Strategies and product selection in apple scab control

Economical and pomological factors have increased the sensitivity of modern orchards for fungal diseases. Different strategies must be integrated in the control measures to achieve a sustainable production system. The disposal of modern fungicides with a high performance is only one pillar in disease management. Sanitation, optimal timing of spray treatments, adequate application techniques and resistance risk modifiers are the main tools to reach an integrated durable fruit production structure. Besides this agricultural approach, the consumer attaches more importance to the side effects of pesticides on the environment and eventually the residues left on the fruits. Scab (Venturia inaequalis on apple and Venturia pirina on pear) is the key parasite on pip-fruits. On the most commercial varieties, more than 60 percent of treatments are related with scab control. The evolution to monocultures of one-variety, and the ban of plant growth regulators to shorten the growth period and in this manner the infection period, has increased the infection pressure to a level that one mistake in the spray program can lead to an economic disaster. The recent concept of widening the varietal offering of apples as one of the remedies to the apple crisis can help in diminishing the infection pressure of scab. In the scab risk assessment, biological factors as inoculum, varietal susceptibility, ascospore release and leaf growth are incorporated in Mills infection periods to improve scab warning services. The determination of biotic parameters is enormous labor consuming and here software image analysing systems and simulation models can facilitate the infection risk estimation. The available fungicide families, demethylation inhibitors, anilino-pyrimidines and the recent developed strobilurins, must be positioned during the growing season in relation with optimal biological and climatological circumstances. Also the block treatment, which was introduced by the launching of the strobilurins, is a new issue in disease management. The combined use of fungicide families with complementary effects on different fungal developing stages together with a limited number of treatments with one family per season must prolong the lifetime of modern fungicide families. The flexibility in product choice, doses and quality care of the application over the different treatments must lead to a durable management of apple diseases in the orchard.