August 5th Update: I’ve looked closely at the cranberry fruitworm level at two very different sorts of cranberry sites, and the fruitworm pressure or level is remarkably similar at the two sites, coming in at 14% and 16% of berries with at least one cranberry fruitworm egg deposited on them. One of the sites has had no pesticides used for a few seasons now, which might explain the fact that I found a level of parasitism of the fruitworm eggs measuring an impressive 50%, so HALF of the eggs were parasitized by a tiny, beneficial wasp. Given that each surviving cranberry fruitworm larva can eat as many as five berries through the course of its development, if you begin with 16% of your berries having one fruitworm ‘on board,’ then you are potentially facing a hefty loss from fruitworm damage in the absence of any control efforts or very much help from predators or parasites.
So I think the take-home message is to be very vigilant with your fruitworm situation this season. The mild winter would have aided greatly in the survivorship of the overwintering pupae inside their hibernacula ‘capsules’ on the floor of the beds. Theoretically, a starting ‘egg level’ of 16% of berries infested, could translate to a loss of 16 x 4 or 16 x 5 (if each larva eats 4 to 5 berries), for a loss of 64-80% of one’s berries! But control efforts, coupled with the elements (weather, parasitism, predation), would keep losses closer to 50% in a worst-case scenario. I’ve never heard of a grower losing more than 50% of the crop to fruitworm. But, one thing seems clear — this is a high-pressure fruitworm year!
July 22nd Update: The second generation of Blackheaded fireworm larvae has now come and gone. I wasn’t sure for awhile, because it has been controlled so well at the sites I have been to. However, the moths I had captured from the first generation mated and laid their eggs, and the eggs hatched (and before I could get any photos, sadly). Today, however, I had time to capture this photo of one of the leaves that the moths deposited their eggs on. It shows 11 empty eggshells from which fireworm larvae emerged, as well as the shriveled remains of one of the larvae (in the upper left portion of the photo). By the time the eggs hatched, the small upright in the container I had–for the moths to lay their eggs on–had apparently dried out to the point where it couldn’t sustain any of the larvae, nutritionally or otherwise, leaving behind a graveyard of shriveled-up fireworm larvae by the time I noticed. The only ‘current’ pests I am seeing in the beds now is the occasional Blunt-nosed leafhopper, and a few Cranberry weevils. With regards to weevil, the vast majority of sites have been below the threshold of 4.5 per 25 sweeps. Just one bed had a count above the threshold, at 5 per 25 sweeps, and enough of the bloom has already gone ‘out’ on that particular bed (roughly 75% out-of-bloom) that I’m not overly concerned about that situation.
June 13th Update: Blackheaded fireworm is certainly present now, but I’ve only found it at two sites so far, although at extremely high numbers at the most recent location (late last week in eastern Maine), where it was 30 or more times above the threshold! I’ve been seeing such unique pest situations at each site I visit this season, that I think the take-home message is that you need to check your own acres rather than paying much attention to any news from what is occurring in other areas of the state. Another site in eastern Maine had high numbers of the Blunt-nosed leafhopper, for example, but not a single fireworm larva (after taking about 200 sweeps).
No other pest ‘stood out’ to me this week; low numbers of everything else, in other words, including tipworm, surprisingly enough. I noticed only a single upright last week from two sites in eastern Maine that showed the classic ‘cupping’ symptom from tipworm. My guess is that the lack of springtime heat and the cold weather we’ve had lately has prevented the tipworm from building up its populations. It will be interesting to see what happens with tipworm in July.
June 6th Update: Have not been finding a great many pests so far this season, I am pleased to report. Early-season caterpillar numbers have been a little over the threshold, at times, but mostly so far the populations of false armyworms, blossomworms, fireworm, and the rest, have been low, even at an organic site I checked last week. I’ll be visiting eastern Maine sometime this week, to see if the situation is any different in that part of the state. No signs of tipworm as yet, but generally eastern Maine is where the tipworm is the heaviest so I expect I might find some while I am there this week.
