Now’s the Time for Spraying Peach Trees
After this past week’s storms, there is no doubt that winter is here. Everything got wet and cold, knocking the last of the leaves off deciduous trees and soaking the garden until it was too wet to work. But there are special winter chores to do, so get out the rubber boots because the first on the list can’t be put off.
Peaches must be sprayed with a fungicide to prevent peach leaf curl, an all too common disease. This is the time of the year that this fungus gets started, but it can be easily controlled at this point by spraying with either fixed copper or lime sulfur. Because neither is particularly hazardous, they can be applied with a hose-end sprayer.
While you’re at it, you might get a dormant oil spray that also contains one of these fungicides. This traditional spray does not work as an insect poison, but smothers insects and their eggs--though it is especially valuable for the control of mites. Where are the critters at this time of the year since the leaves have fallen? Hiding in cracks in the bark or wherever they can find winter shelter on the tree. Should any of the oil get on evergreen plants, just hose them off when you’re finished--this is not the same kind of oil you put in your car, but a very light version that looks more like water.
For peaches, a second application of fungicide should follow in about four weeks, and perhaps a third four weeks after that, if you have had problems with this disease.
Whitefly update: Will a dormant oil help control the new ash whitefly that has been in the news so much? Probably not. It seems to overwinter on evergreen plants and on fallen leaves, surviving as an inactive late-stage nymph. It might help to clean up all fallen leaves and send them to the dump, but come next summer, they will probably be back in even greater numbers.
Will they survive the winter? Unfortunately, most definitely, because this is a temperate-zone whitefly, the first to come to California (the other five or six introduced whiteflies are tropical or subtropical), and it can survive in quite cold climates (it is native to Ireland and Poland, among other places).
No chemical control has been found to be very effective and the best hope is for researchers to bring over beneficial insects from Europe to help in its control. In Europe, it is not considered a major pest because it is, apparently, kept under control by predators.
The Los Angeles County Board of Supervisors is considering funding such an effort, and it certainly wouldn’t hurt to let them know your concerns. The best guess is that it will take about $50,000, which seems a small price to pay.
It is not as yet considered a major pest here, despite the fact that in some parts of town they are so numerous that it appears to be snowing. But they actually don’t do that much damage to a plant, though they are a definite nuisance and could, with time, harm trees.
They are also not the first introduced whitefly, and whenever a new one shows up, it is quite numerous at first. Researchers have said, “it’s snowing whiteflies again” several times.
Ash trees, pomegranates, apricots and pears, including the evergreen ornamental kinds, are the most susceptible. The whiteflies found on citrus are another sort: the woolly whitefly, which becomes most numerous in late fall and early winter, then subsides as predators get the upper hand. They look like they are named--a woolly mass under the leaves.
The flurry of ash whiteflies is probably over for the winter, but expect them back by summer.
Medflies and malathion: Medflies are considered a very serious threat, and the aerial spraying that is part of their control has prompted some gardeners to ask, “What else is being killed by the malathion?” The county agricultural commissioner’s office says the malathion is mixed with a protein bait so it only attracts medflies or similar plant pests, not beneficial insects, not even whiteflies.
Some gardeners who have put out those sticky yellow traps designed for whiteflies have ended up catching medflies too, and so have some people who have been painting their houses. These are the sterile medflies, another part of the control program.
Other winter work: After spraying and raking up the leaves, you can start pruning deciduous fruit trees, because some flower very early in the year, and near the coast, you can start on the roses too, but wait until later if you’re farther inland where a freeze might catch the new foliage that results.
Bare root fruit trees and roses begin showing up at nurseries now, though many nurseries wait to put them out after Christmas. But if you want the best selection, this is the time to start looking. As soon as the ground dries enough, dig the holes where you plan to put the bare-root plants. Many experts recommend digging the holes in advance so the plants can go in the ground as soon as they are purchased.
And, now it is time to plant those tulips that have been in the refrigerator since early fall.
