Evaluation of dip treatments for control of Colletotrichum acutatum on strawberry transplants, 2016-17

摘要

Product effectiveness in managing root necrosis and crown rot caused by C. acutatum was evaluated at the Gulf Coast Research and Education Center, Wimauma, FL. Canadian bare-root transplants were inoculated on 10 Oct 16 with a mixture of four C. acutatum isolates, two sensitive and two resistant to Quinone-outside inhibitor (QoI) fungicides. Plants were inoculated by spraying a suspension of 106 conidia/ml onto plant roots using 300 ml per 100 plants. After inoculation, plants were kept at room temperature overnight and were transplanted into plastic-mulched raised beds on 11 Oct 16. Beds were 28 in. wide on 4-ft centers and contained two staggered rows of plants spaced 12 in apart within and 15 in. between rows. Fifteen treatments were arranged ina randomized complete block design with four blocks in neighboring beds. Plots were 10.5 -ft long with 20 plants each, separated by a 3-ft gap without plants. Treatments consisted of submerging (dipping) four bundles of 20 plants each in a 4 gal solutionor suspension of fungicide for 5 min. All treatments were dipped in the field just prior to planting in single marked plots in each replication, except one treatment of Zivion which was dipped indoors to avoid degradation by sunlight. Controls were dipped in water for 5 min before planting. To aid establishment, plants were overhead irrigated for 10 days. Further irrigation and fertilization were done via drip tapes until the end of the evaluations. K-phite, Prophyt, Prophyt + Abound, and Phostrol treatments received an additional foliar spray application 21 days after planting (DAP). Sprays were applied with a CO2 back-pack sprayer, calibrated to deliver 100 gal/A at 60 psi through two T-Jet 8002 hollow-cone nozzles. Plant diameters of 10 staggered plants in each plot were measured 35 DAP using a ruler attached to a clear plastic sheet to push leaves down near the bed. Two perpendicular measurements were made, the first along the longest axis of the canopy. The 10% trimmed average was used to avoidoutliers and estimate plant diameter per plot. Percentage of diseased plants (dead + wilted) was evaluated 42 DAP. Seven harvests were performed from 1 Dec 16 to 29 Dec 16. Yield was determined by counting and weighing marketable fruit, and expressed inlb/A. Plant diameter, plant mortality, and yield were analyzed by fitting a generalized linear mixed model in SAS. Means were separated by Fisher's Protected LSD test (a = 0.05).