Helpful Tips and Hints

Fall Biocontrol Releases

Many growers adopt and cling to a misunderstanding that can cost them money: “Spring is the time for bugs, and that’s the time for fighting them.” Having these thoughts can be downright dangerous. Spring is a time for bugs and a good time to do battle. But it’s not the only time of year for pest control — and in some cases not even the best.

Summer is another period of activity. If you have a greenhouse, you can include mid-winter. And there’s one more very important season: autumn.

The Autumn Scenario

Fall is a great time to level the playing field — or flatten the competition. As we come indoors for winter, so do many pests, or at least they try. Picture this cycle:

• Mid-winter: you fire up your greenhouse, bring temperatures up — almost immediately you find pests. You fight them back and win a reprieve.
• Mid-summer: stock plants are outside basking in the sun. Greenhouse is buttoned up to bake out the pests, diseases and weeds.
• Now (fall): you’re moving stock plants back inside to keep them alive and retain summer flush. Pests are coming inside too — warmth, sunshine, regular watering. In the eyes of the pests it’s like spring all over again.

This is when biocontrols pay off. Introduce them in fall — they’ll feed through autumn, awaken early in mid-winter alongside the pests, and give you a presence and small population of good guys when and where none previously existed. This even works in some field crops like strawberries: putting out a hardy mite like Neoseiulus fallacis in fall helps disable two-spotted mite populations come spring.

Testing Methodology — One at a Time

In biocontrol and IPM, as in other sciences, testing is an on-going endeavor. Producers test. Distributors test. End-users test — rarely officially, often without a structured way to gauge the results. We hear things like “I’m going to test these guys out and see what happens.”

While we encourage experimentation, going about it haphazardly can produce misleading results and obscure the facts. Improper testing can confuse the tester to the point of being damaging.

The Five-Control Trap

One big problem: people try to over-test. They test too many things at once, which all but obliterates any useful data. Case in point: a grower has a certain pest — let’s call it Weirdicus buggii. Fearful of this pest, with little knowledge of how it behaves, the grower wants to try four or five different approaches at once. This stacks the odds in their favor, hoping at least one works.

The problem: if they do get control of W. buggii, they won’t know which one did the trick. Next year, they’ll have to employ all five controls again to get the same results.

It’s chancier trying one control at a time, especially biocontrols since they tend to work more slowly than chemical controls — but the results will be more clear. There will be no confusion as to what did what.

Know the pest, know what’s normal and what’s not, try one control at a time until you know what works, and go about the whole thing in a structured, logical way. Document the progress and variables. The useful information obtained by doing so is far better than shooting from the hip.

Pinch Power — Just Squish Them

The scenario, heard countless times: the phone rings. A grower has located a small grouping of aphids and wants to obtain some biocontrols to fix the problem. He’s acting swiftly — good. Then I casually ask: did you squish the little group of aphids after you noticed them?

The answer is almost always no. Why not?! If you see the pests, deal with them. Don’t rely on the bugs or the sprays when a quick pinch is such an obvious answer. Populations are generally easier to control — whether you’re spraying, using bugs, or taking matters into your own hands — when pest numbers are low.

Act when and where you have the chance. I know of no grower who’s “too big” to do this. It works. The scale is irrelevant; it’s all proportionate. Just do it.

Spotting Spider Mite Webbing Early

If growers have a lot of two-spotted mites (Tetranychus urticae), there should be a fair amount of webbing associated with them. Sometimes the webbing is difficult to see if not viewed the right way — or if numbers are not yet high.

There’s a way to spot the webbing early. I discovered it quite by accident in a Vermont tomato grower’s greenhouse. Informally scouting the rows, I plucked a leaf about midway up, aisle-side. I held it up. It looked clean without magnification.

Straddle the Midrib

Then I turned toward daylight and turned the leaf so 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 — and it was revealing.

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.” Inside the tent — mites. Two-spotted mites, specifically.

The grower was dismayed, but happy to know about the infestation before the webbing became obvious from all angles. Be small, real small, and straddle the midrib. You might find mites long before they want to be found.

Web-Wiping for Two-Spotted Mites

If you have spider mites — specifically two-spotted mites and others which produce webbing — you can deliver one heck of a blow by giving them a sponge bath.

Dip a sponge in a bucket of warm water and non-detergent soap. Clean the affected plants, notably the webbed portions, focusing on leaf undersides where the mite’s eggs and young are in numbers. When you’re done, add some predatory mites to clean up even more.

Note: Distinguishing Mite Webbing from Spider Webbing

The webbing here goes from leaf underside, over the midrib, to the opposite leaf underside (in really bad cases it can cover entire plant tops). If you see webbing strung from plant to plant across several inches to a few feet, that is probably spider webbing. Spiders are really good predators — leave them alone if at all possible.

Shop-Vacuuming Whitefly Clouds

If you ever touch your plants — or just stroll through your greenhouse — only to stir up hundreds, thousands, or tens of thousands of whiteflies, here’s the move.

Head back out of the greenhouse (run, even — too depressing in there). Grab your Shop-Vac. If you don’t have one, buy one at your local hardware store. Now, with Shop-Vac in hand, head bravely back in and suck up all those airborne whitefly adults. Take care not to suck up your plants — stick to the airborne pests.

It helps to have someone disturb the plants as you go to encourage the whiteflies to take flight. This puts a big hurtin’ on the resident whitefly population. Worth your effort. If this scenario is yours, it should now be on your Must-Do list.

Luring Thrips with Cotton-Ball Extracts

Thrips are attracted by scent as well as visual stimuli such as color. There may be a way to use this scent attraction to help thrips trap themselves — removing them from the crop.

This still wants more experimentation, but the technique: soak plain old cotton balls in vanilla or almond extract and place them in the crop. Thrips are quite attracted to these scents and will make their way into the cotton balls looking for the source. Once they burrow in, they find it nearly impossible to extricate themselves.

A novel, inexpensive approach that can help reduce thrips numbers simply by trapping them.

Trapping Fungus Gnats with Potato Slices

Need to scout for — or trap — fungus gnat larvae? Here’s the method: ¼″ slices of raw potato.

Place a slice of raw potato on the surface of the media — one per pot per section for monitoring, or one slice per pot (several on beds) for trapping. Let the slices rest undisturbed for one week, then flip them to check for signs of life.

The gnat larvae are attracted to the slices and will burrow inside, feeding as they go. The scout will see the holes if not the actual larvae within the slices. If larvae are present, throw the slice away — in a way that the larvae are destroyed or at least don’t emerge back into the environment.

Due to spoilage, change the slices weekly. Easy, inexpensive, effective.