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

2013 Reports:

August 12th: Red-headed Flea Beetles are still to be found (if you have them) and Blackheaded fireworm is mostly in the moth stage again. In other words, the 2nd-generation of larvae have metamorphosed into moths, which are now hanging out on the cranberry beds and mating.  They flutter and dart about when walking through an infested area, and they tend to remain in the patch (or patches) where the larvae were.  Most years, the eggs these moths lay now will overwinter, but, it is possible there is still time for a 3rd generation to run its course before winter sets in (something I will be looking for).  Cranberry fruitworm is with us, but I do not have a fix yet on the extent of its pressure this year.  I collected Stevens berries from an organic site this past Thursday, and after examining 50 of them so far, have found no evidence of fruitworm (which is encouraging).  I will be examining more of the berries tomorrow from the same location.

July 25th: This period of the crop stage used to–in the past–be a fairly quiet time for us for pest activity, with everyone focusing primarily just on cranberry fruitworm and fruit rot control.  However, be on the lookout for a relatively new actor on our stage: Red-headed Flea Beetle.  I found high numbers (12+ in 25 sweeps) of them at a site in Washington County this week, and another site in the Columbia Falls area registered “1″ on July 19th (1 per 25 sweeps is not high enough to worry about, but, it does indicate–in conjunction with the outbreak I found at the other site three days later–that they are around so growers should be on the lookout).  There is no action threshold in place for this pest, but, if you are seeing a dozen or more per 25 sweeps, I think I would be concerned.  They feed on the  the undersides of the leaves, while usually leaving the top leaf surface intact. But they also gouge the berries, and overall, their feeding can significantly impact bud development for the following year if their populations are high.  I also found Blackheaded fireworm larvae (2nd-generation), as I suspected, in Washington County this week (well over the threshold).  They were abundant enough and far enough along to spot the closed-up tips while walking through the infested areas, and roughly 40% of the stems exhibiting that tell-tale, flagged-over/closed-up appearance at the tips–when I opened them up–revealed a larva inside.  So they are definitely with us now.  Last, but not least, Cranberry fruitworm has begun laying eggs on the berries.  Berries smaller than garden peas, in size, are at lower risk than are those that are pea-sized or larger.  I examined 82 berries today, and found only 1 with a viable egg on it, so perhaps the populations will be lower than they were last season — one can hope!

Final Keeping Quality Forecast: Neither Bangor nor Caribou picked up any of the additional 3 points that were possible for June, so, that means that out of a total of 16 points available in the model, Bangor finished with 8, and Caribou finished with 9.  A score of 8 gives a forecast result of “Good” (for Bangor) and a score of 9 gives a result for Caribou of “Good to Excellent.” A score of “Good” means: Can ‘probably’ reduce your fungicide applications (definitely reduce if you used a Late Water flood) and a score of “Good to Excellent” means, according to the model: Can ‘probably’ reduce or eliminate your fungicide applications (definitely eliminate if you used a Late Water flood).

July 14th: Blackheaded fireworm is well on its way again in central and southern Maine, with the 2nd generation of larvae now feeding on upright tips and webbing the upper leaves of the tips ‘shut’ so they can enjoy the protection that affords [This is how it looks].  The larvae should be hatching from their eggs in downeast Maine this week, especially with the hot weather we are now having.  They will develop/grow quickly with heat like this.  Probably one week as a larva is all the time they will need, before pupating.  And I would not be surprised if there is a 3rd generation of them this season.  There is some good news to share, however, which is simply this:  Other than fireworm, I have not seen any other pest issues recently.

June 26th: This has been an active season for our cranberry pests, in general.  Things are settling down a little now, however, in part because we are in between generations for Blackheaded fireworm currently, meaning the insect is in the moth stage (mating and laying eggs).  By mid-July I would expect to see larvae again, and be careful, as the numbers could be quite high based on how many sites had sizable levels of first-generation larvae.  Cranberry tipworm levels are slowly climbing, I think, but they are considerably lower than historically they would be by this point in the season.  I don’t think the tipworm injury levels are really hurting anyone significantly at this point.  July will be the real test.  Last season, tipworm numbers rose dramatically during the month of July.  Cranberry weevil has been a nuisance for many of you this season, but, I think most of you have also handled them well such that as we head into bloom, I don’t think we will see any outbreak numbers (or threshold numbers) anywhere.  The bloom period is when the weevils do the most harm, clipping off flower pods after laying an egg inside them.  So, unless you are seeing flower pods littering the floor of your bed(s), then you probably did not suffer much of a loss from the weevil.

