Zoltan Imrei1, Ivan Sivcev2, Ivan Tomasek2, Miklos Toth1
1 Plant Protection Institute, Hungarian Academy of Sciences
2 Institute for Plant Protection & Environment, Beograd, POB 936, YU-11001, Yugoslavia
Sticky traps are not suitable for quantitative monitoring because the sampling efficiency of the trap is constantly changing over time depending on the number of insects already captured and other debris accumulating on the sticky surface. For quantitative monitoring it is necessary to develop a non - saturable trap design, which can continually take representative samples of the population.
Our lab is in the course of developing an upturned funnel trap for Diabrotica, which fulfills the above requirements. This year the performance of this funnel trap was compared with that of the sticky "cloak" (PAL) trap which is widely used for detection of Diabrotica in Europe. The comparisons were performed by using two types of baits, a sex pheromone bait (which is capable of attracting only the males) and a flower volatile bait (which attracts both females and males).
In tests with low population density the funnel trap was found to be as effective as the PAL sticky trap with all bait variations. In a high density situation the funnel trap captured significantly less during the first part of the test, then, suddenly captures in the funnel trap increased dramatically and significantly exceeded those in the sticky traps. We theorize that the probable cause for this controversy might be that water from heavy rain (registered before the last day of the test) could have got into the upturned funnel, and the water so accumulating inside the funnel could inhibit beetles escaping from inside the trap, thus increasing the trap's efficiency. Other observations also suggested that a certain percentage of beetles already in the dry funnel trap can escape back through the entrance hole. For the future new experiments are planned to study this effect, so the development of the new non-saturable trap design is still not complete and has to be continued.
When comparing the performance of traps baited with single baits with that of traps containing both baits, we found that traps with the dual bait were not catching significantly more than traps with single baits. This result corresponds to preliminary results obtained one year ago. So at present it seerns that putting both baits into a single trap does not have significant advantages over using single-baitedtraps for their respective purposes. Traps baited with the pheromone are best used for detection purposes, while traps baited with the flower volatile bait can be used if the capture of females is needed.
The ratio of females in the catch of the flower volatile baited traps was higher, than in that of unbaited traps (corresponding to the natural sex ratio), suggesting that the flower volatile bait is more strongly attractive towards females then towards males.