Chlorpyrifos-resistant greenbugs found in Texas
click image to zoom Another study was conducted from 1994 - 1996 to identify best mixtures of insecticides that were available at that time and how to use insecticide mixtures for resistant greenbugs (GB) after a failure of chlorpyrifos, or as the 1st application if resistant greenbugs are expected to be in the field (Archer et al. 1999. Journal Economic Entomology 92(4): 794-803). The insecticides used in this study were chlorpyrifos, carbofuran, and malathion. Since we do not have carbofuran now, the results from the chlorpyrifos/malathion mixtures may help us in managing our resistant greenbugs. The rates for the insecticides were chlorpyrifos (4E) at 1 pt/acre and malathion (5E) at 12.8 fl. oz/acre. In summary the findings showed:
• The mixture of chlorpyrifos/malathion gave good initial control (86%) but tapered off by 10 days after treatment and numbers were increasing again.
• A second application of the mixture 11 daysafter the initial application provided good control of the remaining GBs (94% to 83%) for another 10 days.
• After chlorpyrifos had already been applied
• The application of the chlorpyrifos/malathion mixture did not provide good control of the remaining GBs for 10 days after spraying
• A second application of the mixture 11 days after the mixture application did provide good control (94% to 82%) for 10 days
These data provide some evidence that chlorpyrifos/malathion mixtures may be used to improve control of fields if the greenbug infestation has some resistant greenbugs.
Unfortunately, there is no available information on how well the newer products, such as Cobalt and Stallion, will control resistant greenbugs and we do not have any good solutions when there is a control failure with chlorpyrifos. Our options are very limited, but we do know that applying multiple applications of chlorpyrifos will not control the resistant greenbugs.