Turf Tips by Chris Karcher

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August Turf Tips
Upcoming Grub Activity - What to Look For

Introduction
White grubs may annually damage our lawns.  These grubs have a life cycle that consists of an egg, larva, pupa and adult.  This process is called a complete metamorphosis.  While there are many types of white grubs, the adult beetles of typical white grubs we encounter include:

• Japanese Beetle

• European Chafer

• Green June Beetle

• Masked Chafer

• May/June Beetle

Damage
Grubs can be responsible for a significant amount of damage to turf every year.  Grubs are soil-inhabiting pests that damage turfgrasses by feeding on the grass roots just below the soil surface.  Typical signs of grub damage include "drought like" patches of wilted, dead, or dying turf visible during spring (April and May) and fall (September to November).

Another sign of their presence may be mole, skunk, or bird activity searching for them in the soil.  In fact, the tunnels made by moles, the plowing and turning-over of soil by skunks, and pecking and scratching by birds often will cause more physical damage to the turf than the grub infestation itself.  In extensively damaged areas, the sod, with its roots cut off, can be easily pulled back by hand, exposing the grubs typically located near the top 3 inches of the soil.

Upcoming Grub Activity
Early to mid-August will be the time most likely for heavy grub activity.  At this time the grubs will begin feeding on the grass roots.  While damaging symptoms may not appear right away, discolored patches of turf will appear in late August, September, and even into October.

Grub Weather
As a rough guideline to determine the magnitude of grub problems in your area, consider what the weather conditions were like during the last weeks in June and the first few weeks in July.  The critical factor is moisture levels.  Egg survival is dependent on having enough moisture.  When the young larvae hatch, they too are dependent on moisture for survival.  If the weather was wet or moist during this period, you can expect a potential grub problem in late summer and fall.  Hot dry weather during the late June and early July time period will usually desiccate many of the eggs causing a lower grub population that year.

IPM & Grub Activity
Implementing an Integrated Pest Management (IPM) approach to grub control requires a good understanding of how and when these pest populations develop.  By knowing the pest, its life cycle, and the environmental conditions that favor grub activity, you will be in a better position to make sound, environmental decisions as to whether or not control measures are necessary.  Due to the fact that grubs are below the turf surface it is harder to detect grub activity until after the fact and brown patches of turf have already appeared in the lawns.  By then it is too late.  Therefore, one sustainable approach to managing pests is careful monitoring or scouting of grub activity.  "Getting your knees dirty" and gathering information on grub populations is a fundamental component of IPM for two reasons.  First, because an understanding of the lawn's ecosystem is essential to preventing pest problems.  Second, because IPM relies upon close monitoring of pest populations in order to determine when a population has reached a damaging threshold.

Treatment
To determine if treatment is warranted, define your objectives for the lawn.  Knowing that no control product will give 100% elimination, do you need to treat?  If you find a large population of grubs, (5 or more in the area of dinner plate size of your turf) a control treatment of either Merit or Mach II would be needed.  Remember that if the thatch levels in your lawn is above ¾" you will have difficulty getting the product down below the thatch levels where it is needed (core aeration in the fall will help this problem).  Follow label instructions for watering and application of any control product that you apply.

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Chris Karcher is a local franchise owner of NaturaLawn of America - the leader in organic-based lawn care and the only national service provider to promote Environmentally Responsible lawn care.  "Doing the right thing has never been this easy!"

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