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A
NEW DEFENSE AGAINST SPIDER MITES All
rosarians know that the two-spotted spider mite (tetranychus urticae) is a serious rose garden pest. This nearly
invisible insect works on the bottoms of leaves sucking the chlorophyll out of
them. Spider mites can take a healthy bush to a leafless stick in a matter of
days unless thwarted by constant vigilance of plant health and condition, and by
an intensive spray program using Avid to kill the adult mites and Hexygon to
kill the eggs and larva, or Floramite to kill all life stages. The
aforementioned chemicals all work as contact or, at best, translaminar (i.e.,
Avid) sprays so special care must be taken to spray the undersides of the leaves
– Avid, being translaminar, does penetrate the leaf structure and will move
from the top surface to the bottom, but it only kills the adults. The life cycle
of the spider mite – from egg to adult – is five to 20 days depending on
factors such as temperature and humidity. If you don’t get all life stages
when you spray, the mites will probably return, and they may have become
resistant to the spray(s). But help is on the way! Bayer
Environmental Science has just announced the registration of a new miticide,
based on a proprietary new chemistry with a unique mode of activity. The name of
this new miticide is Forbid 4F, and
its active ingredient is spiromesifin, a tetronic acid, which blocks fat
synthesis so the mites dry out and die. This mode of activity, inhibiting lipid
biosynthesis thus causing dessication (i.e., drying-out), is virtually the same
as that of soaps and oils. That is, the MOA for Forbid 4F can be considered, for the sake of simplicity, to be MOA 6
as defined in papers elsewhere on this website, and in articles appearing in the
Rose Society’s newsletter, Basal Breaks.
This is great because MOA 6 has little or no potential for the development of
resistance – an analogy[1]
would be a flamethrower: you may miss some of your targets, but when they return
they’ll be no less vulnerable to the flame. Another
feature of Forbid 4F is that, like
Avid, it is translaminar. The active ingredient, spiromesifin, while not
systemic (i.e., it does not move through the plant’s vascular system like, for
example, Merit does), is absorbed by the plant’s leaves and will move from the
tops of the leaves to the bottoms where the mites feed. This ability to move
from the tops to bottoms of leaves significantly reduces the tedium of the spray
process – while care should still be taken to cover the entire bush, rigorous
spraying of the undersides of leaves should not be required. Moreover, according
to Bayer, Forbid 4F controls mites at
all life stages and
offers an excellent residual of four to eight weeks for mites. The
label for Forbid 4F indicates its
toxicity rating is CAUTION (be aware that the Avid label carries a WARNING
designation). The label further specifies a usage rate of 2 to 4 fluid ounces
per 100 gallons of spray. This equates to 1/8 to 1/4 teaspoon per gallon of
spray – Bayer recommends, however, using the lower rate. Also, Forbid
4F may be tank mixed with sprayable fertilizers, insecticides and
fungicides, although Bayer recommends a jar compatibility test. This product is
available through Bayer distributors, such as Southern Ag ( http://www.southernag.com
) in REMEMBER: Read the Label! |
