No abstract

Producers in the Mid-Atlantic region of the United States often use prophylactic pesticide sprays in their fields to increase wheat (Triticum aestivum L.) yields regardless of disease or insect pest levels. This study was carried out at two sites during each of two field seasons to evaluate th-e effects of pesticide applications (fungicides and insecticide) on insect abundance, beneficial arthropods, foliar damage and grain yield in winter wheat. Insecticide applications reduced densities of cereal leaf beetle (CLB) and CLB damage of flag leaves at the Queenstown and aphid at the Upper Marlboro study site compared to controls during 2009 and 2011 field seasons, respectively. However, insecticide application also reduced arthropod predators at Queenstown in 2009. Fungicide applications reduced leaf spot severity symptoms at Queenstown in 2009 and both sites in 2011. Grain yield was negatively correlated with the percentage of severely damaged flag leaves during the 2009 growing season when diseases and insects pressure was greatest. Nevertheless, yield increase associated with application of pesticides (fungicides) was observed only at one out of four siteÀyear combinations. Results from this study suggest that prophylactic sprays will not enhance wheat yields in the absence of high pest pressure.

Cover cropping has long been used as a method of reducing soil erosion, increasing soil quality, and suppressing weeds. However, the effects of cover crops in local farming systems are varied and can be affected by timing and method of termination. Field experiments were conducted at two sites in Maryland, USA during the 2013 and 2014 growing seasons to examine how varying the date and method of terminating a barley (Hordeum vulgare) cover crop affects the arthropod communities in succeeding no-till soybean (Glycine max). Experimental treatments included early-kill with pre-and post-emergent herbicides (EK), late-kill with pre-and post-emergent herbicides (LK), late-kill with a flail mower and pre-emergent herbicide (FM), and a fallow/bare-ground check with pre-and post-emergent herbicides (BG). Terminating barley late, just prior to soybean planting, resulted in significantly greater biomass accumulation in LK and FM than EK. However, method and timing of termination had no effect on the community of pest and beneficial arthropods in the soybean canopy. Results from this experiment suggest that terminating the cover crop early or late (just prior to crop planting) or using a mower or post-emergent herbicide will result in a similar community of arthropods within the soybean canopy.

Row spacing in agricultural systems can influence crop yield as well as pest and predator abundances. Soybean (Glycine max L. Merrill) growers in Maryland typically plant in narrow (∼19 cm), medium (∼38 cm), or wide (∼76 cm)-spaced rows, and there is a general lack of information on how these row-spacing schemes influence arthropod abundance and soybean yields. A study was conducted during two growing seasons to determine the effect of soybean row spacing and planting date (early and late) on soybean arthropods and yield. Despite a great deal of variation in arthropod responses to row spacing, and interactions between row spacing and study year, leaf-feeding herbivores were generally more abundant in narrow-spaced soybeans. All arthropod functional groups were more abundant, and yield was greater in early-planted soybeans relative to late-planted soybeans. Potential causes and implications of these finding are discussed.

No abstract