Criteria for control

Stewardship is vital for the sustainable use of agrochemical products

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Crop protection products (CPPs) generally refer to the group of agricultural chemicals called herbicides, fungicides, insecticides, and nematicides. These are biologically active products aimed at controling pests (insects and nematodes), diseases (fungi, bacteria) and weeds in crops.

CPPs are strictly regulated (ACT 36 of 1947) in South Africa. To be used safely and effectively, CPPs must be handled and used in accordance with the manufacturer’s recommendations. Otherwise they may be harmful to people, animals and the environment.

Safe, effective CPP forms part of sustainable agriculture, which requires economically viable, environmentally friendly and socially acceptable practises. CPP best practises form part of a good integrated crop management plan (also referred to as good agricultural practises or GAP).

Choice of CPPs

CPPs are formulated to optimise the efficacy, safety and stability of the chemical. Many different formulations exist, but the basics are either liquids and powders or granules. In most cases the formulated products are mixed or diluted with water before use.

Some good product choice practices:

Keep an updated list of products that are registered for the crops you grow.

Ensure that only CPPs registered in South Africa are applied appropriately as recommended on the label

Ensure that only technically trained people are responsible for choosing which plant protection products to use. Competence can be demonstrated via official qualifications or specific training course attendance certificates.

Plant protection residue analysis

If a producer is intending to trade the produce in a market where the maximum residue levels (MRLs) are stricter than those of the country of production, the producer or the producer’s customer must be able to demonstrate that these MRLs have been taken into account during the production cycle (i.e., modification where necessary of plant protection product application regime (pre-harvest interval) and the use of residue testing results).

Application is key

Mixability of remedies

Not all remedies can be mixed. Compatibility is indicated on the label under restrictions. Alternatively, contact a certified crop protection agent or CPP supplier. In some instances, two remedies may be mixable in terms of physical compatibility, but their biological mode of action can be affected in the process, rendering both products ineffective.

Never mix remedies in concentrated form; each remedy should be diluted separately before being added to the spray tank. This is especially applicable to wettable powders where it is necessary to make a suspension using a small amount of water before slowly adding it to the spray tank while stirring. Always read the label carefully for mixing instructions.

Water quality

The general guideline is to use clean water of a high quality. This is not always possible, due to water containing too much suspended soil and organic matter, which can adversely affect the efficacy of a product. Hard water containing high levels of calcium and magnesium salts (>500 ppm) can bind with the active ingredients of a product and often reduce efficacy. Adjuvants are available for the correction of water quality to ensure optimum efficacy but should always be applied according to the label.

Spraying equipment

Always consider equipment types, nozzles and droplets, calibration principles and thorough cleaning of the equipment after applications are made.

Spray application equipment is used to deliver the CPP to a target area, usually with water as the carrier. When selecting the equipment and nozzle type, always consider the product’s intended use. This information is usually found on the label.

Almost all types of application equipment use nozzles to deliver the CPP accurately. Ensure that the correct nozzle is selected for the intended product. Droplet size is one of the most important aspects of the effectiveness of any application. Droplet size is a function of the pressure and the type of nozzle used.

Advances in adjuvant technology may further enhance droplet deposition through its potential effect on droplet size. Spray nozzle problems typically manifest in changes in the rate of flow. The flow rate will increase as the surface of the orifice and/or internal vane or core begins to deteriorate. Increased flow rates or lower spraying pressures may also result in larger droplet sizes. When spray pattern uniformity is affected, streaks of uncontrolled weeds or the occurrence of pests or diseases typically develop. It is therefore vital to maintain and replace worn nozzles frequently.

Cleaning equipment during the season

Equipment should regularly be flushed with clean water, preferably once a day, to prevent chemical residues drying out on filters and in the nozzles. If changing products, decontaminate the sprayer. Follow label instructions when required. Even very small amounts of some products (eg sulfonylurea and growth-regulator-type herbicides) can damage susceptible crops if the unit is not thoroughly cleaned.

“Weather” to spray or not?

The weather is critical in determining effective CPP application. Farmers must decide whether the application can be made safely and effectively under prevailing weather conditions so as to avoid spraying under conditions that increase the risk of drift. Understanding how weather affects spraying and how it can be monitored can inform the decision-making process.

Consider local forecasts and consult the label for product specifications such as optimal application conditions, drying time, absorption rate and retention time. If conditions become too windy or too hot, or it starts to rain, stop spraying until conditions improve. Temperature, relative humidity, wind and rain can affect effective pesticide application significantly. Adhere to the following guidelines:

  • Spray when wind is steady and ideally at 2–15 km/h. Avoid variable or gusty wind conditions.
  • Avoid calm conditions – small droplets may remain suspended for long periods.
  • Look out for inversion layers.
  • Spray when wind blows away from sensitive areas.
  • Avoid spraying in temperatures above 28°C.

Safe handling

A few things need to be taken in to consideration regarding safe storage of CPPs. Products must be stored in accordance with local regulations, away from other materials, in a secure location appropriate to the products’ required storage temperature conditions. The storage location must be fire-resistant and well ventilated in the case of walk-in storage. Shelving must be made from non-absorbent material and the storage facility must be able to retain or deal with spillage. Access should be limited to workers formally trained to handle CPPs. Liquids must never be stored on shelves above powders. An up-to-date stock inventory or record of use should be readily available.

Handling

All workers who have contact with crop protection products must be subjected voluntarily to annual health checks. The accident procedure must be evident within 10 metres of the CCP storage facilities, which must be able to deal with accidental operator contamination. When mixing CPPs, follow the correct handling and filling procedures as stated on the label.

Empty containers

Re-use of empty CPP containers for purposes other than containing and transporting the identical product must be avoided. Disposal must occur without exposing humans or contaminating the environment. Only official collection and disposal systems must be used; empty containers must be adequately stored, labelled and handled according to the rules of a collection system.

Empty containers must be rinsed either by an integrated pressure-rinsing device used directly on the application equipment or at least three times with water. Empty containers need to be kept secure until disposal. All local regulations regarding disposal or destruction of containers must be observed.

Obsolete products

Obsolete CPPs must be securely maintained and identified and disposed of by authorised or approved channels. Surplus application mix or tank washings should be disposed without compromising food safety and the environment.

Equipment

Any equipment sensitive to food safety and the environment (e.g. fertiliser spreaders, crop protection product sprayers, irrigation systems, equipment used for weighing and temperature control), must be routinely verified and, where applicable, calibrated at least annually. The farmer should be involved in an independent calibration-certification scheme, where available.

Record of application

Record-keeping of all applications is not only required by certification bodies but is also an extremely valuable tool for the farmer to identify possible causes for good or poor control achieved with CPPs. All records must include:

  • Crop name and/or variety
  • Application location, date and time
  • Product trade name, active ingredient and quantity applied
  • Operator
  • Justification for application (was recommended by a trained and certified professional?)
  • Technical authorisation for application
  • Application machinery used
  • Conditions during application
  • Pre-harvest interval

While there is no guarantee against accidents, these best practices will go a long way towards eliminating incidents and minimizing risks should any problems arise.

Marius Boshoff, National Marketing Manager, Villa Crop Protection

 

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