Attractive lures

Surveys using lures are undertaken as part of surveillance, delimiting and monitoring of ant abundance and distribution.

Attractive lures are more time consuming and costly than visual surveys, but they can be necessary if ants are at low abundance. This is because visual surveys alone are not able to detect ants if there are few of them. The lures make the ants come to you!

One exception may be Argentine ants, which are not highly attracted to lures and may be more easily detected via repeated visual searching. Work in the California Channel Islands has shown that Argentine ant trail pheromone ((Z)-9-hexedecenal) added to sugar water or protein based bait trap attracts more Argentine ants than plain sugar water.

Using lures for general surveillance : Using lures for delimiting and monitoring : Placing lures in visual survey tracks : Detecting little fire ants

Using lures for general surveillance

Routine use of non-toxic lures around surveillance areas (e.g. transport hubs, ports, airports) provides early warning of new incursions. This type of surveillance is used routinely by MPI in New Zealand as part of the National Invasive Ant Survey.

Over time this regular surveillance can build valuable information about different ant species’ rates of spread.

Ants are drawn to the lures, allowing them to be caught and identified. For a general surveillance campaign both protein and sugar lures are used, so it is important to note which sort of bait the ants were collected on in order to help formulate bait matrix composition for later management activity.

Where the objective is surveillance of a specific species, lures designed to attract just that species are needed. For example, little fire ants are best detected using peanut butter lures. Yellow crazy ants respond well to sweet lures such as honey or sugar water.

Various lures in plastic cups used to test ants preference for different types Left to right: honey, peanut butter, raw chicken egg (© Monica Gruber & Allan Burne)

Materials

For luring you will need:

• sugar and water or honey
• toilet paper or cotton wool for sugar water or honey
• card or paper to place the lures onto (or plastic jars if the ants are to be collected for identification)
• peanut butter or oily fish, sausage or other protein
• lollipop sticks, chopsticks or other sticks for peanut butter (for little fire ants)
• notebook and pen or pencil to record notes

Placing protein (fish or peanut butter) and carbohydrate (liquid honey or 20% sugar water soaked cotton wool or toilet paper) lures in containers such as specimen jars, pottles or vials over the surveillance area gives an indication of presence or absence of ants.

Lures should be spaced approximately 10 m apart in groups of 10-20 extending approximately 500 m away from the centre of the surveillance area.  In high risk areas the number of lures should be increased to at least 8 lures per 10 x 10 m area. Attractive lures should be placed between 8am and 11am or between 3pm and 6pm when ants are likely to be more active. Do not place lures when rain is imminent. If it does rain during the period, the work will need to be repeated. Mark where lures have been placed either on an aerial map/diagram or use GPS waypoints. If you are using a GPS make sure the waypoint number corresponds with the number on the vial or pot. Upload the waypoints into Google maps for future reference. The lures should be retrieved after three hours, labelled (location, bait type, date and time) and taken for identification of any ants captured. The ants should be placed into a preservative (70% ethanol or other alcohol or propylene glycol) to prevent them from rotting. The ants can also be frozen if they do not need to be sent away for identification.

Placement of lures at 10m intervals in groups of 10 -20. The lures should be placed in areas that ants are likely to forage, such as shaded areas, around fruit trees or other potential food resources (© Allan Burne, Pacific Biosecurity)

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Using lures for delimiting and monitoring

Where no ants are observed during a visual survey of a previously infested area, place attractive lures at 20m intervals (© Allan Burne, Pacific Biosecurity)

When a visual survey has been done as part of delimiting or monitoring, and no ants were detected, attractive lures  should be used to confirm their absence. If the target species are present at low abundance, the lures will likely draw them to where they can be seen. The lures (appropriate for the ant species being targeted) are placed on the ground at 20 metre intervals. For delimiting it is best to place both protein (oily fish or peanut butter) and carbohydrate (liquid honey or 20% sugar water soaked cotton wool or toilet paper) lures on card in the survey area. This can also be checked by using food preference tests.

Only a small amount of food is required per lure - about the size of a fingernail should be enough.

If the target ant species clearly recruit to one type of lure better than another it is safe to just use this type of lure. For example, yellow crazy ants often prefer sugar over protein, so only sugar lures need to be used.

Little fire ants are the opposite - they love peanut butter! The Hawai'i Ant Lab has easy instructions on using chopsticks, popsicle sticks, or coffee stirrers with a very thin layer of peanut butter to detect little fire ants. You can paint the sticks a bright colour to make them easier to see. And the Hawai'i Departments of Agriculture (DOA) and Land & Natural Resources (DLNR) has produced a great video on how to check for little fire ants.

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Placement of lures in visual survey tracks

Have a look at the information on visual surveys to check how the tracks are set up, and why five surveyors are referred to here.

Sugar lures (yellow circles) are placed at 20 m intervals first by surveyors 1, 3 and 5 in the first track (a), then by surveyors 2 and 4 in the second track (b) (© Allan Burne, Pacific Biosecurity / Google Earth)

Going back to the first survey track, lures should be placed by surveyors 1, 3 and 5 on their respective lines (below left). In the next adjacent survey track the lures should be placed by surveyors 2 and 4 (below right).

In the next track the lures are placed by surveyors 1, 3 and 5 again.

By repeating this pattern you will create a matrix of lures spaced at 20 m intervals. Any ants present will be drawn to the lures, allowing them to be caught and identified.

For most ants attractive lures should be placed between 8am and 11am or between 3pm and 6pm when ants are likely to be active.

Do not place lures when rain is likely. If it does rain during the period, the work will need to be repeated.

Mark where lures have been placed either on an aerial map/diagram or use GPS waypoints. If using a GPS, make sure the waypoint number corresponds with the number marked on the map. Upload the waypoints into Google maps for future reference.

The lures should be checked after thirty minutes, and if no ants detected, checked again after three hours. Any target species found should be recorded.

Detecting little fire ants

Domingo Cravalho of US Fish and Wildlife shows how to survey for little fire ants (© Hawai'i Departments of Agriculture (DOA) and Land & Natural Resources (DLNR))

Information sources

Craddock, Mattson. 2014. National invasive ant surveillance programme report 2014. Report by the New Zealand Ministry of Primary Industries

Peacock, Mattson, Craddock Pettigrew. 2015. National invasive ant surveillance programme annual report 2015. Report by the New Zealand Ministry of Primary Industries

Ward, Stanley. 2012. Site occupancy and detection probability of Argentine ant populations. Journal of Applied Entomology. 137: 197–203 

Hawai'i Ant Lab. Little fire ant fact sheet 3: checking your property for little fire ants. 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

Doherty. 2013. Delimiting surveys for invasive ants. Pacific Invasives Initiative, Auckland

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

Merrill, Boser, Naughton, Choe, Rankin. 2016. Detecting Argentine ants (Linepithema humile) on California’s Channel Islands. XXV International Congress of Entomology (ICE 2016). Orlando, Florida, 25-30 September

content reviewed by Phil Lester, Victoria University of Wellington, August 2016