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!