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SPRING 2008
Research on Diseases and Insect Pests of Carrots in Ontario, Canada
PNVA and Great Lakes Expo Carrot Session Reports
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Spring 2008 �
Vol. 16, No. 1 Spring 2008
4 ResearchonDiseasesandInsectPestsofCarrotsinOntario
10 PNVAREPORTGrowersHearDiscussionsRangingfromSpiderMiteControltoManagingWeeds.
12 GreatLakesFruit,Vegetable&FarmMarketExpoCarrotGrowersUpdatedonVariousProductionChallenges
In This Issue:
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9 TradeTalk15 CalendarofEvents15 PeopleintheNews15 ProductUpdate15 NewsRelease16 DiseaseIdentification
Departments:
Kevin Vander Kooi, Catarina Saude, Shawn Janse, Mary Ruth McDonald, Michael Tesfaendrias and Laura Riches form the carrot research team at the Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada. Photo courtesy of Dr. Mary Ruth McDonald
On the Cover:
Two-spotted spider mite feasting on a rose leaf. See page 10
USDA/ARS Photo
� Carrot Country
Carrots are the fourth most valuable field vegetable in On-tario. In 2006, the crop was worth $19 million and there were 8,250 acres of carrots in the province, 40 percent of
the total production in Canada. Approximately half of the produc-tion is on muck soil.
The major carrot diseases in Ontario are leaf blights (both Alternaria leaf blight and Cercospora leaf spot) Sclerotinia rot and cavity spot. Forking caused by Pythium species can cause major losses in some years. Aster yellows is a bigger problem on carrots grown on mineral soil, but was high on all carrots in 2007. Sclerotinia rot is the most important disease on carrots in storage, but botrytis gray mold and Rhizoctonia can also be problems in some years. Nematodes are controlled through crop rotation, late plowing and fumigation.
Carrot weevils are a persistent insect pest in carrot production. Carrot rust flies cause economic losses only in the Bradford/Hol-land Marsh area of the province. Insecticides are applied every year in an effort to control aster leafhoppers and reduce aster yel-lows. Much of the research on diseases and insect pests of carrots is conducted at the Muck Crops Research Station by researchers at the University of Guelph in cooperation with researchers in other areas of Canada and the United States.
The results of the major research trials in the past few years are summarized in this report. More details are available in the Muck Vegetable Cultivar Trial and Research Report which is published
by the Muck Crops Research Station each year (for a copy, contact Shawn Janse at [email protected]).
Carrot Leaf Blight
Carrot leaf blight in Ontario is caused by two fungi, Alternaria dauci (Alternaria leaf blight) and Cercospora carotae (Cercospora leaf blight). Both leaf blights can weaken carrot tops, which can lead to an inability to pull the carrots out of the ground using a mechanical harvester.
Trials were conducted in 2006 and 2007 on mineral soil to de-termine the relative importance of applied nitrogen and fungicide application on the control of leaf blights and on carrot yield. In 2006 there was a significant effect of fungicide on leaf blight and yield, but no effect of nitrogen on leaf blight or yield. In 2007, ni-trogen rate had an effect on disease but not on yield, while fungi-cide application increased yield and reduced disease (Table 1). The amount of Alternaria blight that developed over the season was the same on carrots that received 200 percent of the recommended rate of N and no fungicide, as it was on carrots that received no N, but three or five fungicide sprays. Thus 210 lb/acre of nitrogen provided the same disease control as 3 fungicide sprays.
The effects of N on Cercopsora leaf spot were only seen at the high (200 percent) rate where carrots that received 200 percent of the N rate and three sprays had the lower levels of Cercoposra leaf spot than carrots with no N or the recommended rate that
Research on Diseases and Insect Pests of Carrots in OntarioResearch and Report by: Mary Ruth McDonald, Kevin Vander Kooi, Catarina Saude, Michael Tesfaendrias, Sean Westerveld and Greg BolandDepartment of Plant Agriculture, University of Guelph , Guelph, Ontario, Canada
Spring 2008 �
Cavity SpotCavity spot of carrot occurs every year in the muck soil regions
of Ontario, but the severity can vary from year to year. There is a growing interest in carrots with different pigments, and carrots that vary from white and yellow to red and purple are available on the market. Pigments in carrots may provide some protection from cavity spot, or may be unrelated to disease development. Carrot breeding lines were obtained from Dr. Phil Simon, ARS, USDA, at the University of Wisconsin and were tested for three years. In 2006, carrots from different seed companies were included (Table 2).
