Granular baits

SAFETY FIRST! ALWAYS READ THE MATERIAL SAFETY DATASHEET (MSDS). WEAR GLOVES WHEN HANDLING. WASH YOUR HANDS THOROUGHLY AFTERWARDS. DO NOT EAT, DRINK OR SMOKE WHEN HANDLING PRODUCTS

Granular baits are pellets made from an attractive food matrix containing a low dose of pesticide.  

For example, the active ingredient in AntOff bait is fipronil at a concentration of 0.01 g/kg bound in a fishmeal matrix.

AntOff is available in two sizes to ensure the bait is not too large for smaller ant species. 

Granular baits are ideal for treating large areas and may be distributed, or "broadcast", in a number of ways such as granular bait spreaders, mechanical blowers and bait stations.

Whatever bait you are using - ALWAYS follow the manufacturer’s guidelines for bait application rates.

Two sizes of AntOff bait manufactured by Animal Control Technologies (© Allan Burne, Pacific Biosecurity)

It is important to regulate the amount of bait being distributed. If too little bait is put out you won’t kill the ants. If too much is put out, the bait will remain in the environment, potentially poisoning beneficial organisms, and you will have spent more money and time than you needed to. Regulating bait use can be achieved by measuring the amount of bait used in each spreader and the area treated.

Granular baits can be distributed by hand, but this is not recommended. It can result in patchy distribution, a waste of bait, and bait not reaching the ants.

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Manual spreaders

Often referred to as Scott spreaders (due to the name of a popular brand), a typical manual spreader features:
  • a hopper for holding the bait
  • a winding handle that agitates the bait and scatters it over the ground
  • an adjustable opening (aperture) that is used to control the amount of bait that is spread.

With the aperture set, the operator holds the trigger in and winds the spreader handle at approximately 60 rpm while walking at a normal pace (~6 km/h).

Manual bait spreader (© Allan Burne, Pacific Biosecurity)

Holding the trigger in for long periods of time can be tiring and uncomfortable for the operator’s hand.  Once the spreader has been correctly calibrated for the bait, a screw can be put through the trigger assembly to keep the trigger in the open position. It is best to drill a pilot hole first, to prevent the screw from cracking the plastic of the spreader.

Modifying the spreader

Some ant baits (particularly those used for little fire ants) can be light and fluffy and do not feed through spreaders evenly. If you find this is the case, the spreader may be modified to improve its performance.

There is a T shaped agitator at the base of the hopper, which can be pulled out easily. Wrap a cable tie around the spindle of the agitator and tighten it as firmly as possible. Cut the protruding end of the cable tie down so that there is about 25 mm remaining and replace the spindle. When the handle is turned, the cable tie will rotate with the spindle and should assist with the flow of bait.

The Hawai'i Ant Lab provides detailed instructions on how to do this.

Regulating bait use

First, figure out how much bait the spreader holds. To do this, fill a spreader with bait, then tip the bait out into a plastic bag or other lightweight container and weigh it. For example, a Scott spreader comfortably holds 1 kg of AntOff bait.

Work out the volume of the bait. Pour the bait you have weighed into a measuring jug or plastic bottle of known volume and record the volume of 1 kg of bait. For example: 1 kg of AntOff bait equates to 1.5 L. 

This information is useful for two reasons. Firstly, you can keep track of how much bait is being used in the field without having to weigh it. Secondly, used in combination with the area (in hectares) that needs to be treated, you will be able to regulate bait use according to the manufacturer’s instructions.

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Bait Distribution

 
Each spreader holds ~1 kg of bait and delivers it in a 2.5 m swath (© Warren Butcher & Allan Burne, Pacific Biosecurity (left) © Alex Cook (right)) 

The swath width (where the bait is spread) will be approximately 2.5 m. The bait is applied by walking in a straight line (transect) through the areas to be treated, spreading the bait evenly.

When a boundary is reached, the operator turns, takes one step into the next area to be treated and walks back the other way so that the new swath overlaps the previous one by about 25 cm.

It helps to mark the boundaries of the swathes in dense areas to ensure the right level of overlap. This can be use flagging tape or paint to mark trees.

Measuring distance and area

In order to apply the correct amount of bait to a given area it is vital to quantify the area to be treated. Distances can be most easily and accurately measured with the assistance of GIS, large scale tape measures and GPS units. If these are not available, approximations may be made by pacing.

    A pace is the distance between the heel of the back foot and toe of the leading foot when taking a step forward. 

The average male pace length is approximately 76 cm (0.76 m) and the average female pace length is 67 cm (0.67 m). Therefore by dividing 10 m by 0.76 m you can establish that the average male needs to take 13 paces to cover 10 metres. The average female needs to take 15 paces (10/0.67).

It is suggested that one person (ideally the tallest) is assigned as the measurer. Measure the length of his or her stride in metres and divide as above. Use the result to establish the 10, 20 and 100 metre distances used to measure the treatment area.

This calculator will assist you in estimating the number of spreader tracks required based on either the stride lengths and swath width you enter or the track length in m and swath width. 

Optimum usage rate

The optimum usage rate for the bait in this example is 10 kg per hectare (100 x 100 m).  Thus, one spreader load (1 kg) should cover 0.1 ha. This equates to four 2.5 x 100 m tracks (or 10 m x 100 m, which is 0.1 ha) as shown below.

