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Title: Factors affecting damage to pecan foliage by the black pecan aphid

Author
item Cottrell, Ted
item Wood, Bruce
item CONNER, PATRICK - UNIV OF GA

Submitted to: Southeastern Pecan Growers Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/9/2008
Publication Date: 8/15/2008
Citation: Cottrell, T.E., Conner, P., Wood, B.W. 2008. Factors affecting damage to pecan foliage by the black pecan aphid. Proceedings of Southeastern Pecan Growers Association. 101:74:85.

Interpretive Summary: Aphids feeding on pecan foliage can cause great economic harm leading to a reduction of leaf chlorophyll and leaf area, a decrease in leaf net photosynthesis, depletion of carbohydrate reserves in stem tissue and defoliation. Aphids also affect pecan yield, quality and return bloom. In this study, we found that adult aphids preferentially select foliage previously damaged by other aphids and that aphid nymphs deprived of feeding on aphid-damaged foliage had higher mortality and slower development. In addition, there was genetic variability in the response of the pecan host in its ability to resist black pecan aphid damage to foliage. We also demonstrated that timely usage of plant growth regulating chemicals can greatly suppress black pecan aphid development ultimately leading to reduced damage to pecan foliage and introduce the novel concept of using plant growth regulators to protect pecan orchards against the black pecan aphid attacking pecan.

Technical Abstract: Pecan foliage is attacked by three aphid species (black pecan aphid, Melanocallis caryaefoliae [Davis], blackmargined aphid, Monellia caryella [Fitch], and yellow pecan aphid, Monelliopsis pecanis Bissell) across the southeastern United States. Aphid feeding results in a reduction of leaf chlorophyll and leaf area, a decrease in leaf net photosynthesis, depletion of carbohydrate reserves in stem tissue and defoliation. Additionally, they also affect pecan yield, quality and return bloom. Of the three aphid species attacking pecan foliage, it is the black pecan aphid that causes the most serious damage and is the hardest to control. In this study, we explored factors affecting damage to pecan foliage by the black pecan aphid (i.e., adult feeding site selection, impact of leaf chlorosis on nymphal development, seasonal impact of cultivar on aphid performance) and a possible method to minimize that damage (i.e., impact of plant growth regulators on black pecan aphid performance). We found that adult aphids preferentially selected foliage previously damaged by other aphids and that nymphs deprived of remaining on aphid-damaged foliage had higher mortality and slower development. In addition, there was genetic variability in the response of the pecan host in its ability to resist black pecan aphid via resistance to induction and acceleration of physiological leaf aging by the parasitic black pecan aphid. We also demonstrated that timely usage of plant growth regulating chemicals can greatly suppress black pecan aphid development ultimately leading to reduced ability to damage pecan foliage through reduced reproduction and population growth. We therefore introduce the novel concept of using plant growth regulators to protect pecan orchards against the black pecan aphid.