Happy Summer! June 20th marked the start of the summer season. Summer means a good time for cookouts, picnics, swimming, and grub control. Not exactly what you had in mind for summer fun? Knowing the pest and its habits can help keep you from spending all of your summer fun time dealing with grubs.
This past week was a blur of calls, questions, and visits to homes and fields but it was a great week and flew by staying very busy! I’ll touch on a few of the common questions I’ve received this week.
Trees: Some trees such as willows, hackberries, tops of maple trees, ash, and black walnut are just taking time leafing out. Some trees leafed out once already and dropped leaves. Things that may have caused this were the sudden flux of temperatures from very warm to cool and the strong winds we received. Some trees have also unfortunately had herbicide drift damage that caused leaves to drop. On those trees, watch for new buds as nearly every situation I’ve looked at thus far have new buds forming after about a week-10 days. With all these situations, give the trees a few weeks to leaf out again and if they’re still not doing it, feel free to give me a call. Trees are interesting plants as sometimes environmental impacts that happened 3-5 years ago will show up that much later-and sometimes environmental impacts show up right away!
Disease/Insect issues: This year has been a strange year all around but with our warm winter, I was concerned about an increase in diseases and insects. Thus far, we’re experiencing increases in both-so hang on-it may be a long growing season! Our high humidity, warm temps, and heavy dews have created perfect conditions for fungal diseases on our trees, ornamental plants, lawns (I’m currently fighting a bad case of powdery mildew-as a plant pathologist it is kind of pretty but I don’t like what it’s doing to my lawn!), and in our wheat and alfalfa crops and some pasture grasses. Fungicides may help in some of these situations, increasing airflow can also help as can more resistant varieties or hoping the weather will change. In the case of most ornamentals, we don’t usually recommend doing anything. The same goes for insects as insecticides can help in some situations. I’ve received several calls this past week of people afraid they had herbicide drift damage. While there were a few cases of that, many of the cases were actually fungal leaf spots on leaves. There are various fungicides and insecticide products available from home/garden centers, etc. Be sure to read and follow all label directions and only apply the product on places the label specifies it can be applied.
Crops Update: Later this week we may have a better idea on the extent of storm damage and if some fields will need to be replanted after the storms from last week. Dr. Bob Nielsen from Purdue University reported that most agronomists believe young corn can survive up to about four days of ponding if temperatures are relatively cool (mid-60’s F or cooler); fewer days if temperatures are warm (mid-70’s F or warmer). Soil oxygen is depleted within about 48 hours of saturation and we know soil oxygen is important for the root system and all the plant’s life functions. So we’ll have to wait and see what happens.
Have also had a few calls regarding rye cover crops. When rye is killed out and decomposing, it releases toxins that can affect the germination of other cereal crops such as corn if it’s going to be planted into that rye cover crop. Thus we recommend at UNL that the producer kill the rye and then wait at least two weeks to prevent any major damage to the crop. I realize at this point with the rains to get in and kill that crop on top of waiting an additional two weeks, we’re getting close to the end of the month and will most likely be looking at reduced yields…and depending on maturity, you may need to consider different seed if you end up having to plant in June. If you have specific questions about this, please let me know and we can talk through some situations.
Stripe rust and powdery mildew have been obliterating mid-lower canopies of many wheat fields. I’ve received several calls on why wheat canopies are yellow-that’s the main reason but other factors such as the dry spell prior to these rains and/or deficiencies in nitrogen/sulfur or some viruses may also have been factors. Wheat in Nuckolls County last week was beginning to flower. Fungicides such as Prosaro, Folicur, or Proline are labeled for up to 50% flowering and cannot be applied after that. Remember the wheat head begins pollination in the middle-so if you’re seeing little yellow anthers at the top or bottom of that head, you’re towards the end of flowering. All those products have a 30 day pre-harvest interval-which has been the other main question-are we going to be harvesting in a month? I do believe we’ll be harvesting a month earlier than normal just because pretty much everything in wheat development is about a month ahead of schedule. I still feel the 30 day window for the fungicide application is worth it with the large amount of disease pressure we’ve seen. Wheat in Clay Co. and north still may have time for a fungicide application; those products mentioned above will help prevent Fusarium Head Blight (scab) as well as kill the fungi causing disease already present on your leaves. A list of all fungicide products, pre-harvest restrictions, and rates can be found here. Also check out my previous blog post with video on scouting for wheat diseases.
The other major disease appearing in wheat is barley yellow dwarf virus. This is a virus vectored by bird cherry oat aphids which we were seeing earlier this year. Unfortunately, this disease causes the flag leaves to turn bright yellow-purple causing yield loss (at least 80% of the yield comes from the flag leaf) as there’s nothing you can do once the virus manifests itself in those leaves. If you have a large incidence of barley yellow dwarf in your fields, you may wish to reconsider spraying a fungicide as the fungicide won’t kill the virus; however, it will help kill the fungi on the remainder of your leaves and potentially help protect some yield from the two leaves below the flag leaf.
I really appreciated Gary Zoubek presenting at our lawn care workshop last Thursday! I also appreciated all the questions and good discussion; hopefully everyone walked away learning at least one new idea or tip!