If the tracks are shorter, 1 kg of bait will cover more tracks. For example if the tracks are 50 m long 1 kg of bait will be enough for eight 2.5 x 50 metre tracks.

 
One spreader load (1 kg) should cover 0.1 ha. This equates to four 2.5 x 100 m tracks or 10 m x 100 m, which is 0.1 ha (© Allan Burne, Pacific Biosecurity)

By entering your pace length and swath width (or track length if you are measuring rather than using strides) the remaining measurements can be derived using this calculator.

If the spreader is empty before you have covered the calculated area, reduce the aperture size and/or increase the speed at which you are covering ground.

Conversely, if there is still bait left after four 100 m tracks consider increasing the aperture size and/or moving more slowly. In this case you should revisit the treatment area and supplement the bait already spread.

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Broadcasting bait with multiple manual spreaders

When multiple operators are treating the same area, they form a line along the boundary of the treatment area. The operators should be spaced approximately 2.25 m apart. This way the swaths will overlap.

An easy way to check this is for each operator to hold their arms out parallel to the ground while holding a spreader in one hand. There should be about 30 cm between the spreader and the tip of the next operator’s fingers.

By maintaining equal spacing between operators and moving at an even pace it is possible to ensure that the swaths overlap and the entire treatment area is well covered with bait.

 
As the operators move through the treatment area it is important that they remain evenly spaced in a straight line (left) and move at a uniform pace as they pass from one end of the treatment area to the other (right) (© Warren Butcher & Allan Burne, Pacific Biosecurity)

Treatment path

Example of a treatment path taken by four operators treating around an urban structure.  (© Allan Burne, Pacific Biosecurity based on Hawaii Ant Lab drawing)

 

 

 

 

 

 

 

 

 

When the boundary is reached, the innermost operator in the treatment area turns around (180 degrees) and steps 2.25 m further into the treatment area (as shown by the green arrows (left).

The remaining operators regroup around the innermost operator and move back through the next segment of the treatment area. The green arrows show the pattern used for turning the group around.

The operators are spaced approximately 2.25 m apart, and move as a group from one end of the treatment area to the other.

The 2.5 m swaths of bait overlap ensuring that the entire area is covered.

The swath of bait on the return sweep (brown dotted triangles indicate the swath and green boxes indicate the spreaders - left inset) should overlap the swath of the outward sweep

Where obstacles are encountered the operator moves around them taking note of their position.

Areas around obstacles are marked and can later be treated with other baits such as Vanquish Pro paste or ATTRATHOR targeted insecticide.

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All staff MUST be trained and application checked to ensure the correct amount is dispensed in all areas (i.e. 10 kg/ha). Staff should be trained to adjust distribution depending on terrain, movement speed and vegetation densities to maintain a 10 kg/ha application rate.

Always make sure that:

  • Bait is spread evenly
  • The swaths overlap
  • The spaces between buildings are covered
  • No bait is spread within 5 m of any open water
  • No bait is spread within 5 m of a residential building

Mechanical blowers

Petrol driven 2-stroke mist duster (such as the Maruyama MD155DX pictured) may be used to deliver granular bait into areas of dense bush, or where it is suspected invasive ants are nesting high in trees or other locations more than 2.5 metres above the ground.

The mist duster creates a stream of air into which bait is mixed and ejected from a flexible delivery tube. An extension is available for the delivery tube, which allows the bait to be aimed in a specific direction (see below).

The mist dusters have a range of approximately 10 m. The 2-stroke engine is driven by a 50:1 petrol/oil mixture (e.g. 100 ml of oil per 5 L can of petrol). 

A motorised mist duster is used to distribute granular bait into areas of dense bush or into tree tops where invasive ants may be foraging or nesting (© Warren Butcher & Allan Burne, Pacific Biosecurity)
 

The mist duster may also be used for general broadcast bait delivery.

However their weight, combined with the heat generated by the engine make them challenging to use for long periods particularly in environments where temperatures are high.

Their petrol consumption is relatively high and this should be considered when budgeting for a management project.

The mist dusters have a gravity fed hopper, which typically holds up to 6 kg of bait.

For measuring purposes it is recommended that the hopper be filled with 5 kg of bait at a time.

For broadcast baiting one hopper load of 5 kg bait should cover 0.5 ha (equating to an area of 50 x 100 m). The flow of bait is regulated by a hand lever as is the air flow (left). As with manual spreaders it is important to keep track of the amount of bait used per unit area.

Helibaiting

Helicopter delivery of ant baits is an effective method for covering wide areas. However, it is specialised and only practical for large scale uses in areas that have access to appropriate equipment. eXtension.org has information on this method for red imported fire ants, including instructional videos and an aerial application guide.

Information sources

Burne, Barbieri, Gruber. 2015-2019. Management Plan Atafu, Tokelau. Pacific Biosecurity Management Plan

Hawai'i Ant Lab. Little fire ant fact sheet 4: An improved spreader for ant baits: How to modify a cheap fertilizer spreader so it works more effectively. Please note that Hawai'i Ant Lab periodically updates their fact sheets, go to the Hawai'i Ant Lab website to check for updated versions

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