August 4th Update: Blunt-nosed leafhoppers are still present, and they typically survive right up until the first hard frost. I was at an organic site in western Maine on Friday, and found a high number of them (100 or more after 25 sweeps). There is only one generation of these guys per season, and the adults do not feed very much on the leaves. It is simply their vectoring of the False Blossom Disease that is of concern, as described in the June 26th pest report. I also caught my first Red-headed flea beetle of the season on Friday, in central/south-central Maine. We could be in for another year of high counts of this pest. Cranberry fruitworm: Out of 100 cranberries collected at random from an organic site in western Maine on Friday, the only sign of fruitworm I could find was a single, empty egg, with no signs of damage to the berry it was on, and no larva to be found, either. I was pleasantly surprised not to find more signs of fruitworm than that.
July 29th Update: Be watching for these pests, if you haven’t seen them already recently: brown spanworm larvae, 2nd-generation blackheaded fireworm larvae, and cranberry weevils . It is also cranberry fruitworm time, which probably goes without saying.
Brown spanworm is a species of inchworm/spanworm that I found in very high numbers at an organic site last week, and I saw a moderate level of them (about double the threshold of 4.5) at one other site this past Friday. It usually occurs in patches on a bed, rather than being distributed evenly, so you will want to check additional sections of a bed in order to determine the extent of an infestation. I wasn’t sure what kind of spanworm they were until they grew larger in size. I don’t recall ever finding an outbreak of this spanworm anywhere in Maine before [you won’t even find one as yet on my “spanworms” page on the website], but in Massachusetts, it is common to see high numbers of them on some of the bogs nearly every year. PEI has been having problems with it as well (this year and last year). In high numbers, they can inflict a lot of damage to the leaves, and will even feed on blossom buds and berries but generally to a lesser extent than the leaves. The Cranberry Insects of the Northeast book gives a great description of this pest (scroll to page 34 of the pdf; pages 28 and 29 in the book itself). The whitish stripe along each side of the body is what particularly signaled to me which type of spanworm it was, but as the larvae get older, the stripes get less pronounced. If you are finding high numbers of caterpillars that are ‘inching’ or ‘looping’ along (like the one shown in the two photos below), try to ascertain if they are brown spanworms. Send me a photo if you like.
A Note about Cranberry Fruitworm Management: Massachusetts growers have been using Altacor for managing their fruitworm, at a rate of 4.5 oz/A which enables them to use a total of two applications since the maximum amount allowed per season is 9 oz/A. Delegate is being used later in the fruitworm season as a “clean up” spray, if needed.
Brief July 9th Update: Not seeing much for insect pests out there now, with one exception — the Blunt-nosed leafhopper; this pest has been building in its numbers (number of adults), in accordance with its natural life cycle. The number of adults should be at its peak now, or at least close to its peak. The adults will mate and lay eggs on the cranberry stems; these eggs will then overwinter. Pages 61 to 63 of A.L. Averill & M.M. Sylvia’s book, Cranberry Insects of the Northeast covers this pest in detail. You can view the book online at this address [page 67 of the pdf].
Above: Two photos showing several blunt-nosed leafhoppers picked up after sweeping in a cranberry bed. July 3rd; Washington County. All photos by C. Armstrong.
Final Keeping Quality Forecast: Bangor finished with 7 points, and Caribou achieved 8 points (out of 16). Neither location picked up any of the 3 additional points that were possible based on June weather, so this means the final forecast is the same as the preliminary one was a month ago: “GOOD” – for both locations. A forecast of ‘good’ means that you can ‘probably’ get by with just one or two fungicide applications (definitely spray no more than twice if you used a Late Water flood).
