Location: Food Quality LaboratoryTitle: Baseline sensitivity of Penicillium spp. to difenoconazole
|PETER, KARI - Pennsylvania State University|
|COX, KERIK - Cornell University - New York|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2018
Publication Date: 12/18/2018
Citation: Jurick II, W.M., Macarisin, O., Gaskins, V.L., Janisiewicz, W.J., Peter, K.A., Cox, K.D. 2018. Baseline sensitivity of Penicillium spp. to difenoconazole. Plant Disease. 103:331-337. http://doi.org/10.1094/PDIS-05-18-0860-RE.
Interpretive Summary: Blue mold is a widespread, and economically important fungal disease of stored apple, pear, and quince fruit. To help control this important problem, a new postharvest fungicide (Academy) was released in 2016. However, tools to monitor development of resistance to this new material are absent, control of postharvest fungicide-resistant strains with Academy are unknown, and effects of preventative or curative application have not been determined. Thus, our study demonstrated a specific dose of active ingredient to detect early shifts in sensitivity indicative of resistance, that Academy controls multiple fungicide-resistant blue mold strains, and curative treatments were most effective at eliminating decay in commercial storage conditions. The data developed from this study will be used by customers and stakeholders to detect early shifts in sensitivity and can be used to screen resistant isolates. This information will be critical to maintain fungicide efficacy of this new postharvest chemical to maintain high quality, fresh, safe fruit during storage and shipment.
Technical Abstract: Penicillium spp. cause blue mold of stored pome fruit. These fungi reduce fruit quality and produce mycotoxins that are regulated for processed fruit products. Control is achieved by fungicide application and in 2016, Academy was released for use on pome fruit to manage postharvest blue mold containing fludioxonil and difenoconazole. Baseline sensitivity for fludioxonil, but not difenoconazole has been determined for P. expansum. To establish the distribution of sensitivity before commercial use of Academy, 97 unexposed single spore isolates from the US and abroad were tested in vitro. Baseline EC50 values ranged from 0.038-0.827 µg/ml difenoconazole with an average of 0.16 µg/ml. Complete inhibition of mycelial growth for all but three isolates occurred at 5 µg/ml difenoconazole, while 10 µg/ml did not support growth for all isolates examined. Hence, 5 µg/ml difenoconazole is recommended for phenotyping Penicillium spp. isolates with reduced sensitivity. Single and dual postharvest fungicide-resistant isolates were observed in representative isolates from the baseline collection. Academy applied at the labeled rate, had better curative than protectant activity and controlled 4 representative Penicillium spp. from the baseline population. The information generated can be used to monitor future shifts in sensitivity to this new postharvest fungicide in blue mold populations.