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

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 

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.

Another reason to appreciate bees & wasps in grapes

At last Friday's vineyard tour, one of the most common insect questions I get from grape growers again came up. "What can I do about wasps and (less commonly) bees in my grapes?"

My feelings are clear on this subject. I think there is little to be gained from using insecticides against these mostly beneficial insects and significant harm that could be done, both through extending your harvest window and by harming predators and pollinators.  You can read my thoughts on this subject and what growers can do instead of spraying, here.

Today, I read about an even better reason to appreciate wasps, in particular, in your vineyard.  NPR's The Salt blog highlights research from Italy that demonstrates that wasps move wine-fermenting yeasts throughout vineyards and have likely contributed to the evolution of these important yeasts.  You can find the full article here.

More information
What to watch for - Bees and wasps in grapes
Thank the simple wasp for that complex glass of wine - The Salt
Role of social wasps in Sacromyces cerevisiae ecology and evolution - Proceedings of the National Academy of Sciences

What should growers and homeowners who find SWD do?

I am getting reports of spotted wing drosophila SWD larval activity in some southeastern locations over the past two weeks, and we have observed SWD infestation in some of our research station plots in North Carolina.  Infestations in my plots are a good thing, because it allows us to study SWD here and provide you with up to date information, but infestations in grower fields are another matter. We have been catching adult SWD since January in North Carolina, but these are the earliest larval infestations we have recorded in the state.  This early activity has prompted several questions about what growers or homeowners should do if they find SWD infested fruit.  Here's a quick summary of the four key steps you should take in the event of SWD infestation:

1. Remove all ripe and ripening fruit and destroy it (by freezing, "baking" in the sun inside a clear plastic bag for a few days, or removing from the site).  Eggs or larvae may be present in otherwise sound appearing fruit. Leaving this fruit means that potentially infested fruit is present and could be harvested.

2. Begin an aggressive (once per week if it does not rain, reapplication in the event of rain) spray program.  Rotating between at least two modes of action will reduce the likelihood of resistance development.  See here for information about the probably efficacy of registered insecticides in southeastern small fruit crops.  Because these efficacy ratings are based on work done largely in the western US, where environmental conditions differ, they are not set in stone.  We are running several efficacy trials as I type and hope to have NC specific data by mid summer. 

3. Practice excellent sanitation.  Remove all ripe fruit and sell or destroy it.  Do not discard culls in the field, and clean up after rain and u-pickers. Unpicked fruit is a reservoir for SWD larvae.

4. Sample fruit regularly and consider trapping flies.  Traps tell you SWD presence or absence and are not perfect, but they are helpful.  Place traps in strawberry rows, near fruit for the best chance of catching flies.  Sample fruit each harvest by either cutting them open and looking for larvae, crushing them in salt water (1/4 cup salt per gallon), or freezing them.  Salt water and freezing will cause larvae to exit fruit.  Sample at least 30 berries per field.  See here and here for trapping information and here for larval sampling information.

All growers are strongly encouraged to monitor for SWD adults before larvae are found.  If adults are present and fruit are ripe, pesticide treatments are recommended through the end of harvest.  We hope that this strategy will prevent larvae from showing in fruit and triggering the actions listed here.

Update, June 22, 2012
I am aware that homeowners may be not be able or may prefer not to use insecticides on fruit in the gardens are yard.  Unfortunately, sanitation alone will not eliminate and SWD population.  However, if you can pick your fruit a bit earlier or a bit less ripe, it will be exposed to SWD for less time and will perhaps be at a lower risk of infestation.  It's also important to note that while SWD larvae cause fruit to decay quicker and are unpalatable if present in fruit, they are not poisonous or parasitic.  If you have inadvertently consumed fruit from your home garden that SWD larvae have been present in, they do not pose a heath risk.

