PM-01
Carrot rust fly, Psila rosae Fab. (Diptera: Psilidae): seeking new means of control
François Villeneuve1, Géraldine Maignien1, Jacques Poissonnier2, Bernard Guéry3, Sophie Szilvasi4
1 CTIFL, Centre de Lanxade, BP23, F24530 La Force, France
2 CTIFL/Hortis Aquitaine
3 DRAF- SRPV AQUITAINE, Centre INRA, Domaine de la Grande Ferrade, BP 81, F33883 Villenave d’Ornon Cedex, France
4 DRDAF-SRPV Nord Pas-de-Calais, 81, rue B. Palissy - BP 47, F62750 Loos en Gohelle, France
The carrot rust fly (Psila rosae Fab.) is an important pest of carrot crops in France and all of Northern Europe. In the climatic conditions of France, there can be three generations per year. This pest is taking on new importance with the reduction of the number of active ingredients available for crop protection, due to the withdrawal of organophosphates and carbamates; at this moment, only pyrethrins are available. Hence the necessity of initiating new research in order to find new means of both chemical and alternative control.
Research on chemical control should not only address the assessment of new active ingredients, but also risk prediction. So far, risk prediction is based on the trapping of females using passive yellow sticky traps. This technique has its limits, especially during the third flight, when the traps become less attractive, making risk prediction more difficult. For several years now SWAT, a German risk prediction model, has been tested. With a few adaptations to French conditions, this model gives fairly reliable risk forecasts.
Concerning chemical control, research has focused on seed coating (tefluthrin, clothianidin, spinosad, alone or in association), soil treatment (tefluthrin, bifenthrin, clothianidin), and foliage treatment (dimethoate, chlorpyriphos-methyl, delthamethrin, thiacloprid, spinosad, rynaxypir). Encouraging results where obtained with tefluthrin in soil treatment and rynaxypir in foliage treatment.
As for non chemical means of control, especially because there has been little evidence of parasitoids or predators of the carrot rust fly, research has concentrated on physical barriers (soil covers and vertical nets), resistant varieties, or repulsive substances. Except for soil covers, alternative means of control have shown no satisfactory results so far.
PM-02
The role of non-carrot crops and wild plants in the epidemiology of cavity spot (Pythium violae)
Anne Kretzschmar, Warwick HRI, University of Warwick, United Kingdom
In the UK carrot growers avoid fields which had been planted with carrots before in order to avoid cavity spot, mainly caused by Pythium violae. The inoculum of P. violae is assumed to remain in the soil for years after a carrot crop, although in low concentrations. It is not known what the most important resting structures are, how long they stay viable and what role alternative hosts play in the maintenance of P. violae inoculum. P. violae is known to have a wide host range. In our project at Warwick HRI we investigate how different rotations and companion plants affect the levels of cavity spot in carrots and the amount of P. violae in soil.
The non-carrot crops used in these field trials and common arable weeds are being tested for their role as host plants for P. violae. With a newly developed qPCR we can quantify the amount of P. violae in plant tissue and root surface soil of field grown and artificially inoculated plants.
PM-03
Banding low risk herbicides for weed control in carrots
Kevin Sanderson, Jerry Ivany, David Main and Basil Dickson
Agriculture and Agri-Food Canada, Crops and Livestock Research Center, 440 University Avenue, Charlottetown, Prince Edward Island, C1A 4N6, Canada
Carrot growers are continually faced with pressure to reduce pesticide use. In 2008, a low risk herbicide trial was set out to determine the effect of weed control strategies on carrots. The experiment was split-plot design with 2 planting times, June 9 and 25, with six treatments. Rows consisted of preformed hills spaced 90 cm apart. Treatments were Lorox , flaming, Ecoclear, Matran®, and Nature’s Avenger™ applied using a 30 cm wide band over the row. Banded treatments were compared to a broadcast application of Lorox. All treatments were applied pre-emergence except for the Lorox which was also applied post-emergence. The banded treatments had between row weeds removed by cultivation. Weed biomass by species, was determined using two quadrats on the top and side of each row. Total dry weight of weeds was reduced by 72% for the June 25 planting date compared to June 9. Lorox gave the best weed control with no difference between the banded and broadcast application. Ecoclear, Matran®, and Nature’s Avenger™ reduced dry weight of crab grass and total weeds and was intermediate to flaming and Lorox. All non-Lorox treatments were equally effective in controlling corn spurry. The effect of low risk weed control strategies on carrot yield will also be presented.
