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IPM Message for Cranberry Growers: Aug 2, 2019

August 2, 2019

Even with the incredibly hot weather we are and will be experiencing, there is little value to applying additional fungicides at this point in most situations.  You will do more to conserve and preserve fruit integrity by maintaining good soil moisture, adequate irrigation, and perhaps doing some mid-day cooling when indicated.  Short irrigation periods can decrease canopy temperature by 30-40°F and avoid scalding as long as soils are not saturated and no puddling occurs. Data support low efficacy with late summer applications of fungicides to control fruit rot, so please do not waste your money.

Other items to keep in mind with the stressful conditions: Yellow vine syndrome may show up, especially on vines that are stressed for other reasons, such as Casoron applications or other issues.  Keep in mind too that cranberry vines will not metabolize herbicides as readily when they are stressed and you may see “flashing” after you apply Callisto (or other mesotrione products).  The vines should grow out/recover from both of these issues.

Weevil have moved off bog and back into the woods, so no sense to chase them now.

If you have dodder on your bog, you can rake it once to open up the canopy.  You can use hand-held flame torches to keep it from setting seed; this is very helpful. You need to do this as soon as you can but certainly before the seeds are formed.  Concentrated solutions of Callisto (1.5 oz/gal) are also effective on dodder (best if the dodder has not yet flowered, but can still help even if flowers are there).

If you plan to do tissue tests, collect your samples from mid-August through mid-September. You can get your samples analyzed locally or send them off to UMass for analysis. Samples should contain no more than the top 2 inches of growth (no roots, soil, runners, or fruit). Collect tissue from vegetative and flowering uprights. You typically need about 1 cup of vine tissue. Do not collect samples when the vines are wet and do not send the samples in plastic resealable bags. Always request nitrogen determinations when you submit your samples.

If you are still applying pesticides (e.g., 2nd application of Ridomil or Aliette for Phytophthora), be sure to observe all needed PHIs.  Ridomil products have a 45-day PHI; Aliette has a 3-day PHI.  Callisto has a 45-day PHI, QuinStar, Poast and Select are 60 days.