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Friday, April 29, 2011

Practicing what we preach - Implementing IPM at the Ideal Track

Last February, I planted a research block of blueberries as the Ideal Track, the blueberry research field at the Horticultural Crops Research Station, Castle Hayne, NC, with the intention of setting up various insect management trials. Because Ideal Track is home to the "#1 public blueberry breeding program in the world", as their website proudly proclaims, the station-wide insect management program was necessarily very conservative. Meaning that insecticide sprays were scheduled on a calendar basis, and the entire farm was treated. This practice essentially eliminated populations of fruit feeding insects such as cranberry and cherry fruitworms and blueberry maggot and pathogen vectors such as sharpnosed leafhoppers. While preventative treatment makes sense in the context of a breeding program where every berry might be meaningful, a very conservative insect management program doesn't work well with insect management trials, which by their nature, require some population of insects to manage!

Nor do I recommend a calendar-base spray program to blueberry growers. Instead, I recommend scouting for pests and treating only when potentially damage populations are present. In some cases, like that of sharpnosed leafhopper which can vector pathogens to blueberry plants, very low numbers of insects can be damaging. While other insects, including fruitworms and blueberry maggot, may result in some fruit loss by do not impact overall plant heath and can be tolerated to a certain degree, especially at a research station, where science, not blemish free fruit, is the goal.

Station superintendent Kent Rorem, plant pathologist Bill Cline, and I agreed that insecticide treatments may be necessary for some pests on the station but that we did not have enough information about the biology of these insects to support all the calendar treatments. In order to determine what key blueberry pests are present at Ideal, and therefore what treatments may be needed, I placed several traps throughout the roughly 50 acre planting over the past 3 weeks. Specifically:

13 yellow sticky traps for sharpnosed leafhoppers. Placed on 22 April 2011.

3 cherry fruitworm traps, baited with pheromone lures. Placed 15 April 2011.

3 cranberry fruitworm traps, baited with pheromone lures. Placed 15 April 2011.

All of these traps are checked weekly, and pheromone lures, when used, are changed monthly. We will be using these and other traps placed at the Ideal Track to determine if the traditional calendar pesticide sprays are necessary. As of today, no insecticide applications have been made in 2011. We hope to decrease the up to 6 insecticide applications which have been applied on a preventative basis in previous years. This will be a true win-win-win for my research, the station's pocket book, and the surrounding environment. As Bill Cline said when I first spoke him about this idea, "It's time to start practicing what we preach." I am excited to demonstrate to growers the feasibility of a monitoring based pest management program on the research station.

Monitoring trap countsData from the monitoring traps at the Ideal Track will be available here through the end of the blueberry growing season. Next week (May 2), we will be placing blueberry maggot monitoring traps, and these data will be added to this list. We are also monitoring spotted wing drosophila (SWD) at Ideal but have yet to catch any flies at this location. This location is "New Hanover 1", and SWD trap capture data will be linked shortly.

These counts should not take the place of monitoring for growers or homeowners, since conditions will vary between locations. However, the population dynamics we observe may be useful for growers and homeowners conducting their own monitoring.

UPDATESpotted wing drosophila (SWD) trap captures for Ideal Track are now available here. The site name for Ideal is "New Hanover 1". All SWD monitoring sites are anonomized using county names and site numbers to protect the privacy of cooperating growers.

Thursday, April 28, 2011

Vegetable weevil in tobacco

Warm weather always brings new and unusual insect questions, and this week was full of interesting phone calls. On Tuesday, one of those calls was about about a tobacco field in the North Carolina sandhills with damage to recent transplants. The insects described were beetles with light chevron patterns on their backs, and they had nearly defoliated several plants in the first three rows. After receiving photos from David Dycus, NCDA & CS regional agronomist, it was clear that the insects responsible were vegetable weevil adults (Listroderes costirostris obliquus).

Vegetable weevils are a relatively common occurrence this time of year, and growers and homeowners should be on the look out for populations and damage.

Tobacco seedling with feeding injury from vegetable weevil (Listroderes costirostris obliquus). Photo: David Dycus.
Adult vegetable weevil. Photo: David Dycus.
Vegetable weevil is a non native pest in North America and was first detected in 1922. Originally from South America, adult vegetable weevil are active in fall, winter, and spring. Both adults and larvae feed on young plants, including turnip, carrot, collard, mustard, tomato, potato, tobacco, and a number of weeds. Adults disperse into crops fields in spring from their overwintering locations, and damage is often most severe along field borders. Because of this damage pattern, spot treatments may be sufficient to control populations.

