Vegetable - Small Fruit Production Issues: July 12, 2018

Downy mildew was confirmed on cucumber in Mifflin County on July 11. Warmer weather throughout the state is helping crops along, but has also been good for insect pests.
Vegetable - Small Fruit Production Issues: July 12, 2018 - News


Japanese beetle on raspberries. Photo: Kathy Demchak, Penn State

We see lots of Japanese beetle activity in multiple crops, as well as onion thrips , potato leafhopper , and mites . Herbicide injury also seems to be on the rise, sometimes due to drift and sometimes to improper application. Downy mildew was confirmed on cucumber in Mifflin County on July 11.


Japanese beetles are out in force and becoming problematic in some fruit plantings such as brambles and blueberries. They also are problematic on basil and congregate on asparagus. While there are several insecticides that can be used to control Japanese beetles in berries, pay attention to the days-to-harvest label requirements. If used for Japanese beetle control, Assail should be used at the highest rate allowed for the crop. Spotted wing drosophila (SWD) activity is increasing, and leafhoppers continue to cause damage on brambles. There are more reports of cyclamen and two-spotted spider mites in strawberries, and a concern that cyclamen mites are moving around with planting material. June-bearing strawberries have finished for the year, although yields were disappointing in many areas.

Japanese beetle adults feed on leaves and fruit of many crop plants. They chew leaf tissue between veins and leave a lacelike skeleton. Photo: Greg Krawczyk, Penn State

Vine crops

Downy mildew was just confirmed on cucumber in Mifflin County PA late this afternoon. This is the first report in PA this season it is likely in other nearby home gardens and fields that have not received any protectant fungicides. Careful and frequent scouting of fields is highly recommended along with starting a spray program if you have not already. It is also present on cucumber in Delaware and New Jersey. Squash bugs are active in many vine crop fields, joining the cucumber beetles that have been out for about a month. At-planting treatments with systemics such as Admire are only effective for a few weeks, and foliar insecticides may be needed to keep squash bugs and cucumber beetles under control. It is difficult to control squash bugs after canopy closure – if you need to spray for squash bugs, try to do it before canopy closure. Bacterial wilt of cucumber has also been reported around the state, as have pollination problems in watermelons. Earlier weather conditions may have limited pollinator activity, even when hives were present near the field, or very high temperatures may have affected pollen viability.

Sweet Corn

Harvest of early sweet corn varieties began in late June and continues, with few problems reported so far this season. Trap counts for lepidopteran pests of sweet corn have been fairly low over the past two weeks.

Tomatoes and Potatoes

Late blight has been confirmed on potato and tomato in southern Lancaster County and York County (previously), and we are following up on reports of possible late blight in eastern Pennsylvania. Growers should be vigilant in their scouting for signs of late blight, and keep up with applications of protective fungicides. Those fungicides will also help manage early blight and Septoria in tomato . We have seen some virus issues in high tunnel tomatoes, and are working on identifying the specific viruses involved. Some potato samples with suspected Dickeya and Pectobacterium have also been submitted for pathogen identification. Blackleg on potatoes continues to be a problem in some parts of the state.

Early blight lesion with concentric rings and characteristic yellowing. Photo: Beth Gugino, Penn State


Early harvests of fresh sweet Spanish onions have begun. Significant damage to onion foliage caused by onion thrips was observed on some farms in western Pennsylvania. These small insects can be difficult to see with the naked eye, but early detection is critical for good control. Allium leaf miner damage has been noted in some onion fields; Penn State researchers are looking at different insecticides, application timing, and the influence of planting date to develop recommendations for controlling this pest. There are also reports of Botrytis and Stemphylium leaf blights in onions.

Onion thrips feed on a wide variety of vegetable plants, small grains, field crops, and weeds. Photo: Whitney Cranshaw, Colorado State University.