Maine Cranberry Pest Reports (2019 and 2018)

2019 Reports:

Blackheaded fireworm eggs deposited singly on some cranberry leaves (21 eggs in total)
Blackheaded fireworm eggs on cranberry leaves (ordinarily a single leaf would not have multiple eggs on it, but the moths were held in captivity with very few leaves at their disposal). Photo by C. Armstrong. 8/16/19.

August 23rd: Happy to report that the 3rd-generation of blackheaded fireworm eggs still are not hatching!  With colder nights now in the forecast, and September approaching quickly, the eggs might very well remain unhatched until the spring (phew!).

August 21st: The 3rd-generation of blackheaded fireworm eggs that are being monitored daily are not–as yet–hatching!  Everyone is hoping the situation remains that way for the duration of this season!

August 16th: There is the real possibility of a third generation of blackheaded fireworm this season, as 2nd-generation moths are already laying their eggs, with half of August still to go!  Eggs (from collected moths that are now in captivity) are being monitored daily, to see if they hatch.  Updates will be shared here, and via emails with growers.  Redheaded flea beetle levels are rising, which is the normal time (August and into September) that their populations increase.  Cranberry fruitworm is definitely with us, and isn’t very hard to find on any of the beds, but levels seem to be tolerable (or at least typical) thus far.

August 1st: The 2nd generation of fireworm is definitely with us now — earlier reports were correct.  Most of the larvae found are mature and some looked to be in their pre-pupal stage.  Not everyone has them (some were lucky enough to get good control of the first generation, and/or previous seasons’ generations, such that it’s not an issue right now).  For those of you who were not so fortunate, and with a lot of summer weather still to come, keep in mind that perhaps a 3rd generation will squeak out as well before it’s all over. Other pests: Some redheaded flea beetles and blunt-nosed leafhoppers were found on July 31st, downeast (Washington County), so those pests are now active as well and right on time. Generally their populations rise throughout August and September, so be watching for those.  Don’t be alarmed unless you start finding a great many of them, consistently (on the order of 50 to 100 or so per 25 sweeps).   Tipworm continues to be pretty low, and although there was a site on July 31st with maybe 10% of tips damaged from tipworm, there were no maggots or pupae that were found in several tips that were examined at the site, and no tipworm flies were in the sweep net, either, so they don’t appear to be ballooning out of control like they used to in the past.  Fireworm is demanding most of the attention this season, and the 2nd generation has done some tremendous harm to the vines and to the yields at a few locations.  Next up is cranberry fruitworm, of course.  One fruitworm-infested berry was found already earlier this week (July 29th), in Calais.  Fruitworm could be at a high level this season due to the favorable weather conditions (warm nights, especially).  No scale insects have yet been found at any of the Maine sites.  Bee levels and fruit set have been looking really good!

July 25th:  The 2nd generation of blackheaded fireworm is gearing up (larvae were found in the Augusta area, and downeast there are reports of moths at one location and larvae at another). Anyone using Altacor® or Exirel® for fruitworm (which should be applied at 50% out of bloom), should simultaneously obtain great fireworm control because it works very well on both of those pests (it has a very long residual which helps a lot).

A bumblebee working its magic / pollinating cranberry blossoms - July 10, 2019 (Waldo County, Maine)
A bumblebee working her magic – July 10, 2019 (Waldo County, Maine)

July 15th: No concerning pest problems to report!  Bloom looks heavy, but bee levels on the beds do not look heavy, so that is a bit concerning. Bumblebee numbers on the beds seem to be higher than the honey bee levels, so far, and the native bumblebee numbers don’t seem as robust as the last few years, either.

The second generation of Blackheaded fireworm larvae has not begun as yet, or at least no 2nd-generation larvae have yet been found by our cranberry staff.  They should be present by the end of July, for any site where there was much of a first generation, and assuming that some of them survived long enough to reach adulthood.

July 2nd: Blackheaded fireworm is now between generations, with moths on the beds mating and laying eggs for the 2nd generation.  The eggs are deposited, singly, on the undersides of the leaves, so it’s not practical to try to find any of the eggs yourself.  The second generation of larvae should begin to show up by the middle of July, if your location happened to give rise to some of the moths (each mated female can lay up to 200 eggs).  Cranberry tipworm continues to be at very low levels (no more than 5% of tips being infested, at any of the sites monitored thus far).  Very few insect pests, overall, are being found on the beds at this point (in terms of number of species), which is great! The important thing now is to order up some nice, sunny days to get us through the bloom/pollination period.  Many sites have heavy blossom loads!