June 26th: It seems the 1st-generation larvae of Blackheaded fireworm are mostly now behind us (most should have pupated by now, and one bed I visited this week in the middle of the state was loaded with the adult moths and no larvae, signaling that the first generation is pretty much complete). If you are not seeing the blackheaded fireworm moths in your sweep nets currently, then you’ve either managed the larvae successfully (and deserving of congratulations), or, you didn’t have a problem with them to begin with. If you had an outbreak of the larvae, but were unable to control them, then you should be catching the tiny, dark grey moths in your net when you sweep. These are the moths that will be mating now and laying eggs, singly, on the undersides of the cranberry leaves. Those egss will hatch out and comprise the 2nd generation of larvae, which will probably begin in late July–perhaps a bit sooner for some–and will continue throughout much of August. Be on your guard!
Blunt-nosed leafhoppers are now showing up a fair amount, including in Washington County. This is a pest that is less familiar to many of us, including myself, and is darker in appearance than I was remembering, partly because when you have good light on them, and are looking at them under high magnification, they don’t look nearly so dark and sometimes not dark at all! You’ll be able to tell what I mean from looking at these photos I just took of a specimen I captured yesterday in coastal Washington County. Going from left to right, you can see how much the darkness is affected by the lighting in combination with the magnification.
Why should I care about the blunt-nosed leafhopper? Unfortunately, this insect is a vector of a cranberry disease–a phytoplasma–called “False Blossom.” It is only vectored and spread by this leafhopper, in fact. I’ve never seen any signs of this disease in Maine, fortunately, but, that doesn’t mean it isn’t present. The leafhopper is making a comeback in New Jersey and Massachusetts (and may be on the rise in Maine as well), so, we need to at ‘least’ remain cognizant of the potential risk this leafhopper poses to cranberries. Symptoms of False Blossom Disease: “The lobes of the calyx become enlarged at bloom, and petals are short and streaked with deep pink, red, or green. Flowers usually are sterile (do not produce berries). Branching is stimulated, resulting in a witches’ broom. Foliage on infected plants might redden prematurely and fall. Diseased vines grow few if any runners and tend to die out over time.” Source: Caruso, F.L. and Ramsdell, D.C. 1995. Compendium of Blueberry and Cranberry Diseases. St. Paul, MN: APS Press. You can find a few photos of the disease inside this journal publication from Rutgers, at this address: http://pemaruccicenter.rutgers.edu/assets/PDF/Lee-et-al-2014-with%20false-blossom-diseased-cranberry.pdf Also, please read page 399 of the New Jersey article (part of the discussion section)!
Cranberry tipworm is with us, of course, but, I’ve yet to see a really heavy infestation anywhere, which I’m encouraged about. There’s still a lot of growing season remaining, though, so I’m trying not to get too comfortable with my tipworm ‘feelings’ just yet.
Some Good Guys!! Picked up numerous of these beneficial predators last week in Washington County on a bed of Stevens. They are numphs of a type of assassin bug, in case you see some and wonder what they are. They almost resemble miniature preying mantids, with their large front legs that they use to grasp and secure their prey. So be nice to them, as they will prey upon small caterpillars (and larger caterpillars once they are adults). You can read more about the assassin bugs ‘group’ from this Univ. of Kentucky page, if you wish. In the 2nd photo below, you can see most of a blackheaded fireworm larva, also. The nymph in the photo is probably too small to successfully prey upon it, but, it might be able to overpower a newly-hatched fireworm larva, which is significantly smaller than the full-sized one shown in the photo.
Update (June 17th): Several of our key pests are present now, simultaneously, and will probably be with us for the duration of this month. June is probably when the greatest number of our insect pests occur at the same time, as far as their damaging stage is concerned. Tipworm is certainly trying to do its thing, though perhaps in smaller numbers thus far compared to many past years. I just looked at a sample of tips a few days ago from Washington County from a historically ‘heavy’ tipworm site, and the tipworm was mostly in the egg stage (20% of the sample had 1 to 2 eggs present; 20% isn’t wonderful, but, I’ve seen much worse than that at the start of many previous seasons). Only 8% of the sample had any tipworm larvae or pupae present, and 2 out of the 4 larvae that I did find, had been killed, possibly from a shot of Intrepid that went out about a week prior (Intrepid/methoxyfenozide is not touted for or normally associated with tipworm control because it’s a material that affects caterpillars primarily, causing premature molting…..but, there are also some fly larvae–including the common house fly–known to be affected in the same way by it.)
