Gordon Johnson, Extension Vegetable & Fruit Specialist; firstname.lastname@example.org
Over the last week we have had freezing temperatures in some locations, high winds, and wind-blown sand that have damaged early planted vegetables. Temperatures as low as 28 °F were recorded on May 10 and winds gusted to 40 mph on May 9. High winds continued through May 12 and on May 13 there was another night in the 30’s
This combination has resulted in extensive damage in vegetable crops. Some symptoms are marginal leaf burn, leaf bleaching, leaf desiccation, leaf dropping, stem browning, and in some cases, plant losses. Symptoms are most severe on newly transplanted crops or transplants that have not yet rooted in well. In conventionally tilled field there was extensive sandblasting on our light soils with high winds.
Growers with damage should evaluate plants for the extent of damage and need for replanting. Wilted, snapped, broken, or severely “wind burnt” plants may need to be replaced. Growers should also consider applying protectant fungicides/bactericides to reduce infections by opportunistic disease organisms on damaged tissues.
Damage on potato will appear 1-3 days after the freeze event. The symptoms commonly will be black areas on leaves that dry out. Seed piece are well below ground and will not be damaged. If the apical meristem is killed, the growing point will move to an axilliary bud(s) lower on the stem and growth will continue. The plants may be set back a few days depending on the severity of the damage,
Temperatures between 29-32 °F will cause minor injury, but temperatures below 28 °F may kill the plant to the ground.
Freeze damage in potatoes. Note the black and dried out areas on damaged leaves. Potatoes will grow out of this damage with little effect on yield.
Several hundred acres of watermelons were transplanted over the last 2 weeks on Delmarva. Freezing temperatures and high wind caused severe damage in some fields that will require selective replanting. Fields with strong rye windbreaks had the least damage. Wind-blown sand has “sandblasted” some fields. Symptoms of damage on watermelon will be dark brown to black areas on leaves that become papery. Plants with live growing points will recover; however, If the growing point was damaged, the plants would have to regrow from the buds at the cotyledon.
Watermelon plant with dead growing point. Buds at the cotyledon are intact. However, without any leaves, the plant may not have enough energy to regrow.
Watermelon plant with live growing point and only one leaf damaged. This plant will regrow.
Watermelon plant with dead leaves and damaged growing point but with live buds at the leaf axil and cotyledons. This plant is marginal on the potential for regrowth
Watermelon plant with minimal damage will continue to grow.
Hundreds of acres of both processing and fresh market sweet corn have been planted. Growth has been slow and many fields have freeze and “sand blasting” damage. Effects on corn will depend on where the growing point is and if the growing point was damaged. At V-4, the growing point is just below the ground. By V-6, the growing point is above the ground. For most sweet corn, a light freeze will damage the leaves but the plants will continue to grow because the growing point is still alive. In a sand-blasted field, even though the growing point is still below the ground, the plant is cut off at the soil line. There are no leaves left and an open wound subject to disease entry. These fields may have to be replanted.
Sweet corn damaged by the freeze. These plants will regrow from the growing point.
Peas in Flower
Peas in flower can tolerated short periods below 32 °F (a few hours). However, several days in a row with night freezes will cause yield losses. The most common symptom of damage to peas is blanks where seeds are missing in the pod due to incomplete pollination. This has been observed in early varieties such as Jumpstart in the past.
Throughout Delaware, freezing temperatures damaged or killed unprotected tomatoes. Tomatoes are a warm season vegetable that cannot tolerate any frost or freeze event. Damaged plants will have to be replaced.
Tomato plant killed by the recent freeze. This plant was covered but it did not provide adequate freeze protection.