Evaluation of biological fungicides to control common diseases of Brassicas

摘要

The experiment was conducted at the University of Massachusetts Research and Education Farm in South Deerfield, MA in a field with Hadley silt loam soil. 'Champion' collards seeds (Johnny's Selected Seeds, ME) were sown in 128-cell flats on 19 Jun andwere maintained under greenhouse conditions for five weeks. Seedlings were fertilized with 2-4-1 (N-P-K) fish emulsion (Neptune's Harvest) on 26 Jul. Seedling flats were drenched with Admire 2F (imidacloprid) at 20 fl oz/A on 29 Jul to prevent flea beetle feeding before the plants were moved outside to harden off. Field preparation included amending soil with 10-10-10 (N-P-K) fertilizer at a rate of 750 lb/A and 2.5 lb/A boron (Solubor) as per UMass soil test recommendations. Treflan (trifluralin) at 1.5 pt/A was applied 30 Jul before transplanting for control of grass weeds. A randomized complete block design was used, with each treatment replicated four times in 25-ft blocks and 5-ft buffers planted between blocks as well as around the perimeter ofthe experimental area. A one-row transplanter with a water wheel was used to plant collards seedlings at 15-in. spacing into rows with 6-ft centers on 31 Jul. Entrust WDG at 2.5 oz/A plus an adjuvant (NuFilm P) was sprayed by tractor mounted boom on 13 Sep to control flea beetles and lepidopteran pests. Spray treatments were applied on approximately a 10-day spray interval beginning on 14 Aug and a total of five applications were made using a CO_2 pressurized backpack sprayer delivering 50 gal/A at 50 psi through two TeeJet 8002VS flat fan nozzles spaced 19-in. apart and two TeeJet 8002VS flat fan nozzles on 19-in. drop booms 34-in. apart to ensure complete plant coverage. When plants became too large for this boom, the drop nozzles were moved to 57-in. apart and this setup was used beginning Sep 23 and for all subsequent sprays. Eight materials were tested in comparison to a positive control (Quadris) and an untreated control (H_2O). An adjuvant (NuFilm P) at a rate of 1 pt/100 gal was used in all spray mixes to improve coverage and increase spray efficacy. Due to the proximity of commercial farms, the trial was not inoculated. Disease severity of Alternaria leaf spot (ALS) and black rot (BR) was assessed by visually estimating the percentage of leaf area affected by each disease on ten plants at the center of each replicate plot. Plants were observed weekly throughout the season but disease pressure was low and spread slowly, so complete ratings were carried out only three times, on 06 Sep, 19 Sepand 25 Oct. Average monthly high and low temperatures (°F) were 94.8/55.8, 88/47.6, 91.9/35.5, 78.2/24.8 in Jul, in Aug, in Sep, and in Oct. Total rainfall (inches) was 4.87, 4.10, 3.88, and 1.02 for these months, respectively. Overhead irrigation wasapplied via pressurized water-wheel on 23 Aug to maintain crop health and encourage disease development.