Blackheaded fireworm, false armyworm, blossomworm, and cranberry weevil are other pests I’m still seeing rather routinely. About the only pest that is proving to be at the threshold now, however, or well above the threshold, is the fireworm. Blossomworm seems to have settled down, unless that’s because they have ‘literally’ settled down (down into the canopy), and are only feeding at night, which is what the larger caterpillars in fact do! So I don’t want to be too hasty in saying not to worry anymore about blossomworm this year.
Visual Symptoms of Fireworm: Look for uprights where the uppermost leaves and/or entire uprights have been pulled together, like in these three photos here:
Following the application of Intrepid at the earlier-mentioned site, the number of fireworm larvae being caught was still well over the threshold (in the neighborhood of 5 per 25 sweeps). However, some of those larvae appeared to be sick, and I actually found one tip which had two deceased fireworm larvae present (pictured at right). Thus, by now, the population of fireworm there could easily be reduced by 50% or more of what I picked up previously, just from the good residual power of the Intrepid that was used against it some 7 or more days prior. It appears the Intrepid worked very well!
Preliminary Keeping Quality Forecast: Through the end of May, Bangor picked up 7 points out of a total of 13, and Caribou achieved 8 points out of 13. That gives an early forecast of “GOOD” for both locations with 3 more points possible by the end of June for each location. A forecast of ‘good’ means that you can ‘probably’ get by with just one or two fungicide applications (definitely spray no more than twice if you used a Late Water flood).
Update (June 5th): Cranberry tipworm is now present in Columbia Falls (eggs and 1st-instar larvae), as of June 3rd. The sample of 28 brand new tips that I collected had 4 with eggs, and 4 with a couple of larvae, which translates to an infestation of 28% of the tips. The tips with larvae were already starting to show the characteristic ‘cupping’ injury.
June 4th: Upon visiting 3 sites in coastal Washington County yesterday, it looks like the bulk of our caterpillar pests are just now starting to show up in that region, and not in ‘crazy-high’ numbers, at least for the time being. As we move through the weekend, however, it is always possible that populations could quickly rise and end up looking more like western Maine did a week ago. It is really hard to predict, at this point. Blackheaded fireworm larvae were present, at one of the sites that has had this pest in the past. Most of the larvae could not have been more than a few days old. Counts were rather high, though (roughly 15 per 25 sweeps; way past threshold), and they are likely to climb much higher than that if left to their own devices. Certainly, there were some false armyworms and blossomworms to be found, also, but, in much more manageable numbers compared to the sites I visited last week. Their lower numbers could be due to two things: 1) just a tad early still for downeast, and/or 2), the cold and rainy weather we had on Monday and Tuesday slowed things down, for sure. Temperatures were only in the 50s when I was catching things yesterday, so perhaps on a warmer day, with more time subsequent to the rainy weather we had, there might otherwise have been much higher counts than what I obtained — again, it is very hard to say for sure. Next week I will visit more Washington County sites, so we should have a better feel for the situation by the middle of next week. So stay tuned!
Saturday Update (5/30): After checking one more site yesterday (in central Maine), I am convinced that we are facing a banner year for caterpillar numbers. Just 25 sweeps yesterday resulted in about 20 false armyworms, 30 or more blossomworms, one gypsy moth larva, and one blackheaded fireworm. Since blossomworm and blackheaded fireworm both overwinter in the egg stage, all of the snow we had this winter is probably the reason for the extremely high numbers–the snow insulates well, so greatly boosts their survival chances. The deep snow cover probably aided the overwintering false armyworm moths as well. Footnote: False armyworms and blossomworms are both members of the cutworms group, so their numbers get added together, making yesterday’s total “cutworms” count a sobering 50, with a threshold of just 4-and-a-half.
