In the Strike Zone. Weather

Transcription

1 Weather Combined with a cool latter half of March, a chilly and sometimes freezing start to April put the brakes on spring and plant growth in the central and eastern portion of the state. Columbia and St. Louis are 2 4 degrees below normal for April and have experienced a few frosts in the past few days. Conversely, Kansas City and Springfield are a degree or two above normal temperatures, and are progressing considerably more quickly into spring than the East. This is an odd temperature dichotomy since the progression into spring is normally switched with St. Louis being ahead of KC. Most areas of the state received some rain, with the I-44 corridor getting the most out of last week s storms. Columbia and the Kansas City area are still a little dry, running inch below normal thus far in April. Forecasts indicate temperatures will rise in through the middle of April, which should put us on track for fungicide application thresholds (see below). Along with this temperature increase, we also have a decent chance for rainfall across the state over the next two weeks. A bit of dollar spot and potentially a lot of large patch could result from these conditions.

2 Quick Hits: Fairy Ring Prevention with DMIs: By all forecasts and trends, the entire state will be squarely in the zone for the first of two preventive DMI applications for fairy ring control on golf putting greens. The 5-day average 2 soil temperature in Springfield

3 have reached and stayed in the F threshold range from April 6 th til present. Kansas City has flirted with the range since April 5 th diving in and out, while St. Louis and Columbia have been out of range. With current daily soil temperatures back into the low to mid 50s and the forecasts indicating a warming trend over the weekend, I expect the entire region will be in the range by next week. To recap the strategy briefly, (which can also be found in more detail here), next week will be the time in Missouri for a low rate application of one of the DMI fungicides triadimefon (i.e. Bayleton), tebuconazole (i.e. Torque), triticonazole (i.e. Trinity), or metconazole (i.e. Tourney). Twenty eight days later make a second application. Both applications MUST be watered in with 1/8 ¼ inch of post application irrigation, preferably immediately after treatment. I had an inquiry late last week from a Missouri superintendent who had made the application in early March during our early scare of spring temperatures. If also in this boat, don t feel like this was a wasted application, since you may have staved off some early dollar spot activity. I do recommend a three application strategy, however, making the second application 28 days from the first in April, and a third application 28 days later in May. This split-split-split application strategy will provide a better residual and more effectively provide fairy ring control. Powdery Mildew on Kentucky Bluegrass: I did observe an extremely minor powdery mildew outbreak on fall-seeded HGT Kentucky bluegrass lawn last week. The spot gets a bit of evening shade, and the constant wet leaves and young susceptible leaves made for a prime environment. This disease is normally just a mild nuisance and curiosity, usually doing very little damage to Kentucky bluegrass in this region and requiring no fungicide treatment. The odd white powdery mycelium covering the leaf blades can raise the eyebrows of a homeowner, but does little harm to the plant and will do no harm to them, their children, or pets.

4 Strike Out Large Patch Now Along with being in the strike zone for fairy ring prevention, it s also time to hit the plate for preventing large patch in areas that are prone (saturated, low lying, or shady areas) and have a history of the disease. Our research consistently shows a single fungicide application made in early (on dormant zoysia) or late April when zoysia has greened up to approximately 50% provides better control than single applications made the previous fall. In Missouri, spring is our season for the most extreme large patch symptoms and spread. Additionally, homeowners and superintendents alike expect a solid spring green up that will produce pristine turf over the next six months. A severe epidemic of large patch now can set that process back and allow weed encroachment. Expecting one or even two fall fungicide applications to last through the fall and melt of snow and rain for the 6-7 months until May or June is a stretch. In a home lawn situation with large patch history and where you might only get one fungicide application to target this disease, this is the time to take it. On golf fairways, if a single application was made last fall it should be supplemented with another this spring to ensure control on prime large patch areas. If two fall applications were made, scout routinely and be ready to hit bad areas if they start to fire. Not sure if a property has had a history of large patch? Google it! Download Google Earth and survey a fairly consistent record of satellite imagery of different seasons from the past 13 years. Pay attention to fall (Sept Nov) and spring (Apr Jun) months, and, as the name implies, severe infestations of large patch should be fairly apparent. Google Earth should be also useful for determining the history of other turfgrass or tree related problems, and would be a great tool for turfgrass managers maintaining a new, unfamiliar site.

5 Lee Miller Follow on Like on Facebook! Mizzou Turfgrass Extension Turfgrass Pathologist - University of Missouri