SWD appears with a vengeance at Upper Mountain Research Station

Male D. suzukii on raspberry leaf, Upper Mountain Research Station.  Photo taken 30 September 2010 by Absalom Shank, NC State Horticulture Department

Yesterday, I spent the day at the Upper Mountain Research Station near Laurel Springs confirming the first spotted wing drosophila (Drosophila suzukii) larval infestation in North Carolina.  Spotted wing drosophila (SWD) is a potentially devastating invasive pest of soft skinned fruit which has been present in North American since late 2008.  See here for more background.  Blackberry, raspberry, and strawberry research plots are heavily infested.  SWD were first observed on 30 September in high tunnel primocane fruiting raspberry plots by Absalom Shank, research technician in the NC State Horticulture Department.

Up until last week, no larval SWD had been observed in North or South Carolina, despite the fact that adults have been captured in high numbers.  This is likely due to the fact that most of our trap captures occurred after the majority of susceptible host fruit had been harvested.  It is likely that larvae have been present but in low enough numbers that they escaped detection.

The first thing I did after arriving at the station was to place 6 SWD traps in 3 of 4 high tunnels, where the highest number of flies had been observed.  These tunnels contain primocane and floricane fruiting blackberries and raspberries. Three of the traps were baited with apple cider vinegar, and 3 were baited with a yeast and sugar mixture, as are being used in our regional monitoring program.  Within 20 minutes, the first adults appeared at the apple cider vinegar baited traps.  A total of 4 flies were captured in 3 hours.

Apple cider vinegar baited SWD trap in primocane fruiting blackberry tunnel.  Photo: HJB

Male SWD at apple cider vinegar baited trap entry.  Photo: HJB

SWD larvae were observed last week in fruit from guard plants and caneberry seedling plots, both of which are not regularly harvested.  This week, larvae were found in trial plots, which are harvested twice per week, so flies are not restricted to unharvested plantings.

Fallen raspberries in breeding plots.  These fruit can harbor SWD populations. Photo: HJB

Adult SWD were readily observed and collected in high tunnel plots (and the most of those were in primocane fruiting raspberries), but were not as numerous in outside plots.

Female SWD on ripe raspberry fruit in a high tunnel.  Photo: HJB

Primocane fruiting blackberries in high tunnel.  Photo: HJB.

Primocane fruiting raspberries outside. Photo:; HJB

Many fruit in raspberry breeding/seedling plots were heavily infested, which is not surprising considering that these plots have never been harvested.  Most of the fruit collected contained multiple larvae.

Ripe yellow raspberry from breeding plot.   This single fruit contained 5 SWD larvae.  Photo: HJB

Strawberry plots at the station also contained large numbers of SWD larvae.  Because it was very windy, adult fly presence could not be confirmed in these plots.  Flies which appeared to be SWD females were present, but these are more difficult to sight identify than males.  The fruit damage observed, however, was consistent with SWD.  Sound appearing fruit contained multiple maggots when cut open.  Larvae were collected to rear out adults.

Strawberry containing multiple SWD larvae.  Photo: HJB

These strawberry plots had also not been harvested for several months and contained sound, rotting, and decomposed fruit, all of which are attractive and suitable for SWD larval feeding.

Strawberry plots containing heavily SWD infested fruit.  Photo: HJB

Strawberries with recently laid SWD eggs were also found.  These fruit appeared sound except for a slightly abraded area where the eggs were.

Strawberry fruit with slightly abraded area containing SWD eggs.  Photo: HJB

Enlarged view of SWD eggs.  Photo: HJB

I collected several adult flies and numerous infested fruit to bring back to laboratory to start a research colony.  These insects will be used to test host fruit preference, monitoring tools, and control strategies.  This afternoon I am heading to check my traps at the Sandhills Research Station and check the caneberry breeding plots there for larval infestation. Update: I visited the Sandhills Station today.  See here for a summary of what I found.


SWD Monitoring
We have been monitoring SWD in NC, SC, and VA for 5 months and have detected flies in Montgomery County, NC; Lee County, NC; Randolph County, NC; Davidson County, NC; Edgecombe County, NC; Saluda County SC; Spartanburg County, SC; and Lexington County, NC.  We can now add Ashe County, NC to that list.

