Husker Hort

A Nebraska View of Horticulture


1 Comment

Turf’s Yellow Streak

Yellow turf Photo from turf.unl.edu

Yellow turf
Photo from turf.unl.edu

This year has been a bit more ‘normal’ compared to last year.  The timely rains have kept many from having to run their irrigation systems and saved many lawns from going dormant.  The question that is stumping many people this season is “What’s with all the yellow turf?”

Yellow colored Kentucky bluegrass has been spotted all around the region.   While we don’t know the exact cause of the yellow lawns, there are several factors that are known.  The symptoms appear to only be affecting some cultivars of Kentucky bluegrass.  It has not been seen in tall fescue or perennial ryegrass.  The symptoms mainly appear only on the upper, young leaves.  This discriminating coloration means that it probably isn’t a deficiency of nitrogen.  Nutrients like nitrogen are mobile in the plant; if one leaf is affected, they will all be affected.  Other nutrients like iron might be to blame as it isn’t as mobile in the plant, which can lead to spotty symptoms.  On the turf that has been examined, there isn’t a notable lesion or spot on the leaf, which rules out many diseases and fungal infections.

The weather we have had this season might be playing a role in the yellow streak.  The symptoms are most often seen in lawns that are mostly irrigated.  They also happen when the soil temperatures are at their seasonal highs during wet summers.  There can be some similar yellowing symptoms in the spring, but they are attributed to denitrification, or loss of nitrogen, in the soil.

What can a person do?  You will be happy to know that this sickly color only affects the visual appeal of the Kentucky bluegrass.  It doesn’t seem to have any long term impacts on the overall health of the plant.  No need to apply a fungicide, insecticide, or fertilizers with less than 0.5 pounds of nitrogen per 1,000 sq ft.  Reducing irrigation for the short term should help with this coloration issue.  If you wanted to try to green up your turf, you could try a low rate application of iron.  This could give you back your green color, without the use of nitrogen fertilizer, which isn’t recommended in August.  Mowing could also remove a majority of the discolored younger foliage which is higher up in the canopy.

Some longer term solutions might need to be considered if this turns out to be an annual occurrence.  The main goal is going to include increasing drainage and reducing compaction.  Core aeration is one way to increase drainage to lawns that are compacted, on heavy clay, or have heavy traffic.  Another longer term option could include overseeding with a different cultivar of Kentucky bluegrass or possibly changing turfgrasses altogether.  To get the best of both worlds, you can try both aeration and overseeding.  Take advantage of the holes caused by core aeration and overseed at the same time.  The rule of thumb is that for each week grasses are seeded before Labor Day, development is speeded by two weeks.  The optimal window to seed cool-season turfgrasses is August 15 to September 15.  Thin stands of Kentucky bluegrass should be overseeded with improved cultivars at .75 to 1 pound of seed per 1,000 square foot.  If you are overseeding a tall fescue lawn, use a blend of improved turf-type tall fescue cultivars at a rate of 4 to 6 pounds of seed per 1,000 square feet.  Ensure the seed has good seed to soil contact and irrigate frequently to for the best germination.

If your lawn has a yellow streak, don’t worry.  A little time and a lot of patience will yield a greener appearing lawn.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.


Leave a comment

Attack of the Killer Wasps

 

Cicada Killer Wasp

Cicada Killer Wasp

It sounds like a scene right out of an old horror movie.  Insects are taking over the world.  Hornets are so large they are big enough to carry people away and insects are taking over homes and businesses.  I have to admit I might be exaggerating a bit, but there are some insects that can be frightening to look at or in such large numbers it might feel as if they are trying to take over.  In reality they are just more buzz than sting.

Cicada killer wasps have a frightening name, but that is about all.  These wasps are by far the largest wasp species in Nebraska, up to two inches long.  Their black bodies have a yellow stripe color pattern that is similar to other wasps.  Cicada killers, like their name implies, hunt cicadas, sometimes known as locusts.  They listen for the cicadas to sing then attack and sting to paralyze them.  They carry the paralyzed cicadas to their underground burrows where the female cicada killer will lay her eggs on it.  When the eggs hatch, the wasp larvae feed on the cicada.

