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Ask Dr. Hort: Serious disease killing palm trees

A serious disease is killing palms

Q: We have noticed a lot of queen palms dying. Is there a new disease killing them? Thanks. Deb

A: Both queen and Washingtonian palms are susceptible to Fusarium oxysporum, a fungus that flat-out kills the two palms, and there is NO control, either biological or chemical. The symptoms start with the lowest fronds turning yellow, then brown, on half of the petiole, the stem that supports the leaves, with a brown stripe down the center of the petiole. It goes from this early stage to the whole crown turning brown.

The entire progression takes only two months. Trees need to be cut down as soon as the first symptoms are noticed. Be sure to sterilize tools, equipment and chains after removal, because this disease can be easily spread to healthy trees through exposure to pruning equipment. See images online by searching Fusarium Decline of Queen Palms and Mexican Fan Palms in Florida.

Two readers wrapped in one web

Q: There are webs on the branches coming out of the trunk on one of my crape myrtle trees. I have never seen this before. In fact, I have also noticed that there have been a lot of webs all over my yard this summer. What are they? Jane Norton, Dunedin

Q: What is growing on my 9-year-old Australian tree fern? This is the first time I've ever seen this. I hosed it off about two months ago, but it came back. Paula Messina

A: Although this topic has been explored before, for folks just noticing the webbing, it's caused by psocids, gray or brown soft-bodied insects about 3/16 inch long with chewing mouthparts. They feed on pollen, fungi, lichens, dead plant parts (such as bark) and other organic material, which is why they are called "bark lice." Psocids construct a fine silken web on tree trunks and large branches. This web protects the maturing insects from rain and predators. The webs may look unsightly, but neither the insect nor its web causes any damage and are usually observed each summer. There is no need for concern or control.

Beware the hornworm

Q: This is my first try at gardening in Florida. What is eating my tomatoes? I found a grayish-beige caterpillar with fake black eyes on one but am unable to identify it. Thank you. Fredi Prager

A: Tomatoes are a favorite of hornworms and their relatives, which become as big as your pinky finger and can eat like a teenager. Bacillus thuringiensis (Bt) is a bacterium, harmless to humans and pets, but deadly to caterpillars. Products such as Dipel or Thuricide contain the bacterium, and when applied when caterpillars are small it is very effective. Vigilance is key. Monitor daily, looking for frass (caterpillar poop), black roundish balls, about 1/8 inch or smaller (the bigger the frass, the larger the caterpillar). You also may see chewed areas on the leaves or fruit. If you miss them when they are small, then hand-picking is your means of control.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe the problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: Serious disease killing palm trees

08/13/11 [Last modified: Friday, August 12, 2011 3:27pm]
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