Carrot lines with red pigments (lycopene) tended to be the most susceptible to cavity spot, while several with purple pigments (anthocyanins) had low susceptibility. However, pigmentation was not directly related to cavity spot incidence or severity. The influence of rainfall and temperature on cavity spot at harvest was greatest during the months of July and August, two and three months after seeding. Disease incidence in all the lines increased with increasing rainfall in August (r = 0.73), which ranged from 0.75 to 4 inches over the five years of study High mean maximum air temperatures in August were correlated with low incidence of cavity spot (r = -0.88), over a range of 70 to 75oF.
received five sprays. When looking at marketable yield, carrots receiving five fungicide sprays had higher yield than carrots that were not sprayed, regardless of the N rate. However, the highest yield occurred in carrots that received five fungicide sprays and no nitrogen.
Fungicide application decreased disease and resulted in higher yields. These carrots were hand harvested. If these carrots were harvested by machine, the differences should be even greater because tops of carrots with high level of disease would break, leaving the carrots in the field. Nitrogen application did not affect yields, but high N rates did reduce disease in the 2007 trial.
Table 1. Effects of nitrogen and fungicides on the severity of Alternaria and Cercospora leaf blights as determined by area under disease prog-ress curve (AUDPC) over the season and disease severity index (DSI) at harvest for carrots grown on mineral soil.
TreatmentN Rate (% of recommended)
z# of Fungicide Applications
wAlternaria Leaf Blight AUDPC
yCercospora Leaf Blight AUDPC
yMarketable Yield(t/ha)
x
0 0 487.5 a 376.9 a 39.9 c
0 3 421.2 bc 363.8 a 44.8 bc
0 5 420.0 bc 350.6 a 55.4 a
100 0 451.9 ab 360.0 a 44.3 bc
100 3 406.9 cd 354.4 a 46.1 abc
100 5 408.8 cd 345.0 a 51.0 ab
200 0 429.4 bc 352.5 a 38.3 c
200 3 343.1 e 298.1 b 45.0 bc
200 5 352.5 e 273.8 b 46.9 abc
200 5 @1/2 rate 378.8 de 290.6 b 48.9 ab
z Recommended Nitrogen rate for mineral soils= 110 kg/ha split 2/3 preplant, 1/3 side dress. N source was ammonium nitrate.
y Numbers in a column followed by the same letter are not significantly different at P=0.05, Fisher’s Protected LSD test.
W Fungicides were Lance, followed by 1 or 3 Bravo sprays, then Cabrio.
The carrot crew: Catarina Saude, Kevin Vander Kooi, Mary Ruth McDonald, Michael Tesfaendrias, Laura Riches
Cercospora leaf spot on carrot.
Continued on page 6
Symptoms of carrot weavil damageMary Ruth McDonald
Symptoms of cavit spot on carrot.
� Carrot Country
Table 2. Disease incidence and disease severity index (DSI) of cavity spot in different coloured carrots, grown at the Muck Crops Research Station, Holland Marsh, Ontario, 2006.
Cultivar Source1 Colour2
Disease Incidence (%) DSI3
16 Aug 27 Nov 16 Aug 27 Nov
Purple Haze Bejo P 11.3 a4 5.0 a 4.5 a 1.6 a
Cellobunch Sem O 27.7 abcd 22.0 ab 11.4 abc 8.8 ab
Belgian White BG W 39.8 cd 34.4 bc 13.0 abc 14.4 abc
YaYa Bejo O 37.8 bcd 30.0 b 10.2 ab 15.4 bc
Amarillo Yellow BG Y 26.3 abcd 38.0 bc 8.5 a 18.9 bcd
Rainbow Bejo M 37.8 bcd 40.0 cde 15.4 abc 19.5 bcd
Yellowstone GCS Y 31.3abcd 51.2 cde 9.0 a 21.3 bcd
Purple UW P 12.4 ab 39.2 bc 3.2 a 21.6 bcd
Cosmic Purple JSS P 13.3 ab 37.0 bc 6.2 a 23.0 cd
White UW W 68.0 e 53.5 cdef 29.9 d 26.5 cd
Yellow UW Y 48.8 de 66.8 ef 22.3 bcd 30.8 d
Mellow Yello Bejo Y 68.6 e 69.4 ef 24.4 cd 31.1 d
Dark Orange UW DO 18.3 abc 59.5 def 8.4 a 31.8 d
Dragon GCS P 14.7 abc 62.4 ef 7.0 a 32.0 d
Atomic Red JSS R 20.3 abc 68.2 ef 10.4 ab 50.2 e
Red UW R 17.8 abc 72.7 f 10.1 ab 51.2 e
Sclerotinia rot on carrots in storage.
Research on Diseases and Insect Pests of Carrots in Ontario from page 5
1. Sources UW = University of Wisconsin (breeding lines), Bejo = Bejo Seeds Inc, BG = Bountiful Gardens, CGS = Garden City Seeds, JSS = Johnny’s Selected Seeds, Sem= Seminis Vegetable Seed.
2. Colour = O = Orange, DO = Dark Orange, M = Mixed colours, P = Purple, R = Red, W = White, Y = Yellow.
3. Disease severity index (DSI) was determined using the following equation:
4. Numbers in a column followed by the same letter were not significantly different at P=0.05, Fisher’s Protected LSD Test.
