Strip Cropping: A Potential IPM Tool for Reducing Whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) Infestations in Cassava

Insect pests and diseases are a major limiting factor to cassava production in Africa. The cassava mosaic virus disease (CMVD), caused by cassava mosaic geminiviruses (CMGs) (Geminiviridae: Begomovirus) and transmitted by whitefly, Bemisia tabaci Gennadius, threatens the production of the crop in Africa, causing an estimated annual yield loss of over 1.5 billion US dollars. A 6-month field experiments were conducted to explore the potential of using strip cropping to reduce whitefly infestations in cassava, Manihot esculenta Crantz (Euphorbiaceae). Five rows each of cassava, Jatropha and cotton were grown around a 10-row (1 m row width) × 25 m cassava plots in a randomized complete block design. At weekly intervals, the levels of whiteflies infestations (number of eggs, nymphs and adults) per plot were determined. A significantly lower numbers of immature (egg and nymph) and adult Bemisia tabaci were found in cassava plots surrounded on all sides by five rows of both cotton and Jatropha curcas, clearly demonstrating the potential of strip cropping as a management option for the suppression of Bemisia tabaci populations

Effect of Tillage and Planting Date on Seasonal Abundance and Diversity of Predacious Ground Beetles in Cotton

A 2-year field study was conducted in the southern High Plains region of Texas to evaluate the effect of tillage system and cotton planting date window on seasonal abundance and activity patterns of predacious ground beetles. The experiment was deployed in a split-plot randomized block design with tillage as the main-plot factor and planting date as the subplot factor. There were two levels for each factor. The two tillage systems were conservation tillage (30% or more of the soil surface is covered with crop residue) and conventional tillage. The two cotton planting date window treatments were early May (normal planting) and early June (late planting). Five prevailing predacious ground beetles, Cicindela sexguttata F., Calosoma scrutator Drees, Pasimachus spp., Pterostichus spp., and Megacephala Carolina L. (Coleoptera: Carabidae), were monitored using pitfall traps at 2-week intervals from June 2002 to October 2003. The highest total number of ground beetles (6/trap) was observed on 9 July 2003. Cicindela sexguttata was the dominant ground dwelling predacious beetle among the five species. A significant difference between the two tillage systems was observed in the abundances of Pterostichus spp. and C. sexguttata. In 2002. significantly more Pterostichus spp. were recorded from conventional plots (0.27/trap) than were recorded from conservation tillage plots (0.05/trap). Significantly more C. sexguttata were recorded in 2003 from conservation plots (3.77/trap) than were recorded from conventional tillage plots (1.04/trap). There was a significant interaction between year and tillage treatments. However, there was no significant difference in the abundances of M. Carolina and Pasimachus spp. between the two tillage practices in either of the two years. M. Carolina numbers were significantly higher in late-planted cotton compared with those observed in normal-planted cotton. However, planting date window had no significant influence on the activity patterns of the other species. Ground beetle species abundance, diversity, and species richness were significantly higher in conservation tillage plots. This suggests that field conditions arising from the practice of conservation tillage may support higher predacious ground beetle activity than might be observed under field conditions arising from conventional tillage practices

Characterization of the Earwig, Doru lineare, as a Predator of Larvae of the Fall Armyworm, Spodoptera frugiperda: A Functional Response Study

Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) is considered as the most important pest of maize in almost all tropical America. In Argentina, the earwig Doru lineare Eschscholtz (Dermaptera: Forficulidae) has been observed preying on S. frugiperda egg masses in corn crops, but no data about its potential role as a biocontrol agent of this pest have been provided. The predation efficiency of D. lineare on newly emerged S. frugiperda larva was evaluated through a laboratory functional response study. D. lineare showed type II functional response to S. frugiperda larval density, and disc equation estimations of searching efficiency and handling time were (a) = 0.374 and (t) = 182.9 s, respectively. Earwig satiation occurred at 39.4 S. frugiperda larvae

Thermal Variability Increases the Impact of Autumnal Warming and Drives Metabolic Depression in an Overwintering Butterfly

Increases in thermal variability elevate metabolic rate due to Jensen's inequality, and increased metabolic rate decreases the fitness of dormant ectotherms by increasing consumption of stored energy reserves. Theory predicts that ectotherms should respond to increased thermal variability by lowering the thermal sensitivity of metabolism, which will reduce the impact of the warm portion of thermal variability. We examined the thermal sensitivity of metabolic rate of overwintering Erynnis propertius (Lepidoptera: Hesperiidae) larvae from a stable or variable environment reared in the laboratory in a reciprocal common garden design, and used these data to model energy use during the winters of 1973–2010 using meteorological data to predict the energetic outcomes of metabolic compensation and phenological shifts. Larvae that experienced variable temperatures had decreased thermal sensitivity of metabolic rate, and were larger than those reared at stable temperatures, which could partially compensate for the increased energetic demands. Even with depressed thermal sensitivity, the variable environment was more energy-demanding than the stable, with the majority of this demand occurring in autumn. Autumn phenology changes thus had disproportionate influence on energy consumption in variable environments, and variable-reared larvae were most susceptible to overwinter energy drain. Therefore the energetic impacts of the timing of entry into winter dormancy will strongly influence ectotherm fitness in northern temperate environments. We conclude that thermal variability drives the expression of metabolic suppression in this species; that phenological shifts will have a greater impact on ectotherms in variable thermal environments; and that E. propertius will be more sensitive to shifts in phenology in autumn than in spring. This suggests that increases in overwinter thermal variability and/or extended, warm autumns, will negatively impact all non-feeding dormant ectotherms which lack the ability to suppress their overwinter metabolic thermal sensitivity

Evaluation of winter wheat as a potential relay crop for enhancing biological control of cotton aphids in seedling cotton

A 2-year study was conducted to evaluate the role of winter wheat, Triticum aestivum L., as a potential relay crop to conserve arthropod natural enemies and suppress cotton aphids, Aphis gossypii Glover, in seedling cotton. The results suggested that the natural enemies that moved from the adjacent wheat fields to cotton fields with the maturity and harvest of wheat could keep the cotton aphid population at the edges (0-4 m) of cotton fields under the action threshold of 100 aphidS/m(2). Data also suggested that the wheat strip served as a reservoir to conserve arthropod predators and "relayed" its predators to cotton when wheat matured and senesced

Quantification of diapausing fourth generation and suicidal fifth generation cotton bollworm, Helicoverpa armigera, in cotton and corn in northern China

Cotton bollworm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), is a major pest of cotton and corn crops in northern China. A phenological differentiation between fourth generation cotton bollworms from cotton and those from corn fields was observed in northern China during 1999-2000. The proportion of pupation in late fall was marginally higher in cotton fields compared to that in corn fields; however, the proportions of fall emergence of moths from cotton fields were significantly higher than those from corn fields. The proportion of spring emergence of moths was also significantly higher for larvae collected from cotton (28.0%) than from corn (14.5%). The overwintering duration of females was significantly shorter than that of males in both crops. Moreover, the overwintering duration of bollworm populations from cotton was significantly longer than that from corn. The early spring population of H. armigera came from both cotton and corn fields, but the spring emergence of moths from larvae collected from cotton took about 5 days longer to reach 100% emergence compared to that from corn