2009 Annual Report
1a.Objectives (from AD-416)
To study, through both laboratory and field investigation, the physiology, biochemistry, biology, ecology, and control plant bugs on various host crops in the arid southwestern USA with the goal of developing environmentally sound and sustainable pest management strategies.
1b.Approach (from AD-416)
Laboratory studies will focus on elucidating the feeding physiology and biochemistry of plant bugs feeding on cotton and other hosts. Specific biochemical pathways will be determined and evaluated and molecular methods will be used to identify potential genetic based methods for disrupting these pathways (e.g. RNAi). The life history of plant bugs on new industrial crops will be quantified under controlled conditions. The potential impact of plant bugs on yield and quality of new industrial crops will be investigated in the greenhouse and field using inclusion cages and field manipulation of plant bug populations. Documents SCA with U of AZ.
Development and survival of L. hesperus was examined on lesquerella, guayule and alfalfa at 27C. Nymphal development times were similar on alfalfa, a common host, and lesquerella (ca. 11 days) but slightly longer on guayule (ca. 12 days). Resulting adult females were largest on lesquerella and smallest on guayule. Male size was similar on alfalfa and lesquerella and smaller on guayule. Survivorship was similar on all host plants and averaged between 73-85%.
Data were analyzed to determine when the last effective spray should be made to control Lygus in cotton. These data represent two planting dates, two dates of irrigation termination, three maturity classes and three nominal termination timings for Lgyus control relative to an untreated control. In general, earlier planted cotton was subjected to less risk and damage from Lygus, and smaller returns from Lygus controls than later plantings. Similarly, short-season varieties benefited the least in the extension of Lygus chemical controls later in the season. Conversely, long-season varieties, particularly those planted late, were subject to major risks of loss to Lygus and greater net returns on later terminations of chemical controls. In general irrigations extended beyond cut-out led to conditions requiring later Lygus control terminations.
Replicated small and large plot evaluations of candidate Lygus control chemistry, including reduced-risk options have been extensively tested. Broad spectrum acephate continues to perform well but has the potential to cause secondary pest problems (mites and whiteflies). Two new, more selective insecticides, flonicamid and metaflumizone, have performed the best for Lygus control and also have little effect on natural enemies. Novaluron has failed to provide acceptable Lygus control and has been associated with secondary pest outbreaks and natural enemy destruction.
The 2nd yr of regional mapping and sampling of Lygus bugs in commercial grower fields and other habitats (alfalfa, guayule and weeds) has been complete. More than 50 cotton fields were sampled weekly for Lygus and associated natural enemies. These data are being used to fit complex statistical models of Lygus movement in the landscape and to identify source and sink crops and the sphere of their influence on infestation in cotton.
Preliminary studies are underway to identify physiological and biochemical pathways related to digestions and nutrient acquisition by Lygus bugs and then to identify genes associated with these processes that might become targets for gene disruption by interference RNA methods.
The ADODR monitored activities for the project by meetings, site visits, and emails with the cooperating scientist.