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Maine Cranberry IPM Updates

2008 / 2007
Aug 14 July 15 July 3 June 12 May 29 May 21 May 16 May 15
May 13 May 2 May 1 April 17

August 14

Not 'too' much pest news to report on.  The most pertinent development of note is that cranberry fruitworm populations appear to be high this season, so be vigilant with fruit inspections, since at some sites with high numbers it may not be too late to try to reduce some of the populations, targeting larvae that might be exiting one berry in search of another.  Fruitworm larvae in western Maine are largely at maturity and probably very unlikely to succumb to any pesticides applied now, but downeast sites may still have some windows of opportunity left, if any earlier sprays were disrupted by the high number of rainy days we had during that period.  The fruitworm mating and egg-laying activity may have been prolonged under such conditions, making control of the fruitworm extra challenging this year.  One organic grower in the state has reported an estimate of a 25% loss to date, surmising that his first application of Entrust was probably washed off due to heavy rain. Tipworm: There are still tipworm larvae to be found in new-growth tips in the Columbia Falls area, but there is an absence of eggs so I think we are probably seeing the final generation of larvae for this season occurring now.  Callisto: Growers are still very happy with the performance of Callisto. One grower, spot-treating with a high rate, has seen a little bit of damage to the cranberry plants, but it has been exceeding expectations as far as damage to weeds is concerned.  Even yellow loosestrife is not standing up to the Callisto - at least in one spot-treatment situation I've seen.  
 

July 15

2nd-generation blackheaded fireworm caterpillars are showing up in tips now, and very heavily at two central (and central/southern) areas of the state! Both of the affected locations are organic, however, so for growers who have sprayed any insecticides this season for any other pest (including 1st-generation fireworm), any potential fireworm threats now will likely remain in check.  Tipworm: There is much overlap of life stages occurring most everywhere that has tipworm this season (there was one site that as of June 27th still did not have any tipworm, or had it in such low numbers that I couldn't detect any in my sample or when I was there looking for it).  Assail, used for fireworm suppression, appears to work very well against the early (1st) instar tipworm larvae, giving--in a recent case here in Maine--100% control of 1st-instars, and 70% control of 2nd-instars.  Against the orange-colored, final instar, larvae, control is far more challenging -- just 15% in that same case where the earlier instars were controlled so much better.  This lack of control of the final instars is consistent with the lab studies done at the UMass Cranberry Experiment Station.

July 3

Insects: To my knowledge (and to my sweepnet), since the middle of June, caterpillar pests have not been an issue for anyone. Numbers have been very low. Tipworm populations have been extremely variable from site to site, though consistently lower than in previous years for growers who have added Assail to their insecticide regiment this season.  For growers who haven't used Assail*, tipworm numbers have been all over the board (zero, remarkably, at one site with no insecticide use at all other than B.t., but at other non-Assail sites the levels are generally in the 60%+ range for infestation and damage levels). Callisto is performing extremely well against weeds.  Even cinquefoil, which is reported to be one of the harder ones to knock out with Callisto, did not fair very well after only a single application.  Yellow loosestrife is growing now at sites with a history of it, and most of them are now above the cranberry canopy.  None of the sites where I know yellow loosestrife is abundant have used Callisto, so I cannot report on Callisto's effectiveness against that weed at this time.

Next insect to be watching for: Blackheaded Fireworm (2nd generation larvae) (watch for uprights that are pulled together at the tips, with webbing holding them together)

Umbrella Bloom - As was the case last year, there is a large amount of umbrella bloom to be found again this year.  I believe it is due to tipworm injury in our (i.e. Maine's) case.  Many uprights with the umbrella bloom have the beginnings of small side shoots, near the tips, that I suspect will yet grow out and therefore rectify the abnormality.  That is precisely what took place in at least one bed in 2007, and the yield from that bed was a record-setting yield for that particular grower.

* Note: Tipworm is not on the Assail label for a target pest. Cranberry fruitworm and fireworm are. Keep in mind that blackheaded fireworm goes through two generations each season, with the 2nd generation of caterpillars beginning in mid to late July.

June 12

Insects: Oddly, cranberry tipworm numbers have been very low thus far at all but one location (that I've visited).  This has been true even at locations where no insecticides have been applied (including one organic site, for example).  Tipworm numbers were--until now--also very low in Massachusetts this season, suggesting they are just extremely late for some reason this year. 