Update, August 7, 2012
I have been reading LOTS of scientific papers about SWD in the last week.  A couple of Japanese references suggest that mesh cages or bags (specifically 0.98mm mesh) prevented SWD infestation in blueberries without impacting plant growth.  We use mesh bags a lot to either keep insects we are studying in or to keep insects we don't want out.

We have used mesh bags in blackberries to exclude thrips from developing fruit in order to determine if they impact fruit development.  They don't appear to.

This strategy is worth a shot for homeowners who can tolerate the sight of bags on their plants.  In order to exclude SWD, cages should be placed before fruit begins to change color and tightly sealed at the bottom.  We'll often place a piece of quilting foam between the cage and the stem of the plant to allow us to tightly tie the cage shut (with a zip tie or twine) but protect the stem from damage.  Cages should stay in place until you harvest your fruit.  We use organdy mesh from fabric store and sew our cages to size, but paint strainers also work in a pinch.  I plan to try this method with my backyard blueberries, blackberries, and figs next year and will be interested to hear if others also give it a shot.

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

What to watch for: When treating for SWD

Female SWD on raspberry at the Upper Mountain Research Station, Summer 2010. Photo: HJB

As spotted wing drosophila (SWD) is detected in more and more locations throughout the southeast (Georgia, Florida, 4 locations in South Carolina, 13 locations in NC), many small fruit growers are treating their crops. See here for lists of registered pesticides in blueberries, grapes, strawberries, and caneberries. For several reasons (efficacy, cost, and preharvest interval), organophosphate and pyrtheroid insecticides are among the most commonly used materials against SWD. The current management recommendations for SWD are weekly pesticide applications, rotating modes of action, beginning when fruit are ripening and stopping at the end of harvest and increased sanitation (frequent & thorough harvest, cull removal & destruction). These management recommendations represents a potentially large increase in pesticide use, at least in the short term, in these small fruit crops.

While these classes of insecticides are effective against SWD, they come with risks as well. The key risk, from a pest management stand point, is non target impacts on other pests and beneficial insects. While we we cannot anticipate all of the non target impacts, some are clearly likely.

The most likely non target effect of SWD treatments is the possibility to flare spider mites.

Twospotted spider mite female and eggs. Photo: HJB

Spider mites are economically significant pests of strawberries, grapes, and caneberries (raspberries moreso than blackberries). Both organophosphate and pyrethroid insecticides have been documented as flaring spider mites.

Strawberry, grape, and caneberry growers should scout their plantings for spider mites prior to beginning SWD treatments. A good rule of thumb is to observe at least 10 leaves or leaflets per acre or per variety block, if they are smaller than an acre. Spider mites can be observed and counted with a 10x hand lens. If spider mites are present, planting should be treated with a miticide before beginning organophosphate or pyrethroid treatments. North Carolina blueberry growers more commonly use these insecticides are rarely, if ever, have issues with spider mites, and I do not anticipate a need to manage mites in blueberries.

Spider mites may not be the only non target (unintentional) pest made worse by SWD treatments. Organophosphates and pyrethroids are broad spectrum materials, meaning they kill many different types of insects, including beneficial predators. The insects these predators may control could increase in their absence, but we cannot necessarily predict which insects these may be. Growers treating for SWD should be vigilant and scout their fields at least weekly to assess whether any new or unexpected insect or damage is present.

What to watch for: Raspberry cane borer

Damaged blackberry primocane at the Sandhills Research Station, May 23, 2011.  Photo: HJB

While checking our virus vector monitoring plots today at the Sandhills Research Station, near Jackson Springs, NC, I noticed a few plants with classic raspberry cane borer injury.  Female raspberry cane borer beetles lay their eggs near the tip of primocanes causing the end to wilt and creating a distinctive, paired girdling of the cane.

Raspberry cane borers are one the many exciting "boring" insects that feed on caneberries in the southeast.  If left unchecked, the larvae can kill the cane they feed on over the course of 1-2 years, depending on where in the US they are.  In North Carolina, these insects probably have a 1 year larval life cycle.

