Whiteflies in blueberries - should we be concerned?

I'm attending the North American Blueberry Research and Extension Workers Conference in Kalamazoo, MI today and tomorrow, so I thought it would be a good time for a blueberry post.

I have been noticing large numbers of an unusual looking whitefly in blueberries for the last 2 years and now have an ID for it. Tetraleurodes ursorum does not have a common name, although the Florida Department of Agricultural & Consumer Services suggests it be called the bearberry whitefly. These whiteflies usually appear after harvest and are present on new growth. They are unique in their dark blueish black coloring, which almost makes them appear parasitized. Although many of the nymphs and pupae I collected in 2010 were parasitized, the dark color is their natural appearance. Whiteflies have a complex life cycle. Eggs hatch to a mobile 1st instar, termed a crawler. They then mature through a few stationary nymph stages to what is generally called a pupa but is really just a final, non-feeding nymphal instar. Because whiteflies do not undergo complete metamorphosis, the term pupa is a misnomer.

Whitefly nymphs and pupae on the underside of blueberry foliage in 2008. Photos: HJB

These whiteflies can reach extremely high numbers in NC blueberries. I have seen the back of leaves entirely covered in nymphs and pupae and their associated honeydew. Because they appear to be a post harvest feeder, it is unclear if they are causing any damage to the plant. This late summer, I plan to treat some of my new planting for whiteflies (assuming they are present there) and to then compare flower clusters next spring. Hopefully this will starting giving us a sense of what, if any, importance this unusual insect has for NC blueberries.

Whitefly adults on young blueberry foliage. Photo: HJB

Mystery holes on tobacco stalks

Tobacco stalk with holes.  Photo: Norman Harrell.

Wilson County field crops agent, Norman Harrell, sent me an email with the above picture attached.  A grower brought in the tobacco stalk concerned about what could be causing the holes.  I see this type of damage every year around this time, and it is not of economic concern.  Although any chewing insect (ie. crickets, beetles, grasshoppers) could potentially cause this type of injury, it's most likely due to either tobacco budworms or tobacco/tomato hornworms.  While these caterpillars typically feed on leaf tissue, they may occasionally take a bite out of the stalk.  Stalk injury like this does not impact the plant, and does not suggest that further damage is likely (unless hornworms are found when scouting).  The threshold for hornworms in tobacco is 1 inch-long or larger hornworm per 10 plants with parasitized hornworms counting as 1/5 of a worm because they eat approximately 1/5 of that of a healthy caterpillar.

Bottom line, however, is that stalk damage of this type may be caused by several insects, but is nothing to worry about!

First strawberry preplant meeting - July 28th

The first strawberry preplant meeting of the season (is it that time already?!) will be next Thursday, July 28th at the Mountain Horticultural Research Station in Mills River, NC.  Area horticulture agent, Sue Colucci has organized this meeting, and interested growers can find more details here.  I will be sharing results from our 2010 twospotted spider mite trials, discussing new insecticide options and IPM strategies for sap beetles in strawberries, and sharing information on unusual caterpillar issues from this year's harvest season.
Hope to see the mountain strawberry growers there!


Update
Sue Colucci has just posted an announcement for the meeting on her blog, Western NC Vegetable and Small Fruits News.

Tobacco Tour 2010 completed - pictures to come!

The 2010 Tobacco Tour proceeded this week Tuesday and Wednesday and visited 10 locations encompassing 20 Crop Sciences, Plant Pathology, Bio & Ag Engineering, and Entomology extension and research projects.  Over 120 people attended the eastern tour on Tuesday, and 50 people participated in the western tour Wednesday.  I, and Monique Rivera, took lots of great pictures, which I will post soon!

Grape phylloxera update

Grape phylloxera adults and eggs in foliar galls at RayLen Vineyard. Photo: HJB

Last Thursday I visited RayLen Vineyard to see the grape phylloxera (Daktulosphaira vitifoliae) infestation I posted about previously.  In person, the extent of the damage was even more impressive.  The Vidal Blanc vines were nearly completely infested.  This suggests that several generations have cycled through during this summer.  Vidal is a French-American hybrid grape.  Hybrids (ie. Traminette, Seyval Blanc, Chambourcin) are increasing in popularity among eastern grape growers because they are often more tolerant of our weather conditions that European varietals (ie. Merlot, Chardonnay, Cabernet Sauvignon).  However, it appears that some of these hybrids are more susceptible to foliar phylloxera.  Because they are grown on phylloxera tolerant rootstock, it is unlikely that phylloxera are also damaging roots.

