Strawberry Notes: Crop Progress and Virus Situation Update

Gordon Johnson, Extension Vegetable & Fruit Specialist;

We have a very late crop of strawberries this year. Plasticulture strawberries are finally in full production but reports are that the crop is lower yielding this year. We had some heavy wind storms that shredded row covers earlier this year leaving plants unprotected until recovered. Wild honey bee activity is down due to winter bee kills so only pollination from rented hives has been effective. Cold windy and rainy weather has also kept bees from flying during some of the bloom period, also reducing berry size in some cases.

Another factor has been virus infected plants that growers received this past year. These plants originated from tips grown by a nursery in Nova Scotia. Several growers on Delmarva received virus infected plants from this source. Strawberry Mild Yellow Edge Virus (SMYEV) and Strawberry Mottle Virus (SMoV) were identified in these plants. Symptoms included poor growth in some plants with older leaves turning red in color, leaf edges on new leaves showing a distinct yellowing, and some leaf margins becoming necrotic.

According to Chuck Johnson, Extension Plant Pathologist for Virginia Tech, “There is no cure for plant virus infection. Once infected, plants are infected for life, and every cell in an infected plant will eventually contain virus. There are no “silver bullets” or miracle cures, despite what some may claim. Infected plants can’t be cured, although growers could see some improvement in their appearance and growth during the spring. Those involved in strawberry plant production in Nova Scotia are aggressively working to correct their virus situation. Although many growers consider carrying strawberry plants over from one season to another, 2013 looks to be a very poor year for this. If possible, all strawberry plants should be destroyed after this season’s harvest is completed, to avoid potential carry-over of SMYEV and SMoV. Leaving potentially infected plants in the field this summer risks virus spread into next years’ crop. Fields in matted-row production should be monitored for potential virus incidence as well. Southern Region strawberry research and extension personnel met with national experts and Canadian representatives in late March to plan methods to avoid a repeat of this coming fall.”

We had frost in some areas on Monday and Tuesday and temperatures in the 80s expected later in the week. Because our strawberry crop is so late, strawberries are still blooming. These blooms have the potential to produce ripe berries in 4 weeks. To keep plants blooming and fruit setting during hotter periods where temperatures are in the mid-80s or above, cooling is advised. Run the drip irrigation very early in the morning and again in the afternoon to keep plants well watered and bed temperatures down. Evaporative cooling using mist or sprinklers can work but increases the risk of Botrytis, which may outweigh its usefulness. Shadecloth may be an option in smaller plantings and straw much over exposed black plastic can help keep beds cooler.