SclerotiniaSclerotinia on carrot, also called cottony soft rot, can cause
major losses in storage. Trimming of the carrot leaves, at the time the leaves close over the row, has been shown to reduce the devel-opment of Sclerotinia in the field. Additional research in Prince Edward Island, by Kevin Sanderson and Rick Peters, has shown that trimming also results in a reduction of disease in storage. Trials in Ontario over three years looked at trimming the carrot leaves twice and whether this reduced the development of carrot leaf blight or improved the effectiveness of fungicides. Trimming twice further reduced apothecia production and hence the risk of Sclerotinia. Trimming reduced the severity of leaf blight in one of the three years, when disease pressure was low. Fungicide sprays reduced leaf blight but trimming did not improve the effectiveness of the fungicide.
Insecticide seed treatments can be a very effective method of insect control. Trials were started in 2007 to determine if seed treatments could provide control of carrot weevil or carrot rust fly
φ [(class no.)(no. of carrots in each class)](total no. carrots per sample)(no. classes -1)
DSI= X 100
Spring 2008 �
Seed catalogues for home gardeners often advertise carrots that are resistant to carrot rust flies. We tested three of these “resistant” carrot varieties, Resistafly, Sytan and Fly away in comparison to Cellobunch. Cellobunch had 6 percent rust fly damage, while damage to the other varieties ranged from 3 to 10 percent, and there were no statistical differences. Carrot weevil damage in Cellobunch was 3 percent and ranged from 0.7 – 3 percent in the other carrots, but again, there were no differences.
Editor’s Note: Dr. Mary Ruth McDonald can be reached by telephone at (519) 824-4120 or by email at: [email protected].
Carrots with different pigments from the 2007 cavity spot trials.
(Table 3). The levels of damage from both insects were low in the trials, however, some of the insecticides look promising for carrot weevil control. Entrust (spinosad) at 0.6 mg/seed was the most effective. A new insecticide combination, ( L1778-A) also had very low weevil damage. These trials will be repeated in 2008 to confirm the results.
Table 3. Effects of seed treatments for the control of carrot rust fly and carrot weevil in carrots grown at Holland Marsh, Ontario 2007.
Treatment Ratemg ai/seed
% Carrot Rust Fly Damage
% Carrot Wee-vil Damage
Marketable Yield (t/ha)
Check ---- 5.6 nsz 3.4 by 86.5 ns
Entrust 0.04 7.9 3.0 b 80.0
Entrust 0.06 7.2 0.1 a 84.8
Entrust 0.12 4.6 1.5 ab 93.2
Cruiser 0.04 4.3 1.5 ab 72.4
Cruiser 0.06 7.8 1.5 ab 88.8
L1778-A 0.09 8.0 0.8 a 78.3
L1778-A 0.12 5.4 0.4 a 86.3
z Not significantly different, P=0.05 Fisher’s Protected LSD Test.y Numbers in a column followed by the same letter are not significantly different at
P=0.05, Fisher’s Protected LSD test
� Carrot Country
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Trade Talk
Empire State Expo Includes Carrot/Beet SessionThe 2008 Empire State Fruit & Vegetable Expo includes
a “beet/carrot” session, scheduled Thursday, Feb. 14, from 1 to 2:30 p.m. at the Oncenter Convention Center in Syracuse, N.Y. The location is Rooms 4-6.
The session includes an update on herbicides for beets and carrots, recommendations on nitrogen management for car-rots on mineral and muck soils, and a presentation on what’s ahead in new varieties and markets. Presenters addressing carrot-related topics include: Robin Bellinder, Cornell; Sean Westerveld, University of Guelph; and Jan van der Heide, Bejo Seed Company, Geneva.
USDA Survey Measures Economic Well-being of Farmers
Farmers will soon have the opportunity to set the record straight about the issues that affect them – and to help ensure that policies and programs are based on accurate, real-world data. This is the goal of the annual Agricultural Resource Management Survey (ARMS), conducted by the U.S. Department of Agriculture’s National Agricultural Statistics Service (NASS).
ARMS is USDA’s primary source of information on production practices, resource use and economic well-being of America’s farm households.
“Just about every federal policy and program that affects U.S. farmers and farm families is based on information from ARMS,” said Chris Mertz, director of the NASS Oregon Field Office.
Between Feb. 15 and April 1, NASS field offices will contact 33,500 farmers nationwide by mail or phone to com-plete the survey. Producers will be asked to provide data on their operating expenditures, production costs and household characteristics.
“All farm operators rely on quality information and sound government policies in order to run a successful business. That’s why participation in ARMS is so important,” Mertz explained. “Producer participation in ARMS ensures that decisions affecting farmers, their families, their businesses and their communities are based on the facts, straight from the source.”