Infested Vidal vines. Photo: HJB

Leaves at the base of the canes had no live phylloxera present.  I started to find live phylloxera about half way up the canes, and the youngest leaves had females and eggs in the galls as well as few crawlers.  

Mature grape phylloxera female and eggs (indicated by red arrow) and crawler (blue arrow) on a young grape leaf.  Photo: HJB

Donn Johnson, University of Arkansas small fruit entomologist, has posted several other images of eggs, crawlers and adults here.  The leaves with active infestations were near the end of canes and likely to be removed during hedging (which was planned for the next few days after my visit to RayLen), and because of this, I was reluctant to recommend a pesticide application.  Instead, I suggested removing as many infested leaves as possible during hedging/leaf removal and destroying them.  They could then follow this up with a pesticide treatment if crawlers or open galls (see below) were still present.  

Open galls on young leaves.  The insects in these galls are susceptible to contact insecticides.  Photo: HJB

It seems likely that phylloxera will continue to be a problem in French-American hybird grapes, which I am still a fan of for their many other good qualities.  The strategy at RayLen and other infested vineyards should include early season scouting for first generation phylloxera--likely to be a few galls near the base of cane in spring.  Once crawlers of this first generation appear, foliar treatments should be applied (some of the materials available for phylloxera management are listed in this University of Arkansas fact sheet). Regular scouting for subsequent generations should be conducted throughout the summer followed by treatment as they appear.  Severe phylloxera infestations weaken vines and leave them more susceptible to winter injury.

Phylloxera infested cane.  Photo: HJB

Watching the west: SWD organic trial results

Mark Bolda, University of California Cooperative Extension Farm Advisor in Santa Cruz County, has posted the results of a recent efficacy trial comparing organic management tools for SWD. According to this post, Pyganic and Entrust appeared to provide control of SWD in raspberries. Both of these materials are OMRI listed (organically acceptable).

More information
Results of Trial Testing the Efficacy of Several Organically Registered Pesticides for Control of Spotted Wing Drosophila in Raspberry

Hornworms in motion (not a pest alert!)

Those of us who work on and grow the crops they eat may think of tobacco hornworms (Manduca sexta) as pests to be controlled, but they are also import lab rats for all sorts of biological research. In fact, my undergraduate research studied hormone binding and transport in M. sexta in response to environmental stresses, so I have dealt with my fair share of hornworms in and out of the lab.

A recent study used hornworms as a model of locomotion and found that their gut and body move separately! See here for a nice summary and cool video!

ScienceShot: Caterpillar's Guts Crawl Independently of Their Bodies

SWD article in Growing Magazine

OSU Entomologist Amy Dreves checks a monitoring trap in an Oregon strawberry grower’s high tunnel crop for SWD.
Photo by Lynn Ketchum, OSU EESC.

An article highlighting SWD motoring and management efforts throughout the US has just been published in Growing, a magazine for fruit and vegetable growers. Our monitoring effort is highlighted. When the article was written, there were no SWD captures in SC, NC, or VA. What a difference a few weeks make! We now have trap captures in 2 locations (see trapping data here). More on these captures later this week.

Northern Fruit Growers on Watch

Grape root borer update

I visited 2 vineyards on Thursday, July 15th to discuss grape root borer presence and management. We hung 6 traps at RayLen Vineyard, which they will begin checking this week. I next headed up to RagApple Lassie, where owner Frank Hobson reported catching significant numbers of grape root borer moths in his 3 monitoring traps. After loaning one of his traps to a neighboring vineyard, they reported 60+ moths in a few days.

