Alternative disease management slashes fungicide use

For two years, Carlson cooperated with UW researchers as they built a predictive model for apple scab around measurements of air temperatures and leaf surface moisture. Some years, he uses only half as many fungicides as conventional growers do on his three scab-susceptible apple varieties — Cortland, Gala and Sweet 16 — while other years he can eliminate only one or two treatments.

On his 1,000 scab-resistant trees, which outnumber his susceptible trees five-fold, Carlson applies no fungicides at all. During the growing season, he quickly cuts out branches showing the earliest signs of fireblight and, during the dormant season, he aggressively prunes any possibly overwintering cankers. "Typically, apple growers spray tank mixtures of fungicides plus insecticides," says Carlson. "On my scab-resistant block, I'm not putting fungicides into the tank, so I feel good about that."

Carlson planted his apples densely — and consequently more expensively — on dwarfing rootstocks. That has allowed him to respond more nimbly to changing consumer tastes, since trees on dwarf root-stocks typically start bearing in two years rather than five. While his customers like learning that their apples were grown without fungicides, Carlson knows that flavor is what sells fruit and that consumer preferences can rival aroma compounds for volatility.

0 0

Post a comment