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A Review of Turfgrass Insects and
Their Management (206)
Whitney Cranshaw
Colorado State University
Turfgrass Insects & Mites
• Plant feeders–Root/subterranean feeders
–Crown feeders
–Surface/foliage feeders
• Predators/Parasitoids
• Macrodecomposers
Insects that Feed in the Root System of Turfgrass
White grubs Billbug larvae
Cranberry girdler
Primary root feeding group of turfgrass – white grubs
White Grubs(Coleoptera: Scarabeaidae)
Larvae of scarab beetles – chafers,
May/June beetles, dung beetles, etc.
Turfgrass Damaging White
Grubs in the United States
• May/June beetles (Phyllophaga spp.)
• Masked chafers (Cyclocephala spp.)
• Japanese beetle
• European chafer
• Oriental beetle
• Black turfgrass ataenius
• Green June beetle
Eggs are laid underground, singly or in small groups
White grub identification: Distinct head, distinct thoracic
legs, C-shape when at rest
Turfgrass damaging white grubs feed on the roots
of their host plants
Scarab
Beetle
pests of
Colorado
Primary turfgrass grub in Colorado
Western Masked
Chafer
Cyclocephala hirta
Late stage larva
(white grub)
Pupa
Adults enter the soil and lay
eggs in small groups
Soil type and soil moisture are
very important in determining
where eggs will be laid
The white grubs feed
on soil organic matter –
and roots of grasses
Peak larval
damage can
be expected
to occur in
August, early
September
Skunk digging
damage associated
with white grub
infestations
Identifying White Grubs
Check the Rastral
Pattern!
University of Nebraska
Common white grub of in parts of eastern Colorado
May/June Beetles
Phyllophaga species
Life cycles of
May/June beetles
typically require three
years to complete in
Colorado
Peak damage in year
after peak adult flight
Mixed sized
larvae present,
due to extended
life cycle
Key rastral
pattern feature
Largest grub in
soil – Tenlined
June beetle (and
relatives)
Larvae may feed on roots
of trees and shrubs
Japanese Beetle
Popillia japonica
Japanese beetle
adults chew on
leaves and flowers
of many plants
Japanese beetle
larvae (grubs) –
Among most
damaging turfgrass
insects in the US
Japanese beetle traps
are excellent for
detecting presence of
the insect in an area
Japanese beetle is present in two main areas
Generalized Life History Sequence of
Japanese Beetle
Adults burrow into the ground to lay eggs.
Eggs are only laid in soil that is suitably
moist.
Early stages of Japanese beetle grubs are
highly sensitive to soil drying
As grubs get older,
more root pruning
occurs
Japanese beetle
European chafer
May/June beetle
University of Nebraska
Control of White Grubs in
Lawns
•Cultural practices
• Insecticides
•Biological controls
As grubs get older,
more root pruning
occurs
Grasses with
larger root mass
are better able to
tolerate effects
of root pruning
insects
Mowing height greatly
affects root mass of
turfgrasses!
White Grub Larval Treatments
• Insecticides
– Imidacloprid (Merit, Zenith, Criterion, etc.)
– Clothianidin (Arena)
– Chlorantraniliprole (Acelepryn, Scott’s
Grub-Ex)
– Trichlorfon (Dylox, Proxol)
• Biological Controls
– Heterorhabditis spp. parasitic nematodes
– Bacillus thuringiensis var. galleriae
(grubGONE!)
Some systemic
insecticides
(imidacloprid,
chlothianidin) are
used to control insect
pests of turfgrass
Primary Neonicotinoid Insecticides
Used on Turfgrass
• Imidacloprid (Merit, Criterion, Zenith, many generics)
• Clothianidin (Arena)
• Thiamethoxam (Flagship, Meridian)
Combination products
Aloft – chlothianidin + bifenthrin
Allectus – imidacloprid + bifenthrin
Neonicotinoids and Pollinators –
Should we be concerned about
their use on turfgrass?
Lawns can be an
important resource
site from many
pollinating insects!
>50 total species collected
A key risk to
pollinators when
using
insecticides on
turfgrass
Application to
flowering
weeds
Mowing before application >greatly<
decreases hazard to pollinators!
