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Tuesday, June 28, 2011

NC Cooperative Extension on You Tube - Extension is...

NC Cooperative Extension has posted several videos on their YouTube channel addressing the theme "Extension is..." in three words. My favorite video so far is from Randolph County where extension is "doing applied research", including studying the seasonal biology of spotted wing drosophila (SWD) as part of the SWD volunteer monitoring network.

More information

Saturday, June 25, 2011

What does the "Dirty Dozen" mean for IPM?

The Environmental Working Group's (EWG) annual "Dirty Dozen" list of the produce most likely to contain pesticide residues has been released.  As it has in past years, the list contains several fruits, including apples (1), strawberries (3), peaches (4), imported nectarines (6), imported grapes (7), and blueberries (10).

The Dirty Dozen list often receives significant media attention, and most balanced articles typically point out that pesticide residues measured and regulated by the Environmental Protection Agency and that fruits and vegetables are important part of our diet which should not be eliminated or reduced because of pesticide concerns.

Pesticides, as their name makes clear, are used to manage (kill) crop pests, but the meaning of lists like the Dirty Dozen in the context of pest management is rarely, if ever, discussed.  To understand what the Dirty Dozen might mean for integrated pest management (IPM), it's important to understand what is meant by the pesticide use and pesticide residues.

Methods for measuring pesticides
The EWG used several factors when considering pesticide usage on crops.  These included the percentage of samples testing positive for any pesticide residue, the percentage of samples with more than one pesticide residue, the average number & quantity (ppm) of pesticide residues, and the maximum & total number of pesticides found in samples.   Data compared were from routine United States Department of Agriculture (USDA) testing.  Residues measured are of materials registered for use on the crops, and residues of registered materials are regulated by EPA.  In other words, legally allowable residues of pesticides registered and legally used on crops were measured, and these legally allowable residues have been determined by EPA to be safe.

The Dirty Dozen & IPM
While the number of pesticide residues present can certainly be an indication of heavy pesticide usage, it may also be related to a sound pesticide rotation as part of a resistance management program. It is actually worse for the environment and the farmer to use a single pesticide against all pests for two reasons:
1. Pesticides that are effective against many pests are called "broad spectrum" and are also often toxic to non target and beneficial organisms. In other words, broad spectrum materials can kill things we don't want to kill. When narrower spectrum or species specific pesticides are available, these are a better choice.
2. A single pesticide used against a species that has more than one generations per growing season (like SWD)

For these reasons, samples with more than one pesticide residue or relatively large numbers of different pesticides present are not necessarily troubling in the context of IPM.

Where I think IPM practitioners can learn from lists like the Dirty Dozen, however, is with respect to residue quantity and maximum residue levels.  It is important to stress, again, that the materials detected are legally registered and used on fruits and vegetables.  Produce with detectable levels of unregistered pesticides would not be allowed to be sold.

However, my goal as an applied entomologist is to develop integrated insect management strategies, of which pesticides may one, but not the only, tool.   Fruit crops where relatively high levels of pesticides are detected suggest that few non pesticide options exist.  This is a challenge and an opportunity for applied research.  This is a call to arms to develop management tools which reduce our reliance on pesticides in strawberries, blueberries, and the rest of the Dirty Dozen.  Just as consumers should not be afraid to eat the produce on this list, growers and scientists should not be afraid of the information it contains and should take this as an opportunity to improve our production systems.

Sound applied research takes time, but one project already underway was highlighted in South Carolina at an agent-training tour I participated in.  Spearheaded by Dr. Natalia Peres, University of Florida, with cooperators in the Carolinas, this project uses weather data to predict when strawberry fungal disease can infect fruit and only recommends pesticide applications if conditions are right for infection.  In test locations, this has resulted in a significant reduction in pesticide usage when compared to a standard, weekly spray schedule.  This type of pesticide reduction is exciting but is the result of years of previous research.  It is important that the need for meaningful, applied research is not lost in discussions of food choice and food security.

It is important to be conscious in our food choices, but it is just as important to be conscious of the infrastructure needed to support the ability to choose.  The importance of applied agricultural research has not diminished in the current era of budget tightening, but it is being pushed to the edge of priorities. This decreased support directly limits our ability to respond to public concerns like the Dirty Dozen and its list cousins.

