CORVALLIS, Ore. — When grape growers discover stunted or distorted vines in their vineyards, their first impulse may be to reach for an insecticide.
Not so fast, says Patty Skinkis, Oregon State University Extension Service viticulture specialist.
“We’ve fielded a lot of questions over the years from growers worried that they might have rust mites,” she said. “But there are other things that can cause stunting of grapevines.”
Stunted growth can also result from early frost damage, herbicide drift, water stress, nutrient deficiency or disease.
Free app helps identify the true cause
Skinkis is lead author of Recognize the Symptoms and Causes of Stunted Growth in Vineyards, an OSU Extension publication also available as a mobile app.
“We wanted to help growers explore further before they sprayed for a pest that might not be there,” Skinkis said.
The free app, available on iOS devices, provides science-based guidance from eight Extension field faculty. It features clear navigation and numerous full-color photos to help users identify the likely cause of stunting and find the best course of action.
“Because this publication is essentially a diagnostic tool, creating an app made a lot of sense,” Skinkis said.
Guidance from symptom to solution
The publication explains how different causes of stunting affect vines and how those effects appear across a vineyard. It helps growers interpret symptoms, distinguish between possible causes, and locate additional Extension resources related to grapevine health and management.
Although designed for commercial vineyard operators, home grape growers and winemakers may also find it useful.
When and why stunting appears
Stunting often becomes visible in early spring when vines begin producing new shoots. In Oregon, growers sometimes refer to it as “short shoot syndrome.”
Rust mites — microscopic arachnids that feed on young shoots, leaves and buds — are sometimes to blame. But they are not always the cause.
“In many cases, rust mite–infested vines will outgrow the stunting and develop normally through the rest of the season,” Skinkis said. “Severe infestations, however, can reduce yields.”
Recent identification of rust mites by some growers has led others to assume mites were responsible in their own vineyards.
“But the mites are microscopic — you can’t detect them with a hand lens in the field,” Skinkis said. “And because stunting can have a number of causes, it’s important to identify the real problem before you take any action.”
Previously titled Why are my grapevines stunted? OSU Extension has the answers
