BCSS - Forum

Martin wrote:Dimethoate does not work on red spider mites

M

Not yours maybe. It works for me and is widely labelled for both red spider mite and flat mite. Unfortunately resistance is widespread, and resistance to one organophosphate such as Malathion usually means resistance to all of them. Rotate between miticides in different groups, although that's hard when there are none left on the market! Don't neglect non-systemic sprays for quickly knocking down visible infestations.

No mention in the above of predatory mites!

If you have an outbreak of mites (flat or red spider) on newly acquired plants and the rest of your collection is mite free, it is worth trying to eliminate the mites entirely with one of the contact sprays based on plant oils, as resistance to the spray is not apparent, so if you repeat spraying at appropriate intervals for the life cycle of the mites, you can eradicate the population and keep your collection mite free. Spraying with anything else is pretty much useless to eradicate mites, as resistance to all acaricides (legal and illegal) is now very widespread.

If you have occasional outbreaks in your main population you'd be better off using predatory mites to keep the numbers down low enough for damage to be minimal. Preventive spraying is a very good way to encourage resistance in pest populations and encourages serious pest outbreaks at it kills off any natural predator populations. Phytoseilius works for Tetranychus (but not Brevipalpus), and Amblyseius cucumeris works for Brevipalpus. Of course you have to ditch the sprayer, but think of the money you will save not to mention the benefit to your own health!

And please stop with the idea that humidity helps reduce the population of mites! Tetranychus mites dont like being sprayed with water much, but Brevipalpus, which is the commonest mite I have seen in cactus and succulent collections, thrives in humid environments, and will happily infest orchids and bromeliads. Humidity however does help the predatory mites get a foothold.

I've read on Facebook that people are using Diatomaceous Earth to control RSM. Unfortunately I haven't been able to find an exact product and how it should be applied. It's wildly available on Ebay and elsewhere and has been used in the poultry industry and grain storage for years. Anybody using this of have more specific information?

Here is some info from Wiki:

Diatomite is of value as an insecticide, because of its abrasive and physico-sorptive properties.[11] The fine powder adsorbs lipids from the waxy outer layer of the exoskeletons of many species of insects; this layer acts as a barrier that resists the loss of water vapour from the insect's body. Damaging the layer increases the evaporation of water from their bodies, so that they dehydrate, commonly fatally.

In order to be effective as an insecticide, diatomaceous earth must be uncalcinated (i.e., it must not be heat-treated prior to application)[16] and have a mean particle size below about 12 µm (i.e., food grade).