The growers I visited raised several great questions about grape root borer (GRB) that bear reviewing:

1. Why are we seeing this many moths now?

RagApple Lassie began trapping for moths this year in response to damage seen last year. Several vines were declining, and when they were dug up, GRB damage and larvae were present. This was the first GRB damage they recall seeing. It is hard to say why exactly multiple vineyards are seeing significant numbers of GRB, but I suspect that it at least partially due to weather and vineyard age. Last year was the first summer in 3 years with relatively normal precipitation, and soil dwelling insects are often sensitive to moisture--declining in years with low moisture and rebounding following years with moisture.

We also have several "middle age" vineyards in the Yadkin Valley. GRB take up to 2 years complete a generation, so it may take several (8-10 years) for moths to develop to detectable levels. We have several vineyards at or just older than this age.

2. How do we use control tools for GRB?

Lorsban (chlorpyrifos) is the only material registered for GRB, but as I mentioned in my previous post, this material is hard to time given the long GRB emergence time which coincides with harvest.

Soil mounding at the base of vines at the beginning of July is a cultural control option, but I have seem limited efficacy data on this tool.

3. Are there any non chemical options for GRB?

Soil mounding is a non chemical option. Other non chemical options that have been tested include entomopathenogenic nematodoes and pheromone mediated mating disruption. University of Florida researchers have demonstrated good results with mating disruption, but neither of these tools are commercially available at this time. These are both interesting options that bear examination under NC conditions.

New blueberry maggot trap captures in southeastern NC

Blueberry maggot flies were captured at our southeastern monitoring sites on July 14th. One male each were trapped at Site 2 and Site 12 (you cannot see Site 2 in the figure below). Both locations still have a considerable amount of fruit left to harvest. Southern highbush fruit have long been harvested, but rabbiteye berries remain on the bushes.

Blueberry maggot captures in southeastern monitoring locations.

Prior to this, only 1 blueberry maggot fly was captured at Site 5 (in Bladen County). All 3 locations where flies have been captured are treating aerially with malathion (the grower standard for BBM management in the Calendar spray program), while no flies have been captured at either of our 2 untreated locations (Sites 3 and 14). At our monitoring location outside of the commercial blueberry production region in Rockingham County, we caught 33 flies on July 14th. Our Rockingham County location is also not treated.

Because our last southeastern trap capture was a month ago, this begs the questions as to whether the flies we are observing now are part of the same emerging cohort of adults or if they are newly emerged, and therefore, targeting rabbiteye fruit. Either of these are possible, as many tephritid fruit flies can be fairly long lived (a one month life span would not be unheard of). Unfortunately, we cannot say how the old the flies we captured were because they were male. The ovaries of female flies can be dissected to roughly determine if flies are very young or relatively old, but there are not reliable tools or aging male flies. We'll be keeping an eye out for female flies to shed some light on this trapping pattern.

Live updated southeastern blueberry maggot captures

SWD trap captures now available

Our spotted wing drosophila monitoring locations have been trapping since May in most cases, and now our trapping data is available online. The links below lead to a figure for each site, which are updated as new data are entered. Right now, these figures all look the same since SWD trap captures have been 0 for each site until recently. Two of our locations, one in SC and one in NC have detected SWD, but these data have not yet been entered in the online database. Look for post early this week with the details of these trap captures. I will also be posting a map with links to these locations early next week.

For ease of display, dates are converted into ordinal dates (the number of the date in the year). See here to convert an ordinal date back to a calendar date. If a figure says "no data", this means that trap captures from that site have not yet been entered, not necessarily that there is no data at this time.

Monitoring locations by state (in order from East to West):

South Carolina Locations

Charleston County, SC

Barnwell County, SC

Lexington County, SC. Site 2

Lexington County, SC. Site 1

Saluda County, SC

Spartanburg County, SC

North Carolina Locations

Brunswick County, NC

Edgecombe County, NC

Wanye County, NC

Johnston County, NC
Lee County, NC

Montgomery County, NC

Randolph County, NC, Site 2

Randolph County, NC. Site 1

Davidson County, NC

Gaston County, NC

Cleveland County, NC

Alexander County, NC

Wilkes County, NC

Henderson County, NC. Site 1
Henderson County, NC. Site 2 (This site was established by Dr. Jim Walgenbach at the Mountain Horticultural Research Station on 9 September 2010 in response to nearby trap captures and resulted in immediate detection.)