ARMS survey responses will be compiled and NASS will publish the farm economic data in the annual Farm Produc-tion Expenditures report, to be released on Aug. 7, 2008.
10 Carrot Country
Controlling spider mite populations can be a major challenge in carrot seed production in Idaho and the Pacific
Northwest.Speaking during the Pacific Northwest
Vegetable Association carrot session Nov. 14 in Kennewick, Wash., Robert Maxwell noted that the challenge of mites moving through nets protecting the seed is becoming a bigger and bigger challenge.
Maxwell is a carrot breeder for Seminis Inc., and is stationed at the company’s seed produc-tion facility near Payette, Idaho. The company had about six acres of carrot seed under produc-tion this past year.
Once inside the nets, the mite populations can literally explode, Maxwell told the group. Effective control measures have been lacking, and some of the best alternatives have unwork-able re-entry restrictions for employees who must complete certain tasks on time.
The history of materials available for mite control in carrot seed has been less than satisfac-tory, the carrot breeder said. Comite® and Agri-Mek® are on the market as possible options but for one reason or another have not provided adequate protection. Comite® has a 7-day re-entry restriction that is too long and Agri-Mek® showed no better protection than the control.
Maxwell reported on a mite-control study conducted in 2007 looking at Comite®, which
has a 24(C) registration in Washington, Oregon and Idaho; Acramite™ (Chemtura), applied at 24 oz/acre; Onager™ (Gowan), applied at 20 oz/acre; Zeal™ (Valent), applied at 3 oz/acre; plus a control. Comite® is the only registered product of the four included in the study.
In the tests, the best results came from Zeal™ and Comite®, Maxwell said. Ac-ramite™, Onager™ and the control results were “about the same.” Zeal™ controlled the mites without affecting yield or quality. Bee activity was reduced with Zeal™ and Acramite™, but yields did not suffer.
Maxwell was one of six making presenta-tions during the carrot session. Others were: Tim Waters, Washington State University Coopera-tive Extension, Pasco, Wash.; Doug Walsh, en-tomologist, WSU, IAREC, Prosser, Wash.; Rick Boydston, weed specialist, and Jim Crosslin, research plant pathologist, both with the USDA-ARS, Prosser, Wash.; and Nick David, a plant pathologist at North Dakota State University, Fargo, N.D., formerly associated with Oregon State University’s Hermiston Agricultural Re-search and Extension Center, Hermiston, Ore.
Spider Mite ChallengeTim Waters also addressed the spider mite
control challenge, reporting on research con-ducted with Doug Walsh.
In 2005 and 2006, Washington carrot grow-ers experience economic injury from late-sum-mer spider mite outbreaks, Waters reported. While several insecticides are registered for use against mites on carrots, they are not effective and are inappropriately broad in spectrum. At present, no miticides are registered for spider mite control on carrots in Washington.
“There are a substantial number of candi-date miticides that were tested for their efficacy on carrots,” Waters said, noting that the study will provide the state’s carrot industry with the required efficacy date for a Section 18 request in 2008 and forward a product into the IR-4 residue program for mite control in carrots. No miticides
are currently approved for use on carrots.
In the study, the researchers looked at: Oberon 2SC/spirome-sifen; JMS Stylet Oil; Comite/propargite; Fujimite/fenpyroximate; Champ/neem; Capture
2EC/bifenthrin; Zeal 2 oz./etoxazole; Zeal 3 oz./etoxazole; and Acramite 4SC/bifenezate.
PNVA Report
Growers Hear Discussions Ranging from Spider Mite Control to Managing Weeds
Two-spotted spider mite feasting on a rose leaf. USDA/ARS Photo
Rob Maxwell
Tim Waters
Spring 2008 11
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During the trials, the Capture 2EC flared the mites, Waters said. Oberon, Fujimite, Zeal and Comite all did a “pretty good job.” Oberon and Fujimite produced the best results.
In summary, Waters cautioned carrot growers to treat leafhoppers only when necessary. Other-wise, they run the risk of flaring the mite popula-tion. He also advised against using pyrethroids for the same reason.
Organic Carrot Production OptionsFor those involved in organic carrot produc-
tion, Doug Walsh reported on Entust™, Dow Agrosciences’ organically certified formulation for its biological insecticide spinosad. A review of his presentation appears in the fall 2007 issue of Carrot Country, page 13.
A tolerance for spinosad has been established on carrots, and a Section 3 pesticide registration has been established for foliar applications of the company’s spinosad insecticides, Success™ and Entrust™.
Dow representatives have agreed to pursue 24(C) Special Local Need Registrations for the company’s Entrust formu-lation for seed treatments on carrots. With due diligence, this registration will be submitted during
the winter months and the treated seed product potentially will be available for growers to plant this spring (2008), Walsh said, adding that this registration will “go a long way towards helping carrot producers produce certified organic car-rots in the future.”
