A growing concern for grape disease control

By Blake Jackson

In the humid climate of Pennsylvania, grape growers face a constant battle against fungal diseases. Fungicides, particularly those containing mancozeb, are essential tools in this fight.

Mancozeb, a multi-site inhibitor, targets fungal pathogens by disrupting multiple biological processes. This broad-spectrum action makes it highly effective against diseases like black rot, Phomopsis, and downy mildew.

Downy mildew is a particularly devastating disease in Pennsylvania's wet climate. Without proper control, it can cause significant crop loss.

Mancozeb's multi-site action makes it less likely for pathogens to develop resistance, ensuring its long-term effectiveness.

In contrast, modern single-site inhibitors, while effective, are more vulnerable to resistance. A single mutation in the pathogen can render these fungicides ineffective.

Metalaxyl, once a highly effective single-site inhibitor for downy mildew, succumbed to resistance within a few years of its introduction.

The impending loss of ziram, another multi-site inhibitor, will further increase reliance on mancozeb. Without it, growers will be left with less effective options like captan and copper.

These alternatives have limitations in terms of efficacy against certain diseases and may face additional restrictions.

The potential loss of mancozeb is alarming, especially considering the growing prevalence of resistance to single-site inhibitors.

Recent research in Pennsylvania vineyards has confirmed that downy mildew pathogens are developing resistance to several single-site inhibitors, including those in FRAC groups 11, P07, and 40. This leaves growers with fewer options for disease control.

Mancozeb's role in resistance management is crucial. Its continued use has helped delay the development of resistance in other fungicides.

If mancozeb is lost, the industry may face a rapid decline in effective disease control options.

The loss of mancozeb would have severe consequences for Pennsylvania's grape industry. It is a vital tool for managing diseases and ensuring the long-term sustainability of grape production in the state.

Photo Credit: istock-jimfeng