Progress 06/01/06 to 05/31/07
Outputs
1) Four replicated 10x10 meter plots of the following treatments were planted in a randomized complete block design: a. Monoculture of Norland (red skinned, susceptible variety) b. Monoculture of the resistant breeding program clone (NY-131 white skin) c. 50:50 mixture of Norland and NY-131 mixed in the row d. 50:50 mixture of susceptible and resistant alternated by row Potato leafhopper adults were sampled in all plots twice (6/29 and 7/6) using a D-Vac suction sampler. Nymphs were counted in all plots twice (7/17, 7/24), on ten fully expanded leaves from the inner ten feet of rows adjacent to the center row, taking 5 leaves from each row. Yield was measured on the middle twenty-foot sections of rows 4 through 7. Analysis of variance was used to compare adult and nymph PLH populations and yields. An efficacy trial including two products approved for organic production was conducted in a randomized complete block design with four replicated 12 ft. single-row plots per
treatment, separated by skip rows. Treatments were applied with an R&D CO2 backpack sprayer. Each treatment received three applications at weekly intervals. Pyganic 1.4 EC (32 oz/A) - starting at adult arrival (June 21, June 30; July 7) Pyganic 1.4 EC (32 oz/A) - starting at nymph hatch (July 12, July 19, July 25) Pyganic + Surround (25 lb/A) - starting at adult arrival (June 21, June 30; July 7) Pyganic + Surround (25 lb/A) - starting at nymph hatch (July 12, July 19, July 25) Untreated control Plots were rated 2 times (14 and 26 July) for PLH injury. PLH nymphs were counted two times (13 and 26 July) on five fully expanded leaves per plot. Yield was estimated for each treatment by harvesting the middle 6 ft. of each plot and averaging over replicates. Data were analyzed by analysis of variance. Varietal mixture trial: The seasonal mean number of PLH adults was not significantly reduced in the in-row mixture compared with the average of the monoculture plots, or on the Norland in the
alternate row plots compared with the Norland monoculture. The seasonal mean number of nymphs on Norland plants was significantly reduced in the in-row mixture compared with the monoculture, but not in the alternate row mixture. Hopperburn on Norland plants in the in-row mixture was rated significantly lower than on the monoculture, but not in the alternate row mixture. Yield of Norland was not significantly higher in either mixture compared with the monoculture. While the in-row mixture did significantly reduce the number of PLH nymphs and the hopperburn rating on the susceptible Norland in the mixture, the reduction was apparently not enough to improve yield compared with a monoculture planting. Efficacy Trial PLH nymph populations were significantly reduced in both of the adult-arrival-timed treatments, and hopperburn ratings were significantly reduced in all but the Pyganic + Surround at adult-arrival treatment. Yield was significantly increased in all treatments, compared with
the untreated control, with no significant differences among treatments. The addition of Surround to Pyganic did not improve control, and time of initiation of control does not appear to be critical for improving yield.
Impacts
This project provided organic farmers with information about the efficacy of two different approaches to controlling potato leafhopper on potatoes. Organic farmers have been shown to suffer reduced yields in potatoes from damage caused by potato leafhopper feeding. Few insecticides allowed for use in certified organic production are effective against potato leafhopper. Crop and varietal mixtures have been demonstrated to reduce pest pressure in some other cropping systems. We demonstrated that mixtures of varieties resistant and susceptible to potato leafhopper did not reduce damage in the susceptible variety enough to prevent yield loss. Our efficacy trial demonstrated that three weekly applications of Pyganic, a pyrethrin product allowed for organic production, significantly reduced leafhooper populations and increased yield, whether initiated at first adult invasion, or the first appearance of nymphs. An economic analysis showed that yield protection provided by the
Pyganic applications more than compensated for the cost of the product. We demonstrated that the addition of Surround, a kaolin clay product, did not significantly improve the level of control compared with Pyganic alone.
Publications
- No publications reported this period
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