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 studies as early as August.
This 12 months there appears to be scattered studies. Provided that Lewis mite populations can ramp up in a heat fall and rear their ugly heads in October, it appeared like a superb 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 completely a pest of poinsettia crops within the greenhouse (until you’re additionally rising strawberries.) Early detection is tough, for the reason that signs are fairly delicate at first: faint speckling and chlorosis (see image under), which may resemble nitrogen deficiency. Moreover, the mite is nearly unimaginable to see with no microscope.
Typically, Lewis mite populations go undetected till mid-October, when populations construct up sufficient to begin inflicting noticeable injury: the higher foliage will flip brown and the mites will type ugly webbing.
In the event you haven’t handled preventatively for Lewis mite (extra on this later), stroll your crop a bit of extra typically and search for the attribute stippling signs. In the event you discover a spot on the bench with Lewis mites, contemplate throwing out infested crops 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 Remedy:
Propagation:
Provided that they’re tough to detect, however find yourself inflicting a number of injury, the best resolution is usually a single, preventative utility of a miticide on the slicing stage. (One thing to maintain in your again pocket for subsequent 12 months).
Sadly, merchandise historically used for Lewis mite don’t appear to be working as effectively for the reason that final time I printed this put up,e.g. Floramite (bifenzate). So what different choices are there?
Avid (abamectin; IRAC 6), though exhausting on biocontrol brokers, can be utilized successfully with out derailing your bio program when you use it early in propagation as a preventative spray, earlier than pure enemies are launched. The residues typically dissipate earlier than parasitic wasps are placed on at potting. (This technique clearly is not going to work when you launch bios in propagation).
Manufacturing:
Alternatively, Avid can work if carried out rigorously 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 now not seems to be very efficient for Canadian growers, including in a product with ovicidal properties will help enhance its efficacy. In line with technical specialists, some growers have discovered Floramite, adopted instantly by Shuttle (acequinocyl), to be efficient , whereas remaining pretty mushy 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 needs 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 a superb choice. 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 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. Nonetheless, shut statement can 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 will probably be far more tough for the reason that cover is denser. Many translaminar/systemic miticides will probably be efficient for Lewis mite (e.g. Avid, Kontos), however will possible intrude with whitefly biocontrol packages. Nonetheless, when you’re on a chemical program for Bemisia whitefly (or want to change to 1 if whitefly stress is excessive), late September or early October that is the proper time to use Kontos, as it should additionally assist management whitefly nymphs (see diagram under).
What about Biocontrol for Lewis Mite?
If you’re a facility that’s targeted primarily getting by way of 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 apart from prey mites to outlive (e.g. pollen) and are tolerant to the excessive temperatures Poinsettia are produced below.
If put within the crop early (e.g. in propagation or instantly after potting), they’ll assist maintain Lewis mite in examine – however spot sprays should still be wanted in a heat fall, akin to 2024. In line with a scorching tip from Ecohabitat ultimately 12 months’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 workers that maintain me (and also you!) within the loop for the content material of this put up!