Environmentally Friendly Turf Management
QDPI Redlands Research Station, Cleveland.
The professional turf industry has made great headway over the last few years in reducing the amount of chemicals used to maintain turf. This has happened because of increasing awareness of soil and plant health, education about Integrated Pest Management (IPM) and the availability of a number of new products to use in an IPM program. Many of these principles and products are available to the homeowner, so let’s look at a few.
Plants have the ability to manufacture natural toxins to resist many pests. These natural toxins such as phytoalexins (with anti-fungal compounds) and alkaloids (toxic to insects and nematodes) are kept in reserve by the plant, and only produced after an initial attack by the pest. Caffeine, nicotine and morphine are examples of natural alkaloids by the way – all these are nerve toxins, with very similar properties to chemical insecticides. But here’s the catch – only healthy plants have the ability to produce adequate quantities of these natural resistance chemicals. That’s why fungal pathogens and insects usually target unhealthy plants, because their natural resistance will be low. So we need to encourage healthy plants. The essential points in encouraging healthy plants can be summarized as:
1. Select the right grass for the location. Factors like shade, soil pH, availability of water, the amount of traffic and the amount of nutrition will all affect the decision on the most suitable grass for a particular site.
2. Fertilize correctly (see below).
3. Irrigate for maximum root depth – deep, infrequent watering only when the grass shows early signs of moisture stress.
4. Obey the 1/3 mowing rule – never mow off more than 1/3 of the grass leaf at any one time. For most people this means more frequent mowing, unfortunately. On the plus side you won’t have masses of clippings, and using a mulching mower is practical.
5. Improve the site – reduce soil compaction, increase air circulation and improve drainage to give the plant a good chance at being healthy.
Nearly all weeds are well controlled by the plant health measures listed above. There may still be some flatweeds and probably a few creeping grass species able to invade, however, so some limited herbicide use is probably necessary. Products like ‘Weed and Feed’ work extremely well on flatweeds, but creeping grass weeds (which are nearly impossible to hand weed) would probably be better treated with a touch application of glyphosate (e.g. on a paint brush). These products have good environmental credentials and low toxicity.
Plants are highly competitive. Any resources such as light, water and nutrients are grabbed as quickly as possible, both to benefit the plant and to prevent neighbouring plants from growing stronger. In nature, plants get their nutrients in a slow but steady trickle, mainly from the decomposition of organic matter. The slow supply of nutrients and their competitive behaviour means that plants have adapted, over millions of years, to taking in all available nutrients as quickly as they can. This works fine in nature, but we can create problems when using chemical fertilizer which are readily dissolved and available to the plant. You can measure out and apply a rate of fertilizer that should satisfy a lawn for several months, but no one told the grass that. The plant will take in all that fertilizer as quickly as it can, even if it makes it sick and unhealthy. Professional Turf Managers get around this by applying very small doses of fertilizer at very frequent intervals, sometimes every week. How can we manage this better on a home lawn?
If you’re not going to apply very low doses on a very frequent (1-2 weekly) program, then you should look at Slow Release fertilizers. These can be chemical slow release products (you are probably familiar with Osmocote, for example). Or they can be the original slow release fertilizer of them all – an organic fertilizer. Products made from animal manures or processing by-products (e.g. Blood and Bone, Fishmeal etc.) all make excellent lawn fertilizers with in –built slow release properties. Not only will these promote healthier plants, they will also promote beneficial soil microbes that help aerate the soil, decompose thatch and reduce pest and disease problems.
Some organic fertilizer products such as the seaweed products and the Nutri-Gro range of fertilizers incorporate natural plant stimulants (called biostimulants) and natural plant oils to deter insect pests and encourage better root production. These products are used widely in the professional turf industry.
Good aeration and good chemistry (pH, salt and nutrient levels) are important in soil health, but increasingly the turf industry is turning towards products that enhance soil microbiology. Most of the millions of bacteria, fungi, actinomycetes and soil microfauna (microscopic soil animals) in the soil are beneficial, providing essential nutrients and stimulants to the plants and protecting their roots from a range of fungal pathogens, insects and nematode pests. Natural manure products, as mentioned above, provide good steady nutrition to the plant, as well as to the soil microbes. Products such as sugar or molasses, on the other hand, are not actually taken in by the plant and are intended purely to encourage soil microbes.
Controlling Insects Pests
It’s now possible for professional Turf Managers to control insect pests completely using biological control products. All chemical insecticides on the market are nerve toxins, and as humans, birds and fish all have a nervous system, we are at risk too. Being able to rid golf courses, bowling greens and sporting ovals of the need for chemical insecticides has been a huge step forward for the turf industry.
The main biological weapon in the arsenal is Entomopathogenic Nematodes (ENs). ENs are microscopic roundworms, natural soil inhabitants that have the ability to burrow into a wide range of soil insect pests and parisitise them, eventually killing them. Research by the CSIRO has resulted in a process whereby ENs are mass produced in a ‘factory’ environment, and produced in a convenient form for pest control. They effectively kill a wide range of pests (e.g. Beetle/cockchafer pests, cutworms and other grubs) with no off-target effects (i.e. they’re harmless to humans, wildlife, even earthworms in the soil). ENs have revolutionized insect pest control in turf. Look for the poster on ENs at the field day and check availability with Nuturf suppliers or Ecogrow.
CSIRO research has also resulted in the release of a natural fungus (Metarhizium anisoplae) for the control of Red Headed Cockchafer. This is probably more a concern in Victoria and Tasmania, but it again demonstrates the excellent efforts by CSIRO to provide effective biological control products.
Keep it Simple
While the turf industry is happy to see and use a good range of environmentally friendly treatments, it is plagued by ‘witch doctor’ products that are marketed as clean and green, and a cure for all problems known to man. Many of these are no better than green cordial, and are extremely expensive. The manufacturers of such products are not required to back up their claims, and often make good profits before it becomes obvious that the thing doesn’t work. Recent trial work in Sydney and Melbourne has demonstrated that some of the most expensive of these products do absolutely nothing to improve turf health or reduce pest problems. But that’s no reason to reject the environmental approach – just keep it simple. Some suggestions that are sure to work are:
1. Select the right turf species for your location. Get advice if you’re not sure.
2. Mow more frequently, not taking as much leaf off.
3. Irrigate infrequently and deeply, when the plant shows it needs it.
4. Use simple organic fertilizers, such as animal manures and other organics.
5. Control insect pests with ENs, they work beautifully.
6. If you’d like to try it and you can get hold of it cheaply, encourage soil microbes by adding molasses to the lawn. You won’t see a thing in the short term, but the microbes will appreciate it and pay you back eventually.
© The State of Queensland, Department of Primary Industries and Fisheries 2008 (work reproduced with the kind permission of the Department of Primary Industry and Fisheries).
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