Cultivation of, cisgenic or conventionally bred, late blight resistant potato varieties in combination with pathogen population monitoring and a “do not spray unless” strategy resulted in an 80 – 90% reduction of the fungicide use as compared to current common practice. A team of scientists from Wageningen University & Research and Teagasc – the Irish Agriculture and Food Development Authority published these findings in the scientific journal European Journal of Agronomy. 

Phytophthora infestans, the fungus-like causal organism of potato blight, can rapidly destroy potato crops and regularly causes significant losses to potato farmers worldwide. To control this disease, growers commonly resort to spraying their crops with fungicides on a near weekly basis.

The international team of scientists developed a so-called IPM2.0 approach which includes late blight resistant varieties and builds on the preventive and integrative principles of Integrated Pest Management. IPM2.0 allows potato farmers to make the most of more natural ways to control late blight and strongly reduce the necessary input of chemical control agents. It also ensures a yield equivalent to current practise, protects the limited natural germplasm used to create the resistant varieties, is economically beneficial and strongly reduces the environmental impact of potato cultivation as a whole.

The IPM2.0 approach adds three extra components to the current control strategy for potato late blight: the use of resistant varieties, monitoring of naturally occurring genetic adaptations in the pathogen and a ‘do not spray unless’ strategy, which dictates that a grower only needs to apply fungicides when a resistant variety is at risk of infection due to pathogen adaptation. This strategy ensures potato crops are protected at all times while minimising the risk that resistance genes will be overcome and therefore will become useless.

The team looked at issues such as the efficacy of disease control and the resulting environmental impact during cultivation of the susceptible potato variety Désirée and two different resistant potato varieties: Sarpo Mira, developed through conventional breeding, and a resistant version of the Désirée which received a resistance gene from a wild relative through cisgenesis. Cisgenesis allows enrichment of existing potato varieties in as little as 3 years versus current potato breeding programmes that require 10 years or more to produce a novel variety. In addition to accelerating the breeding process, cisgenesis is more accurate than using conventional crossbreeding and selection methods. 

The susceptible potato variety and the two resistant ones were cultivated comparing common practice, with fungicides applied on a weekly basis, and the IPM2.0 method. The research was carried out in the Netherlands and in Ireland, two prominent potato countries, over several years.

The IPM2.0 strategy on the susceptible variety Désirée, resulted in an average reduction of 15% on the fungicide input. Both resistant varieties however remained healthy with an average 80 to 90% reduction of the fungicide input. 

The internationally recognised and publicly available Environmental Yardstick for Pesticides was used to quantify the environmental impact. It quantifies the environmental impact of chemical crop protection on water-life, soil-life and groundwater.  

Susceptible variety Désirée cultivated under common practice annually received an average of over 700 environmental impact points. Désirée cultivated under IPM2.0 reduced this score to some 400 points. Both resistant varieties however scored much better under IPM2.0: cultivation of Sarpo Mira received an annual average of only 40 points, while the cisgenic resistant version of Désirée scored even better, less than ten points.