|Kubota, Chieri - UNIVERSITY OF ARIZONA|
Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: September 1, 2008
Publication Date: October 1, 2008
Citation: Burelle, N.K., Rosskopf, E.N., Bausher, M.G., Mccollum, T.G., Kubota, C. 2008. Alternative fumigants and grafting for tomato and double-cropped muskmelon production in Florida. Proceedings of International Research Conference on Methyl Bromide Alternatives. 63:1-2. Technical Abstract: A field trial was conducted at the USDA, ARS Farm in Fort Pierce, FL in a field infested with root-knot nematodes (RKN) (Meloidogyne incognita), soil-borne pathogens, and weeds. A split plot experiment with four replications was used to evaluate rootstock/scion combinations in fumigated and herbicide-only treated soil. Four main plot soil treatments were applied under metalized film including methyl bromide (200 lbs/a, 67:33), iodomethane (100 lbs/a, Midas®), dimethyl disulfide (50 gal/a, 79:21 DMDS, Paladin™), and an herbicide-only control (Dual Magnum™, Matrix®, and Sandea®). Subplot treatments in the primary tomato crop were three rootstocks with reported resistance to RKN (‘TX301’ (Syngenta Seeds), ‘Multifort’ (De Ruiter Seeds), and ‘Aloha’ (American Takii), and the non-grafted scion, ‘Florida-47’ (Asgrow Seed) on its own rootstock. A double-crop of muskmelon was planted into the existing beds in the spring. Two muskmelon rootstocks, C. metulifer (Trade Wind Fruit Co.) and ‘Tetsukabuto’ (Takaii Seed) were evaluated with the non-grafted scion ‘Athena’ (Syngenta Seed) on its own rootstock. Each melon rootstock was planted into subplots previously occupied by each tomato rootstock. Crops were managed using recommended commercial practices for Florida tomato and muskmelon production, and were evaluated for growth, disease and nematode resistance, yield, and graded fruit. Weed populations were assessed for fumigant treatments at planting, mid-season, and harvest. Early and midseason soil nematode counts showed no differences among soil treatments for effects on RKN populations. Late season soil counts were higher in the herbicide-only plots, and RKN populations extracted from tomato roots at harvest were higher/g of root tissue in the herbicide-only plots. Non-grafted rootstocks supported higher populations of RKN in soil and roots at the end of the season than all other rootstocks. Interactions occurred between soil treatments and rootstocks with regard to galling by RKN. The highest rates of galling occurred in herbicide-only soil and non-grafted plants. ‘Multifort’ and ‘Aloha’ provided the best resistance to galling in herbicide-only treated soil of the rootstocks tested. No differences in galling occurred among rootstocks in soil treated with methyl bromide, methyl iodide, or DMDS. All soil treatments controlled weeds throughout the tomato crop. Soil treatments did not affect tomato plant vigor ratings early in the season but by midseason, methyl bromide had higher plant vigor compared to all other soil treatments. Late in the season, methyl bromide was only different from the herbicide-only control with respect to plant vigor. All soil treatments increased plant height, shoot weight, and root weight at mid- and late season compared to the herbicide-only control. ‘Aloha’ rootstock produced less vigorous plants at both mid- and late season than all other rootstocks. Plant height at midseason was lower for ‘Aloha’ and ‘TX301’ compared to the nongrafted controls. Sprouting from the rootstocks occurred in all grafted varieties but less so for ‘TX301’ and ‘Aloha’ then ‘Multifort’. At the end of the season, ‘Multifort’ and ‘TX301’ had the highest shoot and root weights, and best root condition ratings of all plant types. The effects of soil treatments on nematodes and weeds were sustained in the melon double-crop. In February, all soil fumigants had lower RKN populations than the herbicide-only control, with methyl iodide having significantly lower numbers. By midseason of the melon crop, nematode populations had rebounded in all treatments. At the end of the melon crop only DMDS had lower numbers of RKN isolated from roots than the herbicide-only control. Of the rootstocks tested, C. metulifer supported lower RKN populations in both soil and roots at the end of the season than either the non-grafted control or ‘Tetsukabuto’. Previously planted tomato rootstock had an effect on galling of melon with highest galling occurring following non-grafted tomato in all soil treatments. Weed populations remained low through the second crop and there were no differences between treatments until the harvest counts, when the herbicide-only treatment had the greatest number of weeds per plot. Although the number of weeds was different, the populations were minimal and no differences in fresh or dry biomass of weeds occurred at melon harvest. Melon vine growth measured in March was lower in the herbicide-only control than in all other soil treatments. All fumigants increased total fruit weight of melons compared to the herbicide-only treatment. Total fruit weight, average fruit weight, and fruit weight/plant were higher in C. metulifer and ‘Tetsukabuto’ compared to non-grafted melon. Previously planted tomato rootstock had an effect on total fruit weight of melon with ‘Aloha’ increasing total fruit weight of melon compared to melons following non-grafted tomato.