Friday, May 1, 2009

Large Patch in zoysia

Our zoysia on the course can be susceptible to a disease in the early fall and middle spring of the year. The disease is more active in the spring because of the cooler temperatures and heavier moisture conditions. The disease that I am describing is called Large Patch. The disease is not a devastating disease if treated preventatively. This disease is normally limited because of our treatment schedule but if the conditions are right, it can become active and can break through our fall treatment. A member and guest might notice this disease because of its bright orange color against the dark green of the zoysia turf. There are sometimes multiple diseased spots within a given area which can make it more obvious to you that something is a bit unusual in that part of the fairway or tee.

We made a preventive application of fungicide in the fall to discourage the disease from starting. The reason why a disease becomes active and creates damage is because the organism that causes the damage becomes very high in numbers in the soil and or on the plant and will begin to cause health issues for the plant. Cultural practices which improve the soil condition around the plants are important in trying to keep disease in check but sometimes we must resort to the last cultural practice which is spraying chemicals.
There are other physical and environmental factors which can increase or decrease the pressure from a disease. Below are just a few of these factors.
  1. Fertilization

  2. Aeration is usually always an improvement to a condition but sometimes can lead to damaging turf if completed during severe temperature or moisture events.

  3. Temperature.

  4. Moisture levels.

  5. Air movement.

  6. Physical damage from mowing, dragging or topdressing.

An increase in heat last week was great for allowing our warm season turf to grow but it also increased the soil temperatures which is one of the factors that brings on the large patch disease. The temperature of the soil has to get high enough for the disease to grow in the soil. Almost everything having to do with turfgrass either good and or bad has to do with soil temperature levels. Turf does not grow until certain temperature levels occur but also diseases do not increase until the right temperature encourage the growth of certain bad organisms either in the soil or along the base of a plant. The other factor which has encouraged this disease to become active has been an increase in moisture and then cooler temperatures which has happened this week. The following pictures will give you a few examples of what the disease looks like on our turf. We did a curative application on these spots and will be scouting for other areas that will need additional treatments. It is difficult for us to see every spot of zoysia so we have taken our operators out into the field and did some education in regards to how to spot the disease. Five or six pairs of eyes are always better than two or three when it comes to trying to find problems on the golf course.

This spot is on the left side of 13 as you begin to go up the hill. The orange ring is the active area of disease. The darker area is some bermuda that we are attempting to kill with our fairway treatments which have been applied twice since fall.

This is a classic example of the disease. This is in the same area as the picture above but has started in the intermediate rough and part of the left side of the ring is in the fairway. The lighter or straw looking turf has been damaged but should recover.

This spot is on the right side of #5 fairway. Another classic ring but the interesting part of this ring is that it is only 1/2 a ring. At each end of the ring is bermuda grass which is not normally susceptible to this disease. The only problem with that statement is that we have some real activity on the 8th approach fairway on the fine leafed "Baby" bermuda grass. I believe some of the material on the inside of this ring that is bleached out is also some of the other finer leafed "U3" variety of bermuda that is on the course which has been slow to come out of the dormancy of winter.

This is a close up of the ring above. My radio which is about 4 inches long gives you an idea of the width of this active ring. Some rings are only an inch or two wide. They vary in size but are normally round in shape.

There are a number of cultural practices which we utilize to reduce the impact of this disease.

  1. Aerate regularly to reduce thatch.

  2. Reducing irrigation in the fall which helps discourage the formation of the disease in the fall. Disease that forms in the fall can potentially activate in the same area in the spring.

  3. Do not fertilize fairways until warmer temperatures in mid-spring/May or until increased temperatures and disease is not actively growing.

  4. Do not aerate in the spring. Cores can move disease to different areas of the course that are not currently infected.

  5. Apply preventive(before disease occurs) in the fall and curative(treat when you see disease)in the spring.

No comments: