Location: Crop Protection and Management Research2012 Annual Report
1a. Objectives (from AD-416):
1. Determine biological, ecological, and structural mechanisms driving stink bug population dynamics in the southeastern region of the United States. 1.A. Study the role of landscape make-up on populations of stink bugs. i. Confirm the sequence of habitats used by the stink bugs Nezara viridula and Euschistus servus in southern Georgia prior to colonization of cotton. ii. Estimate the parameters (net reproductive rate and interpatch movement) in our simple patch model that predicts stink bug colonization of cotton, and fit the model using data. iii. Using the parameterized model, predict the effects of landscape structure on the colonization of cotton by these stink bugs and test the model predictions. 1.B. Evaluate semi-field bioassays for the effects of relative crop quality on major crops used simultaneously by stink bugs. 1.C. Determine the role Bt technology and concomitant reduction in insecticide use and both Bt-targeted and non-targeted inter-specific insect pest interactions on pest invasiveness. 1.D. Assess survival of stink bug egg masses in soybean, cotton, and peanut. 1.E. Identify uncultivated host plant sources of stink bugs for cotton. 2. Develop and test bio-based management systems for stink bugs that are widely adaptable to various cropping systems in the southeastern region of the United States. 2.A. Evaluate non-chemical management practices that reduce populations of overwintering stink bugs such as through the use of controlled burns in woodland understory. 2.B. Determine the effectiveness of pheromone traps to capture stink bugs in a trap crop. 2.C. Determine the ability of a habitat of nectar-producing plants to provide food to natural populations of stink bug parasitoids. 2.D. Determine the effectiveness of a multifunctional habitat to serve as a trap crop for stink bugs and a site for conservation and feeding for bees and other insect pollinators and natural enemies of stink bugs. 3. Assess the ability of various southeastern region winter crops (legumes and small grains) to host a diversity and abundance of beneficial and pest species, and to determine the impact that these insects have on crop protection and damage in continuous cropping systems. 3.A. Determine the host plant affinity of the strains of fall armyworm to winter grain species grown in the southeastern U.S. 3.B. Determine the relative benefit of grasses, legumes, and winter weeds as early season habitat for beneficial arthropods and their relay into later planted sorghum. 4. Using knowledge gleaned about insect enemies, evaluate the use of trained parasitoid wasps in detection of aflatoxin concentrations in peanuts at the peanut grading stage.
1b. Approach (from AD-416):
Map and ground-truth aerial photos and collect data on stink bug 5th instar density over time in corn, cotton, soybean and peanut in four landscapes to estimate parameters (habitat colonization and net reproductive rate) of an existing simple patch model and confirm sequence of host use for stink bugs. Conduct a study on stink bug longevity for Bt cotton, RR cotton, peanut and soybean using plant cages. Use data on relative longevity of stink bugs and data from previous studies on relative stink bug preference for crops to further parameterize the model. Conduct studies on competition between stink bugs and heliothines at the cotton boll and branch scales and on stink bug feeding and oviposition preference for heliothine damaged and undamaged cotton plants. Volatiles and plant tissue will be analyzed for herbivore anti-feedants. Stink bug eggs will be placed as sentinels in Bt cotton, RR cotton, peanut and soybean to obtain data on egg mortality. Occurrence and abundance of stink bugs will be assessed for uncultivated host plants of stink bugs adjacent to cotton fields. Data on density of overwintering populations of stink bugs will be collected in agricultural fields with managed low intensity burns under the woodland and in fields with no woodland burns. Data on density of a stink bugs will be collected in soybean trap crops with and without stink bug pheromone capture traps in agricultural farmscapes. Data will be collected on stink farmscapes with and without a habitat of nectar-producing plants. Data will be collected on stink bug density and damage to cotton in agricultural farmscapes with and without a multifunctional habitat with plant species for trapping stink bugs and other plants for providing resources to natural enemies of these pests. Data will be collected on density of specific sorghum pest and beneficial insects and predation and parasitism rates of pests in both the winter cover crops and subsequent summer crops. Volatiles from aflatoxin infested and uninfested peanuts will be collected and analyzed using gas chromatography mass spectrometry (GC-MS) and a strong volatile correlate to aflatoxin infested peanuts will be identified. Data on the ability of wasps to detect aflatoxin infested peanuts at the grading stage will be collected using the portable 'wasp hound'.
3. Progress Report:
The third year of a study of the effects of landscapes on stink bug populations in southern Georgia was conducted (Objective 1). All of the field data in the regional analysis and most of the data for parameterization of the model predicting stink bug populations in cotton have been collected. The stink bug populations were found not to originate from the woodland adjacent in four major crops grown in the region, regardless of the landscape. There were also competitive interactions between heliothine larvae and stink bugs that were species dependent. Stink bugs prefer to oviposit on undamaged cotton over cotton damaged by heliothine larvae, and preferences for these plants for feeding was dependent on the stink bug and heliothine species. The third year of a study of the effects of various legumes on pest and beneficial arthropod species in a sorghum for biofuel and cotton rotation system was conducted (Objective 3). Cahaba white vetch and lupine winter covers were found to increase the beneficial to pest ratios in the covers and this transferred into the subsequent cotton and sorghum crops compared to the other four legume species. Lupine covers were also found to increase both crop yields significantly more than the other legume winter covers. Wasps as biosensors were studied (Objective 4). Learning and reporting of three chemicals by the wasp species, Microplitis croceipes, is both chemical and concentration dependent and results were reported in the provisional patent (Docket # 0025.10). Additional experiments conducted with two other compounds, one of which is associated with strawberry rot from the fungus, Phytpphthora cactorum, have confirmed these results and will be added to the final patent due in August 2012. The second year of a study to determine the ability of a trap cropping system in peanut-cotton plots was conducted (Objective 2). The trap cropping system included a trap crop, soybean, a nectar-producing plant, buckwheat, and stink bug pheromone capture-kill traps. Stink bugs were much lower in cotton with the trap cropping system compared to cotton without this system. A laboratory study was conducted to determine the ability of two IGR (insect growth regulator) insecticides to kill southern green stink bugs and brown stink bugs (Objective 2). Both azadiractin (Neem) and novaluron (Diamond) effectively killed immature stink bugs as they tried to molt into the succeeding stage of maturation.
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