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ISSUE 3   May 18, 2000


    *As the spring flowering shrubs complete their bloom, and the fruit is of no ornamental value, they can be cut back if needed. This would include but not be limited to forsythia and lilacs.

    *Late blooming perennials can now be divided. Daylilies, Hosta, Rudbeckia, Echinacea, etc. Don’t divide spring bloomers like peonies now, wait until late summer or early fall.

    *Check crabapple, cherry trees, etc. for Eastern Tent caterpillar nests. They develop in the crotches of trees. They tend to rest during the day and crawl out at night to do their damage feeding on the foliage and developing fruit. Either pick them off or spray with an appropriate insecticide. Do not burn the nests out of the trees, as this will cause more damage than the caterpillars!

    *Having received a couple of calls on cankerworm (sometimes called "inch" worms) destruction, there are a couple of tactics available for control at this stage:

    1. Spray with Bt, which is a biological that makes them sick as the eat the foliage

    2. Spray with Sevin to kill them outright

    3. Ignore them. If this is the first such major attack, predators or disease will "discover" them. Besides, most normally healthy trees can tolerate a single defoliation. Re-leafing will occur later this spring.

    *If it has been a year since any fertilizer has been applied, then lightly sidedress perennials, including spring bulbs with a complete garden fertilizer like 5-10-5, or 10-10-10. There are many fertilizers to choose from, including slow-release types which are less likely to cause salt burn or damage to the plants. Avoid getting fertilizer on the center or crown of the perennials.

    *Finally, if you have resisted so far in fertilizing your lawn, congratulations! You may now fertilize your lawn, selecting a fertilizer with a ratio of N, P & K as close to a 3-2-1 as possible. An example would be an analysis of 30-10-5. The rate of application should be close to 1 pound of actual N/1000 square feet, or about 3.3 pounds of this material. A 50-pound bag would cover about 15,000 square feet, or about 1/3 of an acre.

Ron Smith
NDSU Extension Horticulturist and Turfgrass Specialist



    Forest tent caterpillar (FTC) feeding on green ash was reported in northeastern North Dakota last week. These reports are not surprising since substantial defoliation of basswood, oak, and aspen by FTC has been reported in Canada, Minnesota, and/or southeastern North Dakota in recent years.

    Forest tent caterpillars overwinter as fully developed larvae in egg cases which are laid in masses encircling small twigs. The tiny caterpillars emerge in early spring and can often be found first near the egg masses. Unlike other tent caterpillars, FTCs do not produce large, unattractive webs. The caterpillars do congregate on stems and branches during the day. Forest tent caterpillars feed on ash, aspen, basswood, birch, cottonwood, elm, maple, oak, poplar, and other hardwoods. As the larvae enlarge, keyhole-shaped spots along their backs and broad bluish lateral bands become evident. These markings
make identification relatively simple. Since the adults are moths which are attracted to lights, shutting off yard lights during late June and early to mid July may reduce the number of egg-laying adults attracted to areas where the larvae could become a nuisance the following year.

    Forest tent caterpillars did cause defoliation of aspen in parts of north-central and northeastern North Dakota several years ago and caused some defoliation of basswood and other hardwoods in southeastern North Dakota over the past three years. Most recent FTC reports in northern Minnesota and southeastern North Dakota have been of the defoliation of scattered clumps of trees. Most of the defoliated oaks and basswoods refoliated quickly, while aspen trees were slow to recover.
Healthy green ash should refoliate by mid summer.

    Outbreaks may last one to four years in North Dakota. It is difficult to determine how much damage the forest tent caterpillars will cause this year and during the next few years in the state. If treatments do become necessary, Bt can be effective when applied early. Bt works well to control young caterpillars, while permethrin, pyrethrins or other insecticides are needed for older larvae. Always follow pesticide labels.

Marcus Jackson
Extension Forester

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