The treatment threshold for recent transplants is 5-10%, and the field in the sandhills had sufficient damage to justify treatment. Several of the labeled insecticides in tobacco are registered for vegetable weevil. See the NC Ag Chem Manual for recommendations. One addition to the vegetable weevil recommendations not yet listed is lambda-cyaholthrin (Warrior or Karate in tobacco). This pyrethriod insecticide was the material I recommended for use in the case of the sandhills site. See a note on pesticide recommendations.

David and his fellow regional agronomist, Don Nicholson, also noted that several beetles appeared dead or dying near some of the plants. Don and David visited the field about 5 days after transplant, and the grower had used Platinum (thiamethoxam) in the transplant water. The Platinum applied at transplant may also have provided some protection against vegetable weevil, although transplant water application may take several days to move into plants. This may be why the beetles appear affected now but were able to significantly damage several rows of plants.

Damaged tobacco plant with dead or moribund vegetable weevil to the left. Photo: David Dycus.
More information
Vegetable weevil - University of Georgia Cooperative Extension

Wednesday, April 27, 2011

Organic blueberry spray guide from NCSU

Bill Cline
, NCSU extension plant pathologist based at the Horticultural Crops Research Station in Castle Hayne, NC, has spearheaded the development of an organic IPM program for North Carolina blueberries. Together, Bill and I have produced the 2011 Organic Blueberry Spray Guide. This document lists organically acceptable practices and management tools for key blueberry pests in North Carolina. This document is only intended for use by North Carolina growers. If you are interested in organic blueberry production information and are from another state, contact your local cooperative extension agent (see here to connect with your location extension personnel).

As with any "spray program", bear in mind that not all treatments are needed at each location. This document is not a schedule which should be followed, but instead a guide as to what pests may occur and how to manage them if present. Scouting & monitoring should be the keystone of any IPM program, and treatments should only be made if economically significant populations are present.

More information
Organic Blueberry Spray Guide - Bill Cline & Hannah Burrack

Thursday, April 21, 2011

NCDA & CS Agricultural Tornado Assistance Program

The North Carolina Department of Agriculture & Consumer Services has established a website to assist growers who experienced damage from last weekend's storms. The AgTAP website lists grower resources and current news. NCDA & CS has also established a hotline for affected growers at 866.506.6222.

More information
NCDA & CS Agricultural Tornado Assistance Program

Tuesday, April 19, 2011

Tobacco greenhouse pests - Aphids

Red & green color forms of the green peach aphid (Myzus persicae). Photo: Sterling Southern, NCSU.

I have gotten two calls and emails about aphids in tobacco greenhouses, specifically the red color form of the green peach aphid (Myzus persicae). This topic was among those I addressed in the very first Tobacco Connection Newsletter last March. Although they appear different, the red, green, and orange color forms of the green peach aphid are the same species and are managed in the same fashion. The main difference, other than color, of these different color forms is their environmental preferences and interactions with pesticides. In general, the green color form prefers cool temperatures and is more susceptible to pesticides. The red color form predominates in hot weather and has been documented to develop resistance to pesticides used in tobacco more readily.

We typically seen green color forms early in the season while red color forms dominate during the hotter summer months. Both color forms can be found year round in North Carolina, however. Virtually all conventional tobacco grown in North Carolina is treated with systemic neonicotiniods (imidacloprid and thiamethoxam) to control aphids and flea beetles in the field. For greenhouses with aphid infestations where transplant is within 5 days, these materials can be applied and will kill aphids prior to transplant. For aphid infested greenhouses where transplant is more than 5 days off, other treatments are available (see the NC Ag Chem Manual for specific recommendations or contact me and see A note on pesticide recommendations).

More information
NC State Tobacco Connection 1(1). March 22, 2010

Strawberry clipper update

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

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

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

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

Friday, April 8, 2011

New thrips flight prediction tool now available

Tobacco plant with systemic TSWV infection in a research plot; Craven County, NC, 2008. Photo: HJB

For the past 2 years, a group of NCSU entomologists and climate scientists have been developing a website designed to predict tobacco thrips (Frankliniella fusca) flights and make management recommendations to suppress tomato spotted wilt virus (TSWV) in tobacco.  We are proud to roll out this tool for tobacco grower, cooperative extension agent, and crop consultant use today! The TSWV and Thrips Exposure Tool for Tobacco uses temperature and precipitation data to predict tobacco thrips flight timing.  We then provide management recommendations based on grower provided transplant dates. 

