Certainly in most organic lawns, grubs are not the problem that the synthetic lawn care industry has made them out to be.  To be on the safe side, check the sunnier, drier areas of the property.  Use a square mouth shovel to make two slices in the turf at right angles to one another.  Peel the turf back and check in the root zone for grubs.  Make sure you really look.  I would not be surprised to find them to be very small even though it is approaching the middle of September. 

If you find more than 6 grubs per square foot it makes sense to treat them.  The best natural treatment I have found is the use of parasitic nematodes, Heterorhabditis bacteriophora.

Check out greenmethods.com for more info on biological controls.  Make sure you follow the directions for applying Hb nematodes and I’m certain that you will find them very effective in treating your grub problem.

What to do about it now?  The best thing is get ready to improve the soil conditions come fall (only a couple of weeks away).  Top-dress and heavily over-seed these areas come early September.  If your soil test results warrant it make certain that you lime.  Also fall is the best time to aerate your lawn.  All these activities will encourage a healthier stand of turf for next season.  Remember to mow high throughout the season! 

Many folks attempt to control a crabgrass outbreak by lowering their mowing height.  This is perhaps the worst thing they could do.  Crabgrass plants are very adaptive to mowing height. Plants can produce seeds at mowing heights as low as 1/2-inch.  Crabgrass reproduces by seeds. It has a prolific tillering or branching habit. A single plant is capable of producing 150 to 700 tillers and 150,000 seeds.

Establishing a dense and healthy stand of turfgrass is the best way to control crabgrass and other annual weeds, including grasses and broad-leaf weeds. The proper mowing height and frequency, fertilization and irrigation are part of the weed control program and should be practiced throughout the growing season.

The truth is July is not a good time to aerate. Generally the grass has or is attempting to go dormant. If you aerate now, you will put the grass under more stress than it is already experiencing. You will bring weed seeds to the surface or spread annual weeds like crabgrass over greater areas. Since you are also bringing soil cores to the surface you are providing better weed seed to soil contact, allowing greater light and warm soil to ensure germination.

A much better time is to wait until mid- to-late August. The cool season grasses are beginning to come out of dormancy, the warm season grassy weeds like crabgrass begin to die off with the cooler evening temperatures. Over-seeding at this time is especially beneficial. We found that if we broadcast grass seed after we aerated we would further thicken the grass.

Good soil structure is critical to plant health.  Good soil structure allows air and water to move through the soil’s pore space and provide channels for the roots to grow through. Ideally soil pore space would be 25% each for air and water. As soils become waterlogged the 25% of air space is taken up by water.  Another way to look at it the soil bulk density increases in wet weather limiting root growth.  If there is traffic on the field additional compaction will occur.

According to studies published in the Journal of Experimental Botany report that when plants encounter compacted soil, stomatal closure occurs and shoot growth slows.   Ethylene is believed to play a central signaling role during the response of plants to waterlogging.  In simpler terms the plant begins to shutdown, its ability to carry on photosynthesis slows, shoot growth and root growth slow.  The turf grass will exhibit chlorosis or yellowing under such conditions.

Unfortunately it is difficult to correct poor drainage issues once a field has been constructed.  The fields that we have been on this season that were problematic were constructed without crowning (center of the field one to two feet higher than the sidelines) to allow water to flow off the fields.  During construction heavy earthmovers were used leading to further compaction of the underlying soil.  Over this compacted soil; sod was rolled out.  It is very difficult to correct these situations once they have been put in place.

So what to do about it? 

Weather - First, we can hope for drier weather.

Limit Traffic - It is important to limit traffic, especially wheeled traffic which will only increase the level of compaction.  This means mowers too.

Aerate - Core aeration will help once the fields have adequately dried, though it is important to core aerate only if the grass can actively grow. 

Top-Dress - Top-dressing with high quality compost can also help.  It is important not to top-dress these native soil fields with sand.  While for many it seems counterintuitive, the small amount of sand that you add will only increase the likelihood of further compaction. 

Irrigation – While it should go without saying the irrigation system should be turned off; we still need to say it.

Earthworms – It may be a stretch, but earthworms can be introduced for very little money.  While conditions may not be ideal for the earthworm, if they take you are introducing natural aerators to the soil.

Be Patient – The grass is not going to grow until it is ready.  The introduction of a synthetic fertilizer with high water soluble nitrogen will only make matters worse.

Red thread is a sign of low-nitrogen availability for the lawn.  Soils with a pH below 6.5 – 7.0 will also be more likely to exhibit the condition.  If you haven’t already done so, it would be a good thing to apply another organic fertilizer application to reduce infestation.

Red thread is a sign of low-nitrogen availability for the lawn.  Soils with a pH below 6.5 – 7.0 will also be more likely to exhibit the condition.  If you haven’t already done so, it would be a good thing to apply another organic fertilizer application to reduce infestation.

It has been my experience that the overuse of water related to our lawns is that we water too frequently and for too short a period of time.  As a result, the water used is truly being wasted.  When we first come on a property and check their irrigation system nine times out of ten we find that it is set to run three times a day (morning, mid-day and late day), for fifteen – twenty minutes at a time.  So in essence by using an automatic system one is watering 45 – 60 minutes per day, seven days a week.  In reality if one did that just one day a week their lawn would receive a good soaking.  However, they would also need to change from watering three times a day back to watering only once per day.

It is also important to realize that watering needs change depending on time of season and what you are hoping to accomplish. 

New Lawns - As I’ve stated elsewhere, the best time to start a lawn from scratch is the fall.  While most folks want to start a new lawn as soon as the snow disappears in the spring; such an approach is not the best.  If you are fortunate enough to get the lawn started; then you need to keep it going through the heat of the summer.  This naturally will require greater water usage than if one waited until late-summer or early-fall to begin.

Over-seeded Areas – Water twice a day for approximately 10 – 15 minutes, mid morning & afternoon, to ensure soil and seed stay moist – not wet.   Maintain watering schedule until seed germinates, approximately two – three weeks.  Once the seed germinates, cut back watering to once per day in the morning, then every other day, then twice per week as the root system gets establishes. Once germination is complete you need to water 1 inch weekly to maintain a healthy lawn.  Grass can take up to 18 months to become fully established. Avoid watering late in the day.  During times of excessive heat more frequent watering is required.   Mow at 3-3 ½ inches to shade the soil and hold in moisture for the new seedlings.

Lawns do not need to be green all season long.  If you have a healthy established lawn it is ok and in fact natural for the lawn to go dormant in the heat of the summer.  It will return in late summer – early fall as nights get cooler, dew will collect on the lawn and the early morning and the lawn will come out of dormancy.

How do you do that?  Take some time off from mowing.  Give yourself some rest, too!  Allow your athletic fields that you have been mowing at 2 ½ inches to grow longer.  Raise your mower heights to

3 ½ – 4 inches.  Keep them at this height until August. 

This will allow the grass on your athletic fields to carry on more photosynthesis and put down deeper roots.  This will make the turf on your athletic fields more wear resistant come the fall when the heavy hitters get out there; football, soccer and field hockey.

Take a rest, your fields will thank you.