Update to the Keeping Quality Forecast:  The final forecast will be made once June’s data is complete, but the preliminary forecast has already improved by one point (for both of the locations used in the model–Bangor and Caribou) as a result of May conditions.  Thus, currently, the forecast with Caribou conditions has moved into the “Very Good To Excellent” category, and Bangor is now sitting at the highest point total (8 points) inside the “Good” category.  Both of those labels mean, according to the model, that you can probably reduce or eliminate your fungicide applications. The difference between them has to do with whether or not you used a Late Water flood this season or not, which gives you even better protection against fruit rot.

June 5thBlackheaded fireworm and also cranberry weevil are now in Columbia Falls.  Fireworm was way past threshold at two of the Columbia Falls sites I visited yesterday (counts ranging from 10 to 20 per 25 sweeps).  The fact that fireworm is a very patchy insect was illustrated for me in impressive fashion.  Half of the beds I swept had no fireworm at ALL, but in the other beds (a short distance away), fireworm numbers were at dangerous levels.  This was true for each of the sites where I found them.  So, if you have more than one bed, be sure to sweep as many of them as you can, before assuming you are free of fireworm.  I found cranberry weevil at all of the Columbia Falls sites I visited yesterday, and they were way above threshold at one of the sites.  Tipworm should be starting in Washington County now, also, given the stage of the plants (new tips are opening up and lengthening).  I collected some samples and will be looking for eggs ASAP with my dissecting scope.

June 4th:  It looks as though the May 31st prediction about caterpillars beginning to be found in Washington County was correct.  Yesterday I found Blackheaded fireworm larvae and false armyworm larvae there, and will be returning tomorrow for more sites (in the Columbia Falls area), since fireworm has been rather prevalent there in recent years.  The fireworm larvae yesterday were nearing maturity already (their development has been VERY fast following our hot weather).  The fireworm I captured in central Maine on May 20th are now in the moth stage, so I do not think they will be in the larval stage for more than a few more days in Washington County.  Remember, this is only the first generation (of two to three total).  If one allows the first generation to escape, the second generation can be extremely damaging to the vines, skeletonizing the leaves in large areas of a bed, resulting in a brown,  ‘burned’ appearance to the affected areas. 

So please be vigilant and sweep, and treat your sweepnet contents like a crime scene (in order to spot the fireworm larvae)!  What do I mean by that?  Please keep reading.  The picture below is the contents of my net from yesterday, after doing 50 sweeps.  You should have about the same amount of leaves and litter as this, after 50 sweeps.  If you have more than this, you are probably sweeping too low into the canopy…..if you have less than this, you are probably sweeping too near the tips of the plants.  Now, the important point I wish to make about this picture, however, is that for the first 30 seconds or so, when looking at it, I only spotted TWO caterpillars (one false armyworm and one fireworm larva), and, I was looking VERY carefully.  If I were an impatient person, I might have dumped out the contents at that point and concluded that the location was barely at the threshold for fireworm, which is only 1 to 2 per 25 sweeps.  “I guess that’s still threshold,” I thought to myself, but was thinking I should probably sweep again.  However, I kept looking in my tray, and it turns out there were 14 MORE fireworm larvae in my tray and it took me at least five minutes to discover them all!!  Why are they so easy to miss?  The answer is that, besides blending in so well with the leaves, the larvae rarely crawl into any empty spots (of the tray or whatever container you might be using) where you can see them easily.  In other words, they like to stay clinging to the leaves and debris, and when they *do* begin to crawl, they purposely crawl from leaf to leaf (and sometimes going underneath them), rather than crawling out into the open.  It is a protective instinct, no doubt.  Contrast this with the bright green color of false armyworms, and the fact that they just start crawling anywhere and everywhere, and it is easy to understand the difference between them and the reason why you need to be extremely patient and thorough if you expect to discover fireworm larvae.  I had already removed all of the larvae before taking this picture, but, it would probably look about the same either way, because–as I’ve said–they hide so easily.

2013 Pest Reports - Scouting Tray (060313)

Sweepnet contents after taking 50 sweeps (June 3rd, 2013) (Washington County). Blackheaded Fireworm larvae are skilled at clinging to the leaf litter and remaining out of sight. One must be patient and extremely thorough in order not to miss them.

