Issue: February 17, 1997
Daffodils blooming too early?Question:
I saw flower buds on my daffodils the other day. It is still winter and I am worried that the flowers will freeze. What should I do to protect them?Answer:
Don't worry. The daffodils are appearing on schedule. They are very cold tolerant and will survive almost anything that winter can throw at them. It is important to keep them watered now so that their flower stalks will develop to full height. Those planted in warm, sunny, locations (especially on the south side of structures) will dry much faster than those in more protected locations. They will also bloom earlier so keep them watered, but not soggy.
Fat white worms in lawn.Question:
I found fat white worms under my grass. As I touched them with my shovel they curled up. They were a dirty white color with a gray spot near the end and a brown head and legs at the other end. What are they and do they do any harm?Answer:
You have described lawn grubs. These are the larvae of several beetles often called June beetles or chafers. The grubs are common pests in New Mexico lawns. There are several chemical and some non-chemical treatments available but this is not the proper time to treat for lawn grubs; however, it is wise to begin planning ahead.
A caution - one product often advertised for white grub control is not effective in New Mexico. That is the milky spore disease. It is not effective in New Mexico because the beetle larvae susceptible to this biological control measure do not exist in our state. The grubs common here are not susceptible to milky spore disease.
As the lawn greens in the spring, the damage done by the grubs during the fall and winter will become apparent, but now they are doing little damage and, because they are large, they are difficult to effectively treat. The proper time for treatment is usually in late July or August in New Mexico. This is when the eggs are just hatching and the young grubs are beginning to feed on the grass roots and crowns. This is also when they are most readily controlled. When you observe June beetles flying around porch or street lights in the summer, plan to treat for the grubs two to three weeks later.
There are numerous products to use, some chemical, some biological. You will find these products at your local nursery or available through some garden supply catalogs. The chemical treatments are more readily available locally, but you may find it necessary to order the biological control (parasitic nematodes) by mail. Plan ahead. While proper timing of treatment is important for most the effective control of grubs, the instructions on some products will tell you to treat before the eggs hatch while others have instructions to apply them just as the eggs are hatching or slightly after. Read and follow all the label directions.
There are many good lawn care companies familiar with the control of lawn grubs and you may choose to employ them to treat your grub problems. Whether you choose to control grubs yourself or hire someone, it is wise to check to see if your grub problems are severe enough to require treatment. To determine if there is a problem requiring treatment, cut several one-foot squares of sod and look under them for the grubs. Replace the sod after checking. A healthy lawn in New Mexico should be able to tolerate up to 15 grubs per square foot without showing injury. If the lawn is under stress from disease, drought, other insects, compacted soil, or heavy use, fewer grubs may cause injury even in New Mexico. Even though now is not a good time to treat for grubs, since you found some grubs, you can inspect to determine what level of infestation you have currently. This will help you make your plans for appropriate action in the summer. If you have a significant problem now, you are likely to have similar infestation levels after the new generation is produced.
By the way, two to four weeks after treatment you should again inspect the lawn to see if the treatment was effective. In the second inspection, you should find fewer grubs and those present should be discolored and lethargic.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
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