Variability of infestation of rose varieties by the spider mite Tetranychus urticae under conditions of application of Phytoseiulus persimilis or acaricides

The two-spotted spider mite Tetranychus urticae is a dangerous polyphagous pest of agricultural and ornamental plants. In a commercial greenhouse treated with acaricides or biological control using predatory mite Phytoseiulus persimilis individual varieties of roses differed significantly in terms of the average annual infestation by the pest mite. On the poorly populated rose varieties, the biological control agent application was more effective as compared to the acaricides. To effectively control the pest, the required predatory mite rates were 4.6–8.7 times higher on varieties with a minimal spider mite infestation (Aqua and Deep Water) as compared to the maximal pest infestation (Heaven and Brazil).

THE INFLUENCE OF DIFFERENT PHYTOPROTECTION SYSTEMS ON ENTOMOFAGE FAUNA IN APPLE PLANTATION

The paper presents data on the diversity of entomophagous fauna in an ecologically managed apple plantation, as well as aspects regarding the differences found in the structure of the entomophagous complex in three variants of phytoprotection technologies: "Ecological", "Biotechnical" and "Chemical standard". The study was carried out during the years 2019-2020, at the Research Institute for Fruit Growing Pitesti, in a plot aged 12 years. The evaluations were performed both in the field, visually and in the laboratory, at binocular magnifier. As a result of this study, a number of 6 species of predatory insects were identified: Chrysopa carnea, Coccinella septempunctata, Adalia decempunctata, Anthocoris sp., Phytoseiulus persimilis and Aphidoletes aphidimyza, were mainly from the Orders Mesostigmata, Coleoptera, Neuroptera, Diptera and Hemiptera.

Artificial heat waves induce species-specific plastic responses on reproduction of two spider mite predators

Climate change models predict that the frequency, intensity and duration of heat waves will increase in the next decades. Heat waves can have profound impact on the reproduction of biocontrol agents ranging from postponing oviposition to manipulating offspring quantity via egg number and quality via egg size. Such species-specific responses of biocontrol agents to heat stress may also affect their success in controlling the target pest. Here, we evaluated the predation and reproductive performance of the two spider mite predators Phytoseiulus persimilis and Neoseiulus womersleyi exposed to simulated mild, moderate and extreme heat wave conditions over three days. Irrespective of heat wave conditions, all N. womersleyi females survived, whereas 12% of the P. persimilis females died. Both species responded to heat stress via plastic modifications resulting in increased predation rates and smaller egg sizes. Significantly more P. persimilis females postponed oviposition during the experimental phase than N. womersleyi. The deposited egg number of Phytoseiulus persimilis was not affected by heat wave conditions. On the contrary, the reproductive output of N. womersleyi was a function of temperature, i.e., the higher the temperature, the higher the number of deposited eggs. These findings indicate that P. persimilis is more heat sensitive in relation to reproduction than N. womersleyi. However, further investigations of heat wave effects on other fitness-related traits and their consequences at population level are needed to find out whether N. womersleyi is an alternative or supplement to P. persimilis as spider mite control agent under heat waves.

Mites from the family Phytoseiidae as an element of an anti-resistant strategy for protecting fruit plantations from spider mites

In the last decade, the acarocomplex of apple orchards in the plain-steppe zone of the Crimea was dominated by two species of mites, fam. Tetranychidae - Amphitetranychus viennensis (Zacher) and Panonychus ulmi (Koch). Their share in the complex of phytophagous mites was 52.5 and 32.0%, respectively. Against the background of repeated acaricidal treatments during the season, the emergence of resistant races of phytophagous mites was recorded. The proposed anti-resistant strategy for controlling the number of spider mites on an apple tree involves the use of Phytoseiulus persimilis (Athias-Henriot), Neoseiulus californicus (McGregor), and Amblyseius andersoni (Chant). The combination of methods of seasonal colonization by phytoseiids serves as the building blocks of an anti-resistant defense system.Resettlement in the spring, by flooding, of two species of acariphages, P. persimilis and A. andersoni , contributes to the formation of acarofauna, so that while the first species reduces the number of phytophagous mites (by 50-60%), the second adapts and starts feeding later, and, at the expense of daughter individuals, it allows to reduce the number of pests by the end of the second decade of June to 2-3 individuals / leaf. In summer, a double release of the predatory mite N. californicus with a norm of 30 thousand individuals / ha (150-300 individuals / every 10 trees) reduces the risk of mass reproduction of spider mites at high average daily temperatures and low humidity.

Efficacy of the predatory mite Cydnoseius negevi (Swirskii & Amitai) (Acari: phytoseiidae) as a shared predator for sucking pests on sweet pepper in a net house in Egypt

A field experiment was carried out to evaluate the efficacy of the native predatory mite Cydnoseius negevi (Swirski and Amitai) (=Typlodromus negevi) as a biological control agent for Bemisia tabaci (Gennadius) complex, Onion thrips Thrips tapaci (Lindeman) and Tetranychus urticae (Koch). The efficacy of Phytoseiulus persimilis (Athias-Henriot) against these pests was also evaluated. The data obtained revealed reduction in population density of the above-mentioned pests in the experimental plots for P. persimilis and C. negivi compared to the control plot. Mean population density of each of the pests ranging from 32.2–0.5, 284.4–2.0 and 441.8–2.0 individuals / leaf for T. urticae, in the three plots respectively. The mean values of B. tabaci fluctuated between 41.1–2.1, 16.2–1.0 and 57.3–3.6. individuals / leaf and T. tabaci between 20.1–2.6, 13.7–1.4 and 24.9–1.9 individuals / leaf respectively. A slight non-consumptive negative effect is shown by P. persimilis against the pests B. tabaci and T. tabaci. This preliminary experiment hopefully will enhance the role of the native predator C. negevi to play a role in bio-control and its mass augmentation.

