Fungus likely to blame for spots in lawn
Lawns are getting toasted right now. This is a stressful time of year for plants, particularly those that are not truly desert plants. Temperatures are out of their “comfort zone” and they become susceptible to diseases because they are less capable of fighting through a problem.
Q: I believe I am dealing with some fungal outbreak on my new lawn. About a month ago I started to see faint circles of stressed lawn. They range from 24- 48 inches wide. They are certainly not dog urine spots. I know the difference. Also, I’m confident it’s not a watering problem. All spring and early summer the lawn has been healthy . But now these circles are appearing everywhere. Do I need to just throw in the towel and start over?
A: This is most likely a fungal disease called summer patch. Buy a lawn fungicide that says it controls summer patch, Fusarium diseases or “frog eye” on the label. Follow the label’s directions precisely . If the label states it controls necrotic ring spot as well, so much the better .
Fungicides are primarily preventive, so making an application now will stop the disease from going any further but not reverse the damage done.
This is a hot-weather lawn disease and favors soils that stay wet and don’t drain readily. You can always expect it to occur when temperatures are rising and become aggressive during the summer monsoon season when relative humidity takes a bump .
Next year anticipate an outbreak to start in June and make your preventive fungicide application then or when you start to see those faint circles .
I would aerate the soil now, as well. You can use a simple hand aerator or you can rent a power aerator . Don’t use shoes with the spikes on the bottom. They are a gimmick.
Remember this problem area in the future. Before the onset of hot weather, aerate to improve water drainage from the area around grass roots. Mow the lawn at its minimum acceptable height (usually 1½ inch for tall fescue) to improve air circulation .
Avoid excessive applications of nitrogen fertilizers but keep the lawn fertilized adequately. This will usually mean about half the label rate mentioned for lawns on the fertilizer bag.
This is particularly true if you are mulching the clippings back into the lawn with a mulching mower. Returning the clippings to the lawn with the mulching mower has no bearing on this disease.
Q: I have a 5-year-old date palm that had a wonderful display of fruit for the first time this year. It is a Medjool date palm that I grew from seed. The fruits are at least 1½ inches long and round. But now they are falling off in great numbers. I thought that birds were on them thinking they were grapes, which I have nearby. I have covered the Medjool dates with cloth and still they are almost all gone. Another date palm nearby, a Deglet Noor (8 years old), has great fruit set but very few drops. Could it be that my Medjool has not been pollinated?
A: Exactly right. The fruits dropping have not been pollinated. No or poor pollination can happen for a number of reasons but I am guessing there was no male pollinator in the area with open flowers.
What can you can do, outside of planting a male Medjool palm, is create a source of pollen and hand pollinate the female flower clusters when they open.
You will have to find a male Medjool date palm (flowers will be produced at the same time as the female ) that is low enough to the ground for you to reach. When the male tree is producing its floral spike early next summer and near flowering, prune several spikes and put them in a clean bucket of water. Move the bucket close to the base of your palm and let the flowers open. Replace the water daily with clean water.
When the flowers open, shake the male flower spike and flowers pretty hard against the female spike . Replace the male flower spike in the bucket of water and repeat for the next couple of days as more flowers open.
Alternatively, you can tie the male flower spike to the female flower spike and cover with a bag. Beat the bag pretty hard and leave the bag in place for a couple of days and then remove.
Q: Our cactus has started to die from the top down. We lost our first one in May, before the summer heat even started. Do you have any idea why this is happening? We were watering, with bubblers, three times a week, for about five minutes. We increased that when they started to die, but it did no good .
A: Wow, judging from the pictures you sent you do have a problem. This looks like one of the cereus or night-blooming cactuses, a pitaya type.
When did you see this happening? This looks very similar to freeze damage from the winter. If you are just seeing this now, then, of course, it is not. If you are watering too often and not giving it a break of dry soil between waterings, another possibility is root rot.
Three times a week is going to be excessive for this plant and may be the problem. The plant would prefer a large amount of water and then long times between waterings, much like rainfall in dry climates. But, the bottom line is that the soil needs to dry thoroughly between waterings to prevent root rot.
When planting, make sure the soil is amended with some good stuff. Cactuses can survive poor soils better than many plants but they perform better with an enriched environment .
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.