Virginia Locations

Frederick County, VA. Site 1

Frederick County, VA. Site 2

Montgomery County, VA

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

Reminders!

Our second SWD webinar is tomorrow at 2pm. See here for details and email Hannah for more information.

The NC State Tobacco Tour is July 19-21. Find the schedule and register here. Registration closes Friday!

Grape root borer captures in NC vineyards

Mating pair of grape root borer moths (female, left; male, right).  Photo: H C Ellis, University of Georgia, Bugwood.org

Two North Carolina vineyards have reported grape root borer (Vitacea polistiformis) trap captures in the last week.  Both vineyards are in the Yadkin Valley, where many of our wine grape growers are located.  If these places are capturing moths, they are likely active in other vineyards in the area.  Many wine grape growers do not monitor for grape root borer, so we do not have a good sense of how wide spread they are NC, but they are capable of infesting grapes throughout the state (both bunch/wine grapes and muscadines) and occur throughout the eastern US, from Florida through Ohio.

Grape root borer injury.  Photo: James Solomon, USDA Forest Service, Bugwood.org

Grape root borer larva.  Photo: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

Grape root borers are potential devastating pests.  As their name suggests, the larvae of grape root borers feed on the roots and crowns of vines.  Like related species (ie. raspberry crown borer), larvae may live for 1-2 years, longer in northern latitudes, and shorter in southern.  According to Tennessee entomologists, larvae there take 22 months to develop on average.  This same Tennessee factsheet has a great overview of grape root borer biology.  Briefly, egg laying begins about 8 days after emergence, and the eggs take 14 days to hatch.  Eggs are laid at the soil surface.  These newly hatched larvae are the most easily controlled life stage, and chemical treatments (if used) are targeted to them.  Once the larvae enter the roots, they are very difficult to control.  Adult control is also impractical, because the moths do not feed on grapes and therefore would not contact insecticides applied the crop.  Adult moths emerge and lay eggs over a relatively long period of time as well, further complicating management. 

Much of this difficulty arises from the materials registered against grape root borer.  Only one conventional insecticide, Lorsban (chlorpyrifos) is registered.  Lorsban has a long pre harvest interval in grapes (35 days in bunch grapes).  Because moths may continue to emerge until fall, this application timing may be too early in some cases.  Ideally, a material which could be timed to moth trap captures would be more useful.  Identifying an alternative to Lorsban with a shorter PHI is a high priority IR-4 project, but the long life cycle of this pest slows this process.  Non chemical management tools are also available.  Entomopathogenic nematodes and pheromone-based mating disruption (essentially confusing male moths) have shown promise experimentally, but neither have been brought up to commerical scale.  Cultural control by soil mounding (in early July or the start of moth emergence, whichever comes first), can also reduce moth numbers.  Soil mounded around the base of vines creates a longer distance for emerging moths to travel, and they die before reaching the surface.  See the Southern Regional Small Fruit Consortium's Bunch Grape IPM Guide for specifics on treatment options.

Monitoring

Pheromone lures attractive to male moths can be used to detect adults, and these are traps growers have caught moths in this year.  Several trap types can be used in combination with these lures (typically rubber septa impregnated with pheromones), but the easiest to use is probably the bucket trap.  These traps are available from several suppliers (some are listed below).

 

Grape root borer monitoring trap.  Traps are baited with a pheromone lure attractive to Photo: Insect pests of grapes in Florida

Although the grape root borer pheromone is relatively specific, one related species can also be attracted to the traps.  The squash vine borer (Melittia cucurbitae, below) is easily distinguished from grape root borer.

Squash vine borer adult are orange rather than yellow/brown like grape root borers and have more bristles on their rear legs.  See here for another useful image.  Photo: Purdue University Cooperative Extension

In addition to traps, which attract male moths, growers should also scout for pupal cases under the vines.  This will provide a better sense of the total moths present in the vineyard, as traps may pull males in from nearby plantings or wild grapes.  Other states have used pupal case counts to develop treatment thresholds.  Kentucky entomologists recommend treating when 5% of vines have pupal cases present.  Thresholds are an important component of an IPM program, because there are consequences (economic, environmental, etc.) to each management decision, and unnecessary treatments should not be made.

