Locating spider mite colonies early on during scouting is important, no, essential, to gaining the upper hand in your attempt to keep them off your pest list. But this can be challenging, especially since they aren’t usually detected on sticky traps and other scouting tools. In fact, even the most diligent pest scouts have difficulty locating spider mites before they reproduce into more significant — and difficult to control — numbers. To find mites more quickly, there are things you can do.
Before we begin, please note that some of this has been said before. We state it again here as it bears repeating.
- Inspecting Leaf Undersides
- We’ve mentioned this one before. It was based on a discovery we made during a scouting visit to a tomato grower in Vermont. If you get down low and look along the leaf’s midrib, instead of looking at the leaf from above as most people normally would, you can see mites and fine webbing that is otherwise invisible. Doing this we were able to find spider mites in a greenhouse that had been declared “clean” by the grower. While certainly disappointed by our find, he was grateful to know.
- Sticky Strings
- This applies to greenhouse tomato growers but maybe others as well. If you use strings to support your indeterminate tomato plants, you can coat these strings with Tanglefoot or other similar product. Doing so traps any mites that attempt to use the strings to move from plant to plant. If you apply a very light coating regularly (so it doesn’t dry out), you can inspect the strings much the way we described leaf inspections, above. Doing so will allow you to see them stuck in the substance. Moreover, you can glean additional information. For example, if the mites are stuck near the top of the string you know they must have been going to that plant from elsewhere. If they are closer to the bottom part of the coated part of the string, then the mites were probably coming from that plant.
- Trap Crops for Mites
- Have you ever heard of using trap crops for spider mite detection? No? Neither have we. But why not? If it’s effective for other pests, why not mites, too? We suggest trying it, using some mite prone plant. A dry, somewhat unhealthy common or English ivy (Hedera helix) comes to mind as pretty good mite fodder, but pick whatever you know. Try to make sure it’s more appealing to mites than your crop is, but it’s not critical. Proximity counts so place your trap crop away from your cash crop but between it and the probable source of mites (i.e., the outdoors, the woods, a field, etc.). You don’t need a lot, just something attractive to mites and poorly tended to. Check it out regularly, focusing a portion of your regular scouting regimen on the trap crop. Just two notes of caution: If you do find mites, clean yourself up before heading into your cash crop and; create a good physical or spatial barrier between your cash crop and the trap crop to help prevent crossover.
These tips could keep you out of trouble by letting you know at the earliest possible moment that mites are in your space. Once you know that then you can add controls capable of offering prevention and low infestation management like Neoseiulus fallacis and N. californicus. Going this route seems to be best for the plants and the easiest on your wallet.
If you have some mite scouting tricks up your sleeve that we didn’t mention, please take a moment to share them below (while comments remain open), or contact us.
