Joseph M. Kemble

A Multivirus Epidemic of Tomatoes in Alabama

During 1992, a multivirus epidemic reduced tomato production by as much as 25% in the major tomato-growing region of Alabama. Estimated yield losses of 100% resulted from the epidemic in over 250 ha in two counties of North Alabama. Cucumber mosaic cucumovirus (CMV), alone or in combination with potato potyvirus Y (PVY) and/or tobacco etch potyvirus (TEV), was responsible for the crop failure. CMV was detected alone or in combination with PVY and/or TEV in over 70% of the samples tested and was present in 90% of the fields surveyed. In 1993, 21 tomato fields were monitored weekly from transplanting through harvest for CMV, PVY, TEV, tobacco mosaic tobamovirus, and tomato spotted wilt tospovirus. All 5 viruses were detected, with CMV occurring most frequently. Incidence of CMV at the 61% level or higher was found in 16 of the 21 fields surveyed. Tomatoes transplanted in April and May were least effected and had relatively low virus incidence until late in their development. Tomatoes transplanted in June and July were infected at an earlier age, had the highest virus incidence, were the most severely affected, and suffered the greatest loss in yield. In 1994,Aphis gossypii, the cotton aphid, was the most common virus vector found during an aphid monitoring/virus spread study. Populations of A. gossypii peaked in late June, immediately preceding a period of rapid CMV incidence and spread.

Growth, fruiting and ethylene binding of tomato plants in response to chronic ethylene exposure

Summary‘Red Robin’ tomato plants were grown in chambers containing 0, 0.01, 0.05 or 0.1 µl l−1 ethylene in the atmosphere. Plants in 0.05 or 0.1 µl l−1 ethylene had epinastic leaves. At 0.01 µl l−1 ethylene, visual symptoms were difficult to detect unless an untreated plant was used as a comparison. Even the smallest tested concentrations of ethylene reduced fruit numbers. Plant height of this dwarf tomato variety was not greatly affected by ethylene exposure. Plants exposed to any concentration of ethylene had almost double the ethylene binding capacity of plants grown in ethylene-free air. When plants growing in air were treated with diazocyclopentadiene, an ethylene binding site inhibitor, shoot fresh weight increased, but plant height did not. Thus, endogenous ethylene plays little to no role in determining plant height in this variety.

No-till with high biomass cover crops and invasive legume mulches increased total soil carbon after three years of collard production

ABSTRACT Studies have shown that conversion to conservation tillage from conventional tillage does not increase total soil organic carbon (SOC) significantly in the short term (<5 yrs). While no-till increases total SOC in the medium to long term, it was hypothesized that the inclusion of high biomass cover crops and organic mulches may increase total SOC in the short term. The use of invasive, perennial leguminous species as mulch may sustainably increase SOC during limited-input fall vegetable production. The objective of this study, conducted in Alabama (USA), was to quantify total SOC changes due to organic mulches and forage soybean (Glycine max (L.) Merr. cv. Derry) as a summer cover crop after conversion to no-till during limited-input fall collard (Brassica oleracea L.) production. Forage soybean as a summer cover crop did not increase SOC. No-till without mulch (control treatment) significantly increased SOC at 0–5 cm from 6.3 to 14.0 g kg−1 soil in 3 yrs, whereas inclusion of cut-and-carry mulches increased SOC to ≥22.6 g kg−1 soil. Treatments did not affect collard yield, which averaged 17,863 kg ha−1 yr−1. This represents a novel, limited-input system that may help control on-farm invasive species while sustainably increasing SOC in the short term.