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2017 Rice Insect Control Update
Michael Stout, LAES & LCES (interim)Marty Frey, RA, Rice Research Station
Lina BernaolaEmily Kraus
Maisarah SaadJames Villegas
Insect pests in rice: a time of transition?
Established pests
Over the past decade: Invasive pests
Insect pest management in 2017
• Prepare for the established pests
-- Have a plan for managing rice water weevils
-- Scout for rice stink bugs
• Be on the lookout for invasive pests
-- Look for symptoms of Mexican rice borer, South American rice miner, rice delphacid
--Pheromone traps for Mexican rice borer
Rice stink bugOrganophosphates
“old” threshold
OrganophosphatesPyrethroids
“old” threshold
Weeds
Scouting and thresholds• Begin scouting when rice is 50 to 75% heading
• 10 sweeps at 10 different areas
• Avoid hot hours
• First two weeks of heading: 3 bugs per 10 sweeps
• After first two weeks: 10 bugs per 10 sweeps
• Count nymphs as well as adults!
Re-evaluation of stink bug thresholds
• Small field plots of ‘Cheniere’
• Plots assigned to three treatments: no insecticide, high rate of Karate applied every 2-3 days; low rate of Karate applied every ~ 6 days
• At grain maturity, collect 15 panicles per plot
• Hand thresh, separate filled from empty grains
• De-hull filled grains, process to measure peck and broken grains
y = 0.2469x + 1.8628R² = 0.4483
0
2
4
6
8
10
12
0 5 10 15 20 25
Stink bugs per 10 sweeps
% p
eck
Stink bug density vs. % peck, 2015
Each bug: 0.25% peck
y = 0.2704x + 0.3067R² = 0.807
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 5 10 15
% p
eck
Stink bugs per 10 sweeps
Stink bug thresholds: bug density vs. % peck, 2016
Stink bug thresholds: bug density vs. empty grains
y = 0.5656x + 11.762R² = 0.6239
0
5
10
15
20
25
0 5 10 15
% E
mp
ty g
rain
s
Stink bugs per 10 sweeps
These density – damage relationships will allow us to calculate new
economic injury levels/thresholds
Rice Water Weevil Biology
14
Overwintering
Adult feeding
Mating & egg-laying
Root pruning
Flooding triggers
egg laying
Foliar insecticides Seed treatments
Pyrethroids Belay Dermacor CruiserMaxxNipsitInside
What insecticide should I use?
Justification:
If you have a history of rice water weevil or stem borer infestations, probably best to use
seed treatments
Cruisery = -34.03x + 2669.9
R² = 0.5132
Dermacory = -34.12x + 2655.3
R² = 0.9292200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
0 2 4 6 8 10 12 14
Relationship between rice water weevil larval
density and rice yield
• Each weevil larva correlated with ~1% loss in yield
• Three larvae per core sample = ~$20 per acre
Plo
t yie
ld
Weevil density
Cruisery = -34.03x + 2669.9
R² = 0.5132
Dermacory = -34.12x + 2655.3
R² = 0.9292200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
0 2 4 6 8 10 12 14
Relationship between rice water weevil larval
density and rice yield
• Each weevil larva correlated with ~1% loss in yield
• Three larvae per core sample = ~$20 per acre
Plo
t yie
ld
Weevil density
Threshold = 3 larvae per core sample = density of larvae at which treatment is
justified
0
25
50
75
100
2008 2009 2010 2011
Pe
rce
nt
exce
ed
ing
thre
sho
ld
Year
Proportion of untreated rice with weevil infestations that exceeded threshold, 2008-2011
Threshold = 3 larvae per core, ~$15-$20 loss per acreAverage weevil density = ~11 larvae per core sample
0
25
50
75
100
2008 2009 2010 2011
Pe
rce
nt
exce
ed
ing
thre
sho
ld
Year
Proportion of untreated rice with weevil infestations that exceeded threshold, 2008-2011
Threshold = 3 larvae per core, ~$15-$20 loss per acreAverage weevil density = ~11 larvae per core sample
The majority of rice fields in SW Louisiana will require treatment!
