Integrating Biological Control into Pecan Weevil Management: A Sustainable Approach

2004 Annual Report for LS03-153

Project Type: Research and Education
Funds awarded in 2003: $217,500.00
Projected End Date: 12/31/2006
Region: Southern
State: Georgia
Principal Investigator:

Integrating Biological Control into Pecan Weevil Management: A Sustainable Approach


The overall goal of this project is to reduce reliance on chemical insecticides by incorporating biological control into a sustainable pest management program for pecan weevil. Specifically, we are investigating entomopathogenic (insect-killing) fungi for their potential to suppress pecan weevil populations. We are exploring methods to enhance the efficacy of the fungi by selecting superior strains, developing novel formulations, and determining the effects of certain soil amendments that may enhance fungal persistence. Thus, far we have identified virulent fungal strains to be utilized in further testing in field efficacy. Preliminary studies on soil amendments indicate potential for enhanced fungal activity. Novel formulations have been developed and caused greater field suppression of pecan weevil relative to the standard wettable powder formulation.

Objectives/Performance Targets

Project Objectives:
1. Enhance persistence of C. caryae control with B. bassiana by one or more of the following:
A. Selecting superior fungal strain for pecan weevil control.
B. Addition of soil amendments to improve B. bassiana persistence.
C. Developing improved formulations.
2. Determine the optimum area of B. bassiana application
3. Conduct feasibility and economic analyses to determine the potential of incorporating B.
bassiana into an integrated pest management system.
4. Extend the project findings to grower clientele.


Selecting superior fungal strains.
Seven strains of the entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, were screened in the laboratory for virulence to adult pecan weevils (these strains were selected based on results of prior screening Vs the larval stage of pecan weevil). Results indicated variation in virulence among the strains tested (Fig. 1). Based on high levels of virulence (ca. 70% mycosis in lab studies) and amenability to mass production the following strains are being considered in further studies: Metarhizium anisopliae strain MaLA7 and F52 (currently under commercial development), and the already commercially available “standard” GHA strain of B. bassiana (which is labeled for pecan weevil).

Addition of soil amendments to improve entomopathogenic fungal persistence and efficacy.
A graduate student was hired in the Department of Entomology, University of Georgia to address this objective (under the direction of Dr. Wayne Gardner, co-PI). An initial screening of diatomaceous earth as a possible soil amendment to enhance efficacy/persistence of B. bassiana and M. anisopliae (GHA and F52 strains, respectively) was conducted. Preliminary results indicate diatomaceous earth may have increased mortality and infection of pecan weevils when exposed to B. bassiana. However, further tests are required and underway to confirm the hypothesis. Additional amendments will also be tested in the laboratory and field.

Developing improved fungal formulations for control of pecan weevil under field conditions.
An oil based and UV-protecting formulation was developed by Dr. Bob Behle (USDA-ARS, Peoria, co-PI). These formulations may offer enhanced fungal spore persistence and thus enhance efficacy of pecan weevil control. Field trials conducted in 2004 tested the efficacy of the oil formulation (cultivated into the soil for further protection of fungal spores), the oil formulation + UV screen applied to the pecan tree trunk, and the standard formulation, wettable powder (WP). All treatments utilized the GHA fungal strain of B. bassiana and were compared to a non-treated control. The number of live and dead pecan weevils captured in each plot was analyzed. The oil formulation (cultivated into the soil) and the oil-UV screen formulation (applied to the trunk) caused greater pecan weevil mortality relative to the untreated control, whereas the standard wettable powder did not cause greater mortality than the control (Fig. 2). These results indicate that the new formulations are superior and promise to provide enhanced pecan weevil control. The field experiment will be repeated in the summer of 2005 with additional treatments addressing soil amendment effects.

Figure 1: Lab screening of fungal strains Vs adult pecan weevil.
Figure available upon request (could not upload here).

Figure 2: Field efficacy with different fungal formulations and treatments.
Figure available upon request (could not upload here).

Contact project investigator for hard copy to see figures referenced above.

Impacts and Contributions/Outcomes

Progress made on this SARE project was incorporated into a presentation at the Western Pecan Growers Conference, (March 2005, Las Cruces New Mexico), and mentioned in the following related publication.

Shapiro-Ilan, D.I., Cottrell, T., Gardner, W.A., and Wood, B.W. 2005. Biologically-Based Insecticides for Pecan Pest Management, Proceedings of the Western Pecan Conference, 2005. (in press).