Do it yourself - Grape root borer monitoring

Tomorrow, June 26, I will be kicking off the 2011 Grape Root Borer Volunteer Monitoring Network (GRB*VMN) at the NC Winegrowers Association summer picnic. I will be distributing trapping kits to volunteer growers and demonstrating trapping methods. For grape growers interested in monitoring for grape root borer who cannot attend the meeting, this post details how to monitor on your own. If you are interested in participating in the GRP*VMN, please contact me for more information.

The traps I use are available from Great Lakes IPM* and pheromone lures can be purchased from Arbico-Organics*.

Grape root borer (Vitacea polistiformis (Harris)) is potentially the most significant pest of grapes (both muscadine and Vinfera) in the southeast.  Larvae have a 1 to 2 year life cycle, which means that injury, in the form of weakened and dying vines, often does not present for several years.  Many of the Vinfera vineyards in the Carolinas and Georgia are reaching the 8 to 10 year mark, the time at which I anticipate grape root borer injury to become more apparent.

The GRB*VMN has two purposes:
1. To determine the density, range, and seasonal biology of grape root borer in North Carolina.  In other words, to find out how many moths we have in our vineyards, which vineyards they are present in, and at what time of year they are active.
2. To give NC grape growers the skills to monitor for grape root borer and make management decisions based on monitoring information.

To accomplish these goals, we will train grape growers throughout the state to monitor for grape root borer adults on their farms and share their data through this blog.

Monitoring methods
We will place 4 universal moth traps per vineyard.  Ideally, we will place these traps each in a different variety (if present).  Within variety blocks, traps should be placed in low lying, wet areas, since these are at the highest risk of grape root borer infestation.

Grape root borer trap components. From left to right: hanger, trap top, trap lid, pheromone container (front), pheromone impregnated septa (packet, front), pesticide kill strip (red, front), and trap bottom (back).
Traps should be assembled as follows:

Pesticide strips placed in trap bottom.
Pesticide strips are used to kill moths once they enter traps. No pesticide is present outside the traps, and therefore, these traps can be used in organic systems.  Pesticide strips should only be handled with nitrile gloves.

Trap top attached to bottom.

Trap tops snap onto to trap bottoms.
Trap lid added to trap top.
Trap lids keep rain and other debris out of the bottoms.

Grape root borer pheromone impregnated septa.
Grape root borer pheromones are impregnated onto rubber septa and remain attractive for an entire field season.

Pheromone lure placed in pheromone container.
Pheromone lures are placed into lidded containers.

Assembled trap.
The pheromone container is inserted in the trap lid and hangs into the trap opening.  Moths are attracted to pheromone lures and fall into the trap bottom where they are killed by the pesticide strip.  Hangers are attached to trap lids, and traps are hung from canes or trellis wires.

Assembled grape root borer trap
Traps are checked weekly  and moths are counted.  Pheromone lures are attractive at a long distance to male moths, and attractive at a short distance to females, so both sexes may be present in traps.  Grape root borer moths resemble wasps but differ in that their wings are black and they lack the thin "waist" of wasps.  After a few days in the traps, moths may appear darker brown (see below).
Mating male (left) and female (right) grape root borer moths. Photo: University of Kentucky.
Female grape root borer moth one week after collection.
While the grape root borer pheromone is relatively specific, it will attract one related species, the squash vine borer.  However, these moths are bright orange and black and easily distinguished from grape root borer.  Other insects found in traps may include beetles and small brown moths, but these should also be readily distinguishable from grape root borer moths.
Mating male (left) and female (right) squash vine borer moths. Photo: University of Minnesota
Data collected by the GRB*VMN will be entered online weekly and will be shared here, beginning the first week of July.

*Does not imply endorsement of named vendors over other options.

More information
NC Winegrowers Association - Summer Picnic

Thursday, June 16, 2011

SWD ID Guide

I have put together a series of images to assist in spotted wing drosophila (SWD) identification. These images and steps distinguish SWD from the most common similar flies in North & South Carolina and are not intended to be used for SWD identification in other locations. If you have not caught SWD previously, confirm your identification with a cooperative extension agent or entomologist!

More information
SWD ID Guide - Hannah Burrack

Wednesday, June 15, 2011

Do it yourself - Spotted wing drosophila monitoring

As we begin to find spotted wing drosophila (SWD) in more and more locations, growers and homeowners are expressing interest in monitoring for adult flies.  Our volunteer monitoring network uses simple, homemade traps that can be easily adapted for use by others. (Enlarge photos by clicking on them.)  

