Location: Stored Product Insect and Engineering Research
Project Number: 3020-43000-034-058-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2025
End Date: Jul 31, 2026
Objective:
The project to be initiated in FY2025 will assess the feasibility of heat treatments for stored grains and seeds for khapra beetle by 1) assessing mortality in various commodities of interest, 2) assessing behavioral reaction to heat treatments that may affect efficacy, 3) validating treatments at industrial scale in prospective food facilities, including facilities that apply International Standards for Phytosanitary Measures (ISPM 15) treatments, 4) assess impacts on commodities from the heat treatment, and 2) comparing using surrogate species Trogoderma species, such as the warehouse beetle, Trogoderma variabile Ballion and the larger cabinet beetle, Trogoderma inclusum LeConte to validate assays and reach general conclusions about the genus when appropriate.
Approach:
The research project proposed here would support a cooperative effort involving personnel from USDA-APHIS, USDA-ARS, Kansas State University, and the University of Thessaly in Greece (through a sub-agreement with USDA ARS). Funding would support a Master’s Student stationed at Kansas State University and having access to research at the USDA-ARS Stored Product Insect and Engineering Research unit nearby in Manhattan, Kansas. This unit currently houses colonies of surrogate Trogoderma species, such as T. variabile and T. inclusum, which can be used immediately to validate experimental methodology before application to T. granarium. There is currently an application pending to initiate a T. granarium colony at this facility, and two of the cooperators on this project already have colonies of T. granarium Funds will be needed for trips to synergize research. It will also be needed for research materials including rearing supplies, commodities for testing, temperature probes, and heating blocks.
The research follows largely from previously published assessments of T. granarium susceptibility to heat and the currently adopted Australian standards for heat treatments (DAFF, 2023). The expertise of the collaborative team will allow application of their knowledge of commodity treatment research to the more specific objectives of the project.
Assessment of mortality in colony populations in environmental chambers. The first experimental element will be the validation of heat treatments in situ within commodities in small scale preparations within environmental chambers. We will aim to collect data for at least 4 different common commodities. Because of the nature of recent industry requests, we will prioritize watermelon seeds (Citrullus lanatus). Other commodities targeted will include corn seed (Zea mays), wheat berries (Triticum aestivum), and lentils (Vicia lens). All materials will be purchased from organic sources where there has been no prior treatment. Work on this aspect of the technical approach will be performed at one or more of the T. granarium colonies maintained by the cooperating laboratories.
The experimental approach will require manipulation of colonies to provide insects of various stages to test treatments. While previous work on this topic demonstrates that diapausing larvae should be most tolerant to heat stress (Wilches et al, 2019) the research was based upon rearing T. granarium on pulverized diet. Furthermore, there are different mechanisms of triggering diapause in T. granarium, based upon different colony conditions. These mechanisms include both cold exposure and limiting food resources. Because our objective will be to measure mortality directly in commodities we will take four approaches to generate colonies within these commodities that will provide a range of life cycle.
Rearing is generally performed in one-liter jars containing pulverized dogfood, mixed with wheat germ and covered with dried oats (see Domingue et al., 2023). Colonies are typically started with populations of 50 to 100 adults, with hundreds to thousands of mixed stage beetles present within two to three months. If colony jars are left undisturb
