The opponent: Tree pests (emerald ash borer, Japanese beetle, scale, et al)
The coach: Dr. Jason Fausey, weed scientist for Nufarm
The game plan: Lawn care operators (LCOs) have a number of options when it comes to insecticide application methods for tree pests, but selecting the right one for you isn’t as simple as going with your favorite color or the coolest mascot.
When deciding which of the several insecticide application methods available to lawn care operators is best for you, the first thing to consider is the target pest and the proper chemistry to manage that pest. Does the product you desire to use only work when applied as a foliar spray or when soil applied? Or is it a versatile material that can be applied effectively in a number of different ways?
Once you’ve determined that, you’re ready to start thinking about the application method you will use on the site. That’s when factors such as the size of the job, the setting and the type of equipment you have available for use will help determine the right method for you.
1) Soil application – Whether you’re considering a soil drench or injection, applying an insecticide directly into the soil beneath a tree can make great sense. Perhaps the main benefit of a soil application is the avoidance of drift. But there are some factors to consider before going this route. The efficacy of a soil application can be adversely affected by soil conditions that will be nearly impossible to predict before arriving at the job site: Is it too wet or too dry? Is it sandy or clay? Is it compacted? Is there mulch or not? Is there turf around it? These variables can make results less reliable, and can therefore make a soil application less attractive.
On the other hand, soil applications are ideal for pests with multiple generations per year. Unlike a foliar treatment, where most insecticides break down after about a month, the residual of a soil application can provide months of control as the insecticide works its way up through the roots of the plant to where pests feed. Depending on which chemistry you’re using, soil applications can be just as fast as other application methods. It all depends on the active ingredient you’re working with.
2) Basal trunk or bark spray – This is my preferred method in most cases. Basal trunk sprays are fast, easy to apply, require minimal equipment and, when using a product such as Safari Insecticide, provide outstanding efficacy. They can be more consistent than soil applications or foliar sprays. If the pest you’re targeting is located inside the tree, like the emerald ash borer larvae, a basal trunk spray is an ideal choice. Basal trunk sprays can be applied quickly to a large number of trees. You don’t need special equipment to reach high up into the foliage. Unlike injections, basal trunk/bark sprays are non-invasive and don’t require drilling a hole into a tree. If you have a large number of trees to treat or are in a residential area, basal trunk sprays are ideal because there is minimal off target deposition when compared to a foliar spray.
3) Trunk injection – As with the basal trunk spray, a trunk injection may be the right choice for you when targeting a pest that feeds inside the tree. Trunk injections have the advantage of placing the product right where pests feed. However, injections can be time-consuming. You can treat several trees via basal trunk spray in the time it takes to inject a tree and wait for the insecticide to fully enter the tree. And as LCOs know, time is money. Injections are also invasive: Does your customer mind if you drill holes in his trees? If you’re treating a small number of trees and time is not a factor, a trunk injection may well be the right choice for you.
4) Foliar sprays – Despite concerns over drift and the need for both perfect coverage and special equipment to reach the foliage, there are times when a foliar spray may be the right option for you. If you’re treating for a pest such as an adult Japanese beetle, which is a foliage feeder, you’ll want to use a foliar spray. And, again, remember your setting. If the tree is located right next to or above a house, foliar may not be the right choice for you. But if you’re treating a large tree in a wide open space, and targeting a particular kind of foliage-feeding pest, a foliar spray may well be appropriate.