Risk Of Apple Scab Is High Despite Cold Temperatures

Although temperatures are chilly, the risk for scab is still high, industry insiders say.

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“The recent winter-like conditions do not kill scab spores and the spores continue to further mature and release. If the weather forecast comes to fruition, an apple scab infection event is predicted for April 7,” writes Kari Peter, Assistant Professor in the Department of Plant Pathology and Environmental Microbiology at the Penn State Fruit Research and Extension Center. “If your trees have green tissue, recommendations for dealing with scab while managing cold injury are discussed.”

Peter suggests growers in Pennsylvania follow her up-to-date posts on her twitter account @DrTreeFruit.

David Rosenberger, Professor Emeritus, Department of Plant Pathology and Plant Microbe Biology, Cornell University says the cold and wind is expected to continue.

“Orchards sprayed last week should still have enough residues to squeak through this potential infection period, but orchards that have not yet been sprayed and those that were sprayed prior to the rains Monday, March 28th, could be at risk,” he writes. “The situation is further complicated by weather predictions for windy weather through much of the remainder of the week and by concerns that pesticides applied after freezes may exacerbate leaf injury.”

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Rosenberger posts some tips for growers on what to do with both a threat of scab infection and cold temperatures on his blog.

Mary Concklin, Visiting Associate Extension Educator in the Fruit Production and IPM Department at the University of Connecticut, offers some suggestions on frost protection for growers and what the best options for weather patterns.

In addition, Win Cowgill, Agricultural Agent and Regional Fruit Agent for Rutgers Cooperative Extension suggests growers consider foliar potassium to protect against frost and freeze incidents.

“There is some indication that foliar potassium applied to apple can help protect against frost, freeze. Maybe,” he writes. “I would guess we might get a few degrees of assistance. The idea is the potassium increases the turgor of the cell walls.”

 

 

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