Q: What is the best way to handle insect pests organically on the garden scale?

A: The short and often unsatisfying answer to this questions is to focus on soil health, which in turn will give stronger healthier plants, which are in turn less attractive to pests and less susceptible to their damage.

While this is generally the truth, it does turn out that this is rarely achieved purely and there are a few simple practices that will augment the healthy soil, healthy plants approach, especially where we’re trying to push the limits of what can be grown in our particular micro climates.

I don’t think a lot about pests in the relative sense of worries on the farm or especially in my garden, but if I’m honest with myself there are a few pests that I deal with consistently and I’ll talk about those here, with more general approaches below.

Short List of Pests

Flea Beetle

There are two types of these, crucifer and solanaceous. The crucifer are the bigger problem for me and they eat little pin holes in leaves of crops like arugula and mizuna. I deal with them by covering the plantings with floating row cover (5 or 5.5oz). I lay it directly over the plantings and don’t worry about using hoops to keep it off the crop, which makes it less prone to blowing away. I weigh down the edges with old boards, but sand bags, or just clumps of soil work as well.

The photo above shows my farm with row cover both directly on the ground (mostly covering carrots) and held up with quickhoops (mostly covering chicories). This photo was taken late in the fall so it's mostly protecting plants from cold at this point, but I don't take chances with rust fly, and even late in the year they'll fly on warm days.

Carrot Rust Fly

Rust Fly lays its eggs at the base of the carrot plant, or parsnips, and then the larvae burrow into the root, making rusty tracks. These tend to build up over time and that’s a problem when I’m growing many successions of carrots, especially when I leave them in the ground for a long time before harvesting them. I deal with them by covering the plantings with floating row cover. This can make the tops a little wimpy and makes it harder to see when the plants need to be weeded, but it actually helps with germination unless it’s really hot (not often a problem here in the NW). There’s also insect mesh that’s available which is see through, and can be used with hoops. It’s much more expensive but the advantage, besides being able to see the carrots, is that it doesn’t make the tops spindly, which is only really a problem for bunching.

Cabbage Maggot

These are similar to the carrot rust fly, only they affect roots like turnips and they can also affect broccoli and cabbage. For me they’re really only a problem in turnips and rutabagas. Again, I just cover the plants, for their entire life, except weeding and harvest, with floating row cover.

Slugs

This is one situation where row cover is not helpful, and actually the increased humidity can be problematic. Where slugs are a problem I try to limit habitat. Basically they don’t like dry, bare soil, which is difficult for them to crawl across. This means I don’t mulch (although dry grass clippings are supposedly also a barrier), and I eliminate grass pathways, trying to keep the surface of the soil as loose and dry as possible.

Plant Health

Other than those, there are none that are consistently a problem for me. Going back to my first statement the soil health and general plant health are huge here. I definitely see problems as soon as plants get to be stressed. Also, some varieties are more susceptible, and varieties that are not adapted to my location, and therefore easily stressed are more susceptible. Cucumber beetles will attack young melons or squash and they can generally be kept off of the young plants with row cover until they get established. Aphids will attack stressed brassicas almost every time. My kale plants get stressed from summer heat and are attacked by aphids every summer. When the temperatures moderate in the fall the aphids disappear and the kale is beautiful all through the winter.

Anything you can do to provide good growing conditions will help plant either outgrow or avoid pests. Floating row cover not only provides a physical barrier, but it also moderates the environment around the plants, allowing them to establish and grow more quickly. Regular, appropriate watering keeps plant growing evenly. If plants are too wet, or too dry growth is slowed and insects are attracted, or can get the upper hand.

Predators

Part of good soil health is also creating a broad base of biological activity, and this includes lots of predators. Masanobu Fukuoka points out in his book “The One Straw Revolution” that there are many predators and in some years one is more prominent than in others.

“This year spiders appeared in great numbers, but last year it was toads. Before that, it was frogs that predominated. There are countless variations.”

Diversity is important, and habitat for that diversity is important.

Diversity in Plantings

Just as diversity in predators is important, diversity in your plantings is important. Even for experienced growers there are crop failures. When there is a crop failure of one variety and you’re only growing three things that’s a huge loss. If you’re growing 30, it’s not as big a deal. Some years favor one crop over another, and while we can do a lot to help crops along in a bad weather year, or a year with particular pest pressures, sometimes its best just to take the loss, concentrate on the crops that are doing well, and try again the next year thinking about what it was that caused the loss and trying to avoid the same situation.

Spraying

The honest truth is that in 15 years I’ve tried using soap once. It didn’t do much, and I’ve never sprayed anything else. It’s not that the other sprays don’t potentially work, it just that it’s an added expense, not just the product, but the sprayer, and the protective gear to spray it, and I just don’t want to deal with that, and I haven’t really needed to. In addition, one other time when someone I was working with went to spray soap on some pepper plants in a greenhouse that had been infested with aphids she found that the aphids were practically gone and they were covered in ladybug larva. Sometimes waiting for the predators to do their job isn’t a bad idea, you wouldn’t want to put them out of work and have them move away, or worse, kill them with your spray.

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