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Theodore P. McAvoy and Joshua H. Freeman

Alternative soil fumigants are needed to replace methyl bromide (MBr). One possible MBr alternative is dimethyl disulfide (DMDS). Highly impermeable plastic films such as virtually impermeable film (VIF) and totally impermeable film (TIF) can be used to increase fumigant retention. Possible advantages of increased fumigant retention are decreased fumigant use rates, decreased buffer zone requirements, reduced fumigant emissions, and improved pest control. Reduced fumigant emission may be especially important with DMDS because it has a sulfur odor, which is easily perceivable by the human nose. One potential drawback of decreasing film permeability may be longer plant back intervals, especially during periods with cool wet soils. The objective of these experiments was to evaluate the effect of TIF on DMDS retention at various rates compared with VIF. Experiments were conducted at the Virginia Tech Eastern Shore Agricultural Research and Extension Center (ESAREC) in Painter, VA, using high (561 L·ha−1), standard (468 L·ha−1), and reduced application rates (374, 281, and 187 L·ha−1) of DMDS in combination with TIF and VIF during spring and fall seasons. Soil temperature and fumigant concentration within the soil were recorded. A stepwise decrease in fumigant retention was seen as fumigant rates were reduced under TIF. Retention periods were impacted by soil temperature. High temperatures decreased the retention period and low temperatures increased the retention period. Standard fumigant rates (468 L·ha−1) under VIF resulted in similar fumigant concentrations in the soil as 281 L·ha−1 under TIF. Similar fumigant concentrations and possibly similar planting interval can be achieved by reducing fumigant use rates ≈40% to 50% under TIF compared with VIF.

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Theodore McAvoy, Joshua H. Freeman, Steven L. Rideout, Stephen M. Olson and Mathews L. Paret

Seven hybrid tomato rootstocks with possible resistance to bacterial wilt caused by Ralstonia solanacearum and a known resistant cultivar were tested as grafting rootstocks to impart resistance to a bacterial wilt-susceptible cultivar, BHN 602. Greenhouse studies showed resistance of all the rootstocks to bacterial wilt. The disease incidence and yield of ‘BHN 602’ grafted to these rootstocks were evaluated in open-field tomato production in Florida and Virginia over four seasons. Significant differences in bacterial wilt incidence were observed between grafted entries in three of the four trials. In these three trials, grafted entries consistently exhibited the least bacterial wilt incidence compared with the controls; the self-graft, and non-grafted entries. Over all the trials, tomato plants grafted onto ‘Cheong Gang’, ‘BHN 1054’, and ‘BHN 998’ displayed the least bacterial wilt incidence. Rootstocks had a significant effect on total marketable yield in all the trials with certain grafted entries yielding significantly greater than non-grafted ‘BHN 602’. Field studies show that grafting holds promise for decreasing the impact of bacterial wilt on tomato cultivars as well as increasing the overall productivity of tomato cultivars.