Trap sources

Great Lakes IPM

Trece, Inc.

Gempler's

ARBICO Organics 

Grape phylloxera in NC vineyards

Vidal Blanc grape leaves heavily infested with the foliar form of grape phylloxera at RayLen Vineyards, Mocksville, NC.  Photo: Turner Sutton

This Wednesday, I received an email from Steve Shepard, vintner at RayLen Vineyards, describing a large infestation of the foliar form of grape phylloxera in his Vidal Blanc block.  Vidal Blanc (or just Vidal) is a French hybrid grape widely planted in the eastern US because of its cold tolerance.  I made plans to visit the vineyard next week and was not too concerned about the potential for damage.  Then I received an email from Turner Sutton, NC State plant pathologist, who sent me a photo of the damage (above).

Grape phylloxera (Daktulosphaira vitifoliae) is an aphid like insect which can feed on both leaves and roots of grape vines. Foliar infestations of grape phylloxera are fairly common in NC, but they are usually limited to a few galled leaves and do not impact photosynthesis.  If only a few galls are present, removing the affected leaves before the galls spread can limit an infestation.  In fact, phylloxera was of so little concern last year that we did not address its management in the Southern Region Small Fruit Consortium Bunch Grape IPM Guide. We are meeting to edit this guide in 3 weeks, and adding phylloxera will on the top of my list of changes.  The root feeding form of phylloxera has received most of the attention as a pest because of its potential damage to western US grape plantings and its history as an invasive species in France.  Native North American grapes are naturally tolerant to root feeding by phylloxera, but native French varieties were not.  The use of American root stocks grafted to French varieties (developed by pioneering American entomologist Charles Valentine Riley) is credited with saving the French wine industry.

Foliar phylloxera has become increasingly common in recent years, and infestations as severe as the one at RayLen can reduce photosynthesis therefore decrease fruit quality and vine vigor.   French-American hybrid grapes are being planted more frequently in the eastern US because of their tolerance to varying climatic conditions, but many of these varieties appear more susceptible to foliar phylloxera.  The grape phylloxera life cycle is very complicated, but the stage most amenable to management are the crawlers, which move on the plant surface to found new galls.  Not all the galls on the leaves in Turner's photo necessarily contain live phylloxera, as the galls will remain after the insects have moved on.

Comparatively little work has been done on foliar phylloxera, but Dr. Donn Johnson at the University of Arkansas has put together an excellent fact sheet on phylloxera biology and management.  Dr. Johnson also works with Missouri wine growers, who have been dealing with damaging foliar phylloxera infestations for several years.

More information
Biology and management of grape phylloxera - Johnson, Sleezer, and Lewis

Floating Sheep tackles tobacco again

 Floating Sheep, a geography blog which I have posted on before, has another series of maps related to tobacco.  This time they are comparing crop production and consumption using Google Maps.  In a post here, Matthew Zook, an associate professor of geography at the University of Kentucky, compares mentioned of several crops over geographic areas.  In the US map above, there's a clear tobacco (purple) cluster in the southeast, although tobacco shows up in keyword searches nationwide.  This map is similar to their "minor vice" map, which compared alcohol, caffeine, and tobacco references in the US and worldwide.

Blackberry borers can mean big problems

Weakened blackberry plants, Guilford County, NC. Photo: Gina Fernandez

NC State caneberry specialist, Gina Fernandez has just returned from sabbatical and has wasted no time getting out for field visits. Yesterday, she brought me several samples from blackberry fields in Guilford County that were in severe decline. Their problems were almost all insect related. There were more cane boring pests from these few sites than I have seen my entire time at NC State! I'd like to use these samples as an overview of the key cane boring insects in NC, what symptoms to look for, and what the management strategies for these pests should entail.

Evidence of borer damage is often visible from a distance. Plants will appear weakened, and in the case of raspberry crown borer, floricanes will be loose and easily removed. There are 3 key cane boring insects in North Carolina, and these locations had all of them!