Weed Control OptionsFocusing on weed control, Rick Boydston
reported on the current herbicides labels avail-able for use on carrots as well as general weed control recommendations.
“Carrots are very susceptible to weeds. They don’t provide a lot of competition to suppress weeds early in the season,” he said. “We did some studies a few years back looking at yield reductions with carrots and volunteer potatoes,
which can be a problem when we have mild winters, and saw yield reductions ranging from 22 to 91 percent.”
Weeds can also act as hosts to insects, pests, nematodes and diseases in carrots, Boydston said.
The speaker began his presentation talking about a few general pre-sowing and after-sowing strategies for non-herbicide control. Pre-sowing strategies include various types of tillage imple-ments and bed formers that can be used early on and weeding implements that can be used to eliminate the first flush of weeds.
“After you have sown your carrots, espe-cially in organic situations where you don’t want to use herbicides, you can use flame or steam weeding,” he said. “Another option is to har-
row, shallow, early in the season.”
One strategy that works well with carrots is to begin with a stale seed-bed, Boydston said. With irrigation, the growers can work the soil and prepare a bed early on before the carrots are even planted.
Sprouting weeds can then be removed via shal-low tillage. Withholding the irrigation is another option that can be used to dry out the weeds. Flaming, in organic systems, also works well as do herbicides such as Paraquat® used to burn down weeds prior to planting.
Among the herbicides labeled for carrots are Lorox®, Treflan®, Sencor®, Nortron®, Prowl® H2O, Round-up® and Gramoxone®, he said Nortron® (Enhofumesate) and Prowl H2O were registered for use on carrots just last year.
Nortron® is especially good for grass control, Boydston noted. Commonly used for weed control in sugarbeets, Bayer has limited registered of the herbicide to carrots grown in Washington and Oregon. When applied for control of volunteer potatoes, Nortron® delayed potato emergence, affected leaf formation and helped boost carrot yields.
On carrots, Nortron® is applied PRE at the rate of 48 oz/ac on coarse soils and 64 oz/acre on medium and fine soils. The early POST rate (PRE to weeds) is 64 oz/ac when the carrots are at the 2-4-leaf stage.
The second new herbicide, Prowl® H20, is applied at the 2 pt/ac rate with a maximum of 2
pts/season, the weed specialist said. It is labeled for chemigation pre-emergence of the carrots.
A third product, Dual Magnum, received a 24[c] label for Oregon last year, but not Wash-ington, Boydston said.
A third product, Dual Magnum, received a 24[c] for use on carrots in Oregon last year, but not Washington. Growers must indemnify Syngenta before using the product.
Aster Yellow ControlSpeaking on “Spyroplasm and Phytoplasm in
Carrots,” Jim Crosslin pointed out that both are transmitted by beet leafhoppers and affect a wide variety of crops, including carrots.
The problem for carrot growers is Aster yellows, a plant disease of the phy-toplasma group. Symp-toms on carrots include a yellowing of younger leaves, progressing to red or purple, dwarfed and
Doug Walsh
Rick Boydston
Jim Crosslin
Continued on page 15
12 Carrot Country
With new legislation in Ontario and proposed laws in the United States governing nutrient man-
agement and source water protection, can growers cut their fertilizer input and still produce a quality crop?
Canadian researcher Laura L. Van Eerd gave growers her observations during the Great Lakes Fruit, Vegetable & Farm Market Expo carrot session, held Dec. 5 in Grand Rapids, Mich.
Eerd is with the Land Resource Sci-ence Department, University of Guelph Ridgetown Campus, Ontario, Canada.
She was one of five speakers making presentations during the two-hour carrot session. Others were: Mathieu Ngouajio, Mary Hausbeck and Beth Bishop, with the departments of Horti-culture, Plant Pathol-ogy and Entomology, respectively, at Michigan State University; and Mary Ruth McDonald, Plant Pathology Department, University of Guelph, Ontario, Canada.
Got N? Nitrogen Management in CarrotsWith optimizing nitrogen use efficiency
in mind, Eerd reported on a two-year study in the Ontario area aimed at determining the optimal rate of nitrogen while assessing the value of split applications of N fertilizer and products such as UMAXX® that alter the release of nitrate over the season. The trials, conducted on six different sites on mineral soil typical of carrot production in the area, also attempted to determine the rate of ap-plied N fertilizer. Was it all being taken up by the crop or was some being leached below the root zone and lost in the field?
