Abstract In recent years the litchi spider mite, Oligonychus litchii Lo et Ho (Acariformes: Tetranychidae) has become an important pest in Taiwan on fruit crops such as wax apple, litchi, longan, guava and loquat. We carried out field surveys in a wax apple orchard in Pingtung County from February 2008 to February 2009 to study the spatial distribution and population dynamics of O. litchii. The indices of dispersion (ID), Green’s indices (Cx), the mean crowding of Lloyd, the patchiness index of Lloyd, the b value of Taylor’s power law (log S2= log a + b logm), and the β value of Iwao’s patchiness regression (m* = α + βm) all indicated a clumped dispersion of O. litchii on wax apple. Analysis of the stage structure of the population in the field showed that the proportions of eggs, larvae, nymphs, male and female adults were 83, 3, 8, 1 and 5%, respectively. The distribution patterns of O. litchii within the various regions and height of a plant were all similar. It was noted that O. litchii preferred to aggregate on mature leaves. The population occurred year round, reaching its peak in April and May, and then declined in June due to prolonged rainfalls and the start of the typhoon season. Climatic factors tend to affect the population density of O. litchii.
摘要 荔枝葉蟎 (Oligonychus litchii) 屬於真蟎目 (Acariformes) 、葉蟎科(Tetranychidae)，為近年來台灣農作物上重要害蟎之一。本研究自2008 年5 月9 日至6 月27 日止於屏東縣麟洛鄉的蓮霧園內進行荔枝葉蟎之田間分布類型研究，分別以Index of dispersion (ID)、Green’s coefficient of dispersion (Cx)、Lloyd’s mean crowding index (m*) 、Lloyd’s patchiness index (m*/m) 、Iwao’s patchiness regression 及Taylor’s power law 等統計分析結果均呈聚集型分布，而荔枝葉蟎之田間年齡結構中以卵佔83% 為最高，其次依序為若蟎、雌成蟎、幼蟎及雄成蟎，分別為8、5、3 及1%，顯示其年齡結構上以卵為最大量。調查荔枝葉蟎在蓮霧植株之株內分布情形，其中於植株垂直高度、周緣深度間差異並不顯著；對葉片成熟度之偏好，荔枝葉蟎於成熟葉上平均個體數明顯多於未成熟葉，且喜好聚集於成熟葉之葉面中肋上取食及產卵。自2008 年2 月至2009 年2 月於屏東縣麟洛鄉蓮霧園進行田間周年族群動態調查，結果顯示4 月為其發生高峰期，6 月以後因連續降雨及颱風影響致使葉蟎族群密度開始下降，顯示氣候因子為其田間密度之重要影響因子。
| Key words: Oligonychus litchii, spatial distribution, population dynamics | | 關鍵詞: 荔枝葉蟎、空間分布、族群動態 |
|