Protect trees from weeds and pests

Control weeds while they’re small and easy to kill, so they don’t compete with the young trees.

In a new orchard, weeds have every condition they need to thrive and compete with the trees—full sun, regular moisture, and nutrients. Keep a sharp eye on the weeds right from the start because they can grow 4 to 12 inches in a week and the best time to control them is when they’re small enough to spray and kill with a relatively dilute solution of contact herbicide, says Tim Smith, Washington State University Extension educator for north central Washington.

“You have to be ready to go. If left alone for a few weeks, they’ll completely cover a young tree, and at that point, how are you going to control them? They go from being no problem to being a large problem in two to three weeks because once they get bigger they’re difficult to kill.”

He recommends a low concentration of herbicide, not just a low rate per acre, and says 2, 4-D should be avoided in the summer in young blocks.

Weed control is even more crucial with the smaller sleeping eyes and bench grafts because they are smaller than nursery trees. Smith said several residual herbicide products are available for use in nurseries, and the grower is in effect growing nursery trees when using those types of plants. “It may be an orchard, but you have to use nursery techniques.”

If using grow tubes, check frequently to make sure weeds aren’t growing inside the tubes.

Young trees need to be protected from herbicides where grow tubes are not used. Applying cheap white interior latex paint to the trunks is preferable to wrapping the base of the trunk with paper or plastic because of the risk of insects, such as the dogwood borer or apple clearwing moth, getting inside the wrapper and girdling the trunks. The paint also protects the tender young trees from sunscald in the winter.

Pests

The apple clearwing moth is a relatively new pest that has damaged young orchards in British Columbia, Canada, and has been found in northwestern ­Washington.

“Both of these insects love to attack small trees with graft unions that are above the ground, especially if the graft union is damaged in any way,” he warned.

The lack of sprays on young trees also leaves them ­vulnerable to leaf-feeding insects, such as caterpillars. Monitor for damage to make sure infestations don’t get out of hand, Smith advises.

A few aphids are nothing to worry about unless they infest more than the first four or five leaves on the shoot. Predators and parasites will do the job if you are patient, he said. “We haven’t been able to show they do a lot of damage to a young tree that’s otherwise healthy.”

Young trees are also particularly susceptible to ­damage by deer, elk, and voles.

Diseases

It’s important to control powdery mildew in a new orchard, but don’t overspray, Smith cautions. Every 10 to 14 days during a period of rapid growth on really sensitive varieties should be plenty. In a newly planted orchard, it is sufficient to spray alternate rows or even every third row because of the small size of the trees. Overspraying is a waste of money and can lead to resistance of mildew ­populations to fungicides.

Nursery trees on dwarfing rootstocks will often have flower buds when they’re planted, but they will bloom after the normal bloom period when the weather is warm. Fireblight infections can begin in these blossom clusters and easily kill vulnerable young trees.

“I’ve seen young, newly planted apple orchards ­devastated when they were near a source of fireblight and they had blossoms on them,” Smith said. “Every infected tree is basically a goner and has to be replaced.”

He recommends having a crew walk through the block to snip off blossom clusters to prevent infections during the first season. Spraying is not as effective, and the amount of labor it takes to clip off the blossoms is ­minimal, he said.

Typically, in mid- or late summer of the first year, the ground between the rows is smoothed off so grass seed can be planted for a cover crop. Smith said the grass is easier to establish in August than June or July because of less competition with weeds. The following spring, the grass should grow rapidly and be able to compete with weeds.