Insect pests and their role as biocontrol agents on populations of Impatiens glandulifera in Bulgaria – a case study

Based on data from available scientific publications, a review of the insects, trophically related to Impatiens glandulifera in its European invasion zone has been made. As a result, nine insect species (Pristerognatha fuligana, Deilephila elpenor, Xanthorhoe biriviata, Chrysolina herbacea, Siobla sturmi, Impatientinum asiaticum, Aphis fabae, Aphis nasturtii, Phytoliriomyza melampyga) were found on the invasive plant. Of the identified insects, seven species (D. elpenor, X. biriviata, A. fabae, A. nasturtii, C. herbacea, P. fuligana, P. melampyga) are widespread in the country, of which only two – C. herbacea and  P. fuligana are associated with I. glandulifera. The remaining two (I. asiaticum and S. sturmi) are not pre-sented in the Bulgarian entomofauna. Тhe potential role of these insects as agents of biological control of populations of I. glandulifera in Bulgaria has been assessed.

Динамика численности и видовой состав тлей на посадках семенного картофеля в Ленинградской области

Существенным элементом в комплексе специальных и агротехнических приемов, направленных на ограничение распространения вирусной инфекции, является мониторинг численности, динамики и видового состава тлей, мигрирующих в посадках оригинального картофеля. Двухлетний мониторинг (2016 – 2017 гг.) на опытных полях Гатчинского района Ленинградской области проведен с использованием желтых водных ловушек Мёрике. Изучены количество тлей, сроки их миграции на посадки картофеля, сроки наступления пика численности. Наибольшее влияние на насекомых оказывала среднесуточная температура воздуха. За сезон наблюдений отловлено: в 2016 г. — 481 крылатая особь 31 вида, в 2017 г. — 131 особь 30 видов. Доля возможных переносчиков вирусов картофеля от общего числа зарегистрированных крылатых тлей составила в 2016 г. 14,8 %, в 2017 г. — 32,8 %. Оценка скрытой зараженности вирусной инфекцией (MBK, YBK вирусы) методом ИФА в 2015 – 2017 гг. показала, что на растениях картофеля сорта Ломоносовский скрытая зараженность составила 2,6 – 7,3 %, сорта Чародей — 1,9 – 13,3 %, сорта Невский — 0,8 – 10,5 %, сорта Романо — 4,1 – 9 %. Из известных переносчиков вирусов картофеля в оба года в энтомологических сборах с сосудов отмечены Aphis nasturtii — 6 – 12,2 %, Aphis fabae — 7,2 – 4,6 % от общего числа отловленных; Myzus persicae (13 %) в составе мигрирующей генерации тлей отмечены только в дождливом и прохладном 2017 г. В прогностических целях желательно пользоваться в регионе также данными со всасывающей ловушки, поскольку появление в ней насекомых отмечено на 10 – 12 дней раньше, чем на полях.

Мониторинг динамики численности и видового состава тлей-переносчиков Y-вируса в условиях опытного поля Ленинградского НИИСХ «Белогорка»

Наблюдения за динамикой численности летающей генерации тлей показали, что миграция их на картофель начиналась в 1-й (2014 г.) и 2-й (2015 г.) декадах июня. Интенсивный лет в оба года отмечали в 3-й декаде июня. Пик численности приходился на первую декаду июля, когда количество крылатых тлей на один ловчий сосуд Мерике составляло в 2014 г. 80 экз., в 2015 г. — 70 экз. В составе мигрирующей генерации тлей на картофеле встречались крылатые мигранты 21 вида, среди которых доля эффективных и важных векторов передачи Y-вируса (YBK) составляла в 2014 г. 36,3 %, в 2015 г. — 34,7 % от общего числа зарегистрированных. Основными векторами передачи Y-вируса являлись: Acyrthosiphum pisum Harr., Aphis fabae Scop., Macrosiphum euphorbiae Thomas, Myzus persicae Sulz, Rhopalosiphum insertum, Aphis nasturtii Kalt, Rhopolasiphum padi. Исходя из проведенных наблюдений за динамикой лета тлей скорректированы сроки проведения обработок инсектицидами оригинального картофеля. С учетом динамики численности лета крылатых тлей изменены и сроки сжигания ботвы на более ранние. Сжигание ботвы Реглон Супер (2 л/га) выполнено 25.07.2014 г. и 27.07.2015 г. на раннем сорте Ломоносовский и 30.07.2014 г. и 02.08.2015 г. на среднераннем сорте Чародей. Ранние профилактические обработки инсектицидами и ранние сроки сжигания ботвы позволили снизить скрытую зараженность в питомниках отбора клонов у сорта Чародей по MBK с 15,8 до 4,4 %, по YBK — с 3,0 до 0 %, у сорта Ломоносовский по MBK — с 13,6 до 3,6 %, по YBK — с 2,0 до 0 %.