Why do we need a tool to predict thrips flights?
Losses in tobacco to tomato spotted wilt virus (TSWV), which is vectored by thrips, vary greatly depending on year and location, with losses since 2000 in NC alone ranging from several million to over 45 million dollars per year.  In addition to killing young plants, TSWV reduces the uniformity, yield, and leaf quality of infected plants that are not killed. Tools for managing TSWV in tobacco are limited and must be applied before TSWV spreads into the crop. Imidacloprid (Admire Pro®) and Actigard® applied to transplants in the float house are the most commonly used TSWV management measures. However, the level of TSWV control provided by these materials has been inconsistent. 

Field studies at multiple sites in NC and GA have confirmed the value of using both Admire Pro® and Actigard® in reducing losses to TSWV. Results demonstrated that condition of the plants when float bed applications of either product were made influenced the degree of phytotoxicity, with the highest and most persistent levels of phytotoxicity always associated with the weakest transplants. Phytotoxic effects of pre-transplant applications of Admire Pro® and Actigard® can be minimized by applying them separately at least 1 day apart.  These studies confirmed that the greatest reduction in TSWV can be obtained when Admire Pro® (applied as a float tray treatment) and Actigard® are used, and demonstrated that the most effective application timing of Actigard® varies with year and location depending on when the spring flight of tobacco thrips and spread of TSWV occur. Tobacco thrips are the most important species for TSWV transmission in North Carolina and much of the southeast.

How do we know that treatments timed to predicted thrips flights are effective?
Field trials conducted by NCSU entomologists for the last 3 years and Clemson entomologists for the last 2 years have demonstrated that Actigard® treatments timed to thrips flights lower TSWV incidence.

Who should use this tool?
The TSWV and Thrips Exposure Tool for Tobacco should be used by tobacco growers in high risk TSWV areas in North Carolina. An area is considered high risk if it has a historical average TSWV incidence over 10%.

Distribution of tomato spotted wilt virus in North Carolina (based on county reports 1993-2008). The darker colors represent counties where TSWV incidence may be high (10 – 15%) in several fields every year.  Figure from Mina Mila, 2011. Flue Cured Tobacco Information, Chapter 8. Managing Diseases.

How do growers/agents/consultants use this tool?
For example, growers in high TSWV risk areas enter their location, tobacco type grown, anticipated transplant date, and any known or planned greenhouse treatments.  The models then predict, based on grower location, if tobacco thrips are expected to fly within the next 2 weeks.  If thrips flights are predicted, then the website suggests possible management options.  For example, if the predicted flight is within 2 weeks of transplant, a greenhouse treatment of Actigard® will likely result in the greatest TSWV suppression. On the other hand, if the thrips flight is predicted 3 to 4 weeks after transplant, a field treatment of Actigard® may be most effective.  Finally, if thrips are not expected until 8 weeks after transplant, treatment is likely not needed.  Of course, whenever using pesticides, always read and follow the label.  The label is the law! 

Thrips flight predictions are only available 2 weeks out at this time due to forecast data available.  As weather forecasting tools improve, so will the prediction length.

What if I am not in North Carolina?
We have tested the website in South Carolina, and predictions are reasonably close to those for North Carolina.  However, we have not tested the website in another southeastern states, so for the time being, we are recommending it only for use by North Carolina tobacco growers.

What if I grow other crops affected by TSWV?
Tobacco thrips may not be the most important vector in other crops affected by TSWV, such as peppers and tomatoes, so our models are intended only for use by tobacco growers.  We plan to expand these models for other crops in the future.

More information
TSWV and Thrips Exposure Tool for Tobacco
North Carolina State Climate Office
Tomato Spotted Wilt Virus - University of Georgia
Admire Pro - Product Label
Actigard - Product Label

We gratefully acknowledge the support of the Tobacco Research and Education Council, Inc., Altria, Phillip Morris International, and the R.J. Reynolds Fund for Excellence in developing and delivering the TSWV and Thrips Exposure Tool for Tobacco.

Strawberry clipper update

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

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

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

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

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

Tuesday, April 5, 2011

Today is a web-savy day! I just linked my phone to my blog to allow for even faster posting.

NC Small Fruit, Specialty Crop, and Tobacco IPM now on Facebook!

There's now a new way for you to access information from this blog and from the Burrack Lab at NC State, through Facebook.  Visit our new page here.  If you "like" our page, you will receive updates in your Facebook feed when new blog posts are added.  We will also add relevant content directly to Facebook.  Hope to see you there!

More information
North Carolina State University Small Fruit, Specialty Crop, and Tobacco Entomology - Facebook Page

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).

Periodic Cicadas - Clemson University

Monday, April 4, 2011

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.