Cranberry Station Newsletter 2024 Vol. 25:5

Final Keeping Quality Forecast

By Leela Uppala and Peter Jeranyama

The final forecast is VERY POOR keeping quality. 

 We obtained “2” points out of a possible “16” to arrive at this keeping quality forecast for the 2024 Massachusetts cranberry crop. This score makes the final keeping quality VERY POOR.  

 Implications

• This indicates that fruit rot incidence could be high without timely and effective disease management strategies.
• Fruit quality may suffer if fungicide use is reduced.
• However, in beds where late water was held this spring, fungicide inputs can be reduced in that specific scenario.
• Be extra cautious and conservative….

….if the beds are cultivated for fresh fruit.

….if the beds were not treated or sprayed with fungicides last year.

….if the beds had significantly higher fruit rot in the previous year.

Additional Notes

• Follow all label instructions carefully, including application intervals, recommended rates, water holding times, and pre-harvest intervals.
• Alternate fungicides with different modes of action. Use FRAC (Fungicide Resistance Action Committee) codes on the labels to determine the mode of action. Fungicides with the same FRAC codes have similar modes of action.
• Above average sunshine hours during June, July, and August (especially July) have been associated with better-than-predicted fruit quality.

News from the Weed/IPM Lab

By Katie Ghantous

Kerb use is approved as an Emergency Exemption for 2024 in MA (Section 18) for dodder control, and this label expires on June 30, 2024. If you used Kerb, you must report the use to MDAR. The Kerb Applicator Reporting Form 2024 can be found on our website with the Special Labels https://ag.umass.edu/cranberry/services/special-pesticide-labels. 

Growers have been asking about making herbicide applications during bloom.  In general, if you don’t have to spray herbicides during bloom, it is best to avoid doing so.  However, herbicide efficacy is often based on growth stage of the weed, so if you need to spray during bloom, you can usually do so without impacting the crop.  We have not experienced or heard of growers having issues with using Intensity One or Callisto during bloom, and NIS appears to be safe for use with these herbicides during this timing too. Crop oil carries a risk of injury to plants and delicate flowers. Avoid using crop oil during bloom and any other time that it is hot and humid: [air temp + relative humidity = +150 ºF].  

Fireweed (aka American burn weed; Erechtites hieraciifolius) was a big problem for some growers last year. This is an annual weed (germinates from seed, flowers, and dies every year). If you had it last year, and did not treat with a preemergence herbicide, be on the lookout for it. I have seen some samples of fireweed come into the lab for identification last week, so it is definitely up and growing.

We are currently researching the efficacy of different preemergence herbicides in a greenhouse study on fireweed seeds and should have better recommendations for preemergence control for next spring. Casoron has been the historic recommendation, but preliminary results show that several other herbicides may also give control.

Research conducted on lowbush blueberry shows that mesotrione (Callisto) can be used to control fireweed postemergence BUT timing is critical. Almost 100% of small weeds (1.5” tall) were controlled, while there was almost no control of weeds over 6.5” tall.  Scout your bogs and treat when plants are small.  Remember, it looks very different at this growth stage than it does with the iconic tall flower stems standing tall above the vine. You want to treat it BEFORE it is taller than the canopy. Once the fireweed reaches the height of the canopy, it is likely too late for mesotrione to be effective.

Red sorrel (aka sheep sorrel; Rumex acetosella) was flowering for several weeks and was very visible everywhere!  It is a perennial plant that can thrive in acidic and sandy soil. Once it becomes established, it is difficult to hand-weed since plants spread underground by rhizome. It is not usually very competitive with established cranberry plants. When found growing in beds it is generally only in new plantings or in areas where vines are thin. In the past, it was considered more of a nuisance than a true weed issue. If red sorrel is becoming more widespread in healthy, established beds with good canopy cover – we may need to spend more time researching this weed!  Please let us know if this weed is becoming more problematic for you kghantou@umass.edu.

Unfortunately, there isn’t much you can do to manage red sorrel at this time of year. The historic recommendation is to use Casoron preemergence in the spring. If you have patches in established beds, consider mapping those area now so you can spot treat with Casoron next spring. There is some research in other crops that shows sulfentrazone (Zeus/Spartan) may control red sorrel (again, would be preemergence next spring.

Research from lowbush blueberries showed that there is very variable red sorrel control with mesotrione (Callisto) postemergence – which aligns with cranberry growers’ observations and test plots we have treated. Most growers report that they have tried Callisto as a postemergence AFTER they noticed the red flowers everywhere - and have not gotten good results. It is possible that earlier applications when the plants are very small may be more effective – but by the time red sorrel is noticeable, it is already well into making flowers/seeds. For many weeds, herbicide efficacy DECREASE as plant size/stage increases.

Poison Ivy can be suppressed with spot treatment applications of concentrated Callisto. The spot treatments can be made anytime now.  Our research showed that by mid-June, PI has invested stored resources on growing full-sized leaves, and this was an ideal time to knock it back with a spot treat of concentrated Callisto (see Chart Book or contact me for more details). It is most effective to treat twice in each year. The second application should occur several weeks later after the PI recovers from the first treatment and spends more resources on making new leaves. This tactic forces the PI to deplete resources that are stored in the roots, as well as prevents it from having a long growing season to store more resources and spread. If patches are large and well established, it may take multiple years to eradicate the PI. The Special Local Needs (24c; SLN) that permits the use of the concentrated solution for spot treatment is only available for Callisto; the other generic mesotrione products do NOT have this special labeling and cannot be used in this fashion. You are limited to two applications of mesotrione per year (whether that is made as a broadcast or spot treatment).

