INSECTICIDE USE RULES FOR GREEN PLANT BUG BASED ON FEEDING PREFERENCES AND ECONOMIC THRESHHOLDS
Michael Brewer, Texas AgriLife Extension Service
Investigator: Michael Brewer, Corpus Christi Research & Extension Center.
Co-Investigator: Megha Parajulee, Lubbock Research & Extension Center.
Collaborator: Charles Suh, Areawide Pest Management Unit, USDA ARS, College Station.
We conducted a second year field experiment in 2012 at Corpus Christi and Lubbock, TX to test whether plant water stress, insect seasonality, and plant sensitivity are interacting factors that result in damage differences attributable to cotton fleahopper feeding. Fleahopper populations were less sensitive to plant water stress and more sensitive to plant development stage, which may partly explain field to field differences experienced by growers. Although more abundant during bloom, square sensitivity to cotton fleahopper damage and early season opportunity to suppress the population are the primary main considerations in insecticide use. Plant/boll vigor in good soil moisture conditions likely benefits cotton in tolerating cotton fleahopper when cotton fleahoppers occur after squaring. Detection of fleahoppers during bloom in early planted cotton may serve as early warning of cotton fleahoppers in cotton planted later.
Cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae), can cause excessive loss of cotton squares, resulting in reduced yield and harvest delays. It is a key insect pest of cotton in Texas and Oklahoma. Damage (square loss) to individual fields can vary from none to extremely high even under similar population pressure. Understanding how these factors contribute to cotton fleahopper fluctuations may allow better estimation of cotton risk from cotton fleahopper damage. Our ultimate goal is to discern when in-season management (i.e., insecticides, irrigation) is most useful to reduce risk to cotton fleahopper damage.
We report here cotton fleahopper and harvest results from Corpus Christi in 2012 (revealing fleahopper/water stress relationship), and plant measurement results in Lubbock in 2011 (very similar in 2012 per data analysis, revealing plant vigor increases under irrigation, graphics in preparation).
Corpus Christi: Fleahoppers were detected late with good numbers first occurring June 1, corresponding to mid-bloom for a relatively early planting (42 days after planting) and early bloom for a later planting (31 days after planting). The early planting had much higher populations when fleahopper first appeared in the field, and sprays suppressed the population in the early planting. As in the previous year, water regime did not affect initial fleahopper densities. Two weeks later (June 14), cotton fleahopper populations increased as the later planting matured, and the sprays did not suppress this expanding population. Irrigation significantly increased yield, and the early planting had higher yields under irrigation. Yield reduction attributable to fleahopper was not detected; even though the early planting had higher fleahopper populations (including ones above the economic threshold of 15 fleahoppers per 100 plants in our area).
Lubbock: The total number of fruit set per plant increased with increasing irrigation, but fruit retention suffered only when irrigation was reduced (low irrigation and dryland) (data taken from a complete plant mapping on August 3, 2011). The irrigation level significantly influenced cotton fruit physiology, with larger and heavier bolls with harder carpel walls produced at high irrigation regimes compared to those at the low irrigation and dryland.