How to determine what is eating your plants


I’ve been gone for a few days enjoying the backcountry of Glacier National Park, so you can imagine my horror when I came home to dying pumpkin and zucchini plants. Something is skeletonizing the leaves, and search as a might, I cannot figure out who is the culprit. Since I am in the middle of sleuthing out the particular pest that is doing this, I thought this is a good opportunity to share a few steps on how to go about it.

Some pests are easy to spot. When a big ol’ hornworm caterpillar is chomping away on your plants, you know what the problem is. But for my poor plants there is nothing crawling on them at all; at least nothing I can see with my naked eye or during the daytime. Here is what I’m doing to find what’s eating the plants:

~ Do an internet search. This is kind of the crystal ball (like Web MD!) when something isn’t right. But when I type in “skeletonized concurbits” or “what pest is skeletonizing my pumpkin plants” nothing relevant comes up in the results. I was shocked because the symptoms are pretty dramatic. Even the gardening forums failed to shed light on the subject.

~ Ask fellow gardeners. We have an excellent local Facebook page where you have a lot of veteran gardeners who are willing to offer their insight. I posted a few pictures of the problem and threw it out there. You do have to wade through some of the advice, but several of the gardeners had good ideas ranging from going out at night with a flashlight and white paper to see if I could tap some of them off of the plants, to putting the leaves under a microscope.

~ Turn to Extension. One of the gardeners who offered to put it under a microscope was a Level 3 Master Gardener. He has a camera hooked up to his microscope to be able to take photos when you find something suspicious. Plus, he’s taken phenomenal pictures of different bugs. It really opens up a brand new world. Part of the Master Gardeners’ efforts include helping other gardeners with their various issues so they’re a good place to turn to if you don’t know what’s happening in your garden. If they don’t know they answer, they usually can find someone who can figure it out since they have university resources at their disposal.

~ Send it to a diagnostics lab. If you, and everyone else, continues to be stumped, there are often labs connected to universities where you can send samples. We have one at the Montana State University, although I have a feeling the plants might be dead by the time I would receive an answer because they are being hit hard and fast. If I can’t pinpoint the problem, I still might do this simply to know in case this happens again.

So what do I do in the meantime? Diatomaceous earth seems to be my go-to answer for just about any creepy crawly, but with the torrential downpour we had last night, it didn’t last long. I’ll redust again this morning. I’m also going to pick up an organic pesticide with Bt (Bacillus thuringiensis) in it when we go into town this morning. There are some pests that are resistant to it, but it’s typically a safe bet. If all else fails, I might bring out the big guns by dosing them with Sevin. I need to figure out what is going to work.

Not knowing what you’re dealing with is extraordinarily frustrating. Typically if you follow these steps, and you might not have to go through all of them, you can determine what you’re fighting so you choose the best way to battle them.

Meet Amy Grisak

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