In the past I have only sprayed Ca once on Prestige. This year I didn't because the calcium levels in the leaves were low, but not terribly low like they have been in the past. Well, I am seeing some tip burn show up. They are about 7-10 days from being mature. Will I gain anything spraying Ca this late? If so, what rate should I use? I did apply Decree last week and am circulating air to keep botrytis conditions minimal. Thanks.

Greenthumb -

Bract edge burn is basically a localized calcium deficiency to the bracts. Most of the time bract edge burn may not even show up on the plants while they are in the greenhouse environment but will surface in the retail environment or for the consumer. Basically as the plants age or become past their prime the bract edge burn can become worse.

It isn't too late to get a couple of sprays in because you can make them at weekly intervals and it will prevent the burn from becoming worse and progressing. Rates for calcium chloride sprays are 200-400 ppm.

The same conditions that promote botrytis also promote bract edge burn so controlling relative humidity and providing good airflow will also help. Good luck.....

Greenthumb, in our work with Prestige what we have seen is that it often will show some signs of bract edge burn (BEB). However, the problem is not too widespread and does not take out entire plant. I have not actually done Ca sprays on Prestige. With other varieties, we find that there is some benefit from doing two sprays compared to none. In some trials 400 ppm is better than 200 and in other trials it is not. So - do the sprays and use 400 ppm Ca. Then do all you can with environment control.

In review, in sensitive varieties, there is a strong relationship between fertilizer level during bract expansion and BEB. The higher the ammoniacal –N levels and/or potassium levels the more severe the BEB. These are + ions that compete with Ca uptake. Also, cultural and environmental conditions that promote large bract size and rapid bract expansion increase the chance of having BEB. Ca moves in the water moving through the plant. Bracts have relatively few stomates and less water moves through them. Thus, less Ca is accumulated in the bract tissue. We have found there is often little relationship between Ca levels in media or even lower leaves and the Ca levels in bracts. BEB can occur even when CA levels seem adequate. If a grower is in a situation where BEB might be a problem, we then suggest the Ca sprays to increase concentrations in the bracts. The sprays should start with first color and be applied weekly. Often actual tissue collapse from Ca deficiency is not seen, but the weaker tissue allows direct invasion by Botrytis. The bluing in the bracts is Botrytis advancing in the tissue and it is actually the Botrytis that takes out the bract.

Good luck with the crop. Jim