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Cooperative Extension: Cranberries


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Grower Services - Maine Cranberry Pest Reports (this year and last)

2018 Reports:

August 16th: Haven’t seen 2nd-generation Blackheaded fireworm larvae yet, but the moths are around again so they must be getting ready!  Fruitworm levels seem about average to me.  Nobody I have visited has very much Cranberry tipworm (fantastic!!)

And . . . just an occasional Redheaded flea beetle and Bluntnosed leafhopper (I’ve been finding no more than 4 or so of each of those pests per 25 sweeps, which isn’t too concerning I don’t believe; no thresholds for those pests, but I think if you’re only seeing a few per 25 sweeps, you’re ok. They do better in drier conditions, and fortunately the second half of the season has been a lot wetter compared to the first part of the season.)

July 12th: The final keeping quality forecast is ready (Bangor didn’t pick up any additional points but Caribou gained one). Bangor finished with 6 points which translates to a forecast of “Fair to Good” and Caribou finished with 8 points, for a “Good” forecast. (MS Word) (pdf)

All seems pretty quiet now for insect pests.  I finally found some tipworm yesterday in western Maine (not Turner!), at a site that avoided frost injury this season, and so far every site that suffered some frost damage (presumably on June 4th), has conspicuously been lacking in tipworm.  I think it’s safe to say that the timing of that frost killed off the tipworm.  That is a painful way to kill tipworm, though, of course.  But a little bit of a silver lining.  Switching gears to fireworm, it appears we are between generations now, as expected.  End of July and first week of August is when I would be expecting to see 2nd-generation larvae showing up; the offspring from any that were lucky enough to escape everyone’s attacks.  Hopefully the 2nd generation won’t be a factor!

Pollination looks fine, from what I’ve seen.  And I’ve done ‘tagging’ of 20 random flowering uprights at each of three locations thus far, and the initial counts for those sites of “potential” berries per upright are: 3.14, 3.15, and 3.55.  Interestingly, the 3.15 site is organic, but still with a respectable starting number.

June 20th: Still finding Blackheaded fireworm larvae and cranberry weevils. The fireworm are mostly fully developed now so will be pupating at any time as we close out this week.  So if you want to clean out whatever fireworm larvae you still have, you’ll need to use something that will work fast (a contact material, in other words), rather than something that needs to be eaten because the larvae I’ve been finding may not feed any more before pupating.

Cold night on June 3rd into June 4th: Have seen some frost damage at a few sites due to the cold night we experienced in early June. Bangor recorded a minimum of 37 degrees for June 4th (during the overnight hours I would presume), and it was as low as 30 in Houlton.  Factor in low/pocket areas, or areas where sprinklers didn’t quite reach, and you’ve got a recipe for some frost damage (see photos), which superficially resembles tipworm injury but the leaves at the tips are folded over a lot more than what you see with tipworm, and I’ve not seen any tipworm yet, either, though it should be around some at this point. With the more seriously injured tips, a good portion of the tips turned brown (moreso than what happens from tipworm) (see photo at left).


June 1st: Blackheaded fireworm larvae and cranberry weevils are causing some problems, so be on the lookout for these two pests!  A few false armyworm and blossomworm caterpillars have started to show up this past week also, but in low numbers thus far. No signs of tipworm as yet; not enough new growth for them.

Preliminary Keeping Quality Forecast: The preliminary cranberry keeping quality forecast through the end of May is at the ‘Fair’ to ‘Good’ level using Bangor conditions (and ‘Good’ if using Caribou conditions).  Caribou has gotten 7 points and Bangor has racked up 6.  The total points possible in the model is 16.

May 21st: Be “cautiously aware” that blackheaded fireworm larvae are now hatching from their eggs so you may find some before I can get around to some additional locations. The site where they have begun to show up is a cooler location, so basically anyone in Maine might have some currently so it would be a really good idea to do some sweeps and then look carefully because they’re super duper small right now.

The only other pests I’ve seen are a few cranberry weevils and a single small gypsy moth larva.

For a review if needed:


2017 Reports:

July 27th: The 2nd generation of Blackheaded fireworm has begun in earnest.  They showed up quickly, and have progressed quickly, too. By this coming weekend, I believe that many of the larvae will be pupating; the subsequent moths will mate, and the females will lay eggs that will overwinter and give rise to next season’s ‘first’ generation of larvae.

July 21st: Cranberry fruitworm has begun to lay its eggs anywhere where there are pea-sized–or larger–cranberries (eggs confirmed in western Maine on July 17th). One viable egg was found in western Maine after checking only 13 berries, and you only need 1 in 250 berries as a trigger for spraying, so we could be looking at a heavy fruitworm year.

July 7th: It looks like the first generation of Blackheaded fireworm is now in our rear-view mirrors (i.e. in the adult/moth stage), virtually everywhere in the state. If you have any (and most sites I’ve visited have had a few), these are the offspring of the first wave of larvae that have now come and gone. Nowhere did I see a situation where the 1st-generation larvae caused a lot of damage, and hence, the reason there wasn’t a pest report posted during June.  Everyone–from my perspective and combined with my visits–appeared to manage their numbers quite well.  It remains to be seen how large the 2nd generation of larvae will be.  The numbers of moths I’ve been seeing are on the low side, so I’ll be surprised if we have any massive outbreaks anywhere. Be looking for the tiny larvae at the tops of the uprights (and by sweeping), as we get later and later into July. Their timing often coincides with one’s fruitworm spray regimen, such that the fireworm are often controlled by virtue of the fruitworm management.

Cranberry tipworm is slowly rising in the percentage of tips it has injured, as the season is progressing, but the numbers have not been high enough as yet to concern me very much.

July 6th Update:  The Final Keeping Quality Forecast is now available: (MS Word) (pdf)

May 30th Update:  Be watching for Blackheaded fireworm larvae!  Scores of them were newly-emerged (from their eggs) in eastern Maine on May 27th. So unless you were doing the late-water flood practice this season, they should be present now, developmentally. Those doing the late-water flood should see a later emergence, I believe, of the fireworm.  Western Maine had next to no insect pests as of May 24th, and a site in central Maine also had next to no insect pest activity as of today (May 30th) — just a couple of cutworm caterpillars.  The bugs are probably not very fond of these cold and rainy days!


DISCLAIMER: Pesticide registration status is subject to change and varies from state to state; therefore the author and the University of Maine Cooperative Extension cannot assume liability for recommendations. It is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. THE LABEL IS THE LAW: ALWAYS READ AND FOLLOW THE LABEL WHEN APPLYING PESTICIDES. Use of product names does not imply endorsement.


Cranberry questions? Contact Charles Armstrong, Cranberry Professional. University of Maine Cooperative Extension || Pest Management Unit || 17 Godfrey Drive || Orono, ME 04473-3692 || Tel: 207.581.2967 [email: charles.armstrong@maine.edu]

Image Description: Four blackheaded fireworm larvae with red circles drawn around them to make them easier to see in the photo.

Image Description: Photo showing some frost injury to a cranberry upright

Image Description: Cranberry stems injured by frost (Photo taken on 6/19/2018)

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Contact Information

Cooperative Extension: Cranberries
5741 Libby Hall
Orono, Maine 04469-5741
Phone: 207.581.3188 or 1.800.287.0274 (in Maine)E-mail: extension@maine.edu
The University of Maine
Orono, Maine 04469
207.581.1865