A reminder: SWD treatments may flare spider mites

Remember when treating for spotted wing drosophila (SWD), some recommended materials may also flare spider mites.  Information on how to scout and what do here.

More information
What to watch for: Broad spectrum insecticide can flare mites - Strawberry Growers Information Portal

More thoughts on SWD trapping for 2013: How many traps should growers use?

After hearing several permutations on a similar question this week, namely "how many spotted wing drosophila (SWD) traps do I need to use?", I posted this information on the Strawberry Growers Information Portal.

More information
More on spotted wing drosophila monitoring: How many traps should growers use? - Strawberry Growers Information Portal

What to watch for: Strawberry clippers active

I am starting to cross post more information on the NC Extension Portals, and my latest post at the Strawberry Growers Information Portal addresses some of the many questions have gotten this week and last on strawberry clippers.

More information
What to watch for: Strawberry clippers - NC Strawberry Growers Information Portal 

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

What to watch for: Aphids in strawberries

There has been concern among some strawberry growers in the southeast regarding aphid vectored virus infections in plants from some sources. Dr. Barclay Poling, NC State University Horticulture Department, has reported on these observations as they developed in a series of alerts, found at the NCSU Strawberry Growers Portal.

Aphid vector viruses are rarely significant issues in annual strawberry because even if infections occur during the year, they happen later in the season and do not cause economic losses.  In addition, infection from multiple viruses (virus complexes) is often necessary for visual symptoms or loss to occur.  Where aphid vectored viruses can be significant is in perennial production and in nursery production.

It appears that plants suspected to be infected with viruses are restricted to a few plant sources, so for growers who do not have plants on their farm from suspected sources, no additional management is recommended.  However, for growers with suspect plants, management is recommended to prevent early season in field spread.  Systemically applied insecticides are likely the most effective method of managing aphids, and information on using these materials is in the Southern Regional Small Fruit Consortium Strawberry IPM Guide.  Importantly, these materials have application timing restrictions with respect to bloom to protect pollinators.  This restrictions should be carefully followed and are another good reason NOT to preventatively treat for aphids if you do not have suspect plants!  Most North Carolina growers with a need to treat should be able to meet these restrictions. If systemic insecticide applications cannot be made, the alternative foliar materials are more difficult to use because of pollinator concerns and should be applied only if aphids are present--which requires good scouting!

The recommended aphid scouting program is 40 randomly selected leaves per acre, which should be observed for live, non parasitized aphids. If only parasitized aphids are present, treatment may not be necessary.  This is particularly true if you have already treated, because parasitized aphid mummies will often hang on to plants when dead non parasitized aphids will wash away or decay.

Non parasitized and parasitized (brown, rounded) aphids on cabbage. Photo: IPM Images, Alton N. Sparks, Univ of Georgia.

The aphid species we are most likely to have present on strawberries in North Carolina are strawberry aphids, green peach aphids, and occasionally, potato aphids.  It can be important to distinguish between these species, particularly if faced with the need to treat populations with foliar insecticide applications, because aphid species may respond differently to insecticides.

All three aphids can be green but may also be orange to red. Potato aphids, with their larger size and long legs, are perhaps the most distinctive species on strawberries.

Potato aphids (Macrosiphum euphorbiae) nymphs, adults, and winged adults. Photo: IPM Images, Whitney Cranshaw, Colorado State University.

Strawberry aphids can be distinguished from green peach aphids by the presence of knobbed hairs covering their bodies, which can be observed under 20x or greater magnification. University of Florida Extension has a nice image illustrating these hairs.

Strawberry aphids (Chaetosiphon fragaefolii) posses knobbed hairs that can be used to distinguish them from green peach aphids. Photo: IPM Images, Jeffery Lotz, Florida Department of Agriculture and Consumer Services.

Green peach aphids are among the most common aphid pests in North Carolina crops and have a very wide host range.

Green peach aphid adult and nymph. Photo: Jim Baker, NC State University.

If aphids are observed in fields with suspected virus infected plants that do not appear similar to our common species, contact your extension agent and submit a sample to the NC State University Plant Disease and Insect Clinic (or your state resources) for identification.

