Lawn grubs are the larvae of different species of beetles such as Japanese beetles. These grubs live under the lawn and chew on the roots. In small quantities, they are not very harmful. But in large quantities, these grubs can kill the lawn. Therefore, several kinds of insecticides have been developed that are designed to kill off these white grubs. However, lawn owners should pull up the turf grass in order to ensure that the problem is lawn grubs and that there is a significant infestation warranting pest control.
Before white grubs can be killed, they must be identified. Areas that have white grub infestations are often browning and wilting. Turf grass can tolerate some white grubs, but having 10 or more grubs per square foot is an indication that the white grubs have overloaded the lawn and might kill the turf grass. Several kinds of insecticides can be used to kill off white grubs and many of these insecticides have positive benefits and consequences.
Some insecticides, such as imidacloprid, kill white grubs by harming the nervous system. Others, such as chlorphyrifos, must be swallowed by the white grub in order to kill it, according to Dow AgroSciences. The milky spore bacteria causes milky spore disease on the white grubs, killing them and making the soil inhospitable for white grubs.
Some insecticides can be harmful to people or the environment. Bendiocarbs are a good grub insecticide because small quantities of this insecticide have been found to effectively kill white grubs. This is beneficial since large quantities of insecticides in the soil can have a detrimental effect on the environment over the long run, according to Naturwissenschaften Journal. Imidacloprid can have harmful effects on humans by causing difficulty breathing, staggering, trembling and spasms. This insecticide also kills a lot of other wildlife including birds, according to the Flora website. Birds are some of the best natural predators for white grubs, so killing off birds can actually be counter-productive. Chlorphyrifos has a moderate level of toxicity.
Many insecticides need the right conditions in order to function effectively. In order for bendiocarbs to kill the white grub, the grub must be no older than 7 days old. Isofenphos is not as effective if lime is added to the soil in order to reduce the soil acidity, since alkaline soils can cause insecticides to break down, according to the University of Massachusetts. Also, a great deal of watering needs to occur after applying isofenphos in order to get it to work properly. Finally, there are some species of white grub that might not be harmed by isofenphos.
Milky spore is an organic form of insecticide that can be used to kill white grubs. This bacteria functions very slowly and is not recommended for white grubs that are highly concentrated under the turf grass, since the bacteria will not kill the white grubs fast enough, according to the University of Rhode Island. However, if allowed to integrate into the soil, the milky spore disease will kill the white grubs over a long period of time. Parasitic nematodes are another option. According to the University of Illinois, parasitic nematodes--very small worms--have effectively reduced the number of lawn grubs. The heterorhabditis bacteriophora nematode should be used, since other kinds of nematodes tend to float to the top of the soil away from the white grubs.