Alfalfa Weevils Make Their Mark

Historically, alfalfa weevils are not a widespread problem in North Dakota. However, 2012 is different. Until recently most growers have been blaming weather for the slow growth of their alfalfa crop. While the dry, early spring season may have slowed early development, the small weevil larvae certainly have had an impact in recent weeks as they feed in the terminal buds of the growing alfalfa.

The larvae are light green in color with a white stripe down the center of the back and about three-eighth to half an inch in length. At first, the feeding injury appears as small, circular holes in the leaves. As the larvae grow, the feeding injury is more evident. Severely damaged fields take on a silvery/gray to brown appearance.

The larvae soon drop to the ground and pupate into the adult stage which causes very little damage to a growing alfalfa plant. The adults and larvae prefer the shaded protection of the windrow. Following harvest, the adult will seek protection of adjacent sites that offer plant litter.

At this point in time, the best strategy is to cut the fields for an early hay crop. The damage has been done and little growth of the first crop will occur. Taking an early cut will stimulate the growth of a possible second cutting under dryland conditions. This strategy will definitely work under irrigation systems.

The adult weevil is about a quarter of an inch long with the typical weevil snout. It is brown in color with a darker brown to black stripe down the center.

Tree of the Week

How about considering European Mountain Ash (EMA)? There are several growing in Williston including those in front of the post office.

EMA offers some good seasonal colors. For most of the season this tree has a dull dark green leaf color which turns to a purplish-red fall color. In the spring, the tree produces a creamy-white flower color. These blossoms produce a cluster of bright orange berrylike fruits. Some people do not like these small berries because the fallen berries are somewhat difficult to gather and remove from the lawn. However, birds like the berries after a good fall freeze.

Don’t expect this tree to reach heights above 25 feet. Like other trees, it has problems of its own. EMA is a member of the Rose family, thus it is susceptible to fire blight. Also, as a young tree it has a sensitive smooth bark making it susceptible to sunscald. Wrapping the trunk during the tree’s early years will pretty much eliminate the sunscald problem.

EMA is not a native tree to North Dakota. Although it heralds from northern Asia and Europe, it does require supplemental water. Thus I suggest it be planted on boulevards and home landscapes where a water hose is close by. There are several varieties that vary in form from columnar to oval.