Improving recommendations for grape berry moth and fruit rot management in high brix Niagara grape production
B. HED (1), J. Timer (2), T. Weigle (3). (1) Lake Erie Regional Grape Research & Extension Center, North East, PA, U.S.A.; (2) Pennsylvania State University, North East, PA, U.S.A.; (3) Cornell University, Portland, NY, U.S.A.
The production of high brix grape juice (<i>Vitis labrusca</i> ‘Niagara’) requires a delay in harvest increasing the risk of loss from fungal fruit rots. Our objective was to evaluate that risk and improve pesticide recommendations for high brix Niagara production by comparing a current grower standard (GS) pesticide program to an IPM strategy utilizing site specific weather and pest information. In both years of the study, fruit rot (<i>Botrytis cinerea</i>) increased with delay of harvest and was associated with grape berry moth (<i>Polychrosis viteana</i>) infestation (GBM). In 2011, there was significantly more GBM damage at 14 brix with the GS than the IPM program, but no significant difference with respect to fruit rot (<i>P</i> ≤ 0.05). With delay of harvest (16 brix), the severity of GBM damage was 37% greater in the GS than the IPM program, and the IPM program significantly reduced fruit rot by 28% over the GS. In 2012, there was no difference in rot between programs at 13 brix, but at 16 brix the IPM program had 44 % less rot than the GS though the difference was not significant. Phomopsis fruit rot (<i>Phomopsis viticola</i>) was not an issue in either year, but the IPM program significantly reduced the incidence and severity of Phomopsis shoot lesions in 2012 when compared to GS, due to an early mancozeb spray at 3-5” shoots. Better timing of insecticide sprays through the IPM treatment reduced losses to rots when harvest was delayed for higher brix accumulation.
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