Here in Massachusetts, fall is one fine sight to see. The leaves fade into beautiful shades of goldenrod yellow, crimson red and burnt orange. The birds are chirping. The autumn breeze a’blowing. Your favorite fall decor surrounds your front door.

But unbeknownst to you… there are menaces taking shelter on your landscape! 

Now is the time our region’s gypsy moth and winter moth population lays their eggs. Their spawn cocoon snuggly in or against your trees until ready to hatch in the spring, when thousands of caterpillars hatch and eat your freshly sprouted leaves.

Luckily, there is something you can do this fall to prevent overwintering insects from devouring your trees and vegetation next year: spray horticultural oil. Let’s explore how this pesticide works:

What is a Horticultural Oil Spray?

A horticultural spray is a light-weight, oil-based pesticide that can be safely applied to your plants to kill leaf-eating insects. 

While the spray causes no harm to your trees or shrubs, the oil is heavy enough to block the spiracles these bugs have to breathe and smothers them to death. Horticultural oils also disrupt the insects’ metabolism while they’re still eggs, affecting the growing larves’ ability to feed— starving them.

How Does this Bug Spray Work?

We spray our Lesco horticultural spray directly onto leaf-eating bugs’ eggs* throughout the summertime until late fall, depending on which moth is your problem. This proactive step reduces the number of cocoons that’ll survive through pupation in their egg sacs, and as a result, reduces the number of hungry caterpillars on your landscape come hatching time.

*It’s important to note that this spray will not kill adult moths! Around Thanksgiving we have clients calling in a panic like clockwork, saying it’s like it’s snowing on their lawn— that’s how many white winter months are swarming. At this point, we usually tell the homeowner they have to let the moths run their course, but that we can help to combat these pests next year by destroying the young eggs during the upcoming summer. Read more about the moths’ hatching cycles below.

Which Bugs Does the Oil Spray Kill?

Our Green Sphere team applies horticultural spray to your trees and shrubs to target Massachusetts’ biggest overwintering pests eggs: gypsy and winter moths. (The types of insects a hort spray will kill though is wide, as it’s a pesticide).

Gypsy moths usually appear as red or blue-dotted caterpillars from April to May and transform into adult moths by August. They feed on your trees and foliage before laying more eggs mid-fall, which grows over the winter and hatch as caterpillars come spring. These are the guys we want to hit with some spray from September until November!

But there’s another leaf-eating insect you have to worry about… the adult male winter moth. This moth emerges from the ground in November and goes on a similar feeding frenzy. He then mates with a female, who lays about 150 eggs under your tree bark or in tree crevices. And that’s just one female moth. Imagine dozens of mommy moths mating and laying hundreds of eggs on your property.

When Should it Be Sprayed?

We recommend only spraying as needed, as determined by a property assessment. 

If there are gypsy moth eggs incubating, we can spray the pods from early fall until roughly mid-November. Some may persist until spring, so we may recommend spraying your trees and shrubs again early spring to stop any lingering fighters before they hatch.

Winter moths are different. Their pupation occurs in late May or early June, so we spray their egg pods during the summer to kill them before they hatch around Thanksgiving. If you missed this spraying window, you’ll almost certainly have a moth problem in Nov/ Dec, and should be mindful to apply a preventative spray late spring or early summer next year.

Where Should it Be Sprayed?

Our horticultural oil spray is safe to use on shade trees, ornamental trees and shrubs like broadleaf evergreens, woody ornamentals, residential fruit trees like apples, pears, pecans, peaches, etc. as well as on flowers and foliage plants like roses and other flowering shrubs. Our hort spray is pretty much safe on most, if not all, of Massachusetts homeowners’ landscaping. 

Don’t Forget About Beetles! Pair the Spray with Tree Injections

Keeping leaf-eating pests away may require multiple tactics. We often recommend pairing horticultural oil spray with tree injections for landscapes overrun by moths or beetles.

Our Arborjet tree injections use the least amount of possible tree pesticide, with the greatest amount of control. We usually perform these non-invasive injections in September, but if you’re reading this and missed the window, we can also treat your trees come April to ward against infectious and plant-destroying insects. Learn more about our tree injections here.

Professional Pest Control with GreenSphere

There is a lot that people simply don’t know about pest control. It’s easy to mistakenly misidentify which moth is your problem. Or, to start treating your landscape for leaf-eating insects when the problem is really a disease or another pest, like lawn voles or rabbits!

Because of this, it’s always better to trust the keen eye of a landscaping expert who can accurately assess your problem and get you the quick fix you need. We always say, “Hire a professional— you’ll be glad you did!”

Let us keep all kinds of annoying bugs (like ticks and mosquitoes too) off your property. Learn more about our insect treatment programs.