Seasonal trend of Eutetranychus orientalis in Moroccan citrus orchards and its potential control by Neoseiulus californicus and Stethorus punctillum

Citrus brown mite, Eutetranychus orientalis (Klein), known as major pest of citrus crops in different countries, was considered as a quarantine pest in Morocco. This pest is currently among the most potential enemies of Moroccan arboriculturists following the increasing ineffectiveness of the majority of acaricides used in conventional orchards. The present study was designed to collect and morphologically identify specimens from 31 orchards in the five main production regions of Morocco; to study the population dynamics of this pest in Taroudant as well as the molecular identification of a Phytoseiid considered as a potential predator using the mitochondrial 12S rRNA gene. Morphological description confirmed that the collected adult females from all orchards in the five regions belong to E. orientalis. Thus, this exotic pest has invaded all citrus growing regions since its introduction. In the Souss region, two significant peaks of population outbreaks of this pest were observed. A first peak from November until the end of December 2017 and in winter, a second peak is recorded in early autumn 2018. Thereafter, mite infestations remained at lower levels throughout the summer. In addition, it appears that eggs represented between 50 to 88.7% of population in spring and winter seasons respectively, but percentage of adult females does not exceed 2.3% in autumn and winter seasons. Adult females of Neoseiulus californicus, larvae of Stethorus punctillum, were more abundant and very active on orange leaves and weeds during period of observation. Molecular analysis using 12S ribosomal RNA gene confirmed that the best query coverage 99.23% (E-value = 5e-176) with 99% of recovery identical to N. californicus. The phylogenetic tree obtained from comparison of the specimens’ generated DNA sequences with other individuals from Neoseiulus genus revealed the relationship with species N. californicus. These results suggest that orchard management will favour the plant cover associated with citrus trees and thus ensure sustainability, diversity and high density of phytoseiides and other predatory insects. This auxiliary fauna, like N. californicus, S. punctillum, will be able to control spider mites, as well as other phytophagous insects and keep them below damaging levels in citrus orchards in the Souss region.

Statistik Demografi Kumbang Predator Stethorus sp. (Coleoptera: Coccinellidae) pada Tetranychus Kanzawai Kishida (Acari: Tetranychidae)

Tetranychus kanzawai Kishida adalah spesies tungau yang dapat menyebabkan kehilangan hasil pada tanaman pertanian sekitar 60–90%. Salah satu cara untuk mengendalikan tungau hama yang ramah lingkungan adalah dengan menggunakan kumbang predator Stethorus punctillum Weise. Penelitian ini bertujuan untuk menentukan statistik demografi, preferensi, dan tanggap fungsional S. punctillum pada T. kanzawai. Pengujian neraca hayati S. punctillum menggunakan 100 telur, dengan mengamati jumlah individu yang masih hidup sampai betina dewasa menghasilkan keturunan. Preferensi S. punctillum terhadap 50 telur dan 50 individu masing-masing nimfa dan imago T. kanzawai, dengan mengamati jumlah T. kanzawai yang dimangsa oleh larva instar I, II, III, IV dan imago S. punctillum. Tanggap fungsional dilakukan dengan memberi mangsa S. punctillum sebanyak 30, 40, 50, 60, 70, 80 telur T. kanzawai, pengamatan dilakukan pada jumlah telur yang tersisa. Hasil penelitian menunjukkan bahwa telur S. punctillum berlangsung selama 7,01 ± 0,72 hari, larva instar I 4,84 ± 0,51 hari, instar II 3,16 ± 0,52 hari, instar III 3,00 ± 0,27 hari, dan instar IV 2,48 ± 0,50 hari. Kemampuan betina menghasilkan telur sebanyak 64,47 ± 2,37 butir. Laju reproduksi kotor (GRR) S. punctillum 64,29 individu/generasi, tingkat reproduksi bersih (Ro) 17,18 individu/betina/generasi, laju pertambahan intrinsik (r) 0,27 individu/betina/hari, rata-rata masa generasi (T) adalah 62,41 hari, dan waktu ganda (DT) adalah 2,51 hari. Data menunjukkan bahwa S. punctillum memiliki preferensi stadia telur T. kanzawai dan kurva tanggap fungsional tipe III dengan Th 7,68 menit dan a 0,22 telur/menit.

The sensitivity of some species of entomoacarifages to the insectocaricides used in the protection of apple culture

The apple orchard populations of acariphagous (Stethorus punctillum Weise, Chrysopa carnea Steph, and mite-predators Amblyseius andersoni Chan, Metaseilus occidentalis Nesbit and Neoseiulus californicus Mc Gregor), which were at least 25 years under pesticide treatment, were studied. Our studies show that for these populations the least toxic pesticide is Avaunt, EC, Talstar 10 EC, Omite 30 WP, Confidor 200 SL and the most toxic pesticide is Vertimec 018 EC, Dursban 480 EC for both entomophagous. BI-58 New is slightly toxic for the larvae of C. carnea and highly toxic for N. californicus in laboratory culture. The orchard populations of acariphagous develop resistance to BI-58 New, Dursban 480 EC and Decis f-Luxx 025 EC, in the conditions of the prolong pesticide treatment. The discovery of natural populations of entomophagous resistant to pesticides is of high importance due to its potential practical use.