Small fruit and tree fruit growers should be aware that SWD populations are present at potentially damaging levels and should carefully monitor their plantings for adult and larval presence.  Caneberry growers with primocane fruiting berries and strawberry growers with fall fruiting or day neutral plantings should be especially aware.  Adult traps can be constructed from plastic containers or bottles (see here for a description of trap construction and here for videos demonstrating trap construction and use).  Sticky cards for use in traps can be obtained from a variety of sources.  We get ours from Great Lakes IPM.  Male SWD are readily distinguished from other flies by their spotted wings.  Females are more difficult to distinguish, and growers should consult their county extension agent for identification confirmation if males are not present.  See here for examples of SWD and non SWD flies on sticky traps.  Traps should be checked at least weekly.

Growers should also monitor fruit for larval infestation.  Large larvae will be visible in fruit, but small larvae may not.  Larvae can most easily be detected via the "fruit dunk" method.  Fruit are gently crushed and floated in sugar water.  After several minutes, larvae float to the surface and can be counted.   See here for a video and here for a description.  A hand lens may be necessary to observe small larvae.  It is important to remember that many native Drosophila feed on rotting fruit.  Observing infestation in relatively sound fruit and confirming adult presence minimizes the likelihood that you will confuse SWD with native relatives.

SWD Management
Sanitation is extremely important in managing SWD.  In areas where SWD is present, all ripe fruit should be removed from the field or plants should be treated with insecticide regularly, with the interval depending upon the material used.  Unmarketable fruit should be destroyed or removed from the site.  Composting may not be sufficient to kill SWD larvae and may attract adults to rotting fruit.  This presents a challenge to fruit breeding activities at research stations and will need to managed with care.

SWD populations in the western US (California, Oregon, and Washington) appear to respond well to a number of insecticides, which is encouraging news.  I am preparing a document listing the registered materials that are effective against SWD by crop and will have this available early next week.  Growers who have confirmed SWD should contact their county cooperative extension agent or myself for management recommendations.  It is especially important to rotate insecticides used to treat SWD to minimize the likelihood of resistance development.

More information
OSU SWD Website
Spotted Wing Drosophila Updates - WSU Mount Vernon Research Center
Strawberries and Caneberries - Blog by Mark Bolda (UC Farm Advisor)
NC Small Fruits IPM SWD Posts



Sponsored by the Southern Region Small Fruit Consortium, Project 2010 E-01.

Fall NC Entomological Society Newsletter

October is a busy month for the North Carolina Entomological Society! Read all about our recent and upcoming events in the NCES Fall Newsletter.

More information
Fall 2010 Newsletter - NCES

UNC system facilities are 'in a mess' - Education - NewsObserver.com

The Entomology Department is also housed in Gardner Hall. Although my lab is in another building, it's in no better condition.

More information

UNC system facilities are 'in a mess' - Education - NewsObserver.com

North Carolina Entomological Society seeks outstanding teachers!

Do you know a teacher (K-12) who uses insects in creative ways in their classroom?

If so, the North Carolina Entomological Society wants to know! We are seeking outstanding teachers who use entomological tools in their classroom, whether to teach students about the wonderful world of insects or to assist in the teaching of other concepts. Last year, we recognized 3 teachers, Susan Dixon (Western Alamance Middle School, Elon), Kathleen M. Dorn (Hunter Huss High School, Gastonia), Teresa Garrou (Hudson Elemenary, Hudson), one each for elementary, middle, and high school.

Teachers can nominate themselves or others. Strong applications typically include examples of of the insect learning activities used. This can include lesson plans, photos, example assignments, and more. Applications are due to me either via mail (NC State University, Campus Box 7630, Raleigh, NC 27695-7630) or email (hannah_burrack@ncsu.edu) by October 15, 2010. Application information can be found here. This year's awards will be presented at the NCES banquet on November 5th at the JC Raulston Arboretum and comes with a monetary award to be spent on school supplies. Travel and registration to the banquet are included in the prize, and we hope winners will be able to join us to be recognized.