May 31st:  There are no major pest situations of concern to report on (no serious outbreaks, in other words–which is always good news).   Things have been moving slowly since the last report, with the early spring caterpillars not that far along currently (so they are very vulnerable to any of our control products should you happen to encounter a threshold level of them), even in western Maine which is usually well ahead of the rest of us.  The cooler temperatures earlier this week, and rain, kept things at bay, I’m sure.  I did pick up a few cranberry weevils yesterday in western Maine, so, they are only just now beginning to move from the woodlands where they spent the winter, to cranberry beds, and unless you have a history of having them, I would not be overly concerned.  Everyone should sweep their beds, though, during this weekend, with the heat we are now experiencing.  Caterpillars may likely be starting now in Washington County (as a result of this heat), and I will be heading there this coming week to find out.  Fireworm is the one to really be watching for.  Tipworm flies are probably not far off, but I have not seen any as yet, nor have I seen any new shoots still, which really draws the flies in.  Stevens buds even in western Maine were only in the cabbagehead stage yesterday.

May 20th (Spring Caterpillars): Quite a variety of our typical early-season caterpillar pests were coming out in force in central Maine as of May 16th.  Blackheaded fireworm, false armyworm, blossomworm, and gypsy moth caterpillars all made an appearance for me. One spanworm was in the mix as well.  The gypsy moth and blossomworm larvae were not abundant (below threshold by themselves).  However, the fireworm and cutworms (false armyworms) were way above threshold.  Now, downeast Maine (Washington County) is probably a good week or more behind compared to central Maine and western Maine, and as of Friday, May 17th, there were no caterpillars to be found whatsoever, from sites I visited in the Columbia Falls and Jonesboro areas.  I knew even before checking that I would most likely not find anything, given how dormant the vines still looked, and in fact I didn’t find anything — not a single caterpillar of any kind.  No signs of tipworm yet, either, which also does not surprise me because there are no new shoots coming up from the runners yet, even in central Maine.

Degree Days: Degree days are certainly not tearing up the charts!  The accumulations are low, although this seems to be a much more ‘normal’ spring than what we’ve had in recent years.  I also am feeling a lack of trust in the ‘target’ number for when blackheaded fireworm larvae are supposed to start hatching (target number is 252 degree days), because of the fact that they have begun hatching in central Maine already, and yet, the degree days for Bangor have not even reached 100 yet.  So clearly the model is not full-proof.  The target number for cranberry tipworm eggs is 225 degree days, but, I suspect new shoots will be coming from the runners before we reach that number, and I trust the crop stage more than the degree days for predicting tipworm egg-laying.  But perhaps they will line up better than I am thinking they will.  Only time will tell.

For a list of ‘growing’ degree day (GDD) accumulations from some representative areas around the state, visit: http://umaine.edu/cranberries/grower-services/degree-days/

Issued May 13th — Preliminary Keeping Quality Forecast for Maine Cranberries: With 10 possible points to be awarded to this point in the season, Bangor got 7 of them and Caribou got 8.  Both scores ‘already’ translate to a rating of ‘GOOD’ which means, according to the model: Can ‘probably’ reduce your fungicide applications (definitely reduce if you used a Late Water flood).  Each location is likely—by the end of June when the model is completed—to earn at least 1 more point out of the possible six that are remaining, so a ‘final’ score in the 9 to 11 range is quite likely, especially for areas most similar to Caribou’s conditions. A score in the range of 9 to 11 translates to a rating of ‘VERY GOOD TO EXCELLENT’ which means, according to the model: Can ‘probably’ reduce or eliminate your fungicide applications (definitely eliminate if you used a Late Water flood).


2012 Reports:

August 15th:  Cranberry Fruitworm has been rather high in populations this year, but, it may not be as bad as it looks on the surface (at least not for those of you who have sprayed at least once if not TWICE for it this year).  I collected a large sample of random berries [picked blind] from a bed last Friday that looked to have possibly what one would describe as “a lot” of fruitworm, but the % loss from my sample was actually only 3%, and a loss of 3% or less is considered by the industry to be acceptable (And…only ONE of the 127 berries I looked at had an actual larva present inside).  So, I’m hoping that although some of you may be seeing a lot more fruitworm-infested (i.e. prematurely red) berries than you’ve seen in recent years, the actual percentage loss may not be much more than 3% (hopefully!!), and this is assuming you have treated a few times for the fruitworm.  We’ve just had some VERY low population years up until now, I believe, so we are not used to this.  It is safe to point our collective fingers at the mild winter we had, as the most likely and most immediate cause of the higher numbers this season.

