Spotted wing drosophila monitoring recommendations for 2013

Spotted wing drosophila traps in strawberry plots at the Horticultural Crops Research Station, Clayton, NC. Photo: HJB

Strawberries are just beginning to ripen in central North Carolina, so last week, we placed spotted wing drosophila (SWD, Drosophila suzukii) traps in our research plots at the Horticultural Crops Research Station in Clayton, NC.  Eagle eyed observers will noticed some differences in the traps in the photo above and those we placed in our SWD plots a few years ago.

Shading traps placed in strawberries

What's easily visible above is that our traps have "hats".  We added these hats because work from other labs suggested that SWD like shade and that leaving traps uncovered in strawberry plantings may catch fewer flies.  In a multistate comparison of SWD traps conducted in 2011, a trap with a "hat", referred to as the Haviland trap, caught more flies than other trap types in a range of different crops.  Hats are likely not necessarily in crops with shaded areas or where traps can be hung directly from host plants, like blueberries, cherries, and caneberries.

A Haviland-type SWD trap with a "hat".  In this case, the hat is meant to keep rain out. The Haviland trap performed well in a comparison of SWD traps during 2011.Photo: HJB

Bait recommendations

In previous years, we have used apple cider vinegar (ACV) as the primary bait in our SWD traps and for the SWD*VMN because early experiences suggested that it was easier to work with compared to a yeast & sugar slurry (the other bait we tested).  However, these early experiences were based on changing the baits less frequently than every week.  When baits are changed weekly, yeast & sugar lures appear to catch more flies and may catch flies earlier than ACV.  Therefore, for 2013, we're suggesting that SWD trappers consider using yeast & sugar lures rather than ACV.

In order to make the yeast & sugar bait, follow the steps below:

Ingredients for yeast & sugar slurry: yeast & sugar! Photo: HJB

1. Collect the bait ingredients, active yeast and plain sugar.

2. Combine 4 Tbsp sugar with 2 Tbsp yeast.

3. Add 32 fl oz of water to the dry ingredients and stir till the mixture is suspended. Do not store premixed bait in a sealed container.  It is actively fermenting (which is what attracts flies) and can explode.  It's easiest to mix bait as it's needed rather than premixing.

4. Fill traps with 150 ml of bait (or just over 5 fl oz) each.  Traps should be check and baits changed weekly.  The odors associated with these non preserved baits change over time, and after one week, they are likely less attractive to SWD.

A few other helpful hits for using yeast traps:

• Many other insects find fermenting yeasts attractive. Traps should have small entry holes, no more than 3/16 large.  Otherwise, larger insects such as beetles, filth flies, and moths will clog traps.
• Trap contents can be poured into a container for transport back to the office or lab rather than counted in the field.
• Do not discard used bait in the field.  We do not want to make our fields any more attractive to SWD than they already are!
• Kitchen sieves can be used to filter flies, but flies in yeast baits might need be rinsed after filtering to see wings, legs, and ovipositors (key ID characteristics) clearly. 

It's very likely that our bait recommendations will change for next year, based on experiments that are planned or already underway. SWD is an invasive species, meaning it's new to North Carolina, and many other areas. Therefore, many of our monitoring and management recommendations are subject to change.  We are all learning a lot of new information, as quickly as we can!

For the time being, we have not changed our trap recommendations. We are still suggesting using 32 oz plastic containers for 2013, although this recommendation is also subject to change, especially if commercially available traps become available that out perform homemade traps.

More information
Plan to monitor insects in 2013 - NC Small Fruit & Specialty Crop IPM

The future of the SWD*VMN for 2013 and beyond

Male (right) and female (left) spotted wing drosophila on a raspberry at the Upper Mountain Research Station, Laurel Springs, NC. Photo: HJB

For the last three years, we have coordinated the Spotted Wing Drosophila Volunteer Monitoring Network (SWD*VMN).  The goals of the SWD*VMN were:

1. To detect the movement of spotted wing drosophila (SWD) if or when it spread throughout the eastern United States
We began the SWD*VMN in 2010, when SWD had only been detected in Florida in the eastern US. The SWD*VMN facilitated the first detections of SWD in South Carolina, North Carolina, Tennessee, Virginia, Arkansas, Louisiana, West Virginia, and Maryland.

2. To determine when during the year SWD are active and relative population densities throughout the year
SWD have been detected earlier each year in states where the SWD*VMN has been active.  In 2012 and 2013, some locations in the southeast caught flies throughout the entire winter. Peaks in trap captures in NC appear to occur in mid summer (July) and fall (after September), with fall populations appearing the largest.  However, these trap capture peaks are subject to interpretation because the traps and baits we use are likely not as attractive to SWD adults as fruit. 

Dates of first trap capture for eastern states participating in the SWD*VMN. Table from Burrack, et al. Journal of Integrated Pest Management.

3. To communicate and display information on detections and trap captures with growers and extension personnel
All trap captures from the SWD*VMN are available here (click on a county to link to the sites in that county and then click on site names to view data from that site). Our policy has been to only identify sites to county.

Along the way to accomplishing these goals, we've been able to gather some additional information. During 2010, we compared different lures at SWD*VMN sites and learned that some baits need to be changed more frequently than others. Our relative trap capture numbers have suggested that some crops may either foster lower SWD populations or be less conducive to our trapping methods.  For example, we catch more flies in shady crops such as caneberries and some grapes and fewer flies in crops with open, sunny canopies such as strawberries and blueberries.  Importantly, this does not necessarily mean that we have fewer flies in theses systems.

