在行间种植易感染橡胶病害的复盖植物,看起来应该是有害的,因为随着寄主植物种植面积的扩大,病菌就有了更多的蔓延机会。但是很久以来就已知道,栽培易于感染橡胶根病的豆科复盖植物却会减低胶树的根病发病率。在战前的一项更新试验中(H.2),到定植后第三年末所得的结果如下:复盖种类匍匐豆科复盖灌丛豆科复盖无复盖每亩胶树的根病发病率 Planting covered plants that are susceptible to rubbery diseases appears to be detrimental because there are more opportunities for germs to spread as host plantings expand. It has long been known, however, that the cultivation of leguminous plants that are susceptible to Rhizomania reduces the incidence of gum root disease. In a pre-war renewal trial (H.2), the results obtained at the end of the third year after planting were as follows: Covered species Creeping legumes Covering shrubs Leguminosae Covering No cover Roots per acre gum tree Incidence