Where Assail has been sprayed against fireworm, tipworm numbers have also been very low, though it is proving difficult to know if the low tipworm counts are due to the Assail when tipworm numbers have been so low everywhere else as well.  As the season progresses, this uncertainty should evaporate. 

Numbers of false armyworm and blackheaded fireworm caterpillars have been below threshold at most locations.  Fireworm larvae were still being caught in the Augusta area as of June 10th, with counts of 4 per 25 sweeps at one site (threshold is 1-2).

Callisto: Callisto has worked very well at each of two locations I have seen it used on to date.  In Washington State, growers have learned that a second application is needed to control most perennials. They usually apply the 2nd dose once re-growth occurs, but on some weed species, control is best when the second application is applied 2-3 weeks after the first.  The timing of that 2nd application depends heavily on the sensitivity and vigor of the specific weeds being targeted. Yellow loosestrife needs to be hit early, often and hard. For other weeds, the general strategy is to let them die back, and wait for regrowth before putting on the 2nd application. 
 

Decorative red button signaling an alertMay 29 (Spring caterpillars, and tipworm)

Just when it looked like perhaps our spring caterpillar pests weren't going to be terribly abundant this year, yesterday was a wake-up call.  Out of two sites in Waldo County that I had checked earlier this month with very little activity occurring, each site this time had a heavy outbreak taking place -- blackheaded fireworm at one location, and false armyworm at the other.  Numbers were roughly ten times the threshold for fireworm (as high as 1 fireworm per 10 uprights), and two times the threshold for false armyworm.  I've never before seen such a high level of first-generation blackheaded fireworm! 

Make sure you sweep your bed(s) each week, and don't throw away the contents of your net too quickly.  The green, active, false armyworms are easy to see and count right away, but with the blackheaded fireworm, you have to be extremely patient and thorough, and paw through the leaf litter/debris frequently, in order to scare the tiny caterpillars out of hiding.  I highly recommend using something with a white background (in full sunlight if possible) when spreading out your net contents.

Tipworm Update: I found my first 2008 tipworm egg and larva yesterday, in southern Waldo County.  So I would expect them to be showing up in Washington County by June 4th. 

May 21

As expected, we saw tipworm flies in western Maine today, but only a few caterpillar pests, and none of them were fireworm.  Numbers of everything were extremely low (way below threshold).  It could be that false armyworms are just a little late this year, or else it just won't be a high/good year for them.  Tipworm flies were also reported in Mount Vernon today, having shown up throughout the course of May 19th.

Decorative red button signaling an alertMay 16

I was in Troy and Lincolnville today, and found a tipworm fly at each location -- yes, only a single tipworm fly in 50 sweeps at each location, but now we know the tipworm is starting. No eggs found on any tips sampled at either site as yet, but that will soon change, as the flies only live for 3 to 5 days.  Tuesday I will be in Turner, where I would imagine tipworm is present now as well. Blackheaded fireworm larvae have JUST hatched in Troy as well.  I found 4 of them in 50 sweeps today (or 2 per 25 sweeps).  Dump your sweepnet contents onto something white (a sheet of paper will work), spread the leaves around a little, and then let it sit for a few minutes while you patiently watch  -- the fireworm larvae, if they are there, will eventually begin to crawl out from the debris, and you'll be able to see them easily at that point.  They are way too small to be noticed very well if they remain concealed amongst the leaf litter debris that you'll have in your net, so patience is the key, and somewhere calm enough that the wind won't blow everything away before you've had a chance to study it. False armyworm larvae are present now as well--for sure in Troy and Lincolnville--and probably everywhere with the possible exception of Washington County which might be a few (or more) days behind warmer areas of the state.  Their numbers were already higher in Troy, just since Wednesday, which doesn't surprise me as more and more of them continue to hatch each day with this nice weather we are seeing.

Degree Days: Unfortunately, the number of degree days that accumulated--to mark the start of tipworm and blackheaded fireworm--ended up being considerably less than the number that was derived last year.  I was hoping last year's numbers and this year's numbers would match up better.  What that says to me is that we just need additional years of measurements, before we can pinpoint what the true number of degree days might be, for either the tipworm or the fireworm.  Visit the Degree Days page in order to see the final values.  It could be that the best we can hope for is a 'range' of degree days as a model for these pests.  Even the best degree day models are not perfect.  You still cannot beat your own two eyes!
 

