Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu
This season, some strawberry growers in Delaware have been contacted by their plug plant suppliers to alert them that Neopestalotiopsis (aka Pestalotia or Neo-P) has been present in the plugs they are producing. Nurseries are working to dispose of infected plants and prevent spread of the disease, however they cannot guarantee that the plugs that growers receive will be free of Neopestalotiopsis. Growers must decide whether to cancel orders or take plants that may have the disease.
Growers who are planting plugs from nurseries where Neopestalotiopsis has been identified should take action this fall to prevent development and spread of this disease in their strawberry crop. All strawberry growers should be alert to symptoms of this disease in their fields.
Know the Symptoms
Neopestalotiopsis causes leaf spot, crown infection and fruit rot. The leaf spot and crown infection symptoms are most relevant to fall disease scouting. Foliar symptoms are tan leaf lesions which develop small black fungal structures (pycnidia) under wet conditions. If crowns become infected the whole plant will wilt, but leaf lesions may not be present.
Leaf symptoms typical of Neopestalotiopsis
Leaf symptoms typical of Neopestalotiopsis
Black pycnidia form in lesions of leaves infected by Neopestalotiopsis.
Black tendrils of spores emerging from pycnidia on a strawberry leaf infected by Neopestalotiopsis.
Neopestalotiopsis crown infection showing characteristic reddening of leaves, wilt and stunting of new growth.
Cull Unhealthy Plants
Inspect transplants before planting and do not plant transplants that appear unhealthy. Destroy culled transplants. Throughout the fall, scout for plants with symptoms of Neopestalotiopsis and remove and destroy symptomatic plants. Plants with suspected disease can be submitted to the UD Plant Diagnostic Clinic by bringing them to any of the county Extension offices.
Fall Fungicide Applications
Thiram and Switch are the two fungicides recommended for Neopestalotiopsis control in the Strawberry section of the Mid-Atlantic Commercial Vegetable Production Recommendations. Bill Cline from NC State recommends reserving Switch for use only in the spring, since it is also important for preventing Anthracnose and Botrytis fruit rots, and overapplication risks development of fungicide resistance. His recommendation is to use Tilt, Rhyme or Inspire (collectively limited to 4 applications) in rotation with Thiram for fall applications. Start fungicide applications right after planting and make repeat applications every 7-14 days. If weather conditions are wet and more conducive to disease development use the 7-day spray interval. Continue fungicide applications until temperatures are consistently below the temperature range conducive to this disease, 50-86 °F. Note that disease symptoms can be observed at temperatures as low as 41 °F if conditions are wet.
Avoid Physically Moving the Disease
Neopestalotiopsis spores can be spread on workers or equipment. It is important to sanitize tools and equipment to prevent the movement of the disease in the field or between fields. Avoid working with plants under wet conditions.
Additional Articles on Neopestalotiopsis
Dramatic Neopestalotiopsis Disease in Strawberry Tips and Plug Plant Production Nurseries
Neopestalotiopsis Leaf, Fruit, and Crown Rot of Strawberry
Best Management Practices for Neopestalotiopsis
Strawberry Disease Identification: Neopestalotiopsis (aka Pestalotia) or a More Traditional Disease?