The last frost tolerance check on May 9th had ST, BL, and hybrids at 29.5 F and 27 for EB and Howes. All cultivars at Rosebrook were at the bud elongation stage. Hopefully after the cold day today, we will enter at least a few days of warmer temperatures, especially at night.
If you are holding LW floods, floods should already be off inland locations. Coastal Plymouth County floods should be off by the 20th and Cape bogs with late water should remove their floods by late May. 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 can balloon in from off the bog. LW bogs can be attractive sites for egg laying. CB weevil is NOT impacted by late water and you should be on the lookout for those as well. We recommend NOT adding any fertilizer to a LW bog for at least 2 weeks after the flood comes off. Monitor the vines closely and add amounts based on vine response. Generally, no fertilizer is needed 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.
Non-LW bogs: If you are applying Casoron or QuinStar for dodder, in most situations you will be targeting to get your herbicides out in the next available window. Dodder will “pop” if we get the high temperatures that are predicted and the window for getting good efficacy could close pretty quickly. If you are using Callisto (especially through chemigation), hopefully your applications have gone out already.
We have reason to suspect that gypsy moth pressure will remain high and extended this season. Be diligent in your sweeps and in control applications. We did have pretty good luck with 1 qt/A Sevin last week, dropping counts in the 20-30’s to something between 3 and 10. Remember that the larvae will continue to balloon in from outside sources even if you have sprayed the bog. We assume that they must be eating something out there to continue their molting and growing even though Marty had a hard time actually “detecting” evidence of eating out on the bog.
For most situations, the window is now closed for spring applications for control of upright dieback, fairy ring, and Phytophthora. If you have any questions on these, please call Erika at x18. Fertilizer: If you are using slow or controlled release, 50-100% goes out around mid-May, so we are in that window right now.