The injury at Sandhills was very recent, as evidenced by the fact that the end of the cane was just wilted and not dead.  In addition, no larvae were readily found in the cane when I tore it open, suggesting that the eggs have not yet hatched.

Cultural control, via removal of infested canes, is the recommended management strategy for both raspberry and rednecked caneborers, and this is the perfect time to remove raspberry cane borer infested tissue!  Infested primocanes can be tipped, and will continue to grow over the course of the summer.  If left until fall, during the typical pruning period, the entire damaged cane must be removed to ensure the raspberry cane borer larva is destroyed.  Neither raspberry or rednecked cane borer injury typically damages more canes that would be removed through typical fall/winter pruning in North Carolina.  We generally only see significant raspberry or rednecked crown borer injury at locations where pruning has been minimal.  Now is a good time to scout for borers are remove the damaged plant parts before they can get a foothold.

More information
Blackberry borers can mean big problems

What to watch for: Tobacco budworm

First instar tobacco budworm larva in eastern North Carolina tobacco. Photo via Loren Fisher.

Tobacco budworm populations developing
Tobacco budworm (Heliothis virescens) larvae are beginning to show up in North Carolina tobacco fields. At our research plots at the Upper Coastal Plain Research Station, Rocky Mount last week, we found several infested plants, and yesterday at the Lower Coastal Plain Research Station, Kinston, plots were between 0-10% infestation in most of our trials. The vast majority of the larvae present were recently hatched 1st instars, although a few 2nd instars were also present. This means that egg laying occurred fairly recently and that growers will likely begin to see tobacco budworm larvae in their fields soon. In fact, a consultant called Loren Fisher and I last week to report that he and his staff were seeing budworm larvae in fields in eastern NC. Populations in these fields were near treatment thresholds (10%). As always when I discuss treatment thresholds for tobacco budworm, it is important to understand that these thresholds are very conservative, meaning that yield loss has rarely been documented due to budworm feeding, even at much higher infestation rates than 10%.

Campoletis sonorensis wasp searching for young tobacco budworm larvae, Kinston, NC. Photo: HJB

Natural enemies present

Also present in large numbers at the Lower Coastal Plain Research Station yesterday were large number of red-tailed wasps (Campoletis sonorensis) in search of young tobacco budworm larvae to parasitize. The wasps were so common that it was almost easier to follow them from plant to plant than to search for the newly hatched larvae in buds. The large numbers of parasitic wasps also suggests that many of the larvae we saw this week may not make it to adulthood.

Management

For those growers whose fields have tobacco budworm populations at greater than 10% infestation in small plants, have not observed parasitic wasps, and plan to treat, there are several insecticides available (see the NC Agricultural Chemicals Manual for specific recommendations). Some NC growers have used Coragen (a newer insecticide from DuPont) as a transplant water treatment for preventative control of tobacco budworm. Because there is relatively limited data against tobacco budworm using this application method of Coragen, I cannot say how effective or long lasting its activity may be. It also important to note the size of tobacco budworm larvae feeding on transplant water Coragen treatments. First instar larvae may not have fed on enough tissue to kill them, so growers should hold off on making foliar treatments until 2nd instar larvae are present. Caterpillars eat the vast majority of the leaf tissue they will consume as large larvae, so the injury caused by a 1st instar as it develops to a 2nd will not be significant. However, if growers who used Coragen in the transplant water for tobacco budworm control have 2nd instar larval populations above a 10% infestation level and need to apply a foliar, rescue treatment, they should select a different mode of action material, such as Tracer/Blackhawk (spinosad), Denim (emamectin benzoate), Orthene (acephate), or methomyl (Lannate). Growers who have used Coragen in the transplant water should not apply Belt or Coragen as their first foliar treatment following transplant.

What to Watch for - The cicadas are coming! What does this mean for berry crops?