May 28th: Year of the Blossomworm? Forget the Year of the Sheep, which is what 2015 is according to the Chinese zodiac. We might, instead, be facing the Year of the Cranberry Blossomworm, if western Maine is any indication. Be on the lookout for this caterpillar! I found it yesterday (consistently, too) in numbers over 20 times larger than I’ve ever seen this pest before! Counts in the one-hundred+ range, per 25 sweeps, and its standard threshold is just 4-and-a-half. Even doubling the threshold to 9, to account for low berry prices, pales in comparison to counts in the 100 to 200 range. Apparently this was a very good winter for at least the cranberry blossomworm, and perhaps some of the other caterpillar pests as well, which may have been knocked down a week earlier at this location from a spray that was applied targeting any caterpillar pests that were present at that time. The flood of blossomworms that is there now likely emerged/hatched a few days after that application, leaving them all alone in a sea of delicious new cranberry growth. So, the take-home message from what I found is this: at best, we might be facing a terrible season of very high cranberry blossomworm populations, and at worst, all of our veteran caterpillar pests may be more numerous than in years past. Hopefully it’s just a good year for the blossomworm, alone, and not all of its friends, too!
Description: Cranberry blossomworm larvae lack the bright green color that False Armyworm cutworms have, that we are more accustomed to seeing. I would describe the young larvae as a dingy green or tan/brown in color, with a darker, reddish posterior end (in the larva pictured above, this darker/redder end is the left-most end; its head–which is a tad out of focus–is on the right-hand side of the photo). These larvae do not get nearly as large as false armyworms, either. They max out at around 1/2″ long rather than 1.5″ or longer like their false armyworm relatives eventually grow to reach. They also have a white stripe (with no yellow bordering it) running the length of each side of their body.
Other pests?: I found very little of anything else yesterday; just a spattering of cranberry weevils, false armyworms, and a single larva each of gypsy moth and blackheaded fireworm after checking multiple beds. Everything except the blossomworms was well under threshold. The story of the day was definitely “Cranberry Blossomworm.” It was a VERY unusual discovery, as I’ve never before found that pest in numbers anywhere near that high. I’m not even certain it has ever been over the threshold before in Maine, without adding its numbers to the number of false armyworms found, which usually far surpasses the blossomworm larvae.
Tomorrow I’ll be visiting another site, somewhat centrally located, which may help tell us if this blossomworm explosion was just a fluke, or something that many growers will be confronted with this season.
September 10th: Be on the lookout for Red-headed flea beetles! I found high numbers of them at a site downeast yesterday (on the coast), and spotted some others at an additional site near Columbia Falls. I only saw a single occasional one last month, but now their numbers have apparently built up in some locations. There’s only one generation of them per season, and the adults out there now will be laying eggs just below the soil/sand surface. The adults are feeding on the undersides of the leaves, and it looks surprisingly similar to the feeding damage caused by blackheaded fireworm, which many sites also have leftover injury from this year’s fireworm populations (we did, in fact, get three succinct generations of the blackheaded fireworm this season). There are moths out there now that are the newest offspring from that 3rd generation of larvae we had. With temperatures cooler now, their eggs will overwinter rather than hatching into a 4th generation (three is plenty!!!). Action Threshold for flea beetles: There is no ‘firm’ or full-proof threshold for this pest, probably because the adults can be very patchy on a bed, but…if you are averaging sweepnet counts of 15 or more per 25 sweeps, they consider that (in Massachusetts) high enough to consider taking action against them. A high level of beetle feeding can impact the buds that are there now which the vines are counting on for next season’s growth. Since the beetles can be so patchy, be sure that you don’t just sweep one portion of a bed (make sure you have good representation of the entire bed). If you are still getting 15 or more beetles, across the entire acreage, I would certainly be concerned and trying to control them would be justified.
August 20th — Final Keeping Quality Forecast:
- For Bangor conditions: 7 points out of 16, which equals a forecast of GOOD (Can ‘probably’ reduce your fungicide applications and can definitely reduce them if you used a Late Water flood)
- For Caribou conditions: 9 points out of 16, which equals a forecast of VERY GOOD TO EXCELLENT (Can ‘probably’ reduce or eliminate your fungicide applications and can eliminate them entirely if you used a Late Water flood).
