Insects.
Many growers report remarkably empty sweep nets this week. Generally, no counts or low counts of weevil. The cape bogs have significant black bug infestations that are not being seen in central cranberry areas like Carver. Acetamiprid (Assail, Arvida) is being tried as another option for managing these new found pests.
This is the week for scale! Based on several samples, the female scale started producing eggs and crawlers just this week. If you have active scale spots (many are old dead areas), now is the time to use your spray to manage these insects. There is variability based on area and variety, but generally this weekend is the target. Bees are in, so be sure to spray at night.
Remember, Altacor for fruitworm should not go on until 50% out of bloom or later. This is likely at least a week or two away. Super hybrids move fast with pinheads progressing to bigger fruit rapidly and the fruitworm will target these first with their eggs.
Disease.
The preliminary keeping quality forecast is VERY POOR. The final forecast will be ready next week but is unlikely to change significantly.
- This predicts that the fruit rot incidence could be high unless timely and effective disease management strategies are employed.
- Above normal sunshine hours during June, July and August (especially July) have been associated with good or better quality than predicted.
Many growers applied their first fruit rot fungicide this week or are preparing to apply it soon. Most fruit rot infections occur during the bloom period and early fruit set, before berries start to size up. Your first application should happen when 10-50% of flowers are opened. Once the fruit has set and begun to increase in size (mid-late July), fungicides are no longer necessary or effective.
Weeds.
Fireweed (aka American burn weed; Erechtites hieraciifolius) was a big problem for some growers last year. Research conducted on lowbush blueberry shows that mesotrione (Callisto) can be used to control fireweed postemergence BUT timing will be critical!!!! Almost 100% of small weeds (1.5” tall) were controlled, while almost no control was seen for weeds over 6.5” tall.
I have seen some samples of fireweed come into the lab for ID last week, so it is definitely up and ready to be treated in some spots. Scout 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.
Growers have asked about making herbicide applications during bloom. In general, if you don’t have to spray during bloom, that is always best. 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. 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 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].
Applications of concentrated Callisto solutions for poison ivy control can go out anytime now. Our research showed that by mid-June, PI has invested stored resources on growing full-sized leaves, and now it the 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. After the PI recovers from the first treatment and spends more resources on making new leaves, hit it again. The Special Local Needs (24c; SLN) that permits the use the concentrated solution is only available for Callisto; the other generic mesotrione products do NOT have this special labeling and cannot be used in this fashion.
Fertilizer.
Some growers (including State Bog) put on a modest amount of nitrogen this past week. The best fertilizer use efficiency occurs during fruiting (75% in bloom/early set) and usually occurs late June/early July. At that time, the fertilizer application should be delivering 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 have specific questions about fertilizer, please feel free to contact Peter at peterj@umass.edu