How bad would the fruitworm have been if I hadn’t sprayed for it?  This is a question we all often ask ourselves, and which is very hard to answer, but this year, I feel that I can speak to that question somewhat with some good evidence to back up my answer, at least for one location where I sampled a lot of berries recently, after the egg-laying period was apparently finished.  Often times you can find the empty egg shell from a larva that has hatched out, which provides a bit of a measure of what the ‘starting’ population was like, independent of the fate of the larva after the fact.  Sometimes a larva will consume its own egg shell, however, for extra nourishment, so it is still not an absolute measure of the initial population, but at least one can know what the ‘minimum’ starting population must have been….  And in the case I examined closely this season, the ‘starting’ level of fruitworm was at least 11% of the berries.  And yet it resulted in only a 3% loss of fruit, from what appears, presumably, to be the result of the pesticide(s) used (Rimon® and Carbaryl® in this case; I don’t believe natural enemies were involved, because there was no visible tunneling or damage at all on the fruitworm berries that were ‘not’ lost or damaged (i.e. the other 8% — nothing except an empty egg shell), and normally they would begin to tunnel within only a few minutes of hatching, which suggests to me that just a few bites of ‘something’ was responsible for their demise rather than a predator or natural enemy).  Now, granted, if you have a small planting, and/or a low yield to begin with, what is 11% at one site for a starting percentage of berries might equal 25% of your crop or your neighbor’s crop!  So, it varies, of course, from site to site, as far as how much of your crop, percentage-wise, is in danger from this pest!  As point of reference, this year’s figure of 11% comes from a site with multiple beds, and with an average to above-average crop load.

Cranberry Fruitworm egg shell remains (after the larva hatched):

A cranberry fruitworm empty egg left behind after the larva hatched out. A cranberry fruitworm empty egg left behind after the larva hatched out. A less-zoomed view of a cranberry fruitworm empty egg left behind after the larva hatched out.

a male Spotted-wing Drosophila fly - captured on August 9th 2012 (Hancock County)

A male Spotted-wing Drosophila fly – captured on August 9th, 2012 (Sedgwick, ME)

Spotted-wing Drosophila (SWD Fruit Fly) Update: We have had our first SWD fly capture in a trap associated with cranberries (on the edge of a cranberry bed in Sedgwick), however….it was only ONE fly, and is in an area with a lot of low-bush blueberries so I am still not very worried about an attack on cranberries from this new fruit pest.  (It probably came from a blueberry or wild blackberry in the area.) It is important that we keep monitoring, however, to be able to say that ‘yes, they are present in the same areas as our cranberries, but did not infest any of the cranberry fruits’, especially throughout the periods after the blueberries and raspberries are all gone when the flies could presumably be more desperate for additional sources of fruit.  The fly captured is a male (only the males have the spots). Several other fruit flies were also captured, some of which might have been SWD females, but the females are harder to identify, of course, and I could not see any ovipositors on any of the others to be able to look for the presence of the double row of saw-like teeth that the SWD females possess.  None of the others looked to have markedly red eyes, either (another diagnostic trait).

a trap for the Spotted Wing Drosophila fruit fly pestAdditional Information: At least 6 different Maine cranberry sites are being monitored (4 that I am responsible for), representing 148 acres, located in Turner, Dresden, Sedgwick, Deblois, Columbia Falls and Township 19.

The August edition of the UMass Cranberry Station Newsletter addresses SWD as well. They are not overly concerned about it actually infesting cranberry fruits, either, but are keeping careful watch.


