Four weeks ago, right?? Because rye grass sprouts in 1 week. KBG takes 3 weeks of continuous moisture to germinate. When you say "it came in very well," the KBG has not come in yet. All we see here is rye. Have you been doing your daily watering religiously for the past 3 weeks? In other words, are you sure you have any germinated KBG in there?

For the reason mentioned above, the rye mixed with KBG is not a good one. People see the rye come in like gang busters and think they can stop the daily watering. Now assuming you continued the daily watering, then you can develop what you have developed. So there are problems mixing rye with KBG.

You're probably asking for identification so you can buy the right chemical fungicide. Is that correct? There is an organic solution which usually kills the most popular fungal diseases regardless of what disease you have. The material is ordinary corn meal. When corn meal decomposes it attracts a predatory fungus called trichoderma. The trichoderma fungus feeds at first on the various fungi which are decomposing the corn. When those "feeder fungi" are gone, the trichoderma will attack the disease fungus. Like most organic products, the entire process takes about 3 weeks to see results. I've successfully killed the fungus in my lawn every year since 2002 using corn meal. Cracked corn also works. You can get corn meal or cracked corn at your local feed store in 50-pound bags. Use at the rate of 20 pounds per 1,000 square feet.