As warming temperatures arrive, most readers are spending more time outdoors and in their gardens. I’m sure of this because of the number of inquiries we are getting about wildlife-friendly ways to protect vegetables and other plants.

So the time seems right to cover the basics and give some recommendations on what you should and shouldn’t do to keep your yards wildlife friendly for the upcoming growing season.

An important concept to start with is acknowledging a problem with most pest control methods: Your goal is to kill something, and it is hard to only affect the targeted pest or species. Many of the insecticides I’ll mention here are effective at killing a pest, but they do not discriminate and will often kill other insects that are actually beneficial to have around. 

I’ve written here a few times about the insecticide Bacillus thuringiensis, more commonly known as (and easier to say) “Bt,” which is organic, being naturally found in soils. Bt is typically sprayed on leaves of oak and apple trees to be consumed by emerging caterpillars, and is often used in controlling browntail moth. Browntails are an invasive species that can damage trees through repeated defoliation and cause human health problems, typically a rash and sometimes respiratory issues.

Bt works, after being ingested, by causing a caterpillar’s stomach lining to rupture, killing them from the inside out. The problem is that any caterpillar that consumes the treated leaves is going to suffer the same fate. And to perhaps state the obvious: we need caterpillars. And we need them in abundance, as an important food source for many animals, especially baby birds. 

It is worth noting that there are different subspecies of Bt, with varying degrees of toxicity to different insects. The more common kurstaki, while mainly used for lepidoptera larva (caterpillars), has little toxicity to bees, while aizawai was found to be highly toxic to those important pollinators. Remember that just because a pesticide is labeled “organic,” it doesn’t mean it is safer to use on plants. These are definitely better than synthetic insecticides, but making sure you are using the correct ones and as sparingly as possible is still important.

One of the inquiries that prompted this article was from Barbara Grimes of Shapleigh, asking specifically about the use of neem oil. Neem oil is organic, coming from the pressed fruit and seeds of a neem tree, an Old World species primarily cultivated in India and now across the tropics. More specifically, you’ll see Azadirachtin listed on neem oil products, as it is a compound processed from the oil that can have specific effects on pests.

Like Bt, Azadirachtin needs to be consumed, then inhibits growth and can cause sterilization. When Azadirachtin is removed from neem oil, you get a product called “clarified hydrophobic extract of neem oil,” which, instead of needing to be consumed, is a contact insecticide. So soft-bodied pests like aphids need to come in contact with it for it to be effective. The Xerces Society reports neem oil products in any form as being moderately toxic to bees and other pollinators. 

The point of all of this is not to say that you shouldn’t use any of the products, but rather to make sure you are aware that many of the “friendly” sounding products are still insecticides and will have secondary harms. Make sure you use them as directed and in moderation. With all the declines we are seeing across most bird populations, we need to be helping from the bottom up. Start by planting native plants in your yard (mainenativeplants.org). These will host native insects, which feed the next generation of birds. That’s the best thing you can do to help! 

Have you got a nature or wildlife question of your own? It doesn’t have to be about birds! Email questions to [email protected] and visit www.maineaudubon.org to learn more about birding, native plants, and programs and events focusing on Maine wildlife and habitat. Maine Audubon Staff Naturalist Doug Hitchcox and other naturalists lead free bird walks on Thursday mornings starting at 7 a.m., at Maine Audubon’s Gilsland Farm Audubon Sanctuary in Falmouth.