Organic lawn control for grubs

Culling information from:

* http://www.richsoil.com/lawn-care.jsp
* http://voices.yahoo.com/how-control-lawn-grubs-organically-6815688.html
* http://www.ehow.com/facts_7520696_organic-lawn-grub-control.html
* Amazon.com - $28.99 - "St. Gabriel Organics 8001096 Milky Spore Powder, 10-Ounce":http://www.amazon.com/exec/obidos/ASIN/B001D10EWO/lc12-20


Summary:

* Unlikely to have a white grub problem in a flower or vegetable garden.
* Uncommon problem for lawns too.
* Cornell U study conducted in a bad grub year:
** only 18% of lawns had a grub problem bad enough to warrant treatment.
* But grass is more vulnerable to white grubs than flowers and garden plants because grass roots grow close together. 
* Grubs kill grass from the bottom up.
* Check for a lawn grub problem:
** Look for irregular patches of dead or dying yellow or brown grass in your lawn. 
** Due to root damage, the grass will lift out of the ground easily if you pull on it. 
** The ground may feel soft or spongy.
** Peel back one square foot of lawn and check for the little white wormlike grubs. Rule of thumb:
***  8 or more grubs present =  infestation, so treat. 
*** 0 to four grubs, no need to treat.
***  5 to 7 grubs = ok to treat, but not imperative.
* If treating for grubs, do not use chemicals, since beneficial species, including birds can be harmed.
* Treat organically.
* Best organic method for dealing with white grubs is natural predators.
** parasitic wasps, ants, and ground beetles kill grubs and/or the eggs they hatch from (reason never to use pesticides).
** Encourage birds to visit the yard.
** Milky Spore":
*** naturally occuring bacteria that makes the grubs puke their guts out, but it doesn't seem to bother anything else. Birds are safe eating the dead grubs.
**  Predatory nematodes (also called "beneficial nematodes") 
***  micro worms that crawl through the soil and eat a variety of different organisms, including grubs.
*** Some are good for plants, and some are harmful. 
** Spray neem oil, taken from neem trees, on your lawn to suffocate and starve hiding grubs.


Details:

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Grubs are the larvae of certain species of beetles. Grubs think grass roots are yummy. If you dig up dead patches of grass you just might see a bunch of grubs munching away.

This is where birds are your friends. Birds think grubs are yummy.

I have never had to personally deal with grubs. And I have yet to encounter an organic grower that has had to deal with them. But I have had many people write to me and ask how to deal with grubs organically. Nearly all of them have mentioned "Last year I sprayed toxic goo to get rid of the grubs and now they're back". While I did not see what happened, my guess is that birds and other natural grub control ate the dead grubs and died. No more natural grub control.

So the trick is to kill the grubs, but don't harm anything that eats grubs. The answer is to bring in more grub predators.

Having done a little reading on this topic, "Milky Spore" (Bacillus popilliae) and/or predatory nematodes appear to be the organic control. "Milky Spore" is a naturally occuring bacteria that makes the grubs puke their guts out, but it doesn't seem to bother anything else. So if a bird eats a dead grub, the bird will be fat and happy. Predatory nematodes (also called "beneficial nematodes") are like micro worms that crawl through the soil and eat a variety of different organisms, including grubs.
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Birds enjoy a fat grub as a meal, and you should try luring birds into your yard. If you plant large shrubs and trees on your property, birds are more likely to build nests. Any bird you can get to live on your property will eat grubs and other pest insects nearby. While moles, skunks and raccoons devour grubs as well, they will cause their own damage to your lawn.

Several compounds made from plants and bacteria quickly kill off common lawn grubs. Spray neem oil, taken from neem trees, on your lawn to suffocate and starve hiding grubs. Use the bacteria-based "Milky Spore" to kill an entire yard's grub population in as little as two weeks.
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Grubs usually are not too much of an issue for flowers and vegetables, due to the fact that their roots are far apart and flower beds are dug up often. Grass, on the other hand, is much more vulnerable to white grubs because grass roots are so close together. Grubs kill grass from the bottom up.

Conventional lawn pesticides tend not to have much effect on grubs, though they can help by killing the adults of the species before they lay eggs. 

But it's very possible to avoid using such chemicals at all for the control of lawn grubs. For one thing, there's a good chance no treatment is really necessary. As mentioned, there's unlikely to be a white grub problem in a flower or vegetable garden. But it's really not that common a problem even for grass lawns, though people trying to sell you pesticides might attempt to persuade you otherwise. A Cornell University study conducted in an unusually bad year for grub infestations found that even then only 18% of lawns had a grub problem bad enough to warrant treatment.

So the first thing you need to do is make sure there even is a grub issue worth treating. For signs of lawn grub infestation, look for irregular patches of dead or dying yellow or brown grass in your lawn. Due to root damage, the grass will lift out of the ground easily if you pull on it. The ground may feel soft or spongy.

If this leads you to suspect grubs, peel back one square foot of lawn and check for the little white wormlike grubs. The rule of thumb is if you see eight or more, you have a serious enough infestation to treat. If you see zero to four, don't bother. If you see five to seven, that's in a gray area where it's not a bad idea to treat, but it's not imperative to do so. What you may want to do in that case is sample one or more additional one foot squares to see if they bring the average over seven or under five.

But even if treatment is necessary, there is an organic alternative to using chemical pesticides.

The best organic method for dealing with white grubs is by way of their natural predators. Certain parasitic wasps, ants, and ground beetles kill grubs and/or the eggs they hatch from. (Which is one reason against spraying pesticides on your lawn. You typically end up killing more beneficial than harmful insects.)

But you can also buy and apply one of the grub's natural predators-parasitic nematodes. Nematodes are very tiny worms. Some are good for plants; some are quite harmful. The kind that are parasitic on grubs are highly beneficial to plants in that they kill off the larvae eating their roots.

Follow the instructions that come with the package of nematodes carefully. For one thing, you'll need to thoroughly water the area of the lawn to be treated, as this enables the nematodes to swim along with the water as it seeps into the soil where they can find white grubs.

White grubs are smallest from about mid-July through September, and they tend to be closest to the surface during that time and then in March and April. So the best time to treat your lawn is the second half of the summer, and the second best time is March and April.
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