Technical articles

This biocontrol technique consists of spraying a thin layer of calcined clay on the plant to establish a protective mineral barrier. It is a preventive action that disrupts the targeted pest at certain stages of its cycle. There are different hypotheses regarding the modes of action involved :

disruption of host plant recognition by the white color that the clay gives to trees or target organs.
physical barrier and modification of environmental conditions affecting the biology of the insect. Its movements are disturbed by the particles; the insect is hindered in laying eggs, breathing, and feeding.

Technique

The technique consists of spraying a thin layer of calcined clay on dry plants and under low wind conditions. It is necessary to agitate the mixture throughout the treatment to keep it in suspension and to adapt application conditions (adequate concentration, maximum 3 per thousand, working pressure below 10 bars, type of nozzles…). Moreover, the volume of mixture must allow good wetting without reaching runoff.

A sprayer suitable for clay spraying with a diaphragm pump and ceramic nozzles (more durable over time) are recommended for implementing this technique.

The appropriate timing depends on the targeted pest. For this, the technique must rely on decision support tools (DST) such as trapping and visual observation of pests to monitor their presence and schedule treatments.

The use of clays is a main lever for several pests including the olive fruit fly (Bactrocera oleae) on olive tree, the cherry fruit fly (Rhagoletis cerasi) on cherry tree, the pear psylla (Cacopsylla pyri) on pear tree, the green leafhopper (Empoasca vitis) on grapevine for table grape and the walnut husk fly (Rhagoletis completa) on walnut tree.

This method is also a complementary lever or has a physical barrier effect on other pests such as green leafhoppers on clementine, the Mediterranean fruit fly (Ceratitis capitata) on late varieties of apple tree and clementine, the vector of Apricot Chlorotic Leaf Roll Virus (ECA) (Cacopsylla pruni) on apricot tree, plum tree and peach tree (to be validated under commercial conditions on peach tree).

In organic farming, clays have a complementary effect on population levels of migrant and non-migrant aphids. Studies conducted on the green peach aphid and the apple gray aphid have shown a reduction in outbreak intensity. Studies conducted at SEFRA and GRAB have shown a partial effect on Drosophila suzukii. However, fruits (cherries) often remain marked at harvest and are unfit for consumption unless the epidermis is washed.

Example of implementation

Against flies on olive (minimum 3-4 passes) and cherry (1 to 2 passes max)

Treatment should begin as soon as the first flies are observed (trapping), depending on climatic conditions (hot and dry weather is very unfavorable to the pest). Renewal is necessary as soon as uncovered fruit areas appear or after washing by rain or erosion by wind. A last application 15 days before harvest is recommended to limit fruit marking.

Against walnut husk fly on walnut tree (3-4 passes)

Treatment should begin as soon as the first flies are observed (trapping), then a second application 8 days after the first, with renewal depending on rain washing.

Against pear psylla (1 to 3 passes in winter and 0 to 4 in season)

Winter applications targeting the first generation, from the egg-laying of overwintering females : timing is before the start of egg-laying by overwintering females with renewal until bud break depending on rainfall and presence of adults in the orchard environment (checked by beating).

Seasonal applications targeting the 2nd generation and subsequent ones are also possible. These post-flowering applications (before egg-laying of the 2nd generation with renewal every 8 to 10 days depending on new leaf emergence) are only recommended if G1 could not be controlled (presence of honeydew during flowering).

The last application should be about 30-40 days before harvest to reduce the risk of fruit marking.

Against the vector of ECA (1-2 passes on plum and apricot trees)

Treat before insect return to trees (before bud break) and until flowering. Renew treatments depending on washing on 2-year-old wood. It is unnecessary to systematically cover current year shoots, as C. pruni pierces 2-year-old wood.

Against green leafhoppers

On table grapes : applications are made as soon as leafhopper larvae appear, to be renewed depending on washing. The last application is before cluster closure to limit fruit marking.

On clementine : applications are made as soon as the first adults appear in chromatic traps (often late October-early November in Corsica), to be renewed depending on washing. On this fruit species, clays are sometimes applied until harvest if cleaning is possible at the packing station.

Against Mediterranean fruit fly

Only one application is made before maturity (at worst at R – 21 days) depending on trapping levels. The delay between application and harvest depends on the washing and brushing capabilities at the packing station.

Against migrant aphids

In autumn : treatments are timed before aphid return flights or as early as possible depending on harvest dates for species harvested in autumn. The later the intervention, the more eggs have already been laid.
In spring : limit the establishment of founders and secondary colonies.

Details on the technique

For good effectiveness, it is imperative to target treatment periods and frequency according to the biological cycle of the pest to be controlled.

Clay use is limited to certain stages due to fruit marking.
No treatment during flowering to protect bees and pollinators.
Do not forget personal protective equipment (mask against dust).

Implementation period

On established crops
Cumulative effect over several years: ultimately, reduction in the number of interventions after winter with equivalent effectiveness.
Effectiveness directly conditioned by application persistence.

Spatial scale of implementation

Plot
The larger the plot block, the better the control.

Application of the technique to...

All crops : Sometimes difficult to generalize

Sometimes difficult to generalize

Sometimes difficult depending on the fruit species concerned (cannot leave white deposits on fruits)

All soil types : Not applicable

Not applicable

All climatic contexts : Sometimes difficult to generalize

Sometimes difficult to generalize

Impossible if snow remains on the plant

Regulations

Only a few commercial products based on Kaolin are authorized for plant protection uses. Since April 2014, aluminum silicate (kaolin) is listed in Annex II of Regulation (EC) No 889/2008: therefore, commercial plant protection products based on kaolin authorized in France are usable in Organic Farming.