Here are some of her findings reported:There was no difference in carrot yield between all N treatments in four of the six sites. Average yields at sites #3 to #6 were 20.2, 25.6, 14.2 and 27.9 tons/ac, respectively, representative of Ontario carrot production on mineral soil.Based on the carrot contract price of $95/ton and fertilizer at 50 cents/lb, the most economical rate of N (MERN) was 96 to 102 lb N/ac. The MERN is the rate where applying more nitrogen will not produce enough additional yield to pay for the additional nitrogen applied.The studies showed no yield advantages of split applying N. As well, there were no differences in crop nitrogen uptake or removal between the split-applications compared to the same amount applied pre-plant.There was no carrot yield advantage of using slow-release fertilizers such as UMAXX®. Hence, use is not recom-mended because of the additional cost.As expected, the highest fertilizer treat-ments had the most residual soil nitrate, 89 lb N/ac, to the three-foot depth, at harvest. This proved a concern in terms of leach-
ing and because of the additional cost of wasted N, which worked out to be $45/ac. There was no difference in the amount of re-sidual soil nitrate to the 3-foot depth between the 0 and 100 lb N/ac.
Enhancing Carrot Rotation SystemsIn his report, Mathew Ngouajio, ad-
dressed the group on the benefits of using biofumigants and other cover crops to enhance carrot rotation systems.
Summing up his findings, the researcher reported that brassicas cover crops can successfully be fitted into carrot rotation sys-
tems. Such crops were planted after carrot harvest and reached the flowering stage prior to the first frost. Both the cover crops and the rotation crop (squash in 2007) could be used to improve carrot rotation systems and potentially help reduce nematode problems, he said.
Ngouajio reported on an on-farm trial established in Newaygo County, Mich., conducted in 2006 to test the effects of cover crops on carrot rotation systems with special focus on management of root lesion nematodes.
Herbicide programs used in carrots af-fected sorghum sudangrass and arugula cover crops established after carrot harvest, he explained. Sorghum sudangrass totally failed to establish, and arugula growth was slower than expected.
“Lorox® might be implicated,” he said, acknowledging, however, that it was not
possible to attribute the effect to a spe-cific cover crop as the trend was similar in all plots including the control.
The root lesion nematode population bounced back in soil samples collected af-
ter harvesting the winter squash crop used in rotation with carrots, he said. However, the level was generally low compared to 2006 and, this time, the brassica cover crop plots seemed to have lower levels than wheat. Blight Management Studies
Mary K. Hausbeck reported on research looking at “Using Skybit for Blight Manage-ment in Carrots.”
“The Carrot Weather Forecasting Project’s purpose is to test the TOM-CAST
Great Lakes Fruit, Vegetable & Farm Market Expo Report
Carrot Growers Updated on Various Production Challenges
Laura L. Van Eerd
Mathew Ngouajio
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Spring 2008 1�
single treatment threshold was established for the entire state and the entire season,” the speaker said. “This treatment threshold depended on a presumed infectivity rate, or one that was determined very early in the season. Usually that infectivity rate was around 1 to 3 percent.
“We compared treatment thresholds and resultant insecticide ap-plication recommendations between those that would have resulted from the older method (using a constant infectiv-ity rate of 2.5 percent) and those generated by current methods of testing leafhoppers (using the most recent infectivity rate). Of the six aster leafhopper samples tested, aster leafhopper populations at that site on that date exceeded the “new” treatment threshold three times. For the same dates and sites, the older treatment thresh-old would have been exceeded four times. How-ever, use of the “old” treatment threshold would have resulted in one unnecessary insecticide application (Mason County, July 15), and two necessary applications would have been missed (two sites in Mason Country, Aug. 7),” the speaker detailed.
Aster leafhopper infectivity testing remains crucial to helping growers make informed insecticide application decisions, Bishop reminded the group.
Mary Ruth McDonald’s presentation, “Research on Diseases and Insect Pests of Carrots in Ontario,” is reported separately in this issue.
system using either on-site weather data or weather data received via a satellite,” she explained. “The satellite weather information was sent by e-mail each morning from Skybit, Inc©.
“In each set of information sent, there were the weather data that were collected for the past 24 hours as it was observed through the satellite. A global positioning system (GPS) was used to determine
exact locations of our experimental sites to ob-tain the most accurate weather data,” she said. “The e-mailed weather data were copied into a program which formatted and summarized the data and predicted TOM-CAST spray dates. The on-site weather data comparison was collected using Spectrum Technologies© leaf wetness sensors and spray application dates predicted using TOM-CAST.”
Large-scale trials were at both MSU’s Muck Farm and on a grower cooperator’s farm in Mason County, Mich.
Here are a few of the findings reported:In the Mason County trial, both forecasting systems provided significant disease control compared to the untreated control. The fungicide treatment blocks had significantly better ratings for petiole health, blight severity and percentage of infected petioles than the untreated block of carrots.In the Muck Farm trial, both forecasting system also provided significantly better disease control than the untreated control. The fungicide application scheduled by Spectrum for on-site weather data had significantly better ratings in all areas of disease assessment compared with the block of carrots sprayed using the corrected satellite weather data.
