Treatment Of The Crop

Step 1: Implement a Pre-Application Plan

Crops attract a great variety of pests and diseases that cause external and internal damage to the crop and plant.

Although some pests and diseases in a field or orchard are controlled manually, the greater majority are controlled using chemicals. The crop protection application methods covered in this unit standard refer to the chemical control of pests and diseases.

The term Crop Protection Manager is used in this learning material when referring to the person responsible for the implementation of the crop protection program. In practice, this function may be fulfilled by the farmer or the general manager of the farming operation.

Proper planning for protecting crops from pests and diseases is critically important. Poor planning could result in financial losses due to a reduced crop or a poor-quality crop, and possible damage to the health of trees. Time and money will also be lost if incorrect or unnecessary applications are made.

Planning entails two steps. Firstly, a crop protection program is compiled to control the pests and diseases commonly found in the area where the farm is located. The crop protection manager decides which chemicals to use, in what concentration to apply the chemicals, and the schedule of application. This information is incorporated in a crop protection program, which is normally compiled before the start of the season and strictly adhered to as the season progresses. There may be minor changes made during the season if circumstances in the field change.

Pre-application planning is done before each stipulated application on the crop protection program and may be best accomplished by using a simple checklist. We will look at the checklist at the end of this session, after considering the various components of this planning process.

A proper plan for the application of plant protection products, a thorough understanding of the following components is required:

• Plant protection products
• Application methods
• Application equipment
• Health and safety

Step 2: Know your Plant Protection Products

The first step in the pre-application planning is to identify the product indicated in the crop protection program. Plant protection products are generally classified as insecticides, fungicides or herbicides.

Plant Protection Product Registration

Only chemicals that have been registered with the National Department of Agriculture in accordance with Act 36 of 1947 are permitted for use in South Africa. These products are listed in the following Government publications, which are updated from time to time:

• Guide for the Control of Plant Pests
• Guide for the Control of Plant Diseases

There is a section in these publications covering citrus pests and diseases where remedies for specific problems are listed. If these books are not available, the crop protection manager may need to consult a representative of one of the agrochemical companies.

Plant Protection Product Identification

The first step in identifying a product is to consult the chemical label. All chemicals must, by law, have a label on the container when it is supplied to the end-user.

The following information appears on the product label:

• Full instructions on how to use the chemical are indicated, together with detailed information on the uses for which the product is registered. The instructions must be read carefully and adhered to strictly. This will ensure that the best results are attained, that the safety of the user and others is not at risk, and that the environment is not excessively harmed. It is an offence to use a chemical in a manner for which it was not registered.
• A physical description of the product is supplied, including its colour and whether it is in fluid, powder or granular form. The crop protection manager should inspect the chemical in the container to ensure that it answers to this physical description. If not, the container and its contents should be discarded in the prescribed manner.
• The chemical composition of the product is indicated on the label.
• The toxicity of the product is indicated, along with instructions for its safe handling.
• The pre-harvest interval (PHI) of the product is indicated. The PHI, also known as the Withholding Period, refers to the period after application of a chemical treatment during which time the fruit may not be harvested. PHI’s vary considerably from chemical to chemical and need to be checked by the crop protection manager when he compiles the crop protection program. It must also be checked as part of the pre-application planning.
• The product expiry date is stated, being the date on or before which the chemical should be used. Chemicals should be used before the expiry date to make sure that the chemical is still effective.

Note: All chemicals leave a residue on the fruit. There are very specific regulations regarding the chemical residue levels that are allowed, especially if they are exported. Minimum residue levels (MRL’s) are prescribed for all plant protection products registered with the Department of Agriculture. The PHI indicates the period during which the chemical residue will be too high and beyond the regulatory limits. During this time, the fruit must not be harvested.

Plant Protection Product Availability

The crop protection program indicates the concentration at which the product must be used, and the quantity required per tree or hectare. It may also indicate the total quantity of a chemical required for the application, but if not, the crop protection manager can calculate this by using the information provided.

The crop protection manager must ensure that a sufficient quantity of the chemical is available before application commences. In this regard, he needs to consult with the person in charge of procurement (buying) and the inventory manager.

Step 3: Prepare the Equipment

Once the method of application has been determined, the equipment required for the application is identified and checked. Application equipment and measuring equipment is required during most applications. The crop protection manager determines the equipment requirements by considering:

The area or number of trees to which the chemical must be applied.

The time in which the application must be completed.

The number of farm workers available.

Click here to download a handout that explains the equipment used for chemical applications.

Once the equipment requirements have been determined, the crop protection manager must consult with: 1) the person responsible for mechanical equipment to ensure that sufficient equipment (tractors and spraying machines) will be available. 2) The person responsible for the stores to ensure that sufficient measuring equipment and chemicals are available.

The crop protection manager must also ensure that all equipment is in a good working order, as breakdowns during application can cause delays that may result in ineffective pest and disease control. Spraying machines and tractors are normally serviced before the start of a season but must be checked regularly. The crop protection manager must consult with the person responsible for mechanical maintenance in this regard.