Trapping supplies include:
Apple cider vinegar (not "flavored")**
1 to 3 quart sized plastic containers with 10 to 12 1/4 inch holes one inch from the top
Unscented dishsoap
Forceps (not shown)
Sieve (not shown)
Solid containers (not shown)
Sorting tray (not shown)
Sample vials (not shown)

Yellow sticky cards (optional)
Cellophane (optional)
Microscope, magnifier, or hand lens (preferred)
**Update, 18 April 2013 - For 2013, we are suggesting that yeast & sugar baits be used instead of apple cider vinegar. Read about how to make and use yeast & sugar lures here.

Many of the trapping supplies can be either be purchased at the grocery store (the deli section will often let you have a few quart sized (32 oz) containers) or through online retailers.  I either use a soldering iron or a 1/4 inch drill bit to punch 12 holes in each trap.  I then string a hanger (nylon cord) through 2 opposite holes.  Yellow sticky cards, forceps, and magnifiers can be purchased from several sources*; I order ours from Great Lakes IPM or BioQuip.

Traps are baited with 1 to 2 inches of apple cider vinegar.

Yellow sticky cards increase the attractiveness of the traps, but also make it more difficult to distinguish female flies from native Drosophila spp.
Because yellow sticky cards improve trap attraction, we are using them at SWD volunteer monitoring network sites where we have not previously caught SWD.  However, because the yellow sticky cards complicate SWD identification & trap processing, we stop using them once SWD is confirmed at a location.

Traps should be hung directly from plants (blueberries, caneberries, grapes, fruit trees, etc.) or placed in the fruit zone of low growing plants (strawberries) near fruit.  SWD prefer shady areas with available moisture, so traps hung in these areas are most likely to catch flies.

This trap was hung from the trellis wire near a heavily fruiting blackberry plant.
Traps should be checked at least weekly.  If using yellow sticky cards, they should be removed, wrapped in cellophane, and marked with the date and trap number.

Sticky cards are only changed if suspected SWD are present or if they are no longer sticky.
A regular kitchen sieve (8 or 10 gage mesh) is small enough to prevent adult SWD from passing through.
Using a 8 to 10 gage mesh sieve (a standard kitchen sieve or sink strainer works well), filter apple cider vinegar into a solid container.

Be sure to line up the holes in the trap with the sieve to avoid spilling vinegar. 
After you have filtered the vinegar, return it to the trap and refill to 1 to 2 inches.  You can reuse the apple cider vinegar but should completely change it at least every 4 weeks.  Used apple cider vinegar should be discarded away from the field so as not to attract flies away from traps.  We are currently studying how long apple cider vinegar and other lures are attractive to SWD, so recommendations on reusing lures may change.

Replace traps after they have been refilled.  
Rinse collected insects off the sieve in to the solid sample container and return them to the office  or lab to process.
The collected insects should be compared to voucher specimens (right) or images of known SWD.
While male SWD are readily distinguishable with little or no magnification, female SWD are more difficult to identify.  Ideally, suspected female SWD (flies that are similar is size, shape, and color to voucher specimens) should be observed under 20x magnification.  The key distinguishing characteristic for female SWD is their large, serrated ovipositor.

The ovipositor of female SWD is large, serrated, and readily distinguished from native Drosophila spp.
Can you spot the male SWD?
Compare suspected SWD to known voucher specimens (available upon request from Hannah).
If you suspect that you have captured SWD adults, check your identification with your cooperative extension agent, extension specialist, the NC Plant Disease & Insect Clinic, or other experts.

Because we are still learning about SWD biology in North America (and the southeast), our current management recommendations are conservative.  I suggest the growers who capture SWD at their farm utilize pesticide treatments (either conventional or organic).  See here for a list of management tools available for North Carolina small fruit growers and their likely efficacy against SWD.  This list is only applicable to North Carolina growers.  If you are outside NC, consult your local cooperative extension agent for registered management tools.  You can find your local cooperative extension office here.

*Does not imply endorsement of named vendors over others.

More information

Tuesday, June 14, 2011

SWD Monitoring Network Featured in the SRIPM Newsletter

The spotted wing drosophila (SWD) volunteer monitoring network is featured in the spring 2011 edition of Southern Exposure, the newsletter of the Southern Region IPM Center. SWD captures continue--today we confirmed flies from Person County, NC and yesterday, we found flies from a site in Onslow County, NC, confirmed a positive trap capture from Anson County, NC, and confirmed the first fly in 2011 from Wayne County, NC. This brings our total of counties where SWD has been identified in North Carolina to 12.

