ARS | Publication request: Application of plant growth regulators mitigates chlorotic foliar injury by the black pecan aphid (Hemiptera: Aphididae)

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2010
Publication Date: August 16, 2010
Citation: Cottrell, T.E., Wood, B.W., Ni, X. 2010. Application of plant growth regulators mitigates chlorotic foliar injury by the black pecan aphid (Hemiptera: Aphididae). Pest Management Science. 66:1236-1242.

Interpretive Summary: Feeding damage by the black pecan aphid to pecan foliage is costly to growers. If left untreated, aphids cause leaf senescence and abscission which can affect the current year’s crop and next year's crop. The plant growth regulators chlorforfenuron (CPPU), gibberellic acid (GA3) and aminoethoxyvinylglycine (AVG) retard leaf senescence. These growth regulators (either individually or in various combinations) and a water-only control were applied to pecan foliage in the field twice in both 2006 and 2007. Treated foliage was used in leaf disc laboratory bioassays to assess aphid mortality and developmental period, and leaf disc senescence (i.e., percentage of leaf discs with chlorosis and percentage of leaf disc area with chlorosis). No difference in aphid mortality among treatments was ever detected but aphid development could be prolonged. Relative to the control treatment, foliage treated with certain plant growth regulator combinations had less chlorosis and decreased chlorosis severity. We conclude that certain plant growth regulators may be used to 1) prolong aphid development and increase their nymphal exposure period to natural enemies and 2) mitigate chlorotic leaf injury by the black pecan aphid through inhibition of aphid-elicited ethylene production in pecan leaves.

Technical Abstract: Chlorotic feeding injury by the black pecan aphid, Melanocallis caryaefoliae (Davis) (Hemiptera: Aphididae), to pecan (Carya illinoinensis [Wangenh.] K. Koch) foliage can result in leaf senescence and abscission. The plant growth regulators chlorforfenuron (CPPU), gibberellic acid (GA3) and aminoethoxyvinylglycine (AVG) retard leaf senescence. These growth regulators (either individually or in various combinations) and a water-only control were applied to pecan foliage in the field twice in both 2006 and 2007. Treated foliage was used in leaf disc laboratory bioassays to assess aphid mortality and developmental period, and leaf disc senescence (i.e., percentage of leaf discs with chlorosis and percentage of leaf disc area with chlorosis). No difference in aphid mortality among treatments was ever detected. Only the combination of CPPU + GA3 (both 2006 dates) and AVG + GA3 (one 2007 date) had a significant effect on prolonging aphid development. A significantly lower percentage of leaf discs treated with CPPU + GA3 (all dates) developed aphid-elicited chlorosis compared to the control and AVG treatments. Again, the CPPU + GA3 treatment always resulted in a significantly lower area of the leaf disc developing aphid-elicited chlorosis compared to the control and AVG treatments. We conclude that certain plant growth regulators may be used to 1) prolong aphid development and increase their nymphal exposure period to natural enemies and 2) mitigate chlorotic leaf injury by the black pecan aphid through inhibition of aphid-elicited ethylene production in pecan leaves.