In this video, Extension field specialist Margaret Hagen describes controlling grubs in your home lawn. Read a full video transcript below.
Hello. I'm Margaret Hagan, a Field Specialist with the University of New Hampshire Cooperative Extension. Today we're going to talk about controlling grubs in the home lawn. Home lawns in New Hampshire are often severely injured by grubs - the larval stage of various beetles. European chafer and Japanese beetle grubs are the ones that cause the most severe damage to lawns in the Northeast. Other beetle larvae of Asiatic garden beetle and Oriental beetle can also cause occasional damage in home lawns.
Typically damage begins to show up in September and is evident through October. Grub damage is usually most severe on lawns facing South or in full sunlight. Heavy grub infestations can destroy grassroots allowing the sod to be rolled back just like a piece of carpet. Indication that grubs may be damaging your lawn are the presence of birds, moles and or skunks feeding in your lawn. Many homeowners first notice grub damage in the spring when the snow melts. Patches of dead or dying turf are especially visible at this time.
Knowing the life cycle of white grubs will help you time your control so it is most effective, saving you time, money and more damage to your lawn. The life cycles of the two beetles most likely to cause damage to your lawn, the European chafer and the Japanese beetle, are very similar. The adults fly in early summer and lay eggs in late June to late July. Larvae feed on turf roots from early July through mid Autumn and again in the Spring. Depending on which grub control you choose, applications should generally be made between late April and early August.
Preventive grub controls are the most effective, but keep in mind that the most common grub controls, like the Agway Grub Control that contains imidacloprid and the Scotts GrubEX that contains a acelepryn will control grubs early in the spring. They are preventive products that work very well on newly hatched grubs present in July, but do not work well for large grubs found from late September to May. Also, there are different recommended timings for application depending on the active ingredient. Although the bag often says apply any time from May to August 15th, it is highly recommended that products containing imidacloprid, thiamethoxam, halofenozide be applied and irrigated into the soil from mid-June to mid-July. If applied in early Spring they may move through the soil or partially degrade by the time the grubs hatch in late July. If applied too late they may not be effective as they work best on small grubs.
Products like GrubEXthat contain acelepryn are less water soluble so they take longer to move down to where the grubs are.
It can take 60 to 90 days for these products to fully dissolve in a soil. Because of this it's best to apply products containing acelepryn between late May and late June. That way it will be most effective when the grubs hatch in July in August. There are two chemicals Sevin and the DYLOX contained in this 24-hour Grub Killer Plus that are considered curative treatments.
These are short-lived compounds that kill all stages of the grubs. These two insecticides are the only options available if high numbers of grubs are found in the Fall and in the Spring before early May. They are not as effective as the preventive compounds in reducing grub numbers. Consider carefully whether it would be best to wait and apply a preventive later. Watering with a half inch of irrigation immediately after the application is essential to get effective results from these insecticides. Don't apply curative compounds in the spring after May 15th as the grubs stop feeding in late May as they prepare to become adult beetles.
Two biological control products that are presently in the market are milky spore disease and parasitic nematodes. In New England, due to our cooler soil temperatures milky spore disease has not been very effective in controlling white grubs. Another drawback to milky spore disease is that it's specific to Japanese beetle larvae and doesn't control the other species of beetles. In New Hampshire, remember the majority of damage to lawns is caused by larvae of the European Chafer. An alternative biological control on the market is parasitic nematodes. Reports on the effectiveness of nematodes have been mixed. If choosing parasitic nematodes for control, it is important to purchase the nematodes from a reputable supplier so they arrive fresh. Often nematodes are shipped directly to you, upon receiving your nematodes it's best to apply them right away. Nematodes must be kept moist. A good time to apply them is on a cloudy day or when a light rain is falling. Make sure you water these in well when you're finished.