Spotted wing drosophila biology and management in North Carolina strawberries

The third in my summer series of spotted wing drosophila (SWD) factsheets focuses on strawberries.  Please note, factsheets are shared via Google Documents, which is great for quickly and easily posting files but does sacrifice image quality.  If you would like a printer quality digital copy of this factsheet. Please email me.


You can find the first factsheet on SWD biology and management in North Carolina caneberries here and the second on post harvest SWD significance and sampling here.



This Thursday I will be attending a strawberry field day in Watauga County, NC at a farm that grows day neutral (summer fruiting) strawberries and sharing information from this factsheet as well as results from our spring strawberry SWD management experiments at the Central Crops Research Station. Day neutral strawberries present unique SWD management challenges because they fruit through fall, when the highest SWD populations of the year occur.  You can read more about day neutral strawberries at the North Carolina Strawberry Association's blog.

More information
Strawberry field day - Watauga County Cooperative Extension

Do it yourself: An update on distinguishing SWD larvae from other insects in strawberries

Early this spring, I wrote a post discussing how to distinguish spotted wing drosophila (SWD) larvae from other internally feed insects.  That post was focused primarily on blueberries.  This spring and early summer, however, I received several calls about SWD in strawberries, and they appeared in our research plots for the first time.

Fortunately, the majority of grower calls I received about larvae in strawberries ended up being sap beetle larvae rather than SWD larvae.  Sap beetles or picnic beetles are actually a complex of beetle pests which include at least three species in North Carolina (Carpophilus lugubris, Stelidota geminata, Glischrochilus quadrisignatus, and others) and are attracted to rotting, not sound fruit.  If rotting fruit are present near sound fruit, as can commonly happen when you-pickers aren't thorough or rain prevents picking, sap beetle adults and larvae can also attack sound, otherwise marketable fruit.

While sap beetle larvae are also not desirable in strawberries, they are more easily controlled than SWD.  Good sanitation, meaning removal of overripe or rotting fruit, is usually enough to keep sap beetle populations in check.

How, then, can you distinguish between sap beetle larvae and SWD?

Host fruit
Sap beetles will first attack overripe, rotting, or otherwise damaged fruit.  SWD will be found in fruit that appears otherwise marketable until cut open.  As SWD grow older, fruit condition may deteriorate, but fly larvae found in sound fruit are more likely to be SWD than those found in rotting fruit.

Size
Young sap beetle larvae may be similar in size to large SWD larvae, but in general they will be larger than SWD larvae.  Size on its own is not a good determinant, but it can be a good initial indicator.

Sap beetle larva on knife blade. Photo from a commerical strawberry farm in eastern NC, 2012.

 Appearance
SWD larvae lack legs, have no distinct head, lack hairs or bristles, and are tapered on both ends (see here for more images).  Sap beetle larvae have distinctive head capsules, three pairs of legs, and bristles along their bodies.  Adult sap beetles may also be present along with larvae.

Sap beetle larva. Note the three pairs of legs, the distinctive brown to black head capsule and the bristles along the body.  Sap beetle larvae will be mostly white or cream colored and lack patterns on their body. Photo from a commerical strawberry farm in eastern NC, 2012.

Two spotted wing drosophils larvae (center) inside a day neutral strawberry, Upper Mountain Research Station, October 2011. Photo: HJB

What other insects might be present inside strawberries?
Corn earworm (Helicoverpa zea) are occasional pests of strawberries, and the larvae can tunnel into berries.  Corn earworms are caterpillars, which means they have a distinctive head capsule and three pairs of front legs like sap beetle larvae, but they also have short, grippy prolegs along their abdomen and have a pattern of stripes along their body (although their appearance can be highly variable as larvae age).

Corn earworm larvae feeding on strawberries. Photo via UC IPM.

What causes misshapen strawberries?

Recently, I've gotten a few questions about misshapen strawberries.  Misshapen or "wonky" strawberries can be caused by several things, but the two most common causes likely to occur in North Carolina are poor pollination and lygus bug injury.  It's actually fairly straightforward to distinguish between these two types of injury.

