7.4.2 Review of Application Methods, PPE, Calibration and Spraying

The previous sections have discussed the many aspects of selection, calibration and maintenance of application equipment. Having made sure your equipment is in good working order, there are several aspects to safe and effective application:

• Assessing the target
• Nozzle selection and setting
• Selection and use of appropriate personal protective equipment (PPE)
• Calibration
• Application technique: how to treat the target? 
  Where must the spray deposit be put …
  • pods & trunks?
  • shoots?
  • whole tree canopy?

First, select the right nozzle: if your sprayer has a variable hollow cone nozzle, what setting should be selected? Remember that “overkill” will result in high residues and harm to the environment … as well as wasting money.

Variable cone nozzle settings:

It pays to Calibrate 

Use the right amount of water (volume rate) and pesticide mixture. Ask yourself the questions: 

• how many litres can my sprayer tank hold?
• how many trees are treated per tank-load?
• how many tank-loads are required to spray the whole farm? 

An example of a label for an insecticide product used in a major cocoa growing country is shown below.

The label states that

• the recommended dosage is 0.5 L per ha,
• 125 ml should be used per sprayer tank- load for 0.25 ha, and
• two applications are recommended per year. 

No reference appears to be made to the volume application rate (VAR) or any standard tank capacity, but presumably refers to motorised knapsack mistblowers. 

Farmers might actually spray 0.25 ha with one load, but in order to do so correctly still requires a knowledge of how many tank-loads will spray a known area (typically perhaps, the whole farm). 

Since mistblowers generally have a 10-12 litre capacity (see section 6.4.1.), the VAR should be 40-50 L/ha. Some may claim that this is too complicated for farmers, but discrepencies will result in proportionate overdosing or underdosing of the product. 

The potential consequences include high residues and poor pest control respectively, so trainers, SSPs and certification staff MUST examine whether this is a common problem within their regions.