Control of White Grub Infestations in Lawns
An understanding of the cycle of the White Grub is important before beginning your control measures. Without a plan or control program the numbers of white grubs in lawns will increase as will their damage to lawns, turf grass, golf courses and other grasses in areas such as pastures or graze lands. The basic biology and cycle of this lawn pest as it matures will help you time your pesticide application. Without proper timing, the application of pesticides will either work poorly or result in failure to control the lawn grub problem. This information page will cover different topics about White Grubs such as their basic biology, damage, control.
There are many pests of lawns in the United States. These pests are separated into lawn pest groups that give you an indication of where they develop and which parts of plants on which they feed. Once you understand this important relationship you will be able to plan a control strategy that includes proper use of the correct product and when the product or insecticide should be used for optimal control of the targeted pest. Proper timing is just as important as choosing the preferred pest control product for the targeted pest. This timing is especially true when dealing with White Grubs and Molecrickets.
Leaf, stem and thatch inhabitants are a group of lawn pests that include Chinch Bugs, Spittle Bugs and others. Soil inhabitants include white grubs, molecrickets and billbugs. This information page will concentrate on control of white grubs in your lawn.
The C-shaped larval stage of certain beetles cause a great deal of damage
to lawns or turfgrasses in residential lawns, golf courses and pasture
grasses. The grubs are the immature offspring of Japanese
Beetles, June Beetles (May Beetles), Chafers. These immature stages of
beetles that feed on the root systems of your lawn are called White Grubs.
Adult beetles either fly to the area (driven by
mating behavior) or emerge from the ground as they develop into their final
adult stage. After emerging as adults, the process of mating and laying
eggs begins. The adult beetles emerge, mate and lay eggs from June until
As the young grubs emerge from their eggs they burrow into the top layer
of soil where they begin feeding on small soil particles and organic
matter. It is in this stage that white grubs are easiest to control.
A small, young grub that feeds close to the surface and which has not developed
a resistance to chemicals is far easier to control with pesticides than older
and hardier grubs.
As temperatures begin to rise in the spring of the year, so do the white grubs that have over-wintered in their deep cells. When they rise back to the surface, these grubs again feed on the roots of turf grasses. This feeding continues until late spring. The pupation period usually lasts about two weeks, after which the adult beetle emerges from its pupal state. The adults emerge to begin the next round of mating, feeding and laying of eggs.
Damage to the roots of your lawn or turf grass can be devastating as these grubs have had practically no food during the winter months and their appetite is in full swing. There are pests that feed on the leaves and stems of grasses and their damage is easy to see. The damage caused by White Grubs often goes unnoticed or is not identified correctly. You are most likely to see the results of their feeding before seeing the damage to the hidden root system. Once grubs begin feeding on the roots, the grass blades above ground will begin to die and the ground above will feel soft or spongy. Damage is often noticed as brown patches in the lawn. A tinge of yellow color can be seen in lawns that are heavily infested with white grubs.
The cycles of grubs can vary somewhat depending on the species of beetle
that is laying eggs in your lawn. June Beetles usually have a three year
life cycle and Japanese Beetles and certain
Chafers have a one year life cycle.
The grub's life cycle takes it to various levels in the soil during different seasons of the year as the grub responds to moisture, ground temperatures. The beetles mentioned lay eggs in the soil. As the larvae or grubs emerge from the eggs that are a few inches deep in the soil, they primarily feed on organic debris in the upper soil layers. This feeding is in summer to early fall of the year. As cooler temperatures approach, the white grubs begin to move deeper down to protect themselves from the cold. As the soil begins to warm up the next spring, the grubs return to the upper levels of soil in your lawn to begin feeding on the root systems of plants.
The best time to kill white grubs is when they are closest to the soil's surface and when the grubs are young. In their smallest stages (after emerging from eggs) the pest has far less resistance to insecticides applied to the lawn.
Pesticides applied to lawns in July and early August will have the best
control. Do not confuse lawn applications with ornamental
applications. Spraying ornamentals will kill adult insects but the
products used for this type of job usually do not have any noticeable effect on
grubs. Pesticide sprays can be used to kill adult beetles that are
depositing eggs in your lawn. This spraying does greatly reduce numbers of
adults but is not necessarily a good substitute for proper lawn and soil
Lawn Applications to Control White Grubs
Conventional insecticides rarely give good control of these lawn pests. Grubs are soil inhabitants that live and feed in areas where pesticides have trouble reaching. For this reason it is best to use Merit insecticides for white grubs. Merit Granular has two characteristics that help achieve control of such pests: super long residual and systemic action. Merit Insecticides are available in granular formulation as well as wettable powder concentrate formulation: Merit .5G Insecticide Granules and Merit 75% Concentrate.
Season long control is a great advantage when fighting this lawn pest but the product can possibly break down under severe conditions such as water and extreme temperatures. In most cases the summer/fall application of Merit systemic insecticide will do the trick. If you live in an area where infestations are stubborn or difficult to control or if extremes in rainfall or temperatures might affect the insecticide, an extra application in late spring could be quite beneficial.
Merit contains an active ingredient that can give season
long control of white grubs with a single application. You should apply
Merit insecticides no sooner than mid July and no later than early August.
Check with your local extension office to see if this time table is different in