The Perennial Problem

It's been a while since I penned a few words for Pitchcare. The winter and spring have been exceptionally busy, and so it's a relief to be writing this article from two points of view.

The first is I can write about a subject that is close to most of us - controlling weeds, and not the seemingly endless rounds of impenetrable cobblers that come from Europe. The second point of view is that, as I write, spring is here! Last week the resident swallows arrived and the riot of noise and activity that they bring with them has kicked off. It's like the first asparagus or strawberry of the year - a beginning to the next chapter of the season.

If the old proverb is to be believed we should (fingers crossed) have a 'normal' year this year. Oak before ash and we shall have a splash, Ash before Oak and we shall have a soak. In Cheshire the Oaks won by two whole weeks which, I hope, means we will have a long dry summer.

The previous two years have made life tough. Soft ground and persistent rain made travelling on turf tricky, and the days available to spray limited. So, it's understandable that many pitches and courses simply didn't get the chance to follow through with their weed control. So, this year, it is important to take advantage and catch up. The recession may make people nervous on committing to weed control, but the weeds don't care and will carry on regardless.

So what makes a good turf weed?

In essence, a weed that can adapt to the regime we put grass through to make the surfaces we need to play our games on. Take the humble buttercup. In a meadow the creeping buttercup grows as tall as most of the grasses around it. On a golf course it grows flat to the floor to avoid being mown. It is able to adapt its growth habit to the constant trimming we subject it to. This applies similarly to plantains, white clover, and the good old daisy. So, given the ability of the weeds to adapt to our mower blades, they also need to spread. They have adapted here, too.

Plants are lucky. They can perpetuate themselves, either with the help of a willing partner - seeding - or, if they don't have that option, some can spread through propagation, or with runners. The weeds that spread this way are often the hardest to control, as each runner they put out allows a new point from which to draw nutrients and water, to sustain either the whole mother plant, or a new individual.

Good examples of this are slender speedwell and, again, the creeping buttercup. Other ways to spread are via a big storage body - the perenating organ. Daisies and dandelions are the most common examples of perennials with this type of structure. They have a whacking great root that, when needed, can also adapt to propagate new individuals if the plant is attacked or disturbed. Fragments of the root are easily capable of becoming a new individual.

Docks are famous for being able to re-grow from root fragments. A 1cm section of a dock root is all it takes to grow into another plant! This may be bad from the point of view of a perpetual weed problem - but the smart thinkers amongst us know this can be a weakness we can exploit, too. Read on.

Without doubt the toughest turf weeds to keep control of are the perennials. The annual weeds are less of a challenge - but they have their tricks as well!
Annuals have one season to get through an entire life cycle. So, to ensure success, they have the Chinese army approach - lots and lots of seeds. As they seed so prolifically, the seed matures and germinates over a period of time. After the initial flush the germination tails off. This is crucial to understand; knowing this pattern in germination is another trait we can exploit when putting together a plan to control weeds in turf.

In addition to the plants, all the pitches and courses have an unseen reserve of weeds just waiting for their chance. The seed bank. A well managed grass sward is ideal at keeping out the newly germinated weeds, and preventing germination. But, there are opportunities that present themselves - and the weeds take their chance. Worm casts are a good chance. When the worms form casts they place soil bearing weed seeds in the ideal place to germinate, with no chance of the grass sward suppressing them. Gaps left from successfully treated weeds are often rapidly used by germinating opportunists. And again - we know this and so can plan to prevent it.

Integrated Pest Management or IPM.

Put in simple terms, it's using all the tools in the box to achieve the optimum desired outcome for the grass you are managing. Never rely on any one tool, as it has gaps - use all of them together to minimise these gaps. This applies to all aspects of pest and disease management, but here I am focusing on weeds.

The first part is nutrition. Weeds thrive in a man made grassland environment as there is an abundance of available nitrogen. This free boost to their growth really speeds up their development and enables them to dominate the sward. The solution here is soil testing. Look at turf nutrition as a year long exercise in providing enough nitrogen potassium and phosphate to enable a healthy, vigorous sward, and no more.