Poor pollination
Strawberries do not require, but benefit from, insect pollination, so weather conditions that limit insect activity and pollen movement typically precede when this type of misshapen fruit appears.

Misshapen strawberry fruit due to poor pollination (above) and a normal appearing fruit (below). Photo: HJB

Poor pollination causes misshapen fruit because unfertilized seeds remain small and the fruit around them does not grow at the same rate as the fruit around fertilized seeds.  On the image above, the top fruit has seeds of different sizes next to each other while the seeds on the bottom fruit are uniform.

Lygus bug injury
North Carolina Department of Agricultural (NCDA) regional agronomist David Dycus mentioned via email today that growers in Mississippi had recently expressed concern about misshapen fruit due to lygus bug feeding.  Lygus bugs (also known as tarnished plant bugs) feed on strawberry seeds and fruit and can also cause misshapen fruit.  Lygus feeding does not result in variable seed size and can, therefore, be distinguished from poor pollination in strawberries.  Typically, North Carolina growers do not experience extensive damage from lygus bugs, because they are active later in the year.  This year, however, they may be active earlier (although, our warm spring has turned a little chillier), and it's worth keeping an eye for their damage.  Lygus can be difficult to control, so if grower suspect they have damaging populations of lygus present, they should contact their county agent or myself for recommendations.

Strawberries damaged by lygus bugs. Photo: UC IPM Program

Other, non pest, insects can look like lygus bugs, include beneficial insects like big-eyed bugs and non strawberry pests insects like false chinch bugs, and it's important to correctly identify pests.  BugGuide has a nice identification guide for Lygus lineolaris (the east coast species which feeds on strawberries).

Other causes of misshapen berries
Insects and poor pollination are not the only causes of misshapen fruit in strawberries. Pathogens can damage fruit, mechanical injury can scar it, and abiotic factors can change fruit shape.

Update, 27 April 2013
An update to this post has been added to the NCSU Strawberry Growers Information Portal.

What to watch for: flea beetles in strawberries?

When Duplin County extension agent John McIntyre called me asking about flea beetles in strawberries, I was skeptical.  Flea beetles are common pests in tobacco & vegetables in North Carolina and one species feeds on grapes, but I had never heard of flea beetles as pests in strawberries.  I figured that whatever damage was present was likely due to our bumper crop of caterpillars or other, more typical pests. However, when he sent me these pictures, it was clear that the beetles pictured were flea beetles or something very similar and that feeding damage was from them.

Two adult flea beetles on strawberry foliage. The "lacy" feeding damage is characteristic of many foliar feeding beetles. Photo: John McIntyre, Duplin County NCCE.

Adult flea beetle with John's figure for size reference. Photo: John McIntyre, Duplin County NCCE.

Also present on leaves and tunneling into at least one strawberry fruit were what appear to be the larvae of these same beetles. After seeing these images, my first thought was that theses beetles looked an awful lot like grape flea beetle, a relatively common early season grape pest whose adults and larvae both feed on developing buds and foliage in grapes.  See here for a nice set of images from Michigan State University of grape flea beetle adults and larvae.  It turns out that grape flea beetle (Altica chalybea) has a close relative known as the strawberry flea beetle (Altica ignita), so it's possible that that these may be either species or a completely different critter.  John brought samples of the larvae and adults by my office this evening, and I'll identify them over the weekend and post an update here.


So, now that I believe we're dealing with a flea beetle, what should the affected growers do?  I do not think that the foliar injury in the images above will result in yield loss, and I suggested that the growers not treat if only foliar feeding was present.  However, one larva John found had tunneled into a strawberry.  If lots of larvae are present and potentially feeding on fruit, this is of much greater concern.  Unfortunately, most of the pesticides effective against flea beetles are broad spectrum and may flare spider mites in strawberries, which have already become problematic in strawberries this spring throughout the southeast.  There is one narrower spectrum material that might work can be organic as well, and I suggested to John that if larvae were present, this might be the best choice.  See a note about pesticide recommendations.

