Puskás J1, Hill L2, Kiss M1 and Nowinszky L1*
Received: June 19, 2023; Published: June 27, 2023
*Corresponding author: Nowinszky L, Eötvös Loránd University, Savaria University Centre, Hungary
The relationship between the activity of moths, as indicated by pheromone traps, to solar activity and Earth magnetism was investigated in North Carolina, USA. Relationships were found but species differed in their responses. These results are similar to those found in light- and pheromone trapping data on moth and caddisfly species in Hungary and Australia.
Keywords: Pheromone; Trapping; Moths; Solar Activity; Geomagnetism
Pheromone traps are used around the world in the fight against harmful insects. The catch indicates the presence of pest species, the start of its swarming, the population size and the swarming process in a place of interest. For plant protection prognosis, it is usually sufficient to count the captured insects at 2- or 3-day intervals. The lighttrap is another collecting device that is used for various scientific purposes and its uses predates the use of pheromone traps. Early in their use, researchers recognized that the effectiveness of light-traps is affected by several environmental effects. Many scientific publications on this topic have appeared in many countries of the world. We have investigated environmental factors for decades such as in our recent book (Nowinszky, Puskás, Hill ), which includes references to earlier work by us and others. Most pertinently to the current study, we had the opportunity to study environmental effects on pheromone trap collection data in Hungary. Plant protection entomologist, Gábor Barczikay counted and trapped the pheromone trapping results of 8 harmful moth species daily between 1982 and 2013 in a Hungarian orchard. Using this rare daily data set, we published a number of studies together with him including in a book (Nowinszky, Puskás ). In the current report, we investigated the influence of solar activity and Earth magnetism, as among the most important environmental factors, using the data of moth species collected in the state of North Carolina, USA.
The activity of the Sun is the common name for a group of local disturbances of the Sun’s radiation. Solar electromagnetic and corpuscular radiation affects the geophysical parameters on Earth, which in turn affects the biosphere. The solar activity includes all the information about the Sun’s surface that can be detected by using several methods. The most important activity is the 10.7 cm solar radio flux. The solar radio flux at 10.7 cm (2800 MHz) is an excellent indicator of solar activity. It correlates well with the sunspots, flares and a number of ultraviolet (UV) and visible solar irradiance records. The F10.7 has been measured consistently in Canada since 1947, first at Ottawa, Ontario and then at the Penticton Radio Observatory in British Colum bia. Unlike many solar indices, it can easily be measured reliably on a day-to-day basis from the Earth’s surface, in all types of weather. The data we use was published by British Geological Survey (http://www. geomag.bgs.ac.uk/data_service/space_weather/solar.html).
A derivative of solar activity is the Dst (Disturbance Storm Time) index, which has been measured since 1957/58. It characterizes the earthly manifestations of space weather by measuring the strength of the ring current around the Earth, which is created by protons and electrons originating from the Sun. The so-called geomagnetic storms are large disturbances of the Earth’s magnetic field that can be defined by changes in the Dst index. This index describes the globally averaged change of the horizontal component of the Earth’s magnetic field at the magnetic equator. It is calculated hourly by using measurements from a few stations at low latitudes (Honolulu, San Juan, Hermanus, and Kakioka). The size of a geomagnetic storm is classified as moderate (−50 nT > minimum of Dst > −100 nT), intense (−100 nT > minimum Dst > −250 nT) or super-storm (minimum of Dst < −250 nT). In quiet times the Dst ranges between +20 and −20 nanoTesla (nT). We used the data of hourly equatorial Dst values (Final) published by WDC Kyoto Observatory. Moth (Lepidoptera) species have been trapped in pheromone traps in the state of the North Carolina (USA) for many years at several localities: Lenoire, Sampson County and Johnston County. This catch data was available on the internet for the years 1996, 1998, 1999, 2000 and 2002.The catching data used for the calculations are summarized in Table 1.
