Thielaviopsis basicola is common storage pathogen for carrot roots Article Moulds that should be better known: Thielaviopsis basicola a...
Is there any efficient treatments against the pathogen suitable for vegetable crop?
To reduce the carrot black rot in the storage you can address the issue by prevention in the proactive management of the field soil. You may want to have a rotation where the cover crop or preceding crop is not a host. If you are able to plant oil radish it can lead to a biofumigation effect. In addition, Black rot in carrots is a cool season pathogen. Some approaches would be use a solarization combined with organic amendment to reduce the black rot pathogen population. By going for a more summer planting the temperatures will be less favorable for black rot. Another recommendation in the literature is maintaining pH 5.6 or slightly less which does not support aggressive black rot. In terms of storage the use of a conditioning protocol which would stimulate the systemic acquired resistance or the application of SAR promoters might be very useful. Hope some of these ideas are helpful.
Thank you Paul,
We will try to fix the problem next year following your recommendations.
Merry Christmas and a Happy New Year!
Alex
Many storage issues are helped by the optimizing of the mineral nutrition of the host plant and stimulating the plant defensive reactions. In many cases the optimizing of Calcium nutrition can help the integrity of storage organs related to necrotrophic pathogens. In relation to Calcium the ability to optimize Calcium is difficult if Boron is deficient. The use of complete soil and tissue analysis might be very helpful and be able to suggest areas of improvement. Beside the issue of nutrition the use of stimulated systemic acquired resistance by appropriate stimulus is a possible way to reduce the development of issues in storage. It will be very important to review and contemplate the recommended conditioning as post harvest curing conditions. The harvesting operation can be something that leads the way to issues related to mechanical damage the techniques and adjustments of harvesting can be very determinant of storage losses and looking at the venues of mechanical damage and ways to minimize these can be of critical importance.
Dear Doctor Ignatov, In relation to black root rot of carrots the organisms of biocontrol are Trichoderma harzianum and Pseudomonas fluorescens.
For an organic approach these organisms might be very useful for your purposes.
My idea of stimulating the calcium metabolism has a caveat pH of under 6 is known to inhibit the casual fungicide. Suppressive soils would have high P. fluorescens and a high availability of iron which favor the natural biocontrol.
I think the biocontrol mixture Trichloderma and Pseudomonas as a seed treatment and follow up with Systemic Acquired Resistance stimulated by salicylic acid products.
If you could map your soils the areas which are alkaline might be treated to reduce pH by selective sulfur because it is well demonstrated that neutral alkaline stimulate your black rot issues.
I did additional literature research and would couch my first remarks.
You may want to review the literature on suppressive soil for black rot which stress Pseudomonas under an acid environment which favors the iron metabolism of the bacteria of control. Commercial products of Pseudomonas and Trichoderma are available and you may want to test them for efficacy.
Sincerely, Paul Reed Hepperly
Dear Paul, thank you a lot for the ideas, we will try everything. So far,
Thielaviopsis basicola infect plants together with plant pathogenic Leuconostoc mesenteroides.
Alex
Leuconostoc mesteroides is known to enter washer injuries.
I think the harvest reduction of mechanical injury and the prestorage treatment could be very important.
The root crops generally need a period of healing which is done at higher than ambient temperature and good aeration to scarify the wounded tissues. The treatment might be combined with a surface disinfestation with something like Calcium hypochlorite to eliminate surface contaminants. You will need to review some of commercial carrot recommendations not be starting at zero.
The use of elevated temperatures in a 2 to 3 day period can trigger heat shock proteins which are important in the ability of the plant to adapt to storage issues. The elevated temperature and high humidity can trigger host reactions which produce lignification but also the acquired resistance mechanisms.
Dear Alex, Check Eshel, et al 2009. Combining physical, chemical and biological methods. Post Harvest Biol. Technol. 54(1): 48-52.
This article says hydrogen peroxide and biocontrol yeast can work synergistically as post harvest carrot treatment for black rot pathogen.
The good thing about hydrogen peroxide it can remove the bacteria of your concern. In addition the by products of hydrogen peroxide is water and oxygen. Very safe and environmentally friendly and for the consumers and workers.
Paul, thank you! I haven't thought about yeast as biocontrol agent. Bacterial agents were not efficient enough.
The US Department of Agriculture Research Service have shown efficacy of yeast for apple and pear post harvest decay disease control. C. Wilson was one of the primary scientists in that effort. They also showed these yeast control trigger the systemic acquired resistance mechanism you may want to look at their work.