Skeletonizers make quick work of destroying grape leaves

Dealing with insects, whether they're good or bad, highlight the questions that have come across my desk this week.

Q: What is eating my grape leaves?

A: They are grape leaf skeletonizers. Turn over a few leaves and you'll find small, black-, yellow- and blue-striped caterpillars. They later mature into blue-black moths, which resemble wasps with featherlike antennae. Larvae feed side-by-side in groups devouring grape leaves rapidly, leaving only the veins. Soon only the "skeleton" of the leaf remains. Handpick and destroy any adults, larvae or eggs you see. Wear gloves, because the larvae are covered with stinging hairs that may cause skin irritation. Ask your nursery for the organic compound called Bt to control them.

Q: How can I get rid of the swarming bees in our tree?

A: Swarming bees have caused much concern this spring. There may be as many as 50,000 bees in a colony, consisting of a queen, sterile female workers, male drones and developing bees. The colony increases in size and eventually splits. A queen and group of workers leave the nest all at once, often landing on a nearby tree while scout bees seek a new nesting site. These bees are not usually aggressive in the swarming/resting stages because they do not have a home and offspring to defend. Leave them alone, and they'll soon move on.

Q: I see swarms of beelike bugs in our yard. I say beelike because they have similar coloring, but their bodies are thinner and longer. What are they?

A: These are good insects. They are hover flies or flower flies. They love aphids. They move in on plants heavily infested with aphids and deputize the females to lay eggs in a colony of aphids. They then refresh themselves on flowers, hence the name flower flies. Soon, larvae hatch and begin devouring aphids.

Q: My peach fruits look ugly with brown scarrings and bleeding resin on them. Do I remove them and are they diseased?

A: Western flower thrips caused this damage, and you'll also find it on nectarines. The fruit is still OK to eat. Horticulturist Bob Morris has found spinosad to give control, but begin spraying after petal fall next spring and continue spraying until harvest. As always, follow label directions.

Q: Can you give me a name of a reliable landscape contractor to put in my landscape?

A: I have to avoid this question, but the Southern Nevada Water Authority has a list of trained and certified landscape contractors with an emphasis on using water-conserving plants and irrigation systems. Go to www.snwa.com, and under "Find a Water-Smart Contractor," select a contractor. If you are a landscape contractor, go to the same website, and click on "Becoming a Water-Smart Contractor" to find out how you can become certified.

Q: What is the white fuzzy stuff on my euonymus?

A: It is powdery mildew that is a white, powdery substance on leaves and stems. It affects roses, euonymus, cucurbits, grapes, vegetables, fruit trees, penstemons and many other plants. It is abundant in our valley. The spores do not require moisture. They land on leaves and redirect nutrients from plants to themselves. In severe cases it covers leaves, blocking out sun-inhibiting plants to photosynthesize. It often occurs when we place sun-loving plants in the shade. Place plants where they get adequate sunlight and good air circulation. If you have a problem, take one part milk in nine parts of water and drench the infested area.

Q: What is the black soot on my mulberry limbs?

A: It is sooty canker. It occurs on many woody plants because of heavy pruning. Exposed, dry, thin bark eventually cracks and splits to reveal black, powdery spores. Branches die back to the canker anywhere on the tree, usually entering the tree via a wound. Pruning opens the door, either directly through the pruning cuts, or indirectly by exposing branches to sun scald. Prune out infected branches at least 12 inches below the canker. Do your major pruning during the winter, to prevent further sunscald injury. This fungus easily spreads on tools, so clean them with 10 percent bleach solution or rubbing alcohol after each cut.

Linn Mills writes a garden column each Sunday. You can reach him at linn.mills@springspreserve.org or call him at 822-7754.