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IPM Message for Cranberry Growers: Apr 15, 2011

April 15, 2011

General Preemergence Herbicides.  Now is the time to be applying Devrinol, Casoron, and Evital for preemergence weed control. Water Casoron in well after application; you want the herbicide in the top soil layers.  Casoron volatizes easily so avoid applying when air temperatures exceed 60 F.  Soil temperatures should be warm (50 F) so that you will get the boundary layer formed to get the best weed control (you want volatilization in the soil!).  It is always best to NOT apply PRE herbicides just before a string of frost events, if possible.  However, applying before a single frost event should be no problem.  Devrinol should be watered in, too; you want the herbicide off the foliage and into the soil.

Frost. The tolerance for EB and Howes is 18 F; ST and BL are considered to be at 20 F.  The new hybrid varieties seem to be closer to Ben Lear and Stevens, so growers with those varieties should gauge their protection needs on those varieties. The CCCGA’s frost service will be activated as of April 14 for all eligible members.

Winter Moth. We have a fact sheet for winter moth available ( Eggs begin hatching in mid-April.  Larvae are usually seen mid-late April.  The newly emerged larvae look like black-headed fireworm larvae; it is very hard to tell them apart at this stage.  Young larvae can be quite voracious and do a lot of damage.  The current thought is that if you find an average of 10 or more, you should consider treating.  Once winter moth caterpillars become free-feeders, they are easier to control but have likely done most of their damage by that point.  Be prepared to sweep early than usual (early May) and sweep more often, especially if you have had injury in the past.  Intrepid and Delegate are probably the best choices; Orthene and Avaunt are good choices; Sevin and Diazinon are NOT good choices as spanworms are often resistant to these compounds.  Here is a link to the UMass Landscape’s fact sheet on winter moth:

QuinStar. EPA granted our emergency exemption request for the use of QuinStar for dodder control for 2011.  You can use up to 12.5 fl. oz/A per application of the 4L, not to exceed 16 fl. oz/A per season with a maximum of two applications.  You can apply up to 8 oz/A per application of the Dry Flowable formulation, not to exceed 10 oz/A per season with a maximum of two applications.  Irrespective of which formulation you use, you cannot exceed a total of 0.50 lb active ingredient/acre per season.  Handlers have varying policies on the use of QuinStar for 2011.  All growers should verify that their handlers will accept fruit treated with quinclorac PRIOR to using the herbicide.

Applications made earlier in the season (pre to early postemergence of dodder seedlings) seem to be most effective.  For this year, I would guess application would go out May 10-15.  Scout for early emerging seedlings on your bogs and time your application based on the appearance of seedlings.  Applications made once dodder has securely attached to its host are much less effective.  It is better to be EARLIER with QuinStar, rather than TOO LATE.  A 30-day interval must elapse between applications and QuinStar has a 60-day PHI.  If you have any questions about using QuinStar, please call me at ext. 21 and/or contact your handler.