I received an email yesterday from a relatively new blueberry grower in Tennessee which asked an intriguing question: "...Tennessee is expecting the 13-year cicadas in a couple of months. We planted our first planting of blueberries in the spring of last year (2010) so they are coming into their second year of growth. Will the cicadas damage them and if so is there anything preventative we can do?"

For those of you who haven't heard the news, this summer, much of the eastern United States will experience the emergence of Brood XIX (also known as "The Great Southern Brood"), the 19th Brood for this population of 13-year periodic cicadas.  Cicada adults are large, stout insects that feed on plant xylem.  Immature cicadas (nymphs) live underground and feed on roots.  Periodic cicadas, members of the evocatively named genus Magicicada, synchronize their life cycle so that the adults all emerge together over a short period of time.  This adaptation is presumed to be a defense against predation by overwhelming possibly predators.  In addition to the 13-year cicadas that will be emerging in 2011, there are also 17-year periodic cicadas and many non-periodic cicadas that do not synchronize their emergence.  There are also non-periodic species of cicadas, often called "dog day" cicadas because the adults emerge during the hottest part of the summer.

Adult periodic cicada. Photo: Bruce Marlin, Wikipedia.

Adult cicada emerging from nymphal exoskeleton.  Photo: Joseph O'Brien, BugWood.

The first part of the question above is relatively easy to answer.  Yes, cicadas may potentially damage blueberries and other woody perennials such as grapes and caneberries. Young plants, like the recently planted blueberries at our Tennessee grower's farm are likely at greater risk than established plantings.  Strawberries are not at risk of cicada injury because they only lay eggs in woody perennials.  Of course, in order for periodic cicadas to damage plants, they need to be present in large numbers.  While Brood XIX is expected to emerge over a wide area of the southeastern United States, mass emergence will not occur everywhere.  See here for a map of where Brood XIX is expected to emerge, and check here to see if they have been recorded from your town. Chances are good that you will experience Brood XIX this summer if periodic cicadas emerged in your area 13 years ago, and you are in the zone where they are expected.  Cicada Mania is an excellent online compendium of all things cicada-related.  Adult cicada emergence begins when soil temperatures reach 64F.  For those of you without soil probes, Cicada Mania has posted an emergence calculator based on air temperature.

Damage to plants from adult cicada feeding is typically minimal, even for large, periodic emergences. Of greater concern is the damage that females cause through egg laying.  Adult cicadas lay their eggs in woody tissue, under the bark.  From the outside, these oviposition scars look like ragged cuts. 
The leaves beyond oviposition scars wilt and are referred to as "flags".  

Periodic cicada eggs inside a twig.  Photo: John Ghent, BugWood.

The second part of the question is a bit trickier.  Preventative treatments may be tempting, and soil treatments of insecticides have show promise in reducing the number of egg laying attempts by female cicadas.  However, preventative treatments must be made before insects are present.  This means that they may not end up being beneficial if large numbers of cicadas do not appear.  Some foliar insecticides may also repel adult cicadas.  For small plantings, netting is very effective at reducing or eliminating egg laying.  In locations with young plantings a high likelihood of emergence, preventative treatment may be a good choice.  For specific recommendations, contact your county cooperative extension agent.  If you are in North Carolina, see here to find your county extension office.  If you are in another state, you can find your location extension resources here (select your location at the top of the page).

More information
Cicada Mania
Indiana University's Cicada Project (Brood X)

Periodic Cicadas - Clemson University

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. 

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.

What to Watch For - Wasps and bees in grapes

Wasps and bumble bees feeding on grapes. Photos: Ric Bessin, University of Kentucky Entomology

Today I had 2 phone calls and emails about wasps and bees feeding on grapes. Given our warm summer, this is not a surprise. In fact, last Friday when Turner Sutton, NCSU Plant Pathologist, and I were visiting vineyards last week we noticed several varieties (Marsanne & Viognier, to name a few) that were nearing harvest. Like many other crops, this is about 2 weeks earlier than normal. I said to Turner as we were leaving, "All this ripe fruit says to me is that I need to be ready for calls about bees, wasps, and green June beetles," and here we are!

