2022 PA Vegetable and Berry Current Issues for July 5

For PA, the cooler than average conditions fell across the far eastern part of the state including Lancaster, Chester, Lehigh, and Berks counties, and the northeastern corner of the state. Meanwhile, precipitation varied from 25% of normal to over 200% of normal. Much of PA was below average with Erie Co. recording its 18th driest June on record. Currently, July is forecasted to be wetter than normal in the southeastern region of PA while temperatures are predicted to be higher than normal across much of the state.

Figure 2. June 2022 average temperature and percent of normal precipitation from the Northeast Regional Climate Center.

Field Production

Since being confirmed on cucumber in Lancaster County on June 23, there have been no new reports of cucurbit downy mildew in the region. However, in southeastern PA there have been several very favorable days for downy mildew spread and development over the past week. Regular scouting and use of downy mildew specific fungicides on cucumber and cantaloupe is recommended especially if rain is in the forecast.

If you suspect downy mildew, please let us know. Other diseases being observed in cucurbits include angular leaf spot as well as bacterial wilt on pumpkin which is transmitted by the spotted and striped cucumber beetles. The youngest cucurbit plants are most likely to die because of bacterial wilt. No powdery mildew has been noted yet, but it has been recently reported in southern NJ.

Bacterial diseases of onion are increasing in fields that have received some of the heavier rains. Storm damage can create entry points for pathogens so maintaining a fungicide program can help maintain the foliage as the plants are bulbing. Surface feeding damage has been reported in some onion fields. Often this can be attributed to the salt marsh caterpillar (Figure 1) which is much hairier than the leek moth. Although the damage can be extensive it is often very localized in the field and can be managed by manually crushing the pest. Younger stages are more yellow in color but darken as they age.

Black rot on cabbage and broccoli has been reported. It typically comes onto the farm with the seed but can also survive associated with cruciferous weeds or in crop residue. If associated with the seed, then differences between varieties and types of cole crops may be observed. The bacteria can also enter through wounds following heavy rain, hail, insect feeding, or mechanical injury. Depending on the weather conditions, symptoms may be visible within 8 to 12 days, or it may take up to 40 days for symptom expression. Optimal conditions for disease development are temperatures ranging from 77 to 86°F and the presence of free moisture either from rain, fog, dew, or irrigation. Copper is the primary management tool once the crop is in the field to help reduce the spread from infected to healthy plants.

Figure 3. (Left) Tan lesions initiating from the leaf margin with dark veins are characteristic of black rot on cabbage and other cole crops. Photo: Sara Hricko, Penn State Extension. (Right) Female squash bug laying eggs in a diamond-shaped pattern on a pumpkin leaf. Photo: Beth Gugino, Penn State.

There have been additional confirmed reports of tomato spotted wilt virus in tomato field production. This virus is vectored by thrips and is not seedborne. It most commonly affects tomato, pepper, and ornamentals. Removal of infected plants removes a potential source of inoculum. Weed management is also important.

Japanese beetles are now out in high numbers in several regions of the state. They defoliate the area between leaf veins as they feed, leaving behind skeletonized leaves, and are difficult to control with insecticides. There also have been reports of slug damage on sweet potato. Slugs are particularly problematic in areas with high moisture, such as those with straw mulch or dense canopy.

Squash bugs are mating so be on the lookout for the egg masses. When they hatch the young nymphs will remain on the underside of leaves. Insecticides are most effective on the younger nymphs. Recent data from Virginia Tech suggests that Sivanto and Beleaf are effective and help conserve a common parasitoid of squash bug. Squash vine borer is also active as well as cabbage moth. Vine borer feeding will lead to wilted and yellowing plants, often with holes near the base of plants filled with green or orange waste resembling sawdust.

Berry Crops

Any plantings of strawberries that are known to have a significant amount of root or crown disease issues should not be carried over. Disease inoculum will only build up in the planting over time, making disease control in future plantings in the same field more difficult. However, fields showing only a few plants with disease issues may be kept. Now, after renovation, is the time to treat fields prone to Phytophthora issues (red stele or Phytophthora crown rot) with Ridomil Gold SL or Orondis Gold Premix. These products are soil-applied as a banded application or through the drip system. See the label for allowable methods of application.

Several cane diseases are present on blueberry canes including Botryosphaeria and Phomopsis. Botryosphaeria stem blight in particular seems to be becoming more common in PA over time. Warmer and wetter conditions and the plant stress of being planted in less-than-ideal locations and soil types are both likely to be contributing factors to this increase. Fungicides are not particularly effective on Botryosphaeria. Pruning out newly infected canes (Figure 4A) during the summer is the main method of control for either of these blueberry cane diseases and others. Watch for wilting cane tips that do not recover when it is cooler and cut through canes to look for any browning of the cane tissue, either in the center or off to one side of the cane (Figure 4B). Continue to cut lower on the stem until the tissue is light green all the way through, and not water-soaked in appearance (Figure 4C), which may be an indication that the fungus is invading the cane tissue.

Figure 4. Symptoms caused by Botryosphaeria on blueberry canes. Photos: K. Demchak, Penn State

As mentioned in the last issue, scale insects may be found on blueberry plants. Putnam scale can spread to the fruit and settle on it, making it unmarketable. The scale can be difficult to spot and blends in with the cane. Look for it on older canes in areas where the surface of the bark has split, watch for the crawlers and treat them as described in the article Watch for Scale Insects on Blueberries While You Are Pruning.

Spotted wing drosophila (SWD) season is beginning, so be sure to apply insecticides as needed, keep plantings cleanly and frequently picked, and remove cull fruit from the field. There are some indications that sprays applied when SWD first moves into plantings help to keep SWD numbers down later.