The Preventative Tetrahedron of Bio-Control: A simple “how to”

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The most difficult hurdle for many, in their jump to bio-control from chemical reliance, is the need to switch the habit of reacting to pest pressure, with the habit of preventing pests in the first place.

Prevention is essential in three ways: One, it works. Two, it is least expensive. Three, it gives you more options.

It works so well, in fact, that twice when asking growers at the end of the season how the preventative approach worked, they responded “I can’t tell, I didn’t have the pest this year.”

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Even when the results aren’t that spectacular, growers find they had less pest pressure the whole season. But note the need to change your thinking: “less pest pressure” did not mean no pests (except in those extreme examples). What it means is the pests are always there, but never at a level that hurts production.

The matter of expense varies. In some extreme cases the first year switching to bios is the same price as chemical programs or even more expensive. This is for two reasons: One, chemical residues or a chemical “clean-up” to “start fresh” inhibits the effectiveness of the beneficial insects. Two, chemical reliance has interfered with the immediate surrounding areas, preventing natural beneficial insects from reducing the natural pressure of pests coming in from neighbouring areas. In those extreme cases, the second year is dramatically less expensive.

For most, however, the savings are immediate. Re-entry times are non-existent, saving labour costs; The sprays, spray equipment, and licensing are replaced by cost of beneficial insects at sometimes a fraction of the cost. Longevity and employee satisfaction is also increased by not needing to suit-up and spray after hours. Lastly, being able to sell to an “organic market”, or even just public opinion of your reduction of chemical usage could increase sales. Not to mention chemicals (and their spreader/stickers) inhibit plant growth. So bio programs often increase yield.

Lastly, the preventative approach gives your more options. I have some excellent growers who, for the above reasons, switched to bio-control, and yet their buyers still except plants to be “clean.” The term “clean” is frustrating, as it means wiped of anything – good or bad. But, that is the market for these growers. So they maintain the use of chemicals, but only as needed. So starting with bios gives you the ability to put the chemicals in your shed and only bring them out when totally necessary. What this ensures is that the pests in your house do not build up a resistance to that chemical throughout the season, and in those final weeks before you sell everything to those big box stores, you employ the chemistry. Sure, I’d rather buyers be comfortable with a couple aphids – especially if they see predator insects on the same plant – but we’re not there yet.

So, here’s the goods:

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A tetrahedron has a base upon which the rest of it sits. The fundamental base in this preventative program is absolutely essential:

Apply a soil-based predatory mite as soon as possible.

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You can add it to the soil mixing machine, sprinkle it atop plug trays, spoon a little in each pot as they arrive or broad cast it on a floor or field. 25 mites per square meter of Stratiolaelaps scimitus will protect against the establishment of root aphids, root weevils, pupating thrips, overwintering spider mites, psyllids, springtails…etc. The list goes on. If applying outdoors, increase the rate based on any problems you have had in the past (usually up to 4x). This is because these mites prevent the big guys by eating their eggs or first stage larva. Something like a click beetle is too big, but it’s tiny wire-worms are good food. So outdoors, this may take a couple seasons to get the full effect. Indoor, or in pots, this will simply prevent establishment of any pest at damaging levels.

For application avoid extreme heat or cold (freezing). Otherwise, these will avoid those conditions by seeking shelter and return the next year. One application for the life of the plant or up to 5 years outdoors is sufficient.

Reapplication is recommended if natural pests arrive in droves, like an inundation of thrips, adult root weevil (leaf notching) appears suddenly and in large amounts, or spider mite pressure was high the year before.

The tetrahedrons other three sides are connected to the base. However, tip it on it’s side and it doesn’t really matter which is which. This is a reason I picked the tetrahedron: while the in soil predatory mite is essential, you may have a crop that is hydroponic and has no soil media. Or, you may have a crop that is ridiculously susceptible to spider mites or aphids, so your program “base” may be control of that particular pest. So let’s look at the other sides of this tetrahedron:

Spider Mite control:

This one is easy. The stratiolaelaps in your soil is the first step. At “clean-out” you should also put stratiolaelaps on the floor near pillars, plumbing or electrical outlets as these often run into the subfloor where spider mite will overwinter.

The next step is to apply neoseiulus fallacis (also known as amblyseius fallacis) at a substantially tiny rate of 2 mites per square foot (even lower at 2 per square meter has been found to work on some crops). This is a foliar predatory mite, so sprinkle it and it’s carrying media on or near the plants as soon as the first leaves appear.

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Fallacis can survive on pollen, and a whole host of other small pests. It is fast, aggressive, but tiny (don’t expect to see it). Typically, an early establishment of fallacis will result in no noticeable spider mite throughout the year.

Furthermore, if applied outdoor, fallacis also has a multi-year establishment. We don’t know how often you need to apply it, but in some outdoor crops one application has not needed to be followed up, and we’re going on 10 years!

Aphid Control:

Another easy one: Most aphids are host specific (meaning they can only survive on a particular plant or family of plants). Some aphid parasites, like aphidius (colemani, matricariae, ervi) are aphid specific, meaning they will only control a particular kind of aphid. Furthermore, they leave the parasitized aphid carcasses (mummies) and honeydew on the plants. So the best option:

Aphidoletes aphidimyza is a predatory midge. It’s larva eat all types of aphids, the adults eat the honeydew so your plants look clean and aphids are controlled.

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Orange aphidoletes larva

These come in a package of pupa that is opened up in your greenhouse or crop/garden when the adults emerge. That’s it. 250 per acre, every two weeks in aphid prone crops. Outdoors, one or two of these applications early in the spring is enough as they will eat, cycle, grow in number and give you multi-year coverage. (Although to keep their density up we recommend repeating releases every year).

Tips:

In a cold, dark house, provide some light to help aphidoletes cycle. If light affects your plants, use green Christmas lights, as plants reflect (and therefore don’t “see”) green light.

Turn your fans off for several hours straddling dusk. Adult aphidoletes mate at this time and search for aphids by smell. They need low-velocity air for both.

Generalist:

There are many generalists, all of which tend to focus on different types of pests. But one is cheapest and is needed as a preventative to control thrips, broad mites, cyclamen mites and russet mites, all of which, once established, are incredibly damaging. Neoseiulus Cucumeris is a foliar predatory mite. Like fallacis, it is tiny, which allows it to feed on tiny pests. It is applied in large numbers regularly to prevent pest establishment.

Apply Cucumeris to plants when first leaves appear, every 2-3 weeks at a rate of 50/square foot.

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If you are worried about thrips, trap for them and when they appear in large numbers immediately apply Cucumeris again, even if out of your 2-3 week rotation.

You can also use slow-release sachets which can release Cucumeris over 5 to 6 weeks, which reduces your labour.

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That sums up the tetrahedron. If you’re new to bio-control you can follow that exactly and tweak it as necessary. If you are becoming experienced with bio-controls you’ll know that some predators don’t like some plants and you may need to adjust release rates or even find another predator. Or, for example, if your crop is spider mite prone, you may apply fallacis at an increased rate, and reduce Cucumeris applications. Some non-growing media operations use the rove beetle Dalotia coriaria instead of soil-predatory mites, as it helps control flies, and aphids without the need of soil. Truly a bio-control program needs to be specific to your growing conditions, style and crop.

Contact us at www.appliedbio-nomics.com (ask the doctor) or contract a local IPM specialist for more information.

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