Organic Pesticide Guide

What to use and when can be an overwhelming experience for gardeners looking to grow organically. Just because thing are organic doesn’t mean it is free of chemicals, or even safe for that matter.

Many organic pesticides are as toxic as inorganic ones. The biggest thing to do is use sparingly and be proactive with understanding the thorniest pests’ life cycles so you can target them with minimal impact on other insects. Also, best practices include treating in the late evening or early morning hours with light to no winds, and without rain in the forecast.

I generally only use microbial pesticides, in addition to minerals. Think Bt, Cease, and kaolin clay. Those are the three we reach for with regularity in our garden. We haven’t utilized horticultural oils or insecticidal soaps here, but I do include them in the guide, though in full disclosure I don’t have much experience with their efficacy.

We very occasionally use Neem in the garden, and don’t use Btg though I would if Japanese beetle populations increased again. Combined, these five are listed on page 1 of the 2-page guide. The second page is a list of mostly oils that we don’t use but seem to have some good applications in home gardens.

Types of Pesticides

Fungicides are effective by preventing the spores from attaching to and populating (colonizing) the leaves of plants. These must be applied proactively, early and often.

Insecticides target and kill larvae and adult insects, and sometimes eggs. They might be effective as a contact insecticide (coating the insect) or when ingested. This varies by product.

Being a Good Gardener

The first way to think about pesticides is: are you going for a preventative or reactive approach?

The second thing to think about is will you try to treat the insect or the plant? Most oils require “contact”, meaning their effectiveness lies in cutting, suffocating, and/or dehydrating the insects and this must be done by spraying them or having them crawl over the powder.

The other main way insecticides are effective is through ingestion, such as Bt. These are sprays that dry on surfaces. There are benefits and drawbacks to both approaches, and I listed the main ones in the guide.

For obvious reasons, if we are dealing with a fungal disease, we won’t be treating an insect (usually), but we will be preventatively treating the plant (eg, spraying Cease to prevent Septoria Leaf Spot from developing on my tomato plants).

Hope this helps you think through what might be best suited for your garden and pests.