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Cooperative Extension: Maine Wild Blueberries


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SWD Management Recommendations Fact Sheet

Attached is a fact sheet for SWD management in Michigan Highbush bluberries (SWD Management for Michigan Blueberries_June 21 2014) , which is very informative and includes a table with rain steadfast properties of some of the SWD insecticides.

Here is the link to the the SWD Management for Michigan Blueberries  http://www.ipm.msu.edu/uploads/files/SWD/SWDManagementforMichiganBlueberries_-June212014.pdf

Spotted Wing Drosophila (SWD) September 3, 2013

SWD trap captures in Washington County remained steady and similar to last week. At the University of Maine Blueberry Hill Farm, we continue to capture anywhere from 1 to 30 flies per trap; and the proportion of fruit that have SWD larvae appears to be very low (less than 1 %) as we still have not detected any in our fruit samples.   

The harvest is beginning to wind down in many areas; however, if you still have fruit to harvest you should continue to monitor for this pest and protect your fruit if necessary. This is especially true in the southern and mid-coast part of Maine. In these regions fruit infestation is being found and individual trap captures range from 0 – 200 flies / trap with flies being caught in every field that is being monitored.

SWD captures were continuing to build in Michigan’s highbush blueberry fields last week. Most growers were getting very good control with the recommended insecticides, but some growers were suffering a breakdown and getting infested fruit with SWD…THEREFORE, IF YOU HAVE NOT HARVESTED AND SWD CAPTURES ARE BUILDING, YOU SHOULD BE CONSERVATIVE AND PROTECT YOUR CROP UNLESS YOU CAN HARVEST IT IN THE NEXT FEW DAYS.

WE WILL CONTINUE TO MONITOR TRAPS AND CHECK FOR FRUIT INFESTATION THIS WEEK.

NOTE:  Please refer any questions, comments or concerns to Frank Drummond, 1.800.897.0757 (Maine only) or 207.581.2989, frank.drummond@umit.maine.edu or to Dave Yarborough, 1.800.897.0757 or 207.581.2923, davidy@maine.edu.

SWD updates will only be sent out and posted on our blog when we have trap captures.

Spotted Wing Drosophila (SWD) August 26, 2013

SWD trap captures continue to build throughout the state.  At the University of Maine Blueberry Hill Farm, we are now catching 10-30 flies/trap.  Traps in other areas downeast are now capturing 30+ flies/trap.  These SWD continue to be mostly females; however, males appear to be making up a larger percentage than in previous weeks.  The increasing trap captures is evidence of fly reproduction and subsequent fruit attack. The proportion of fruit that have SWD larvae still appears to be very low; we have not yet detected any in fruit samples.  

Please continue to monitor and protect your fruit if necessary from this pest. Also, it looks as if the early harvesting that has been taking place all over the state will certainly pay dividends this year if we can get much of the crop in before significant damage starts to be detected.   Just remember that based upon last year’s monitoring, this pest can explode in numbers very quickly from just a few flies to hundreds / trap…so do not relax too much!   This is especially true as we get close to September. Last year SWD trap captures by September were averaging 40-50 flies/trap! 

NOTE:  Please refer any questions, comments or concerns to Frank Drummond, 1-800-897-0757 (Maine only) or 581-2989, frank.drummond@umit.maine.edu or to Dave Yarborough, 1-800-897-0757 or 581-2923, davidy@maine.edu.

SWD updates will only be sent out and posted on our blog when we have trap captures.

Spotted Wing Drosophila (SWD) August 20, 2013

This summer appears to be a bit different than last year, the first year that we experienced SWD. It does appear that SWD is starting to build, evidence being multiple captures of 2-7 flies/trap with a few males being captured. However, the buildup appears to be slow and there are still several fields that have NOT captured any SWD yet. As far as blueberry growing regions go, SWD captures have occurred everywhere at this point with the highest numbers in the southern coastal area. Because of the evidence of reproduction in the field, resulting in fruit infestation, I suggest monitoring and if you have caught a single male SWD or multiple females then you should harvest that field immediately or protect it with an insecticide. I still believe we are safe from fields having significant damage as we have not been finding SWD larvae in fruit samples as of yet.

As I stated last week, please continue to monitor and protect your fruit if necessary from this pest. Also, it looks as if the early harvesting that has been taking place all over the state will certainly pay dividends this year if we can get much of the crop in before significant damage starts to be detected. Just remember that based upon last year’s monitoring, this pest can explode in numbers very quickly from just a few flies to hundreds/trap…so do not relax too much! 

NOTE:  Please refer any questions, comments or concerns to Frank Drummond, 1-800-897-0757 (Maine only) or 581-2989, frank.drummond@umit.maine.edu or to Dave Yarborough, 1-800-897-0757 or 581-2923, davidy@maine.edu.

SWD updates will only be sent out and posted on our blog when we have trap captures.

