Newbery D McC
Imperial College, Silwood Park, SL5 7PY, Ascot, Berks, UK.
Oecologia. 1980 Jan;46(2):180-185. doi: 10.1007/BF00540124.
(i) In an area of coastal scrub on Aldabra Atoll the growth and phenology of 120 bushes of Scaevola taccada was measured along three transects stretching 200 m inland from the sea, between May 1977 and November 1978. Correlations between bush parameters, the infestation by the coccid Icerya seychellarum and prevailing saline conditions were measured. Considerable death (up to 50% of labelled clusters) of S. taccada occurred in 1977-78. Leaf infestation ranged from 0 to 1.6 mg dry weight of coccids cm total leaf area per cluster. (ii) Coccids fed predominantly on senescing leaves and seasonal differences in leaf infestation were closely associated with changes in leaf phenology. Under experimental conditions coccids could utilize green leaves. (iii) Infestation increased with distance away from the sea whilst the influence of salt, and its effect in increasing leaf succulence, decreased inland. Infestation was strongly negatively correlated with leaf succulence. (iv) Two experiments with S. taccada showed that coccids significantly reduced the growth of leaves and roots and increased the rate of leaf senescence. 0.5 mg cm of coccids reduced leaf production by 39%. (v) In May 1977 the proportion of dead clusters was significantly positively correlated with coccid infestation and in 1978, when mean cluster death doubled, death near the coast (0-100 m) was positively correlated with leaf succulence, whilst inland (101-200 m) death significantly increased with increasing infestation. (vi) It was concluded that coccids could account for the reductions in leaf production in the field and that they contributed to much of the bush death. (vii) The effects of coccids on the leaf production of S. taccada and Euphorbia pyrifolia (Part I) closely agreed. It was estimated that 1.25 mg cm of coccids can completely check leaf production.
（i）1977年5月至1978年11月期间，在阿尔达布拉环礁的一片沿海灌丛区域，沿着从海边向内陆延伸200米的三条样带，对120株草海桐的生长和物候进行了测量。测量了草海桐植株参数、塞舌尔绵蚧的侵染情况与当时的盐分条件之间的相关性。1977 - 1978年期间，草海桐出现了相当数量的死亡（高达50%的标记丛）。叶片侵染程度为每丛每平方厘米总叶面积上有0至1.6毫克干重的蚧虫。（ii）蚧虫主要取食衰老叶片，叶片侵染的季节差异与叶片物候变化密切相关。在实验条件下，蚧虫能够取食绿色叶片。（iii）侵染程度随着远离大海而增加，而盐分的影响及其增加叶片肉质化的作用在内陆则减弱。侵染程度与叶片肉质化呈强烈负相关。（iv）对草海桐进行的两项实验表明，蚧虫显著降低了叶片和根系的生长，并加快了叶片衰老速度。每平方厘米0.5毫克的蚧虫使叶片产量降低了39%。（v）1977年5月，死亡丛的比例与蚧虫侵染呈显著正相关，1978年，平均丛死亡率翻倍，海岸附近（0 - 100米）的死亡与叶片肉质化呈正相关，而在内陆（101 - 200米），死亡随着侵染程度增加而显著上升。（vi）得出的结论是，蚧虫能够解释田间叶片产量的降低，并且它们导致了大量草海桐植株死亡。（vii）蚧虫对草海桐和白背叶大戟叶片产量的影响（第一部分）非常一致。据估计，每平方厘米1.25毫克的蚧虫能够完全抑制叶片产量。
