Please note unless something pressing is happening in MA cranberry world next week, the next IPM message will be out on July 3.
There is extreme heat forecasted for several days and into next week. Keep a close eye on soil tension and avoid pesticide applications (especially herbicides) to stressed plants, if possible.
Best Management Practices recommend irrigating in the early morning (between 4-8 am), so as not to extend the time the plants remain wet (the conditions that fungal pathogens prefer). This practice of early morning irrigation also minimizes loss from evaporation, run-off and drift, which can amount to 30 percent of water that comes out of the nozzle.
Percent bloom and percent out-of-bloom are measures of cranberry development and are important for accurately timing pesticides and fertilizer applications.
- “Percent bloom”, also known as “Percent Through Bloom” is used to time fungicide sprays and fertilizer applications
- “Percent out-of-bloom” is used to time fruitworm sprays
To calculate either, you must collect flowering uprights. Walk in a line and randomly select 10 uprights. Collect at least 4 sets of 10 uprights per bed to get a good representation. The more uprights you collect, the more confident you can be in your estimate for the bog. For each set of 10 uprights, count all the floral structure (open flowers, flower pods, pinheads, fruit).
Percent bloom
(open flowers + pinheads) ÷ (flower pods + open flowers + pinheads + fruit)
Percent out-of-bloom
(pinheads + fruit) ÷ (flower pods + open flowers + pinheads + fruit)
Insects
Honeybees have arrived and are working the bloom. Bumblebees are active. The bloom is progressing everywhere and will start moving fast with the coming warm weather.
Cranberry fruitworm is flying on the bog. The cranberry fruitworm moths are looking for slightly sized up pinheads to lay their eggs on! Do not use your Altacor until you have enough berries that the fruitworm can lay their eggs into, warranting the spray. Altacor fruitworm timing is generally 50% OOB for most cultivars, especially those that have quickly sizing fruit. Howes are the exception, and that app can go on 7-9 days after 50% OOB.
Keep your eyes out for brown areas! They could be caused by golden casebearer, or it could be drought stress. The tiny brown beetles have been turning up in a number of places. The only option to manage would be diazinon and you would need a lot to warrant the spray that would challenge your bees working the bog. With the coming predicted heat, drought stress could also be to blame and can look very similar to areas of insect damage.
While weevil can still be present on the bog, it is too late to manage them. All options are incredibly toxic to bees and cannot be applied during bloom. Weevil grub are developing in flower pods where populations were high several weeks ago.
Disease
We have had some questions from growers about tank mixing fungicides used to control phytophthora with the fruit rot fungicides. We asked our colleagues in New Jersey, and they report that growers there regularly mix phosphonate fungicides (like Rampart) with Quadris Top or Proline. It is unclear if there is an added boost from mixing, but it does allow growers to target both diseases with a single spray.
If using broad-spectrum fungicides such as chlorothalonil (eg. Bravo) or mancozeb (eg. Manzate Max) as part of your fruit rot fungicide regime, they are best used early in the possible infection period (when the maximum number of flowers are open). This corresponds to early to mid-bloom (now!).
Follow all label instructions carefully, including application intervals, recommended rates, and water holding times. Be careful to follow the restrictions for maximum amount of a.i. per year AND the maximum number of applications for each compound. This is especially important to remember when you are using mixtures with azoxystrobin. For example, if you apply Abound with Indar and then apply Quadris Top both applications count towards your max azoxystrobin for the year!
Weeds
This is generally a time when not many broadcast herbicides are being applied – too difficult to get them out with the critical fungicides and insecticide sprays happening. However, this is an idea time to spot treat poison ivy (using concentrated Callisto) and also to scout for extremely fast-growing problematic weeds like phragmites and Japanese knotweed. If you have either of these growing on your bog, you should try to wipe them with glyphosate as soon as possible – do not wait until August. Both of these weeds can form extensive root systems, so managing them when they are small is important. You may need to wipe them more than once, so it can be useful to flag the areas you see them.
Despite the fact many people use the terms “glyphosate” and “Round Up” interchangeably, a grower recently pointed out that there are many products called “Round Up” that are not actually glyphosate. In the homeowner market, Round Up can contain a variety of things (like triclopyr and imazapic) that are not registered for use on cranberry and have zero glyphosate. Make sure you are paying close attention to a.i. and not just product names and also make sure that any glyphosate product you are using on bog is actually registered for cranberry use!
Fertilizer
Early fruit set fertilizers go out at 75% bloom, so some varieties may be getting close!