Plant Diseases/spider mites on Burford Holly bushes
We have sprayed with soapy water - let stand 15 minutes and hosed off. One set of these hollies look damaged w/ black "mold" looking stems and dying leaves. Can we cut them back and will they come back next year from the roots? When is the best time to cut back or should we just pull them out and plant new in the fall? We live in the Nashville, TN area. Thank you.
Dear Lynne, It almost sounds like you have scale and spider mites on your holly bushes. The black sooty mold is often left behind by scale insects which are unmoving insects that are protected by a hard shell or scale covering. They can be found on the bottom or tops of the leaves, or along the stems, depending on the type. I wouldn't recommend cutting them down to the roots, or pulling and replanting, because you are likely to be attacked by the same insects. I do have remedies for both scale and spider mites. To cure spider mites, you will need to spray with a product containing NEEM. NEEM is an organic ingredient that is effective in killing insects, fungus, and spider mites. You can find it in many garden products, since now organics are used whenever possible. To kill the scale, you should spray with a horticultural oil - lightweight or dormant oil. Do NOT use cooking oil; that only works for sautéing vegetables. The good news is that you can mix the oil and the NEEM together and spray the plants at once. Spray very thoroughly from the top and from the bottom, coating both sides of the leaves and the stems until the plants completely drip. Don't wash it off afterwards, but allow to dry. It's best to spray when the weather is warm (over 60 degrees), and either cloudy or there are no flowers on the plants (to avoid spraying bees). You may need to spray three or four times about a week apart to make sure that the bugs are gone. You will know that the scale is gone when a moderate stream of water will dislodge the bumps off the plant. In the event that you don't have scale, the oil will remove the sooty mold residue which prevents the plant from getting adequate light. To see if you have any spider mites left, hold a white sheet of paper underneath a leaf or small branch and tap the plant sharply a few times. If you see anything crawling around, you still have spider mites. I hope this information helps. Don't be too discouraged, because this is very treatable. I see a surprising number of hollies that become infested over the winter months, but since you now know what to do, you can cure yours. Good luck, and let me know if you have further questions. Melissa