Controlling Aster YellowsIn her presentation entitled, “Aster Yellows 2007,” Beth Bishop
noted the seriousness of the disease of carrots and other vegetable crops. Affected plants have distorted, discolored foliage and hairy, bitter-tasting roots.
Plants become infected with aster yellows after being fed upon by an aster leafhopper that carries the disease, the researcher explained. Once plants are infected, nothing can be done; the only way to pre-vent aster yellows is to control the aster leafhoppers that spread it.
Past research at MSU shows that the infectivity rates in the state vary from year to year and that both location and time of year influ-ence them, Bishop said. Due to previous testing, the university is able to provide growers with treatment thresholds that are specific to their local area and particular time of the season.
During 2007, aster leafhopper populations in northwestern Michigan carrot fields were low early in the season, Bishop observed. No leafhopper samples tests were received until July. During July and August, six leafhopper samples were submitted to Diagnostic Services for testing. Five came from Mason County and one from Oceana County. All leafhopper populations except one tested positive for aster yellows.
“Prior to 2000, when faster, less expensive methods to test aster leafhoppers for infection with aster yellows became available, a
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Mary K. Hausbeck Beth Bishop
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1� Carrot Country
Calendar of EventsFeb. 12-142008 Empire State Fruit and Vegetable Expo and Becker Forum, Holiday Inn Liverpool and Oncenter Convention Center, Syracuse, N.Y. Carrot/Beet session on Thursday, Feb. 14, from 1-2:30 p.m. Contact: Jeff and Lindy Kubecka, New York State Vegetable Growers Association, (315) 687-5734 or [email protected]
May 4-7United Fresh, Las Vegas, Mandalay Bay Convention Center, Las Vegas, Nev. Contact: United Fresh Produce Association, (202) 303-3400, www.unitedshows.com, www.unitedfresh.org.
Oct. 24-27PMA’s 2008 Fresh Summit International Convention and Exposition, Orange County Convention Center, Orlando, Fla. Contact: PMA, (302) 738-7100, www.pma.com.
People in the NewsEric Sheller Named to Georgia-Pa-cific Agronomy Staff
Eric Sheller is a new senior techni-cal sales agronomist for Georgia-Pacif-ic Plant Nutrition’s Nitamin® nitrogen fertilizer business.
Sheller is responsible for manag-ing the group’s West Coast sales and agronomy activities. He will also facilitate commercial grower trials of Nitamin 30L and Nitamin Nfusion™ in the region, and work with GP’s exclu-sive West Coast distributor, Wilbur-El-lis Company.
Sheller has broad expertise in the agricultural chemical industry. He is a California State Champion in land fertility, pest management, agricul-tural marketing and agricultural sales management. He received a bachelor’s degree in Plant Health from California State University of Fresno.
Product Update
New Technology for Handling Tarps: Grabbit Tarp Holder
Announcing the availability of the EZ Grabbit Tarp Holder from Grabbit Tool Company.
The EZ Grabbit Tar Holder is an innovative device using a new patented technology called linear grappling. Do things with your tarp that before were impossible: (1) Mount tarps to struc-tures; (2) fasten tarps together; and (3) grab tarps anywhere without tearing.
The EZ Grabbit Tarp Holder is far superior to Grommets, which are never
where you need them or tear out of the tarp or canvas. Quickly and easily attach tarps to structures, trucks, etc. Fasten or seam tarps together or grab tarps anywhere.
For more in-formation, con-tact Grabbit Tool Company, 1600 W. Evans Avenue, Ste. J, Englewood, CO 80110-1032, phone (877) 981-5262 or check the Web at: www.grabbittool.com
Carrot Trivia
The following trivia is from the World Car-rot Museum: www.carrotmuseum.com.
· Carrots have the highest content of beta carotene (vitamin A) of all veg-etables.· The wild carrot is called Queen Anne‘s lace.· The longest carrot recorded in 1996 was 5.14 meters (16 feet, 10 ½ inches).· The heaviest carrot recorded in the world was 18.985 pounds (1998, sing root mass). John V.R. Evans, USA.· Carrots were first grown as a medi-cine, not a food.· The average person will consume 10,866 carrots in a lifetime.
· Carrots produce more distilled spirit than potatoes. · Carrots were the first vegetable to be canned commercially.· The classic Bugs Bunny carrot is the “Danvers” type.· The carrot is a member of the parsley family including species such as celery, parsnip, fennel, dill and coriander.· Holtville, California dubs itself as “The Carrot Capital of the World.”· The Greek foot soldiers who hid in the Trojan Horse were said to have consumed ample quantities of raw carrots to inacti-vate their bowels.
News Release
Better Suspension, Better Control and Wider Tracks with Spra-Coupe 7655
The Spra-Coupe 7655 boasts im-proved suspension front and rear, added joystick capability and the ability to extend the axle to a 152-inch track. The smoother ride and improved controls will reduce operator fatigue and stress, while the wide track will fit every row crop situation.