Spotted Wing Drosophila (SWD) August 13, 2013

Trap captures of spotted wing drosophila continue to occur throughout the state, BUT appear to have jumped up a bit. There are still some fields that have not had trap captures and many have had just the 1 or 2 SWD. However, late last week  in southern Maine, trap captures jumped quickly with one small fruit field in Bowdoinham having over 200 SWD in a trap! Yesterday in Jonesboro we were finding 2-15 flies/trap in fields that a week ago just had either no captures or 1 SWD in a trap. Therefore, this is evidence that SWD are beginning to multiply in blueberries. The infestation must be still very low. We took fruit samples yesterday in the fields that had increasing SWD trap captures and we still did not detect larvae in the fruit and so the infestation is most likely spotty in the fields and at very low levels. However, from last year it became apparent that SWD can build up very rapidly.

Please continue to monitor and protect your fruit if necessary from this pest. Also, it looks as if the early harvesting that has been taking place all over the state will certainly pay dividends this year if we can get much of the crop in before significant damage starts to be detected.

NOTE: SWD updates will only be made when we have trap captures.  Please refer any questions, comments or concerns to Frank Drummond, 1-800-897-0757 (Maine only) or 581-2989, frank.drummond@umit.maine.edu or to Dave Yarborough, 1-800-897-0757 or 581-2923, davidy@maine.edu.

Spotted Wing Drosophila (SWD) August 4, 2013

As of last week, trap captures of spotted wing drosophila continue to occur throughout the state. There have only been a few fields at this point where multiple flies are being caught. Most fields either have had NO trap captures yet OR just one or two SWD. We have identified SWD larvae in fresh fruit from Coastal Maine, but fruit still appear to be free of larvae in the Downeast region. I suspect that SWD larvae might be appearing in more fields over the next few weeks. At this date many larvae have been observed in fruit, but they have almost all been larvae of the blueberry fly (BMF).  The abundance of this pest is extremely high this year and can be very damaging. Please continue to monitor and protect your fruit if necessary from this pest.

Both larvae of SWD and BMF are a translucent white color. The BMF larvae are pointed in the front and very thick and blunt at the rear and so they resemble more of a cigarette that has one end twisted to a point. The SWD larvae are pointed at BOTH the front and the rear.

I will let everyone know when I start finding or hear about others finding SWD larvae Downeast.

NOTE:  SWD updates will only be made when we have trap captures. Please refer any questions, comments or concerns to Frank Drummond, 1-800-897-0757 or 581-2989, frank.drummond@umit.maine.edu or to Dave Yarborough, 1-800-897-0757 or 581-2923, davidy@maine.edu.

Spotted Wing Drosophila (SWD) July 30, 2013

 Trap captures of spotted wing drosophila continue to occur throughout the state. All blueberry growing regions have reports of SWD males and many fields have experienced multiple captures, indicating that reproduction is occurring and fruit infestation is taking place. But, let me be clear NOT ALL fields have captured SWD yet. On the other hand, we have started to find SWD larvae in fields, both in the coastal area and Downeast. Infestation levels are not high yet, but this confirms that SWD is now beginning to reproduce in blueberry fields. THEREFORE, It would be prudent to protect your crop as soon as possible if you have captured male SWD in your field. Keep the crop protected until harvest. See SWD fact sheet on the wild blueberry web page for more information on effective insecticides.

It is also sobering and informative that last week, Michigan found a sudden rise in captures of SWD adults in traps deployed in highbush blueberry fields. They are recommending growers to take action if they have been trapping SWD and for those not monitoring to start to do so.

Spotted Wing Drosophila (SWD) July 25, 2013

More SWD have been captured in the Downeast growing area on the blueberry barrens. Male SWD were caught and confirmed in a few locations. At the University of Maine Blueberry Hill Farm SWD have been caught in more locations throughout the fields there. So far our fruit sampling (several fields sampled yesterday) has not revealed any SWD larvae in the fruit, but the recent capture of male SWD suggests that reproduction of this pest in blueberry fruit may have commenced. If you are capturing male SWD consider protecting the crop until harvest.

Blueberry fruit fly (BFF) appears to be in high densities in many locations throughout the state. Do not forget about monitoring and managing for this significant pest. Some fields have noticeable BFF attack in their fields demonstrated by considerable shrunken berries.    

Again, as stated earlier in the week, we recommend that you continue to be vigilant and monitor for BOTH SWD and BFF. Be prepared to protect your crop if SWD trap captures occur. Again, hopefully a significant amount of harvest can occur prior to SWD captures in some fields.

Spotted Wing Drosophila (SWD) July 22, 2013

More SWD have been captured in the coastal growing area. Nine flies were captured this past week in a Warren field and continued single SWD detections have been found in Union and Lincolnville. However, despite the number of fields where this pest has been captured in traps there are still SEVERAL fields in this area that have not detected SWD. The first capture Downeast was in Marshfield last week, but as of today no other occurrences have been reported. It APPEARS that recent applications of insecticide to control blueberry maggot fly might be negatively affecting SWD as fields that we had found SWD in earlier and that were sprayed have had few if any subsequent captures. This is just a guess, because it could also be that the hot weather we had last week was detrimental to SWD as well. It has been reported that SWD does not tolerate extremely high temperatures.

Last week we collected fruit samples from coastal and central Maine and inspected the fruit for SWD larvae infestation using the “salt water crush test”. The fields sampled were fields that have had SWD reported in them for at least a week. Thus far, we have not found any SWD larvae in fruit, but we will sample more fields this week.