Over the year the goal should be to end at the same levels of soil nutrients that you started with - so you balance. Knowing your nutrient levels, by soil testing, tells you this, so you can plan your nutrition inputs. The availability of nutrition should be considered carefully, too. After calculating what N P K levels are needed, then supplying them to the rootzone needs to be controlled. Slow release products are the way forward here. A controlled and sustained release of what is needed is a far better than a surge of nitrogen that will lead to quick growth of weak grass, but very strong weed growth. This will also keep your mowing manageable - you won't be chasing grass that is trying to become hay.

Compaction is a problem that occurs mostly on sports pitches, but does promote an environment that certain turf weeds thrive in. Plantains of all varieties are a key symptom of soil compaction.

Winter sports pitches are especially vulnerable to compaction, which leads to the grass establishing slower and growing less vigorously. Its ability to regenerate and form a competitive sward is reduced. The solution here is decompaction to allow the grass to flourish. An expensive investment but, seen as part of a programme planned over years, the cost can be budgeted for depending on the frequency it is needed. Other benefits are vastly improved aeration and drainage - but that is another article in itself.

Treatment with herbicides is the next aspect of IPM. It is also the solution that has the quickest impact and the most predictable outcome, but works far better with results that are sustained longer when put into action with the other points mentioned.

So, we have two types of weeds. The annuals and the perennials. Both germinate or emerge at different times and over a period of months. This poses the question when to treat? If you are too keen and treat too early you will only catch a fraction of the spring annual flush. The ones that germinate after you spray will taunt you for the rest of the season! If you spray too late, you will catch a far higher proportion of the annuals and the perennials that emerge slightly later. But, waiting might not please the membership so, a fine balance is needed. The watch words here are hurry up and wait. The longer you leave your planned spring spray the more weeds you will treat. The more weeds you treat the better value you are getting from the treatment you are putting down. This further reduces the weeds in your bank - eroding what will come back at you in the future.

Effective timing is just one aspect of getting your weed control right. Selecting the right product is also crucial. If you choose the wrong product, and you get ineffective control as the weeds aren't listed as susceptible on the product label, you haven't solved your problem. Identifying the weeds you have and selecting the product that treats what you have then is crucial.

If you have the usual suspects (plantains, white clover, dandelions and daisies, with one or two others) then a good three way selective will achieve a good result. If you have tricky weeds such as slender speedwell, woodrush, and yellow trefoil you need a more potent (and sadly expensive) product that will deliver a result. If you are uncertain then get advice - a BASIS qualified advisor will certainly help make the informed choice and recommendation.
Herbicides only work as well as they are applied. Take care when applying them - and set up you sprayer specifically to do the job. Herbicides and fungicides work very differently and are applied to different parts of the sward.

The key is getting the water volume correct to achieve good coverage on the weeds with a spray droplet size that will achieve this. Coarse droplets will bounce off or roll off a well waxed leaf. Medium and fine droplets are stickier and give better coverage, but need to be used when the wind is low to avoid drift. Water volumes of 150 to 250 litres per hectare are ideal for sportsturf, as all you are hitting is a prostrate open target sitting on top of the grass. When work is peaking, from April to August, it may be you don't have the time to spray yourself. Contractors are ideal for helping here, but choose a good one! Make sure they are a sportsturf specialist with specialist equipment.

Depending on what suits your operations, early autumn is the ideal time to treat persistent and perennial weeds. This timing takes advantage of their biology - at this time of year they are sending their nutrients down to their deep roots for next year. Taking advantage of this nutrient flow you can get far deeper penetration into the plant with a herbicide, giving a higher level of control. The results may not be immediately appreciable, but the following spring there is a significant difference.

Weed control is best viewed as a programmed approach, along with overall management. The trick is to use cultural methods to suppress the weeds to the point where spraying is needed, and then when you do spray, make every drop count.
Follow up.

After you have treated your weeds you can predict that they will leave gaps where they once were. Plan to take advantage of this by overseeding and feeding with a good rooting promoter shortly after the weeds have begun to die off properly. This will block out any opportunist germinators, and create a gap free sward that will block out a high proportion of weeds that are waiting for their place in the sun.

Paul Cawood,
Business Development
Manager,
LanGuard Ltd
Tel: 07738 885 703
www.languard.co.uk