Page Intro: Stethorus punctillum, the spider mite destroyer, is used for the control and management of various spider mites. On this page you will find a description, life-cycle info, benefits, drawbacks, scouting info, advisories, usages, and other good stuff such as ordering.
Description
These tiny 1.5-2 mm. black beetles are relatively new to the commercial biocontrol industry. However, naturally speaking, they’ve been around for a very long time and are fairly well documented; since as early as 1936. Needless to say, but said anyway, I’m happy to be able to tell you about them. It is indicative of their commercial availability, and that is a good thing.
One thing which is a certainty: these beetles, as their name implies, have a pretty impressive track record for controlling various spider mites. I am not aware of alternate prey for these little guys, but, being beetles — which are fairly opportunistic by nature — they may impact other critters. There is no indication that predatory spider mites are at risk of being eaten, however. This is probably because predatory mites are very fast and tend not to hang out on one leaf for too long.
S. punctillum are very similar in appearance to Delphastus cataliniae but tend to be a little hairy like their scale eating cousins, Rhyzobius lophanthae.
These beetles have historically controlled the two-spotted mite and the carmine red mite (Tetranychus urticae and T. cinnabarinus, respectively); the European red mite (Panonychus ulmi); and another species, Metatetranychus ulmi, for which there is no common name, if it has one, is unknown to me, but may be a synonym for the European red mite mentioned above. It would not be at all surprising to discover many other pestiferous mites which could, at least, be impacted by this aggressive little beetle.
S. punctillum are provided in small lots as pre-fed, pre-mated adults which, theoretically, are supposed to track down spider mite populations, begin feeding and reproducing, without too much delay. This statement has been upgraded from “theoretically” to “realistically” since this text was originally written I’m happy to report. With these beetles you can avoid serious spider mite damage. [Intro]
Life-style
The minuscule adult female beetles lay their eggs amongst pest colonies, laying up to 8 eggs per day (in the lab, perhaps more in real life). The eggs hatch into grayish, alligator-shaped larvae similar to that of R. lophanthae, but smaller. These, too, are fierce predators, growing up to 2 mm. long and consuming a great number of pests.
The life-span of these predators is roughly 18 days in their immature stages, then 4-5 weeks as adults. The conditions for optimum performance will be between 69-90°F with a relative humidity of around 60%. But these are optimum conditions, and not necessarily a prerequisite of successful implementation. Please note, however, cooler temperatures (less than 59°F) will hamper reproduction and development a certain degree. [Intro]
Benefits
These predators should provide outstanding results in the short- and long-term. Our own trials, thus far, have yielded favorable results in outdoor orchard applications. Indoor applications, including greenhouse, have been documented previously by others. The best reports come from the hydroponic folks out there.
They can fly. With exception to Feltiella acarisuga, there are no other commercially available spider mite predators with this special ability (unless you count predatory mites on a windy day). Flight allows this beetle to enter the canopy of trees, without the aid of hand placement, much more quickly.
Another significant benefit to using these beetles is the way they’re supplied: pre-fed, pre-mated. Oviposition or egg-laying can potentially occur very soon after release. [Intro]
Drawbacks
These beetles may be a bit on the pricey side. This will probably be the case until production peaks. This hinges on steady demand. I suspect that the results may far outweigh the price issue.
Another possible drawback is the fact that they can fly (a double-edged sword) giving them the power of rapid exodus should they choose. [Intro]
Scouting
Adult beetle presence, larval presence, reduction of pest numbers and new, clean plant growth. These are all signs that spider mite destroyers are hard at work.
The white eggs of this beetle can sometimes be found scattered along the host plant’s leaves, top and bottom. Since many beetle eggs have a distinctive football shape, and are usually laid in rafts (clusters and/or rows). These eggs, found scattered, may be easier to spot.
The scout may also wish to search for the beetles’ pupae — grayish balls — in the lee of the veins on the leaf undersides. [Intro]
Advisories
Aside from misting the site with water before releasing and doing so in the evening (sometimes not necessary in interiors), there are other things you can do to ensure the maximum number of beetles perform. Flowering, pollen producing plants may a big plus, but still needs confirmation. Honeydew is another possible supplemental food source, but it is unlikely a significant one.
You may want to try releasing these beetles into trees the way we are suggesting to try for Cryptolaemus montrouzieri: Find a long bamboo or wooden pole with an approximate diameter of three-sixteenths to one-quarter-inch; insert one end of the pole through the pre-manufactured hole in the bottle’s lid and into the bottle of beetles, being careful not to injure any of them; the beetles will climb up the pole to the other end [if it’s not too hot, in which case they may fly off the pole, but should still make it to the foliage — eventually — which should be tucked into the tree’s foliage.
Yellow sticky traps used in greenhouses may present a problem with these beetles. We are unsure of this and ask that you exercise cautious observation when the traps are in use. If predator numbers on the traps get too high, remove the traps or use them for only two or three days per week. [Intro]
Usages
I’m not certain of every possible use. I suggest trying them in any environment where pest mites are present. And please let me know how they do. This especially true of tomato growers who are eager for another form of mite control. Best environment thus far: a hydroponics greenhouse. [Intro]
Rates, Instructions, and Purchase
Need more information? Check out our release rates or our short-term storage, handling, and release instructions. You may also purchase S. punctillum. [Intro]
