A novel discovery in the pecan weevil’s pupal cell may lead to a new control method for pecan diseases such as scab

Authors: Shapiro Ilan, David; MIZELL, III, RUSSELL - University Of Florida

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 3/4/2015
Publication Date: 4/1/2015
Citation: Shapiro Ilan, D.I., Mizell, Iii, R.F. 2015. A novel discovery in the pecan weevil’s pupal cell may lead to a new control method for pecan diseases such as scab. Pecan Grower. 26(2):10-17.

Interpretive Summary: Soil-dwelling insects have developed various mechanisms to defend against pathogens (disease causing agents) that also dwell in the soil. The pecan weevil spends two to three years in the soil inside an earthen cell (also called its pupal cell or soil cell). To facilitate weevil survival during that long period, we hypothesized that the soil cell may possess antimicrobial properties. In a laboratory study, we tested the hypothesis using the white muscardine fungus (Beauveria bassiana) as a model. The white muscardine fungus is commonly found in soil of pecan orchards, and is a natural enemy of pecan weevil. We compared survival of fungus spores when exposed to soil from the pecan weevil pupal cell versus those surviving when exposed to regular field soil. Soil from the weevil’s pupal cell was toxic to the fungus (Shapiro-Ilan and Mizell, 2015). Therefore, we contend that the antibiotic factors responsible for suppressing the white muscardine fungus may also be toxic to various other fungi including pecan scab and other diseases. We discovered a unique bacterial strain associated with the weevil’s soil cell, and posit this bacterium or its associated by-products to be the causal antibiotic agent. Additional research is underway to expand this research and explore new opportunities for disease and pest control.

Technical Abstract: Soil-dwelling insects have developed various mechanisms to defend against pathogens (disease causing agents) that also dwell in the soil. The pecan weevil, Curculio caryae, spends two to three years in the soil inside an earthen cell (also called its pupal cell or soil cell). To facilitate weevil survival during that long period, we hypothesized that the soil cell may possess antimicrobial properties. In a laboratory study, we tested the hypothesis using Beauveria bassiana as a model. B. bassiana is commonly found in soil of pecan orchards, and is a natural enemy of C. caryae. We compared survival of fungus spores when exposed to soil from the C. caryae pupal cell versus those surviving when exposed to regular field soil. Soil from the weevil’s pupal cell was toxic to the fungus (Shapiro-Ilan and Mizell, 2015). Therefore, we contend that the antibiotic factors responsible for suppressing the B. bassiana may also be toxic to various other fungi including pecan scab, Fusicladium effusum, and other diseases. We discovered a unique bacterial strain associated with the weevil’s soil cell, and posit this bacterium or its associated by-products to be the causal antibiotic agent. Additional research is underway to expand this research and explore new opportunities for disease and pest control.