Factors contributing to the economic impact of cotton fleahoppers, Pseudatomoscelis seriatus

Factors contributing to the economic impact of cotton fleahoppers, Pseudatomoscelis seriatus

Summary

Here two factors which may contribute to the economic impact of fleahoppers on cotton production in Texas are investigated. First, fleahopper pest management may be complicated by the existence of genetically-distinct fleahopper popoulations in Texas. Previously, it was found that fleahopper populations from Corpus Christi, TX, are genetically distinct from other fleahopper populations across the state. Genetic differentiation in the pest species can cause variability in response of the pest to management because each genotype may have distinct effects on host plant performance. The effects of fleahopper genotypes on cotton growth, development and yield will be contrasted using standardized cotton monitoring techniques, SQUAREMAN, COTMAN and PMAP. This field project is planned for Summer 2013. Second, fleahopper management may be confounded by an increased susceptibility of cotton plants damaged by fleahoppers to other pests. Although cotton can tolerate some fleahopper damage, damage may increase the availability of carbon and nitrogen in the plant tissues for subsequent herbivores. Increased susceptibility exacerbates the need to spray insecticide, and limit cotton’s ability to compensate for fleahopper herbivory. Understanding how fleahoppers may alter the availability of nutrients for other herbivores in cotton will assist IPM practitioners to anticipate pest populations in fleahopper infested fields. In 2012 a preliminary field study was completed to determine fleahopper effects on beet army worm feeding preference. Results suggest that fleahoppers reduce the susceptibility of cotton to Lepidopteran pests.

Objectives/Performance Targets

In 2012 we completed a preliminary study to determine if fleahopper herbivory altered the feeding behavior of Lepidopteran pests on cotton.

All other experiments are scheduled to begin April 2013.

Accomplishments/Milestones

In 2012 we completed a preliminary study to determine if fleahopper herbivory altered the feeding behavior of Lepidopteran pests on cotton.

At the Texas A&M field laboratory, twelve 10 feet x 10 feet field cages were erected in a conventionally managed cotton field. Cotton plants were transplanted into these cages, after being grown in laboratory grow rooms to the 4-6 leaf stage. When the transplants reached their second week of squareing the in the field, a randomized complete block design 2×2 factorial experiment begun. Treatments included: (1) Control (no insects), (2) Fleahopper Control (Caterpillars only), (4) Caterpillar Control (Fleahoppers only) and (4) plants invested first with fleahoppers, followed by caterpillars. Treatments were blocked by field cage, and so, the sample size for this experiment was 12. Plants assigned to be infested with fleahoppers had 2 adult fleahoppers caged to their terminal for 48 hours. Plants assigned to be infested with caterpillars had 10 neonate beet armyworm larvae added to their topmost fully expanded leaves. Caterpillars were added to the 4th treatment group after the fleahoppers were removed. We then tracked caterpillar retention on the plants over 7 days. We found evidence that previous fleahopper herbivory reduced the susceptibility of cotton to caterpillar herbivory. Plants previously infested with fleahoppers, hosted fewer caterpillars by the end of the experiment then plants that were free of fleahoppers. The effect was marginally significant.

Impacts and Contributions/Outcomes

Results of the preliminary experiment do not support our first hypothesis that cotton fleahopper herbivory may increase the availability of carbon and nitrogen in the plant tissues for subsequent herbivores, leading to an exacerbation of pest problems. Instead, fleahoppers may be inducing defenses in the plants that deter Lepidopteran herbivory, suggesting a potential benefit of moderate fleahopper herbivory for cotton production. The experiment previously described will be repeated 2013 and include additional measurements. Additional measurements will include: (1) identification and quantification of any induced defensive chemistry following fleahopper herbivory, (2) caterpillar feeding rates and (3) caterpillar developmental performance on both fleahopper free and infested cotton.

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