The 4-1-1 On Grub Control

TAKING CONTROL. Lawn care operators can use three approaches for managing grubs: preventive, curative and rescue treatments.

Ten to 15 years ago, grubs were treated solely through the curative approach when the pests were young or just hatched - typically late July and early August, Potter said.

But, during a cool year, the treatment window for curative control usually extends to the last two weeks of August and even the first week of September, targeted toward the first and second instar grubs, according to Shetlar. “A treatment at this time, while technically a curative application, should be called a rescue treatment because we are trying to stop any further damage and discourage any animal digging - quickly,” he said. “Because affected grubs do not die quickly after a rescue treatment, skunks and raccoons will continue digging. Therefore, this is why we recommend an application of a quick-acting insecticide like trichlorfon (Dylox) or diazinon (until existing stocks are used up).”

“During a curative approach, lawn care operators can typically go with a phosphate or carbamate in a liquid or granular form for control,” Potter added. “But they should also make sure to do post-treatment irrigation so the insecticide can be leeched into the soil. If the product is not watered in, you can lose up to 50 percent of active ingredient due to wind and other environmental elements. Adequate sprinkler systems should do the trick. Also, according to my data, 5 to 10 percent of the tests say liquid works better in a curative approach.”

While curative and rescue treatments are still practiced, Potter said these methods are going out of style due to the high risk associated with discovering and treating the grub infestation before pests reach the third instar stage, when they are large and cause significant turf damage.

Another drawback is that these methods typically mean additional costs for the customer, Buechner said. “When we do curative control, some seeding also has to be done due to the turf damage, therefore curative control costs clients roughly $40 more per 1,000 square feet,” he said.

However, curative treatments are still popular among clients and lawn care operators who believe in the integrated pest management approach to control, Buechner said.

The final grub treatment choice - preventive control - has been growing in popularity among lawn care operators because of new products on the market, such as Merit and Mach 2, that are specific to this control type.

Preventive control has a broader window of application that spans from late May through egg hatch in late July or the first or second week of August, Potter said. “So far, my tests have shown better than 94 percent control with this approach on annual grub species,” he said.

But preventive treatment involves applying the grub control product before a lawn care operator can sample the area for grub population, Shetlar pointed out.

Therefore, preventive control’s disadvantage is that some clients and lawn care operators oppose the use of pesticides before a problem is discovered, LaScalea said. “They only want us to treat their lawns when they have problems,” he explained.

But Potter insisted there are ways to integrate preventive control and IPM, such as:

• Target high risk sites first
• Keep records of grub activity
• Pay attention to adult beetle activity, which can foretell grub problems
• Use products with lower toxicity compounds

WHY GRUB TREATMENTS FAIL? Grub control methods can fail for many reasons. For instance, LaScalea said the type of turfgrass being treated can affect results. “Ninety percent of the turf in north Texas is Bermudagrass,” he said. “This turf recovers well from grub damage as long as it’s watered and fertilized heavily after treatment. But bluegrass and fescue do no recover well and typically need seeding or renovation, depending on the problem level.”

Following are some common reasons grub management programs fail and ways to correct them, based on information collected by Potter, Shetlar and Baxendale:

• Poor application timing - too early or late. For instance, larger grubs are harder to control, therefore treating too late may not result in a high level of control.



• No identification of grub species present. “Each grub species is active at slightly different times of the season,” Shetlar said. “Some grub species, especially European chafers and Oriental beetles, seem to be less susceptible to the new insecticides. Most entomologists are suggesting that when one of these pests is the main grub, apply Mach 2 or Merit at egg hatch - usually mid-May.”



• Too much thatch - It’s a barrier between the product and the grub, and should be managed before treatment. “If the thatch layer exceeds ½ inch, a light aerification and increased post-treatment irrigation will enhance insecticide penetration and should improve white grub control,” Baxendale said.



• Insufficient or lack of post application irrigation. The insecticides need to be moved to the soil-thatch interface, Shetlar said. “This is best accomplished by applying ½ to ¾ inches of water immediately after application,” Baxendale said. “Repeat irrigation every four or five days to continue moving the insecticide into the soil. This also keeps the crown and root area moist to encourage recovery of the turf. If conditions have been hot and dry and grubs are deeper in the soil, a pretreatment irrigation of ½ inches applied 48 hours before the insecticide application should encourage grubs to move closer to the soil surface and enhance the control level.”



• Incorrect rates and poor calibration. “This is specifically low application rates,” Shetlar said. “Merit and Mach 2 rates have been calculated so that there is no ‘fudge factors’ left to reduce their rates. Older grub insecticides could often be used at reduced rates, but don’t try it with Mach 2 or Merit.”