E-Letter 2

Your response to the first Tech Help email was fantastic, we thank all of you who shared feedback about this support service. As stated in our first message, we want to respect your use of this electronic format and intend to send out messages that are time appropriate or when questions we are receiving indicate significant patterns of crop development are being experienced. The following message is in response to growers reporting problems with leaf distortion on poinsettias, we hope you find the information valuable.

Leaf distortion on developing foliage can be the result of several potential factors:
Thrips feeding can be one problem, and it may be worse this year as drought conditions impact host sites normally abundant outside greenhouses. Damage from thrips feeding produces leaf scaring and star shaped puckering that is very distinct. Fortunately there is no long term impact on the crop. Thrips are also quite selective in cultivar preferences; you can have heavily impacted plants directly next to plants that are free of symptoms. Thrips are easy to control on poinsettias and most sprays targeted for this pest will work.

Another distortion is commonly found on young shoots developing after the pinch. In this example the cause may be environmental stress affecting young, tender leaves. High light (and the heat it brings) develops leaves that are highly lobed. Adjustment of the environment is the most important response, usually through shade or periodic misting of the plants to mitigate stress conditions. No long term impact will be seen on the growth of the crop or future leaf expansion.

Another distortion that happens is initiated before pinching, although there are several potential causes. A common problem comes from overhead irrigation with fertilizers, especially those that contain phosphorous like 20-10-20. With this example, expect young leaves to be distorted and a characteristic reddish color in the damaged tissue. To correct, eliminate contact with the fertilizer or at very least rinsing off foliage after watering. The new growth and young shoots that develop after pinch typically are free of any symptoms.

The other option is seen as stress on plants becomes significant. Sensitivity is diverse within cultivars, but plants like Freedom Pink, Redberry Punch and Max Red are a few from Ecke that have exhibited symptoms in the past. In this example, leaves take on a strapped shape that is thick in texture, preventing normal expansion. Plants become stunted and when pinched, shoots are slow to develop. When growers do not respond to what is happening and irrigate, fertilize and even growth regulate these plants in the same way required for normal crop development problems with root rot, high salts and severe stunting are the result! The best way to correct this problem is to adjust the climate on these cultivars (more shade, less fertilizer, adjusted irrigation schedule, syringing of plants during heat of day) and treat appropriate to the growth. Do not try to hold these plants to the normal plants regime until they have recovered and are once again actively growing.

We hope this information helps describe what we are hearing from growers as well as give you some ideas on how to help deal with symptoms of leaf distortion that you may find in your greenhouse at this stage of the crop. Ecke Ranch Tech Help.