One common question was what to do with areas that were killed out by summer patch last summer. Summer patch is a fungal disease that is favored by applying nitrogen too early in the spring, by a compromised root system by too wet of soils in the spring, by stress from summer heat, and irrigating in the evenings. Last year I was receiving calls from all over the County regarding this disease. Eventually affected areas can refill, but in many cases, that just didn’t happen. Preventive fungicides right now are recommended to help prevent the fungus from causing damage to your lawn again this summer.
So besides a preventive fungicide what can you do? The best time to reseed is actually in the fall. One option is to keep these areas weed-free including of crabgrass so that doesn’t overtake these areas. Reseed with a disease resistant variety in the fall following the recommendations in this extension circular.
Your other option is to reseed/overseed right now with a disease resistant variety knowing that you may fight crabgrass this first year. Overseeding and reseeding are recommended to occur from now through May 1 for Kentucky bluegrass and from now to early June for tall fescue. You can determine the correct timing of all lawn practices by visiting the turf calendar Web site. Simply choose whether you have Kentucky bluegrass or fescue. Click on a lawn practice and scroll the circle on the calendar area to the current month to find the recommendation for that time.
Some other tips regarding lawn care: sharpening lawn mower blades is key to not shredding the grass which can invite pathogens that cause disease; mulch lawn clippings as often as possible as they contain nitrogen that can be released back into the soil; use a fertilizer product with the highest amount of a slow release nitrogen as possible (check fine print on the fertilizer bag); and sweep or use a leaf blower to send all clippings and granular pesticides back onto the lawn as leaving them on the sidewalk allows for them to be washed into the gutters and eventually lakes and streams. Right now, a silvery colored fungus called powdery mildew is visible in places in lawns that are shady or have minimal air movement. We don’t typically recommend a fungicide as this disease is more aesthetic than harmful.
Here’s wishing you a nice lawn this summer! Also a reminder of our free Container Gardening workshop to be held April 19th from 5:30-7:00 p.m. at the Clay County Fairgrounds. Elizabeth Killinger, UNL Extension Educator, will be presenting on container gardening for vegetables and flowers, creating a few container gardens for door prizes, and provide creative ideas for container gardening. Please RSVP at 402-762-3644 so we can have a meal count, hope to see you there, and invite your friends!
Happy April! The weather sure has been interesting! Since my last columns, UNL has come out with some altered recommendations for turf. So letting you know that according to Zac Reicher, Professor of Turfgrass Science, he is recommending an application at 50% of the high label rate rate of crabgrass control now in the form of dithiopyr and then plan on making a sequential application at 50% of the high label rate in early to mid-June with a dithiopyr product. Crabgrass is already emerging and this product helps with grass that’s already emerged as well as controlling crabgrass pre-emerge.
Also information from Zac: Preemergence herbicide applications for broadleaves can start anytime now and assuming typical weather, sequential applications should be planned for in June. Almost all of the current preemergence herbicides (dithiopyr, pendiamethalin, prodiamine) are available as fertilizer/herbicide combinations, but cool-season grasses need little nitrogen in the early spring regardless if it is in March this year or late April in most years. Therefore, it is important to use a herbicide/fertilizer combination with as little nitrogen as possible to avoid a large growth flush and maximize long-term health of the plant. The problem is finding a product with little or no N. If you find a selection of products, do some quick math and calculate which product delivers the lowest amount of N/1000 sq ft, preferably 0.50 to 0.75 lbs N/1000 sq ft. Additionally, slow release N will extend the window of N release and minimize the potential growth spike after application. Slow release sources include sulfur- or polymer-coated urea, urea formaldehyde, methylenediurea, dimethylenetriurea, or natural organic nitrogen. These are listed on the label as “slowly water soluble” or “water insoluble”. Pay special attention to N sources followed by an asterisk and be sure read and follow the entire label of any product you apply. With the unusual weather this year and the increased need for sequential applications, each application usually applies about 50 to 75% of that which would be applied when using a single application. Applying two applications at lower rates will also reduce the nitrogen applied in each application, which is beneficial at this time of year.
The following sources explain more about the math calculations:
• Update: Warm soils and forecast are revising recommendations for preemergence herbicides
• Lawn Care Pro Series: Crabgrass and Other Summer Annual Grasses
• Do it yourself: Choosing preemergence herbicides
• Crabgrass Control in Homelawns
The strange weather has allowed for an uncommon turf disease to begin appearing in this area of the State. Ascochyta leaf blight typically is found in places like Colorado, but this year, it’s showing up in Clay and other areas of Nebraska. Typically the fungal pathogen is favored by hot, dry weather preceded by cool, wet weather-exactly what we’ve had up till this recent wet spell-which also favors the pathogen. Symptoms include the leaf blades turning straw colored or bleached and dying back from the tips. Eventually patches of turf may appear straw colored.
There’s nothing recommended for this disease except to manage your turf properly-mowing at proper height (we recommend 3″), fertilize at proper times, etc. For more information, check out this source: http://turf.unl.edu/pdfctarticles/AschochytaMay2011.pdf