Life cycle of Retracrus johnstoni Keifer (Acari: Phytoptidae)

• Published in: Neotropical entomology 2003-06, Vol.32 (2), p.197-201
• Main Authors: Gondim Jr., Manoel G.C.(Universidade Federal Rural de Pernambuco Depto. Agronomia), Moraes, Gilberto J. de(USP ESALQ Depto. Entomologia, Fitopatologia e Zoologia Agrícola)
• Format: Article
• Language: English
• Subjects: Arecaceae; Biologia; Biology; ENTOMOLOGY; Eriophyoidea
• ISSN: 1519-566X; 1678-8052; 1678-8052
• DOI: 10.1590/S1519-566X2003000200002

Eriophyoid mites are commonly associated to palm trees, although few of them have been reported causing economic damage to those plants. One exception is Retracrus johnstoni Keifer, a pest of Bactris gasipaes Kunth, plant used for palm heart production. R. jonhstoni is frequently found in large numbers on Arecaceae in southeast Brazil. The biology of this mite was studied under laboratory condition. Sections of leaves of the palm tree Syagrus romanzoffiana (Cham.) Glassman, with ca. 15 leaflets, were kept alive by maintaining their bases in distilled water. Ca. 20 field collected adults of R. johnstoni were transferred onto each leaflet for oviposition. After 24h, mites were removed, leaving only one egg laid. Once a day, the eggs and the subsequent stages were examined to determine the life cycle, oviposition rate and survivorship. Each immature stage of R. johnstoni lasted ca. seven days, corresponding to ca. 20.5 days for immature development. The sex ratio was ca. two females per male. Total fecundity was slightly over five eggs per female. Immature and adult mites secreted a layer of white material, which covered their bodies. Spermatophores of R. johnstoni resemble those of other species in the same superfamily, and consist of a head of ca. 6 x 6 µm onto a base ca. 6 µm long. Leaflets show dark spots on the lower surface and yellowish spots on the corresponding regions of the upper surface. Leaf spots become progressively larger and coalescent, and the leaf dies and falls prematurely. Os ácaros Eriophyoidea estão comumente associados a palmeiras, entretanto poucas espécies têm sido relatadas causando danos econômicos nessas plantas. Uma exceção é Retracrus johnstoni Keifer, praga de Bactris gasipaes Kunth, planta utilizada na produção de palmito. R. johnstoni tem sido encontrado em grande número de arecáceas no Sudeste do Brasil. O objetivo deste trabalho foi estudar a biologia deste ácaro em laboratório. Seções de folhas da palmeira Syagrus romanzoffiana (Cham.) Glassman com cerca de 15 folíolos foram conservadas mantendo suas bases em água destilada. Aproximadamente 20 adultos de R. johnstoni foram transferidos para cada folíolo para oviposição. Após 24h, os ácaros foram removidos, deixando-se apenas um ovo por folíolo. Diariamente os ovos e os estágios subseqüentes foram examinados para determinação do ciclo de vida, taxa de oviposição e sobrevivência. Cada estágio imaturo de R. johnstoni teve duração de aproximadamente sete dias, totalizando apro