Something is wrong with my redbud tree. One large branch appears to be dead. Could you tell me what might be the cause and if I should remove the branch?
Don MacMillan, Gold River
According to UC Master Gardener Veronica Simpson, crown rot is a disorder that affects redbuds, especially if they are planted in lawns. That may be what's ailing your tree.
Infected mature plants grow slowly and may gradually decline. Leaves discolor, stunt, wilt or drop prematurely.
Trees also may die from crown rot. Roots look dark and decayed. Twigs and branches die back and the entire plant can be killed.
Another possibility is verticillium wilt, a soil-dwelling fungus that infects through roots. Leaves fade, yellow, brown or wilt, often scattered throughout the canopy. Branches die. The entire plant eventually may die.
Good drainage is essential for redbuds. Lawn trees with crown rot may recover if the soil and grass is removed from around the trunk and out about 18 inches.
For your tree, remove the branch and any dead twigs. Gradually reduce irrigation to infrequent deep watering. The water should penetrate to a depth of 12 to 18 inches, and you should not water again until the soil is dry. Use a probe to check soil moisture.
Do you know how to rid tomato plants of whiteflies? I had them at the end of the tomato season last year, but I have seen a few flying around my plants already. I do not want to use any store-bought chemicals.
Susan Patchett, Folsom
Whiteflies are truly annoying. According to UC Master Gardener Carol Rogala, they develop rapidly in warm weather, and management of heavy whitefly infestations is very difficult.
Whiteflies are not well controlled with any available insecticides. The best strategy is to prevent problems from developing in your garden to the extent possible.
In many situations, natural enemies will provide adequate control of whiteflies. Avoiding the use of insecticides that kill natural enemies is a very important aspect of whitefly management.
In the early stages of population development, whiteflies can be held down by a vigilant program of removing infested leaves, vacuuming adults or hosing down plants with water sprays.
Aluminum foil or reflective mulches can repel whiteflies from vegetable gardens. Sticky traps can be used to monitor or, at high levels, reduce whitefly numbers.
If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. For more detailed information, please refer to the UC IPM Pest Note 7401 on Whiteflies. Find it at www.ipm.ucdavis.edu.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.
Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:
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