More information
Southern Exposure, Spring 2011

Monday, June 13, 2011

Team Rubus

Those of you that pay attention to the blog roll on the right side of the website may have noticed a new addition last week. Team Rubus is the new online home of the Caneberry Breeding and Small Fruit Extension/Research Program at NCSU, led by Gina Fernandez, Department of Horticulture. Welcome to the blogosphere, Team Rubus!

Gina and I will be attending a blackberry twilight tour this Thursday, June 16th in Henderson County. I will be discussing SWD monitoring & management and other caneberry pests, and Gina will address cultural practices. You can find the details about the tour here.Link
More information
Team Rubus

Sunday, June 12, 2011

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.

Tobacco insect activity increasing

Yesterday, I visited Cross Creek Seed, Inc. in Raeford, NC to check on a research trial we treated last Friday. This trial is comparing Coragen, a newer insecticide from DuPont, applied through drip irrigation to an untreated control for tobacco budworm and tobacco hornworm management. We applied treatments last Friday, and this was our first post treatment count.

Drip applications of Coragen applied to 3 week old tobacco plants. Photo: HJB

It's too early to tell if there are any differences between treatments, but I lots of other noteworthy insects. Several green stink bugs were on plants, but I observed only one damaged leaf.  Stink bugs in tobacco feed on the mid ribs of leaves, sometimes causing the leaf in question to wilt.  Even in very high densities, stink bugs typically only damage one leaf per plant, and this damage is not economically significant.  Wilted leaves may recover or may be more susceptible sun scald and be unharvestable.  The most important consideration with respect to stink bug damage is to distinguish it from potential disease symptoms.  The early stages of several diseases in tobacco may cause wilting.  In order to confirm stink bug damage, stink bugs should be present in the field and damage should be recent (not sun burned).  If stink bugs cannot be confirmed in the field, and other causes of wilting, such as drowning, cannot be ruled out, disease samples should be collected to rule out soil borne pathogens.

Green stink bug present on a tobacco plant, Raeford, NC. Photo: HJB
Tobacco plant with leaf injured by stink bug feeding, Raeford, NC. Photo: HJB
Also moving around the tobacco plants were several snowy tree crickets (Oecanthus fultoni).  Crickets are another infrequent, non economic pest of tobacco.  I didn't see any cricket damage on the plants near Raeford.  When present, cricket injury to tobacco consists of ragged holes on medium to large leaves.

Snowy tree cricket on tobacco plant. Photo: HJB
Also present were fairly large numbers of the insects we are trying to control in this trial, tobacco budworms. Most of the larvae present were small (1st to 3rd larval instars), and adult budworm moths were also flying around.  While tobacco budworms are not necessarily an economically significant pest in tobacco leaf production, they can cause major losses in seed production.  Tobacco budworms preferentially feed on the reproductive parts of plants and can reduce seed set and consume developing seeds.  We have been studying methods to reduce pesticide use against tobacco budworms in seed production. Seed growers typically apply pesticides weekly for tobacco budworm, and we are comparing newer pesticides to reduce foliar application, both in foliar applied and soil forms.

Tobacco budworm (Heliothis virescens) moth present on tobacco plant. Photo: HJB
Last year was a banner year for caterpillars, referred to by some as the "year of the worm".  The 2011 growing season is still young, but signs point to this year being a similarly high pressure caterpillar year.  At Cross Creek, I saw the beginnings of tobacco/tomato hornworm activity--two eggs and one recently hatched larva.  
Tobacco or tomato hornworm eggs in tobacco near  Raeford, NC.  Photo: HJB
Tobacco hornworm larva. Tobacco hornworm larvae have a red caudal (rear) horn, while tomato hornworm larvae have a blue caudal horn. Photo: HJB
Last week, at a field in Harnett County near Lillington, I saw all ages of tobacco budworm larvae and tobacco hornworm larvae.  This is slightly earlier hornworm activity than typical, but it is not out of ordinary.  Growers should scout their fields at least once before topping to ensure that hornworms are not present.  Hornworms are common, but potentially devastating pests in tobacco and shouldn't be taken lightly.

First, second, and third instar tobacco budworm larvae, near Lillington, NC.  Photo: HJB