The nests of these insects are not always placed in the best location.  The cicada killers’ nests are in the ground, usually near sidewalks, driveways, retaining walls or other areas of exposed soil.  They can be identified by the half-inch wide entrance hole with fresh soil surrounding it.  If you get close to their nest, they will alert you.  These wasps are very docile and often will just fly around your or act like they are coming after you.  When a person walks by a cicada killer, the wasp may become disoriented.  It will circle around the person as a way to reestablish its position, they not attacking.  While they are a wasp, they rarely sting unless severely provoked.

While control is rarely needed, there are some things you can do to ease your mind.  Cultural methods can be used to detour these wasps from making their nests in particular locations.  Since they make their burrows in out of the way places, take steps to encourage dense lawns or place extra mulch around the flowerbeds and around shrubs to cover bare soils.  Insecticidal control can be used if the nests do become a problem.  Use an insecticide labeled for use on wasps and be sure to read and follow the label instruction.  Take caution when applying insecticides to wasp burrows.  Apply products in the cooler parts of the day, either early morning or later in the evening, when the insects will be in their burrow and not as aggressive.

They might not be taking over the world, but there is an insect that is invading homes right now.  The strawberry root weevil is a common home-invading insect that is black or dark brown and about 1/4 inch long.  They are often confused with a tick, but they have 6 legs instead of the 8 that ticks have.  The larvae feed on the roots of strawberries, evergreens, brambles, and grapes.  The adults, which are all female, emerge in summer and feed on the edges of foliage, giving a notched appearance.

The beginning in late July to early August the adult strawberry root weevils begin to migrate into homes.  Once inside the home, they don’t cause any damage and are just more of an annoyance than anything else.  They are attracted to moisture and will often be found in sinks, bathtubs, or other similar places.  Control inside the home is rarely required, in a few weeks the migration will be completed.  Once found inside they can be vacuumed or swept up.  While there are pesticides labeled for inside home use, they are rarely recommended.  To prevent entry into homes, now would be the time to apply a perimeter spray that contains bifenthrin, cypermethrin or cyfluthrin.

Insects might not be taking over the world, but there are times when larger than average wasps and armies of strawberry root weevils invading homes might make it feel as if they are.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.


2 Comments

Grubs

 

White Grubs

White Grubs

June 21st 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.

White grubs are the larvae of a group of beetles called scarab beetles.  There are many scarab beetles in Nebraska, but only a few can cause significant damage to turf.  The more common ones include the masked chafer, or annual grubs, and the May/June beetles, or three-year grubs.  White grubs look very similar.  They have C-shaped bodies that are cream or white colored, have reddish-brown heads, and three pairs of short legs right behind the head.

There are minor differences between the species, but they all have the same type of feeding patterns.  The grubs feed below the soil surface on the roots of all common turfgrass species.  They are capable of destroying the entire root system of the plant if infestations are heavy enough.  The first signs of grub damage include areas of pale, discolored, dying grass displaying signs of moisture stress.  The adult beetles of these grubs rarely cause much damage and are more of a nuisance than anything.

Damaged areas are small at first, but will grow rapidly as the grubs grow and enlarge their feeding area.  The affected areas may feel spongy and can be easily lifted from the soil surface or rolled like a carpet.  Another indicator that your lawn may have grubs is small areas that are dug up by animals like raccoons, skunks, or moles foraging for the insects.

A few grubs in your lawn doesn’t necessarily mean that an insecticidal control is needed.  There are threshold levels that warrant insecticidal control.  For masked chafers 8-10 grubs per square foot and 3-5 per square foot May/June beetles are the threshold levels.  If you have more insects than that, a curative treatment will be needed, usually around the first week of August.  If you have had a history of grubs in your lawn, a preventative insecticide application the third week of June through early-July will have the insecticide in place when the eggs begin to hatch.

Products for grub control have changed over time.  Before 1999 grub insecticides were used as curative treatments.  They were fast acting, had a short residual activity and needed to be applied within a narrow treatment window.  New types of insecticides are now available that offer the opportunity for preventative treatments.  These products are slower acting, but they have a much longer period of residual activity and are available for a much wider treatment window.