Poster Presentation: Kevin Sanderson
Phone: 902-566-6881
E-mail: sandersonk@agr.gc.ca
PM-04
Comparison of methods for detection of ascospores of Sclerotinia sclerotiorum
G.J. Boland1, M.R. McDonald2, M. Parker2, M.S. Melzer1, C. Saude2, S. M. Westerveld3 and M. Tesfaendrias2
Departments of Environmental Biology1 and Plant Agriculture2, University of Guelph, Guelph, Ontario, Canada, N1G 2W1. Ontario Ministry of Agriculture, Food and Rural Affairs, Simcoe, ON, Canada, N3Y 4N5
Ascospores of Sclerotinia sclerotiorum are the primary source of inoculum for epidemics caused by this pathogen in numerous crops. In carrot (Daucus carota subsp. sativus), the concentration of ascospores sampled within the crop canopy is related to the severity of disease that subsequently develops in the field. Several methods of sampling and detecting ascospores of S. sclerotiorum are being compared to identify the most effective method(s) to incorporate this variable into a disease forecasting model to determine the need and timing of applications of fungicide for management of sclerotinia rot of carrot. The methods include: 1) growth on semi-selective medium directly exposed within and above the crop canopy; 2) aerosol sampling within and above the crop canopy using a N6 (Anderson) single stage viable impactor with detection through growth on semi-selective medium, 3) aerosol sampling using a Zefon Bio-Pump with Air-O-Cell (assessment using microscopy) or 4) Via-Cell cassettes (assessment through serial dilution and growth on semi-selective medium), and 5) a Burkard 7 day recording volumetric spore sampler with detection using a polymerase chain reaction (PCR) assay. All of the methods detected ascospores on at least some sampling dates during 2006-07, except the Zefon Bio-Pump when using the Via-Cell cassettes. On most sampling dates, direct exposure of petri dishes containing semi-selective medium within and above the crop canopy were equally effective in detecting ascospores. Selection of the most effective method for a specific application is dependent on the cost and availability of laboratory equipment and supplies, and technical expertise
PM-05
Epidemiology of Rhizoctonia solani of carrot and first results on effect of biofumigation on the kinetics of the epidemic
Danielle Breton and Françoise Montfort
The poster will present:
• results of mapping of carrot damping-off after soil infestation with different level of Rhizoctonia solani AG2-2 inoculum
• sensitivity of R.solani to green manure volatiles of various Brassicaceae.
• results of effect of mustard on damping-off kinetic in artificially infested soil
PM-06
Black spots caused by Rhexocercosporidium carotae (syn. Acrothecium carotae)–a new threat against cold stored carrots
M. Wikström1, S. Ragnarsson1, B. Jönsson2, J. Köhl3, A.K. Arvidsson1, S.L.G.E. Burgers3, B.H. Groenenboom-de Haas3, and C.H. Lombaers-van der Plas3
1 DeFindus R&D AB, P.O. Box 530, S-267 25 Bjuv, Sweden;
2 Swedish Board of Agriculture, Plant Protection Centre, P.O. Box 12, S- 230 53, Alnarp, Sweden;
3 Plant Research International, P.O. Box 16, NL- 6700 AA Wageningen, The Netherlandands
Black spots on carrots have become an important threat to production of cold stored carrots in Sweden. Rhexocercosporidium carotae (syn. Acrothecium carotae) is found to be the dominating pathogen causing this problem. The pathogen was first described in Norway and later it has been reported also from Sweden, The Netherlands, Canada, and Denmark. The losses after storage have been substantial in carrots from many fields. Basic knowledge on R. carotae is very limited and important information is lacking. Therefore, a joint Swedish-Dutch project started in 2006 with the goal to gain more information about the biology of the pathogen and to develop a forecasting method for the disease. A TaqMan-PCR for detection and quantification of the pathogen in field samples has been developed and field inventories are ongoing. Preliminary results from these studies have shown that the disease has become more prevalent during the latest three years and it occurred in stored carrots from all the 50 investigated fields in 2007. Multiple regression analysis of data from the inventories of Dutch and Swedish carrot crops and the stored lots indicated that damage by R. carotae may be linked to harvest conditions resulting in different degrees of surface damage of the carrots. Also the presence of umbelliferous plants in the neighbourhood of the crop seemed to increase the prevalence of the disease, while clayish calcium-rich soils on the other hand might suppress the disease.