December 2011, – PUTTING UP DEFENCES AGAINST DISEASE ATTACKS

BOWLING greens are susceptible to a number of diseases, many of which can either be prevented or controlled by good green management and maintenance, and over the coming months we will be looking at some of the diseases that can create nightmares for our greenkeepers.

Fungi, along with bacteria, mosses, liveworts and algae, belong to the lowest order of the plant kingdom called Thallophyta, and fungi forms the biggest part of this group. Where the word fungi crops up, we immediately think of mushrooms, toadstools, puff balls in turf and bracket fungi on trees. In other words, what we see is equivalent to a flowering/fruiting part, but in reality the actual fungi is active either within the soil or on a tree.

The fungi that is visible is the end product of the fungi disease that is prepared to spread its microscopic spores which are the equivalent of seeds in plants. The spores are held underneath in the fins of toadstools and mushrooms, but inside puff balls and when ripe these spores are released and carried either by the wind, or sometimes animals, to land on a suitable surface for germination.

Their function is to search for suitable nutrients to supply their own needs. These are in the main sugars and starches locked in their environment that they need to grow because they do not contain chlorophyll in their make-up (green colouring matter).

They also assist in the breakdown of the organic matter and to be further broken down by bacteria and other soil life to be used by the plants that do make their own sugars and starches. A fungus has to steal its life requirements from other sources.

Fungi form hyphae which are very fine filaments searching for food in the pore spaces in soil and are called mycelium. This mycelium has a wafty cottonwool like appearance and searches out for organic material needing to be broken down, but in the process what is left behind as it progresses is a waxy like material that is waterproof and fills up the pore spaces in the soil that prevents moisture permeating down into the soil between the particles.

An abundance of thatch is an ideal breeding ground for fungi activity, especially if the weather conditions are right – wet and warm with a temperature between 42F-45F or 5C-7C.

We have described the waxy appearance of some fungi, which enables it to resist the effect of being washed away or leached out of the soil. One can see that it is not exactly similar to a grass plant or any other plant life. It is like a leech or parasite that extracts goodness from others – dismembers or breaks down the cell structure of the host plant.

Lack of maintenance of turf in scarifying to remove dead, dying, decaying and diseased materials, and lack of aeration will all contribute to the spread of fungi, as this grass debris is all natural food for fungi to feed on.

When the pore spaces in between the soil are filled up with this waxy material and become impermeable to water, this can result in the possibility of poor quality turf and this is why aeration is essential.

Spiking allows air into the surface and in turn water can get through to the lower levels to assist the recovery of the turf. This is why regular maintenance operations are so important in turf culture.

ONE of the most common diseases on our bowling greens is Fusarium, which in the main attacks annual meadow grass.

When the conditions are right – wet and warm with temperatures between 5C-7C – Fusarium attacks the basal sheaves of the annual meadow grass and shows as a discolouring of a brown moist circular ring shape which as the disease increases begin to coalesce (join together) to make much larger patches of this sickly brown phenomenon.

On closer inspection you will see that it is the very outside of the leaf that is affected first. If the damp, muggy conditions persist then the disease takes a much stronger hold and can envelop the whole of the annual meadow grass plants.

It has often been noticed that the grass stays greener for a much longer period and if we do have a further change in the weather then this starts to grow and partially recover, but the rest of the plant adds to the thatch in the turf and can be severely disfigured.

The practical way of dealing with Fusarium attacks is to carry out regular, thorough scarifying, particularly in the autumn, to clean out the debris. Make several passes with the scarifier set lightly into the turf, but not touching the soil, and change the direction frequently. Daily dew removal to raise temperature at soil level is also vital towards the prevention of this disease.