Presentation

Characterization of the technique

Principle

This consists of protecting crops from attacks by insects pests through the installation of tarps, veils or nets, on or around the crop, to physically prevent pests from accessing the plants. For insects that fly close to the ground, vertical nets can be placed around the crop; for others, it is necessary to cover all the plants. A difficulty is knowing when to set up these protections, which generally cannot be permanent due to other interventions required on the crop.

Details on the technique :

Set up the physical barrier in case of risk, especially before the first flights of the targeted pest(s).

Barriers are installed at openings in crops under shelter or greenhouse, laid flat on the crop in open field or tunnels, or vertically in open field to combat pests moving under the plant cover or close to the crop (carrot fly, cabbage fly).

After installation, it is necessary to check the tightness of the physical barrier.

For some techniques, the barrier must be removed before any other intervention.

Implementation period : On established crop
Spatial scale of implementation : Plot

Application of the technique to...

All crops : Sometimes difficult to generalize. This technique is only applicable to crops occupying limited areas. However, it can be applied to various open-field crops (carrot, turnip, cabbage), protected and greenhouse crops (cucumber, tomato…).

Effects on the sustainability of the cropping system

"Environmental" criteria

Effect on air quality : Increasing

phytosanitary emissions : DECREASE

Effect on water quality : Increasing

N.P. : DECREASE
pesticides : DECREASE
turbidity : DECREASE

Comments

Air and water quality

Reduction of pollutant transfers to water and air thanks to reduced insecticide use. The technique allows replacing insecticides. Their possible transfer becomes zero.

Fossil energy and GHG

Installation is manual, so there is a reduction in fossil energy consumption if the net replaces treatments. However, the impact of manufacturing is unknown. It is possible that nitrogen mineralization is stimulated and may cause N2O emissions.

Waste production

Nets must be recycled after use and represent quite large amounts of plastic.

"Agronomic" criteria

Productivity : No effect (neutral)

Production quality : No effect (neutral). No impact except if development of diseases (e.g., grey mold)

Soil fertility : Variable. If nets have a thermal effect, nitrogen mineralization may be stimulated (which is interesting in organic farming).

Water stress : No knowledge on impact. If the net used has a climatic effect, stimulation of evapotranspiration?

Functional Biodiversity : No knowledge on impact. Effect on movement of other insects and living organisms than the targets.

Other agronomic criteria :

Transmission of virus : link=|alt=green face size 10

The risk of transmission of viruses by certain aphids or leafhoppers is reduced.

Microclimate : link=|alt=red face size 10

Microclimate problem favorable to diseases.

"Economic" criteria

Operating costs : Increasing

Requires investment depending on the chosen barrier and its quality :

Reusable polyethylene nets 2 to 3 years: 0.6 to 0.8 euros/m².
Polyamide nets single use: 0.3 to 0.4 euros/m².

Mechanization costs : Decreasing

Physical barrier installation is manual thus reducing fuel consumption if treatments decrease.

Margin : Variable

This technique increases crop protection costs compared to chemical protection, notably due to required labor. It is therefore often implemented in organic farming, where product valorization helps limit the effect on margins.

"Social" criteria

Working time : Decreasing

Decreasing if the net replaces one or more sprayer passes.

Peak period : Increasing

Installation time is relatively significant.

Effect on farmer's health : No knowledge on impact

However, increased work difficulty, in greenhouse and shelter, when barriers cause temperature rise.

Observation time : No effect (neutral)

As with chemical treatments, net installation must be well timed relative to the target pest cycle.

Favored or disadvantaged organisms

Favored pests

Organism	Impact of the technique	Type	Details
weeds	STRONG	weeds	The presence of nets creates a microclimate favorable to the development of weeds (increased temperature and humidity)
vegetable crop flies	STRONG	pest, predator or parasite	If the net is placed on soil infested with pupae, or if flies manage to penetrate under the net, the technique favors fly population development by a confinement effect

Disadvantaged pests

Organism	Impact of the technique	Type	Details
Tuta absoluta	STRONG	pest, predator or parasite	The effectiveness of the technique depends on mesh size (it must be adapted to the targeted pest) and the tightness of the device
cabbage fly	STRONG	pest, predator or parasite	Strong effectiveness even if technique used alone. However, effectiveness depends on mesh size (must be adapted to the targeted pest) and device tightness
vegetable crop flies	STRONG	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness. It is possible to use vertical nets or nets on hoops to protect brassica crops against cabbage root fly (Delia radicum), which flies close to the ground
noctuids of vegetable crops	STRONG	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness
flea beetle	MEDIUM	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness
aphid	MEDIUM	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness
stink bug (pest)	STRONG	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness
thrips of vegetable crops	LOW	pest, predator or parasite	Effectiveness depends on mesh size (must be adapted to targeted pest) and device tightness

Auxiliaries disadvantaged

Organism	Impact of the technique	Type	Details
Predatory and granivorous arthropods	STRONG	Natural enemies of pests	All predator arthropods moving by air (hoverflies, ladybugs, lacewings…) are disadvantaged by the technique

For more information

Against cabbage flies in organic farming, vertical nets as a protection method
-Picault S.CTIFL, Technical brochure, 2008Infos CTIFL, n° 244, 36-40. To access the brochure see link

Physical anti-insect devices
-French Plant Protection Association, coordination : Jean-Louis Bernard. French Plant Protection Association. AFPP guide working group, provisional document as of 12 February 2011, Technical brochure, 2011. AFPP link

Practical guide for designing vegetable cropping systems saving phytopharmaceutical products. Technical sheet T21.
-Launais M., Bzdrenga L., Estorgues V., Faloya V., Jeannequin B., Lheureux S., Nivet L., Scherrer B., Sinoir N., Szilvasi S., Taussig C., Terrentroy A., Trottin-Caudal Y., Villeneuve F. Ministry in charge of agriculture, French Agency for Biodiversity, GIS PIClég., Book, 2014. To access the Guide see link

Overview of alternative methods : protective nets
-Prisca S., Picault S.CTIFL, Technical brochure, 2016. To access the brochure see link

Flea beetles, puncturers of crucifers
-Bosse-Platière A. (Terre Vivante). Terre Vivante website, page visited 26/01/2012, Website, 2012. Link

Vegetable sheets : How to use veils and nets in organic market gardening?
-Vetabio. Vetabio, Technical brochure, 2011. see link

Diseases and pests of open-field vegetables in Brittany
-Estorgues V. (Chamber of Agriculture of Finistère, coordination); vegetable advisors of the 4 chambers of agriculture of Brittany. Chambers of Agriculture of Brittany, Book, 2005

Implementation of "insect-proof" nets in greenhouse crops; impact on choice of covering materials and ventilation systems, Plastic and horticulture days.
-Lagier J.INRA, Non-peer-reviewed journal article, 2002. see link

Alternative methods in vegetable crops
-Oste S., Legrand M., Roy G. (FREDON Nord Pas-de-Calais). Phytoma n°613, March 2008, pp26-29, Press article, 2008

Keywords

Pest control method : Physical control
Mode of action : Avoidance

Type of strategy regarding pesticide use : Substitution

Photo gallery

Appendices

S'applique aux cultures suivantes

Favorise les bioagresseurs suivants

Défavorise les bioagresseurs suivants

Défavorise les auxiliaires

Predatory and granivorous arthropods

Implementing Physical Anti-Insect Devices

Contents