Monday, August 31, 2015

Tomatoes with Blossom End Rot

What causes the bottom end of green tomatoes to rot?
Blossom end rot (BER) is a physiological disease. This type of disorder is caused by something other than a fungus, bacteria, virus, etc., and therefore there is no need to spray with a pesticide.

Symptoms may occur at any stage of fruit development but most often on the immature, green fruit at one-third to one-half full size. Tomatoes will show light brown spots at or near the blossom end, and while ripening, these spots gradually expand into a sunken, leathery, brown or black lesion.  Sometimes hard, brown areas develop inside the fruit.

Recent studies show that blossom end rot results from a low level of calcium in the fruit. Adding lime to the soil will help prevent this problem.  

BER is aggravated by excessive amounts of fertilizer, particularly nitrogen and low soil moisture or irregular watering patterns. Use nitrate nitrogen as the nitrogen source. Ammoniacal nitrogen may increase blossom-end rot as excess ammonium ions reduce calcium uptake. Fertilizing with nitrogen during early fruiting should be avoided. Drought will increase BER along with wide fluctuations in soil moisture; mulching will help.

BER is more common on sandier soils. Some varieties are more affected than others. Check seed catalog descriptions for those varieties that are resistant. Peppers, eggplant and zucchini squash  can also be susceptible to BER.