Rednecked cane borer
The rednecked cane borer (Agrilus ruficollis) is part of a family of beetles known as metallic wood boring beetles. The adults lay their eggs on the surface of primocanes and the larvae bore into them. When used, insecticide treatments target the adults, since the larvae do not spend time outside the plant. Larval rednecked cane borer feeding produces galls on the canes. The larvae are flat and found within the cane. As they grow, larvae will tunnel above the gall and reduce plant vigor and yield.

Rednecked cane borer galls (top), larva in gall (middle) and outside of gall (bottom). Photos: Gina Fernandez (top), HJB (middle, bottom).

Low levels of rednecked cane borers can be managed with cultural control, specifically by removing and destroying all infested canes during the fall. The larvae overwinter inside the cane, so pruning will remove next year's generation of adults. For large infestations, chemical control of the adults may be necessary (see the Southern Region IPM Guide for chemical information). Dr. Donn Johnson, University of Arkansas fruit entomologist, has also had success removing primocanes in the early summer after the adult beetles laid their eggs (a June removal date worked the best in Arkansas and did not impact fruiting). This strategy may work well in North Carolina, because our long growing season allows plenty of time for primocane regrowth.

Raspberry cane borer

Raspberry cane borers (Oberea bimaculata), members of a family known as long horned beetles due their prominent antennae, were also present in the Guidford County plantings. The adult beetles create paired girdles at primocane tips in summer. These tips wilt and will eventually fall off, and the entire cane may die. Larvae tunnel downward from the tip and have a 1-2 year life cycle in the southeast.

Raspberry cane borer girdling. Photo: Gina Fernandez

Cultural control, via pruning, is also an effective means of managing raspberry caneborers. Insecticide treatments may be targeted to the emerging and ovipositing (egg laying) adults just after bloom in cases where large infestation exist.

Raspberry crown borer

Raspberry crown borer (Pennisetia marginata) is perhaps the most severe pest of caneberries in the southeast. The larvae of this clearwing moth feed on the roots and crowns of caneberry plants and can kill an entire plant. Because they spend most of their 1-2 year larval stage underground, they are extremely hard to manage. Work conducted in Arkansas demonstrated that late fall or early spring soil drench pesticide treatments are most effective at reducing raspberry crown borers. These timed treatments target the early instar larvae before they are ensconced in the crown. Insecticides are, at this time, the most effective means of raspberry crown borer management. Infested plants should be completely removed, since mature larvae will not be impacted by pesticide treatments.

Raspberry crown borer damage (t0p) and larvae in a blackberry cane (bottom). Photos: Gina Fernandez (top), HJB (bottom)

In addition to the damage caused by these 3 wood boring insects, there were also several canes with damage at the tip that were dying back.

Unidentified damage at cane tips and associated tunnels. Photos: Gina Fernandez

It is possible that this damage was cause by raspberry cane borers, but no larvae were found in the canes, and what tunnels there were stopped several inches from the top. If this was raspberry cane borer injury, we would expect to see tunnels continuing to the soil level or larvae present. These canes may have been injured during tipping and then feed on be opportunistic secondary pests. I dissected one of these canes, and there was fungal growth in the gallery, although this may also be secondary.

Fungal growth in damaged cane. Photo: HJB

Wood boring insects are a fact of life for caneberry growers and can easily get out of control if a planting is not managed carefully. There are abundant feral and wild brambles in the landscape, which serve as hosts for all three of these insects. Carefully scouting, good cultural management, and insecticide treatment when needed will keep borers from destroying caneberry plantings.

More information
Rednecked cane borer - Virginia Tech
Rednecked and raspberry cane borers - University of Kentucky
Blackberry Insect Pest Management - Presentation from Donn Johnson, University of Arkansas

NC vineyard profile

Raffaldini Vineyards & wine maker Stephen Rigby are profiled at Architects & Artisans in two stories. One on the vineyard, and one on wine making. They're worth a look.

IPM funding at risk

I have delayed weighing in on the developing Farm Bill because I share the views, more eloquently put, of many other organizations, including:
The Entomological Society of America
The Southern Region IPM Center
The Farm Press

However, I think it's time to add my voice to chorus in support of the restoration of the "406 Programs" to the 2011 Farm Bill. These programs not only support direct research on important agricultural issues (Program areas: Methyl Bromide Alternatives, Crops at Risk, and Risk Avoidance and Mitigation, among others), these are also the funds the support our state and regional IPM centers. These centers (North Central, Northeastern, Western, and Southern) are catalysts for IPM research, implementation, and practice and are essential to the work I do.