July 30th: Heavy fireworm and fruitworm! I am seeing high populations of blackheaded fireworm (2nd generation) and cranberry fruitworm now, with both of these pests mostly in the caterpillar stage. Cranberry tipworm is also very high at some sites, but, the fireworm is the pest I am most concerned about because of its tendency to increase in population each year once it becomes established somewhere, and because of its destructive potential. Tiny patches soon become big patches, which soon can become an entire bed.
Surprising Finds!! This past week, July 24th to be exact, I spotted–twice on the same day, in two separate towns in Washington County–a critter that truly lives up to its name: the Big cranberry spanworm! (more photos below) It looks more like a twig than most twigs do, but I happened to look right at it in each case, and could tell something wasn’t quite ‘right’ about these particular sticks or twigs because of the way they were attached to the uprights. But, if you weren’t looking with eagle eyes, you’d never see these guys because of their masterful camouflage. They also latch onto the stems so tightly that you wouldn’t likely sweep one of these guys up in your net, once they were this large. I looked around carefully for more of them, but, fortunately, only found the single one at each location. I say fortunately, because, at this size, they can be extremely destructive, chewing up whole flowers and upright tips in no time at all. It also goes through just one generation per year (lucky for us), overwinters as a pupa, and emerges as a moth around the very end of May. The female moth lays her eggs in a cluster containing as many as 432 eggs, which hatch around the middle of June. After seeing these two specimens, I have a new appreciation for just how destructive at least ‘some’ spanworm species can be! Note: You can read more about it on page 30 of the UMass Cranberry Insects of the Northeast book if you have a copy of that.
First 3 photos: Big Cranberry Spanworm, Eutrapela (=Abbotana) clemataria (J. E. Smith); 4th photo shows a twig that was found on the cranberry bed near the big cranberry spanworm, which is remarkably similar to it in size, color, and pattern! [Photos by C. Armstrong]
Some new Cranberry Tipworm photos (by C. Armstrong):
July 14th: One mystery solved; New one takes its place — The little critter causing the round holes in the leaves pictured here and in the previous report, is a kind of leafminer insect called Coptodisca negligens Braun. It is described on page 66 of the Cranberry Insects of the Northeast book, and, I’m happy to report that it only goes through one generation per year. I do not believe any work has been done with this pest in relation to its impact on yield, and for sure that is true at the time the book was published (1998). It seemed to be the older leaves that were colonized where I found it, though, and the older leaves do not do much photosynthesizing anyhow, so I don’t imagine there is a noticeable effect on yield, even if you had one or two leaves ‘victimized’ per flowering upright.
New mystery! I saw this caterpillar feeding away on a flower on Friday in Washington County. I’ll try to get it identified. It is certainly distinctive!
Boron Grant Well Underway! I’ve finished two rounds of flowering upright sampling at six Washington County sites. Each site is having one leaf tissue test (of flowering uprights, including the flowers) collected and analyzed every 7 to 9 days during the bloom period, for a total of three samples from each site (and, one site is having this done on two side-by-side beds, one with CalBor applied and one without, looking for any differences in boron levels and subsequent fruit set percentages). I’ll also take one more sample from each site in the fall. In addition, to see where in the uprights most of the boron is ‘found’ during the bloom period, I collected one sample of just flowers, another sample of just leaves, and a third sample of just stems, all from a bed where CalBor was applied 8 days before my sampling. It will be interesting to see where most of the boron shows up (hopefully in the flowers, where we want it, compared to the stems and leaves). I’m also doing my usual tagging of 20 to 30 uprights at each site, in order to have fruit set values to go along with the boron findings.
