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IPM Message for Cranberry Growers: May 22, 2017

May 22, 2017

Gypsy moth is still present and should be swept and managed for.  Cranberry weevil is being found on many bogs at threshold and now is the time to manage this insect (Avaunt).  Winter moth is wrapping up and not many are being found on bogs anymore. A few sites reported blackheaded fireworm in the last two weeks but they should be just about done.  Sparganothis fruitworm is big enough to see now and management for the 1st generation should go on now (Intrepid, Confirm, Delegate).

Cape bogs with late water should remove their floods by late May; all other locations should have their floods off by now.  Remember, frost tolerance is automatically 29.5 F once the flood is removed, no matter the appearance of the buds.  LW bogs must be swept for early season insects, especially in this year, when gypsy moth pressure is high and larvae can balloon in from off the bog.  LW bogs can be attractive sites for egg laying.  CB weevil is NOT impacted by late water so keep an eye out for those.  Generally, no fertilizer is needed on LW bogs until bloom. Casoron can be applied for dodder control to a LW bog if needed.  Apply soon after the withdrawal but be sure the bog is dry and the soil has drained.

Red sorrel (also known as sheep sorrel; Rumex acetosella) is very prevalent on bogs this spring.  The red flower clusters are visible above the vines, but the leaves are within the cranberry canopy.  Using glyphosate to wipe the flowers will not be effective, as glyphosate is mainly absorbed through the leaves.  Hand weeding is recommended for controlling this weed.  Callisto may also be effective.  If you use Callisto (either the 8 oz/A or concentrated spot-treatment rate), please let us know how it worked. 

Fertilizer: If you are using slow or controlled release, 50-100% goes out around mid-May, so we are in the window right now.  If you don’t apply 100% as CR, make up the difference with fast-acting sources. If you are using fast-acting soluble sources including the soil-applied liquids, up to 20% should go out between roughneck to hook (for all cultivars, including Rutgers and WI). Try to use fertilizer sources with a low middle number (low P). For established beds that have tissue P in the normal range, you need no more than 15 lb/A of P each year.  Check p64 in the Chart Book for more specifics on P requirements and recommendations.

If you are using pheromone traps to monitor for Spag, girdler and/or black-headed fireworm, your traps should be out by June 1.  Use 1 trap/10 acres and place them on the windward side of the bog.  Check your traps weekly, recording the number of moths captures.  Change the bait every 3 weeks and the traps as needed.  Be sure you are counting the right moths as sometimes nontarget species can be caught.  Depending on your control choice, you will use the trap counts in different ways.  If you are treating BHF or Spag with Altacor, Intrepid or Confirm, you will be monitoring for the ONSET of flight to time your applications. If using conventional insecticides, you will be monitoring for PEAK flight to time your applications.