Update, 10 April 2012
I took the adult beetle and larval samples to Dave Stephan, insect identification expert at the NC State University Plant Disease and Insect Clinic this afternoon. Dave agreed that it does indeed look like it is from the genus Altica, but he suspected that they were too small to be grape flea beetle.  He is going to run them through a key to determine if they are strawberry flea beetles or something else entirely!

What to watch for: caterpillars everywhere!

Caterpillar feeding on developing blueberry buds. Photo: Bill Cline

Worms or caterpillars, whatever you prefer to call them, there is an bumper crop of larvae in North Carolina this spring.  My colleague, Steve Frank, ornamental and urban horticulture entomologist, spoke to the Raleigh News & Observer this week about about the large number of cankerworms present in state, and this afternoon, I received calls about caterpillar damage in two crops, blueberries and strawberries.  The abundant caterpillar populations are likely due to warm spring weather; many insects have been able to begin an early generation. In blueberries, this has resulted in isolated pockets of large numbers of what appear to mixed populations of spanworms, cankerworms, and other generalist caterpillars.

A diverse assortment of caterpillars from southeastern North Carolina blueberries. Photo: Bill Cline.

 One grower who has noticed large caterpillar populations in Reveille, a later flowering variety, and asked plant pathologist Bill Cline what the potential management options might be.  In the past, blueberries grower may have used malathion, a broad spectrum insecticide, applied in the late evening to control caterpillar populations.  I instead suggest that the grower use a narrow spectrum material that is safer to bees, as the plants to be treated were close to bloom.  Regardless of how safe a pesticide may be for bees, if plants are to be treated during bloom, any material should be applied in the evening minimize exposure to bees and allow for maximum dry time before they begin foraging.

The second question was from a research station in Virginia, where they had noticed green caterpillars present in their ripening strawberries.  My suggestion for strawberries would be the same--select a narrow spectrum, bee safe material.  These would include microbial (such as Bt) or insect growth regulators (such as Intrepid). See a note on pesticide recommendations.  Following any treatment, plants should be carefully scouted for re infestation, since high insect pressure situations may result in more movement into crops.  Just because caterpillars are present in a crop again following treatment does not necessarily mean that the treatment did not work.  Insects can also move back into plantings following a treatment.

What to watch for: strawberry update

This morning, I visited our strawberry research plots at the Central Crops Research Station, Clayton, NC.  We will be using these plots for sap beetle, caterpillar, and spotted wing drosophila research this spring, and, like most of the southeast, our plants are pushing early.  It looks as though we will have berries in about 3 weeks, which is a month ahead of our normal schedule.

Along with this potentially early strawberry crop comes early questions about pest management.  I have fielded lots of questions about strawberry clippers and two spotted spider mites in the last few weeks.  I posted several times last spring about strawberry clippers, and you can find those posts here.  You can also find my posts on spider mites from the last several years here.  For grower with spider mite populations at threshold (5 mites/leaflet in a sample of 10 leaflets per acre) and plants that have not yet started fruiting, now is a good time to get those populations under control.  You can prevent mite issues later in the season by treating now with a miticide and avoiding the use of broad spectrum insecticides (pyrethroids and carbamates) unless absolutely necessary for other insect pests. If a broad spectrum material is needed, for example against sap beetle or SWD infestations, scout for spider mites before and watch populations carefully follow a treatment.  For growers who do not have mites about threshold (or no mites at all), you can breathe a little easier--barring a major slow down in plant growth, you may avoid the need to treat at all for mites.  Once plants are actively fruiting and rapidly growing, mite populations must be very high to cause damage--and very high mite populations typically only develop if you start off with mites earlier in year (around now). 

More information
Strawberry clipper posts - NC Small Fruit and Specialty Crop IPM
Two spotted spider mite posts - NC Small Fruit and Specialty Crop IPM

Southeastern strawberry preplant meetings underway

The 2011 strawberry preplant meetings are underway, and I will be attending the Sandhills meeting tonight in Carthage, NC. You can find a list of all upcoming strawberry preplant meetings here. Tonight I will be discussing spotted wing drosophila (SWD) biology and significance in strawberries and strawberry clipper considerations.