Spectra of activityCruiser/Nipsit Dermacor X-100
Pyrethroids very broad spectrum, Belay not as broad-spectrum
For early planted fields without a history of weevils or stem borers, may consider foliars (pyrethroids and Belay)
The question with foliars – when do I treat?
If you have a history of rice water weevil or stem borer infestations, probably best to use
seed treatments
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0 2 4 6 8 10 12 14 16
We
evil
larv
ae p
er
core
sam
ple
Feeding Scars per plant
Can we predict larval densities by counting adult weevils or feeding scars?
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0 2 4 6 8 10 12 14 16
We
evil
larv
ae p
er
core
sam
ple
Feeding Scars per plant
Can we predict larval densities by counting adult weevils or feeding scars?
Timing of foliar applications: if weevils are present (adults, scarring) and standing
water is present
But…over the past decade: Invasive pests
South American Rice Miner
• Will the SARM be a problem again in 2017?
--Cannot predict, previous widespread infestation was 2005
• Will seed treatments control SARM?
--Has not yet been tested, because insect does not show up consistently
• What else can be done about SARM?
--early planting, adequate seeding rates
Mexican rice borer now in all rice-producing parishes in Louisiana
Source: Blake Wilson
MRB Range Expansion
2008
2011
2013
2014
2015
2016
Not yet
detected
Calcasieu
Cameron
BeauregardAllen
Jeff.
Davis
Evangeline
Acadia
Vermilion
Laf.
St.
Landry
St.
Martin
Iberia
St.
Martin
St.
Mary
Iberville
WBR
EBR
Pointe
Coupee
Assump.
Stem borer management program
• Use Dermacor X-100 to control weevils and suppress stem borers
• Plant early to avoid severe infestations of borers
• Plow fields in fall/winter to eliminate overwintering habitat
• Use less susceptible varieties
• Scout and use pheromone traps; foliar insecticides if needed
• Silicon soil amendment may reduce borer densities
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Ave
. no
. of
wh
ite
he
ad
Variety
2015
2016
Stem borer infestation (mean whitehead/variety) in Crowley, 2015-2016
Rice delphacid (planthopper) in Texas (2015)
Photo by Pat Porter Photo by Pat Porter
If you see “symptoms” of these invasive pests, contact your county
agent – we need to know how severe and prevalent these problems are
2016 Dermacor trial
• Wanted to test the effectiveness of Dermacorat several rates against rice water weevils and stem borers
• Small rice plots at H. Rouse Caffey Rice Research Station
• Rice water weevils-core samples
• Rice stem borers-infest cut stems in lab at two growth stages
• Lab analysis of chlorantraniliprole levels
0
5
10
15
20
25
30
0 0.25 0.5 0.75 1 2
Wee
vil l
arva
e p
er c
ore
Dermacor rates (relative to label rate)
P < 0.0001
A
B
B B
B B
Dermacor is very effective against rice water weevils…
0
0.5
1
0 0.25 0.5 0.75 1 2
Mo
rtal
ity
Rat
e
Dermacor Rate
SCB Mortality (Vegetative)
0
5
10
15
20
25
30
35
40
45
0 0.25 0.5 0.75 1 2
Mo
rtal
ioty
rate
Dermacor Rates
SCB Mortality: Reproductive
Dermacor also provides protection against stem borers
0
20
40
60
80
100
120
140
160
180
200
0 0.25 0.5 0.75 1 2
Ch
lora
ntr
anili
pro
le (
pp
b)
Dermacor Rates
Chlorantraniliprole Analysis
Reproductive
Vegetative
www.lsuagcenter.com/riceinsects
http://ricescout.lsuagcenter.com/
“Rice Insects Information” website & Rice Scout App
• Information on biology and management
• Pictures
• Links to videos
Mike Stoutmstout@agcenter.lsu.edu
Cell: (225) 892-2972Office: (225) 578-1837
Questions or feedback?
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