More information
NCES Outstanding Teacher Award Application
North Carolina Entomological Society

SWD trapping update - Identification overview

One male spotted wing drosophila (circled) and 3 non SWD. Trap from Davidson County, NC. Photo: HJB

Drosophila suzukii (spotted wing drosophila) trap captures are increasing throughout the Carolinas. Last week, SWD were confirmed from our monitoring site in Davidson County, NC, and we continue to catch flies at 7 other locations in NC and SC. The table below summarizes these locations and the total flies detected to date. See here for links to trap capture data for all of the southeast monitoring locations.

Site	Date of first capture	Total flies to date
Davidson County, NC	8/24/2010	19
Edgecombe County, NC	7/30/2010	1
Lexington County, SC (Site 1)	7/30/2010	6
Lexington County, SC (Site 2)	8/6/2010	19
Spartanburg County, SC	8/13/2010	4
Saluda County, SC	7/2/2010	5
Randolph County, NC	7/27/2010	9
Montgomery County, NC	8/11/2010	17

In addition to SWD, several other flies have been caught in the traps, many of which can be confused with SWD. The image above includes 1 male SWD with clearly visible wing spots (circled) and 3 other flies which could be confused with SWD. The image below notes the key characters to distinguish between these 3 flies.

Non SWD flies. Left: fly with "cloudy" cross veins (cross vein circled). This cross vein will not be cloudy in SWD wings. Center: fly with spotted abdomen. SWD will have no discrete spots along the abdomen. Photo: HJB

Also found in yellow sticky traps have been flies with 3 spots on each wing (below).

Drosophilid fly with 3 wing spots (indicated by blue boxes). Photo: HJB

In addition to flies which may potentially be confused with male SWD, there are also flies which may be difficult to distinguish from female SWD. The most important female feature is the prominent ovipositor (below). The ovipositor can be hard to distinguish when insects are on yellow sticky traps, but can be teased out and still appears different than that of any other female fly.

SWD ovipositor. Fly captured in Edgecombe County, NC. Photo: HJB

Female SWD on yellow sticky trap, ovipositor indicated by blue box. Photo: HJB

Ovipositors of non SWD females are much smaller and lack the dark brown teeth on the anterior margin.

Non SWD females. Note much smaller ovipositors that lack dark marginal teeth (click to enlarge). Photo: HJB

More information

Washington State University SWD ID Guide



Sponsored by the Southern Region Small Fruit Consortium, Project 2010 E-01.

Watching the west: SWD in grapes

Washington State University has assembled several SWD fact sheets on spotted wing drosophila (SWD) in grapes.  They have also shared an update on no-choice laboratory assays on SWD in grapes.  The results from this first round are promising (see here), indicating that grapes may very in the suitability to SWD by age and variety.  These results are highly preliminary, but interesting.

More information
Washington State University - SWD grape trial update
Washington State University - SWD in wine grapes factsheet
Washington State University - SWD in Concord grapes factsheet 

Tobacco splitworm damage spiking throughout NC

Tobacco leaf with damage from tobacco splitworm larvae (Phthorimaea operculella). This leaf had at least 20 galleries. Photo: HJB

Damage due to tobacco splitworm larvae has dramatically increased at sites in Johnston, Columbus, and Chowan Counties in the past two weeks. Masters student Monique Rivera has been studying the seasonal biology and behavior of tobacco splitworm for the last 2 years and is wrapping up her thesis research this fall--just in time to see the damage this insect can do in the field.

The accepted ESA common name for the tobacco splitworm is the potato tuber moth, which reflects the fact that this insect is also a pest of potatoes, feeding on the tubers. For at least the past 5 years, however, the tobacco splitworm has been present in tobacco plantings where no potatoes have been found. This suggests that the insects are coming from other sources into tobacco fields. Although little work has been done on tobacco splitworm as a pest of tobacco, research conducted in the early 1900s in Maryland suggested that dry, hot years resulted in the greatest amount of tobacco splitworm injury. This observation appears to hold true for our recent NC infestations, with widespread injury in 2007, 2008, and now 2010.

