Insect-killing nematodes (tiny white crescent) emerging from a dead insect larva. Photo credit: Peggy Greb, USDA Agricultural Research Service, Bugwood.org
Nematodes are tiny worms. While some of them can damage plants, some prefer to eat insects, and these “good worms” (entomopathogenic nematodes is the technical term, but we can call them EPNs for short) can be helpful biocontrol agents. Teresa Rusinek (Cornell Cooperative Extension eastern NY Commercial Horticulture Program) wrote a guest blog post about her work testing EPNs for control of wireworms in sweet potatoes. Elson Shields (Cornell Entomology) has spent many years perfecting the use of persistent EPNs that are native to New York in agricultural fields where they control insect pests. Kyle Wickings is my go-to expert on using EPNs to manage white grubs in turf. A former graduate student in Kyle’s lab (Max Helmberger) made an amazing video describing the life cycle of EPNs. John Sanderson is the Cornell guru of greenhouse biocontrol (including EPNs for greenhouse insect pests).
So many people have developed so many great materials on EPNs, the purpose of this post is to point you to some of these great resources. Why re-invent the wheel? And if I’ve missed something, please let me know!
John Sanderson (Cornell University) has done some great work evaluating different EPN species for controlling insect pests in greenhouses. You can watch a webinar summarizing this work here.
Carol Glenister (IPM Laboratories) and Elson Shields (Cornell University) did a presentation on “Getting the Most Out of Beneficial Nematodes in Organic Production” for the UMass Amherst Extension Vegetable Program. You can watch the recording on YouTube, and you can read their answers to frequently asked questions online.
Proper identification is essential to good IPM, and Kyle Wickings’ Grub ID key helps you do just that.
Need help identifying your white grubs (a critical first step to using EPNs effectively in your lawn)? Kyle Wickings developed a simple key.
Are you concerned about grub damage in your home lawn? Put back that pesticide bottle, and start by scouting and identifying grubs, then apply some EPNs (only if you need them). You can find all the details here.
Count how many white grubs you actually have per square foot (and identify them) before deciding if an EPN application would help.
If you are growing alfalfa, Elson Shield’s lab has all the information you need to successfully use EPNs to control alfalfa snout beetles, starting with an overview, and including detailed resources to help you be successful.
Wondering if EPNs can help you control fruit and vegetable insect pests? In consultation with my colleagues, I developed a summary of what we know about which fruit, vegetable, and ornamental pests you are likely to be able to manage with EPNs. More research is ongoing, so this list will continue to evolve.
This work is supported by NYS Departments of Environmental Conservation and Agriculture and Markets.
This post was written by Amara Dunn, Biocontrol Specialist with the NYSIPM program, but was only possible due to the great work done by colleagues. All images are Amara’s, unless otherwise noted.
These white grubs can damage your lawn…but only if enough of them are present. Don’t waste time and money treating for them if you don’t need to!
For much of this summer, many people in NY had “water” at the top of their lawn care list. White grubs are another concern for home lawns. But finding a grub in your lawn does not automatically mean that you need to treat. Before you think about doing anything to your lawn to kill grubs, you should know how many grubs you have, and which species they are. If you do need to treat, consider using biocontrol.
Good news! It’s the perfect time of year to scout for white grubs. Starting in mid to late August, and continuing into October, grubs that hatched from eggs laid during the summer will be just beneath the surface of your lawn, feeding on the roots of your grass plants. This is the time to look for grubs. You might also notice some damage to your lawn from white grub feeding during this window.
Late August through October is the perfect time of year to look for grubs in your lawn. The grubs will be young and close to the surface.
X marks the spot (to sample for grubs)! Select parts of your lawn where you think there might be grubs, sample in these places, and take notes on what you find.
Take a look at this fact sheet for detailed instructions on sampling your lawn. All you need is a piece of paper, something to write with, and a shovel or trowel. Check 1 foot by 1 foot squares around the lawn. If you have a bulb planter with a diameter of approximately 4.25 inches, or a golf course cup cutter, this works, too. Make notes about where you’ve sampled and how many grubs you found in each spot. Save the grubs from each sampling location separately.
