Roll Your Swirskii Bottle Before You Open It

Mites arrive loose in a bottle of dry bran that looks a lot like sawdust. They sink through it on the journey, so a bottle opened straight out of the box gives your first plants mostly bran and your last plant most of the animals. It is the commonest way a release done carefully still comes out uneven, and the fix takes thirty seconds.

It is one of five steps below — none technical, none involving water or a sprayer, about ten minutes for a shelf. What is worth reading for is which of them change the outcome. The ones people agonize over mostly do not, and two that sound optional decide whether you can tell, three weeks from now, whether any of it worked.

Step 1: the box arrives

Open it the same day. This is livestock with a short shelf life, and a box left on a porch over a weekend is the most common avoidable loss in this whole business.

If you genuinely cannot use them immediately, the two formats want different things, which is worth getting right because they are usually in the same box.

You will not see anything happening in either format. That is what correct looks like.

Step 2a: if you have a bottle

The mites are loose in a carrier of bran and vermiculite — the granular stuff that looks like sawdust. It gives them something to walk on and keeps them from crushing each other.

1. Roll it first — ten slow turns on its side, as above. Everything else here depends on the bottle being mixed.
2. Open it over the plant, not over the bench. Whatever comes out first is going somewhere.
3. Tap, don't pour. Hold the bottle at an angle above the plant and tap the side so a thin scatter of carrier lands on the upper leaf surfaces. You are aiming for a dusting you can just see, not a heap.
4. Spread it around. A few taps per plant across several leaves beats one pile on one leaf. The mites will walk, but not far — see step 3.
5. Leave the carrier where it lands. Do not brush it off, do not mist it in. Mites are still in it for a day or two.

Step 2b: if you have sachets — the small paper packets

A sachet is a small paper packet with a working colony inside it — predators, their eggs, and a supply of food. It has a small opening called a vent, and the mites walk out of it over the following weeks.

Do not open it. There is no step where you open it. Opening a sachet turns a four-week nursery into a very small bottle.

1. Find the hanging hook at the top. Most sachets have one — a wire or card hook you loop over a stem. If yours is a plain flat packet, drape it over a branch so it hangs folded like a saddlebag, or hold it there with a plant clip, a clothespin or a twist tie round the stem. The only rule is that nothing pierces the body of the sachet, because a hole is a second exit and a way in for water.
2. Put it in the canopy, in shade. Among the leaves, on a stem or branch, where the foliage shades it. Not on the pot rim, not on the bench, not dangling in the open.
3. Make sure it touches foliage. This matters more than the exact height. A mite leaving the vent should be able to step straight onto a leaf rather than walk down a bare stem to find one.
4. Keep it dry. Hang it above where you water, and do not mist it directly. Water damages the rearing material inside, and a soaked sachet is a finished sachet.
5. Then leave it alone for about four weeks, and replace it rather than refilling it.

Step 3: how much to put out

Sachets are simple: one per plant for anything in a pot six inches across or bigger, or one every two to three feet where plants are touching and a mite can walk between them. Smaller pots standing together share a sachet; smaller pots standing apart each need their own, which is usually the moment a bottle makes more sense.

That "where plants are touching" clause is the whole rule, and it is worth understanding rather than memorizing. Swirskii moves roughly three feet a day across a continuous canopy, and it barely moves at all between pots that do not touch. Two plants six inches apart on a shelf are, as far as this animal is concerned, two different planets.

For bottles, the published rates are 20 to 30 mites per plant preventively, and you are not going to count them. Practically: a light, visible dusting of carrier across a few leaves of each plant. If you can see a scatter of granules on the leaf, that is the dose. Detailed rates for bigger setups are in how many swirskii per plant.

Step 4: if there are no pests yet, give them food

If you are releasing preventively — before there is a pest — the mites need a food source or they will starve, wander off, or eat each other. This is what predatory mite food is for, and ours is a blend of cattail pollen, brine shrimp eggs and brewer's yeast.

You do not weigh it. The method is a dry artist's or makeup brush: dip it in the jar, hold it over the plant, and tap the handle so a barely visible dust settles on the leaves, concentrated around new growth. Think seasoning rather than breading. Repeat every ten to fourteen days.

One exception, and it matters. If you already have an active thrips problem, skip the food. Pollen feeds thrips too, and on a collection that is already infested you can make things worse. Feed once the pest numbers are down — the reasoning is in feeding predatory mites.

Step 5: mark one leaf

Sixty seconds now, and it is the only way you will know later whether any of this worked.

Pick one leaf on the worst-affected plant and mark it — a loop of colored twist tie around the stem behind it, a small sticker on the petiole, a dot of nail polish on the stem. Write down the date and what is on that leaf right now: how many whitefly nymphs, or how much damaged new growth there is.

You are not going to be able to find the mites. A marked leaf lets you compare the same leaf to the same leaf in two weeks, instead of comparing your memory of the plant to the plant. A sticky card near the canopy does the same job for thrips.

Four things that waste a bottle of mites

• Spraying anything. Including horticultural oil, insecticidal soap and neem. There is no spray that knows the difference between a pest mite and a predatory one. If you have sprayed recently, check how long to wait before releasing.
• Opening the sachets. Covered above, and worth saying twice.
• Misting the sachets. Raising the humidity around the plants is good; water landing on the sachet is not.
• Deciding it failed at day three. Swirskii eats the youngest stages, so it works on the generation coming up rather than on the adults already flying. Counts fall over a couple of weeks, not overnight. What the first three weeks actually look like is in you won't see your predatory mites.

Tips

Common questions

Do I open the sachet?

No. The sachet has a vent the mites leave through on their own, and inside it is a breeding colony with its own food supply that keeps producing predators for about four weeks. Opening it turns that into a one-off release of whatever happened to be inside at the time.

Where exactly do I hang a sachet?

In the canopy, on a stem or branch, shaded by foliage and touching a leaf if you can manage it — and above the height you water to. Contact with leaves matters more than the exact height, because a mite leaving the vent should be able to step onto a leaf rather than walk down a bare stem to find one.

How many mites do I need per plant?

One sachet per reasonably large plant, or one every two to three feet where the foliage is touching. For bottles, the preventive rate is 20 to 30 mites per plant, which in practice is a light visible dusting of carrier across a few leaves. Dose per plant rather than per square foot unless your canopy is genuinely continuous — swirskii barely moves between pots that do not touch.

Can I put them in the fridge?

Not a normal kitchen refrigerator — the air in one is very dry and it will dehydrate the colony. If you must hold them, around 50 to 55 °F for a day or two. The real answer is to use them the day they arrive.

Do I need to feed them?

If you are releasing before there is a pest, yes, or they have nothing to eat. Use a dry brush to tap a barely visible dust of predatory mite food onto the leaves every ten to fourteen days. If you already have an active thrips problem, hold off — the same pollen feeds thrips.

How will I know it worked?

Not by finding mites, which you almost certainly will not. Mark one leaf on the worst plant and note what is on it today, or put up a sticky card for thrips. In two weeks compare the same leaf to the same leaf.