Helpful Hints and Tidbits You Should Know


Spotting Webbing

If growers have a lot* of two spotted mites, Tetranychus urticae, there should be a fair amount of webbing associated with them. Sometimes, though, this webbing is difficult to see if not viewed the right way or if viewing conditions are poor. Or — and this is an important one to the scout — if numbers are not yet high as some webbing should still be present as the colony of these pests develops. It is even more difficult to see when numbers are low. And this is the critical time (so as to avoid *scenario “A” — high numbers, lots of webbing).

There is a way to spot this webbing, though. I discovered it quite by accident one day while visiting a tomato grower’s greenhouse in Vermont. I was walking along their rows of plants, informally scouting with them as we walked, and I plucked a leaf from a plant. It was a random act, but the conditions made it difficult to view the part of the plant I was concerned with — about midway up, aisle-side — so I yanked it right off the plant.

I held the leaf up before my eyes. It looked clean without magnification. I then turned towards a good source of daylight and turned the leaf in such a way that I could look down the length of the leaf’s underside, right along the midrib. Imagine being really small and straddling the midrib like one would straddle a horse. That was the view I had. It was revealing.

I was surprised by what I saw: going from one leaf under-surface to its opposite, over the midrib, was webbing. Very fine webbing. It created a sort of tent, with the midrib being the “center pole,” if you will. Inside the tent of fine webbing were mites. Two-spotted mites, specifically. It was the very beginnings of an infestation. The grower, while dismayed by the discovery, was also happy to know about it before the webbing became obvious from all angles. So, in summary, be small, be real small, and straddle the midrib and have a look. You might find mites long before they want to be found.

Web Wiping

If you have spider mites, specifically two-spotted mites and others which produce webbing, you can really give them a good swift kick in the pants by simply giving them a sponge bath. Take a sponge and dip it in a bucket filled with a non-detergent soap and warm water. Clean the affected plants, notably the webbed portions, focusing mostly on leaf undersides. The mite’s eggs and young are there in numbers so this is such a worthwhile activity. Try it, you’ll see. It delivers one heck of a blow to the mites. When you’re done with the clean-up, add some predatory mites to clean-up even more.

Note: The webbing I’m talking about primarily goes from leave underside, over the midrib, to the opposite leaf underside (though in really bad cases it can cover entire plant tops). If you see webbing strung along from plant to plant across spans of several inches to a few feet, that is probably spider webbing. Spiders are really good predators so leave them alone if at all possible.

Sucking-Up Whitefly

If you ever touch your plants, or worse, simply stroll through your greenhouse only to stir up 100s or 1000s, or even tens of thousands of whiteflies, this is something you might want to try. Head back out of the greenhouse, run in fact (too depressing in there seeing all those pests). Grab your Shop Vac. If you don’t have one, buy one at your local hardware store; they’re under $20. I Think. Now, with Shop Vac in hand, head bravely back into that greenhouse and suck up all those airborne whitefly adults. Do take care not to suck up your plants so stick to the airborne pests. Someone can help by disturbing the plants as you go to encourage to whiteflies to take flight. This will put a big hurtin’ on the resident whitefly population so it is worth your effort. Go ahead, if the circumstances described are yours, this should now be on your Must-Do list.

Update: Here’s a new twist to this tip that’s worth reading.

Luring Thrips with Extracts

For a long time we’ve known that thrips are attracted by scent as well as visual stimuli such as color. But now there may be a way to utilize this scent-attraction to help thrips trap themselves, thus removing them from the crop. One new way to do this, even though this still requires some more experimentation, is to soak plain old cotton balls in vanilla or almond extract and place them in the crop. Apparently thrips are quite attracted to these scents and will actually make their way into the cotton balls looking for the source. The good part is once they burrow into the cotton balls they find it nearly impossible to extricate themselves. This is a novel, inexpensive approach that can help reduce thrips numbers simply by way of trapping them.

Trapping Gnats with Potatoes

Need to scout for or trap fungus gnat larvae? Here’s a novel method: Use ¼" slices of raw potato to catch them. Here’s how: Place a slice of raw potato on the surface of the media on at least one pot per section for monitoring purposes, or place one slice on the surface of the media per pot (or several on beds). Allow the slices to rest undisturbed for one week, then flip them over to check for signs of life. The gnat larvae are attracted to the slices and will burrow inside of them, feeding as they go. The inspecting scout will be able to see the holes if not the actual larvae within the slices. If larvae are present, simply throw the slice away, being sure to do so in such a way that the larvae will be destroyed or at least not emerge in the environment from which they’re being removed. In any case, due to spoilage, be sure to change the slices weekly. Easy, inexpensive, yet effective.

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