Q: Last fall I failed to apply a disease-control fungicide to my peach and nectarine trees. Is there anything I can do in the spring? -- D.W., Redlands
A: You can get good results by treating the trees just when their buds start to swell in the spring. When peach blight is causing cankers that produce gum on the twigs, use Bordeaux, ferbam or ziram. Ferbam is preferred for peach leaf curl, which results in clumps of distorted leaves and poor-quality fruit.
Q: What can be done to keep an olive tree from setting fruit? Falling olives stain my walk, and I am allergic to the pollen. --F.H., Canoga Park
A: If you want to keep the tree, you'll need to apply a fruit-set inhibitor (such as naphthaleneacetic acid) to the bloom. A relatively new variety of olive tree, 'Majestic Beauty,' does not develop mature fruit. Ask for it at your nursery.
Q: What plants can be intermixed with vegetables to repel pests such as tomato worms, spider mites, borers and whiteflies.--R.I., Manhattan Beach
A: Tests conducted over the years indicate that planting garlic, onions and marigolds (or any other kinds of plants) among vegetables has no effect in reducing pest populations. Avoiding overuse of insecticides will permit efficient resident parasites and predators to eliminate a good number of pests. Introducing such beneficial insects as ladybird beetles does little to augment the work of resident beneficial insects. For tomato worms, you'd probably do best to pick them off by hand.