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News & Press: Industry News

Handling Late Season Grub & Animal Problems

Monday, December 5, 2016  
Posted by: Maureen Plank
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By David Shetlar (the BugDoc)

Professor of Urban Landscape Entomology
Dept of Entomology, The Ohio State University(OSU Extension and OARDC)

 

  

While I have been predicting major grub problems across Ohio all year, many lawn care companies are just now realizing the extent of the problem! In many areas, grub activity was masked by a hot and dry period that ran from mid-July into mid-September. Many lawns were dormant and the grubs were hanging low in the soil profile until more conducive conditions (meaning moisture) returned. Even without frequent rains, much of turf that had gone into heat and drought dormancy began to grow out when cooler night temperatures arrived. Where this didn’t occur, many just though that rains would solve this problem. In many cases, it was the presence of white grubs that was keeping the turf from greening up!

 

Lawn care specialists and homeowners alike are now “discovering” grubs in Ohio lawns. In many cases, it’s the skunks and raccoons that are revealing the issue, but simply assuming that animal digging means you have grubs can be a mistake! In fact, I had an organic lawn care technician inquire about why something was digging in a lawn when they couldn’t find any grubs!? He said that the lawn was quite lush and was growing nicely! I had to chuckle when I asked him if there were earthworms evident. His answer was, “Yes! We specifically design our program to be earthworm friendly!” Big nightcrawlers are considered to be a delicacy by skunks and raccoons! However, when these animals are going after nightcrawlers at night, they usually only make small cone-shaped pits or they simply mash down the turf in a small spot. When going after grubs, they can either roto-till the turf (usually skunks) or they can roll back the loose sod (usually raccoons).

 

For folks needing a “rescue” treatment to control white grubs and/or stop animal digging, I recommend a “best practices procedure.” First, make sure there are grubs present! Second, are the grubs a white color or have they taken on a light, buttery-yellow color? If white, they are likely still feeding and a stomach insecticide will work. If some of the grubs have turned yellowish, they may have stopped feeding for the fall season, so a contact insecticide would be better.

 

Once you have determined if the grubs are still feeding or not, you need to assess the thatch and soil moisture. If you can take some of the soil and make a ball that holds together, it is moist. If the soil doesn’t make a ball but falls apart, pre-irrigation will improve the success of your insecticide treatment. In dry conditions, I recommend irrigating sufficiently to moisten the top inch of soil. This usually requires 3/8 to 1/2-inch of irrigation. Use pans or containers to determine when this amount of water has been applied! Oh, while assessing the soil moisture, how thick is the thatch and is it “layered” or “fluffy?” If you have 1/2-inch of layered thatch or more, you will likely have real trouble getting any insecticide through!

Now that you have determined that the soil is moist and the thatch isn’t too thick, which insecticide should be used? If the grubs are actively feeding, most of the neonicotinoids should still kill the grubs (i.e., imidacloprid, thiamethoxam, clothianidin, or dinotefuran). Imidacloprid and thiamethoxam products take the longest to kill the grubs, often 7-10 days though the application will usually stop feeding immediately. Clothianidin and dinotefuran products cause the grubs to turn brown fast, often in less than five days. If you suspect that the grubs have stopped feeding, then Dylox or Sevin should be considered as both have significant contact toxicity. Dylox is water soluble and moves faster through the soil profile. Both can be hung up in thatch layers, so watch out for thick thatch layers!

When using liquid sprays for grub rescues, irrigate immediately after the application so that the sprays don’t dry on the turf foliage. When using granules, the normal dictate is to irrigate within 12 hours after the application.

Frankly, this is a poor statement as this often doesn’t tell the home owner how much water to apply! Again, if the thatch and soil is moist, another 3/8 to 1/2-inch of irrigation will be needed!

Finally, if there are animals digging, I often recommend using my colleague’s (Dr. Harry Niemczyk) technique! Spread some Milorganite fertilizer over the area where animals are digging. This fertilizer is made from human sewage sludge and it has a powerful odor that repels most skunks and raccoons for one to two weeks!


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