Basic data were the number of individuals of each of five species caught in one night. In order to compare the differing sampling data, relative values were calculated. The relative catch value (RC) was the quotient of the number of specimens caught during one night per the average nightly catch of individuals within the relevant sampling period. The RC was one when the actual nightly catch was equal to the average nightly catch across the whole trapping period (Nowinszky ). All catch data by species were considered as a single sample and the relative catch values were counted from these. However, some of the data represented trapping over 2-3 nights recorded as a single date. In these cases, the 10.7 cm solar radio flux and Dst data were added to these dates and processed. The Dst data were also available hourly, and since moths are most active in the first half of the night, local time data of 21 hours was taken into account. The relative catch values were added separately for each species to the 10.7 cm solar radio flux and Dst values of each night. After that, groups were formed from the data pairs with the number of groups or classes calculated according to Sturges’ method (Odor, Iglói ). We averaged within groups the 10.7 cm solar radio flux, Dst index and relative catch and plotted them.
Our results are shown in Figures 1-10. The catch of four of the five investigated species increased in parallel with the increase in the value of the 10.7 cm solar radio flux. The exception was the Tobacco Budworm Moth (Chloridea virescens Fabricius, 1777), whose catch increased initially and then decreased. Examples of different responses by different species in our previous studies include: Most caddisfly (Trichoptera) species increase activity with increasing 10.7 cm solar radio flux: Neureclipsis bimaculata Linnaeus, 1758, Hydropsyche contubernalis McLahlan, 1865, Hydropsyche bulgaromanorum Malicky, 1877, Brachycentrus subnubilus Curtis, 1834, Halesus digitatus Schrank, 1781 (Kiss et al., 2021). Likewise, an Australian moth species: Tree Lucerne Moth (Uresiphita ornithopteralis Guenée, 1854) (Nowinszky, et al. ). Increasing then decreasing: Ecnomus tenellus, Rambur, 1842 (Trichoptera) (Kiss, et al. ). In regard to Dst index, two types of relationship were found: Decreasing and increasing then decreasing catch values as Dst values increased.
The two species showing decreasing activity were the Southwest Corn Borer (Diathraea grandisella Dyar, 1911) and Corn Earworm (Heliothis zea Boddie, 1850). The increasing and then decreasing type of response occurred in the other three species: European Corn-borer (Ostrinia nubilalis Hübner, 1796), Tobacco Budworm (Chloridea virescens Fabricius, 1777) and Western Bean Cutworm (Striacosta albicosta Smith, 1888).We could not obtain significant results from such a small number of catch data. This problem always arises when we are not able to perform our calculations with very large data sets. A solution to this is offered by the hypothesis that we previously proposed (Nowinszky, et al. ). We propose that results that meet two conditions can be considered real. One is that results from multiple independent samples are essentially the same. The other condition is that the results can be interpreted based on our prior knowledge. The results of our previous studies based on other species in other continents are extremely like our current results. One of our studies (Nowinszky, et al. ), examined the effectiveness of light trapping of 8 caddisfly (Trichoptera) species in relation to geomagnetic Dst index values. The catch results of two caddisfly species increased and then decreased: Hydropsyche bulgaromanorum Malicky, 1977 and Setodes puctatum Fabricius, 1793.
In another study (Nowinszky, et al. ) we processed data from a Mészáros-type light-trap operated in Bečej (Serbia) also in connection with the Dst values. This high-performance light-trap collects many moths. Among them, we found the decreasing type of response in the Green Oak Tortrix (Tortrix viridana Linnaeus, 1758) while the European Corn-borer (Ostrinia nubilalis Hübner, 1796), Lesser Belle (Colobochyla salicalis Denis & Schiffermüller, 1775) and the Ruby Tiger (Phragmatobia fuliginosa Linnaeus, 1758) displayed the increasing and then decreasing type of response to increasing Dst index. In a recent study (Nowinszky, et al. ) we found similar behavior of moths collected in pheromone traps in Hungary. In analyzing data for seven species, we found that two species belonged to the increasing then decreasing type: Hawthorn Red Midget Moth (Phyllonorycter corylifoliella Hübner, 1796) Oriental Fruit Moth (Grapholita molesta Busck, 1916). In all cases, independence is clear and the types of behavior can also be interpreted from a professional point of view. The explanation for the decreasing type can be that negative values of Dst are favorable and positive values are unfavorable for insects. In the case of the increasing and then decreasing type, increasing Dst values initially favor the increase in flight activity, but above a certain value, they inhibit it. Although pheromone traps are primarily used for prognosis of pest activity, we consider it worthwhile to study the collected data in connection with the impacts of environmental factors on insect activity.