There are a wide range of products that can be used to treat grubs.  Chlorpyrifos (Dusban), carbaryl (Sevin), isazophos (Triumph), Chlorantraniliprole (Acelyprin), Imidacloprid (Merit), and Halofenozide (Mach 2) are just some examples of the products that will work well to control grubs.  Trichlorfon (Dylox) can be applied for curative control if white grubs exceed threshold levels later in the season.  Be sure to read and follow the label instructions.

Keep in mind that no registered insecticide is 100% effective.  On average they usually kill 75 to 90% of the grubs present in any given area. Re-applications may be necessary when grub populations get very high.  Scouting early and catching the problem before the numbers get too high will help allow you to have a worry free summer.

Can’t get enough horticulture information?  Listen on Fridays at 8:15 a.m. on KRGI 1430 am to hear ‘Everything Outdoors.’  It is a live call-in radio show in which Hall County Extension Educator Elizabeth Killinger gets you the answers to your horticulture questions.

 

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.


Leave a comment

Lawn Weeds

Henbit- a winter annual

Henbit- a winter annual

A weed is a plant out of place.  Seems like such a ‘nice’ definition for these little plants.  Weeds can be issues in many areas, but it always seems that they are the most plentiful in the lawn.  The key to knowing when to pull and when to spray depends on the weed and time of year.  It all comes down to proper identification of the weed and its life cycle.

Winter annual weeds bloom in the spring, produce seed, and die all before the temperatures get hot. One of the more common winter annual weeds is henbit, which is the ‘pretty’ purple flower in bloom in the road ditches.  Henbit has scalloped leaves, a square stem, and little purple flowers at the tip of the stem.  These weed seeds germinated last year in September or October.  The little plants sat dormant throughout the winter just waiting for the right time to jump into flower and seed production.  Right now, a post emergent herbicide, products like 2,4-D, can be applied, but they might not do that much good.  Spraying might make you feel better, but it can cause the plant to produce and drop its already mature seeds.  If the area isn’t too large, you can hand-pull these weeds.  Also, look at the density of your lawn in the areas where the weeds are located.  Is it thin?  You might need to figure out why the turfgrass isn’t competing with the winter annuals and a cultural practice change might be needed to promote grass growth and density in that area.  If herbicide control is needed, preemergence herbicides should be applied in early September to control winter annual weeds.

Summer annual weeds germinate in the spring, grow throughout the summer months, and produce seeds and die before winter.  One of the most common summer annual weeds is crabgrass.  Crabgrass is an annual grass that often fills into areas where the turfgrass is thin.  There are products that you can apply now to help keep the crabgrass problem at bay.  Crabgrass preventers, or preemergence herbicides, will help you in this fight against crabgrass.  These products will only work to keep seeds from germinating, or beginning to grow, not for plants that are already growing.  Crabgrass needs a minimum soil temperature of 50 to 55 degrees to begin germination.  Preemergence herbicide applied just prior to germination provide the longest period of control.  In most years, the optimum time to apply preemergence herbicides for crabgrass are  between the end of April to early May.  A second application might be needed in mid to late June to give complete weed control.  Remember that these products need to be watered into the soil profile for best control.

Perennial weeds come back year after year.  The common offenders include white clover and ground ivy.  Ground Ivy looks very similar to henbit, but the control methods are very different.  Ground ivy also has scalloped leaves, a square stem, and purplish flowers, but the flowers are in the leaf axil, between the leaf and the stem.  Positive identification is key to the control method.  Since ground ivy is a perennial and comes back year after year, a post emergence herbicide will be needed.  If the product is applied now, the foliage might be burned back, but the plant will regrow.  The best time to apply post emergence herbicides for perennial lawn weeds is in October with a combination herbicide, like Trimec that contains 2,4-D, MCPP, and dicamba.  These products will also work well to control other weeds like clover or dandelions in the lawn.

With proper identification and timing, these out-of-place plants can be controlled.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.