The assessment of resistance of the acarocomplex formed on apple tree against the background of pesticide treatments

Клещи-фитофаги ежегодно наносят существенный вред промышленным плодовым культурам, наиболее повреждаемой из них является яблоня. Многократное применение химических препаратов в защите от вредителей не только оказывает пестицидный прессинг на агроценоз, но и нарушает экосистему плодовых насаждений, что проявляется в смене одних видов другими, влияет на биоразнообразие, снижает численность полезных членистоногих и приводит к появлению резистентных к пестицидам рас клещей. Целью исследований являлась разработка и испытание системы защиты интенсивных яблоневых садов Красногвардейского и Нижнегорского районов Республики Крым от клещей сем. Tetranychidae - боярышникового Amphitetranychus viennensis (Zacher), красного плодового Panonychus ulmi (Koch) с помощью хищных клещей-фитосейид Phytoseiulus persimilis (Athias-Henriot), Neoseiulus californicus (McGregor) и Amblyseius andersoni (Chant). Производственные испытания системы проводились в 2019-2020 гг. на участках, где в 2015-2018 гг. был сформирован акарокомплекс методами наводнения и сезонной колонизации. После формирования акарокомплекса была проведена оценка его устойчивости к токсическому действию применяемых в хозяйствах средств защиты растений. Исследованиями установлено, что сформированный в течение трех лет акарокомплекс хищных клещей позволил снизить численность диапаузирующих самок A. viennensis на 87 % и плотность популяции вредителей в летний период, предотвратить вспышку численности фитофагов в весенний период 2019-2020 гг. Доказано, что препарат из класса пиретроидов с действующим веществом тау-флювалинат снижает численность хищников на 99 %. Частичное восстановление плотности популяции за счет миграции аборигенных видов хищников наблюдалось через 2-3 месяца. Вспышка численности клещей-фитофагов на участках, где был сформирован акарокомплекс хищных клещей, происходит из-за применения токсичных для них препаратов и появления резистентных к акарицидам рас клещей-фитофагов. Phytophagous mites annually cause significant damage to commercial fruit crops, the most damaged of which is the apple tree. Repeated use of chemical preparations in protection against pests does not only exert pesticide pressure on agrocenosis, but also affects the ecosystem of fruit plantings, replacing one species with others, influencing biodiversity, reducing the number of helpful arthropods and causing the emergence of pesticide-resistant mite races. The aim of the research was to develop and test the system of protecting intensive apple orchards of Krasnogvardeisky and Nizhnegorsky districts of the Republic of Crimea from mites of Tetranychidae family - hawthorn mite Amphitetranychus viennensis (Zacher), European red mite Panonychus ulmi (Koch) with the help of predatory phytoseiidae mites Phytoseiulus persimilis (Athias-Henriot), Neoseiulus californicus (McGregor) and Amblyseius andersoni (Chant). In-process system tests were carried out in 2019-2020 on plots where in 2015-2018 the acarocomplex was formed using methods of population development and seasonal colonization. After the acarocomplex formation, an assessment of its resistance to toxic effect of plant protecting agents used in farms was carried out. The studies confirmed that the acarocomplex of predatory mites developed in three years allowed to reduce the number of diapausing females of A. viennensis by 87% and the pest population density in the summer period, to prevent outbreak of phytophagous population in the spring period of 2019-2020. It was proven that pyrethroid class preparation with the active ingredient tau-fluvalinat reduced the number of predators by 99%. Partial recovery of the population density due to the migration of native species of predators was observed in 2-3 months. Outbreak of the number of phytophagous mites on the plots where the acarocomplex of predatory mites was developed was due to the use of toxic preparations and the appearance of resistant to acaricides phytophagous mite races.

Relative potency of a novel acaricidal compound from Xenorhabdus, a bacterial genus mutualistically associated with entomopathogenic nematodes

Our study aimed to identify the novel acaricidal compound in Xenorhabdus szentirmaii and X. nematophila using the easyPACId approach (easy Promoter Activated Compound Identification). We determined the (1) effects of cell-free supernatant (CFS) obtained from mutant strains against T. urticae females, (2) CFS of the acaricidal bioactive strain of X. nematophila (pCEP_kan_XNC1_1711) against different biological stages of T. urticae, and females of predatory mites, Phytoseiulus persimilis and Neoseiulus californicus, (3) effects of the extracted acaricidal compound on different biological stages of T. urticae, and (4) cytotoxicity of the active substance. The results showed that xenocoumacin produced by X. nematophila was the bioactive acaricidal compound, whereas the acaricidal compound in X. szentirmaii was not determined. The CFS of X. nematophila (pCEP_kan_XNC1_1711) caused 100, 100, 97.3, and 98.1% mortality on larvae, protonymph, deutonymph and adult female of T. urticae at 7 dpa in petri dish experiments; and significantly reduced T. urticae population in pot experiments. However, the same CFS caused less than 36% mortality on the predatory mites at 7dpa. The mortality rates of extracted acaricidal compound (xenocoumacin) on the larva, protonymph, deutonymph and adult female of T. urticae were 100, 100, 97, 96% at 7 dpa. Cytotoxicity assay showed that IC50 value of xenocoumacin extract was 17.71 μg/ml after 48 h. The data of this study showed that xenocoumacin could potentially be used as bio-acaricide in the control of T. urticae; however, its efficacy in field experiments and its phytotoxicity need to be assessed in future.