Strawberry clipper is a relatively infrequent pest in the southeast, but the North Carolina Sandhills is a clipper hot spot. I am planning an on farm trial in this region next spring to address some of the key questions about strawberry clipper management. Namely, how much does clipper damage impact strawberry yield, and how do southeastern strawberries respond to damage?

For those not able to attend preplants, the SWD slides I will be covering are embedded below. Bear in mind that the maps in this presentation are current as of July 2011 and are subject to change.



I will also be attending the South Carolina preplant on August 18, 2011 where SWD will be the main topic.

More information
Preplant meetings and fumigation resources - NC Strawberry Association
Strawberry clipper posts - NC Small Fruit & Specialty Crop IPM

Strawberry season coming to a close

After another short picking season, we are pulling the plug on our strawberry research plots at the Central Crops Research Station near Clayton, NC this week. The spring of 2010 was also a quick, short growing season, and I am curious how many other strawberry farms are wrapping up harvest in the next few weeks. I am also curious if this pattern is related to our cold winters, and if short seasons are the norm under these conditions. We will maintain our planting for the next few week to monitor for spotted wing drosophila, but our two mite trials have ended because the plants are growing more foliage than fruit at this point.

SWD trap in strawberry plots at the Central Crops Research Station, 2011. Photo: HJB

It's always a little bittersweet to end a field project, so I read the latest post from Berry Girl, a relatively new strawberry grower near Goldsboro, NC with interest. They, too, are ending their field season for the year and looking towards next year. I've enjoyed reading their blog this spring and hope they keep it up!

More information
Bowing out - The True Adventures of Berry Girl

Strawberry clipper update

Last Wednesday, I visited Lee County to check on our strawberry clipper traps and take counts. We continued to see clipped buds (20 of 30 plants checked), but the damage appeared older and no adults were captured on the traps. It will be interesting to see if the damage continues this week. Clipper counts are also picking up at other locations in the Sandhills, I have now heard reports from 3 different locations where clipper has been observed.

Strawberry clipper weevil adults on wild blackberry buds. How many clippers can you find? There are 11 in this container. Photo: HJB

More exciting, however, was what I found this morning in my growth chamber. The clipper eggs that I collected 2 weeks ago have completed their larval stages and are now adults. This answers the first question I had in mind when I brought them back to the lab. At a constant temperature of 28C, the strawberry clippers took about 15 days to complete their larval stages. Now that I know I can successfully rear beetles from infested buds, my next goal is to collect enough adults to conduct a laboratory bioassay of registered and unregistered materials to control clipper weevil adults. This will go a long way to making more meaningful treatment recommendations, particularly for newer, reduced risk materials. However, we still need to understand the real impact of clipper damage in terms of yield for our production system before I am willing to advocate an aggressive pesticide program.

In the meantime, I will be keeping my adult beetles on flower buds, since they have been documented to feed on flowers and pollen. This appears to be correct, because the beetles went straight for the unopened blackberry buds I placed them on and started chewing away.

Strawberry clipper update

I returned to the Lee County farm I visited last Friday to check the sticky traps I placed and count any additional damage.  Also visiting were Seth Holt, Lee County agriculture agent; David Dycus, NCDA & CS regional agronomist; and Brenda Gwynn, new Lee County Horticulture Agent.  The sticky traps I placed at the end of the rows nearest to the woods caught 3 clipper weevil adults, which is a promising result.

Yellow sticky trap placed at the end of a strawberry clipper damaged field in Lee County.  Photo: HJB

Yellow sticky trap with a strawberry clipper weevil (among other insects) in center, circled.  Photo: HJB

Strawberry clipper from sticky trap, up close.  Photo: HJB

 Clippers were also readily distinguished from other weevils on the traps.  If traps can detect strawberry clipper movement from their overwintering sites in the woods into fields, perhaps they can be used to time scouting efforts and insecticides treatments (if necessary).  The four of us also counted damaged plants in the 3 untreated row ends the grower left.  Damage had increased since last week.  Twenty-one of the 31 plants observed had at least one clipped bud, and damage ranged from 1 to 6 clipped buds per plant.  In the treated parts the rows, 11 of 13 plants observed at least one clipped bud.  This suggests that the treatment applied last week is no longer effective and that clippers remain active.  I replaced traps and will be returning next week to check them and assess damage.  My goal is to determine how long the clippers remain active and if the sticky traps continue to catch adults.

