Combiner plantes pièges et plantes répulsives :Push-pull" strategy
The push-pull strategy consists of making the crop repellent to pests (push) while simultaneously attracting them (pull) to areas where they can be managed by physical or chemical destruction, trapped, or simply diverted from the crop at the sensitive stage (see sheet on trap crops).
Overview
Characterization of the technique
Description of the technique:
This combination generally appears more effective than the two elements separately. Repellency can come from: the appearance of the crop (color, size, shape), the presence of repellent intercrop plants, or the spraying of repellents (synthetic repellents, volatile compounds from non-host plants of the pest, odors emitted by natural predators, pheromones, etc.). The attractive zone may consist of visual traps, attractive plants possibly treated with pheromones or other natural or synthetic substances. Note that in known applications of the technique, some repellent plants also have an attractive effect on beneficials whose action is sought to be promoted in the plots and/or on the trap plants at the border.
Example of implementation:
The two (only) classic large-scale implementation examples concern cotton and maize or sorghum in East and Southern Africa (Australia, USA?). Cotton: control of the noctuid moth using extracts of neem seeds (repellent) and trap plants on the plot border such as cowpea or maize. Maize and sorghum: control of the stem borer via introduction of Desmodium uncinatum as an intercrop (repellent) and Pennisetum purpureum or Sorghum vulgare sudanense as attractive trap plants around the plots (which serve as hosts but do not allow full larval development).
In vegetable farming, more or less conclusive trials have been conducted by interspersing rows of tagetes (French marigold) among tomato plants for a repellent effect on soil-damaging nematodes. This less complete example than a full push-pull system seems interesting in two respects: it illustrates the possibility of extending the push strategy beyond insects alone and it develops in the soil compartment targeting root systems.
To combat different species of vegetable flies, it appears that planting a row of maize around the plot has an attractive power, the flies coming to ‘rest’ on this support. This ‘pull’ example is given because it illustrates a situation where attractiveness is not directly linked to the pest’s search for food.
Details on the technique:
They would require having a comparative scale of the degree of repulsion or attraction between pairs of species for some major pests. For flying insects actively seeking their host, choice test devices in flight tunnels could yield good results.
Implementation period On established crops, during the cropping season or the critical sensitivity period.
Spatial scale of implementation Plot and its immediate surroundings.
Application of the technique to...
All crops: Not generalizable as is, but a thorough knowledge of the feeding preferences of generalist pests would highlight the range of situations where progress seems possible. Any feeding or behavioral preference a priori opens opportunities for deploying this approach.
The only large-scale application of this strategy currently concerns the protection of maize and sorghum against the stem borer (Chilo partellus) in East and Southern Africa (in South Africa, mainly the "pull" component is applied as farmers do not plant intercrops). However, a push-pull strategy based on repellents and/or attractants can potentially be adapted to many crops. More than the crops, it is the characteristics of the pest (specificity, mode of movement) that may limit generalization.
All soil types: Easily generalizable
No known interaction with soil type.
All climatic contexts: Easily generalizable
In very dry environments, possible competition for water between the repellent plant in association and/or the border trap plant.
Effects on the sustainability of the cropping system
"Environmental" criteria
Effect on air quality: Variable
Phytosanitary emissions: DECREASE
GHG emissions: VARIABLE
Effect on water quality: Increasing
Pesticides: DECREASE
Effect on fossil resource consumption: Variable
Fossil energy consumption: VARIABLE
Pollutant transfer to water (N, P, phytosanitary ...):
As the technique reduces pesticide use which are transferred to water. Only trap zones are possibly treated. The attractive or repellent substances that may be sprayed are generally non-toxic (pheromones, essential oils, etc.).
Pollutant transfer to air (N, P, phytosanitary ...):
As the technique reduces pesticide use which are transferred to air. Only trap zones are possibly treated. The attractive or repellent substances that may be sprayed are generally non-toxic (pheromones, essential oils, etc.).
