Pepper transplants. Photo: Tom Ford, Penn State
What to look for following a cold, wet spring?
Based on a recent discussion held by Penn State Extension’s team of faculty and educators working in vegetable and small fruit production, the following are some important things to look out for in the field following this cold, wet spring.
- When plants grow slowly, and root systems don’t develop well due to cold temperatures and too much rain, they can become very susceptible to heat and drought stress once the summer sun comes out and rainfall decreases. When conditions improve, careful cultivation and additional applications of fertilizer, if appropriate, may help plant root systems rebound.
- Be on the lookout for late blight (Phytophthora infestans) in potatoes and also greenhouse tomatoes. In previous years with cold and wet springs, late blight has been found as early as the beginning of June in Pennsylvania.
- Small fruit growers should be on the lookout for Botrytis grey mold , especially with the prolonged bloom period, as well as Botrytis crown rot.
- The cold spring may be slowing down pollinator activity, both wild pollinators, and honeybees. This year, in particular, it is worth taking extra steps to protect pollinators from pesticides and to provide them with good habitat and food sources during the upcoming summer and fall.
- Pythium root rot can challenge slow growing and stressed root systems. The fungus will primarily colonize the small feeder roots causing them to turn brown and sluff off.
Photo: Pythium root rot (left) and healthy (right) watermelon transplant roots. Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org
We have observed several instances of herbicide injury to crops around the state, including in strawberries, leafy greens, and vegetable transplants. Herbicide injury in the field can be more common in a cool, wet spring. Plants already weakened by poor growing conditions can be more susceptible to injury, for example, strawberry plants coming slowly out of dormancy. Herbicides can injure plants in the greenhouse and high tunnel, as well. Don’t store herbicides in greenhouses or high tunnels, where they may volatilize and injure seedlings.
In general, strawberry fields have been slow to get going due to weather and to winter damage; deer damage has also been a problem. Powdery mildew was found on strawberries in one greenhouse, probably linked to prolonged cloudy weather and poor air circulation. Black root rot with Rhizoctonia involved was found recently in a strawberry field.
Cool, wet springs are ideal for Delia maggots , and we are seeing more cabbage maggot damage than usual this spring. Seed maggots also caused damage to a watermelon crop in central Pennsylvania. Allium leaf miner is now active in eastern Pennsylvania in onions and other allium crops. Some timber rot (Sclerotinia sclerotiorum) has also been observed in high tunnel tomatoes.
We are seeing some isolated cases of vegetable seedlings that are severely stunted and chlorotic, despite having adequate water and nutrient applications. When this problem arose last year, it was linked to a particular potting mix product. If you observe unusual stunting and chlorosis in your vegetable transplants, contact your local Extension educator so that we can follow up.