Husker Hort

A Nebraska View of Horticulture

Monthly Archives: August 2013


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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.


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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.


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Gone Batty

New UNL Extension Publication about bats

New UNL Extension Publication about bats

What is small, flies at night, eats 25-125 percent of its body weight in insects each night and gives most people the heebie-jeebies?  Bats are more than just scary little critters that want to suck your blood; they are helpful creatures that are worth their weight in insect control

These winged mammals are more misunderstood than scary.  There are about 13 species of bats living in our great state, most are rarely found in or around structures.  Bats are insectivores and only need small needle like teeth to crush the insects they catch in flight.  These nocturnal creatures have good vision, but rely on echolocation, or sonar, to hunt in the dark for their prey.  Man, can they eat!  One little brown bat can eat 600 to 1200 mosquito-sized insects every hour.

Only a few species of bats are common in or around structures.  The big brown bat is the most common across the state.  It has dark brown fur on its back, pale brown fur on its underbelly, and it has exposed black skin on its nose, ears, and wings.  It is about 4-5 inches long from nose to tail and weighs a whopping 1/2 to 1/3 of an ounce.  When its wings are fully extended, they can reach lengths of 12 to 16 inches, making it look much larger in flight.

Bats will leave their own ‘calling cards’ to let you know they are around.  The most common sign that a bat is in the area are their droppings, guano.  Bat droppings will look like it contains specks, which are the exoskeletons and wings of insects.  Droppings are often found on attic or porch floors and under eves and shutters.  A 3/8” hole is all the space a bat needs to get into a structure.  The bat will use these openings every evening to go in and out.  Rub marks or smudges, caused by the oil and dirt in the bats fur, are often found near these opening and can alert you of a bat entrance.

July is the month many homeowners encounter bats.  At this time of the year, young bats move around the structure, but they are not strong enough to forage for insects.  They often find their way into the living quarters of the home or just outside their entrance points into a structure.  Young bats are also more likely to fly inside an open window or door.

There are some steps you can take if a single bat has entered the home.  First, open all exterior door and windows and shut the doors to adjacent rooms.  Leave the lights on and stand motionless next to a wall or in a hallway leading to the room.  Wait patiently for the bat to swoop around the room, find an escape route and fly out on its own.  Try to observe the bat leaving the home so you can be sure it made it out safely.

If the bat is at rest on the wall there are some other steps you can take to remove it.  While wearing a thick pair of leather gloves place a large mouthed container over the bat and slide a stiff piece of cardboard between the container and the wall.  The cardboard will help to secure the bat inside the container, allowing you to either get it tested for rabies or to set it free.  If you set it free, place it up at least 4 feet off the ground so it can gain enough lift to fly away.

Bats are associated with rabies, a disease that can be transmitted to humans. While significant, infection can be easily avoided and should not be used as an excuse to kill bats. Only a very small percentage of bats are associated with rabies. Due to their small teeth, you might not realize you have been bitten.  Nebraska has the recommended protocol for handling potential bat-human exposures. Assume a person was bitten if:

  • He/she awakens to find a bat in the room.
  • A bat is found in the room with someone unable to communicate well (i.e. children, intoxicated or otherwise mentally impaired).
  • The bat made contact with a person.

In these situations, do not release the bat.  Take care not to damage the bat’s head.  Contact local health officials to determine where the bat needs to be sent for rabies testing.  If the bat is not found within a couple of hours, talk to your health professional about needed treatment.

The next time you see a bat, think of all these mosquito-munching, nocturnal creatures do to help keep pesky mosquito populations in check.

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.


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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.