Archive for Tuesday, August 25, 1998


August 25, 1998


Grubs. What are they good for? Fishing!

Almost every shovel full of dirt contains something. Many kids anxiously turn over a spadeful looking for earthworms before heading off to the lake to fish. Many times, however, the tightly curled white grubs are also available. And while the fish might like them, gardeners recognize that an infestation of grubs can damage grass and plants as they feed on tender roots.

White grubs are the larval stages of the scarab beetle and nearly 200 species are found in Kansas. The most prevalent one is the southern masked chafer beetle. In July and August the beetles emerge from the soil, mate and deposit the eggs which hatch in two to three weeks. It is much easier to control grubs while they are small so now is one time to apply control.

Since grubs are in the soil, it is only when they have come in contact with insecticides that control occurs. Thatch can be detrimental by building up and preventing insecticides from soaking into the lawn. Power raking or verti-slicing are methods which help promote the flow of grub controls. If the season is dry, watering can drive grubs to the surface and will assist in the contact of the insecticide with the grub.

It is critical to be accurate with the application of insecticides. Label rates are sufficient to kill grubs. Over application is unnecessary and against the law. Excessive run-off can cause damage to domestic and wildlife animals. Underapplication probably won't get the job done.

Spreaders should be accurately calibrated for the application recommendations on the side of granular insecticides. Normal wear and tear on spreaders can alter flow rates. Sprayers should also be calibrated and checked for leaks. Worn nozzles should be replaced to ensure a uniform spray pattern. As always, protective clothing should be worn by the gardener and all applications should be applied on a calm day to prevent drifting.

Grubs can be killed by ``contact'' insecticides or stomach poisons. Trichlorfon is an active ingredient which can be found in both spray and granular form. Several companies distribute this type of control, so read the label.

Imidacloprid is an active ingredient in stomach poisons. ``Merit'' is a common name found on the label of these types of products. Unlike products recommended for ``rescue'' treatments which kill on contact, stomach poisons are used as ``preventive/insurance'' treatments. These products are taken into the plant via the root system and ingested by the grubs. Generally in eastern Kansas these products are applied from April through early July or 30 to 40 days after the flight of the chafer beetle.

Although children might like grubs for fishing, and moles might like them for eating, gardeners can save their flowers and grass by a little preventive maintenance.

-- The Garden Calendar is sponsored by K-State Research and Extension-Douglas County office and written this week by Master Gardener Pat Risley. For more information call the Master Gardener Hotline, 843-7058, from 1 p.m. to 4 p.m., Monday-Friday.

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