At this point we recommend that you continue to be vigilant and monitor. Be prepared to protect your crop if SWD trap captures occur. Again, hopefully a significant amount of harvest can occur prior to SWD captures in many fields.

NOTE: SWD updates will only be made when we have trap captures.

Spotted Wing Drosophila (SWD) July 8, 2013

It is no wonder with this HOT weather over the 4th and following weekend a few more SWD captures have surfaced since my update on July 2nd.  However, last week’s capture of a male SWD in Cherryfield was a misdiagnosis. When we looked at it, two spots were found on each wing and so we have NOT had a recent SWD capture Downeast yet. But, in the south…male SWD were captured in Dresden and Whitefield on July 3rd in the southern coastal blueberry-growing region. On Saturday, July 6th, I found a male SWD in a Winterport blueberry field. I have deployed 20 traps in this field and only ONE trap had an SWD. I also have 25 traps deployed in a Stockton Springs field, but as of yet no male SWD have been identified and I have not had a chance to go through all the traps for microscopic detection of females yet.  I am guessing that from the low number of captures that SWD has not completed its first generation, producing new adults.

An important and timely question…What shall I do if I detect male SWD in traps in my field at this time of year (early July)?  I think the thing to first state is that if you have only a slight proportion of ripe (blue) berries (< 0.5 % or so) then don’t panic. At this point I believe ONLY the overwintererd SWD are in our fields as of yet and SWD needs RIPE fruit to lay eggs in. However, they will attack these fruit and start to build in numbers over the next several weeks. So, there is a trade-off between: 1) starting to protect your crop too early with insecticides and having to spray many times prior to harvest and 2) incurring damage and fruit loss. Each grower has to strategize to solve this dilemma of whether to take action or not.

ONE WAY of finding a solution to this problem is to determine at what percent of ripe fruit in your field is the trigger for action.  As an example…If you typically get 2,500 lbs / acre on a given field and guessing on past prices you can estimate what you will get for your crop…then you can calculate how much loss in revenue you will incur if SWD takes 1, 2, 5, 7%, etc., of your crop and you can determine what the economic threshold would be…or in other words the cost of crop loss that will equal the cost of controlling SWD (application + insecticide cost). So, in our example if you normally get $0.75 / lb, then 1, 2, 5, and 7% infestation EARLY in the season will cost you…25, 50, 125, or 175 lbs / acre or in dollars…$18.75, $37.50, $93.75, or $131.25…in this case if it costs you $100/acre to treat the crop then somewhere between 5 – 6% crop loss would be your decision making trigger to treat, meaning 5 – 6% of your crop being ripe.

The calculation above is ONLY a guide. Growers are different in their aversion to risk and price that they receive and so it is not possible to give a simple one answer that fits all.  BUT, this being said another thing you might want to consider prior to an insecticide application is to take a known sample of ripe fruit from your field (small collections from several locations throughout field). Place a quart of your fruit in a gallon zip-lock baggie and mix a salt solution of 1/4 cup salt to 4 cups water.  Lightly crush the berries in a bag and add the salt solution.  Allow the fruit to sink to the bottom of the bag and wait approximately 10-15 min.  Several baggies can be easily set up if you want to sample more than 1 quart of fruit. If the fruit is infested, the larvae should float in the solution for you to visually inspect (See my SWD factsheet showing what larvae look like).  NOW you have a better idea of crop loss that exists at the time of sampling.

The last aspect of EARLY SWD management that I want to bring to your attention comes from my inspection of blueberry fruit fly traps this past Sunday in the field. I was at a field in Stockton Springs and the threshold (10 cumulative flies / trap) was already surpassed at 13 flies / trap. So, if this grower is thinking about a perimeter spray (a location where we also tend to capture lots of SWD)…then an insecticide that is ALSO effective against SWD would be a logical choice. An insecticide that would NOT a choice is imidacloprid (ADMIRETM, PROVADOTM, MONTANATM, PREYTM, etc.) since efficacy against SWD is low. Reduction of SWD adult numbers as a result of a perimeter blueberry fruit fly application might buy you some more time before you need to manage for SWD or maybe even allow you to harvest early making an insecticide treatment specifically for SWD not necessary. However, at this point we do not know how this might play out and so it is no guarantee that spraying for blueberry fruit fly will have any effect on SWD.

*A NOTE…for organic growers the above points are also relevant. Insecticide options are EntrustTM or PyganicTM. The capture of SWD may also be a trigger for deploying exclusion netting over your crop or for deploying a grid of bait cups (every 25 ft) throughout exceptionally high yield areas of your field as a trapping out tactic.      

NOTE: SWD updates will only be made when we have trap captures.


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Contact Information

Cooperative Extension: Maine Wild Blueberries
5741 Libby Hall
Orono, Maine 04469-5741
Phone: 207.581.3188, 800.287.0274 (in Maine) or 800.287.8957 (TDD)E-mail: extension@maine.edu
The University of Maine
Orono, Maine 04469
207.581.1110
A Member of the University of Maine System