Cut a 1 foot by 1 foot square at each sampling location, and look for grubs in the roots of the grass. (Photo credit: NYS IPM)
If you didn’t find any grubs, please don’t treat your lawn! You are wasting money, and applying unneeded pesticides (or biocontrol nematodes) is never a good idea. If you did find grubs, it’s important that you determine which species they are. Why? Because the white grubs you are likely to find in NY are the immature (larval) stage of many different insect species. And each species causes different amounts of damage to your lawn. This means that the number of grubs your lawn can tolerate before it’s damaged – and therefore the number of grubs you should tolerate before treating for grubs – depends not only on the overall resilience of your turf, but also on the grub species you have. Check out the following table:
White grubs may look very similar, but they are not! Different species cause different amounts of damage to your lawn. If you find more than the number of grubs per square foot (or per 4.25-inch diameter soil core), you might consider treating your lawn for grubs. If not, you don’t need to do anything!
Fortunately, identifying grubs is easy, too! All you need is a penny, a hand lens with at least 15x magnification, and this online Grub ID tool. First, use the green “Learn how to identify grubs” button to find out which part of the grub to look at and how to hold it. Next, follow the instructions to compare each grub you found to the size of a penny.
The Grub ID tool explains exactly which part of the white grub to look at when you are identifying it. Just click the green button.Take a close look at the rear end of a white grub (using a 15x hand lens) to find out which species you have.
Finally, inspect its rear end with a hand lens to determine which species you have. Once you’ve identified the species, click on the species name to find specific management information. Now, look at that table again. For the species you found in your yard, do you have more than the listed number per square foot (or per 4.25-inch diameter soil core)? If not, then don’t waste time or money treating your lawn.
Most likely, only a few spots in your lawn (if any) warrant grub treatment. This is why you took careful notes about where you found grubs. Late August through September is also a good time to use a curative treatment for grubs in NY. The grubs are small and easier to kill. Some chemicals are effective when used at this time (but not the ones that are taken up by the plant!). A preventative pesticide that is taken up by the plant and kills the next generation of grubs when they start feeding in the late summer and fall should be applied in May or June. Before using any pesticide, find out if it is allowed in NY and find the product label using the New York State Pesticide Administration Database (NYSPAD). If a product isn’t listed in this database, you may not use it in NYS (even if you can buy it online). You must follow all instructions on the label.
Use the product registration section of the New York State’s Pesticide Administration Database (NYSPAD) to check if a white grub pesticide is allowed in NY. When you get to the website, follow the three simple steps shown here.Unlike the healthy white grubs you saw earlier in this post, this grub has been killed by nematodes.
But why use a chemical when you could use a biological control? Entomopathogenic nematodes are tiny beneficial worms that don’t harm plants, but kill grubs. See how they do it by watching this short video. Why wouldn’t you want these nematodes working for you? Beneficial nematodes are a curative white grub treatment, so they should be applied between mid to late August and October. But you still only need to apply them to spots where grub numbers exceeded the thresholds in this table. You can purchase nematodes from garden centers or online garden supply stores. Look for the nematode species Heterorhabditis bacteriophora and Steinernema feltiae.
Grub-killing nematodes are sold as what looks like a dry powder. Dissolve them in non-chlorinated water (if available) before applying them to your lawn. Follow all package instructions.
For both species, make sure to follow the instructions on the package for storing and applying them. Nematodes will be harmed by ultraviolet light, so apply them around dawn or dusk, and water them afterwards to wash them into the root zone of the grass (where the grubs are). Any type of sprayer (as long as it doesn’t contain a fine mesh) or even a watering can will work to apply nematodes. If you use a sprayer, keep the pressure below 30 pounds per square inch. When you’re mixing up the nematodes, if non-chlorinated water is available, use that. Chlorinated water is fine for watering them in after you apply them.
Regardless of what treatment you use, scout your lawn again next year to find out how well your IPM strategy worked, and if there are other areas you need to treat (or not).
This post was written by Amara Dunn (NYS IPM) and Kyle Wickings (Department of Entomology, Cornell University).
