Clay spraying on lavenders/lavandins
Kaolinite (aluminum silicate) acts preventively on the infestation of lavender and lavandin plants by disturbing the behavior of insects. The creation of a white film on the foliage disrupts the insect vector of the phytoplasma and limits its feeding punctures at the time when the plants are most vulnerable: the summer following planting and the summer of the first cut.
The presence of clay does not reduce photosynthesis. On the contrary, in case of high heat, it protects the plants.
This product is also safe for bees – an important issue for the beekeeping sector.
Context
The crops of lavender and lavandin face mortalities attributed at least in large part to the phytoplasma of Stolbur, transmitted by a cixiid, Hyalesthes obsoletus. Despite the implementation since 1994 of control methods, namely the creation of disease-tolerant varieties and the establishment of a certified healthy plant production sector, mortalities remain significant today.
Climatic sequences observed since 2003 (spring and autumn droughts, heatwaves) have worsened mortalities in the production area, due to direct impacts on crops (water stress), but also indirect impacts (vector insect populations favored by high temperatures).
The current situation is increasingly worrying: the lavender varieties created no longer seem able to stem the progression of mortalities and cultivated areas decrease year by year. Lavandin is also in a risky sanitary situation due to a near-genetic homogeneity of cultivated plants (three-quarters of the area is represented by a single clone, Grosso), and the increasing mortalities of plants of this Grosso clone.
Deployment
Current deployment
Little used. Only a few producers in the production area use it (less than 1% of the area).
Deployment planned over time
If a systemic approach demonstrating real effectiveness can be proven, the use of clay could be deployed on lavenders and lavandins (other than the Grosso variety). This represents about 8,000 ha. The impact of leafhopper punctures is strongest during the first two years after planting. Therefore, the maximum number of hectares potentially concerned in the short term could be estimated at about 2,000 ha.
The development of this solution can only be done on new plantations, so implementation will be progressive over several years if proof of effectiveness and interest is established.
The need for additional experimental data does not allow short-term deployment: 25% of new plantations by 2025 (provided sufficient combined effectiveness is demonstrated).
Deployment indicator
Sales of approved products.
360° Analysis
Level of reduction in use and/or potential impact
Means of control against decline are currently only prophylactic and are likely to remain so. Indeed, direct control of the phytoplasma is not possible because antibiotics, active molecules effective against bacteria, are prohibited for use on crops in France. As for direct chemical control of the leafhopper Hyalesthes obsoletus, it is difficult to consider. Indeed, larvae are untouchable by conventional insecticides because they live in the soil. Regarding adults, their flight periods coincide with the flowering period of lavenders/lavandins and thus with the presence of bees. Control is therefore currently indirect by using varieties selected for their tolerance to decline and healthy plants. Thus, the use of clay does not replace chemical treatments but acts as a link in the chain of possible prophylactic solutions.
Barriers to overcome and conditions for success
Despite the interest of the method, demonstrated in numerous trials, the effectiveness of clay spraying does not guarantee 100% protection of the crop, which discourages producers from adopting it. Especially since it requires adapting spraying equipment: membrane pump rather than piston (abrasive product), need for a spraying kit with 3 double-slot nozzles, etc.
No health-related or hardship barriers are observed with the use of clay.
Refining the application protocol and integrating the use of clay into an innovative itinerary (including notably cover crops, tolerant variety, and healthy plants) would allow, through new experiments, to demonstrate its effectiveness and thus its interest for the lavender sector.
Additional cost or gain
The additional cost is estimated at about €300 excluding tax for 3 spraying kits and between €40 and €45 excluding tax/ha for the product (2 annual applications). The additional cost thus remains quite low.
Stakeholders' commitments for deployment
IBMA France (French association of biocontrol product companies): Promote awareness of these biocontrol solutions. Encourage the development of training on biocontrol to learn how to use these solutions.
Acta – Agricultural technical institutes through Iteipmai: Propose modifications to crop itineraries to disrupt the biology of the phytoplasma vector insect and thus reduce decline pressure on lavender fields.
PPAM de France: Communicate to producers about the existence of this solution and promote its use.
Concerned sectors
Lavender and lavandin crops
Sources
Original version of this article: Contrat de Solutions: https://contratsolutions.fr/le-contrat-de-solutions/pulverisation-dargile-sur-lavandes-lavandins/
