2022 PA Vegetable and Berry Current Issues for August 16

Over the past 128 years, this July was Pennsylvania’s  24^th driest July and its 103^rd in terms of maximum temperature, averaging 84.0°F for the daily highs. While the Palmer Drought Severity Index ranked PA’s July the 65^th driest over the past 128 years, MA and CT each ranked 11^th this year. For PA, the driest July occurred in 1965 and the wettest in 2019. The current U.S. Drought Monitor places Potter, Tioga, and much of Union Counties at moderate drought (D1) status and surrounding counties in the northern tier, the central-eastern part of the state, and Bucks and Montgomery Counties at abnormally dry (D0) as of August 9, 2022. For more climate-related information, visit the Northeast Regional Climate Center website.

Field Production

Cucumber remains the predominant host for downy mildew in the mid-Atlantic and northeast regions. The closest nearby reports on cucurbits other than cucumber and cantaloupe include eastern TN on butternut squash and most recently on jack-o-lantern pumpkin in a research field in northwest OH. Powdery mildew continues to be reported on a wide array of cucurbit crops in the greenhouse and field, which is typical for this time of the season. The protectant fungicides for downy mildew tank mixed with targeted fungicides for powdery mildew will help protect against both diseases.

Additional reports of Phytophthora blight in cucurbit and pepper fields have also been confirmed. Remember that asymptomatic (visibly healthy) fruit at harvest could still develop symptoms post-harvest. It usually takes several days for visible symptoms to develop. If concerned about post-harvest fruit losses, consider holding back a bin a day or two to see if symptoms develop. If a bin is rejected, avoid disposing of rotting fruit in production fields which could be a source of the inoculum the following year. There are also reports of bacterial diseases in some cucurbit fields. As the fruit develops, the bacteria can splash disperse from the leaves onto the fruit and then enter through natural openings on the fruit surface (lenticels). Eventually, lesions will develop and can also be colonized by secondary soft rot bacteria leading to the complete collapse of the fruit.

Figure 2. Fruit lesions caused by bacterial leaf spot on pumpkin fruit. Photo: Vegetable grower in Bucks Co., PA

Grey mold is reported in some tomato high tunnels as dew periods extend with lower night temperatures. Also, be on the lookout for Septoria leaf spot in field tomatoes and anthracnose on peppers. There continue to be no reports of late blight on tomato or potato in the region.

On the insect front, be on the lookout for cabbage looper in cabbage and kale. These green caterpillars can leave ragged feeding on foliage and contamination due to their frass. Slug damage has been observed in late-planted sweet corn in regions with recent rain and stink bugs on tomato. Stink bug damage can appear as yellow circular lesions on fruit. Spotted and striped cucumber beetles are still being reported in cucurbit fields. As cucurbits finish blooming, options for management expand as the risk of harm to pollinators is reduced.

Berry Crops

Spotted wing drosophila numbers have significantly increased and will only get higher from here on out. Growers should use all available cultural controls to keep numbers as low as possible. These include harvesting brambles, especially raspberries, every day if possible or at least every other day to help to keep SWD populations low. Harvest thoroughly and refrigerate fruit as close to 32 degrees as possible right after you pick it. Even a few hours at warm temperatures can speed up the development of SWD while refrigerating the fruit at very cold temperatures will kill eggs and recently hatched larvae. Remove cull fruit from the planting and bag it; do not just compost it. Keep plantings weeded to keep the humidity low in the plants, as SWD loves humid conditions. Spray every row so that each side of every row is thoroughly covered. This will also minimize SWD hiding places and allow sprays to infiltrate the canopy. Available insecticides can be found in the article Spotted Wing Drosophila: A 2021 Update for Berry Growers.

Figure 3. Two SWD larvae (white square), an egg under the skin with breathing tubes (arrow), and more breathing tubes from other eggs (ovals) on blackberry. Photo:  K. Demchak, Penn State

Blackberries with sunscald have been noted. High temperatures and bright sunlight can result in either bleached drupelets or drupelets that revert to a red color after cold storage. The use of 30% shadecloth in the field has reduced sunscald incidence in studies done elsewhere. In research at Penn State, high tunnel plastics that diffused light and reduced UV practically eliminated the problem. Keep in mind that SWD larvae feeding in a drupelet will also cause it to lighten in color, which could be mistaken for sunscald.  

It is getting to the time of year when day-neutral strawberry yields will increase as temperatures cool. Unfortunately, so are the populations of pests with multiple generations like thrips and tarnished plant bug (besides spotted wing drosophila). Thrips cause bronzing of the fruit surface, and the surface damage caused by their feeding can result in seeds being raised and easily rubbed off (so can powdery mildew) as the berry surface does not expand like usual to surround the seeds. Treatment is only needed if populations become high enough to affect fruit quality. Radiant or Entrust are the most effective products, with Assail being an option. Tarnished plant bugs will cause button berries. If you spray for spotted wing drosophila, you are unlikely to need additional sprays for tarnished plant bug since broad-spectrum products used for SWD also control this pest.

Figure 4. Surface bronzing from thrips feeding and a raised seed can be seen on this strawberry (Photo:  K. Demchak).

Given the dry conditions in many locations in the state, you may hesitate to direct water resources to crops finished producing for the year like June-bearing strawberries, summer-bearing raspberries, or blueberries. However, remember that how well these crops grow this year will determine next year’s yields, so please keep your berry crops in mind throughout the rest of the summer.