Estimating population variability of aphids (Hemiptera: Aphididae): how many years are required?

Variability is an important characteristic of population dynamics, but the length of the time series required to estimate population variability is poorly understood. To this end, population variability of Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii (Kaltenbach) (Hemiptera: Aphididae) was investigated. Population variability (measured as PV, a proportion between 0 and 1) was estimated for time series of 3–62 years, giving replicate estimates for time series of 3–20 years that were normally distributed. Mean values for PV were more uniform for a time series of 12 years or longer than for shorter ones. The standard deviation of PV declined to a minimum at 12–15 years, as the length of the time series increased. Discrimination of estimates of PV was reliable for 15-year time series and longer, but not necessarily for shorter ones. Although M. euphorbiae had a relatively low PV, the coefficient of variation of that PV (12.5), was higher than for the other two species (3.5, 4.5). For robust estimates of PV, a time series of 15 years is recommended, because it minimises the standard deviation of PV, and discriminates values of PV that differ by 0.06 on a 0–1 scale.

Flying features of winged aphids on potato seed plants during 2004-2006

The most important problem of the introduction of advanced potatoes seed system is to protect against repeated infection the healthy potatoes by viruses in the open field. In our republic the greatest risk to re-infection the healthy potatoes seed is Y - potato virus. The principal vectors of Y – potato virus, developing the largest number, are three types of aphids - buckthorn (Aphis nasturtii), alder (Aphis frangulae) and bean (Aphis fabae). The bean aphid is dominant, in some years its size rises up to 2406 copies. Relatively low coefficient of harmfulness (0.1 equivalent unit), provided the mass settlement on the plants can significantly increase the contamination of potatoes seed. The climatic conditions of the growing season, precipitation, relative humidity, which significantly affect the development and dispersal of aphids on host plants are of great importance.

Seasonal dynamics of three coexisting aphid species: implications for estimating population variability

Seasonal patterns of abundance and population variability were determined for Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii (Kaltenbach) (Hemiptera: Aphididae) in potato plots from weekly samples for 28 years. All species showed a single annual peak, but arrived and reached peak abundance at different times. Population variability (PV, a proportion between 0 and 1) for the week of peak abundance was close to that of other sample weeks and mean seasonal abundance. Based on mid-season abundance, PV of 0.76 for M. persicae differed significantly from 0.80 for A. nasturtii, as well as from 0.59 for M. euphorbiae. A weekly time scale for abundance, initiated at an early stage of plant growth, produced slightly different estimates of PV early and late in the season than a scale centred on peak abundance for each species. PV at the time of invasion differed from estimates for the rest of the summer. The annual abundance used to estimate PV was best determined in the context of aphid life history. Nevertheless, PV provided a robust and precise metric for comparing population variability among the three species, regardless of their seasonal patterns of abundance.

Population variability and persistence of three aphid pests of potatoes over 60 years

Abundance, persistence, and variability of populations of Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii Kaltenbach (Hemiptera: Aphididae) in potato plots for intervals of 58 years (n = 1), 29 years (n = 2), 19–20 years (n = 3), and 9–10 years (n = 6) were compared. The abundance of M. euphorbiae showed no trend among decades and varied 2.4-fold, whereas that of M. persicae and A. nasturtii declined and showed 54-fold and 3700-fold variation, respectively. All three aphid species persisted through the first five decades and M. euphorbiae also persisted through the sixth (last) decade, but M. persicae and A. nasturtii failed to persist for 1 and 3 years of the last decade, respectively. Population variability (a proportion between 0 and 1) measured over a 58-year interval was high: 0.585 for M. euphorbiae, 0.771 for M. persicae, and 0.830 for A. nasturtii. During the first three but not the last three decades, population variability increased with sampling interval, owing to dramatic declines in abundance for M. persicae and A. nasturtii and one stable decade for M. euphorbiae, but no evidence of a more-time — more-variation effect was detected. Persistence was not related to population variability, but declined with abundance. Populations did not reach equilibrium, because of declining abundance for M. persicae and A. nasturtii and changes in population variability from decade to decade for M. euphorbiae. Populations of M. persicae and A. nasturtii from this crop monoculture were less stable than previously studied natural populations of a native aphid species. In contrast, the population of M. euphorbiae, a native species, had variability in a potato crop similar to that of the previously studied native species. The high population variability of M. persicae and A. nasturtii may be associated with their status as introduced species. The dynamic and species-specific characteristics of population variability require that interspecific comparisons be considered cautiously.