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The 33rd International Carrot Conference, Anaheim, CA, USA
The 33rd International Carrot Conference was organised by the University of California Cooperative Extension and the Californian Fresh Carrot Advisory Board. The location was well chosen as most fresh market carrots in the US are produced in California, with continuous carrot production throughout the year. The talks and posters covered the full range of carrot production and the associated science, from carrot pathology to carrot production on board of the International Space Station.
Integrated strategies of disease and pest control were a major topic of this conference. Worldwide pesticide use is being restricted as public concerns about residues in food increase. A lot of groups which work on strategies of combined biological and conventional means of control presented their results in Anaheim. Good progress has been made in the control of foliar carrot diseases. Alternaria leaf blight (A. dauci) can be controlled more efficiently with combination treatments of systemic acquired resistance (SAR) inducing substances and fungicides than with fungicides alone (Z. K. Punja, Simon Fraser University, Canada).
Trimming of foliage to provide aeration and the application of gibberellic acid to the foliage against Alternaria leaf blight and Sclerotinia rot (S. sclerotiorum) reduced the incidence of these diseases.
Although these methods need to be refined for field application, they can help to reduce the use of fungicides.
Several groups around the world are currently working on carrot cavity spot of carrots (Pythium violae and P. sulcatum), my object of research. Jim Farrar of CSU Fresno (USA) reported that biological control through Trichoderma atroviride, several preparations to enhance the soil flora, change of soil pH and a SAR-inducing fertiliser failed to control cavity spot.
Fungicides based on azoxystrobin, fenamidone and cyazofamide controlled cavity spot disease, but are not available to British growers for that purpose. Breeding for resistance progresses, with some new varieties marketed as being resistant to cavity spot.
Kindly supported by the BSPP travel fund, I presented a poster on the role of non-carrot hosts on the epidemiology of cavity spot (P. violae). A lot of work still needs to be done to understand the infection process and epidemiology of P. violae and P. sulcatum and on reproducible pathogenicity tests. The conference was a great opportunity for me to exchange knowledge with pathologists and breeders from Europe and the US who are also working on cavity spot.
Root knot nematodes and their control were another major issue in talks and the field day. The current standard treatment is soil fumigation with nematicides in infested fields before sowing. Some alternative soil treatments with biological compounds like neem and sesame oil or biofumigation with Brassica-species and seed coating with abamectin were introduced as promising alternatives to soil fumigation. Promising sources of resistance genes to Meloidogyne javanica and M. incognita are being used by J. Nunez (UC Cooperative Extension) and breeding companies for developing new resistant varieties. They presented a talk on their trials and had prepared a demonstration trial for the field day. The field day was held on a trial site of the UC South Coast Research and Extension Center. We were guided to two trial fields, a variety display and a nematode resistance trial in which several breeding lines and varieties had been tested for resistance to M. javanica and M. meloidogyne.
I found the discussions with scientists, breeders and producers during the conference very useful. It was a welcome opportunity for me to learn what happens in other fields of carrot related research, and what the views of breeders and carrot growers are on various issues the carrot research community currently deals with.
Anne Kretzschmar, Warwick HRI, University of Warwick