Ripe or nearly ripe fruit coupled with the rain we have recently gotten is a recipe for splitting and other mechanical injury. These injured fruit will attract bees, wasps, and beetles, but they will not just feed on the damaged fruit. Once these opportunist insects are in the grapes, they can also feed on relatively sound fruit.

As I told both people I spoke with today, I do NOT advocate treating bees and wasps with insecticide. There are several reasons for this, with the foremost being that these are beneficial insects. They are our pollinators and predators that we work so hard to maintain all other times of the year. Pollinator heath is a major issue across agriculture systems, and is it irresponsible to be treating bees and wasps with insecticides in grapes. Even if pesticides were used, they will not solve the problem. Most bees and wasps are social insects with large colonies including foraging workers and reproductives. Only a fraction of the workers from a colony will be present in grapes at any given time, and no pesticide applied during harvest is going to have a long contact residual. This means that a pesticide application will kill the relatively small number of foraging workers in a field when it is applied, but leave the rest of the colony intact to re infest when the pesticide has dissipated.

What can be done to reduce bee and wasp injury?

Be ready to harvest.
I am not advocating harvesting fruit before you reach desired brix, but if fruit is ripe enough to split and attract bees and wasps, it is not far from harvest-ready. Harvest clusters as they become mature. This may mean picking several times and picking the early ripening areas (ie. the sunny side of the row) first.

Practice good sanitation.
Remove damaged fruit from the field promptly. Fruit left on the ground or on the vine will attract insects. Powdery mildew and thrips damaged fruit are more prone to splitting.

Be choosy about what you harvest.
Not all the grapes in the field will make it to the crusher. If wasps and bees are damaging a few early ripening clusters, remove them from the field preharvest. Do not harvest damaged fruit.

Consider trapping.
Several traps are marketed for wasps. Providing an attractive lure outside your planting may reduce populations in the vineyard. Suggested lures include soda, sugar syrup, and meat. Yellow trap are typically the most attractive.

Check the field for nests.
Wasps in particular can make nests on trellis wires or vines. If there are nests present in fields, these can be spot treated with insecticides or removed. Surrounding areas should also be scouted for nests, which can be spot treated.

Protect yourself.
Wear gloves, and if necessary, a head net when harvesting.

Ripening fruit at Junius Lindsay Vineyard. Photo: HJB

The early season means we need to be prepared for more wasp and bee presence as ripe fruit develops, but this are not unmanageable issues. Happy harvesting!

More information
Harvest pests of grapes - University of Kentucky

What to Watch For - Caterpillars in blueberries

Yellow necked caterpillar damage on a blueberry bush. Photo: HJB

Last fall, I posted about blueberry feeding caterpillars. Several caterpillars species in the genus Datana feed on NC blueberries and are generally called yellow necked caterpillars. More information on this group can be found here. Yesterday, I visited Vollmer Farms near Bunn, NC to discuss organic blackberry management (this is their first year growing blackberries) and took a look at their blueberries as well. There was some light Japanese beetle injury on a few bushes, but one plant was fairly defoliated. A few yellow necked caterpillars were still present on this plant, but most were close to pupation. I did not start getting calls about these insects until September last year, so like many other things this summer, it appears the caterpillars are also earlier than normal.

Yellow necked caterpillar larva on blueberry bush. Photo: HJB

These caterpillars are gregarious, meaning they feed in large groups, often on a single plant. This grouping also means that yellow necked caterpillars can readily defoliate bushes. This time of year, blueberry bushes develop flower buds for next year and severe defoliation could impact fruit set for next year. Fortunately, only one of the bushes at Vollmer's Farm was damaged.

Nearly mature yellow necked caterpillar and young caterpillar. Photo: HJB

If yellow necked caterpillars are observed early on blueberry plantings, they can be easily managed with both conventional and organic materials (a note of on pesticide recommendations). In addition to the caterpillars, we found a surprise, a large female praying mantis. One caterpillar on the bush had clearly been killed by the mantis, but that didn't seem to deter another from tempting fate by climbing onto the same branch she was on.

