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Lewis mite is a kind of pests that appears to go in cycles – some years we don’t see it in any respect, and a few years I get stories as early as August.
This yr there appears to be scattered stories. On condition that Lewis mite populations can ramp up in a heat fall and rear their ugly heads in October, it appeared like an excellent time for an replace on what’s working, and what’s not.
Lewis Mite Signs and Scouting:
Lewis mite is carefully associated to spider mites (Tetranychus urticae) however are a completely completely different species (Eotetranychus lewisi). For aspect to aspect comparisons of the 2 species, see this text by UCANR.
Lewis mites are solely a pest of poinsettia crops within the greenhouse (until you’re additionally rising strawberries.) Early detection is troublesome, because the signs are somewhat delicate at first: faint speckling and chlorosis (see image under), which might resemble nitrogen deficiency. Moreover, the mite is nearly not possible to see with no microscope.
Usually, Lewis mite populations go undetected till mid-October, when populations construct up sufficient to start out inflicting noticeable harm: the higher foliage will flip brown and the mites will type ugly webbing.
If you happen to haven’t handled preventatively for Lewis mite (extra on this later), stroll your crop just a little extra typically and search for the attribute stippling signs. If you happen to discover a spot on the bench with Lewis mites, take into account throwing out infested vegetation within the “Circle of Love”; i.e. throw out the infested plant and all these instantly surrounding it. Or, do a spot spray of miticides.
Lewis Mite Therapy:
Propagation:
On condition that they’re troublesome to detect, however find yourself inflicting plenty of harm, the best answer is usually a single, preventative software of a miticide on the chopping stage. (One thing to maintain in your again pocket for subsequent yr).
Sadly, merchandise historically used for Lewis mite don’t appear to be working as properly because the final time I printed this submit,e.g. Floramite (bifenzate). So what different choices are there?
Avid (abamectin; IRAC 6), though onerous on biocontrol brokers, can be utilized successfully with out derailing your bio program in case you use it early in propagation as a preventative spray, earlier than pure enemies are launched. The residues usually dissipate earlier than parasitic wasps are placed on at potting. (This technique clearly won’t work in case you launch bios in propagation).
Manufacturing:
Alternatively, Avid can work if performed fastidiously as a spot spray. As a result of Lewis mite are a comparatively slow-moving pest, you don’t must blanket the entire bench or compartment. This retains the consequences on pure enemies to a minimal.
Though Floramite by itself not seems to be very efficient for Canadian growers, including in a product with ovicidal properties may also help enhance its efficacy. In response to technical specialists, some growers have discovered Floramite, adopted instantly by Shuttle (acequinocyl), to be efficient , whereas remaining pretty smooth on parasitoids.
Simply bear in mind that Floramite and Shuttle are in the same chemical class (IRAC 20B vs 20D), and due to this fact ought to be used within the SAME pest technology “window” (2 week interval), versus alternating sprays over the season, as this might promote resistance.
If you end up needing to do a second spray 2 weeks after the primary spray, then Vendex (fenbutatin oxide; IRAC 12) could also be an excellent possibility. It has labored up to now, though it’s unclear if resistance has been constructed as much as this product or not.
Spear T (IRAC 32) can also be a comparatively new product available on the market, derived from spider venom, and is reportedly efficient on each two-spotted spider mite and whitefly, and due to this fact could also be helpful in Poinsettia manufacturing. Nevertheless, shut statement could be wanted to find out it’s efficacy on each Lewis mite and Bemisia whitefly, in addition to it’s results on parasitic wasps.
Because the season progresses, management with contact pesticides like Floramite and Shuttle can be way more troublesome because the cover is denser. Many translaminar/systemic miticides can be efficient for Lewis mite (e.g. Avid, Kontos), however will seemingly intrude with whitefly biocontrol applications. Nevertheless, in case you’re on a chemical program for Bemisia whitefly (or want to modify to 1 if whitefly stress is excessive), late September or early October that is the right time to use Kontos, as it can additionally assist management whitefly nymphs (see diagram under).
What about Biocontrol for Lewis Mite?
In case you are a facility that’s targeted primarily getting via to sale with bicontrol solely in Poinsettia, then your greatest choices for Lewis mite are Amblyseius fallacis and Neoseiulus californicus. Each of those predators can eat different sources of meals in addition to prey mites to outlive (e.g. pollen) and are tolerant to the excessive temperatures Poinsettia are produced underneath.
If put within the crop early (e.g. in propagation or instantly after potting), they will assist preserve Lewis mite in test – however spot sprays should be wanted in a heat fall, corresponding to 2024. In response to a sizzling tip from Ecohabitat ultimately yr’s Poinsettia Open Home at Sawaya Gardens, A. fallacis additionally appear extra tolerant to Avid residues that different bios, and might be launched 3-7 days after spot sprays of Avid as further insurance coverage.
Particular due to the consultants and IPM employees that preserve me (and also you!) within the loop for the content material of this submit!
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