Fossil energy consumption: Variable
The change depends on the mode of application of stimuli to insects either via one or more sprayings, or via the planting of service plants (repellent or trap).
GHG emissions: Variable
Regarding CO2 emissions, the change varies depending on either the spraying passes of stimulating substances or the mode of planting trap and/or repellent crops.
"Agronomic" criteria
Productivity: Variable
In the case of introducing repellent plants into the plot, there may be a slight yield reduction. However, these plants are sometimes valorized (case of Desmodium used as forage in East Africa and which as a legume improves nitrogen balance, or some border trap plants such as Sudan grass and Napier grass which are also forages). However, the area occupied by non-directly productive plants must be subtracted.
Soil fertility: Increasing
Possible interactions between crop and service plants (repellent or attractive). Trap plants or associated crops cover the soil and limit erosion. If they are legumes, they fix nitrogen (case of Desmodium associated with maize).
Trap or associated crops cover the soil and reduce the risk of soil erosion. Border trap plants also constitute anti-erosion hedgerows.
Water stress: No knowledge on impact
Possible interactions between crop and service plants (repellent or attractive).
Functional Biodiversity: No knowledge on impact
In case of reduced insecticide use. However, the effect of various substances that may be applied on other organisms than the targeted ones needs to be studied (especially on insects, notably beneficials and pollinators). However, the push-pull effect can also be to move pollinators away from treated areas (case of rice in Madagascar where pollinators are attracted to floral resources of untreated borders).
Risk of development of insecticide resistance: Decreasing
Elements of push-pull strategies are generally considered non-selective. In case of pest destruction by insecticides, very targeted applications at potentially high concentrations reduce opportunities for insects to develop resistance. However, some attractants are coupled with insecticides and in this case, resistance development is possible.
"Economic" criteria
Operating costs: Increasing
This effect depends either on the cost of planting and destroying service plants, or on the cost of spraying repellent or attractive substances. Costs seem generally higher than those related to insecticide use but economies of scale may be expected with adoption rate of the method.
Mechanization costs: No knowledge on impact
This effect depends either on the cost of planting and destroying service plants, or on the cost of spraying repellent or attractive substances. Planting repellent plants can be a barrier to mechanization or vice versa (cf. South Africa).
Fuel consumption change depends on the mode of application of stimuli to insects either via one or more sprayings, or via planting service plants (repellent or trap).
Margin: Variable
Increase if an associated crop is valorized. On the other hand, it generates infrastructure likely to create a nearby reservoir and continuum for certain diseases (virus of dwarf yellowing) or pests different from the targeted one.
"Social" criteria
Working time: Variable
Change depends on the mode of application of stimuli to insects either via one or more sprayings, or via planting service plants (repellent or trap). Planting repellent plants is considered a barrier to mechanization or vice versa (cf. South Africa).
Observation time: Variable
A push-pull strategy implementing repellent and attractive plants does not a priori require additional observation time, or even less than the observation time required for triggering insecticide treatments. In case of application of substances (either repellent, attractive or biocidal in case of treatment on trap plants), it depends on how sprayings are triggered (observations, regular frequency).
For further information
- Odors to protect crops against insect pests - Kerguntueil A. (INRA, IGEPP unit) University work, 2013, Thesis available: link, Summary: link
- Crop protection - Deguine J. P. (CIRAD); Ferron P. (INRA); Russel D. (University of Melbourne) Quae Editions, Book, 2008, pages 138-139.
- Push-pull technology - Collective, Wikipedia, Website, 2011, link page visited 11/03/2011.
- The use of push-pull strategies in integrated pest management - Cook S. M. (Rothamsted Research); Khan Z. R. (International Center for Insect Physiology and Ecology, Kenya); Pickett J. A. (Rothamsted Research). Annual Review of Entomology, Peer-reviewed article, 2007, 52:375-400.
Keywords
Pest control method: Cultural control
Mode of action: Mitigation
Type of strategy regarding pesticide use: Redesign
