Harsimran K. Gill

Effect of Organic Mulches on Soil Surface Insects and Other Arthropods

ABSTRACT Four different types of organic mulches were evaluated for their effects on soil surface insects and related arthropods. Field experiments were conducted in fall 2007 and 2008 near Citra, Florida. In both the years, five treatments were compared: cowpea (Vigna unguiculata (L.) Walp.) mulch, sunn hemp (Crotalaria juncea L.) mulch, sorghum-sudangrass (Sorghum bicolor Moench × S. sudanense ((Piper)] Stapf) mulch, pine bark nuggets, and unmulched control. Data were collected on insects and other arthropods using pitfall traps. Results indicate that organic mulches can affect a wide range of different insects. Diptera, dominated by Asyndetus spp. (Dolichopodidae), were most dense in pine bark plots in both years. Populations of small plant-feeding insects such as Aphididae, Thripidae, and Aleyrodidae were most dense in cowpea and unmulched control plots in one season. It is possible that these insects were affected by weed growth in cowpea and control plots. Ants, which tend or feed on small plant feeders, were fairly abundant in these plots as well, as were predatory beetles. Some groups, such as Collembola (mainly Isotomidae), spiders, and Orthoptera (Acrididae and Gryllidae) were unaffected by mulches.

Mulch as a Potential Management Strategy for Lesser Cornstalk Borer, Elasmopalpus lignosellus (Insecta: Lepidoptera: Pyralidae), in Bush Bean (Phaseolus vulgaris)

ABSTRACT Lesser cornstalk borer (LCB), Elasmopalpus lignosellus (Zeller), is a serious pest of bean (Phaseolus vulgaris L.) and many other crops. The effect of mulching as a management method for LCB was examined in 2 field experiments conducted in small plots (1 m2) at 2 different locations (experiments A and B) in Alachua Co., FL. Both experiments were conducted in the summer and repeated in the fall, 2007. The treatments were arranged in a randomized complete block design with 5 replications at both locations. In experiment A, treatments were bare ground, plots with mulch, and plots with weeds (original weed cover); while in experiment B, treatments were bare ground and mulched plots. The mulch was obtained from a crop of sunn hemp (Crotalaria juncea L.) planted at another location. Data were collected on bean plant mortality, plant growth parameters (fresh weight, height, and length including roots of surviving plants), and population levels of potential predators. LCB attack was less (P ≤ 0.10) in mulched plots compared with bare ground, considering a number of factors such as location and background of field, season, and amount of precipitation. Greater numbers of surviving plants were found in mulched plots compared with bare ground and weedy plots. In general, fresh weight, height, and total length of bean plants were greater in mulched plots compared with other plots. Treatments did not affect numbers of potential predators of LCB. Evidence suggests that LCB attack is reduced by mulches or weeds around host plants.

Nonfumigant alternatives to methyl bromide for management of nematodes, soil-borne disease, and weeds in production of snapdragon (Antirrhinum majus)

Two field experiments were conducted in north Florida to examine effects of solarization and reduced-risk pesticides on weeds, nematodes, soil-borne diseases, and yield of snapdragon (Antirrhinum majus). Five treatments were replicated five times in a randomized complete block design: fumigation with 80:20 methyl bromide:chloropicrin, solarization, solarization + Kodiak® (product with Bacillus subtilis), solarization + Biophos™ (product with dipotassium phosphonate and dipotassium phosphate), and non-treated control. Methyl bromide was generally superior to treatments involving solarization, which in turn were superior to the control, for improving flower yield and managing weeds, nematodes, and mortality due to plant disease. In the second year, solarization was more effective than methyl bromide in reducing plant mortality; however, surviving plants were larger and more productive following methyl bromide. In the second year, Biophos™ + solarization was as effective as methyl bromide in improving plant height, but not yield. However, integrating solarization with Biophos™ did not provide benefits over solarization alone in terms of flower yield. In some cases, solarization alone provided results similar to methyl bromide for managing weeds, nematodes, and plant disease mortality.

Effects of different organic mulches on the soil surface arthropod community and weeds in snapdragon

Cultural control practices, including the use of cover crops and mulches, are convenient non-chemical methods for managing some insect pests and weeds. Several different types of organic mulches were evaluated for their effects on soil surface arthropods, weeds, and mortality of snapdragon plants in the autumn of both 2007 and 2008 near Citra, Florida, USA. In both seasons, five treatments were compared: cowpea mulch, sunn hemp mulch, sorghum-sudangrass mulch, pine bark nuggets, and an unmulched control. Mulches were applied around snapdragon plants in small plots, and treatments arranged in a randomized complete block design with five replications. Arthropod groups sampled using pitfall and board traps varied in their responses to treatments. The numbers of Formicidae, Cicadellidae, Orthoptera, and small-bodied plant-feeders (aphids, whiteflies, and thrips) were higher in control or cowpea plots than several of the other mulch treatment plots, possibly because weed levels were higher in control and cowpea plots. Collembola, Diptera, Araneae, and Coleoptera did not differ among treatments in either season. Board traps were effective for assessing Gryllidae and some beetles in 2007, when both groups were more abundant in the control and cowpea mulch plots than in the pine bark nugget plots, but in 2008 catches were not affected by treatment. Predatory insects were not consistently affected by mulches. Buckeye caterpillars feeding on the plants were not affected by the treatments and caused 28% mortality to snapdragon plants in 2007 and 27% mortality in 2008.

Insect Diapause: A Review

Diapause is defined as a period of suspended development in insects and other invertebrates during unfavorable environmental conditions. Diapause is commonly confused with term “quiescence” as both are dormant development stages. Here this paper aimed to review the research work done on different aspects of diapause. Attempt was made to explain definitions of diapause, incidence, stages and termination of diapause, genetic control, factors affecting diapauses, including temperature, photoperiod, moisture and food, etc..

Diel Activity of Fauna in Different Habitats Sampled at the Autumnal Equinox

ABSTRACT Experiments were conducted to examine the diurnal responses and abundance of arthropods at the autumn equinox in 2010. Experiments were conducted in 3 different fields, each with a different plant species: sunn hemp (Crotalaria juncea L.), bahiagrass (Paspalum notatum Flugge), and sandbur grass (Cenchrus spp.) using a randomized complete block design. Data were collected on numbers of arthropods caught in pitfall traps and on sticky cards. The long-legged flies (Diptera: Dolichopodidae) and thrips (Thysanoptera) collected were consistently diurnal, while ants (Hymenoptera: Formicidae), springtails (Collembola: Entomobryidae), micro-Diptera and tumbling flower beetles (Coleoptera: Mordellidae) were diurnal in one experiment. Elateridae and Aphididae tended to be nocturnal taxa, but plant height had some effect as well because aphid numbers were significantly higher in tall (182.3 cm) sunn hemp than in short (88.1 cm) sunn hemp at night time only. Cicadellidae were active during both day and night time and showed different levels of activity in pitfall traps and on sticky cards. Pitfall traps were found to be very effective for sampling insect taxa including Formicidae, Elateridae, and Collembola, while micro-Diptera, thrips, aphids, and Mordellidae were commonly caught on sticky cards. Cicadellidae and Dolichopodidae were commonly recovered in pitfall traps and on sticky cards.