May 17, 2021

Current issues in Pennsylvania berry crops pinpointed

As with last year, frost protection of strawberry blossoms has been a challenge for many Pennsylvania growers given the wind that accompanied our cold temperatures. While some blossoms have been lost, most growers are reporting additional bloom that is expected to result in a substantial crop, especially considering that fruit size from later blossoms will increase in size to at least partially compensate for the damage.

Blueberry growers in cooler parts of the state are reporting unusual coloration to new blueberry leaves and emerging blossoms (see Figure 1 at top). This is thought to be a response to the combination of especially cold temperatures this spring with the stage of plant growth. There are varietal differences, with ‘Duke’, ‘Reka’, and ‘Superior’ showing especially deep reddish or copper leaf color, though all varieties are showing odd coloration to some extent.

Mid-season varieties (like Bluecrop) are in peak bloom in central Pennsylvania. Wild bees are out and actively pollinating blueberry blossoms. The most common wild pollinators that have been observed are bumble bee queens and solitary mining bees (genus Andrena). Bumble bees are going through their solitary life stage in early spring when the queens are the only individuals in the nest. This solitary life stage poses a critical time for bumble bees because if they do not find enough floral resources or if they are exposed to lethal levels of pesticides, the queen may die and the colony will not develop.

While insecticide use for blueberries is low early in the season, fungicides are used during bloom to control botrytis and secondary infections of mummy berry, and some of these are also toxic. Category 3 fungicides (Indar, Proline, Quash, and Tilt/Orbit) are known to be highly toxic to bees, so they should be avoided during bloom. They may be used earlier for sprays targeting primary infections of mummy berry, which are made prior to bloom, and fungicides in category 11 (Abound) or 9 and 12 (Switch) may be used instead of them during bloom. Take other precautions to protect pollinators, such as mowing blooming weeds like dandelion in row middles prior to spraying, and/or applying sprays after sunset to minimize bee exposure.

Figure 4. Left: Mining bee pollinating blueberry. Photo: Nash Turley. Right: Bumble bee queen pollinating blueberry. Photo: Margarita López-Uribe/Penn State

The cool temperatures are also keeping warm-weather disease issues tamped down at this point; however, growers are cautioned to remain vigilant. Symptoms of our newest strawberry disease, Neopestalotiopsis, are manageable at this point in the few plantings where this disease is present. Growers continue to report ‘Flavorfest’ plant collapse; this is thought to be due to Phytophthora crown rot that may have been transported with the plants, as even plantings on new ground have had this issue. Windy conditions have resulted in leaf rubbing on strawberries; symptoms are a brown bruising of plant tissue which could be easily mistaken for foliar disease. This type of damage can be differentiated from foliar diseases in that symptoms are present primarily on the uppermost leaves, and any discoloration is only on the surface. Brown markings on petioles are not sunken as with anthracnose.

Figure 5. Tarnished plant bug nymph on strawberry fruit and adult on a strawberry blossom. Photos: Kathy Demchak/Penn State

Tarnished plant bug nymphs are present in strawberry plantings; however, insecticide applications should be avoided until bloom is complete. The threshold for making an insecticide application is 1 tarnished plant bug nymph per 4 blossom clusters, so it is recommended that growers scout as soon as bloom is over and be ready to make an application if needed. This may need to be done by variety to avoid misshapen fruit. Tarnished plant bug nymphs look very different from the adults and do not fly. It is easiest to find the nymphs by tapping blossom clusters over a light-colored surface such as a sheet of paper, as they quickly try to hide once they detect movement. The adults fly away very quickly, so brushing the foliage and identifying them once they land elsewhere usually works best.

Resources for staying up to date with the latest information

• 1-800-PENN-IPM hotline had expanded its menu options  starting with the 2020 production season. Dial 1-800-PENN-IPM (1-800-736-6476) and select from a range of crop groups and topics from vegetables (onion, tomato/potato, sweet corn, vine crops), small fruit, tree fruit, to greenhouse IPM and hear weekly updated 90-second voice messages with the latest information on crop, pest and disease management to help you through the growing season.
• Sign-up with Penn State Extension to receive the latest news and information on vegetable and small fruit crop production as well as pest and disease management either electronically or by calling 1-877-345-0691.
• Cucurbit downy mildew alerts can be obtained by email or text message by signing up. You can specify the distance from your farm for which you would like to receive reports.
• The 2020-2021 Mid-Atlantic Fruit and Vegetable Production Recommendations has the latest information to help commercial vegetable and strawberry growers in the mid-Atlantic region make production and pest management decisions. The hardcopy can be purchased either online or by calling 1-877-345-0691. Individual sections are also available for download . This publication will now be updated every other year so the next update will be in 2022.
• Penn State Extension Informational Kiosks are available at many of the produce auctions across the state. Throughout the season they will provide both education material as well as timely pest and disease forecasting information. Three additional locations are being added this year.
• The MyIPM app is available for free from the Apple Store and Google Play and covers strawberries, blueberries, and blackberries in addition to tree fruit crops. The App is updated with current pests and cultural and chemical controls.

– Beth K. Gugino, Kathy Demchak, Margarita Lopez-Uribe and Shelby Fleisher, Penn State University 

Photo at top: Figure 1. Unusual coloration of blueberry plants due to cold temperatures. Photo: Kathy Demchak/Penn State