Haircap moss (Polytrichum commune) has been the most widespread and “weedy” moss on MA cranberry farms in recent years. Unlike the sphagnum mosses that are found in wet spots and can be partially managed by improving drainage, haircap moss grows well in dry areas and can significantly reduce cranberry yields. I have heard from a few growers questioning whether Zeus/Spartan is not working as well on moss this year. I have not seen the sites in question, but have a theory based on what we are seeing on State Bog.

We had excellent results controlling haircap moss with Zeus/Spartan. After two years of use, the once widespread and dense haircap moss is now only found in small patches on our farm. But nature hates a vacuum and there is now another species of moss (or perhaps a few different species) that seems to be thriving now that the haircap moss is gone. The sulfentrazone does not seem to control these other mosses as well as it controls haircap moss. The main species we found on State Bog was identified as bog groove-moss or ribbed bog moss (Aulacomnium palustre).

If you feel like sulfentrazone did not work well for you for managing moss this year, please let me know. I would like to see what kinds of moss you have on your farm.

Review of grass control with herbicides. There are two herbicide active ingredients that are registered for grass control in cranberry. Sethoxydim (Poast) and clethodim (Select Max, Intensity, Intensity One, etc.) are similar to each other. These herbicides are most effective on actively growing grasses BEFORE they flower. These herbicides injure grasses by interfering with an enzyme that grass plants need to make cell membranes. They work best when the grass is in the process of adding new cells and increasing in size. So, while some grasses may remain green through the winter (like the center of a poverty grass tussock), which shows the grass is living, it is not in a state of active growth. Simply being green/alive is not a good indicator for when to use these herbicides. Target a time when the grass is increasing in size.

Various grass species are at different growth stages now. Some have already flowered, while others are still not actively growing. If you missed the window and the grass you want to manage has already flowered, you might still get some control, but it may not be very effective. Poverty grass is now in a phase of active growth in many areas, and this is the time to treat it!

Intensity One is the ONLY grass herbicide that can be chemigated. Be sure to get a copy of the SLN (or 24c) label to make a legal application. The SLN also allows applications throughout hook and fruit set, but again, this is only for Intensity One. All the grass herbicides need adjuvant to work well, and all of the labels call for NIS or crop oil to be included. Read the label to determine the proper adjuvant for the product you are using. They have little to no soil activity and can only enter the plant through the leaves. Avoid run-off to keep as much material on the grass leaves as possible. ONLY Intensity One can be applied through the chemigation system (SLN label for MA).

QUINCLORAC AND CRANBERRY

Cranberry recently got an EU MRL, which has prompted some (but not all) handlers to change their quinclorac restrictions for export use.  Unless you have heard of a change directly from your handler, assume that the code book restrictions from earlier in the year are still in effect.

With these new changes many growers are wondering how and when to use it! We have had QuinStar registered for over a decade now but have seen very little use across any of the growing regions due to the export issues. It is known to control dodder and yellow loosestrife, but it probably has a much larger weed control spectrum in cranberry that we have yet to discover.

Quinclorac is absorbed by germinating seedlings, plant leaves, and roots. It is then translocated throughout the plant. While some species are susceptible to injury from this herbicide, others are not – it is “selective”. Tolerant plants like cranberry still absorb the herbicide, but it does not impact their growth. We have had many growers tell us that they observe dodder control the year AFTER they have applied QuinStar. It is possible that the dodder is being exposed to the herbicide THROUGH its connection to the cranberry plant, rather than absorbing it directly through its own stems.

QuinStar and adjuvants. For postemergence applications, it is recommended that quinclorac be used with crop oil concentrate (COC; 2 pt/A) instead of NIS. According to the registrant, performance will be reduced, and efficacy will also be less consistent without the addition of crop oil. Crop oil has the potential to injure cranberry plants when used in hot, humid conditions. Before applying a spray with crop oil included, add up:

Air temperature (ºF) + Relative Humidity (%RH) = 150 or more, do NOT use crop oil!

If the weather conditions make it too risky to use crop oil and you need to make an application, you can add NIS. It will not work as well as COC, but it is better than not including any adjuvant at all.

Weed management with QuinStar. The traditional recommendation for yellow loosestrife control is to apply QuinStar 4L (up to 8.4 fl oz/A) in early July after cranberry bloom is finished (when the YLS is about to flower or has just begun to flower). A second application of up to 8.4 fl oz/A can be made at least 30 days after the initial application. Note that perennial plants may take more than 3 weeks to show symptoms. The full effect of the herbicide may not be evident for 3-6 months after application (or even not until the next growing season)!

Past research from New Jersey indicates that for dodder control, an early season application in late May or early June (when dodder is germinating and beginning to attach to cranberry), followed by a second application in July after cranberry bloom was effective for control. As mentioned earlier, some growers feel they see dodder control the year after they apply QuinStar.

Growers have asked whether we can get grass control with QuinStar, but it is unclear at this time which of our grass weeds it will control and what it won’t. Quinclorac products are used extensively in turf, so many grasses are known to be tolerant. Crabgrass and barnyard grass are susceptible, and it is likely that some grass species we encounter as cranberry weeds will also be susceptible. If you are planning to apply QuinStar to a bed with grasses this summer, please let me know. I would like to collect some info on what species are present and how the herbicide worked on those species.