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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED PEST MANAGEMENT FOR KEY PESTS OF PECAN AND PEACH

Location: Fruit and Nut Research

Title: Effects of entomopathogenic fungus species, and impact of fertilizers, on biological control of pecan weevil (Coleoptera: Curculionidae)

Authors
item Shapiro Ilan, David
item Gardner, Wayne -
item Wells, Lenny -
item Cottrell, Ted
item Behle, Robert
item Wood, Bruce

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 27, 2012
Publication Date: April 1, 2013
Citation: Shapiro Ilan, D.I., Gardner, W., Wells, L., Cottrell, T.E., Behle, R.W., Wood, B.W. 2013. Effects of entomopathogenic fungus species, and impact of fertilizers, on biological control of pecan weevil (Coleoptera: Curculionidae). Environmental Entomology. 42:253-261.

Interpretive Summary: The pecan weevil is a major pest of pecan. Prior research indicated potential to use beneficial insect-killing fungi to suppress this pest. The beneficial fungi kill pests but don't harm humans or the environment. In this study, we first compared the efficacy of two species of fungi, one is called Beauveria bassiana and the other is called Metarhizium brunneum. We measured their ability to cause kill pecan weevils. In a pecan orchard, we applied B. bassiana to the tree trunk (a method previously shown to be effective) and compared the treatment with M. brunneum applied to the ground or to the trunk. Results indicated B. bassiana to be superior to M. brunneum regardless of the method of application. Consequently, we explored the potential of applying B. bassiana for pecan weevil control further. Specifically, we determined the impact of different fertilizer regimes (as used by pecan growers) on the persistence of B. bassiana. B. bassiana was applied in a pecan orchard with following fertilizer treatments: chemical fertilizer (ammonium nitrate), crimson clover, poultry litter, clover plus poultry litter, and a no-fertilizer control. B. bassiana persistence up to 49 d in 2009 and 2010 was assessed. Overall, fertilizer treatments did not substantially impact B. bassiana persistence. We conclude that fertilizers applied under standard recommended practices for pecan will not substantially impact survival of B. bassiana when the fungus is applied for C. caryae suppression during weevil emergence. Additional research on interactions between entomopathogenic fungi and fertilizer amendments (or other soil management practices) is needed.

Technical Abstract: The pecan weevil, Curculio caryae (Horn), is a key pest of pecan. Prior research indicated potential to use Hypocreales fungi for suppression of C. caryae. In this study, we first compared the efficacy of two fungal spp. Beauveria bassiana (GHA strain) and Metarhizium brunneum (F52) in ability to cause C. caryae mortality.In a pecan orchard, we applied B. bassiana to the tree trunk (a method previously shown to be effective in C. caryae suppression) and compared the treatment with M. brunneum applied to the ground or to the trunk with or without soyscreen as UV protecting agent. Results indicated B. bassiana to be superior to M. brunneum regardless of the method of application. Consequently, we explored the potential of applying B. bassiana for C. caryae control further. Specifically, we determined the impact of different fertilizer regimes (as used by pecan growers) on the persistence of B. bassiana (GHA). B. bassiana was applied in a pecan orchard with following fertilizer treatments: chemical fertilizer (ammonium nitrate), crimson clover, poultry litter, clover plus poultry litter, and a no-fertilizer control. B. bassiana persistence up to 49 d in 2009 and 2010 was assessed by plating soil onto selective media and determining the number of colony forming units, and by baiting soil with a susceptible host Galleria mellonella. Overall, fertilizer treatments did not substantially impact B. bassiana persistence. We conclude that fertilizers applied under standard recommended practices for pecan will not substantially impact survival of B. bassiana when the fungus is applied for C. caryae suppression during weevil emergence.

Last Modified: 10/22/2014
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