Insects. Most growers are still reporting relatively low insect pressure. Weevil have reached their maximum level on the bog. If you need to manage weevil, you should do it immediately. If you grow export fruit, do not wait on using your Fanfare spray as the 100-day PHI is closing in. It is too late to spray for green spanworm or blackheaded fireworm. Most larvae have completed development and pupated. We should start to see moths soon. The Koppert bumblebee quads are arriving mid-week this coming week and honey bees should start rolling in a week after that.
Scale infestations appear to be down compared to previous years, but there are still some pockets of trouble. Many growers believe they have scale but unless you see orange colored dieback, there is NOT active feeding or an active infestation. Where active scale can be found (few and far between) the females have NOT started to produce eggs, so it is still too early to treat. Once we see eggs develop, crawlers follow in about a week.
Unfortunately, it is still too early to spray for scale! 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 regarding timing and bees.
Black bug and blunt-nosed leafhopper nymphs 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.
Weeds. Poison ivy is up and thriving. It is flowering now in many spots. Unfortunately, most poison ivy on bogs is very low growing. It is mixed into the cranberry canopy and not tall enough to wipe with glyphosate. 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 approach 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.
Disease. We are rapidly approaching bloom. Most fruit rot infections occur during bloom and early fruit set. You should have your fruit rot fungicides plan ready. The first application should happen when the bed is 10-50% through 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.
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, so plan to make an application when the vines are 75% in bloom/early set (occurring late June/early July). 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 have specific questions about fertilizer, please feel free to contact Peter at peterj[at]umass[dot]edu (peterj[at]umass[dot]edu).