White Grub Larval Treatments
• Imidacloprid (Merit, Zenith, Criterion, etc.)
• Clothianidin (Arena)
• Chlorantraniliprole (Acelepryn, Scott’s
Grub-Ex)• Trichlorfon (Dylox, Proxol)
• Heterorhabditis spp. parasitic nematodes
• Bacillus thuringiensis var. galleriae (grubGONE!)
Chloranthraniliprole(Acelepryn)
• New class of insecticides –
anthrinilic diamides
–Based on natural product (Ryania)
• Activity against most chewing
insects
–White grubs, billbugs (Coleoptera)
–Sod webworms, cutworms (Lepidoptera)
Acelepryn• Very low toxicity to vertebrates
–LD50 greater than 5000 mg/kg• Class 4 – No Caution label
– Protective equipment
• Long sleeved shirt, long pants
• Shoes with socks
• Very low hazard to non-target
organisms (bees, birds)
White Grub Larval Treatments• Imidacloprid (Merit, Zenith, Criterion, etc.)
• Clothianidin (Arena)
• Chlorantraniliprole (Acelepryn, Scott’s Grub-Ex)
• Trichlorfon (Dylox, Proxol)
• Heterorhabditis spp. parasitic
nematodes• Bacillus thuringiensis var. galleriae (grubGONE!)
Photograph courtesy of Peggy Greb
Insect Parasitic Nematodes (“Beneficial
Nematodes”, “Predator Nematodes”)
Nematodes enter insects
through natural openings
Heterorhabditis spp.
nematodes can
penetrate directly
through the body wall
Insect Parasitic
Nematodes Can Control
Many Turf Insects
White grubs
Billbugs
Cutworms and sod webworms
Mole crickets
Grubs turn a reddish color when killed by
Heterorhabditis nematodes
White Grub Larval Treatments• Imidacloprid (Merit, Zenith, Criterion, etc.)
• Clothianidin (Arena)
• Chlorantraniliprole (Acelepryn, Scott’s Grub-Ex)
• Trichlorfon (Dylox, Proxol)
• Heterorhabditis spp. parasitic nematodes
• Bacillus thuringiensis var. galleriae
(grubGONE!)
grubGONE!
Bacillus
thuringiensis var.
galleriae
New biological
control for Japanese
beetle - and other
grubs?
Milky Spore for Japanese Beetle?
May help produce some reduction in numbers of
larvae surviving to adulthood. However,
infections typically only affect a some percentage
of population.
Should we now consider trying to introduce
natural enemies of Japanese beetle into Colorado?
Yes!
Natural Enemies of Japanese Beetle Exist
Elsewhere in the US
• Paenibacillus popilliae (Milky spore)
–Bacterium
• Istocheta aldrichi*–Tachinid fly
• Tiphia species* –Parasitic wasps
• Ovavesicula popilliae*–Microsporidium (fungus)
* Species involved in Colorado Japanese Beetle Biological Control Program
Natural Enemies of Japanese Beetle for Potential
Introduction into Colorado?
Ovavesicula popilliae – a microsporidian disease of Japanese
beetle larvae
Main observed effects from infection – reduced
fecundity, reduced winter survival
Ovavesicula infection of
Malphighian tubules of
Japanese beetle larva
The Malpighian tubules of insects filter wastes from the blood, functioning somewhat like what the kidney does in humans
Heavy O. popilliae infection of Malpighian tubules of Japanese beetle
Normal
Infected
Infected malpighian tubule packed with O. popilliaesporophorousvesicles
Year 6: Impact of Ovavesicula Infection on
Winter Grub Mortality (Oct.'05 to April '06)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0
Ovavesicula Infection (%)
Gru
b M
ort
alit
y (
%)
Ovavesicula popilliae: % infection of adult Japanese beetles at ten golf courses in Michigan from 2000 to 2016.
Japanese beetle trap catches at ten golf
courses in southern Michigan from 1999 to
2016.
Data are mean beetles/trap/week.
