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Ask Dr. Hort: Oak scourge may be caterpillar

Oak scourge may be caterpillar

Q: We have three oak trees, and they seem to be losing their leaves. One is losing a lot, the one next to it is losing some leaves, and the one farthest away looks like it may be starting. After closer examination, the one that is losing a lot has tons of yellow worms on it. Do you know what my problem might be and how to fix it? Tina Ronspies, Palm Harbor

A: When caterpillars decide to take over a tree, they pretty much get their way. It is just odd for an outbreak now. Usually, every five to seven years, we have an outbreak of eastern tent caterpillars in the spring, not fall. It also doesn't match your yellow color. It could be the variable oak leaf caterpillar, which is 1 1/2 inches, yellow in color with a pink to red stripe down its back. When disturbed, it secretes formic acid, which can burn skin, so be careful. The tree will spring leaves again, so no need to spray.

Fertilizer will fix philodendron deficiencies

Q: I don't know the name of one of the plants in my back yard. You can see from the photograph I sent you that its leaves are turning yellow. Roger Gingras, Seminole

A: Your plant is a self-heading philodendron, Philodendron bipinnatifidum (shown at left in tip-top shape here in a file photo). It used to be called Philodendron selloum. Most of the philodendrons, which means tree hugger, are much more vinelike in nature and like to climb trees as they would in the rainforest to compete for light. The deficiencies are magnesium and potassium, both common to your plant. A good palm fertilizer will do the trick.

Punch through clay when planting

Q: I have dug up some sections where grass won't grow in a shady area to plant a shade-loving ground cover. I have found packed clay in some places. I stirred up the clay, and will be using some topsoil and manure. Should I be concerned about planting in the clay? W. Clarke

A: If you punch through the clay layer when planting, there is no problem because drainage is re-established. If you end up planting in clay, amending the hole with peat and washed builder's sand or play sand will help with drainage. No topsoil is needed (and in many cases you introduce weed seeds with top soil). I think it's great that you've given up with sod in the shade. Ground covers are much more rewarding.

Identifying citrus tree pests

Q: I have tangerine and orange trees and every year they get this waxy and wormlike marking on the leaf or its undercoating. There is also an aqua or light blue insect that I try to get rid of because I think it lays these yellow-type eggs on the new foliage. I have been forever cutting the damaged leaves and branches. Romeo Wright

A: If the leaves at the ends of the branches seem to be chewed or shredded around the outside of the leaves, you've probably got blue-green root weevils (take a sample to your local extension service for positive identification). The blue-green adults, 1/4 to 1/2 inch long, chew the leaves and then lay eggs on them. Grubs then hatch, fall to the ground and burrow into the soil, where they begin feeding on roots. As to the wormlike markings, those are from the citrus leaf miner, a small fly that lays her eggs there. After hatching, the insect mines its way in the leaf, leaving the telltale trails. Both, with large populations, can be quite injurious to the tree. Bayer Advanced Tree and Shrub Insect Control is a systemic product that will take care of both problems in one fell swoop. Read the label completely before applying.

Need help? Greg "Dr. Hort" Charles answers questions about landscape and garden pests. E-mail your questions to or to (put Dr. Hort in the subject line). Mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe your problem in full, and include your name and contact information. If possible, include a photo. We will print his advice on Saturdays in HomeLink.

Ask Dr. Hort: Oak scourge may be caterpillar 10/29/10 [Last modified: Friday, October 29, 2010 4:30am]
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