Insect Management. This year is a very different year from past years! Insect reports have been very low. However, with the 5 days of heat, we have finally seen some insect action. Reports of weevil exceeding threshold have been pouring in, but many other sites are curiously low, and few have chosen to treat. Cutworms (both false armyworm and blossomworm) have been seen more than they have in past years but still at low numbers and range of size. Only one treatable green spanworm bog has been found. Sparganothis, black bug, and leafhopper nymphs have been found but very rare. Sweep nets have had an array of the collembola (or springtails) that are abundant on bogs – remember that they are NOT a pest. Insect Clinic II is next Tuesday 5/26/26 8-10AM. This is a good review if you are not familiar with all these bugs on your bog.
Weed Management. Sheep sorrel, aka red sorrel (Rumex acetosella), is flowering now, and is suddenly very visible everywhere because the tall flower stalks extend above the cranberry canopy. This is a perennial plant. It is not usually very competitive with established cranberry plants. It is generally only found in new plantings or in areas where vines are thin and is considered more of a nuisance than a truly problematic weed issue – however more growers are reporting this weed showing up in area with thick vine and closed canopy.
At this time of year, there are not effective postemergence herbicide strategies you can use. The historic recommendation for sheep sorrel is to use Casoron in the spring (before budbreak). If you find patches in established beds, consider mapping those areas now so you can spot treat with Casoron next spring. Also, too late for this year, but an early spring preemergence application of Spartan (sulfentrazone) may help control red sorrel (again, too late for this year but make a note for next year). Mesotrione (Callisto) at this time is NOT effective on this weed. It is possible that earlier applications may be more effective – by the time you notice sheep sorrel it is already well into making flowers/seeds! For many weeds, herbicide efficacy DECREASE as plant size/stage increases.
Cranberry plants can be sensitive to some herbicides during roughneck. This is a period of rapid growth and lots of tender new tissue is present. Even herbicides that don’t cause obvious injury can still impact the plant. A good example of this is how clethodim products applied during roughneck can cause deformed flowers later in the season. Other active ingredients, like Kerb, appear to safe during this stage.
For information on managing grasses and dodder, see previous IPM message or contact Katie 508-970-7634.
Disease Management. Cranberry plants are in the treatment window for Upright Dieback as buds break and expand (but prior to roughneck). Chlorothalonil remains the preferred option for Upright Dieback management, but most handlers have a 120-day PHI restriction for export fruit (5/25/26 puts PHI to 9/22/26).
Many disease issues, including Phytophthora root rot, are associated with poor drainage and saturated soils. You can significantly improve disease management by taking steps to improve drainage.
If you have a confirmed Phytophthora infection on your bog, Ridomil (phenyalamide fungicides) and Rampart (or similar phosphonate fungicides) can be used whenever soil temps are warm enough to for root growth to occur. Ridomil is soil applied (watered in after application) while Rampart is used as a foliar (does not get watered in). Multiple applications may be needed to achieve control.
If you suspect Phytophthora root rot, Upright Dieback, or have any disease diagnostic or management questions, please contact Leela Uppala 508-970-7644.
Spring Fertilizers. Some growers that experienced winter injury last season were conservative with their fertilizer. Are your vines are looking a little hungry this spring? According to the Chart Book you can apply up to 20% of your total nitrogen budget at roughneck. For example, if you plan to apply 40 lbs. N/A this season you can consider applying up to 8 lbs. N/A at roughneck (applying the remainder at early set and late set). This recommendation is for regular fertilizer (not slow or controlled release).