CHAMBERSBURG, Pa. — Summer may bring bountiful harvests of beans, sweet corn, cucumbers, tomatoes, and other produce, but it also brings its share of problems for the home vegetable gardener. There are some common problems that show up every summer, but the recent hot, dry weather can make them worse.
Blossom End Rot
Blossom End Rot (BER) is not a disease, but the result of insufficient calcium in the plant when the fruit is developing. The lack of calcium in the plant causes the blossom end (opposite the stem) of the fruit to become dark brown, leathery, and sunken. It frequently appears on the first ripening fruit of the season.
Although there is usually enough calcium in the soil, the roots are unable to absorb it for a variety of reasons. Drastic moisture fluctuations in the soil, the result of too much or too little rainfall; high temperatures; excessive nitrogen fertilization; rapid plant growth; or damage to the roots due to cultivation, are all possible causes for inadequate calcium uptake.
The solution is to make sure that you supply an adequate amount of moisture to the plant – about 1 inch per week – during the growing season. Drip irrigation and straw or plastic mulch will help you to ensure even moisture to the plant.
The results of a soil test will give you the proper amounts and kinds of fertilizer to use on your tomatoes. When the flowers and fruit start developing, use a fertilizer designed for tomatoes to ensure adequate levels of phosphorus and potassium, both important for fruit production; the first number in the fertilizer ratio (nitrogen, N) should be low compared to the last two numbers.
For a quick fix, you can try a calcium spray applied to the foliage (not the fruit). It’s important to follow the label directions, as you can burn the foliage if you apply too much or too often; the calcium spray won’t correct affected fruit, but it may help to prevent BER on fruit just beginning to develop.
Foliar calcium is a stopgap measure, not a substitute for proper fertilization and watering. A soil test and good soil preparation, along with even moisture, are the best solutions to BER.
Tomatoes affected by BER will not recover; removing them from the plant when you first notice BER may help later-maturing fruit from developing the same problem. BER can also happen to peppers and eggplant.
Tomato Leaf Roll
Tomato leaf roll is usually seen on older leaves. The leaflets curl up lengthwise, sometimes into a very tight roll, and they often become thick and leathery as well. Although you may find an insect or spider hiding in that rolled up leaflet, the critter is not the cause of the problem, nor is this a disease.
Leaf roll is a physiological condition, a functional response of the plant to some stress factor, and it can be worse in some tomato varieties than in others. The plant senses it is losing more moisture through the leaves than can be replaced through the roots, so it tries to compensate by rolling the leaves and making them thicker to reduce water loss.
Stress factors that can lead to leaf roll include heavy pruning, excessive fertilizer, cultivating too close to the roots, saturated soil after a heavy rain, or any sudden change in weather. It often happens when mild, rainy spring weather transitions to hot, dry summer weather, and the plant’s top growth has outstripped root formation.
Fortunately, leaf roll is not something you need to worry about, as it does not affect growth or yield, and it will often correct itself when conditions become more favorable. To minimize leaf roll on tomatoes, use mulch to keep the soil at more even temperature and moisture levels; don’t damage the roots by cultivating or hoeing too close to the plants; and water well to keep the soil moist, but don’t overwater so it stays saturated – the soil needs to dry out slightly between watering.
Bitterness in cucumbers increases when plants are stressed from drought, high temperatures, or poor fertilization. As with BER, the solution is to ensure an adequate supply of water to the plant – 1 to 1.5 inches per week – during the growing season. Use drip irrigation, or deep but less frequent watering, combined with mulch to conserve moisture and keep the soil cooler. Sufficient water may lessen the bitterness in later fruit.
Cucurbitacin, the compound that causes bitterness in cucumbers, is usually found in the leaves, stems, and roots of the plant, but it can move into the fruit when the plant is stressed. Fruits on the same plant can be affected to varying degrees. In the fruit, it is often concentrated in the stem end and in the skin; cutting away those parts may remove the bitterness. But if the whole fruit is bitter, discard it; nothing, not even pickling, will make it taste any better.
Many newer cucumber varieties have been bred to be “bitter-free” or “burpless.” Look for burpless or bitter-free cultivars – including Carmen, County Fair, Diva, Green Knight, Sweet Slice, Summer Dance, Sweet Success, and Tasty Green – when selecting plants or seeds next year.
–Annette MaCoy, Penn State Extension