Upcoming Insect and Disease Clinic. 2 pesticide credits, free
Thursday, June 12 8-10AM, In-person, AD Makepeace Room, UMass Cranberry Station
Interested in Internal Fruit Feeders?? Get a review of the history, the lifecycle, and the management of our two biggest summer pests in cranberry, Sparganothis Fruitworm and Cranberry Fruitworm. In addition, there will be a quick review of our other big problem; fruit rot, including a discussion of the limited options available to manage. Hosted by Marty Sylvia, Crysta Taylor (Ocean Spray), and Leela Uppala
Insects
Hopefully bogs are pretty clean now! It is too late to spray for green spanworm or blackheaded fireworm. Most of the larvae have completed development, pupated, and the first moths of both species have started flying. Weevil sprays should be wrapping up as honeybees are arriving soon. The Koppert bumblebee quads arrived this past week.
Unfortunately, it is still too early to spray for scale! Infestations appear to be down, but there are still some pockets of trouble. In the infested sites, we have just started to see females that have produced eggs, so crawlers will follow in about a week. The scale are not vulnerable to insecticides until the crawlers are released. Hold off on sprays until that time. This continues to put us in a very hard place.
Black bug and blunt nosed leafhopper continue to be found on some bogs. Black bug nymphs are a bit bigger now and green. Leafhopper nymphs continue to be tiny and can be yellow, white or a bit darker. Both are cause for concern.
Disease
As we are rapidly approaching bloom (at scattered bloom in many place and already well beyond for some spots), you should have your fruit rot fungicides plan ready. Most fruit rot infections occur during bloom and early fruit set. The first application should happen when the bed is between 10-50% bloom, with many growers starting when around 30% of flowers are open. If you are considering using broad-spectrum fungicides such as chlorothalonil (e.g., Bravo) and/or mancozeb (e.g., Manzate Max) as part of your fungicide regime, it is recommended to use them when the maximum number of flowers are open (early to mid-bloom).
Phytophthora species thrive in poorly drained or water-saturated soils. Improving drainage through practices such as sanding, replanting low areas to bring them up to grade with the rest of the bog, and maintaining ditches is critical for disease prevention. Chemical control should supplement, not replace, cultural practices and should only be considered after laboratory confirmation of Phytophthora presence. For any management questions or help identifying disease, contact Leela (suppala[at]umass[dot]edu (suppala[at]umass[dot]edu) or 508-970-7644).
After drainage is improved, what can be used to treat Phytopthora in cranberry?
There are two types of fungicides that can be used to treat this disease in cranberry.
- Phenylamide fungicides (e.g., Ridomil, Ultra Flourish) are generally more effective in heavily infected areas. Should be applied as a soil drench during active root growth (June to August). These fungicides are more prone to resistance than phosphonate fungicides.
- Phosphonate fungicides (e.g., Rampart, Aliette) are better suited for prevention and suppressing early infections; and also known to induce plant defense against the pathogen. Less prone to resistance than the phenylamide fungicides.
What is the best way to time applications of each product?
- Phenylamides (e.g., Ridomil, Ultra Flourish) should be applied during active root growth periods (typically June to August). These fungicides need to be taken up by roots, so timing with active root development is critical (when soil temperatures are above 60°F).
- Phosphonates (e.g., Rampart, Aliette) are also best applied during active plant and root growth. Most phosphonates have little to no PHI, offering more flexibility in application timing.
Why is Ridomil soil-applied and Rampart foliar-applied?
- Phenylamides like Ridomil are absorbed only through roots and moves upward in the plant (via xylem). Therefore, it must be applied with enough water to reach the root zone.
- Conversely, foliar application is most effective for the phosphonates (e.g. Rampart). They are absorbed through the leaves and translocated within the plant to the roots.
Some growers might be watering in Rampart, even though it’s labeled as a foliar application. If Rampart is watered in, does it decrease efficacy?
- Do not water in phosphonates like Rampart! When applied to the soil, phosphonates can bind to soil particles or break down, reducing their uptake and effectiveness.
- Foliar uptake is essential for systemic movement. Watering in Rampart likely reduces overall efficacy against Phytophthora root infections.
Weeds
Fireweed (aka American burn weed; Erechtites hieraciifolius) was a problem for some growers last year. This is an annual weed (germinates from seed, flowers, and dies every year). It does not have a big root system, and while it “looks bad”, it is unclear if this weed is actually competing with cranberry and reducing yields.
Our research showed that mesotrione (Callisto) can be used to control fireweed both preemergence (before the seeds germinate) and very early postemergence BUT timing will be critical!!!! The study showed it was highly effective on small plants (100% control when weeds are at the 4-6 leaf stage, 3” tall or under) but not effective at all (almost 0% control on plants over 6” tall). Since the cranberry canopy is about 6”, this means that once you can see fireweed it is too late! Scout and treat when plants are small.
Seeds are germinating now and what plants are out there are tiny, so you still have time to treat with Callisto (or other mesotrione product).
Fireweed in sand on bog 6/2/25
Poison ivy is up and thriving. It is flowering now in many spots. The best tool we have for managing this weed is to make two applications of concentrated Callisto (1 to 1.5 fl oz/gallon + 0.3 fl oz NIS (or 1.3 fl oz crop oil) applied by backpack sprayer). A single application may knock it back a little, but two are needed to see significant control. The most effective timing is to treat now(ish) (once the PI is fully leafed out), and then make a second application after the foliage has regrown (approx. 3 to 4 weeks after first application). See the Chart Book for more info. Remember you can only make 2 applications of Callisto per bed per year.
Fertilizer
This is not the time of year for heavy fertilizer use. Some growers apply a modest application of nitrogen ranging from 5 to 13 lb N/acre (up to 20% of the total nitrogen needed for the season) during roughneck/hook.
The best fertilizer use efficiency occurs during fruiting (75% in bloom/early set, occurring late June/early July). At that time, fertilizer application should be made applying approximately 55% of the total nitrogen needed for the season. Another application can be timed for 75% out of bloom (late set) to deliver the remainder of the nitrogen needed for the season.
If you anticipate reduced yield in 2025, consider decreasing the seasonal nitrogen to account for the smaller demand by the plant.
If you have specific questions about fertilizer, please feel free to contact Peter Jeranyama at peterj[at]umass[dot]edu (peterj[at]umass[dot]edu).