Last week’s article discussed several of the more common fungal and bacterial diseases that affect tomatoes. This week’s article discuses several physiological or non-disease problems.
Blossom end rot (BER) appears as a dry leathery spot on the blossom end of tomatoes. It can also affect peppers and watermelons. The spot is usually on the blossom end, is tough and leathery and slightly sunken. Other rots may infect this spot. These fruits may turn red first.
BER is caused by lack of calcium in the blossom end of the fruit. By the time the tomato reaches the size of a nickel it has most of the calcium that it will ever have. This is why we need to prevent blossom end rot early. Inadequate water supply, low pH or low soil calcium levels can cause this problem. Find and correct these problems.
Once a plant has BER, it is hard to control. Calcium is best taken up by the roots so sprays are not as effective. To control and prevent BER:
•Keep your tomatoes’ water supply even throughout the season so that calcium uptake is steady. Tomatoes need 1 to 2 inches of water per week. They perform best when watered deeply a couple of times a week rather than lightly every day.
•Apply a two to three inch mulch around the plant. Do not heavily prune the plant.
•Take soil samples to determine lime and fertilize needs. Avoid large applications of high nitrogen fertilizers when fruit are small.
•Add gypsum (calcium sulfate) or lime to the soil at planting. Mix a cup in each planting hole or use one pound per 100 square feet. You can apply this once you see the problem but these treatments work slowly. Plants often appear to grow out of the problem as conditions improve.
Tomato flowers will fail to set fruit if temperatures are not right, if the plant is water-stressed, or if it already has enough fruit. Night temperatures should be 55 to 75 degrees Farenheit. for best fruiting. Night temperatures above 90 degrees will especially cause problems. Water twice a week (3/4 inch each time) and mulch plants. There is a blossom set chemical you can spray if you can locate it in the garden centers.
Leafrolling occurs when the plant has set a heavy load of fruit and the light intensity is high. It can be caused by overly wet soils. The condition is harmless and should not hurt final production. Prune less heavily and plant in a well-drained area.
Uneven ripening occurs as grey or white spots inside the fruit. Several factors can be involved including improper nutrition, high temperature and disease. The only thing we can correct is nutrition.
Do not use too much nitrogen and/or too little potassium. Soil sample and fertilize accordingly. Use high potassium fertilizers – 5-10-15, 15-0-15 – especially as fruits begin to get larger than a quarter.
Fruit cracking is due to rapid growth after periods of slow growth. Heavy rain after drought and/or heavy fertilization can cause fruit cracking. Harvest fruits after they begin to turn red but before they crack. Follow the watering practices we have discussed and look for cracking- resistant varieties.
Catfacing is caused by cool temperatures at time of pollination. The fruit is deformed with “zippers” on the skin. The fruit can have lobes, tear drops or several blossom scars.
Plant resistant varieties, plant later, or use row covers to increase the temperature on cool days and nights. The large beefsteak varieties appear to be more susceptible. The fruit is still edible.
Sun scald appears as a white blistered area on the top of the tomato. Do not prune heavily and maintain nutrition and pest control so as to provide a good leafy cover for the fruits. Be careful not to confuse this with blossom end rot.
Randy Drinkard is the ANR Agent for The University of Georgia Troup/Meriwether County Cooperative Extension. The Troup County Extension office is located at 114 Church St. and can be reached at 706-883-1675. Open Monday through Friday, 8 a.m. to 5 p.m.