Why are my Kentucky Wonder pole bean plant leaves turning yellow, developing...

Asked July 30, 2014, 1:59 PM EDT

Why are my Kentucky Wonder pole bean plant leaves turning yellow, developing brown/necrotic areas, drying up, dying and dropping. Typically one of the 3 leaves on a stem turns yellow before the other two start to turn. I have a very bad infestation of spider mites that I have been trying to control with insecticidal soap and horticultural oil without much success. It appears that I have red as well as black spider mites. I have also seen leafhoppers, whiteflies and flea beetles on occasion. The lower portions of the stems have reddish brown spotting (from the ground up approx. 4-5 inches). I pulled a stem out of the ground and do not notice any discoloration, rotting or nodules on the roots or part of the stem that was underground. I am not sure if all of the damage to the plants and the drastic leaf loss is due to the spider mites, or if the spider mites are secondary to some other disease process, as there are spider mites on every sick leaf that I exam. My pole bean leaves and problems do not look like any of the photos of bean diseases that I have seen. Some of the leaf damage and loss might also be due to multiple treatments for the spider mites, but there are so many that if I don't spray at least once a week with the oil and soap the mites will kill the plants anyway. Most of my plants have lost more than half of the bottom two thirds of their leaves and they lose more everyday. The top one third of the plants still look green, full and lush. The Kentucky Wonders have not begun to bloom yet. I have many chili pepper plants that are growing in the same garden beds as the pole beans and they are doing fine. This is the first year that I have attempted to grow beans. I have many photos of everything I have described and would like to be able to send more than 3. Can I save my pole beans? What should I do? Thank you in advance for any advice you can give, Jackie

Montgomery County Maryland

1 Response

The beans in the photo look like they were subject to spider mite damage. Spider mites like hot dry conditions. Soap and oil sprays can penetrate the tissue and cause more damage. AT this point hose the plants and leaf undersides with water. Keep the plant well watered and do not overfertilize which can increase mite populations. You do have the option of spraying the top portion (green leaves) of the plant with spinosad. Follow all label directions for control. See our vegetable profile for growing information on beans http://extension.umd.edu/learn/vegetable-profiles-beans
and spider mites