The application equipment that is required is specific to the application method.

Click here to download a handout that explains the calibration of equipment for crop spraying.

Step 4: Mixing the Chemicals

Mixing CPPs for crop protection applications correctly and accurately is essential. If a too-low concentration of CPP is used, the crop will not be protected effectively. On the other hand, if the concentration is too high, it can result in overdosing on animals and damaging the crop. A financial loss is unavoidable!

Mixing CPPs does not only involve measuring correct quantities and combining the ingredients. The person responsible for the mixing must be aware of the nature of the CPPs that is being handled, the safety requirements for working with such CPPs, the appropriate equipment that is required, and the correct mixing procedure.

Mixtures are normally mixed immediately before application and should not be stored in mixed form. It is therefore essential that the person responsible for mixing the CPPs has all the required CPPs, equipment and information available to complete the task without delay.

Apart from the chemicals, the following items are required during the mixing process:

• Protective clothing.
• Measuring equipment.
• Mixing equipment.

Clean water and a bar of soap must also be readily available in case a person’s skin is contaminated with chemical spillage. A person must also wash up after handling the chemicals.

Calculating the Quantity of Chemicals or CPPs Required

To measure the correct quantity of a liquid chemical, an assize-measuring container is required. To measure wettable powders or granules, a scale weighing accurately, is needed

Electronic scales generally allow for more accurate measurements, but hand scales can also be used. It is however essential that scales are serviced and calibrated regularly. Scales must be zeroed carefully before the chemicals are weighed.

The standard practice for tree crops is that recommendations for the concentration of crop protection CPPs to be made in millilitres (ml) or grams (g) per 100ℓ of water. This is also the way it is shown on the crop protection program.

Below are a few examples of notations:

The person responsible for mixing the spraying material needs to have a thorough understanding of this notation.

To mix the above spraying materials, one must calculate the quantities of the various ingredients depending on the total quantity of spraying material required. The amount of water is normally used as a basis, i.e. if 500ℓ of spraying material is required, 500ℓ of clean water will form the basis of the calculation.

Using the examples above, the calculation will be as follows:

Mixing Procedure

The mixing procedures for different pesticides differ. In some cases, it may be required that the compounds are pre-mixed in a separate container. In general, the procedure is to fill the spray tank halfway. The measured pesticide is added (the measuring equipment used can also be rinsed in the tank) and the tank is then filled to the correct level. Stir thoroughly. The pesticide label will specify the procedures to be followed. Read these carefully and apply these procedures.

As an example of a mist blower, the following steps are taken:

• Measure the chemical ingredients accurately, using the appropriate equipment (a size measuring container for liquids and a weighing scale for powders or granules).
• Add the chemical ingredients to a 10ℓ bucket of clean water.
• Mix thoroughly.
• Fill the spray tank half with water.
• Add the 10ℓ mixture to the spray tank on the mist blower and mix.
• Add the remainder of the water to the spray tank, stirring the mixture continuously.

Click here to view a video that explains mixing your pesticide spray.

Click here to view a video that explains mixing and filling your sprayer.

Step 5: Pre-Application Checklist

A pre-application checklist can be compiled when working with chemicals. The format of the pre-application checklist is not standard, and different farms may use different methods or formats for this purpose.

It is however essential that this type of information is recorded in a format that is easy to use for the persons responsible for the application. The checklist must contain all the necessary information to avoid confusion and the need to consult various records.

A pre-application is prepared for every application that must be done according to the crop protection program. The pre-application checklists can then be used during the application to verify that the application is done correctly.

After the application has been completed, the pre-application checklist is filed with the application reports as part of the records kept for the farm.

Click here to download a handout that explains an example of a pre-application checklist.

Step 6: Application of Chemicals

This session focuses on the application of agrochemicals or CPP’s after the pre-application planning has been done and the CPPs have been mixed for application.

Influence of Climatic Conditions

Climatic conditions play an important role when it comes to the application of CPP’s, especially when the product is applied by way of spraying.

Wind: Foliar sprays should not be applied when wind speed exceeds 12 km/h. High wind speeds will negatively affect spray coverage of the tree, which could result in poor control of the target pest or disease. Excessive wind will also result in spray drift, which could damage other crops, pollute water supplies and harm the environment.

Rain and dew: Trees must be dry before foliar sprays are applied. If trees are wet, spraying material is diluted and less effective. One cannot spray at all while it is raining. As a rule, six hours of dry weather is required after an application. If more than 10 mm of rain falls before this time, the application should be re-applied.

Temperature: Most CPP’s are applied during the summer months. Oil sprays must not be applied if temperatures are expected to exceed 30˚C. It is for this reason that oil sprays are often applied at night in warmer areas. It is very risky to apply oil under very hot conditions as fruit burn will occur. Some products are also sensitive to ultraviolet light (UV) and should also be applied after nightfall.