The House Agricultural Appropriations Committee has left funding out for CAR, RAMP, and regional IPM centers, but has resorted some of the 406 programs (MBT, Food Safety, and Water Quality). The loss of the regional IPM centers in particular would be devastating for applied agriculture research and extension in North Carolina. If you feel strongly about this type of research, now is the time to contact your representative and let them know that you support the mission of the 406 programs.

The NC House of Representatives Members can be found here.

Vineyard heat and drought stress alert

Developing grapes at Westbend Vineyards, Lewisville, NC. Photo: HJB

Dr. Sara Spayd, professor of viticulture in the NC State Horticulture Department, is warning of heat and drought stress in NC vineyards. The record heat this week has the potential to impact not only people but plants as well. See here to read Dr. Spayd's complete alert.

Right now, fruit quality and yield is of primary concern, but heat and drought stress can also have implications for insect management. Numerous wood boring beetles can attack grape vines in NC. Most wood boring beetles will not kill an infested vine outright and are rather a symptom of a larger problem weakening the plant. Drought stress is often the initial problem responsible for weakening vines.

In fall 2007, I visited a small vineyard that was planted in half Chardonnay and half Merlot. The Chardonnay vines were small but generally healthy. The Merlot vines, however, were virtually all dead or dying and riddled with several species of wood boring beetles.

Merlot vines and canes with extensive wood boring beetle damage (indicated by arrows). These perfectly round holes are adult beetle exit holes. Some larvae were still present in these vines as well. Photo: HJB

Wood boring beetle larvae collected from Merlot vines. The lower larva is likely that of a long horned beetle (Coleoptera: Cerambycidae) and the insects in the upper image are likely shot hole borer larvae (Coleoptera: Scolytidae). Photo: HJB

According to Dr. Spayd, Merlot is often the "canary in the coal mine" for drought stress. At this vineyard, neither variety had been irrigated the preceding summer, but the Chardonnay vines tolerated the stress better. Numerous beetles were attracted to the stressed Merlot vines and were the final straw that pushed them over the edge. Water is an important part of woody plants defenses against boring beetles. If there are only a few larvae in a tree or vine, the plant will use sap to flood them out. Water stressed plants are no longer able to mount this defense and can be taken over by beetles.

Cultural control is the best method of wood boring beetle management. Healthy vines will seldom host damage beetle populations. Any tissue that is infested with beetle should be removed during winter pruning and destroyed. If cuttings are left in the vineyard, beetles may be able to complete their development and re-infest vines the following spring. Chemical control is recommended. Chemicals will not effectively treat larvae inside vines, and targeting adults is difficult due to their high mobility and the large number of species potentially present.

One beetle is an exception to the rule in that it will attack healthy vines as well as weak vines. The granulated (formerly Asian) ambrosia beetle can potentially damage healthy vines. Granulated ambrosia beetle is a serious problem in nursery production, but does not appear to be widespread in NC vineyards at this time.

More information
Vineyard Alert: Extreme Heat and Droughty Conditions Affecting NC Vines
Granulated ambrosia beetle in NC

Blackberry psyllid at the Sandhills - a little known pest

Blackberry primocanes infested with blackberry psyllid nymphs. The shortened internodes and tightly curled leaves are indicative of blackberry psyllid. Photo: HJB

My blackberry research plots are at the Sandhills Research Station, which is a great place to work for a number of reasons. One these reasons is this the Sandhills have unique pest pressures not easily found elsewhere. Blackberry psyllid (Trioza tripunctata) is one of these pests. Blackberry psyllid adults are small, cicada-like insects, and the nymphs are small and wingless. Both life stages feed on phloem and damage plants. Blackberry psyllids are tightly associated with their overwintering host, pine trees, and because of this, their distribution is closely tied to proximity to conifers. Although there is very little literature on blackberry psyllid, the sources that are available suggest that plantings within 1/8 mile of conifers are at the greatest risk of psyllid damage while those further than a mile from conifers rarely have blackberry psyllid damage.