For more information on Spra-Coupe, visit www.spracoupewillmar.com.
PHOTO CAPTION: The 2008 Spra-Coupe 7655 gives operators an even smoother ride, more convenient controls, a tracking option of up to 152 inches and new tire options that enhance flotation and reduce potential soil compaction.
Spring 2008 1�
twisted petioles and a dense growth of shoots. Infected carrots are slender, elongated and covered with a dense hairy growth of secondary roots. Even worse, the carrots often taste bitter.
Both spyroplasm and phytoplasm are showing up in carrot fields in the Columbia Basin, Crosslin said, and there are more mixed infections that either one alone.
Controlling the vector, the beet leafhopper, is the best method of mini-mizing any damage occurring, Crosslin said.
Ridomil® Resistance StudyNick David reported on a recent 3-year study involving researchers
in Washington, Oregon and Idaho looking into mefenoxam resistance in pythium. The presence of pythium in soil can cause a variety of pre- and post-emergent diseases in crops such as carrots, beans, corn, garlic, green
peas, onions and potatoes, he said. One of the major concerns for carrot growers
is cavity spot. Ciba-Geigy introduced Ridomil® to the market in 1978, and it proved a tremendous hit, David said. It controlled a lot of diseases, but since Ridomil® involves a single mode of action, resistance problems began showing up within a couple of years.
In the study, David, Phil Hamm, Debra Inglis and others looked at soil samples collected from
fields in Washington, Oregon and Idaho where carrots had been grown in the past or would be grown in rotation with potatoes. They found plenty of pythium in almost all fields. Their most important discovery, however,
disease identification
Editor’s Note: The material here is reprinted, with permission, from University of California Pest Management Guidelines, available on the Web at: http://www.ipm.ucdavis.edu/PMG/selectnewpest.carrots.html.
Pathogen:Cercospora carotae
Symptoms:Cercospora blight can occur on any above ground carrot tissue. However, symptoms are usually most severe and obvious along leaflet margins. Infection sites initially appear as a brown spot with a dark brown margin. A chlorotic halo often develops around these spots. As the disease progresses, the leaflets become yellowed and curl at the margins. Lesions on leaf petioles, stems and flower parts are usually elongated and dark brown. Under heavy disease pressure, severe loss of foliage may occur.
Comments on the Disease:Cercospora blight is usually of minor importance in California but often occurs in coastal carrot-growing regions. Cercospora carotae can be seedborne, but also survives between crops on plant debris or in the soil. Infection occurs over a wide range of temperatures with an optimum at 82˚F.
Management:Cultural Control – Use disease-free seed or treat seed with fungicides before planting. Destroy diseased crop refuse by
plowing it under to insure decomposition and practice 2- to 3-year crop rotations.
Organically Acceptable Methods – Cultural controls are acceptable for use on organically grown produce.
Monitoring and Treatment Decisions – In fields with a history of Cercospora leaf blight, start fungicide applications when conditions are conducive to disease development or when disease is observed. Thiram 50 WP is available as a seed treatment. After planting treatments include azoxystrobin (Quadris), chlorothalonil (Bravo Weatherstik), copper hydroxide, pyraclostrobin (Cabrio) EG and trifloxystrobin (Flint).
Cercospora Leaf Blight
Carrot leaves with Cercospora Leaf Blight
PNVA Report continued from page 11
was that there was “quite a bit” of resistance showing up in Oregon and Washington fields. Not much was detected in Idaho, with the exception of Power County, David said.
For growers planning on growing carrots in the three states in 2008, David recommended testing the prospective fields for the presence or absence of Ridomil-resistant pythium. That said, even if a certain level of resistance is discovered, don’t abandon using Ridomil®, he cautioned. The reason is there is still a lot of the pythium population that is Ridomil® sensitive and can be controlled with the formulation.
What else is in the tool box for pythium control? Not much, the plant pathologist declared. There is nothing out there that delivers the comfort level associated with Ridomil®. Vapam® (metam sodium) was looked at for reducing the pythium population but not at reducing the incidence of cavity spot or damping off.
“We just looked at the pythium control level,” the researcher acknowl-edged, and “it (metam sodium) does have efficacy in reducing pythium inoculum.
Recommended cultural practices include: (1) monitoring soil mois-ture—avoiding excessive irrigation; (2) soil aeration—hard pans can restrict water movement; (3) monitoring soil pH and calcium levels—some studies show less when the pH is above 7; (4) be aware of the implications of plant age—cavity spot increases as plants age; and (5) consider resis-tance cultivars—there is some positive information that there are benefits.
“We do have an issue with Ridomil® resistance in the Columbia Basin, and there are pythium populations that Ridomil® does not control,” David said, acknowledging that there may be both resistance and degradation issues associated with Ridomil® use.
Nick David
