Miklós TÓTH¹, Zoltán IMREI¹, Ivan SIVCEV², Ivan TOMASEK^2
1 Plant Protection Institute, Hungarian Academy of Sciences, Hungary
² Institute for Plant Protection & Environment, Beograd, POB 936, YU-11001, Yugoslavia

It is common knowledge that sticky traps - although very sensitive for detection - 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, high capacity trap design, which can continually take representative samples of the population at the same efficiency level.
Based on our previous results several modifications of funnel trap designs have been tested and compared for efficiency with the sticky PAL trap designs. Almost all of the designs tested proved to be as sensitive as the sticky traps, and one of the funnel designs even gave consistently higher catches. This design seems to be suitable for both sensitive detection (in low population areas) and also for quantitative monitoring at sites with higher populations and seems to be a very versatile tool suitable for all kinds of trapping studies. In order to make this trap available for other research groups working on Diabrotica, our laboratory in 2001 is ready to start production of the prototype series, provided that additional funds will become available.
Considerable interest has been shown at previous meetings concerning the trapping range of pheromone-baited PAL traps. Since the debate so far was more oral than experimental, we were tempted to present here the results of a previous preliminary study we conducted some years ago. The test was performed at a site without maize in the vicinity of the Zemun Expt. Stn., Yugoslavia. Male WCR beetles collected from a distant maize field were released in the middle of the test area from one point, and traps were set up at distances of 10, 30 and 100 m from the point of release. At each distance 4 traps were set up to the north, east, south, and west from the point of release. A total of 300, 200 and 300 males were released on July 26, 29 and 31, resp. Traps were inspected and captured beetles were recorded before the next release took place on July 29, 31 and August 2.
In this test we recorded no significant difference in captures in traps set up at 10, 30 or 100 m from the point of release (see Table ). The recapture rates ranged from 2.09 to 2.97% with no significant difference between the three distances. Although to exactly determine the range of attraction of pheromone-baited traps more detailed release-recapture studies will be necessary, data obtained in our preliminary study already suggest that the range of attraction (as defined by Wall and Perry, 1987) of a pheromone baited trap is below 10 m for WCR, since there was no sign of interference (significant decrease in catches) even at the most closely spaced traps as compared to more distantly spaced ones.
The similar level of catches and recapture percentages in the traps spaced from 10 to 100 m in this study suggests that WCR males had a high potential for migration away from the point of release, capable of covering  several hundred m or even more within a couple of days. Probably only beetles coming into the closer vicinity (<10 m) of the traps were attracted and captured by the traps. These data are supplemented by direct visual observations on the behavior of beetles around a pheromone source.

Table: Catches of released male D. v. virgifera in traps baited with the pheromone at 10, 30 and 100  m distances from the point of release. (Zemun, Yugoslavia, July 26 - August 2, 1996). Statistics: ANOVA followed by DNMRT on (x+0.5)1/2 transformed data. Means with same letter within one column are not significantly different at P=5%.
 

Reference: WALL, C., and PERRY, J.N., 1987. Range of attraction of moth sex-attractant sources. Entomol. exp. appl. 44:5-14.