How to test your lawn for grubs and what to do if you find them
- Brown patches in a lawn can have many causes, so grubs should not be assumed without checking.
- A simple test is to dig up a 3- to 4-inch-deep, 12-inch-square section of turf that overlaps healthy grass and damaged grass.
- Grubs are the larvae of beetles such as European chafers and Japanese, Asiatic and Oriental beetles, and they are usually curled into a C shape.
- Fewer than 10 grubs per square foot is considered normal and does not call for treatment.
- If there are 10 or more grubs under the removed turf, treatment may be warranted, and it is most effective when applied in late summer.
- The article says beneficial nematodes are a broader natural option than milky spore powder, while chemical treatments are discouraged because they can harm people, pets, pollinators and wildlife.
Brown patches in a lawn do not automatically mean grubs are present. The article notes that drought, dog urine, fungal disease, pests and too much fertilizer can all cause similar damage, so the first step is to confirm the cause before treating the turf.
To check for grubs, homeowners should dig up a 3- to 4-inch-deep, 12-inch-square section of turf that straddles the border between healthy and damaged grass. If grubs are present, the whitish, brown-headed larvae will be visible in the soil or on the underside of the sod, and they are often curled like a C.
A count of fewer than 10 grubs per square foot is not considered an infestation and does not require action. If the count reaches 10 or more, treatment may be appropriate, especially when the infestation is severe enough that sections of turf roll up easily because the roots have been severed.
The article says grub control works best in late summer, when the insects are young and most vulnerable. It mentions milky spore powder for Japanese beetle grubs, though species identification can be difficult and results are mixed, and it highlights beneficial nematodes, especially the Heterorhabditis bacteriophora strain, as a more broadly effective natural option. Chemical treatments are discouraged because of risks to earthworms, bees, pets, wildlife and humans.
如何检查草坪是否有蛴螬，以及发现后该怎么处理
草坪上的褐色斑块并不一定说明有蛴螬。文章指出，干旱、狗尿、真菌病害、害虫以及过量施肥都可能造成类似问题，因此在处理草坪前，先确认真正原因更为重要。
检查方法很简单：挖起一块深3到4英寸、边长12英寸、跨在健康草和受损草交界处的草皮。如果有蛴螬，它们会出现在土壤里或草皮背面。这些幼虫通常呈白色、褐色头部，身体会弯成C形。
如果每平方英尺少于10只蛴螬，就不算虫害，不需要采取措施。只有当数量达到10只或更多时，才可能需要治理；如果虫害严重，草皮会因为根系被啃断而像地毯一样卷起来。
文章还说，蛴螬防治在夏末效果最好，因为那时它们还比较幼小、较脆弱。文中提到，米尔克孢子粉只针对日本金龟子幼虫，但识别种类并不容易，效果也不稳定；更广谱的自然办法是益虫线虫，尤其是 Heterorhabditis bacteriophora 这一株系。文章同时不建议使用化学药剂，因为它们可能伤害蚯蚓、蜜蜂、宠物、野生动物和人类。