July 24th:   I expect most growers have sprayed once by now for Cranberry Fruitworm.  That’s GOOD, because I am predicting–and worried about–high moth populations this season due to the mild winter we had and the fact that so many other moth species have been high in population this year as well for the very same reason.  So be sure to review the ‘Control’ section of the fruitworm page.  If you have gotten by with only one spray for your fruitworm control in recent years, you should be prepared for two sprays or more this year I am betting, spread out 10 to 11 days apart.   The 2nd-generation of Blackheaded Fireworm is taking place now, with larvae in the tips of uprights and turning them a copper brown.  Fortunately, I have only seen these 2nd-generation larvae at one location thus far this season, however (in central Maine) — a site that has been hit hard by this pest for several years in a row now and which had a very high first-generation of fireworm larvae this year.  Finally, you may be wondering what the latest is on the new Spotted-wing Drosophila fruit fly (from Asia) situation.  Again, we do not expect this fly to develop a liking for cranberry (we believe the skins are too hard for them to penetrate), but I will be setting out some traps at some cranberry sites next week.  As far as other fruit crops being monitored, you can find an update of towns where flies have been trapped this season (associated with raspberries, strawberries and highbush blueberries so far) at this page: http://umaine.edu/home-and-garden-ipm/2012/07/16/spotted-wing-drosophila/

July 10th (three topics of note):

  • Tipworm populations rising
  • Cranberry weevil here and there
  • Final Keeping Quality Forecast

Tipworm is on the Rise! Tipworm is hogging the bulk of my pest news for this report, as it appears to be rising in its populations right now, and at least for a few sites I am aware of in Washington County, sprays of Rimon have only slowed their rise down a tad, but have not hammered them hard the way we would have hoped. I am wondering if all the rain weakened its efficacy some (i.e. diluted it too much) during the hours and/or days following the applications. In the very same sample of tips, I am finding that some tips have dead tipworm larvae in them, while other tips have healthy-looking tipworm larvae present. I’m not sure if it’s an issue of spray coverage (the Rimon must be eaten, remember, so it must come into contact with the tip), or if too many rainy periods diluted it some, or what? I did take some pictures of a dead tipworm, though, six days after a Rimon spray was used, so I feel safe and confident in attributing the ‘COD’ to the Rimon. I have seen tipworm ‘remains’ like this before, and always following sprays of Rimon.  Rimon interferes with the normal formation of an insect’s cuticle following molting, causing immobility and excess water loss resulting in death. The tipworm cadaver shown here is definitely ‘dried out’ in appearance, so the ‘autopsy’ results are consistent with death by Rimon.

picture of a dead cranberry tipworm larva on a cranberry leaf

A dead cranberry tipworm larva, presumably killed by Rimon (novaluron) — July 9th, 2012

Cranberry weevil has also been over threshold at a few locations, with bloom in full swing. Actara® was used at the site with the heaviest infestation, and it solved the problem completely and immediately.  Just remember to watch out for your bees, depending on what material you use. Avaunt® is also reportedly very effective against weevils, and is much safer to pollinators.

July 9th — Final Keeping Quality Forecast: With 16 possible points to be awarded, Bangor finished with 7 points in the model, and Caribou finished with 6 points.  [Bangor and Caribou are two of only four locations in Maine that the NWS provides sky-cover data for, which is needed in the model, and the other two locations are even further from cranberry beds or too dissimilar to the conditions of most of our cranberry beds.]  Massachusetts finished with only 2 points (rating of “very poor” keeping quality) this season!

Bangor’s score translates to a rating of ‘GOOD’ which means, according to the model: Can ‘probably’ reduce your fungicide applications (definitely reduce if you used a Late Water flood).

Caribou’s score translates to a rating of ‘FAIR to GOOD’ which means, according to the model: 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.)

June 24th: I am happy to report that I have seen very little ‘outbreak’ pest activity anywhere recently, and Cranberry Tipworm has been in such low numbers at all but one site so far (of the 15 sites I have visited), that it’s doubtful that it’s even of economic concern at those particular ‘low-tipworm’ sites (levels of only 10 – 15% tip infestation at most locations).  It sure is nice to see such low tipworm numbers at so many locations!  The one exception–a site in Washington County–had an infestation level of 75% on June 15th, with all the life stages represented, and the grower and I even found that there were some Yellow Loosestrife ‘weeds’ on the edge of the cranberry bed with galls on them which had tipworm larvae and pupae inside. I was unaware of any additional host for tipworm other than blueberry, but apparently we can add yellow loosestrife to the list (at least when it occurs together with cranberry) — just one more reason to be aggressive at controlling this stubborn weed, which also serves as a preferential starting host for dodder seedlings.

