They treat their seeds with a fungicide to combat seedling diseases.是什么意思？

They treat their seeds with a fungicide to combat seedling diseases.

他们用杀真菌剂浸了种子来防止秧苗受病.

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

treat

n. 款待，招待，乐事，乐趣；v. 对待，治疗，处理，款待；

例句
New ways to treat arthritis may provide an alternative to painkillers.
关节炎的新疗法可能是止痛药之外的另一种选择。

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

seeds

n. 种子( seed的名词复数 )，子孙，起源，（尤指网球比赛）种子选手；

例句
...autumn's bounty of fruits, seeds and berries.
秋天丰富的水果、种子和浆果

with

prep. 和，跟，随着，关于，和…一致；

例句
A waiter entered with a tray...
侍者端着托盘进来了。

fungicide

n. 杀真菌剂；

例句
They treat their seeds with a fungicide to combat seedling diseases.
他们用杀真菌剂浸了种子来防止秧苗受病.

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

combat

n. 格斗，搏斗，战斗，〈美〉竞赛，比赛，论战；vt. 与…战斗，与…斗争，防止，减轻；

例句
The seagulls swirled in aerial combat over the barges.
海鸥盘旋在驳船上方，展开空中的搏斗。

seedling

n. 秧苗，幼苗，树苗，实生苗；

例句
Keep the soil moist. That way, the seedling will flourish...
保持土壤湿润，那样幼苗就能茁壮成长。

diseases

n. 疾病( disease的名词复数 )，弊端，恶疾，痼疾；

例句
The biology of these diseases is terribly complicated.
这些疾病的机理极其复杂。