Richard B. Chalfant

Soilborne pathogens in a vegetable double-crop with conservation tillage following winter cover crops

Abstract A cucumber-cucumber double-crop followed by a cucumber-snap bean double-crop was grown in a system using conservation tillage in relay-cropping following winter cover crops. Twenty different winter covers were legumes, grasses, legume-grass mixtures, crucifers, or fallow (no cover, resident vegetation). Population densities of Pythium spp. (primarily P. irregulare ) and Rhizoctonia solani anastomosis group (AG-4) were greater following legumes than following grasses or fallow; legume-grass mixtures and crucifers were intermediate. Cucumber fruit rot (induced primarily by R. solani AG-4) was more severe following legumes and crucifers than following grasses; legume-grass mixtures were intermediate. In the snap bean crop following cucumber, root and hypocotyl diseases were more severe following winter covers of legumes or fallow than following grass or legume-grass mixtures; crucifers were intermediate. Root-knot nematodes ( Meloidogyne incognita ) caused injury to the second vegetable crop each year in all winter cover rotations.

Influence of film mulches and soil pesticides on root diseases and populations of soil-borne fungi in vegetables

SummaryField plots of Tifton loamy sand were treated with various soil pesticides and left exposed or covered with biodegradable paper or black polyethylene film mulch. Cucumber, squash, muskmelon, sweetcorn, and polebean were planted in one or more experiments. Trickle irrigation under the film was used in several tests. Isolations were made from roots of all crops except sweetcorn, and the fungi most commonly isolated wereFusarium oxysporum, Pythium spp.,F. solani, F. roseum, andRhizoctonia solani from cucurbits andF. solani andF. oxysporum from polebean. Significantly fewer fungi were isolated from plants grown in soil treated with DD-MENCS (20% methyl isothiocyanate +80% chlorinated C3 hydrocarbons) or methyl bromide-chloropicrin (2:1) (MBC) than from controls, and populations ofPythium spp.,F. solani, andF. oxysporum, were reduced in soil. Sodium azide, sodium azide +ethoprop or carbofuran, and sodium methyl dithiocarbamate were less effective than DD-MENCS and MBC.

Occurrence of fleshy fungi from agricultural fields

Thirteen species of fleshy fungi were identified from two agricultural fields during the 1989 and 1990 growing seasons at the Rural Development Center (RDC) and Horticulture Farm, Coastal Plain Experiment Station, Tifton, Georgia. The three most common fungi wereCoprinus plicatilis, Cyathus olla, andPanaeolina foenisecii. At the former site, residue management practices were established for evaluating crop production and at the Horticulture Farm different crops were grown with conservation tillage employing a Low Input Sustainable Vegetable Production system. Tillage treatments at the RDC were no-till, row-till, ridge-plant, and moldboard-plowing. Residue management of triticale included burning or cutting the stubble at a height of 20 or 60 cm at harvest. At the Horticulture Farm, seven winter cover crops were compared to a fallow control. No significant differences were shown between observations of fungal species and individual treatments at the Horticulture Farm during 1989 and 1990. However, there were treatment differences for observed fungi at the RDC farm on specific dates for both years. Furthermore, no individual treatment(s) during the investigation increased observation rates of specific fungal species. Non-burned debris treatments showed consistently higher populations and diversity of fungi than burn debris plots.

Insecticide resistance management of permethrin and acephate against the cowpea curculio, Chalcodermus aeneus Boheman (Coleoptera: Curculionidae), a pest of the southern pea, Vigna unguiculata (L.) Walp.

To evaluate strategies for management of potential resistance of the cowpea curculio, Chalcodermus aeneus Boheman, to sprayer‐applied permethrin and acephate, five management regimes were evaluated on early, midseason and late sequential plantings of southern peas, Vigna unguiculata (L.) Walp. during 1991–1993. Management regimes were: (1) consecutive permethrin (0.11 kg a.i./ha early‐midseason‐late); (2) consecutive acephate (1.1 kg a.i.ha early‐midseason‐late); (3) consecutive mixture (0.055kg a.i./ha permethrin and 0.55kg a.i./ha acephate early‐midseason‐late); (4) alternation (0.11 kg a.i./ha permethrin early and 1.1 kg a.i./ha acephate midseason and late plantings); and (5) an untreated check early, midseason and late. The effect of management regime on the toxicities (LC50) of permethrin and acephate was determined by topical application to next generation adult cowpea curculios reared from infested southern pea pods harvested from untreated plants in the management fields. In the field, infestation...