Thursday, July 15, 2010

Seed now and watch for cutworms

Now is the time to plant seeds of late summer and fall crops where earlier ones have been harvested. Chose 60 day or less crops (carrots, beets, bush beans, radishes, Swiss chard, New Zealand spinach) or ones that like to mature in cooler temperatures (lettuce, peas, spinach, kale, collards, Asian greens). Note that a nice option with greens is that they can be harvested at almost any stage of maturity in the event of a short growing season.

With a temperature in the nineties F, small seed will be hard to germinate Use seed germination fabric and water lightly but frequently.

One seed germination hazard that some people think is a spring but not summer pest in cutworms. Cutworms are caterpillars that cut and kill tender seedlings round the soil line.
The notorious "miller moth" that people in our area recognize in the adult flying form (photo above left) is Army cutworm in its larval caterpillar stage. (See above right photo).

Note that there are also climbing cutworms as the person who brought chomped basil leaves in for diagnosis today discovered. Beet armyworm (see photos adult left and larva right) is a climber active in mid to late summer that chews on a very wide variety of plants. Variegated cutworm is another (photos below).

Cutworms typically feed at night and hide in soil cracks, under dirt clods or seek other cover during the day. If you are going to find them, you have to go out after dark with a flashlight.

Cutworms are preyed upon by ground beetles, rove beetles, spiders, tachinid flies, parasitic wasps and other garden insects as well as toads and snakes. If natural enemies aren’t providing sufficient control, consider your weed situation. Cutworm moths are attracted to weeds for egg-laying.

Promote rapid seedling growth with good cultural practices (right amounts of water, loose soil, proper planting times, etc.) and use transplants. Transplants and older plants aren’t as tender and less likely to be damaged at the soil line. Note that climbing-type cutworms will find the tender leaves on top.

Protect tender transplants and seedlings with cutworm collars (cardboard, foil) or milk carton rings. Insecticide baits are available for cutworms. They are more targeted than whole-plant sprays which may kill beneficial insects as well as pests. Note that B.t. (Bacillus thuringiensis) natural insecticide is generally ineffective against cutworms.

Photo credit: Miller moth Whitney Cranshaw, CSU Extension; Army cutworm larva Frank Peairs, CSU Extension; Beet armyworm adult Merle Shepard & Gerald Carner & P.A.C. Ooi; Beet armyworm larva Frank Peairs, CSU Extension; Variegated cutworm adult Ian Kimber; Variegated cutworm larva Charles Olsen, USDA APHIS PPQ.

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