Tom MacCubbin: Pesky mite populations hard to control.

Question: Stems of my tomato plants are being covered by mites so that portions have an orange color. I have tried a few products with little effect. What is a good control?

Answer: Heavy mite populations are hard to control, and there are only a few miticides for garden use. Also, when these tiny arachnids are so numerous that you see their orange color or in some cases webs, the plant is probably lost and should be removed.

Still, you might give a miticide a try and especially to protect plants where little damage is noted. Products available for use in the home vegetable garden with mites listed on the label include horticultural oils, insecticidal soaps and sulfur-containing pest controls. In most cases, it is important to hit the mites with the sprays and make repeat treatments as noted on the labels. Making treatments when the mites are first noted is the secret to good control.

Q: My bougainvillea has holes in the leaves and small, round, black droppings on the remaining portions, but I don’t see a pest. What is making the holes?

A: Look a bit closer on the underside of the leaves where you see the chewing. Bougainvillea caterpillars are likely feeding and leaving their excreta behind. Sometimes the pests are sneaky and drop from the leaves when they know you are examining the foliage. If only a few in number, they can be hand-picked from the plants and destroyed. Otherwise, you may want to use a natural spray of Thuricide or a spinosad-containing insecticide following label instructions. Both can be found at independent garden centers.

Q: Our mandarin and grapefruit trees have leaves that are curled on the ends with some browning. I have used an insecticide and fertilized the trees. What else should I do?

A: You are giving these trees good care, but you are probably missing the best time to control the citrus leaf miner. By the time you see the damage, the leaf miners, which also makes tunnels in the foliage, have completed their life cycle and wait for the next flush of growth.

Citrus leaf miner insects begin as moths that lay their eggs when new leaves are less than an inch long. Timing is critical, and insecticides should be applied when new growth is first noted. Use of a horticultural oil spray or a natural insecticide containing spinosad can give good control, if you follow label instructions. Most likely, all the damage won’t be stopped, but you should have plenty of healthy leaves too.

Q: I planted paper white narcissus bulbs in the ground that have flowered and produced tall leaf portions that have fallen over. What should I do with the floppy tops?

A: Gardeners who are a bit optimistic and hope their paper whites flower again should allow the tops to grow and only cut them back to the ground as they yellow and decline. These easy to flower bulbs give a good display the first year, but are reluctant bloomers another. If you are in a colder location, you have the best chance of seeing winter blooms next year, otherwise, the plants are likely to only produce foliage. If you don’t expect a

repeat bloom next year, cut the tops back or treat the bulbs as annuals and remove them from the garden.

Q: I am noticing grub worms in my lawns. What should I do?

A: Grubs make good fishing bait, so you might dig a few and head out to a nearby lake to bring home supper. Otherwise, if using them for bait is not in your future, some control in the lawn is likely needed. Grubs, often called white grubs, are the immature stage of beetles. They feed on grass and other plant roots until they mature into the beetle stage, often by mid-to-late spring.

Control is best achieved after eggs are laid in the ground by the beetles around late spring or early summer. Several grub control lawn insecticides are available at local garden centers to use at that time. Later in the year, when the grubs are large and still growing, a special insecticide is needed that can penetrate the soil to control the immature stages. The insecticide Dylox is recommended by the University of Florida and found in Bayer 24 Hour Grub Killer Plus Granules at local garden centers. Follow label instructions for proper and best control.

Q: My mangoes have started to bloom. When is the best time to fertilize these trees?

A: A series of mild winters have found many Central Florida residents with fruiting mango trees. Let’s hope this trend continues and some good care helps produce your crop. Make a fertilizer application in late February, June and October. Most garden centers offer a citrus, avocado and mango fertilizer to use; follow label instructions. Make the application under the spread of the roots and out past the dripline of the limbs.

Tom MacCubbin is an urban horticulturist emeritus with the University of Florida Cooperative Extension Service. Write him: Orlando Sentinel, P.O. Box 2833, Orlando FL 32802. Email: TomMac1996@aol.com. Blog with Tom at OrlandoSentinel.com/tomdigs.