Notice (be advised)May 15

Caterpillars are just starting to hatch now in Troy. Numbers are well below the threshold but that could soon change.  They are so tiny that I'm not ready to say for sure whether they are false armyworms or not, but that would be my guess.  I also spotted a few flea beetles, but they are seldom ever observed at high enough numbers anywhere to be concerned. No tipworm flies observed yet, and a sample of 30 tips from Troy yesterday turned up no signs of tipworm, but they should be appearing really soon with these warm temperatures we're seeing.  I plan to travel south to Lincolnville tomorrow.

May 13 (Degree Day Update)

Degree Day accumulations are still considerably ahead of last year. I'll be checking in Troy tomorrow to see if any pests are active yet.  Check out the new page I added that is for keeping track of Degree Day numbers.  There is a link for it on the home page, or you can visit it right now as well:
Link to Degree Day Values

May 2 (Degree Day Update)

The site where I monitored degree days in Troy in 2007 is well ahead of where it was at this same time last year (essentially twice the number of degree days to this point), so I would expect tipworm and fireworm to be perhaps two weeks earlier this season compared to last season, unless we enter an unusually cool period soon. 
 
Comparing 2007 with 2008 (Degree Days) as of May 2nd
Date
Degree Days (Base Temperature of 45F)
Degree Days (Base Temperature of 50F)
As of 5/2/2007
89
44.5
As of 5/2/2008
179.6
81.6
Stevens bud stage at site in Troy:
5/2/2008 photo
Total DD believed to be needed for Tipworm & Blackheaded Fireworm, for two different base temperatures
From Year 2007 Findings 
DD Using Base Temperature of 45F
DD Using Base Temperature of 50F
Cranberry Tipworm Flies
~510
~344
Blackheaded Fireworm larvae
~456
~301

May 1

The new insecticide, Assail, that just got a cranberry label, may be just what the doctor ordered, for tipworm control!! Its active ingredient is acetamiprid, and is a neonicotinoid that has activity against eggs, larvae and adults! It was one of the materials tested in the Wisconsin trials in 2005, and control of the tipworm was reported to be virtually 100%. Since it is NOT an organophosphate, I am hopeful that it will work very well for us, against tipworm populations that have not been exposed to much else over the years, and it will provide a means whereby growers can rotate back and forth between Assail and Diazinon (or any other OP), thus theoretically keeping the efficacy high for both of those choices/classes of insecticide.  Assail is toxic to wildlife, including bees (considered mildly toxic to bees), so don't use during bloom.

There is a new and improved version of SpinTor available for use (for caterpillars), called Delegate (Delegate WG).  It is also higher than SpinTor in its toxicity to bees (considered "highly toxic"), so do not apply it during bloom and be alert to potential drift to any hives or to flowering weeds where a lot of bees might be present.  It is also mildly toxic to aquatic organisms. Delegate contains spinetoram, which is derived from a naturally occurring soil organism, and--together with spinosad materials--is classified as a Group 5 insecticide. Since spinosad and spinetoram fall into the same class, you are not supposed to rotate between these two products, as that would foster the onset of resistance in the target pests.

United Phosphorus, Inc. is no longer making the Devrinol 10G formulation, but it is still legal to use any that you may have or may be able to obtain.

The 2008 Maine Cranberry Pest Management Guide is nearly finished, and I have begun work on a Cranberry Management Calendar for Maine that you can find a link for on the home page. 

April 17

The insecticide, Avaunt (active ingredient is Indoxacarb), received a full registration for use in cranberries late last year. Avaunt is described in Massachusetts as an excellent alternative to Lorsban and Diazinon for black-headed fireworm, spanworms, and Spring generations of cranberry weevil.  It is NOT lableled for summer applications against cranberry weevil because those would be freshly-born weevils that are more robust and so the spray is not effective against those (compared to the Spring weevils that have overwintered and thus are 'old' by insect standards).  It is labeled and works against black-headed fireworm and spanworms. It will also affect cutworms if they are present on the bed. It is NOT a good tool for Cranberry Fruitworm or Spag. The REI is 12 hrs and the PHI is 30 days. Avaunt works against the proper functioning of the insect nerve and must be ingested for greatest effectiveness. Good coverage is key. It is toxic to pollinators exposed to direct application but is said to have low impact on honeybees once it has dried. 
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contact Charles Armstrong at: charlesa@umext.maine.edu
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