Umbrella Bloom and Pollination: I am seeing a fair amount of umbrella bloom this season. I dare say you can find some at every location. In reviewing some of the ‘suspected’ causes of umbrella bloom, I am wondering if the theory about lack of chilling requirement is correct, given the very mild winter we had!  The lack of chilling idea seems far more likely than does frost damage, or even tipworm injury, since some of the sites with umbrella bloom did not have any frost events, and they also did not have very high tipworm levels last season OR so far this season, either. Regarding pollination, I am a little concerned about the lower numbers of native bumblebees this season, and how that might affect the overall pollination. I visited four sites this past Friday and saw very few bumblebees–perhaps two the entire day–but at least those growers using honey bees would be pleased as I saw a LOT of honey bees on the beds.  I am tagging flowering uprights again this year (3 sites so far), to try to get a measure of pollination and resulting fruit set.

Good Year for Weevils! I have found more Cranberry Weevil this year than in years past — usually in low numbers this season, but I’m finding at least a few quite regularly and at sites where I’ve not found them before. Our Extension Insect Diagnostician reports seeing more weevils than ever this year out of all the insects brought to him for identification, and he feels one explanation for the high weevil numbers this year may be because of the mild winter. As further evidence of a “good year for weevils,” a type of weevil called a Broad-nosed Weevil has captured my attention this season, because of the many places it keeps turning up.  I first began to notice them feeding on the tips of my rose stems at home (see my photo below).  Then I started seeing them on some highbush blueberries that I just planted. Then…I found one on a cranberry bed last week as well. They belong to a subfamily of weevils called Entiminae, or commonly, Broad-nosed weevils, of which there are many species.  The one I keep finding probably belongs to the Otiorrhynchus genus, which includes the black vine weevil (O. sulcatus) and the strawberry root weevil (O. ovatus), both of which are pests–both as larvae and adults–on cranberries, strawberries, and other crops (and various garden plants, too). The larvae of these kinds of weevils feed on the roots, and interestingly, the adults are flightless (their wing coverings, i.e. elytra, are fused together, which you can also tell from my photo). I would not be overly concerned if you pick up even as many as 5 or 6 of these guys per 25 sweeps, since they do not damage the blossoms the way that the cranberry weevils do (they do not lay their eggs inside the flower pods, in other words), and the threshold for cranberry weevil, for comparison–a much more serious pest–is 4.5 in 25 sweeps.

A Broad-nosed Weevil on a rose leaf (May 30th, 2012) (Etna, Maine)

Preliminary Keeping Quality Forecast (using Bangor and Caribou data; There are only 4 locations in Maine that give sunshine / cloud cover data, which is needed for the forecasting model)

[Out of a total of 16 points, with 3 points still possible to be awarded]: For Bangor currently: Forecast is GOOD (7 points achieved so far); For Caribou currently: Forecast is FAIR TO GOOD (6 points achieved so far); Massachusetts issued their Final Keeping Quality Forecast: VERY POOR (only 2 points were achieved)

June 11th: Cranberry Tipworm finally showed up during the past week, but in very low numbers each place I found it (and zero eggs found, which is very surprising).  One site had just a 15% infestation represented by a few larvae and a few cocoons, another only a 10% infestation, and yet another one with historically high tipworm had ZERO percentage.  The site with only 10% had been treated earlier with Lorsban (for caterpillar pests), but the other two sites were not treated prior to my visits. The 0% site was in Columbia Falls.

In the absence of sprays, I would expect the tipworm numbers to certainly get higher as we progress through the season, but it looks like the cool and wet conditions we had in May and early June was really ‘uncooperative’ for the tipworm. Two of those three sites used Rimon last season, which may also have a lot to do with the low tipworm counts.  It will be interesting to see what tipworm does (or does NOT do) through the remainder of the growing season. What about other pests?  There has been very little ‘other’ insect pest activity to report on, though there have not been all that many days dry enough for sweeping with a net!  But,  I checked two sites on Friday in the south-central region of the state, and although I found a Blackheaded Fireworm larva at each site, the average per set of 25 sweeps was only 1 and 0.5 for the two sites, one of which is organic and has had higher averages in the past few years.  So, even though an average of “1″ might be considered “at threshold,” especially for an organic grower, I was encouraged to see that it looks like the fireworm population is lower there than it used to be in years past — probably a combination of the use of the Late Water practice, and this year’s weather.  Some bloom was starting at one of the locations, too, and I know bloom is ‘close’ for most everyone else as well.

