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Ask Dr. Hort: Banishing bugs that invade tomato plants

Banishing bugs that invade tomato plants

Q: Our tomato bushes are being invaded. On our Husky Cherry tomato, we have been plagued by black beetles. The biggest problem, however, is on our full-size tomatoes (Jet Star Hybrid), which are being attacked by loads of critters that seem to cluster on the surface of each tomato just as it's beginning to ripen. By the time they have moved on to a new tomato, we have the mere shell of the fruit left. What can we do? We do not generally spray any pesticides. Is there a natural remedy to our situation?

Gail Carroll, Belleair

A: Your beetles are probably flea beetles: less than 1/2 inch and black, iridescent blue or green. If they are munching on your plant, spray with products that contain Spinosad, an organic product that contains metabolites from the bacterium Saccharopolyspora spinosa. This is a new class of bug killers that works quite well against chewing insects and is very safe.

Now, for the big guys. You have the nymphs of leaf-footed bugs sucking the life out of your tomatoes. Bag the fruits in paper or try breathable veggie bags, so you can see ripeness. Spray with a product containing a pyrethroid (pyrethrin, cyfluthrin, permethrin). If that doesn't work, try Sevin, a carbamate. Either way, the product must come in contact with the bugs, which will scatter, so this is best accomplished in the morning when they're still half asleep. Be sure to follow label directions when applying a pesticide.

If you have plumeria, you'll likely have rust fungus

Q: I have a plumeria that was badly damaged in the January deep freeze but seemed to be recovering well with at least 25 bright, shiny new green leaves but no flowers. About a month ago I noticed small orange dots on the bottoms of many leaves. I was advised to use a fungicide. After two applications seven days apart, the plumeria lost half its leaves and I cut off two more that had a small, persistent orange dot on each. How did it get this fungus in the first place? Did I overwater? What can I do? I am obviously a novice gardener.

C. Novak, Palm Harbor

A: Novice gardener or not, if you have Plumeria spp., also known as frangipani, you are likely going to have rust fungus in the summertime. Now, how to manage it. There really aren't any fungicides labeled for the homeowner to use to fight rust, but some cultural things will help. Make sure your plant is in full sun, and keep it away from overhead irrigation. At the first sign of the bright yellow-orange spores on the bottom side of the leaf, remove and discard the leaf. Don't let these leaves fall and accumulate under the plant. Then make a formula of 1/2 teaspoon baking soda and 1/2 teaspoon horticultural oil per quart of water. Spray the clean leaves. This will act as a protectant and must be reapplied after every rain. You also can just let the leaves fall and discard them. Nothing you did caused the fungus problem; the microscopic spores are in the air.

Multiple cones on male sagos is unusual

Q: About 15 years ago we added three sagos to our landscaping. . . . The female sagos have taken a "rest" (they bloomed last year). The male sago has always produced a single cone; this year it produced multiple cones. Can you tell us how, or why, multiple cones occur on male sagos? We understand this is a rare occurrence and we would like to find out more about it.

Lili Garrett, Largo

A: The multiple heads are probably due to some cold damage while the bud was beginning to develop. Definitely picture-worthy!

Bacteria is common on wax begonias

Q: I have a beautiful angel wing begonia that is getting dead spots on the leaves. It seems to happen every summer when the plant gets a lot of sun. Other plants in the shade don't seem affected. Please tell me it's sunburn and not something worse.

Pam Purol, Tampa

A: You have a bacterial problem (xanthomonas begoniae), not sunburn. During hot, humid weather this disease is very common on wax begonias. Pick off and destroy infected leaves and redirect any sprinklers. If it continues, use a bactercide such as basic copper sulfate or products containing maneb, spraying on a weekly basis. Always follow label directions when applying pesticides.

m It's simply too hot now to grow tomatoes

If your tomato crop has taken a sudden turn for the worse, don't despair. It's that time of year.

Readers Gerri Hubbell of Port Richey, Maureen P. Carr of St. Pete Beach and Dwight Douglass of Holiday wrote about their tomato plant problems. For most, the problem wasn't with the plant, but with the fruit, which refused to set.

One answer covers all their issues: It's simply too hot. When the night temperature is high (75 to 85 degrees), tomato plants shut down and abort fruit set for survival. Also, high humidity (75 to 85 percent) interferes with the release of pollen and its ability to stick on the stigma (female flower part), compromising pollination.

Turn your efforts instead to planning your fall garden, which should be planted by Labor Day. Check out the calendar on this page for upcoming classes, and consult Vegetable Gardening in Florida by James M. Stephens, which can be purchased at local bookstores or online at

Roger Gingras of Seminole also asked about planting tomatoes in a container, which is a great idea. Fill it with Miracle-Gro or Pro-Mix planting mix. Remember, veggie gardens do best in full sun (six to eight hours). Also keep in mind, of course, that the days get shorter through fall and winter.

Need help?

Enter Greg "Dr. Hort" Charles, who for more than 30 years educated gardeners through the Pinellas Technical Education Centers. He 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, city and contact information. If possible, include a photo. We will print his advice on Saturdays in HomeLink.

Ask Dr. Hort: Banishing bugs that invade tomato plants 07/30/10 [Last modified: Thursday, July 29, 2010 4:20pm]
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