Life cycle

Adult blackberry psyllids over winter in conifers and move to caneberries in spring (probably April in North Carolina) where they lay eggs. The adults will remain in blackberries for several days, and the characteristic leaf curling will develop after about a week. Very low psyllid numbers can produce this injury. Nymphs will develop on the undersides of leaves, progress through 5 instars, and move into their overwintering host in the fall. Blackberry psyllids likely have only 1 generation in the southeast.

Damage

Adult psyllid feeding produces curled leaves and shortened internodes, and at the Sandhills, this damage is mostly on primocanes. This suggests that adults may have moved into plantings later than April, unlike the current available sources suggest. Some canes are affected from the tip down, while others appear to be damaged on the underside of the cane, causing it to curl downward. The nymphs feed from the underside of the leaf and produce wax structures.

The underside of a damaged blackberry leaf with developing psyllid nymphs. Photo: HJB

Blackberry psyllid nymph. The large wax strands are produced by the larvae. Photo: HJB

Curled leaves also provide refuge for other arthropods. I have found spider mites, predatory mites, thrips, and spiders in these leaves so far this season. Spider mites and thrips are potential plant pests, but predatory mites and spiders are beneficial, so these refugia may provide some benefit to the plant.

Spider mite found on blackberry psyllid damaged leaf. Photo: HJB

Management

Cultural control, in the form of site selection, is the most important management strategy for blackberry psyllid in the southeast. The infrequency of blackberry psyllid damage in commercial blackberry production is likely due to distance from conifers.

For locations where psyllid is a problem, we are investigating management strategies this summer, first looking at systemic insecticides that are effective against other psyllids. I treated several plots with imidacloprid on June 22 and will be collected 2 week after treatment samples this Saturday.

SWD Webinar 2 Scheduled

National Agricultural Pest Information System map of SWD trap captures. Click to enlarge. Source: NAPIS

The second of 2 webinars for volunteer SWD trappers has been scheduled for July 14th at 2pm. Contact Hannah if you would like more information on this training session.

SWD male. Source: UCIPM

Those interested in SWD who are not currently trapping (especially county agents and other "first responders") are welcome to attend. You will need the webinar address and password, which I will send you upon request.



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

Once in a blue moon

It's been a hectic (and productive) field season, but being this busy means that lab members are rarely in the same place at once. So, imagine my surprise this afternoon when everyone was in the lab working at the same time! Shelley, M.S. student studying blueberry pollination ecology; Monique, M.S. student studying tobacco splitworm larval biology; and Richard Reeves, Ph.D. student revising tobacco treatment thresholds were all setting up various experiments.

Shelley was measuring and weighing blueberries from pollination efficiency locations. Monique was assessing no-choice feeding assays, and Richard was setting up a bioassay.

This lab togetherness won't last for long; tomorrow all of us are back out in the field. But I had to snap a picture with everyone working!

NC Tobacco Tour July 19-21st

Field sites on the 2007 Tobacco Tour. This was my first official event as a new NCSU faculty member--before my official start date of Sept. 1, 2007. Photo: HJB

The NC Tobacco Tour will take place July 19-21. The Eastern NC Tour will begin with a sponsored dinner on July 19th in New Bern, NC and continue to field sites on July 20th. Our program will be presenting projects on thrips flight prediction, tobacco splitworm ecology (Monique's project), and new insecticides & threshold revisions (Richard's projects).

Our Stokes County trial location, after transplant. Photo: HJB

The Western NC Tour will take place on July 21st, and we will be visiting a lepidopteran management trial in Stokes County.

You can find all the tour details here.

NCSU Tobacco Tour Information

Southern Region Small Fruit Consortium Newsletter

The latest edition of the Southern Region Small Fruit Consortium Newsletter has been posted. In this quarter's issue is a summary of 2010 SRSFC funded projects, strawberry & muscadine updates, and a recap of the Small Fruits Field Day adapted from my post.

Our lab was fortunate to have 2 projects funded by the SRSFC this year. Our blueberry pollination work is supported by a research grant and the spotted wing drosophila monitoring network is supported by extension funds. We greatly appreciate SRSFC's support of these projects!

SRSFC Newslettter. v. 10(3).