The Final Keeping Quality Forecast is ready. Both Bangor and Caribou finished with 5 points out of 16 which somehow still translates to a forecast of “Fair to Good” (same forecast result as last year). This forecast in the model translates to the following interpretation:

You should probably not reduce your fungicide rates and/or the number of fungicide applications. If Late Water was held, you can reduce your fungicide inputs in that situation. Keeping Quality Forecast (pdf) | Keeping Quality Forecast (MS Word)


A 1st-generation blackheaded fireworm larva - June 17th, 2019
A 1st-generation blackheaded fireworm larva, downeast Maine – June 17th, 2019. Look for the shiny black head to help with identification.

June 20th: Blackheaded fireworm is still causing some big headaches in the state, and first-generation larvae are still showing up, even in western Maine, suggesting that the egg-hatch has been significantly prolonged and asynchronous this season!  This is the latest time in June for them, in fact, that Maine has recorded, for 1st-generation blackheaded larvae to still be emerging (with the exception of possibly 2006).  No fireworm moths have been found at any of the sites thus far this season, which provides proof that the ‘late’ fireworm larvae found yesterday in western Maine are not 2nd-generation larvae (a lot of fireworm moths would be on the beds if that was the case, because they do not die that quickly).

Not many other insect pests have been showing up this week (only a few cranberry weevils now and then, an occasional gypsy moth larva, some blossomworm, and still almost no tipworm).  I’ve not found any site as yet with more than 5% of uprights with tipworm maggots inside.  Quite remarkable!  False armyworm larvae have been at surprisingly low levels this season as well.

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 ‘Poor’ if using Caribou conditions.  Caribou has gotten only 4 points thus far out of 13 and Bangor has only one point higher, with 5.  The forecast can be completed at the end of June.

June 11th: Very high numbers of Blackheaded fireworm and Blossomworm larvae to report now, for this week, for at least some of the Columbia Falls growers as of yesterday!  With the first truly ‘hot’ day of the season, the caterpillar pests are trying to take advantage and are trying to make up for lost time, essentially.  Many of the fireworm larvae looked like they had just hatched, and couldn’t have been older than a day or even a few hours in some cases.

Other Notes: 

  • Once again, the timing of young mare’s tail plants around the margins of the cranberry beds is coinciding with the emergence of the blackheaded fireworm larvae, so bear that in mind in future years.
  • Note about Cranberry tipworm: none found as yet even though this is when the eggs and larvae should be appearing; a sample of 40 brand new tips collected on June 10th from a historically ‘high tipworm’ site in Washington County were examined today–June 11th–but no eggs or larvae were present.
  • High populations of Meadowsweet plants on some of the beds in Washington County right now.
  • Preliminary Keeping Quality Forecast: Coming Soon!

June 5th: Blackheaded fireworm and False armyworm caterpillars were found in the midcoast/Lincolnville area today. So both of these pests should be starting for everyone by the end of this week if they haven’t already begun where you are.  I would suggest taking 50 sweeps (twice the minimum of 25, for added thoroughness) on each bed you wish to check, and then very carefully examining the net contents, because the fireworm larvae in particular are very small and they are easy to overlook at first.  Look for their shiny, dark (black) heads, and the backwards wiggle dance that they do when disturbed. Remember, blackheaded fireworm goes through two generations each season, so the best chance one has at keeping them out of the equation, is to control the first generation before they can produce any offspring.

May 31st: Visited western Maine; zero pests found but beds had been sprayed so I cannot as yet say what the insects are doing independent of chemicals.  Mare’s tail plants were present, which in the past has often corresponded to the start of blackheaded fireworm and cranberry tipworm. I will be visiting more sites the week of June 2nd.

May 24th: Have visited three locations thus far (one downeast on May 11th and two yesterday in central/midcoast areas), and have found zero pests thus far. The spring season is certainly on the slow side this year.


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. Keeping Quality Forecast (MS Word) | Keeping Quality Forecast (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.

Four blackheaded fireworm larvae with red circles drawn around them to make them easier to see in the photo.
Four fully mature Blackheaded fireworm larvae as seen on 6/19/2018.

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.

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

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.

Photo showing some frost injury to a cranberry upright
Frost injury as seen on June 12th but which occurred on June 4th.

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).


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.


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 any pesticide recommendations. It is the responsibility of the pesticide 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.