Bumblebees Out in Force! On Friday (July 11th), I was pleased to see native bumblebees out in force. Every few steps there was one! The previous week I only saw a single bumblebee (per bed) the entire time that I was doing my grant work and upright tagging, so I was a bit depressed and concerned about their populations. Now, they seem to be making up for their absence in a big way! Haven’t seen many honey bees, still. I think all of the rain we had may have washed so much of the pollen down that the honey bees haven’t been too impressed yet with what the cranberry blossoms are offering. Hopefully that is changing now. On July 9th, I was at a site where bees were scarce, and, I was seeing a lot of rosy pink-colored blossoms as shown in the 1st photo below. This is symptomatic of poor pollination, when you see flowers of this color with the petals still attached (it likely means the flower has been there for two to three weeks without being pollinated).
In the third picture directly above, you can also see that tipworm has damaged the upright, with the characteristic cupping at the tip of it. I have certainly seen evidence of tipworm-damaged uprights in the beds I’ve been on recently, but, I can’t say I found it to be excessive or alarming. I’ve not seen enough lately, in fact, to be concerned enough to take a sample. Once the grant work is finished, I will start to take a closer look and try to see what levels of cumulative damage it is causing.
June 24th: A few items of note to report! Blackheaded fireworm was the pest to try to beat during June. How well everyone did will be apparent when it is time for the second generation to show up, which is generally during August. I am seeing newly-hatched moths in my sweeps now — they are the lucky ones, you might say. These are the adults from the 1st generation of larvae that has just ended, and are the ones that will be mating now and then laying the eggs for the 2nd generation of larvae. Tipworm has been quite heavy in Washington County, with the first generation pupating now. One random sample I collected late last week had 75% of tips with injury; and eggs, larvae and/or pupae in 80% of the sample. Cranberry sawfly larvae have been showing up a fair amount, but not in high numbers. The most I have seen anywhere is an average of 7 per 25 sweeps and the threshold is considered to be much higher (30 to 40 or more). But, they are sometimes confused with false armyworm caterpillars, which have a much lower threshold (4.5 per 25 sweeps), so, a little review may be helpful for ways of telling them apart. In this case, I think a picture is worth 1,000 words (see below). The features I look for are the small button-like heads, the tiny black eyes that look like a period at the end of a sentence, the three sets of prolegs that they have up near their heads (no legs through the rest of the body until the very end), the moist appearance they often have, and finally, the way they characteristically curl their hind end a bit while they are crawling (the one in the first picture below is showing that behavior). And remember, sawfly larvae turn into a solitary, non-stinging wasp; they are not caterpillars so caterpillar-specific materials will not work on them and that is part of the reason we are seeing more of them in recent years as more and more of our insecticides are very narrow in their chemistries.
Last, but not least, I was on a bed yesterday that had some mysterious and peculiar-looking holes in them (see photos below). I thought perhaps it was the advanced stage of a disease such as Red Leaf Spot, as there is some of that in the bed as well, and the affected leaves seemed to be limited only to last year’s leaves……..however, upon much closer examination today, we found the culprit: a tiny grub feeding between the layers of the affected leaves. Eventually, the grub pupates, probably falls to the floor of the bed, and the leaf tissue where the grub was eventually breaks entirely away leaving nothing but a hole in its place.
June 3rd: Tipworm has arrived in Washington County! Anywhere there are new shoots rising up from the runners, you can expect to have tipworm taking advantage and laying eggs on them. At the coastal Washington County sites I visited yesterday, I really–for the most part–only saw new shoots along the edges of the beds, particularly along the ditches where the development is a little ahead. But, it won’t be many more days before there are new shoots growing up throughout those entire beds.
Anyone wishing to apply a spray for tipworm should wait until there are new shoots throughout the entire bed, or, spot-treat along the ditches (i.e. areas where you know you have new shoots) if that is an attractive option for anyone. A product like Rimon, remember, will not protect any new growth that occurs, so, you definitely want the new tips to be present before spraying anything.
I also found blackheaded fireworm larvae at two out of four Washington County sites yesterday, either at or well above the threshold. The threshold is only 1 to 2 in 25 sweeps, and, I realize that the thresholds assume a higher price for your berries than you might be able to get this season, but, at the same time, you do not want to ignore fireworm because in just one or two seasons in the absence of control, it can easily reach a point where an entire bed is infested, versus just patchy areas.