Even though flower buds continue to be clipped, I am uncertain that the plants will experience economically significant yield loss from damage at this time of year on young, unopened buds.  Before leaving today, we made plans to conduct an on farm trial at this locations next spring designed to determine if aggressive clipper treatment will significantly improve yield.

What to Watch for - Strawberry clipper weevil

I spent last Friday morning visiting a strawberry grower in Lee County, North Carolina who had noticed the first damage from strawberry clipper weevil (Anthanomus signatus) in his field on Thursday.  Because his farm has a history of strawberry clipper, the grower had been scouting every other day and observed that damage went from zero to several clipped buds per plant in the 2 days since he last scouted.

Strawberry clipper weevil females lay their eggs in developing flower buds of strawberry, blackberry, raspberry, dewberry, and red bud.  Female beetles then chew through the pedicel, which supports the flower bud.  This causes the bud to drop from the plant.  The larvae develop in the dropped flower bud over the course of 3 to 4 weeks.  Adults emerge in mid summer, briefly feed on pollen and then overwinter.  There is only one annual generation of strawberry clipper.  Beetles overwinter in wooded areas, so fields located near the woods or rows closest to the woods often experience the greatest clipper injury. 

Mating strawberry clipper weevils. Photo: Tom Murry, BugGuide.

Rain in Lee County in Thursday had knocked many of the damaged buds off the strawberry plants, but there were still many plants with multiple clipped buds.  I collected several damaged buds to take back to the lab and examine for eggs or larvae.  On Friday, all I found were eggs, but by today (Monday), the buds contained quickly developing larvae.

Clipped strawberry buds (center).  Photo: HJB

Stawberry clipper egg inside strawberry blossom.  Note oviposition hole to the upper left of the egg.  The female weevil will chew a hole through the sepal and  petals and then deposit the egg inside the flower.  Females lay one egg per flower.  Photo: HJB

Strawberry clipper larva after 4 days in a 28C (82F) growth chamber.  I was surprised to see how rapidly they had grown over the weekend!  Photo: HJB

The grower had treated the night before with Sevin XLR, a relatively "safe" pesticide to bees when dry.  No pesticide is completely safe for bees; therefore, I do not recommend pesticide use during bloom if at all avoidable. If pesticides (insectides, fungicides, herbicides, or others) are necessary when flowers are present in fields, they should be applied in the evening, after bees are done foraging, to allow for the longest drying time possible before bees become active again. See "A note on pesticide recommendations". The grower left 3, 15 ft sections near the edge of the field untreated for me to observe over the next few weeks.  I placed yellow sticky traps to determine if we could trap beetles walking into the field and counted the damage on 10 plants per row.  Of the 30 plants I observed, 11 had at least 1 clipped bud, and damage ranged from 1 to 5 buds per plant.

A recently clipped bud. Photo: HJB

The big question in this case is whether treatment was necessary to prevent further strawberry clipper damage.  Insecticides have been demonstrated to reduce adult clippers, and therefore the number of clipped buds.  Research on the impact of clipper in New York (English-Loeb, et al.1999, subscription needed to view full article) found that all strawberry varieties tested compensated well for early season clipper damage, or in the words of the authors, damage to primary and secondary buds.  Only damage in late season (tertiary) buds resulted in a significant yield loss because the the plant was not able to mature additional fruit.  A closely related species has been studied in Europe in perennial strawberry plantings (Aasen and Trandem 2006, subscription may be needed to view full article), where yield does appear to be improved when insecticides targeted to clippers are applied.  I am not aware of any studies on compensation on Chandler, Camarosa, or Sweet Charlie, the strawberry varieties most commonly grown in North Carolina, so we cannot necessarily say if they will behave similarly to those observed in New York (Earliglow, Kent, Jewel, and Seneca).  However, I think it seems likely that our varieties can and will compensate for early season clipper damage.  For this reason, I believe that the thresholds currently recommended by entomologists in Virginia (0.6 clipped buds per ft) or New York (2 clipped buds per meter) are certainly conservative enough to prevent economic loss and are probably more conservative than necessary.  Further work is needed on compensation in our key strawberry varieties as well as strawberry clipper biology in North Carolina. 

