Best time to seed and how to deal with bagworms
Q. I saw an article saying I can overseed my lawn during the winter. Is that true?
It's important to sow grass seed at the right times of the year in order to get the best germination for your investment. Fall is the best time, although many people do it in the spring.
Winter (or dormant) sowing of grass seed is usually only for areas that get snow that stays on the ground most of the winter. It requires getting the seed out before the soil freezes, but daytime temperatures are in the 40s.
In our area, frequent cooling and warming messes too much with germination. Seedlings sprout on a warm day and then get nipped a couple or few days later when bitter cold hits again, probably killing them.
For best results, stick with fall seeding if possible, or spring seeding if you could not get it done last fall.
Q. I have bagworms on two evergreen shrubs. How do I get rid of them?
The bagworm is easily identified by the dry, baglike cocoons made from needles of the evergreens they are hanging in. These cocoon bags look like deformed pine cones or little Christmas ornaments.
While the bags themselves are unsightly, the real problem is the damage wreaked by caterpillars as they defoliate the plant. If left unchecked, bagworm caterpillars strip away all the needles, stressing and weakening the plant enough to kill it.
The recommended advice for getting rid of a bagworm infestation is to pluck each bag/cocoon off the shrub from late fall to spring (roughly October to March), to interrupt the insect's lifecycle. This can be quite difficult with a large plant that may have dozens or even hundreds of bags hanging from its limbs.
Light infestations of bagworms on large, healthy trees are often not much of a problem, as birds and some insect predators will feast on the young caterpillars. Make your landscape bird-friendly and avoiding the use of pesticides that kill helpful insects.
Studies at the University of Illinois at UrbanaChampaign indicate flowers in the aster family (like shasta daisy, Newfoundland aster, and treasure flower or Gazania rigens to name just a few) near and/or around the susceptible tree will attract a major natural predator of bagworm, the ichneumonid wasp. These tiny wasp, which are harmless to humans, lay their eggs inside prey insects.
Bt (Bacillus thuringiensis) is a naturally occurring soil bacteria that causes the bagworm caterpillars to become sick and die, but is harmless to humans and pets. The best time to spray with Bt is when the young worms are hatching and emerging from the bags, usually in late May.
The use of synthetic chemical pesticides should be reserved for serious bagworm infestations on very valuable landscape trees. Recommended chemicals to control bagworms include acephate (Orthene), cyfluthrin, and spinosad, applied as sprays, all of which are highly toxic to bees and other helpful insects.
The lifecycle of the evergreen bagworm begins with the female adult insect which is a maggot-like, softbodied yellow-white worm that dwells within a bag she constructed while in her larval caterpillar stage. After laying 500 to 1000 eggs inside the bag, the female dies, and the eggs overwinter in the bag before hatching the following spring. In May and June, the larvae emerge from the egg as tiny caterpillars and begin to build their own bags around the lower part of their body, leaving its head and legs free to move about the plant and feed voraciously on foliage. If a branch becomes completely defoliated, the larvae will crawl away, dragging the attached bags, to attack another branch, or even move to a whole new plant.
By mid-August the bagworm has completed its growth; it attaches its bag to a limb, seals it, and begins the pupal transformation. By mid-September, the adult males emerge from the bags as black furry moths with feathery antennae and transparent wings. The female transforms into a maggot-like worm inside the bag, then awaits a male moth to mate with her through an opening in the bag. It lays eggs, then dies to begin the next generation — without ever leaving the bag it first constructed as a larval caterpillar.
Readers can pose questions or get more information by calling 417-874-2963 and talking to one of the trained volunteers staffing the Master Gardener Hotline at the University of Missouri Extension Center in Greene County located inside the Botanical Center, 2400 S. Scenic Ave., Springfield, MO 65807.