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Contents...
Light Fall for Diseases/New Stuff for 2006
Resistance Management in
Diamondback Moth
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Light
Fall for Diseases/New Stuff for 2006
David LangstonExtension Vegetable
Pathologist - UGA
The fall of 2005 has proven to be a light one fordiseases
of vegetables. Low rainfall is likely themain reason for this. Although
some diseases suchas downy mildew of cucurbits showed upsporadically,
diseases really didn't take off andcause many losses. Hopefully this
hasn't causedgrowers to become lax in their disease preventionplans
for the upcoming year. New tools for 2006 that I have and will provide
willbe the updated section of the Pest ControlHandbook (PCH) in which
you will find a newefficacy guide for succulent legume vegetables.Also,
the brassica disease prevention guide isattached to the e-mail that
distributes this newsletter.
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Resistance Management in Diamondback
Moth
Stormy SpoarksExtension
Entomologist - UGA As all producers of cole crops know, insecticide resistance
in the diamondback moth is a constant threat to production of all susceptible
crops,particularly cabbage and collards. We have already had at least
three cases of severe resistance tospinosad (SpinTor) in Georgia despite
a relativelyshort use history. These problems were somewhat predictable
with the first highly efficacious new insecticide labeled being the only
choice when fullcontrol was truly needed. With the recent additions of
Avaunt and Proclaim to our arsenal I was hoping that resistance would
be much easier to manage, but we have had reports of reduced efficacy
of both of these products and have documented a ‘decrease insusceptibility’ to
Avaunt in one population.
A number of factors contribute to our potential
forresistance problems, but two cause me the greatest concern. In the
most severe cases, growers had started year-round production of greens
about 1 to 1½ years prior to detection of the problem and had
relied heavily on a single chemistry. In the two most severe cases, the
year-round production consisted of sequential plantings within a stones-throw
from eachother. Market demands may require expanded production, but where
plantings can not be separated in time, separate them as much as possible
in space. Resistance in diamondback moth can be developed, or selected
for, on a field by field basis. Making these insects move to find new
hosts as the old hosts mature can increase ‘mixing’ with
other populations and hopefully dilute any resistance that may have been
developed within a field. This will neverreplace a host free period for
resistance management, but it can help (it all depends onoverall management
within the area).
Rotation
of chemistries is essential for resistancemanagement. When SpinTor
was first registered, there simply were not many options for rotation.
We now have three highly efficacious insecticides for diamondback moth
(except where we select for resistance) and should be using all three
along withsome of the older chemistries as well (particularly Bt insecticides).
I have had two recent problems reported with two products (Avaunt and
Proclaim in one case and Avaunt and SpinTor in another). In both cases,
the third product had been eliminated from use for one reason or another.
At this point, I would encourage producers to try and work all three
products into their diamondback moth management programs when possible.
Of course we still recommend use of any insecticide only when needed
and would also encourage use of older chemistries when they are capable
of doing the job (i.e. pyrethroids provide excellent and economical control
of loopers and imported cabbage worm if they are the primary pest targeted,
but I would not use them if diamondback were common in the field).
With
some luck, we will soon have two new products registered to aid in
management of diamondback moth and we will let everyone know as soon
as this happens. However, for now we need to do all we can to maintain
the efficacy of the products we currently have. They should be used only
when needed and rotated so that sequential generations of diamondback
moth are not exposed to the same product. With the three products we
currently have, a rotation of two sequential applications of each product,
with a minimum of one week between applications, will easily accomplish
this during most of the year.
Georgia
Extension Vegetable News
| Volume 5, No.4. |
December 2005 |
| Editor |
David B. Langston, Jr. |
| Production Assistant & Webmaster |
Paul Sumner |
The Georgia Extension Vegetable News is published bimonthly for Jan-Feb,
Sept-Oct, and Nov-Dec and monthly March-Aug. This newsletter is also
available on the World Wide Web at www.tifton.uga.edu/veg
or www.ugaveg.org.
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