SEASONAL INCIDENCE OF MITE AND INFUENCE OF PESTICIDAL APPLICATION ON ORCHID FLOWER PRODUCTION

摘要

Investigations were carried out in 2010 to determine the influence of abiotic factors on the incidence of the two spotted spider mite; Tetranychus urticae Koch and to determine the influence of pesticides on orchid flower production. Initially, in January, the mite population was very low (1.0 mite/10 cm2 leaf area). The population gradually increased and peaked to 22.98 mites/10 cm2 leaf area in the first fortnight of May along with the rise in temperature and sunshine. Then, the population declinedto a low level of 3.43 mites/10 cm2 leaf area in the first fortnight of December. Maximum and minimum temperatures had a significant positive correlation and sunshine had a non-significant positive correlation, whereas relative humidity and rainfall hada non-significant negative correlation with the mite population. Infestation of the two spotted spider mite was more severe in untreated conditions in comparison to the treated ones. The difference was due to various abiotic factors and natural pest infestation occurrence which drastically affected the flower quality and yield. In unprotected conditions, the number of flower spikes/plant (1.90±0.44 spikes), number of flowers/spike (7.35±1.04 flowers), spike length (42.59±5.69 cm), flower spike diameter (5.26±0.66 mm), and flower size (6.27±0.86 cm) was very low. In protected conditions, flower quality and yield were superior than in unprotected conditions i.e. number of flower spike/plant (2.92±0.57 spikes), number of flowers/spike (11.78±1.16flowers), spike length (57.59±7.35 cm), diameter of flower spikes (9.09±1.01 mm), and flower size (6.73±1.16 cm).