|Manual on the Prevention of Post-harvest Grain Losses (GTZ)|
|8. Pest control using insecticides|
8.2.1 Surface Treatment Using Sprays
Sprays for storage pest control are prepared of EC- and WP-formulations (see section 8.1.3). They are used for surface treatment of both storage rooms and stacks of bags. They may also be used to spray produce during its transportation on conveyor belts into silos.
Depending on the height and size of the area being treated, manually operated or motor-driven knapsack or mobile pump sprayers with a capacity of between 10 and 100 litres are used The latter are particularly recommendable for the treatment of the roof area in large stores illustrations of some of the most
The operating instructions must be carefully observed when using the sprayers in order to avoid any incorrect treatment, health damage or damage to the sprayers. Regular care and maintenance of the sprayers is a matter of course. Thorough cleaning after use is particularly necessary.
220.127.116.11 Preparing the Spraying Liquid
The spraying liquid should always be prepared in a bucket and not directly in the sprayer. This ensures a thorough mixing.
For the preparation of EC formulations pour the required amount of water in a bucket (1), add the calculated amount of insecticide with a measuring cup (2) and thoroughly mix using a stick (3). The mixture should then be filled into the sprayer through the filter located on the insecticide tank (4) in order to avoid the clogging of the nozzle by din. EC liquids for spraying are stable mixtures (emulsions) which do not separate even after longer periods.
For the preparation of WP formulations weigh the necessary amount, mix it to a thick paste with a little water and then dilute by slowly adding the remaining water. Stir thoroughly with a stick. WP mixtures for spraying are instable suspensions and must be continually stirred while being applied to avoid the powder settling on the bottom of the spray tank.
18.104.22.168 Application of the Spray
Treatment should start immediately after the mixture is ready. If any liquid is left in the sprayer for a while, it should be mixed again before being applied.
It is important that the amount calculated and prepared for the area being treated (see section 22.214.171.124) is applied evenly. This requires some experience on the part of the user. In case of remaining or not sufficient spraying liquid quicker or slower operation should be performed the next time in order to treat the intended area.
When treating surfaces it is important to proceed systematically. On walls, even distribution is achieved by proceeding like shown in the following illustration:
In doing so, markers such as joints, beams or patches should be used as orientation points to avoid leaving any spaces or treating other parts twice. The standing distance from the wall should be chosen so that the spray covers the wall with the smallest possible droplets. This means in practice that it is necessary to stand closer to the wall when treating the upper parts and further away when treating the bottom:
Standing too far away from the wall will mean that the insecticide spray only partly reaches the surface of the wall. Standing too near to the wall means that a large amount of insecticide will be concentrated on a small area, causing the liquid to run down the wall. Both of these faults must definitely be avoided. The roof can be best treated from the bag stacks if no motor operated high pressure pump sprayer is available.
When treating bag stacks, the upper surface should be treated first, followed by the sides. Particular attention should be paid to the spaces between the bags in order to prevent untreated places.
The area underneath the pallets should be sprayed as far as the range of the sprayer being used permits.
The floor of a store is treated last working from the back of the store towards the doors.
Any remaining spray can be used for areas of particular risk, such as edges and gaps or empty pallets where insects may hide.
After treatment, the sprayer must be rinsed immediately using clean water. Special care should be given to the nozzle.
Fogging is performed using FOG (HN) formulations which are ready-for-use or suitable (heat resistant) EC-formulations mixed with diesel oil. They are applied using a thermal fogger. This method is particularly suited for dealing with flying pests, particularly with moths.
FOG formulations do not penetrate the stored produce. Therefore, fogging is of no use against infestation with beetles or larvae.
It is advisable to repeat fogging after about a fortnight in order to deal with any moths which have hatched in the meantime. The necessity of this procedure has to be checked before doing so.
The basic requirement for the success of fogging is that the active ingredient acts for at least 12 hours. This means that the store must be adequately sealed. If the fog is able to escape through holes, gaps, ventilation openings, doors etc. the treatment will not be very effective.
Application is simple. The FOG formulation has to be filed into the insecticide tank of the fogger. Place the machine in the ajar door of the store and start it.
Switch off any electric lights in the store before treatment as explosion might occur. Keep attention that the tube of the fogging machine is not too close to the bag stack as fire is possible. When fogging stops remove the machine and lock the door. Remember to put up warning signs!
In very large halls, it is advisable to enter the store with the fogger, switch it on and slowly move backwards to the exit in front of the cloud of fog. Wear a mask!
It is advisable to fog during the weekend when nobody is working. After treatment, ventilate the store well for several hours before entering.
Commercial smoke cartridges may be used if no thermal fogger is available.