Application Methods

Plant protection products can be applied in various ways. The manner of application should be stated on the crop protection program. There are many variations of application methods. The decision on which method to use depends on the specific requirements and purpose.

Application methods for trees/ orchards include:

• Foliar spray application
• Trunk application
• Soil drench

Foliar Spray Application

The most common method of applying insecticides and fungicides to plants (trees on an orchard farm) is by applying a foliar spray. This means that the spray material is applied to the leaves of the trees. There are three main types of foliar spray applications, being:

• Light cover spray
• Medium cover spray
• Full cover spray

Click here to view a video that explains spraying pesticides downwards using a knapsack sprayer.

Trunk Application

Some chemicals can be applied directly to the trunk of the citrus tree. These chemicals are systemic, meaning that they are absorbed through the bark and being translocated within the tree to the area where they are required.

Click here to view a video that explains the trunk application of the pesticide demonstrated.

Soil Drench

This method implies the diluting of a chemical in water and pouring it onto the soil around the trunk of the tree where it is absorbed by the roots and translocated within the tree. These chemicals are also systemic. Certain chemicals can also be applied through a drip irrigation system which allows its uptake by the roots.

Crop Treatment Methods

Spraying and dusting, in agriculture, are the standard methods of applying pest-control chemicals and other compounds. In spraying, the chemicals to be applied are dissolved or suspended in water or, less commonly, in an oil-based carrier. The mixture is then applied as a fine mist to plants, animals, soils, or products to be treated. In dusting, as an alternative method, dry, finely powdered chemicals may be mixed with an inert carrier and applied with some type of blower. Dry granular materials also have been used instead of dust or sprays where adequate coverage can be obtained. (See also crop duster). In fumigation, gases or the vapours of volatile compounds are held in contact with the materials to be treated—grain in a tight bin, for example.

Sprays and dust are used to control insects, mites, and fungous and bacterial diseases of plants; insects, such as lice and flies, on animals; and weeds, by means of chemical weed killers or herbicides. Sprays and dust may also be used for such special purposes as applying mineral fertilizers, increasing or decreasing fruit sets, delaying the dropping of nearly mature fruits, and defoliating and vine killing to facilitate the harvest of such plants as cotton or potatoes.

prays have advantages over dust in their ability to adhere to and spread over treated surfaces. Spreading-sticking agents or surfactants are commonly added to spray mixtures to increase the adhesion and wetting of waxy surfaces. These wetting agents decrease the tendency of water to collect in drops and permit the chemical solution to spread over a leaf in a very thin film, bringing the spray chemical into maximum contact with the fungi, bacteria, insects, or mites to be controlled. There has also been an increase in the use of air sprayers or “wet dusting.” The use of a concentrated spray distributed in the airstream from a powerful fan combines many of the advantages of both spraying and dusting.

Click here to view a video that explains the demonstration of a crop sprayer.

Step 7: Post-Application Procedures

After the application of the Chemicals, the treatment record needs to be completed and filed.

Click here to download a handout that explains the treatment record.

Once the CPP’s have been applied in the prescribed manner, certain steps must be taken to clean, maintain and store the used equipment and to ensure that no further contamination can take place. In this session, we will look at these post-application procedures.

The following procedures must be followed to complete the application, some of which are discussed in more detail in the remainder of this session:

• Clean all mixing and application equipment thoroughly and store it in the prescribed manner.
• Clean all protective clothing and equipment thoroughly and store them in the prescribed manner.
• Collect and dispose of empty containers and other waste products correctly, as discussed in section 6 of session 2, and ensure that no empty containers are reused.
• Apply personal hygiene and safety.
• Notify CPP manager of the completion of work.

Cleaning of Equipment

Once the spraying operation has been completed, all machinery must be washed with clean water and stored for future use.

If spraying equipment is not cleaned properly after use, the danger of contamination remains, and people, animals and the environment may be placed at risk. In addition, certain CPPs are corrosive and spraying equipment that is not properly washed may be damaged.

Spraying machines must be washed in an area with adequate, safe drainage such as a filling point with a good French drain and at least 50m away from any water sources.

• Once parked at the filling point, remove the filter, normally situated near the pump.
• Rinse the filter with clean water so that all residues are removed.
• Fill the spraying tank with water while the agitator (mixing mechanism) is running. Water will pour through the open filter rinsing the tank. The tank is considered clean only once all pesticide residues have been removed.
• Wash the outside of the spraying machine with a cloth to remove all spray residues.
• Only now the spraying machine can be parked in its designated area.

All other equipment, such as brushes, knapsacks, mixing equipment, etc., must be washed with appropriate liquid soap and well-rinsed in a suitably well-drained area.

Personal Hygiene Post Application

On completing the spraying task, all persons involved should bathe and dress in CLEAN clothing. Do not put on the clothes that were used for the spraying operation unless they have been laundered properly. Wash body and equipment away from water sources and home every time after using pesticides and wash after each use.