Ion Staunton*

Mites which specialise in eating plants have modified abrading and sucking mouthparts differing from those with chewing/mandibular mouthparts for mites that eat grain, books, straw, birds, people (as in scabies).

Like other Arachnids, such as spiders and ticks, mites have an abdomen without segments; it’s a flexible bag. 

The front half is called a cephalothorax which, from this made-up name: cepha (head) and thorax (chest) means it seamlessly blends from mouthparts, palps and eyes into the muscular region that sprouts legs.

There are no antennae (palps do that job) and no wings.

There are thousands of species; most have the ability to dine happily on more than one type of plant – meaning your crop as well as surrounding vegetation.

Most produce a webbing and, being so small, a young, 0.4mmmite, letting out a few mm of fine web and letting go of the plant can float off to wherever land.

It’s always informative to know where your pests are overwinter.

If you grow deciduous trees, mites fall off with the autumn leaves and the ones which can endure winter are the last of the fertilised females, surviving if they are deep enough beneath the surface.

Overwintering in soil is the modus operandi for most mite species.

After emerging in spring, they climb upwards and the first few new leaves are attacked, and the next generation (less than two weeks later) move onto newer leaves.

The next and subsequent generations, a week or so apart, means all the new leaves can become malformed as they open.

Yes, there are mites with a liking for tropical fruit.

And as is normal for most mites, they prefer the underside of the leaf.

The Lychee erinose mite blisters the terminal buds preventing fruit set. As mentioned, leaf deformation is normal, sometimes it is just discolouration and sometimes the plant distorts and grows unusual hairs. Webbing is often noticeable.

Spider mites, broad mites, russet mites, two-spotted mites and others are just variations on the above.

They are all very small; just 0.5mm to 2mm long.

Body shape can be ovoid to elongated, depending on the species. Unless you really need to impress someone, precisely identifying a mite is not very important.

They eat, they damage, and they die.

Just 10 or so eggs are laid daily, up to 200+ per female in her lifetime of say four weeks and those eggs produce predominantly females at a ratio of maybe 3:1. (Yes, egg production does vary between species).

The hatching larval form has only six legs but within a day or so it has moulted into a nymph with eight legs and, after another few days and a couple of moults which allow an increase in size, they become randy males and females producing more eggs. Talk about a population explosion.

Control

Spraying as soon as you see damage on the first-opening buds, means mites still emerging from the soil after the initial control spray will soon replace the original damaging population.

Using a systemic chemical gets into the sapstream and takes care of new arrivals for as long as it circulates (this detail on the label).

Some suggest mite populations often increase to become serious pests when an insecticide has been used against insect pests.

I have a couple of explanations: because mites are mostly on the underside of the leaf, they may not have been contacted. Another scenario: the insecticide not only killed the pest insect but also the predatory insects that do a great job of eating mites. There are little 2-3mm long, black ladybirds, adults and larvae that can each eat a few mites per minute if they are on a good patch.

Other ladybirds of the usual orange and black colouring and a bit bigger, 4mm and 6mm long, can eat even faster.

And, while we are talking biological control, the companies which sell beneficials, also offer mite predators. at type of civil war is very effective.

Most insecticides will kill mites.

To find out for sure if what you spray kills both your insect pests as well as mites, just apply it to a tree under attack by both mites and the pest and check within a few minutes.

If they are both dead... go ahead.

If not, you should change your droplet size, angle of nozzle or increase turbulence to get better contact onto the underside of the leaf.

This testing process only takes a few minutes but is well worth the time taken.

If your first test found out you were getting close to 100 percent kill, scale back your concentration or your application rate and you might easily and you are still getting the near100 per cent kill.

You will not only have saved on the amount of solution per/hectare that you were using, you also save worthwhile money each year from then on.

Ion Staunton, entomologist, Pestech Australia Pty Ltd, manufacturer of PyBo Natural Pyrethrum Insecticidal Concentrate. Further details from 0407 30 88 67 or 1800 123 457