Location: Stored Product Insect and Engineering Research
Project Number: 3020-43000-034-017-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 15, 2021
End Date: Aug 31, 2024
Objective:
Many species of stored product insects feed on similar foods and are attracted to moldy grain, and thus, may use a suite of microbial cues to navigate throughout the landscape. Ingesting mycotxins (toxins produced by fungi) may result in severe health consequences to humans, and is estimated to be a problem for most markets in developing countries. Anecdotally, food facility managers have reported that grain infested with insects tends to spoil from fungal growth quickly, and on the other hand, areas with fungal growth often attract more insects. Because some post-harvest insects disperse quite far, insects may act as vectors for microbes and their mycotoxins. Knowledge about how these pests interact may highlight the health consequences of insect infestation, and may also yield new attractive volatiles for use in novel behaviorally-based, semniochemical-mediated management tactics such as attract-and-kill and push-pull to manipulate pest populations.
Thus, the overarching objective in this work is to assess the behavioral and chemical ecology insect-microbe interactions in the postharvest environment between two important stored product insects in two families Ptinidae (e.g. Lasioderma serricorne) and Curculionidae (e.g. Sitophilus oryzae) and two common genera of storage molds (Aspergillus and Fusarium spp.). Specific objectives are 1) to examine how the insect and microbial communities interact to promote colonization, population growth, and degradation of grain quality, 2) develop a robust dataset on whether post-harvest insects pose a threat to food safety in food facilities by vectoring mycotoxins, and 3) characterize which microbial volatiles are attractive to Lasioderma serricorne and Sitophilus spp.
Approach:
Obj. 1. To evaluate whether prior colonization by fungi increases life history measures (progeny production, CFU, etc) for the species above. Fixed amounts of grain will be autoclaved, and standardized inocula of fungi (Aspergillus spp., Fusarium spp.) or no fungi (control) will be introduced. Treatments will include grain masses: with no insects or fungi, with insects only, with fungi only, or with both. Insect treatments will contain 25 males and females added to a batch of grain. Treatments will be incubated for 6 wks with total progeny counts, weight of fungal-damage to grain (near-infrared spectroscopy), and insect-damaged kernels (IDK) all recorded as well as sequencing of microbial community after plating. The microclimate in grain masses will be measured, including temperature and RH to determine if it is modified in ways that benefit each pest.
Obj. 2. Field specimens of Lasioderma serricorne and Sitophilus spp. will be collected from around the country. Each adult will be washed to extract surface spores, and plated out on standard agar growth media. Morphotypes will be sequenced. In addition, specimens will be allowed to walk on agar dishes and their tracks will digitized as well as sequenced.
Obj. 3. Headspace volatiles will be obtained using push headspace collection from moldy grain incubated or obtained from the field, and will be characterized by adding an internal standard (tetradecane) then analyzed with gas chromatography coupled with mass spectrometry (GC-MS) using standard methodology. Volatile bouquets will be screened for the greatest antennal response by the species above using GC-EAD. Using the most promising volatiles above, commercially available compounds will be assayed in a wind tunnel to determine attraction, and arrestment will be assessed by tracking movement patterns when exposed to volatiles. For the wind tunnel, compounds will be compared to hexane controls and placed upwind of a release arena. For the arrestment assay, a compound will be placed on one side, while the other side will be a hexane control.
