Light traps are tools for managing nocturnal pests. One of the problems with their application in tropical regions is the evaporation of water from their tanks. This raises the cost of using them. Can another substance, instead of water, be used in insect tanks that can later evaporate? Of course, the substitute should not reduce pest insect catching. Also, catched insects should not be allowed to leave after being trapped.
Hi Amir,
We are using propylene glycol for our pitfall traps and we have not this problem. It is an oily liquid that avoid that specimens scape when they fall in the trap, it takes much longer to evaporate than water, and it preserves the DNA, so the specimens can be used for genetics studies. The problem is that, evidently, it is more expensive than water, but you can dilute with water, and the evaporation is still less than those of water, and you can lower costs.
what about using a sticky material on the bottom of the bucket? that way the insect will glue on the sticky substance and can be collected any time. this will be a good method for pest management, however, if you are interested in identifying the insects later, you will loss some morphological features and you may have broken body parts (legs, wing, antennae etc).
As previously mentioned, propylene glycol has very good results in SLAM and pitfall traps, but cost might be an issue. A cheaper alternative, is common, of the shelf, radiator coolant. From my experience, it works well for pitfalls, even in the Portuguese summer. For collection or ID, the coolant dyes could be an issue, but if just for catching pests, that should be no problem.
Also, it can be filtered and reused for quite a while.
Hi Amir Cheraghi
After this aforementioned information, it would be good to try each option (ethanol, propylene glycol, radiator coolant, water + propylene glycol... etc) and choose the best one based on your objectives and the cost benefit. With this you can also make combinations.
ethanol will evaporate more quickly.
At least some radiator coolant is toxic. Animals like drinking it, but die. One purpose of the dye is to mark radiator fluid as toxic, otherwise it looks like water.
Sticky traps will require frequent replacement because the trap will become full and the trapped insects will attract ants and animals. Handling the sticky material can be unpleasant and makes everything sticky.
Water has the advantage that it is non-toxic and cleaning up is easy. You could try adding something like calcium chloride. This salt is deliquescent and will prevent the trap from drying out completely if the humidity is high. I am not sure what concentration would be ideal. Another option would be to place a tank of water above the trap and have the water slowly drip into the trap to replace water lost by evaporation.
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