Monitoring the development of the oak lace bug (Corythucha arcuata Say) based on the use of atmospheric heat content

Abstract

In recent years, a negative situation has developed as a result of mass invasions of adventive pests on the lands of the forest fund, among which the oak lace bug Corythucha arcuata Say (Heteroptera: Tingidae) requires special attention. The pest poses a great danger to the survival and productivity of oak forests and forest plantations in the South of Russia. The existing methods of pest monitoring do not always reflect the real constants of the phenology of target objects, which leads to errors in determining the optimal timing of protective measures and a decrease in their effectiveness. Hence, research in the development of precision methods for phytosanitary monitoring of harmful species is an important problem of plant protection, especially biological. The study of the phenology and dynamics of the oak lace bug will allow optimizing protective measures, taking into account the most vulnerable phases of phytophage development and the timing of treatments. The aim of this study was to develop precision methods for monitoring the dynamics of the number and age structure of the oak lace bug population based on the use of the heat content of the atmosphere. The studies were carried out in the central (Krasnodar), northeastern (Tikhoretsk) and western (Krymsk) zones of Krasnodar Krai belonging to the temperate climatic zone, as well as the Black Sea zone (Sochi), located in the subtropical climatic zone. The choice of localities for the research was carried out taking into account the territories of invasive distribution of the oak lace bug and the differences in climatic conditions from moderate continental to subtropical. The calculation of the heat content (enthalpy) of air was carried out using a modified Ramzin nomogram (See Fig. 1). Phenological observations and counting of the number of C. arcuata bugs were carried out on model trees of English oak (Quercus robur L.) (See Fig. 2). The reference date was chosen empirically based on the use of heat content indicators that are different in terms of reference periods and corresponding to these periods (See Table 1). As a result of the studies carried out during 2018-2020, the actual dates of the onset of the phenophases of the oak lace bug and the corresponding enthalpy of air (the heat content) were determined (See Table 2). We calculated the amount of heat required for the emergence of the oak lace bug after winter diapause (140-145 kcal/kg air) and passing through the preimaginal stages of development from egg-laying (158-167 kcal/ kg), hatching of larvae (180-194 kcal/kg) before fledging of adults of a new generation (136-145 kcal/kg). The sum of effective temperatures (SET) was calculated according to the generally accepted method (Chernova, Bylova, 2004; Zamotajlov et al., 2009) (See Table 3). We have shown that the enthalpy of air is the most preferable indicator for assessing thermal characteristics for determining the timing of the appearance of overwintered individuals, the passage of phenophases of insects and the number of their generations in comparison with the sum of effective temperatures (See Table 2 and 3). We found that the number of generations of oak lace bug in the central, western and northeastern zones (temperate climatic zone) of Krasnodar Krai, which is directly dependent on the heat content of the air, was three, and in the Black Sea zone (subtropical climatic zone) there were four generations per seasonal cycle. To improve the reliability of predicting the timing of phenological phases of the oak lace bug, a method for monitoring phenophases of the pest based on calculating the heat content of the air has been developed, which can be used for practical purposes to optimize protective measures associated with the use of insecticides, growth and development regulators of insects, entomopathogens and entomophages in agricultural and forest cenoses. Thus, distribution, development rate, number dynamics and harmfulness of the species to the greatest extent depend on the ecological resource of the inhabited territory, determined by the enthalpy of the air. On the basis of enthalpy, the rate of passage of phenophases and the number of generations of the pest, which determine its invasive development in large areas, are reliably calculated.