Plant Pathology (2020) 69, 631-641

Frank van den Bosch, Jonathan Blake, Paul Gosling, Joe C. Helps and Neil Paveley (2020)
Identifying when it is financially beneficial to increase or decrease fungicide dose as resistance develops: An evaluation from long-term field experiments
Plant Pathology 69 (4), 631-641
Abstract: As the frequency of fungicide resistant strains increases in a pathogen population, there is a change in the shape of the response curve of disease severity to fungicide dose. We showed previously, in a theoretical analysis, that such changes can result in an increase or a decrease in the economically optimal dose of fungicide; this depends on how the response curve changes (which is determined jointly by the degree of insensitivity and frequency of a new strain) and the shape of the disease–yield loss relationship (which is a characteristic of the pathogen and crop). Here, we use field dose–response data to estimate economic optimum doses for the control of Zymoseptoria tritici on wheat over a 21-year period. Resistance to fungicide developed to varying degrees against three modes of action (MoA). Changes of optimal dose across years differed according to MoA, but there was an underlying pattern of initial increase in optimal dose, followed by a decrease (ultimately to zero dose at high levels of fungicide resistance). Fungicides are often applied in mixture and analysis shows that, provided the mixture partner is effective, the economic optimal dose increases less as resistance develops than when the fungicide is used as solo product; however, the subsequent decrease in optimal dose remains.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Frank van den Bosch, Jonathan J. Blake

Research topic(s) for pests/diseases/weeds:
damage/losses/economics
pesticide resistance of pest

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Zymoseptoria tritici	Wheat (Triticum)