Section 18 Specific Exemption Approved for Quintec to Manage
Cucurbit Powdery Mildew in NY in 2006
Quintec 2.08SC (EPA Reg. No. 62719-GTL) can be used in NY
for cucurbit powdery mildew following granting of a specific exemption by EPA
to NYS DEC. This use was requested
because powdery mildew cannot be controlled effectively on the lower surface of
leaves with currently registered fungicides due to resistance to QoI and DMI
fungicides and usage constraints on the label and in the FRAC resistance
management guidelines. This
exemption includes all counties in
New York State. Quinoxyfen, the active ingredient in Quintec, has a new mode of
action not in any registered fungicides. It is in FRAC Group 13. Cross
resistance has not been detected with other fungicides. Although
it is not systemic, it moves into leaf surfaces and redistributes, and it has a
vapor phase. Excellent control achieved
on the underside of leaves is thought to be due to redistribution
via its vapor phase. Quintec is
currently registered by EPA on grapes, hops and
cherry. It is marketed by Dow AgroSciences LLC.
Quinone outside
inhibitor (QoI) fungicides, a.k.a. strobilurin fungicides (FRAC Group 11) are no longer adequately effective because
of resistance. The qualitative nature of this resistance (meaning pathogen
isolates are either sensitive or highly resistant) and general cross resistance
among QoIs means obtaining control with this group of fungicides where
resistance occurs will be difficult. Poor control was evident in commercial pumpkin fields monitored on Long
Island in 2003.
Resistance to demethylation inhibitor
(DMI) fungicides (FRAC Group 3) is
also widespread. This type of resistance
is quantitative, meaning isolates of the pathogen exhibit a range in
sensitivity to a DMI depending on the number of gene changes. Pathogen isolates also exhibit varying
response to different DMIs depending on their activity. In the USA, resistance
to DMIs in the cucurbit powdery mildew pathogen is at the point that Bayleton is no longer effective while Nova is
still effective at high rates despite reduced sensitivity. Nova applied at lowest label rate has been associated with
poor control. There continues to be
concern that using Nova or Procure, another DMI, unwisely (not in alternation
with other mobile fungicides in a good resistance management program) will
eventually select for pathogen strains with greater resistance to this group of
fungicides such that these are no longer
effective. Including Quintec in fungicide programs will facilitate
effectively controlling powdery mildew and managing resistance to DMI fungicides.
Quintec can be applied a maximum of 3
times at 4 fl. oz./A with a minimum of 10 days between applications as a foliar
spray to melons, winter squash, gourds, and pumpkin (non-edible peel cucurbits)
from July 1 through September 30. Consecutive applications are not permitted to
minimize selection pressure for resistance. Maximum allowed per acre is 12 fluid ounces. Pre-harvest interval is 3 days. To minimize risk to non-target organisms,
label restrictions require applications be made between one-half hour after
dawn and one-half hour before dusk, only when there is a wind away from
fish-bearing waters, and where there is a well-maintained vegetative buffer
between treatment area and fish-bearing waters. Users
must have a copy of this label when they use this product. Quintec labels can be obtained from local
distributors and the extension office as well as at http://pmep.cce.cornell.edu/regulation/sec18/2006/index.html.
Quintec has provided excellent control of
powdery mildew on lower surfaces of leaves as well as on upper leaf surfaces. In
2 recent fungicide evaluations conducted at Cornell in Riverhead, best control on the lower leaf surface was obtained with Quintec: 86% in 2003 and 98% in
2004. Quintec was applied alone on a
7-day interval to determine its efficacy in these experiments, a use pattern
that should never be used in a commercial field. Similar level of control was achieved in 2004
using an alternation program with Procure plus the protectant sulfur applied each
weekly. The fungicide programs tested in
2003 were less effective than Quintec alone because they included a QoI fungicide rather than Quintec.
A recommended fungicide program (7 to 10
day interval) for 2006 consists of Quintec plus a protectant fungicide (sulfur,
chlorothalonil, copper, etc.) applied in a 3-way alternation with other mobile
fungicides, a DMI fungicide (Procure or Nova at high label rate) and Pristine (FRAC
Group 7 and 11), plus a protectant
fungicide with each. Pristine contains another new fungicide, boscalid, as well
as a QoI fungicide. The first application should be made either preventively or
shortly after detecting powdery mildew at the action threshold of at least 1 of
50 old leaves with symptoms. Quintec,
like the DMIs, has a narrow spectrum of activity. Therefore it is critical to monitor crops for
diseases other than powdery mildew.
Please Note: The specific directions on fungicide labels
must be adhered to -- they supersede these recommendations, if there is a
conflict. Any reference to commercial
products, trade or brand names is for information only; no endorsement is
intended.
