Protection methods
 

• During cultivation

If you are faced with attacks of Thanatephorus cucumeris (eg Rhizoctonia solani ) in the nursery, we advise you to eliminate diseased plants and those nearby. If you have any doubts, you can carry out a localized fungicide treatment at the outbreaks with one of the active ingredients known to be effective on this fungus. Currently, no fungicide * is authorized for this use on tomatoes in France ( e-phy ).

It is also necessary to control the climate as much as possible in order to avoid excess humidity and temperature . The irrigation of the plants will be optimal. It should not be excessive and will allow good wiping of the substrate.

Attacks on adult plants are never harmful and therefore do not require special measures.

In all cases, plant debris and diseased plants will be removed during and at the end of cultivation.

• Next crop

To avoid introducing this parasitic fungus into your farm, it will be essential to use a healthy substrate and quality plants . Plants produced in mini-nets or on other substrates should not be placed directly on the ground, especially if it has not been disinfected; a plastic film will have to insulate them.

In heavily contaminated soils, disinfection of the soil with a fumigant may be considered ( e-phy ). The active ingredients conventionally used (metam-sodium, dazomet ) and the vapor are effective with regard to T. cucumeris . Particular care should be taken to avoid reinfection of the soil after treatment. It should be noted that the combination of metam-sodium and formalin has proven to be very effective in controlling terrestrial attacks of T. cucumeris , but also of Fusarium oxysporum f. sp. radicis-lycopersici and Verticillium dahliae .

In production areas where it is possible, solar disinfection of the soil ( solarization ) will be carried out. Quite spectacular results have been recorded in particular in certain Mediterranean countries: the soil to be disinfected is carefully prepared and moistened, then covered with a polyethylene film 35 to 50 µm thick, held in place for at least one month in a very sunny period. of the year. This economical, efficient method makes it possible to get rid of this superficial colonizing fungus from the soil.

Of course, the agro-cultural measures recommended previously during cultivation must be implemented. In addition, heavy and wet soils will be drained and plowing will be carried out before planting in order to bury part of the sclerotia which are more quickly destroyed in depth. Crop rotations can be carried out with cereals, sweet corn, fodder grasses and onions. We will plant the tomatoes on hillocks and they will be staked. The soil should be mulched to prevent the organs of the tomato (in particular the fruits) from coming into contact with the soil and the water sometimes present on the surface. In addition, it will in some cases promote better aeration of the crowns of plants and vegetation. Fertilization should be balanced, in no case too low in nitrogen.

There is no currently resistant variety . Selection work is underway in order to obtain varieties with resistant fruits.

Several antagonist microorganisms have been experimented with to control T. cucumeris : Bacillus lentimorbus, B. subtilis, Burkholderia cepiacea, Pseudomonas aeruginosa, P. fluorescens, Streptomyces sp., Paenibacillus lentimorbus, Pochonia chlamydosporia, Chaetomium globosum, Glomus mosseum, Niveum Trichoderma viride, T. harzianum, T. koningii Although promising in some cases, the use of these microorganisms is not yet sufficiently reliable to be able to recommend them in the field.

Let us also point out other unconventional solutions which have revealed some potential with regard to this fungus: amendments based on Azadirachta indica in particular, essential oils of Callistemon lanceolatus and Ocimum canum , antioxidants


* Chemical control : As the number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog of plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.