Source: David Smitley, Michigan State University
Japanese beetles collected from Michigan that were infected with Ovavesicula
popilliae were shipped to us in late July 2015. The beetles were frozen, so no
live beetles were introduced, but spores of the pathogen are still viable.
Experimental releases of Ovavesicula
popilliae were first made in 2015
The infected (but dead and
frozen) beetles were applied
in several waysInserted whole into soil
Broadcast whole on surface
Blended and applied as slurry
2015 releases of Ovavesicula
popilliae – It took!
Positive infections confirmed
in 2017 from both Flatirons
Golf Course (Boulder) and
Pueblo Zoo release sites!!!!
Japanese beetle biological control sites in the Denver Metro area - 2018
Ovavesiculapopilliae was released at six sites during August
History of JB Biological Control Releases in Pueblo
Ovavesicula released in 2015Infection confirmed in 2017Istocheta released 2018
Ovavesicula released in 2015No infection confirmed to date
Ovavesicula released in 2018
Ovavesicula release 2015Infection confirmed 2017
History of JB biological control releases in Boulder
Istocheta aldrichi– the “winsome fly”
Diptera: Tachinidae
The adult flies glue their eggs onto adult Japanese beetles
Hatched egg
Pupa of the fly larva that
developed within and
killed the Japanese beetle
Japanese beetle biological control sites in the Denver Metro area - 2018
Istochetaaldrichi was released at two sites during July
History of JB Biological Control Releases in Pueblo
Istocheta released July 2018
Tiphia vernalisspring tiphia
Hymenoptera: Tiphiidae
The adult wasps dig into the soil and lay their eggs on late stage Japanese beetle grubs
Photographs courtesy of David Shetlar, the Ohio State University
Japanese beetle biological control sites in the Denver Metro area - 2018
Tiphia vernaliswas released at the Sterne Park site (Littleton) in May
At almost all JB biocontrol release sites traps were maintained to try and establish a 2018 baseline population estimate, against which future comparisons can be made
Proposed Japanese Beetle Biological
Control Plan
• Attempt to establish all 3 JB biocontrols at
strategically located sites where the insect is in
high population (2018-2021?)
–Denver/Arapahoe County Metro Area – 8-12 sites
–Boulder (3-4 sites)
–Pueblo (3-4 sites)
–Other (TBD)• Monitor establishment and spread of the released biological control organisms
(2018-2030?)
• Periodically census JB by trapping to detect changes in populations (2018-
2030?
Proposed Japanese Beetle Biological
Control Plan• Attempt to establish all 3 JB biocontrols at strategically located sites where the
insect is in high population (2018-2021?)
– Denver/Arapahoe County Metro Area – 8-12 sites
– Boulder (3-4 sites)
– Pueblo (3-4 sites)
– Other (TBD)
• Monitor establishment and spread of the
released biological control organisms (2018-
2030?)• Periodically census JB by trapping to detect changes in populations (2018-
2030?
Proposed Japanese Beetle Biological
Control Plan• Attempt to establish all 3 JB biocontrols at strategically located sites where the
insect is in high population (2018-2021?)
– Denver/Arapahoe County Metro Area – 8-12 sites
– Boulder (3-4 sites)
– Pueblo (3-4 sites)
– Other (TBD)
• Monitor establishment and spread of the released biological control organisms
(2018-2030?)
• Periodically census JB by trapping to detect
changes in populations (2018-2030?
BillbugsSphenophorous spp.
The grass feeding
weevils
Rocky Mountain
billbug
Bluegrass
billbug
Billbug Life Stages
Billbug Egg Inserted into Grass Stem
Young billbug larvae
develop within plant
stems
Billbug damaged turfgrass breaks
easily at crown (“tug test”)
Diagnostic: Sawdust frass characteristic of billbug larval
feeding
Older billbug larvae are root feeders
Billbug larva –
no legs
White grub –
Legs present
Diagnosis of Billbug Damage
• Turfgrass has appearance of drought
stress
– Turf may die in patches
• When pulled (‘tug test’) grass breaks at
crown
– Plant base should show chewing injury
• Granular sawdust-like frass present
around feeding site
Rocky Mountain billbugBluegrass billbug
Billbug Controls
• Use of resistant cultivars
• Adult control
– Targeted at periods when adults are present on surface
• Larval control
– Must concentrate in crown and upper root zone
Caterpillar Pests of
Turfgrass
Sod Webworms and Cutworms
Vagabond CrambusAgriphila vulgivagellus
A sod webworm that was present
in extraordinary numbers during
August/September 2016
Sod Webworms –Caterpillars that feed
on grasses, usually
within a silken
structure
Typical sod
webworm larvae
Most sod webworm larvae live within a
burrow (often lined with silk) in the thatch
The larvae feed on
grass blades, which
they clip. Feeding
occurs at night.
