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.
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 foundBlackheaded 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 5th: Blackheaded 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.
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).
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: firstname.lastname@example.org]