Gerald E. Brust

Seed-predators reduce broadleaf weed growth and competitive ability

Abstract Based on field observations that fewer broadleaf weeds were found in low-input no-tillage systems (LINTS), a series of greenhouse experiments was conducted to investigate the effect of weed seed-predators on the competitive ability of broadleaf weeds grown with grass weeds. Two major broadleaf weeds, which were found in LINTS, red root pigweed Amaranthus retroflexus and lambsquarters Chenopodium album, and two major grass weeds, large crabgrass Digatara sanguinales and fall panicum Panicum dichotoflorum were tested singularly and in pairs (always one broadleaf with one grass) in the study. These seed pairings were exposed to (1) seed-predators (carabids and field crickets found in LINTS) which were at different densities, (2) wheat straw residue, (3) seed-predators and residue, and (4) a control (no seed-predators or residue). Seed-predators reduced the plant relative yield (PRY) of broadleaf weeds to the same extent as the wheat residue. Seed-predators preferred to feed on the broadleaf seeds which reduced the broadleaf weeds competitive ability when grown with grasses. Decreasing seed-predators by 50% resulted in almost no change in broadleaf plant relative yields compared with the control (no seed-predators). The decrease in seedling PRY caused by seed-predators was still evident as the plants matured. There was a significant interaction between seed-predators and residue in reducing broadleaf PRY probably because of differing effects of each on plant growth.

Reflective and Black Mulch Increase Yield in Pumpkins Under Virus Disease Pressure

Abstract Experiments were conducted over a 4-yr period that examined the effect reflective, black, and no-mulch had on aphid populations, incidence of virus infected pumpkin plants, and yield of pumpkin. Three different planting dates and their effect on viral infection and yield were also investigated. The use of reflective mulches significantly reduced the number of alates landing in these rows compared with black- or no-mulch rows. The reduction in aphid numbers resulted in a reduction in the percent of plants infected with virus. Approximately 10 times more plants were infected with virus in the black and no-mulch plots than in the reflective mulch plots in mid- to late July. However, by the end of August, all treatments had near 100% of plants infected with virus. This delay in viral infection in reflective mulch plots resulted in a 45 and 120% increase in pumpkin yield compared with black mulch and no-mulch plots, respectively. First plantings always had greater yields than later plantings. The interaction between mulch type and planting time was significant. Reflective mulches increased yields overall, but significantly increased yields compared with black or no-mulch in second and third plantings. The use of reflective mulch combined with timely planting is a cost effective way of delaying virus problems and increasing pumpkin yields in midwestern United States.

Effects of insecticides applied to control cucumber beetles (Coleoptera: Chrysomelidae) on watermelon yields

Abstract Foliar insecticides applied to control the striped and spotted cucumber beetles, Acalymma vittatum (Fab.) and Diabrotica undecimpunctata howardi Barber, on watermelon, Citrullus lanatus, were of little or no value in three studies conducted in two locations over 2 years. However, an at-planting application of the systemic, soil insecticide carbofuran resulted in higher early yields, although the differences were not statistically significant in small plots. In 1991, large plots comparing carbofuran-treated watermelons with untreated watermelons in two commercial fields showed large and statistically significant increases in melon yield when carbofuran was applied, especially in early yield. Studies in 1992 and 1993 showed that the application of carbofuran at planting stimulated root and shoot growth after transplating and increased yields when compared with untreated plots, plots treated with methyl bromide, or another soil insecticide, terbufos. These studies suggest that carbofuran may be acting as a growth stimulant, as well as an insecticide.