Raspberry And Apple Diagnosis: Powdery Mildew

Q: Each spring the leaves of my apple trees and raspberry bushes get orange spots on them. Soon after, the new growth is covered with a coating of what appears to be powdered sugar. I got a fungicide at a local nursery, but it didn't work.

A: It certainly sounds like your apples and raspberries were infected with powdery mildew, fungus organisms that attack the new growth on both species. A whitish-gray powdery coating on new leaves and stems; dwarfed, distorted and stunted new growth and even defoliation or die-back may all be symptoms of this disease.

Apply a lime sulfur spray to your raspberries in late winter just before or when the buds are beginning to expand. You may also need to use Benomyl regularly until the time fruit is set.

Apple scab can be controlled using sulfur, Benomyl or Funginex in a spray program during the bloom cycle. Spray at the pre-pink, pink and petal-fall stages and later, if necessary, as new growth might be attacked.

Yellowish spotting on raspberry leaves may be caused by a rust disease. This can also be controlled with a lime sulfur application at the green-tip stage of growth in spring.

Q: I have 20 fruit trees in the vicinity of ostrich pens. Are there natural substances I can spray on the trees that will not harm the birds?

A: Lime sulfur, wettable sulfur and fixed copper are fungicides made of naturally occurring elements, which are recommended for use to control scab and mildew on pome fruit and brown rot on stone fruit. In addition, WSU scientists suggest the use of lime sulfur, superior type oils, insecticidal soap and Bacillus thuringiensis (B.t., Dipel, Thuricide) for combatting various insect pests of fruit trees. Although all of these substances are fairly benign when it comes to vertebrate animals, they must always be used with caution.

Q: I pollinated some Thanksgiving cactus, as you described, and would now like to know when they will be ready for harvest. I'd like to start some new plants from seed. Also, my Kafir lilly has fruit on it and I don't know how to tell when they will be ripe. Do I let them dry before I plant the seeds?

A: The berries produced by your zygocactus plants (Thanksgiving, Christmas or crab's-claw cactus) should begin to color up by spring. They will usually hang on the plants for more than a year, and in fact will remain on them while they are flowering next fall, so your plants should be providing color from both fruit and flowers. The seeds are likely to be ripe and viable soon after the berries become fully colored. It would, however, be prudent to wait until the fruit begins to soften a bit before removing them from the plants and extracting the seed.

Kafir lilly or clivia seed is ready after the fruit has turned red and begins to split open. It would not be wise to wait till they dry before planting the seeds.

Gardening runs Friday in Scene and Sunday in Home/Real Estate. It is prepared by George Pinyuh and Holly Kennell, Washington State University/King County Cooperative Extension agents; Mary Robson, Master Gardener program assistant, and volunteer Master Gardeners.