Grain Inoculated with Different Growth Stages of the Fungus, Aspergillus flavus, Affect the Close-Range Foraging Behavior by a Primary Stored Product Pest, Sitophilus oryzae (Coleoptera: Curculionidae)

Abstract

Although some research has investigated the interactions among stored product insects and microbes, little research has examined how specific fungal life stages affect volatile emissions in grain and linked it to the behavior of Sitophilus oryzae, the cosmopolitan rice weevil. Thus, our goals were to 1) isolate, culture, and identify two fungal life stages of Aspergillus flavus, 2) characterize the volatile emissions from grain inoculated by each fungal morphotype, and 3) understand how microbially-produced volatile organic compounds (MVOCs) from each fungal morphotype affect foraging, attraction, and preference by S. oryzae. We hypothesized that the headspace blends would be unique among our treatments and that this will lead to preferential mobility by S. oryzae among treatments. Using headspace collection coupled with GC-MS, we found the sexual life stage of A. flavus had the most unique emissions of MVOCs compared to the other semiochemical treatments. This translated to a higher interaction with kernels containing grain with the A. flavus sexual life stage, as well as a higher cumulative time spent in those zones by S. oryzae in a video-tracking assay in comparison to the asexual life stage. While fungal cues were important for foraging at close-range, the release-recapture assay indicated that grain volatiles were more important for attraction at longer distances. There was no significant preference between grain and MVOCs in a four-way olfactometer. Overall, this study enhances our understanding of how fungal cues affect the close and longer range foraging ecology of a primarily stored product insect.

Attraction, mobility, and preference by Lasioderma serricorne (Coleoptera: Ptinidae) to microbially-mediated volatile emissions by two species of fungi in stored grain

“…Additionally, it is possible that while some of the treatments have attractant or arresting properties as individual bouquets, complex blends admixing in the headspace of the release chamber may result in no preference among each other. Prior work has confirmed that volatiles are able to quickly and adequately diffuse by Brownian motion over the allotted trial period in the assay 10 . Thus, performance of this assay in the biosafety cabinet did not prevent volatiles from reaching test subjects, and was a valid test of the odor treatments.…”

“…At close-range, L. serricorne used volatiles from Aspergillus flavus -inoculated grain for foraging decisions, and this was reflected in some differentiation in the volatile composition from the A. flavus treatment compared to the other treatments. Similarly, another stored product pest, S. oryzae , oriented to MVOCs from A. flavus -inoculated grain at close-ranges, but preferred to use only grain volatiles at a distance 10 . Interestingly, our results also showed that grain without microbes (i.e.…”

“…Van Winkle et al 9 found that tempering grain to different moisture levels and incubating for 9–28 days at 30 °C significantly changed the blend of volatiles and microbial communities, which showed attraction at moderate levels to Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), but not the secondary pest, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Ponce et al 10 found that MVOCs affected the close-range foraging of an internal-infesting pest, S. oryzae , after inoculation of grain with different life stages (e.g., sexual vs. asexual) of Aspergillus flavus . An important knowledge gap that needs to be addressed is how and whether fungal MVOCs impact behavior of external-infesting stored product pests.…”

Weapons against Themselves: Identification and Use of Quorum Sensing Volatile Molecules to Control Plant Pathogenic Fungi Growth

“…However, all these compounds have been detected to be emitted by other fungal species [38][39][40][41]. Interestingly, 2-phenylethanol has been shown to have antifungal properties against Penicillium species [41].…”

Sitophilus zeamais (Motschulsky): the primary obstacles in the maize quality and quantity

“…High humidity and suitable provides ideal conditions for fungal proliferation and mycotoxin accumulation. To reduce the path from mycotoxins in the food and feed chain, it is necessary for dealing with insect pests and fungal contamination [61][62][63][64].…”