Key learning outcomes
- Understand the steps that should be taken prior to use of herbicides for weed control
- Understand the types of herbicides (soil residual vs contact) and how this effects the usage
- Be introduced to herbicide resistance, and the risk factors that can accelerate it’s development in field populations
Whilst chemical control continues to be a mainstay for the majority of growers, having a better understanding of the principles behind the use of herbicides can ensure that appropriate steps to steward them are being made. Optimising the efficacy of these important compounds is vital to delivering a sustainable weed control programme.
Chemical methods of weed control
This is a presentation developed by Philippe Delval, ACTA, France. The video is about 11 minutes 30 seconds long.
Comments, notes and resources referenced in the video
Choosing plant protection products with the lowest risks
When chemical interventions are necessary, the producer has the possibility of choosing, among the authorized specialties *, those which are most specific to the problem (cf. targeted control) and which present the least risks in relation to human health and organisms. non-target and the environment. You can find characteristics of the on the PPDB database
Choosing the most specific plant protection products possible: targeted control
The targeting of the control methods consists in using more specific means against pests and therefore involves a precise diagnosis but also a forecast of phytosanitary risks.
IWMGAME [arable and perennial crops]: Several cards represent chemical control methods. These cards describe the different types of herbicides available on arable and perennial crops. They have preventative or curative effects depending on the herbicide. You can play it at different periods depending on the herbicide as well. They are effective on specific weeds. Herbicides always provide negative side effects.
Reasoning for the application
Adapting the level of protection to economic challenges
It is possible to reduce the level of protection for a crop when its outlet does not require an irreproachable level of quality, such as for animal feed for example.
Reasoning the advisability of phytosanitary treatments
Optimizing the positioning (intervene at the right time) and the number of treatments (treat only if necessary) allows effective protection of the crop while limiting the quantities of plant protection products applied in the fields.
Choosing the optimal period for applying plant protection products
The implementation of a phytosanitary treatment must be reasoned according to 4 essential parameters: the stage of development of the crop, that of the targeted pest, the meteorological conditions and finally the periods of activity of the useful organisms.
Adapting the treatment doses to the amount of vegetation
Reductions of the applied quantities may be considered in situations with lower risk in terms of disease or pest pressure and vegetation development under certain material and meteorological conditions.
Using adjuvants during phytosanitary treatments
The use of adjuvants must be considered on a case-by-case basis and their effectiveness depends on different characteristics (product, target plant).
Choosing and adjusting your spraying equipment
The choice of a well-adapted equipment (sprayers, nozzles) and the correct adjustment of it (pressure, forward speed, spraying flow rate) make it possible to reduce the quantities of phytosanitary products applied per hectare by reducing the waste and by making it possible to modulate the dose (to be implemented with precautions).
Maintaining and having your sprayer checked
The condition of the plant protection product application equipment determines the effectiveness of the treatments, the safety of the handler and the risks of environmental pollution.
Choosing and adjusting your spraying equipment
The choice of a well-adapted equipment (sprayers, nozzles) and the correct adjustment of it (pressure, forward speed, spraying flow rate) thus make it possible to reduce the quantities of phytosanitary products applied per hectare by reducing the waste and by making it possible to modulate the dose (to be implemented with certain precautions).
Testing your sprayer during spraying evaluation benches
It is possible to test the efficiency of your sprayer during spraying evaluation tests. This can allow you to adapt your practices or even be useful before choosing a new sprayer.
Regulating the flow of the sprayer according to the speed
It is possible to regulate the flow of spray mixture according to the forward speed of the material thanks to a “groundspeed related application rate“ system. The volume / ha remains constant regardless of the variations in engine rotation speeds for a given gear ratio.
Limiting areas of overlap by cutting sections of the sprayer
The section cut-off makes it possible to better manage the opening or closing of part of the boom on spraying equipment. This GPS-assisted device limits the overlap areas.
Optimizing your passages thanks to a GPS guidance or autoguiding system
To optimize tractor passages in the field and limit gaps or overlaps between each round trip, it is possible to use GPS assisted self-guidance.
Use agricultural drones to carry out a treatment
Agricultural drones can be used to carry out treatment: spraying in general or even releases within the framework of biocontrol.
Limiting drift during application using collection-retrieval panels
The recovery panels are located under the spraying system and their purpose is to confine the spray pattern and to recover the particles that do not reach the plant.
Limiting drift during application using anti-drift or large gauge nozzles
To avoid drift, it is essential to control material and climatic factors during application. The limitation of the drift also makes it possible to better target the spraying on the area to be treated.
Reducing the quantities of products used by localized application
A localized application of phytosanitary products is a good way to reduce the quantities used. This may involve locating the application in the row, or even targeting only pest outbreaks.
Optimizing the application of herbicides using wetting equipment
It is possible to achieve savings in herbicides by using equipment which applies the product in direct contact with the weeds to be destroyed. For the practice to be selective, the crop must be of a lower height than the plants to be eliminated. Two types of application: by cords or by roll.
Practicing mixed chemical / mechanical weeding in annual crops
Mixed weed control consists of implementing chemical weeding on the row coupled with mechanical weeding in the inter-row of row crops. Localized treatments (on the row or at the level of pest outbreak) make it possible to reduce the quantities of phytosanitary products applied per hectare.
IWMTOOL: Four factsheets are dedicated to describing chemical uses:
In an integrated weed management strategy herbicides can be used to support other nonchemical measures. Different herbicides are focused on one of the growth stages of the weeds, on specific weed groups and either on establishment or growth of the weeds. Herbicides are basically divided in three groups based on timing of application: pre-emergence, post-emergence or preharvest herbicides.
Patch and band spraying can help to reduce the use of herbicides. Apart from the benefits for the environment, a major reason to reduce herbicide use is to prevent herbicide resistance. If no selective herbicides are available, inter-row application of nonselective herbicides may pose an alternative in combination with mechanical tools capable of intra-row weeding (see mechanical weeding). Site-specific herbicide application/ precision spraying also offers an opportunity for further reductions in herbicide use, but these technologies are still under development.
IWMGAME [arable & perennial crops]: Two cards represent localized spraying. You can play them to decrease side effects of the use of chemical products.
One card represents “agri-environmental measures”. It can only be played during the intercropping period and may gain money units. The downside of this card is that the use of chemical cards are prohibited during following cropping periods.
Preventing the appearance and development of resistance to biocontrol products
The objective of resistance management is mainly to maintain the effectiveness of products over time, i.e. to use them wisely so as not to favor the development of resistance which would lead to a reduction in their effectiveness or even cause ineffectiveness.
Anti-resistance strategies = the diversity of control methods offered by integrated pest management should be taken as a whole as a strategic solution. Re-design the system by diversifying the solutions provided in time and space.
One website from committee dedicated to anti-resistance strategies https://www.hracglobal.com/