Management tools for spotted wing drosophila in NC

Because we detected spotted wing drosophila (SWD) in the Carolinas in 2010 before any commercial fruit was compromised, we have this winter to prepare growers and homeowners to detect and manage this new pest.

The first step to managing SWD is to determine whether it is present on your farm or garden. We have detected SWD in 13 counties in NC and SC, but we have been monitoring 24 locations and do not have traps in all possible fruit growing areas. This means that: 1. Some locations do not yet have SWD, and 2. Some locations may have SWD and we may not have detected it yet.

2010 NC and SC SWD Monitoring locations (blue dots) and counties with confirmed SWD trap captures. Figure: HJB

Growers and gardeners should work with their county extension agents (or myself) to trap for and identify SWD. See here to find your county extension agent in NC. Expert identification confirmation is recommended for the first detection at location to ensure that SWD is not confused with native Drosophila species. See the NC Small Fruits, Special Crop, and Tobacco IPM SWD Page for links to SWD identification guides.

Once SWD presence has been confirmed and at risk (ripe) fruit is present, chemical treatment is the current recommended means of commerical management. Cultural control, namely sanitation, can greatly reduce damage but will not eliminate it. Fruit should be frequently and regularly harvested and culls (non marketable or non edible fruit) should be disposed of off site. Burying culls will not necessarily kill SWD. Culls should not be left on the ground because they can be reinfested.

I have adapted factsheets which list the registered, commerical insecticides and their possible impact on SWD developed by Oregon State University entomologists for North Carolina. Links to these factsheets are provided below. The insecticides listed are registered for commerical fruit production, not for use by homeowners. Cultural controls may be sufficient to reduce SWD damage in gardens. If not, contact your cooperative extension agent for pesticide recommendations. The information provided in these factsheets does not replace the insecticide label. The label must be followed at all times; it's the law!

More information
Insecticides registered for use in blueberries & their potential use against SWD
Insecticides registered for use in caneberries & their potential use against SWD
Insecticides registered for use in grapes & their potential use against SWD
Insecticides registered for use in strawberries & their potential use against SWD

Strawberry high tunnel production workshop - November 17

NCSU specialists Jeremy Pattison, Barclay Poling, and myself will be at the Piedmont Research Station near Salisbury, NC on Wednesday, November 17th for a workshop on high tunnel strawberry production. I will be covering twospotted spider mite biology and management in tunnels (a project we have conducted for 2 years) as well spotted wing drosophila monitoring and management implications in tunnels.

You can find information on the workshop here.

More information

Strawberry high tunnel workshop - NCSU and NCDA & CS

Southeast Strawberry Expo Handouts

I present at the Southeast Strawberry Expo in Virginia Beach, VA yesterday and today.  I am never sure exactly how many handouts to bring to this type of meeting, where attendees select the sessions they will attend the day of the meeting.  If you attended the Expo and did not get a handout, or if you were unable to make it this year, you can find links to two of my handouts below.  I will post the slides from my presentation later this afternoon.  I also distributed a draft of the 2011 NC Agricultural Chemicals Manual strawberry insect management guide.  The 2011 Manual will be online in mid December.  In the meantime, you can find the 2010 Manual here.

Southeast Strawberry Expo Handouts
Arthropod management in strawberries: a fall & winter update
Pesticides registered on strawberries and their possible efficacy against spotted wing drosophila (This document is adapted for NC and VA growers from a similar resource developed by Oregon State University entomologists.)

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.