The presentation of the data is different from last year: there was rather less trapping in the peak summer season of 2021, so instead of gross totals of species and moths, I have converted these to average numbers of species and moths per night. I have also broken the data into a number of different seasons. The dates were carefully selected: the second period starts when I changed the actinic light in 2021 (see below); the third period starts when (at last) in 2021 the cold spring ended and the number of species caught in a night rose above 20; the third period ended on my return from France (in both years), which coincides with the reversion of the actinic light to its original type; and the fourth period finishes with the end of meteorological autumn.
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| Comparison of results in my Newton Longville garden 2020/2021 |
As I observed in my first post reviewing 2021, numbers were down in the spring of 2021 (second period in the table): the cold weather led to fewer moths of fewer species. However, the actinic light seems to have been slightly less affected than the LED.
For the first, fourth and fifth periods, the performance of both types of lights in 2021 was similar to what it had been in 2020. However, there is something striking in the summer period (with the paler background in the table). The LED figures are not markedly different between 2020 and 2021: it's the actinic figures (orange text) that are very much better in 2021 than they were in 2020. On average, in the summer of 2021 the actinic light caught each night 28% more moths of 65% more species than in 2020, and out-performed the LED light by a smallish margin.
I mentioned that period 2 began when I changed the actinic light and period 3 ended when I reverted to the previous version. In mid-March, the actinic strip light was broken in high winds. Acting on advice received the previous summer from mothing friends in France, I replaced it with the Synergetic variety. A Synergetic light is essentially the same as a normal blue-white actinic - in fact it is identical in physical dimensions and electrically - but the phosphor coating of the tube includes an additional green element. There is evidence (references to papers on request) that at least some moth species have eyes that are sensitive to green wavelengths as well as to UV and blue (and sometimes red). As far as I know, Synergetic lights only come as straight tubes and not as compact bulbs: this is because their principal use is in insect-zappers in restaurants and similar locations.
The Synergetic seems to have been very much better in the third (summer) period of 2021 compared to the actinic in 2020, but this effect isn't clear in the second (spring) period when the weather was the predominant effect.
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| Comparison of results in France |
The French data should be treated with caution as I only ran the traps on very few occasions, so there may be a notable effect of random variation. Nevertheless, I think I can confidently say that Synergetic lights are very substantially more effective at attracting moths than the normal types of actinics. I will be using a Synergetic for 2022.
I haven't yet run an analysis to see if the advantages of the Synergetic compared to the actinic are concentrated on specific moth families: if I find anything significant there, I will write another post on this blog.
Hi Tim,
ReplyDeleteThe marked improvement shown by the Synergetic bulb could, of course, simply reflect the fact that you'd employed a fresh bulb of whatever type (actinics do lose their attraction to moths over time although it isn't usually obvious to our eyes). However, I do actually agree with you that the green Synergetic tubes seem slightly better anyway, perhaps because they have a broader wavelength with peaks at both 368nm and 540nm. I've used one in a Heath trap but not often enough to get any useful data. In this country it only seems possible to get hold of 15w Synergetic tubes. If you happen to know where to source 30w examples (if anyone actually manufacturers them) I'd be very interested!
Hi Dave,
ReplyDeleteI know that the manufacturers usually recommend changing actinic tubes after 8,000 hours due to fading. In my case, the actinic which broke in March was actually less than a year old, having been run for less than 1,000 hours, so I don't think it had faded significantly.
I can find Synergetic tubes in the standard 15W 18-inch form, and in slightly more powerful 18W 24-inch and 22W circular forms as well as the less-powerful 11W. However, I haven't seen any 30W tubes: Googling this tends to turn up the 30W fly traps that are equipped with two 15W tubes.