Insects can cause a lot of damage
AZALEA LACEBUGS FIND A GOOD MEAL
Q: My azaleas are turning from green to white! I need to identify the problem and treat. Thank you for your help.
A: I think that is the most impressive azalea lacebug damage I have ever seen. Azalea lacebugs are tiny insects that feed on the undersurface of the leaf. Their wings look like lace. If you look closely at the back side of a leaf, you should be able to see them. The gritty spots are their droppings. As they feed, they suck sap out of the foliage, leaving behind some white specks on the upper surface. With repeated feeding, the leaves look bleached or bronzed. Once damaged, leaves will not green back up. The damaged leaves will eventually fall off, and new green leaves will take their place next year. Systemic insecticides applied immediately after flowering in the spring can help prevent another attack next year. Organic sprays of insecticidal soap will help, but consider where you have to direct the spray — the undersurface of the leaf. On large bushes, that is hard to do. Keep watering to help them survive this heat. Stressed plants can be more susceptible to damage.
MINOR ISSUES TURN OUT TO BE MINER DAMAGE
Q: I’m hoping you can advise me what I should do to help my camellia. It suffered greatly from the severe freeze we had here in Little Rock last winter. It lost all its leaves but finally started putting new ones on a few months ago. I have trimmed out the branches that have no new leaves, but now the new leaves have something damaging them. This photo shows some leaves (front and back). Is there any advice you can give me on what to do to stop the damage?
A: I sent the picture to Sherrie Smith, plant pathologist for the University of Arkansas Division of Agriculture Cooperative Extension Service. Although it looks like a disease, she said, it is primarily leaf miner damage. Leaf miners are tiny insects that feed between the layers of the leaves. It usually looks worse than it is; however, when miners attack an evergreen plant the damage lingers. It won’t kill a plant, but it doesn’t help it look its best. For deciduous trees and shrubs and evergreen plants, we recommend good sanitation, removing all the fallen leaves. Applying a systemic insecticide can help, too.
SCALE INSECTS STRIKE AGAIN
Q: I have several plumerias, and the lower trunks are all turning brown and looking like they aren’t getting water. You can see white spots on one, and they all have what kind-of look like, maybe, bug holes. Do they have an insect or fungus? They are all blooming at the top, but the wilt seems to be moving up the trunk. Any ideas?
A: Your plumeria is infested with scale insects. They suck the sap out of the stems of the plant and can infest the leaves as well. These scale insects are covered in a white, waxy, protective shell. You can wait for the weather to cool off and coat them with a horticultural oil, or apply a houseplant systemic insecticide. Even if the scale insects are killed, they will stay attached to the stems, but you should see increased vigor in the plants.
BROWN-EYED SUSANS CAN’T STAND UP AGAINST PROBABLE DISEASE
Q: Why did the all the buds not develop and bloom on my brown-eyed Susans? Should I deadhead the underdeveloped buds?
A: My guess on this one is a virus called aster yellows. But your foliage looks really healthy, so I am not sure. Aster yellows is a viral-like disease caused by a phytoplasma. Small insects that suck the sap of plants, especially the aster leafhopper, vector the disease. Aster yellows is a disease that affects more than 300 species of plants, including ornamentals such as asters, coneflowers, zinnias, marigolds, chrysanthemums, petunias and rudbeckia (like your brown-eyed Susans). Symptoms include misshapen flowers, chlorosis of the foliage and other deformities. Try cutting back all the unopened flowers and disposing of them. Then, see what happens. If it is aster yellows, you have to destroy the plant, as insects will feed on the damaged one and transfer the disease to other nearby plants. There is no cure for the disease. I would take a sample (a stem with unopened flowers and leaves) to your local county extension office for them to send to the UA Division of Agriculture disease lab for an accurate diagnosis.