May 30th (brief update): Looking at where we are with respect to growing degree days is worth doing, in the context of yesterday’s (May 29th) report. It means that my timing for my western Maine visit coincided with not only the start of new cranberry shoots, but it also coincided with the target number for when tipworm eggs are supposed to begin (strictly speaking, eggs should have been present on May 24th but of course, nature is never that predictable).

May 29th, 2012: I was in western Maine on Friday (May 25th), and new shoots were present, especially around the bed edges (some of them were over an inch high), but, to my delight, tipworm was nowhere to be found and nothing had been sprayed yet for insects this season at that location. I would have expected the tipworm to be depositing eggs on the new tips, heavily, but I couldn’t find even ONE (egg or larva), out of a sample of 60 tips (total) taken from two different beds. I’m not sure how to interpret the lack of tipworm. As a detective, all I can say is that I need more data, and so I will keep visiting other sites. In general, the first generation of tipworm (via the form of eggs on the new tips) coincides with the growth of brand new shoots from the runners. I am hoping the March heat we had, followed by a very long period of cool weather, has thrown the tipworm cycle out of whack, which may result in low populations this year, or at least, it may take the tipworm a good chunk of the growing season before it is able to reach high numbers like we have grown accustomed to over the years. And with some of the new tools we now have in the shed, I have to leave open the possibility that tipworm simply WON’T reach high numbers (at least not for everybody), even by late in the season, depending on your own situation and the ‘tools’ you might be employing.

Spring caterpillar numbers were VERY low at the site I visited Friday, and False Armyworm is the only ‘type’ we could find. Having said that, keep watching for Gypsy Moth caterpillars, since the Forest Service has confirmed for me that it appears this year looks like it might be the start of an outbreak year for them, but they do not know how big the outbreak will be. The egg mass counts they did in the fall were greater than usual, but still what they consider to be low, they told me. So, just stay on the lookout as we move into June and the caterpillars get bigger and bigger.

May 22nd, 2012: The early-season caterpillar pests are now emerged and active on beds for downeast locations.  These include the False Armyworm, Blackheaded Fireworm, and Gypsy Moth caterpillars.  They are all at a good size (in other words, ‘small’) for being vulnerable to any of the labeled products you might choose to use on them.  No sign of tipworm eggs or larvae yet, though, as there are no new shoots growing up off the runners yet….but….that time must be very close at hand; perhaps one more week at most.  As far as the early caterpillars are concerned, the downeast locations are nearly a whole month later than when they first started showing up in Massachusetts — just as a point of comparison. Have not found many spanworms of any kind anywhere as yet.  Massachusetts has seen high numbers of Winter Moth [a type of invasive spanworm -- one in every ten MA bogs has had it). [June Update: Winter Moth was found in Maine this year, too (Town of Harpswell). The Bangor Daily reported on it on June 5th: Bangor Daily Story]

May 15th, 2012: Was in western Maine yesterday and happily saw VERY little pest activity — only a few small false armyworms and one gypsy moth caterpillar with nearly a couple hundred sweeps all together! Plants were only in cabbage-head stage, so no tipworm concerns as yet, either, which means the rest of us, i.e. the ‘colder’ parts of the state, must still have plenty of ‘tipworm-preparation’ time.  Remember, the tipworm cannot survive without any tender new shoots upon which to feed.

picture of two different Stevens cranberry uprights, showing the bud stage for each

Stevens buds on May 7th, 2012 (central Maine) — The False Armyworm caterpillars feed on these new buds.

May 7th, 2012: Visited a great ‘indicator’ location today (Stevens bed) in the greater Bangor region, and found plenty of freshly-hatched false armyworm caterpillars (average of probably 10 to 15 per 25 sweeps). One oddball looper was the only other potential cranberry pest I captured. This is a site that is notorious for heavy fireworm populations, so it will be interesting to see when the fireworm larvae begin there. Usually by now they would be present at that location, but we are way behind in degree days compared to recent years for a calendar date of May 7th, so judging by degree days alone, it makes perfect sense that the fireworm have not begun yet.  The plants seem rather far behind to me as well, which stands to reason given the cool temperatures we experienced for most of April. Certainly no new shoots to be seen coming off the runners, and most of the buds were not even very swollen yet, so it’s way too early for tipworm as well, at least for this area.  I’ll try to get to Turner next, to see what is happening there, since they are quite a bit ahead of the rest of us, for degree 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 Office || 491 College Avenue || Orono, ME 04473-1295 || Tel: 207.581.2967 [email: charles.armstrong@maine.edu]

 


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