Life Stages of a Sod Webworm
Egg
Larval stages
Pupa
Adult
Image courtesy of David Shetlar, Ohio State University
Sod Webworm Adults
Key Aspects of Sod Webworm Biology
• Most species overwinter as larvae
• Most species have two generations
– Peak lawn damage done by overwintered
larvae
– Second generation feeds in July, August
• Adults rest on grass or adjacent
vegetation during the day
– Adults fly at dusk, night
– Eggs are dropped onto turfgrass during
flight
Typical Peak Damage:
Early spring
(overwintered larvae)
Some species -
July/August (2nd
generation)
Blackbirds Feeding on Sod Webworms and Cutworms
Holes made by birds seeking sod
webworm (or cutworm) caterpillars
Diagnostic: Fecal pellets produced by sod webworm
caterpillar
Piles of fecal pellets
collect where sod
webworms (and
cutworms) rest
Diagnosis of Sod Webworm Damage
• Turfgrass slow to green in spring
• Blackbirds feed on the lawn
• Close inspection may show piles
of pelleted frass, composed of
grass particles
Vagabond CrambusAgriphila vulgivagellus
A sod webworm that was present
in extraordinary numbers during
August/September 2016
A subterranean sod webworm –
the cranberry girdler
Larvae develop below
ground, feeding on roots
Adults lay eggs at
dusk, during mid-
late summer
Appearance of turfgrass in
cranberry girdler infested site
Peal away the grass to
exam the root area
Cranberry girdler has a
light brown head and a
pale-colored bodied
Cranberry
Girdler
“The Subterranean
Sod Webworm”
Feeds in crown area
and upper root zone
Peak injury September
and early October
Control of Cranberry Girdler?
• Imidacloprid?
• Surface sprays of pyrethroids?
• Trichlorfon (Dylox/Proxol)
• Insect Parasitic Nematodes
Control of Cranberry Girdler?
• Imidacloprid?
– NO. Imdidacloprid does not work well on
caterpillars (larvae of moths)
• Surface sprays of pyrethroids?
– NO. Pyrethroids do not penetrate into the root
zone.
Control of Cranberry Girdler?
• Trichlorfon (Dylox/Proxol)
– Possible. Fast acting, water soluble, very short
persistence
• Insect Parasitic Nematodes
– Possible. Any species works. Soil
temperatures must be above 52-55F. Must be
watered in well.
Insects that Feed in the Root System of Turfgrass
White grubs Billbug larvae
Cranberry girdler
Another new insect to watch out
for:
Noctua pronuba
Large yellow
underwing
Winter cutworm
The forewings (top)
wings can vary from
light to dark brown.
The hindwings are
bright yellow.
An odd behavior
This caterpillar may
be seen actively
moving about on
warm days
throughout winter!
Another new insect to watch out for:
Noctua pronuba
Large yellow
underwing
Winter cutworm
This presentation will be posted at the Insect
Information Web Site
• Housed at Department of
Bioagricultural Sciences and Pest
Management
– Search BSPM CSU
• Within Extension and Outreach
–Insect Information• Extension presentations for 2018 posted at bottom of page
Click here for
over 200 Fact
Sheets
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Beetle
CSU Insect Information
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This presentation will be posted at the Insect
Information web site
• Housed at Department of Bioagricultural Sciences
and Pest Management
– Search “BSPM CSU”
• Within “Extension and Outreach”
• “Insect Information”
– Extension presentations for 2018 posted at bottom of page
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