2015 Reports: Starting soon!
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: firstname.lastname@example.org]