacillus thuringiensis kurstaki was applied to all plots on 11 Jul to reduce populations of Lepidoptera that might impact swede midge injury. On 7 Aug, plots were rated for swede midge damage using a visual damage rating scale, where 0 is no damage, 1 is mild twisting of stem or leaves and/or mild swelling of petioles, 2 is severe twisting of stem and/or crumpling of leaves and/or swelling of florets, and 3 is death of apical meristem and/or multiple compensatory shoots. Broccoli with a damage rating of 0 or 1 at harvest usually produces marketable crowns. As crowns matured between 7 and 30 Aug, they were measured and harvested. Crowns >4 inch diameter were considered marketable. Data were analyzed using the Kruskal–Wallis non-parametric test because of the qualitative nature of the damage rating data and the lack of fit to the normal distribution of the head formation, percent marketable heads, and lepidopteran data. Steel–Dwass All Pairs comparisons were conducted on all data to separate treatment means.

Average maximum temperatures for 2–30 Jun, 1–31 Jul, and 1–30 Aug, were 77.0, 77.7, and 75.8°F; average minimum temperatures were 57.9, 59.3, and 57.4°F. Rainfall amounts (inch) were 3.2, 7.8, and 2.4 for 2–30 Jun, 1–31 Jul, and 1–30 Aug, respectively.

Swede midge pressure was light, with average damage ratings of 1.67 and 21% of plants not forming heads in the untreated check ( Table 1 ). The Veratran and Surround treatments significantly reduced mean damage ratings compared with the untreated check. The Azera, Grandevo, Venerate, and Nu-film only treatments were not significantly different from either the untreated check or the Veratran and Surround treatments. There were no significant differences in the percent of plants forming crowns or percent marketable crowns among the spray treatments and the check. Populations of lepidopteran larvae (diamondback moth and imported cabbageworm) after 3 sprays averaged 3.4 per plant in the untreated check, which was not statistically different from any other treatment except Azera ( Table 2 ).

Author notes