The application of clay on crops to make them less susceptible to insect attacks by forming a protective film is the subject of a CEPP sheet (action no. 39 : Fighting piercing insects using a biocontrol mineral powder).

Effects on the sustainability of the cropping system

Environmental criteria

Effect on air quality : Decreasing

phytosanitary emissions : DECREASE
GHG emissions : INCREASE
particle emissions : INCREASE

Effect on water quality : Increasing

pesticides : DECREASE

Effect on fossil resource consumption : Increasing

fossil energy consumption : INCREASE

Other : No effect (neutral)

Additional details or comments :

No known significant effect on environmental compartments (air, water, soil)

Agronomic criteria

Production quality : Variable

Variable

No phytopharmaceutical residues, limits sunburn (walnut-pear-apple), improves fruit epidermis quality (apple-pear).

Risk of fruit marking for in-season applications (do not apply clays 15 days before harvest for cherries and table olives and 30-40 days before harvest for pear).

Soil fertility : No effect (neutral)

No effect (neutral)

Water stress : Decreasing

Decreasing

Regulation of plant water stress

Functional Biodiversity : Variable

Variable

Low direct toxicity on beneficials. However, indirect effects observed on some families of beneficials such as typhlodromus (natural predators of yellow and red mites and phytoptids of acariosis or erinose. They can also feed on thrips larvae)

Economic criteria

Operating costs : Increasing

Increasing

Cost : between €1.4 and €1.8/kg (about €50 at 30 kg/ha/pass and about €80 at 50 kg/ha/pass)

Mechanization costs : Increasing

Increasing

Specific passes, especially after winter

Social criteria

Working time : Increasing

Increasing

Specific passes especially after winter or in autumn (physical barrier for aphids)

Peak period : Variable

Variable

Working time similar to a conventional treatment if same settings. However, frequent treatments in spring : renewal as soon as new sensitive organs appear (or rainy episodes)

Autumn-winter treatments are less frequent as renewal only occurs depending on rain (psyllid).

Observation time : Increasing

Increasing

It is always more difficult to observe whitened leaves : physical barrier that can cover eggs ...

Favored or disadvantaged organisms

Disadvantaged pests

Organism	Details
Olive fruit fly (Bactrocera oleae)	This technique is a main lever against this pest
Cherry fruit fly (Rhagoletis cerasi)	This technique is a main lever against this pest
Green leafhopper of grapevine (Empoasca vitis)	The technique is a main lever on table grape and a complementary lever on clementine
Walnut husk fly (Rhagoletis completa)	Technique used on walnut (low-height trees)
Mediterranean fruit fly (Ceratitis capitata)	The technique is a complementary lever on late varieties of apple and clementine
Pear psylla (Cacopsylla pyri)	The technique is a main lever for winter clay applications and a complementary lever for in-season applications.
Green peach aphid	Used in organic farming (interest to confirm in conventional)
Vector of Apricot Chlorotic Leaf Roll Virus (ECA) (Cacopsylla pruni)	This technique is a complementary lever on apricot, plum and peach (to be validated under commercial conditions on peach)

For more information

Apricot : prioritize observations and biocontrol to reduce IFT: Sophie Buléon - Ecophyto DEPHY, Technical brochure, 2015 Link to brochure
Applying a mineral barrier against the olive fruit fly. Part 1 - Preparation advice. Siciliano A. Olive Technical Center
Applying a mineral barrier against the olive fruit fly. Part 2 - Nozzle test. Siciliano A. Olive Technical Center
Clays in arboriculture : apple, pear, cherry, olive - Berud M., Warlop F., Libourel G., Filleron E. Regional Chamber of Agriculture PACA, Technical brochure, 2013 - Regional Chamber of Agriculture PACA, Resources, Collection 1 : Alternative techniques, document 1 D. Link to brochure
Effectiveness of clay on several pests encountered in fruit arboriculture. - Darthout L., Favareille J. 2006 French Association for Plant Protection (AFPP) - 3rd International Conference on alternative crop protection methods. Lille, France, 13-15 March 2006.
Kaolin particle films suppress many apple pests, disrupt natural enemies and promote woolly apple aphid -Marko V., Blommers L.H.M., Bogya S., Helsen H. Journal of Applied Entomology, Peer-reviewed article, 2008 - Journal of Applied Entomology, (2008) 132, 26-35 . For further reading link to article
Clay blocks the psylla - Piffady-Durieux A. 2013 Réussir Fruits & Légumes, 327, 34.
Kaolinite clay, a new method of control by protective mineral barrier against the green peach aphid Myzus Persicae Sulz - Garcin A. Agronomic innovations, Peer-reviewed article, 2009 Agronomic innovations (2009) 4, 107-113. Link to article
Pear : Maintain an eco-efficient orchard by combining different levers - Audrey PIFFADY-DURIEUX - Ecophyto - DEPHY, Technical brochure, 2014 Link to sheet
The impact of some compounds utilised in organic olive groves on the non-target arthropod fauna: canopy and soil levels. - Annotta N., Belfiore T., Noce M.E., Scalercio S., Vizarri V. 2007 - VI International Organic Olive Days, 22-25/03/2007, Puente de Génave, Spain.
Evaluation of AGX 12®, Sokalciarbo® and Prev-Am® to fight green leafhoppers on citrus - Areflec. Experimentation station., Professional report, 2006 - Areflec, Test results report. Link to report

Keywords

Pest control method : Biological control
Mode of action : Action on initial stock Barrier
Type of strategy regarding pesticide use : Substitution

Sources

Information initially from the Guide for designing fruit production systems sparing phytopharmaceutical products (2014) / Technical sheet no. 13 . For more information: See link

Appendices

S'applique aux cultures suivantes

Défavorise les bioagresseurs suivants

Application of Clay (Calcined Kaolinite) in Orchards

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