The Growing Edge Community - First peppers have BER...

First peppers have BER...

I've peppers in peat and perlite. The first fruit have BER. Why? Would a solution high in Ca and low in NH4 with a low EC be OK?
-- Mario G. de L., 04/15/2002

Dr. Lynette Morgan replies:
Blossom end rot (BER) in peppers can be common under certain environmental and cultural conditions. BER of peppers appears as dark, sunken lesions on developing or mature fruit. This may occur at the blossom end of the fruit or on the side of the fruit wall and is common in the larger-fruited cultivars. This disorder is commonly attributed to a number of factors, such as water stress, calcium (Ca) deficiency, high salinity or electrical conductivity (EC), imbalances of elements in solution, unfavorable environmental conditions, or combinations of these factors. BER is closely associated with a deficiency of calcium in the fruit itself, while calcium levels in the nutrient solution may be more than adequate.

Under conditions favorable to the development of BER, the first fruit to ripen on the plant tend to be those most affected by this disorder and, as a result, even small, immature fruit will show ripening color. Many environmental conditions can influence the onset of BER. Moisture stress has been shown to increase the incidence of BER, as has high salinity and EC levels. So too has high levels of potassium (K) and magnesium (Mg) in the solution. So it appears that K:Ca and Mg:Ca antagonism occurs. High levels of ammonium nitrogen (NH4) have been shown to produce 35-65 percent more blossom end rot, as compared with zero levels on plants grown with the nitrate form of nitrogen. It has also been shown that high calcium levels are incorporated into all plant tissues when the nitrate form is used in the nutrient solution.

So a solution high in Ca, low in NH4 (or no NH4), and with a reasonably low EC will assist the problem. However, you may also need to modify the environment to make the plants less susceptible to BER on later set fruit. High humidity around the fruit also contributes to BER, with less water lost due to reduced transpiration rates. With less water lost during transpiration, the xylem flow (that transports the nutrient solution containing calcium) into the developing fruit is also reduced and this leads to low internal calcium levels in the fruit and a higher incidence of BER. However, this disorder also occurs under conditions of low humidity, when high transpiration rates from the fruit are occurring. Under these conditions, any factor that creates a slow movement of water in the fruit parts creates a conditions whereby water loss from the fruit can exceed water uptake. Under high evaporative conditions, transpiration losses from small fruit probably cause collapse of the sensitive, unstable tissues, resulting in BER. As you can see, the conditions influencing this disorder are complex.

BER is known to be more common during summer when excessive temperature rises may occur in greenhouses. Normally, calcium uptake and distribution is favored at night when humidity tends to increase and the rate of transpiration from the plant decreases markedly, thus allowing water and calcium to move into the low or non-transpiring tissues. This process is thought to be assisted by the increased xylem sap pressure that normally develops at night due to root activity. Shading of the crop to reduce temperature extremes has proven very effective in BER prevention in summer-grown pepper crops. Attention to EC levels is also of importance. Many researchers have shown a reduction in calcium uptake under high nutrient solution EC levels. For this reason, lowering EC levels during conditions that are conducive to water stress (i.e., high light and temperature), will also lower the incidence of BER. Cultivar selection is also important, as some varieties have greater BER resistance than others.