June 2nd: New shoots are present now in at least the central portions of the state and probably downeast as well (where I am heading tomorrow). So cranberry tipworm is probably not far off. I have continued to find blackheaded fireworm larvae (1st generation) at the sites in the middle and south-central regions of the state, even when the vines have been soaking wet from rainy periods. I have also been seeing a few false armyworms, but fireworm is the pest I’m worried about. Since it overwinters in the egg stage, I suspect the survival was very good through this past winter because of all the snow cover we had. Here is a picture of one I found on May 22nd, to give you an idea of just how small they are when they are newly-hatched, as this one is. There is no mistaking the shiny black head, though. If the vines are wet when you sweep, look closely along the inside rim of the net, as that is where you will be most likely to see them. If you find any when it is wet, you can probably triple or quadruple that number for what you would likely have captured in your net under sunny & dry conditions. May 20th: Found the first blackheaded fireworm larvae of the season today in central Maine (4 out of 50 sweeps), along with a dozen newly-hatched cutworms including very small false armyworm larvae. It was a bed of Stevens, and the buds looked like they were close to the cabbagehead stage; no new shoots present, but, a lot of swollen buds. No cranberry tipworm yet since there were no new shoots anywhere, but, I did find one male tipworm fly in my net so I have little doubt that when new shoots begin to grow from the runners, the tipworm will be laying their eggs on them. Now, these fireworm that I found are way ahead of schedule according to the growing degree day (GDD) numbers accumulated thus far for the central part of the state, so, I’m not sure what that means. It could be the larvae I found make up a really small percentage of the total population yet to emerge, and so possibly the bulk of the population will be hatching later, when the degree days match up better. Hopefully that is the case, but, it’s a good example for illustrating why the scientific community only ever says that GDD numbers are merely a guide, and should never be taken as absolute.
Preliminary Keeping Quality Forecast: Through the end of April, Bangor picked up 6 points out of a total of 10, and Caribou achieved 7 points out of 10. That gives a forecast, already, of “FAIR TO GOOD” (for Bangor), and “GOOD” for Caribou with 6 more points possible by the end of June for each location.
- Bangor: “Fair to Good” = You should probably not reduce your fungicide rates and/or the number of fungicide applications. (If Late Water was held, however, you can reduce your fungicide inputs in that situation.)
- Caribou: “Good” = Can ‘probably’ reduce your fungicide applications (definitely reduce if you used a Late Water flood)
May 14th: No pests to report on as yet. The degree days are starting to add up, though, and I’ll put an update here as soon as I have anything to report. By the way, if you received your 2014 Northeast US Cranberry Pesticide Chart, you will have noticed mention of a new insecticide material called Grandevo®. It is a bioinsecticide that is approved for organic production. The active ingredient is a naturally-occurring bacterium that was isolated from soil under an eastern hemlock tree in central Maryland. I would not discourage anyone from trying it who is interested, because it has an impressive pest profile against chewing and sucking insects (in general) as well as mites, and not just in cranberries. Those of you who do much vegetable gardening might be interested to know that Colorado potato beetle larvae, leafhoppers, and thrips, are just some of the many pests it is supposedly orally toxic towards. There is a really good EPA fact sheet online that describes its active ingredient. The pests listed on its label for cranberry are: aphids, armyworms, brown spanworm [and spanworms in general], cranberry weevil, cranberry and Sparganothis fruitworm, cutworms, fireworms, leafrollers, mites, and thrips. I would not be surprised if it helped some against tipworm, also, though tipworm is not on the list. The UMass Cranberry Chart Book says that chemigation with it is not allowed, but, it is now. The REI is just 4 hours, and, the PHI is 0 (zero) days. It is worth noting, however, as also indicated on the cranberry pesticide chart, that after it is applied it will repel bees for 4 to 6 days, so, obviously, you would not want to use it near the start of bloom or during bloom.
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: email@example.com]