using a naturally occurring virus to manage insects in turfgrass: current situation
TRANSCRIPT
Virus for the control of turfgrass insects: Current situation
Callie Prater Freeman North Carolina State University
Pressure to reduce insecticide usage
Virus as a bioinsecticide
Baculovirus based insecticides are labeled for forestry and agriculture, but not turfgrass
Several commercial products are available such as GypCheck
USDA
Baculoviruses good for biocontrol….
Not harmful to vertebrates and plants
Narrow host range
Highly pathogenic
Have occlusion bodies
Can be used in conventional spray equipment
Prospects for Turfgrass
Reside in thatch layer
Photo: B. Bonning
Management Practices
Frequent irrigation
Mowing
GCM
GCM
Cultural practices
A serendipitous discovery!
Black cutworm Black cutworm Agrotis ipsilonAgrotis ipsilon (Hufnagel)(Hufnagel)
Cutworms in burrow
Black Necrotic Spots
Cutworm having a really bad day
Symptoms
Agrotis ipsilon multicapsid nucleopolyhedrosis virus (AgipMNPV)
B. Bonning
Does AgipMNPV have potential as Does AgipMNPV have potential as a bioinsecticide in turf?a bioinsecticide in turf?
Virus Field Test 2003
24 PVC rings in FW Creeping 24 PVC rings in FW Creeping BentgrassBentgrass
20 420 4thth instar instar larvae per ringlarvae per ring
TreatmentsTreatments1. 1. High rate: 5 x 10High rate: 5 x 1088 OB/m OB/m22
2. High rate post treatment irrigation2. High rate post treatment irrigation
3. Low rate: 5 x 103. Low rate: 5 x 1066 OB/m OB/m22
4. Control: (distilled water)4. Control: (distilled water)
Survivors recovered 3d post Survivors recovered 3d post treatmenttreatment
Verifica
tion
Verifica
tion
Control Low High High w/ Irr
Treatments
0
10
20
30
40
50
60
70
80
90
100
Mor
talit
y fro
m V
irus
(%)
AgipMNPV Field Trial 2003
*
F = 4.09; df= 4,18; P< 0.02
What is a lethal dose and What is a lethal dose and speed of kill?speed of kill?
Dose Survivorship Assay
Virus droplets of dose Virus droplets of dose placed on petri dishplaced on petri dish
6 doses: 0, 5, 25, 125, 6 doses: 0, 5, 25, 125, 625, 3125 OB/ 625, 3125 OB/ microlitermicroliter
24, 124, 1stst instar larvae per instar larvae per dosedose
Virus mine fieldVirus mine field
Larvae were placed on diet and observed for Larvae were placed on diet and observed for mortalitymortality
5 reps per dose5 reps per dose
0 5 25 125 625 3125
Dose (OBs per microliter)
0
10
20
30
40
50
60
70
80
90
100M
ort
alit
y fr
om
Vir
us
(%)
AgipMNPV Dose Assay
LD50: 70 OBs
Infected larva
Uninfected larva
Virus infection terminates development in early instars
3 4 5 6
Days after initial exposure
0
1
2
3
4
Mea
n (±
SE
) in
star
atta
ined
0
20
40
60
80
100
Infected Control Infected Control
Pe
rcen
tag
e su
rviving
AgipNPV Speed of Kill
Are Are olderolder instars equally instars equally susceptible to virus infection?susceptible to virus infection?
AgipMNPV Instar Susceptibility
• Dosed 1st, 3rd, and 5th instar BCWs
• 6 doses: 0, 5, 25, 125, 625, & 3125 OB
• 24 larvae per dose
• 5 reps per dose
0 OB 5 OB 25 OB 125 OB 625 OB 3125 OB
Dose (OBs per microliter)
0
10
20
30
40
50
60
70
80
90
100
Mort
alit
y fr
om
Vir
us
(%)
Instar Susceptibility
1st Instars
3rd Instars
5th Instars
Older larvae, usually the more damaging are not as Older larvae, usually the more damaging are not as susceptible to viral infectionsusceptible to viral infection!!
Will virus infection stop caterpillar feeding Will virus infection stop caterpillar feeding and prevent damage?and prevent damage?
Reduction in Feeding
4th instars droplet fed high rate & control
Given 6g diet every other day
Caterpillars and diet weighed at intervals
Reduction in Feeding ResultsReduction in Feeding Results
d1 d3 d5 d7
Time (d)
0
100
200
300
400
500
600
700
800
900
Weigh
t (mg)
Infected Uninfected
*
*
*
d1-3 d3-5 d5-7
Time (d)
0.00
0.60
1.20
1.80
2.40
3.00
Amou
nt ea
ten (g
)
Infected Uninfected
**
Amount Eaten Caterpillar Weight
* Two-sample T Test P<0.002
Optimizing Field Persistence
Baculoviruses susceptible to UV degradation
Irrigation could interfere with adherence
Formulate to optimize performance
Flourescent Brightener 28: Stilbene optical brightener
Cide-Kick II: Non-ionic spreader sticker
AgipMNPV Field Trial 2004AgipMNPV Field Persistence Trial AgipMNPV Field Persistence Trial 20042004
Houston Oaks GC Houston Oaks GC Paris, KYParis, KY
Treatments 1 Virus
2 Virus + Opt B
3 Virus + Cide-Kick II
4 Virus + Opt B + Cide-Kick II
5 Control (Distilled Water) * * Virus: 6 x 10Virus: 6 x 1099 OB/m OB/m22
Opt B: 1% Opt B: 1% ConcentrationConcentration
Cide-Kick II: Label Cide-Kick II: Label RateRate
Control High H/OB H/S H/OB/S
Treatment
0
10
20
30
40
50
60
70
80
90
100
Mor
talit
y fro
m V
irus
(%)
AgipMNPV Field Trial 2004
* * * *
Field Trial 2004
Open plots sprayed with virus 28, 21, 14, 7d, or 1 day
Third instars confined on 1, 7, 14, 21, 28-d field-weathered residues
Virus Residual Trial 2005
Untreated 1 7 14 21 280
10
20
30
40
50
60
70
80
90%
Mo
rta
lity
with
Ag
ipM
NP
V
Age of virus residues in turf (d)
C
B BB
B
A
AgipMNPV Residual Trial
AgipMNPV ConclusionsObserved a natural epizootic in 2003-2004
Crude virus formulations give adequate control 75-90% and 50% residual
Takes 1wk for larvae to die
Does not provide sufficient reduction in feeding
Inoculate for prolonged suppression
Hurdles to Commercialization Limited host range
Cost of production
Speed of kill
Activity on older larvae
Future Outlook
Recombinant viruses to increase virulence, host range, induce feeding cessation
Hormones, enzymes, toxins
Cell line production
Combination with insecticides
Endophytic grasses
AcknowledgementsTechnical SupportTechnical Support• Dr. Bryonny Bonning Lab Iowa State University
• Dr. Bruce Webb Lab University of Kentucky
• Dr. Dan Potter Lab University of Kentucky
Golf CoursesGolf Courses
Houston Oak GCHouston Oak GC
Cherry Blossom GCCherry Blossom GC
Griffin Gate GCGriffin Gate GC
Kearny Hills GCKearny Hills GC
Lexington Country ClubLexington Country Club
The Bull GCThe Bull GC
*This work was funded by grants from the USGA as well as the OJ This work was funded by grants from the USGA as well as the OJ Noer FoundationNoer Foundation