Frequently Asked Questions: Pests

My camellia leaves have yellow markings on the upper leaf surface and under the leaf is a white growth. Is this an insect or disease?

This is an insect called Tea Scale, which is the worst pest on camellias. Oil sprays which suffocate the insects or systemic insecticides are recommended.

My poinsettia is showing spots on the foliage and creamy colored scab-like lesions on the stem. What is this and how can I get rid of it?

This is a fungus disease called Poinsettia Scab. The disease tissue must be pruned off. New growth should be sprayed with fungicides that include Maneb or Mancozeb. Severely damaged plants should be removed.

My roses have black and yellow spots on the leaves and the leaves drop off the plant. How do I treat this?

'Black spot' is the most common leaf disease of roses. The disease thrives when the foliage stays wet for 6 hours or longer. It is spread by splashing rain or irrigation. Control is accomplished by keeping the foliage dry (use drip or micro-spray irrigation) and spraying frequently with a recommended fungicide (there are many). Successful rose grower's alternate between 2 or 3 fungicides.

Return to top

The trunk of my oak tree is covered with a silky web and there are little tiny insects under this web. How do I get rid of these before they kill my tree?

These insects are called psocids (pronounced "so-sids"). They do not damage plants; they feed only on organic matter that is trapped in the crevices of the bark. Once these insects are mature, they will move out of their protective webbing. No control measures are necessary. If they are unsightly, spray the webbing with a strong spray of water to destroy it and disperse the insects.

Return to top

My oleander is covered with reddish-orange colored worms with black hairs. They are eating all the leaves. How can I control them?

The eggs of the oleander caterpillar are laid on the new, tender growth. When the eggs hatch, the tiny worms cluster and feed on the branch tips. They can be easily controlled at this stage by simply pruning off these branch tips before the worms mature and migrate throughout the entire shrub.

Return to top

It looks like something is pruning off the twigs on my maple tree (also occurs on other trees).  Everyday I find more twigs under the tree and they have all been cleanly cut. What is doing this?

An insect called "twig girdler" is the culprit. It lays its eggs into the twigs of popular trees like maple, oak, pine and pecan, then chews the twig off so it drops to the ground where the life cycle of the insect will be completed. The only control measure to take is to clean up the fallen twigs and dispose of them. This eliminates the next generation.

Return to top

My crape myrtle has a powdery-like substance on the leaf surface. The leaves then curl up and die.

This a fungus called "powdery mildew." Crape myrtle is very susceptible to this disease. Good ventilation around the plant and weekly applications of a fungicide throughout the growing season may be necessary. New hybrids of crape myrtle are resistant to this disease.

Return to top

The bark on my Chinese elm is splitting and peeling off, and it is orange where the bark has come off.  Is this a disease?

Splitting and peeling bark and variation in bark color on Chinese elm and other plants like crape myrtle and sycamore is normal and needs no treatment.

Return to top

My azaleas and sycamore leaves have a bleached-out appearance and the undersides of the leaves are covered with tiny, shiny, black tar-like spots. What causes this?

Both azaleas and sycamore are susceptible to an insect called lace bug. Damage results from the insect sucking out cell sap, resulting in mottling of leaves. The black tar spots are actually insect excrement. Control on sycamore may be impractical if the trees are large. If no action is taken, the trees will defoliate early. No permanent damage will result. Azaleas should be sprayed with an appropriate insecticide.  Note: Azaleas in full sun are more frequently attacked by this insect than azaleas in the shade.

Return to top

I have a stand of pines on my property.  One after another the trees are turning brown and dying. There is sawdust at the base of the tree and sap on the trunk.  Can I save my trees?

Ips beetle and other pine borers are serious pests of pines and other trees. However, they only attack trees weakened by natural or manmade conditions such as drought, lightning or construction damage. The adult beetle attacks the pine by chewing through the bark and laying her eggs. The young larvae feed on the cambium tissue, which girdles and kills the tree. Insecticide sprays on the trunk will probably not save the tree because of the pre-existing stress. The best protection is to keep trees healthy.

Return to top