Tobacco splitworm larvae are leafminers in tobacco, creating distinctive galleries. Female moths lay eggs at the base of tobacco plants, on the soil surface. After the larvae hatch, they move up the stalk and begin feeding on leaves. Damage first appears on lower stalk leaves, but the larvae are capable of feeding on leaves throughout the plant if lower stalk leaves are not present. Newly hatched larvae are roughly 2 mm long, and the galleries they create are also small. Splitworms typically spend their entire larval lifespan in a single gallery, although they may feed internally on leaf veins, making it appear as though they create multiple galleries. In total, a single mature gallery takes up roughly 2 square inches (see above image).

Sites in Johnston, Columbus, and Chowan Counties have had in excess of 50 galleries per plant. Work conducted in the NCSU Entomology Department in 2006 through 2007 found that very high numbers of splitworm larvae like this may reduce total yield. Yield, however, was not the primary concern of growers in Johnston County. It is possible that even fairly low (5 or more full size galleries per leaf) could reduce leaf quality.

Tobacco splitworm gallery (circled). Photo: HJB

Late instar (nearly mature) tobacco splitworm larva in opened gallery. Photo: HJB

Partially cured tobacco leaf with tobacco splitworm injury. Photo: HJB

Growers first noticed the infestations in Johnston County after harvested leaf had been placed in barns. Large numbers of larvae began to flee through the base of the barns and were killed in yellowing leaf.

Tobacco splitworm larvae outside curing barn. Photo: Bryant Spivey, Johnston County NCCE

Dead tobacco splitworm larvae near the door of a bulk barn. Photo: HJB

Curing leaf without tobacco splitworm damage. Photo: HJB

Curing leaf with high levels of tobacco splitworm infestation. Photo: HJB

Management
Although they can be potentially devastating, tobacco splitworms are an occasional pest of tobacco, and preventative treatment is not recommended. It is also not recommended to treat adult moths because they likely do not spend the majority of their time in tobacco. Instead, management strategies should be targeted to the larval stages.

Scouting is key to effective splitworm management in tobacco. Based on trapping and field monitoring conducted since 2007, it appears we have 2 to 3 splitworm generations during the tobacco growing season. Years where 3 generations occur are likely to result in the greatest crop damage because each successive generation will attack the same tobacco. Damage from the early generations indicates that a population is present in a field and that this field should be observed carefully. Early generation damage will appear on the lowermost leaves, and scouting before and after topping should focus on these parts of the plant. Pesticide treatments should be applied if damage begins appearing up the stalk and live larvae are present in these mines.

Treatments should be made when new mine formation begins. Treating mature larvae in mines will likely not be economically beneficial, because large larvae have already caused most of the damage they will do at this stage.

Adult moths can monitored using pheromone baited sticky traps, which are attractive to males and appear to be relatively specific. This means they do not appear to attract large numbers of non target moths which could be confused with tobacco splitworms. Monitoring data conducted in North Carolina for the last 3 years suggests that adult moth trap captures peak 3 to 4 weeks before infield damage. This suggests that adult trap capture peaks could be used to time in field applications of pesticides to control larval infestation. Moths are also caught in fields where no damage occurs, however, so relying only on trapping is not advisable. It is possible that traps could be deployed in fields where early season injury is noted in order to effectively time late season, potentially economically damaging, populations.

Male tobacco splitworm moth captured in pheromone baited trap. Moths appear as similar to many other species to the naked eye. Photo: HJB

Two insecticides, Belt (flubendiamide) and Coragen (chlorantroniliprole) are registered for tobacco splitworm in North Carolina. However, there is very little data on either of these materials against tobacco splitworms, and I cannot recommend one over the other for control at this time. We are working to generate more data on these materials and their appropriate rates.

Why now?
Historical data suggest that tobacco splitworm injury is most problematic in hot, dry years. I suspect that the fields where we are seeing injury now may have received less rainfall than other areas. The marked decrease in the use of broad spectrum, foliar insecticides may also have contributed to increases in splitworm injury. A behavioral shift in the larvae or adults may have resulted in preference for tobacco over other hosts, which may explain why injury is occurring in areas where no other commercial hosts (ie. potatoes) are present.