A brave caterpillar. Photo: HJB

What to watch for in 2010: Thrips

Over the next few weeks (0r until the field season gets busy), I will be posting pest watches for 2010. These are designed to provide updates on pests that may be problematic or for which management strategies may differ in 2010.

First up is a group that has become near and dear to me in the last 2 years: Thrips!

Western flower thrips (Frankliniella occidentalis), www.bugwood.org. Photo: J.T. Reed

Thrips as pests

Thrips are of concern to southeastern growers for 2 reasons: 1. They vector potentially devastating plant viruses, and 2. Thrips can directly damage crops in their own right. In the cropping systems I work in thrips are both virus vectors (tobacco and caneberries) and cause direct fruit or plant injury (strawberries, blueberries, and grapes).

In tobacco, thrips vector Tomato Spotted Wilt Virus (TSWV) which can result in significant losses. Colleagues in the NC State Entomology Department developed a degree day model which predicts tobacco thrips (Frankliniella fusca, the most important TSWV vector in the southeast) flights. We have adapted these models for a website that will be launched for use by county agents and select growers this Thursday, April 1st.

Flue cured tobacco plant infected with TSWV. Photo: www.bugwood.org.

Thrips also vector Impatiens Necrotic Spot Virus (INSV), which infects many plants, including caneberries. Caneberry viruses are the topic of a multi state USDA Specialty Crops Research Initiative (SCRI) project with which I am involved. Lead by the University of Arkansas, this project is designed to identify and development management strategies for virus complexes in caneberries. Unlike many other plant-virus pathosystems, caneberries are often infected with 2 to 3 virus before they show symptoms. The virus complex appears to vary regionally, as do the likely vectors.

Blueberry fruit damage caused by thrips oviposition (egg laying) and feeding. Photo: Insect Management in Blueberries in the Eastern United States, Tuner & Liburd.

In strawberries, grapes, and blueberries, fruit injury by thrips is of greatest concern. Thrips feeding on blueberry can also damage blooms. Blueberry injury by thrips is weather and variety dependant in NC. Late blooming varieties (rabbiteye and northern highbush) are more prone to damage, but growers generally do not need to treat these varieties every year. Thrips injury to strawberries is rare in NC, and other injury is often misdiagnosed as thrips-caused.

Thrips can cause bronzing near the calyx in strawberries. Photo: Jack Kelly Clark, UC IPM Program.

Thrips do not cause malformed fruit. The damage in this image is due to lygus bug injury, but malformed fruit can also be caused be poor pollination or dried calyx disorder. Lygus bug injury is also rare in NC and has only been observed on late season or day neutral strawberries. Photo: UC IPM Program.

Thrips injury to grapes is more common in NC than injury to blueberries and strawberries. Grapes bloom and develop later in the spring, when thrips populations have built to higher numbers and are less susceptible to spring weather conditions.

What to watch in 2010

Thrips management in 2010 will be different than in a typically year, because we will likely have fewer thrips than normal and they may move into crops later. If this holds true, we may have fewer problems with thrips in tobacco and small fruits in 2010 than in a typical year.

Tobacco thrips models currently indicate that this spring will have low numbers of thrips. This is not surprising because cool, wet weather negatively impacts thrips during March and early April. This spring, much like last year, has been both cool and wet, until recently. It is possible that weather patterns could become more favorable for thrips, but unless the weather changes dramatically (rapidly warming and drying), I suspect that thrips movements will occur later this year and that populations will be lower than normal.

What does this mean practically? I anticipate that thrips treatments in blueberries may not be needed, and that strawberry injury may also be rare. As always, SCOUT and SAMPLE before making any treatment decision!

We continue to track and model tobacco thrips populations, and we will not have concrete predictions until the end of April, but I will continue to update as this picture becomes clearer.