Co-application of certain types of compounds to conventional antimicrobial drugs can enhance the efficacy of the drugs through a process termed chemosensitization. We show that kojic acid (KA), a natural pyrone, is a potent chemosensitizing agent of complex III inhibitors disrupting the mitochondrial respiratory chain in fungi. Addition of KA greatly lowered the minimum inhibitory concentrations of complex III inhibitors tested against certain filamentous fungi. Efficacy of KA synergism in decreasing order was pyraclostrobin > kresoxim-methyl > antimycin A. KA was also found to be a chemosensitizer of cells to hydrogen peroxide (H₂O₂), tested as a mimic of reactive oxygen species involved in host defense during infection, against several human fungal pathogens and Penicillium strains infecting crops. In comparison, KA-mediated chemosensitization to complex III inhibitors/H₂O₂ was undetectable in other types of fungi, including Aspergillus flavus, A. parasiticus, and P. griseofulvum, among others. Of note, KA was found to function as an antioxidant, but not as an antifungal chemosensitizer in yeasts. In summary, KA could serve as an antifungal chemosensitizer to complex III inhibitors or H₂O₂ against selected human pathogens or Penicillium species. KA-mediated chemosensitization to H₂O₂ seemed specific for filamentous fungi. Thus, results indicate strain- and/or drug-specificity exist during KA chemosensitization.

Enhanced control of species of Cryptococcus, non-fermentative yeast pathogens, was achieved by chemosensitization through co-application of certain compounds with a conventional antimicrobial drug. The species of Cryptococcus tested showed higher sensitivity to mitochondrial respiratory chain (MRC) inhibition compared to species of Candida. This higher sensitivity results from the inability of Cryptococcus to generate cellular energy through fermentation. To heighten disruption of cellular MRC, octyl gallate (OG) or 2,3-dihydroxybenzaldehyde (2,3-DHBA), phenolic compounds inhibiting mitochondrial functions, were selected as chemosensitizers to pyraclostrobin (PCS; an inhibitor of complex III of MRC). The cryptococci were more susceptible to the chemosensitization (i.e., PCS + OG or 2,3-DHBA) than the Candida with all Cryptococcus strains tested being sensitive to this chemosensitization. Alternatively, only few of the Candida strains showed sensitivity. OG possessed higher chemosensitizing potency than 2,3-DHBA, where the concentration of OG required with the drug to achieve chemosensitizing synergism was much lower than that required of 2,3-DHBA. Bioassays with gene deletion mutants of the model yeast Saccharomyces cerevisiae showed that OG or 2,3-DHBA affect different cellular targets. These assays revealed mitochondrial superoxide dismutase or glutathione homeostasis plays a relatively greater role in fungal tolerance to 2,3-DHBA or OG, respectively. These findings show that application of chemosensitizing compounds that augment MRC debilitation is a promising strategy to antifungal control against yeast pathogens.

The suitability of adult male the navel orangeworm, Amyelois transitella (Walker) for Sterile Insect Technique (SIT) has been reported for both high energy gamma (>1 MeV) and low energy x-ray (90 keV) sterilization. However, research regarding sterilization of NOW larvae and pupae by gamma irradiation indicated nonsuitability due to high mortality. Here, NOW larvae and pupae were irradiated to doses up to 50 Gy with 90 keV x-rays, then paired with nonirradiated colony mates. Sterility of surviving insects was determined by the presence or absence of hatched neonates. While presence of offspring does not guarantee viability, the absence does guarantee sterility (as is appropriate for SIT) and was thus the measure used here. Early stage larvae experienced 77% mortality at a dose of 30 Gy, versus 20% for nonirradiated control. At 40 Gy, mortality reached 98%. Of surviving early stage larvae at 30 Gy, 29% of moth pairs produced offspring. For late stage larvae, no offspring were produced at 40 Gy, but mortality was 73%. For pupae, mortality reached 53% at 30 Gy with 13% still producing neonates, while mortality reached 98% at 40 Gy. These results are consistent with reported results for gamma irradiation of NOW larvae where sterility was observed somewhere between the 30 Gy and 60 Gy data points, but mortality was high. This further confirms the lack of suitability of NOW irradiated in the larval stage, whether by gamma or x-ray, and supports the hypothesis that x-ray and gamma treatments are biologically equivalent at equal doses.

The aim of this study was to examine two benzo analogs, octylgallate (OG) and veratraldehyde (VT), as antifungal agents against strains of Aspergillus parasiticus and A. flavus (toxigenic or atoxigenic). Both toxigenic and atoxigenic strains used were capable of producing kojic acid, another cellular secondary product. A. fumigatus was used as a genetic model for this study. When applied independently, OG exhibits considerably higher antifungal activity compared to VT. The minimum inhibitory concentrations (MICs) of OG were 0.3 - 0.5 mM, while that of VT were 3.0 - 5.0 mM in agar plate-bioassays. OG or VT in concert with the fungicide kresoxim methyl (Kre-Me; strobilurin) greatly enhanced sensitivity of Aspergillus strains to Kre-Me. The combination with OG also overcame the tolerance of A. fumigatus mitogen-activated protein kinase (MAPK) mutants to Kre-Me. The degree of compound interaction resulting from chemosensitization of the fungi by OG was determined using checkerboard bioassays, where synergistic activity greatly lowered MICs or minimum fungicidal concentrations. However, the control chemosensitizer benzohydroxamic acid, an alternative oxidase inhibitor conventionally applied in concert with strobilurin, did not achieve synergism. The level of antifungal or chemosensitizing activity was also “compound - strain” specific, indicating differential susceptibility of tested strains to OG or VT, and/or heat stress. Besides targeting the antioxidant system, OG also negatively affected the cell wall-integrity pathway, as determined by the inhibition of Saccharomyces cerevisiae cell wall-integrity MAPK pathway mutants. We concluded that certain benzo analogs effectively inhibit fungal growth. They possess chemosensitizing capability to increase efficacy of Kre-Me and thus could reduce effective dosages of strobilurins and alleviate negative side effects associated with current antifungal practices. OG also exhibits moderate antiaflatoxigenic activity.

We evaluated the low-density application of 50 dispensers per hectare, in contrast to the traditional >800 dispensers per hectare in apple orchards, to achieve disruption of communication of adult codling moth, Cydia pomonella (L.), in walnuts, Juglans regia (L.), using several methods. These methods included cumulative catches of male moths in traps baited with sex pheromone (Ph) or codlemone, (E,E)-8,10-dodecadien-1-ol, or a combination of codlemone, pear ester (PE), ethyl (E,Z)-2,4-decadienoate, and acetic acid, and by examining the mating status of females. These data were collected from 2011–2014 in nontreated plots and in similar plots treated with Meso dispensers loaded with codlemone (Ph Meso) or codlemone and PE (Ph + PE Meso). Male moth captures in both the Ph and combination lure traps reduced by 88–96% and 72 to 77%, respectively, compared with traps in the nontreated plots. A significantly higher proportion of female moths were nonmated in plots treated with Ph + PE Meso dispensers (33%) than in plots treated with Ph Meso (18–26%), or left nontreated (13%). In addition, significantly fewer multiple-mated females were trapped in the Ph + PE Meso-treated plots (6%) than in either Ph Meso-treated (13–18%) or nontreated plots (23%). These data suggest that the addition of PE can effectively improve Ph-based disruption of C. pomonella in walnut orchards. In addition, these data suggest that the use of low-density hand-applied dispensers can be an effective and lower-cost approach to manage this pest in the large canopy presented by walnut orchards.