Where does the SWD*VMN go from here?
We have accomplished the initial goals of the SWD*VMN and reached the end of the funding which supported the large statewide (in NC) and multi state efforts (much thanks to the Southern Region Small Fruits Consortium and the NC Tobacco Trust Fund, Inc. for their support).  We have also produced a journal article article to more widely share our findings from the SWD*VMN.

Moving forward, we will maintain, and improve the SWD*VMN site for use by our lab and partners in other states to collect, store, and display SWD trap capture data. Collaborators in OR, TN, AR, NY, and other states have expressed interest in continuing to use the site.  The improvements on the way for the site include incorporating graphs to display data for each site and, in the more distant future, incorporating degree day models being developed for SWD by folks in the western US.

In our lab, we will be using the SWD*VMN to collect data from our planned 8 to 12 trapping locations throughout the state, most of which will be at NCSU or NCDA & CS Research Stations. However, we will no longer be directly facilitating large scale SWD monitoring through our laboratory.  We've posting lots of "do-it-yourself" SWD monitoring information and will be posting a monitoring update for 2013 later today.  Please feel free to contact us if you have questions about the SWD*VMN.

More information
SWD*VMN at EDDMapS
All SWD*VMN posts at NC Small Fruits & Specialty Crop IPM

Plan to monitor insect pests in berries in 2013

One of the most important pest management practices growers can impliment is montoring insect pest populations.  This allows management pratices to be targeted when damaging populations are present and also provides a wealth of information about future pest populations.

We’ve posted lots of information about monitoring methods for insects in berry crops, including a series of “do-it-youself” (DIY) posts.

Do-it-yourself insect monitoring:

Spotted wing drosophila monitoring

Spotted wing drosophila monitoring videos

One caveat to our spotted wing drosophila (SWD) trapping recommendations-many new baits and lures are in the process of being developed for SWD. We no longer believe that apple cider vinegar is the most appropriate bait for traps. Instead, we are suggested that interested trappers use a mixture of 4 Tbsp sugar plus 2 Tbsp active yeast dissolved in 32 oz water. Traps should be filled 1 to 2 inches deep with this bait and changed weekly! After one week, yeast baits become unusable.

Distinguishing SWD larvae in strawberries  and in blueberries

Blueberry maggot monitoring

Grape root borer monitoring

Changes are afoot!

Over the last few months, I've been working with NCSU CALS Extension IT to develop NC State supported tools to support online information delivery--like this blog!  As part of that process, we are developing an Entomology "Portal", which will house all of our entomology extension information.

As part of this transition, I will soon be starting to cross post articles to the Entomology Portal as well as here.

Stay tuned for updates!

What insecticides are acceptable where?

Over the last few days, I have received several questions about spotted wing drosophila (SWD) management.  The most common question from growers, agents, and others has been: What insecticides are acceptable for use on fruit that will be exported to other countries?  A significant amount of the blueberries, blackberries, and raspberries grown in North Carolina are marketed by companies that sell world wide. A lower percentage of the strawberries grown in the states are sold outside NC, but some growers also work with large marketers to sell their strawberries who may sell fruit outside the US.

While we know what insecticides are acceptable for use crops grow in the US (if it's labeled on the crop, it's acceptable for use here), not all the options available for US growers are acceptable for use on products that will be exported.  Pesticide residue tolerances (or maximum residue levels, MRLs) must be established in receiving countries for a material to be acceptable for export to that country.  One tool I use frequently to determine if pesticide residue tolerances have been established in other countries is the MRLDatabase, developed by the USDA Foreign Agricultural Service (FAS).  This large database allows you to search by crops, pesticides, and countries in lots of combinations.  Just like any pesticide use information, material presented in this database is subject to change.  Therefore, I always recommend that growers speak with their marketer before using a new management tool to ensure that it is acceptable for the markets their fruit may be sent.

More information
MRL Database - USDA FAS

NC Commerical Blackberry and Raspberry Growers Association Meeting - February 19

There's still time to register for the NC Commercial Blackberry and Raspberry Grower's Association Meeting in Shelby, NC on February 19th. I will be there to discuss what we learned about spotted wing drosophila in 2012 and where we go from here.  Gina Fernandez, NC State University, caneberry breeder, has posted meeting details on her blog.

More information
NC Commercial Blackberry and Raspberry Growers 6th Annual Meeting - Team Rubus

Spotted wing drosophila confirmed from Indiana and the United Kingdom - Update: SWD also found in Texas and Colorado

States where Drosophila suzukii, also referred to as spotted wing drosophila, has been detected in the continental United States. Adapted from Burrack, et al. 2012. Journal of Integrated Pest Management.

Spotted wing drosophila (SWD) was confirmed in Indiana during October 2012, bringing the total number of states with confirmed populations of SWD to 33.

SWD was also detected in United Kingdom in September 2012, which brings the number of countries (including the US, Canada, and Mexico) where SWD has been detected outside of its presumed native range of eastern Asia to at least nine.

Update, March 7, 2013
While reviewing the National Agricultural Pest Information System's (NAPIS) Pest Tracker records for spotted wing drosophila in preparation for an upcoming presentation, I noticed two additional state level detections for 2012 that I had previous missed, Texas and Colorado.  These detections bring the total number of states where SWD has been detected to 35 since 2008.

More information
First find of spotted wing drosophila in Indiana - Purdue Plant & Pest Diagnostic Laboratory
Strawberry alert: The 2mm fly that could decimate Brittan's fruit industry - The Daily Mail
Drosophila suzukii - European Plant Protection Organization (EPPO) Factsheet