Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2008
Publication Date: June 1, 2008
Citation: Lopez, J., Lan, Y., Latheef, M.A., Hoffmann, W.C., Fritz, B.K., Martin, D.E. 2008. Laboratory evaluation of novaluron for toxicity to nymphal instars of field collected southern green stink bug on cotton. Southwestern Entomologist. 33:119-127. Interpretive Summary: Southern green stink bugs have become a greater pest problem on cotton because of the use of genetically modified plants that incorporate insecticidal properties and decreased use of insecticides following successful boll weevil eradication. Control options for southern green stink bugs are currently limited to insecticides and there is a need for enhanced insecticide and application technology efficacy. Novaluron is a very selective insecticide that regulates growth by interfering with the molting process. Laboratory evaluations of novaluron showed that it is most toxic to the second instars as compared to the third and fourth instar nymphs and that increased plant coverage increases efficacy. This means that applications of novaluron need to be made when southern green stink bugs are small and via application with higher droplet size and density for maximum efficacy. Proper timing and spray droplet size of selective insecticide applications will be useful in integrated pest management of Southern green stink bugs.
Technical Abstract: The efficacy of novaluron (Diamond [TM] 0.83 EC) on cotton against nymphs of different instars of field collected southern green stink bug (SGSB), Nezara viridula (L.), was investigated in a spray table using two nozzles, 650033 and 8002E. The nozzles delivered spray rates of 18.7 and 46.7 L/ha, respectively, of total water based spray. Novaluron was applied at 0.0218, 0.0436 and 0.0654 kg active ingredient (AI) rates per ha. The 8002E nozzle produced significantly larger droplets, increased droplet density and increased spray coverage compared to 650033. Regardless of dosage and spray rate, the age of nymphal instars significantly influenced mortality. Mortality of small nymphs (2nd instars) was significantly greater than that of either 3rd or 4th instar nymphs. When novaluron was applied at 0.0654 and 0.0872 kg AI per ha with or without crop oil concentrate, the deposit from the 8002E nozzle significantly increased mortality of 3rd instar nymphs; however, neither dosage nor addition of crop oil concentrate increased mortality of 3rd instar nymphs. Novaluron did not cause a high level of mortality of 4th instar nymphs. This study suggests that application of novaluron should be directed at 2nd instar nymphs to maximize efficacy for control of SGSB on cotton and that applications that produce deposits on plants with increased droplet size and density may increase efficacy.