Warm weather brings out the best and worst in all of us,
including pests. Insect pests can be a re-occurring problem in any garden. With warm weather and plenty of water
available due to regular irrigating, insects can reproduce rapidly and can move
from being a minor nuisance to down-right destructive. There are many pests
that are common to gardens in this region and the WSU Chelan County Diagnosis
Clinic has seen all of them. One of the
most asked about pests according to Linda Sarratt, Master Diagnostician, are
cutworms.
There are many species of cutworm but all have essentially
the same life stages and tell-tale signs of destruction. Cutworms are the larvae of a small, brown,
nocturnal moth. The female moth may lay hundreds of eggs in the fall which can
over-winter on the soil surface or on low growing vegetation and plant residue
(in other words, the weeds you didn’t clean out of your garden in September and
October). When the larvae hatch in the
spring (timing of hatch out is moisture dependent), they begin to nibble away
at the surrounding vegetation and are particularly keen on asparagus, beans,
cabbage and other crucifers, carrots, celery, corn, lettuce, peas, peppers,
potatoes and tomatoes....really, the whole garden (sometimes even turfgrass,
depending on the species of cutworm). Signs of cutworm damage are classic. One day,
you will see a beautiful row of seedlings newly emerged and full of vigor. The
following day, you will notice several seedlings look like they have been ‘cut’
at the base. The upper portion of the seedling may be still partially attached
to its base but leaning at an exaggerated angle or it may be lying on the
ground next to the ‘stump’ which used to be its stem. The following day, more
seedlings will be missing. This cycle will continue until all seedlings have
been decimated.
So what can you do about this? If you think cutworms are the culprits at
play in your garden, the first step is to try and capture one for positive ID.
Cutworms feed at night and then hide under the surface of the soil during the
day. By running your finger around the damaged plant and stirring up the soil
to a depth of about ½ inch, oftentimes you will find the larvae (1/2” to 1.5”
in length is typical). Any larvae that you find should be destroyed.
Another technique is to put foil or cardboard collars around
newly transplanted seedlings. Creating
collars by cutting the bottom off of a compostable paper cup works well. The
cup can be slipped over the top of the seedling after the bottom is cut off and
then the base of the cup can be nestled down into the soil to a depth of about
1.5”. This acts as a physical barrier
between the cutworm and the seedling.
Additionally, diatomaceous earth (a non-toxic naturally
derived form of powdered silica) can be incorporated into the soil around newly
planted seedlings and can be sprinkled onto the plant itself. The diatomaceous
earth is a ‘death of a thousand cuts’ to small, soft-bodied pests like the cutworm.
Lastly, practice preventative maintenance by removing weeds
and other plant residue from the garden throughout the season but mainly in the
fall. This limits the places for females to lay eggs.
For more information on cutworms, the University of Minnesota
has put out an information sheet at the following web address, http://www.extension.umn.edu/garden/insects/find/cutworms-in-home-gardens/
If in doubt about the proper identification of an insect of
particular concern to your garden, the WSU Master Gardener Diagnosis Clinic is
open Mondays and Wednesdays from 1-4 PM at 400 Washington Street across from
the court house in Wenatchee and is free of charge to home-owners.
As always, happy gardening!
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