Emerging pests of rice: Stem borers and apple snails Blake Wilson Field Crops Entomologist

LATMC Rice Breakout Session February 14, 2020

Rice stem borer complex

Sugarcane borer Mexican rice borer Rice stalk borer saccharalis Eoreuma loftini Chilo plejadellus

Rice stem borer complex Lep.: , Snout

Sugarcane borer Mexican rice borer Rice stalk borer Diatraea saccharalis Eoreuma loftini Chilo plejadellus

1 Non-crop grass hosts

Johnson grass Brome grass

Vasey grass Annual rye grass

Host preferences: Choice tests

1.0

Rice 0.8

0.6

Johnsongrass 0.4 Vasey grass

Sugarcane 0.2 Rye grass Brome MRB ovipositionpreference

0.0

Old Old Old Old

Young Young Young Young Young Young

Intermediate Intermediate Intermediate Intermediate Intermediate Intermediate

Beuzelin et al. (2011) ; Reay-Jones et al. (2007)

Host suitability

0.100

0.075

0.050

0.025 MRB LarvalMRB Survival

0.000

2 Rice stem borer complex

Stem Borer Management

• Begin scouting in late tillering • Pyrethroids can be applied with fungicides for sheath blight • Once white-heads are present, losses have already occurred Stem borer injury to leaf sheath

Stem borer injury in rice

White heads

3 MRB Range Expansion

Rapides Avoyelles Vernon

2008

Evangeline 2011 Beauregard Allen St. Pointe Landry Coupee EBR 2013 WBR

St. 2014 Jeff. Acadia Martin Calcasieu Iberville Davis Laf. Ascen. 2015

St. 2016 Iberia James Assump. Cameron St. Vermilion Martin 2017 St. Mary 2018

Terrebonne Not yet detected

High whitehead density

4 Average whitehead density at Crowley Station 2015-2019

6

5

4

3

2 Whiteheads/m2 1

0 2015 2016 2017 2018 2019

Cultural Control: Stubble Management

• Reduce overwintering habitat

Cultural Control: Stubble Management

18 20 cm 15

12 40 cm 9

6

No. stem borersNo. m2 / 3

0 E. loftini D. saccharalis

Data from Beuzelin et al. 2012

5 Cultural Control: Early planting

9 A A 8 A 2018 A 7 6 2019 5 4 B 3 B BC B B Whiteheads/m2 2 C B C 1 0

2018: F = 35.8, df = 3, 105; P < 0.001 2019: F = 33.8, df = 5, 105; P < 0.001

Varietal resistance

12 A 10 2018 A 8 2019 A

6 B 4 BC B BC BC Whiteheads/m2 B B 2 C B

0

2018: F = 35.8, df = 3, 105; P < 0.001 2019: F = 35.8, df = 5, 105; P < 0.001

Insecticidal Seed Treatments

6 Insecticidal seed treatments (ISTs)

–Dermacor X-100 (chlorantraniliprole) –Controls: RWW, armyworm, borers –Fortenza (cyantraniliprole) – Controls: RWW, Armyworm? Colsasipis? –Cruiser (thiamethoxam) –NipsIt Inside (clothianidin) –Controls: RWW, colaspis, aphids, – chinch bugs, thrips

Seed treatment trials 2019 –10 Treatments combinations –Early planted (March 22) and late (May 2) –Stand counts (not presented) –3 cores/plot taken at 4 and 5 weeks after permanent flood –Whiteheads and yield data

Seed Treatment Combination Trial 2019 35 30 Early planted A A 25 A Late Planted AA A 20 B B 15 B B RWW/Core 10 B B B B BC 5 C CC C C 0

Early: F = 39.5, df = 9, 27; P < 0.001 Late: F = 21.3, df = 9, 27; P < 0.001

7 Seed Treatment Combination Trial 2019

7 Early planted 6 Late planted 2 AA A 5 AB AB 4 AB 3 AB

2 B B B B

Whiteheads/m B 1 0

Early: F = 1.3, df = 9, 30; P = 0.287 Late: F = 21.3, df = 9, 27; P < 0.001

Seed Treatment Combination Trial 2019

11000 Early planted 10000 Late planted 9000 8000 A A AB 7000 A AA 6000 AB B B B 5000

Yield (lbs/acre) Yield 4000 3000

Early: F = 1.1, df = 9, 30; P = 0.392 Late: F = 21.3, df = 9, 27; P < 0.001

Relative yield loss 2019 –Unprotected (RWW and borers) –RWW only (Prevathon sprayed) –Borers only (Fortenza + Cruiser) –Protected (Dermacor X100)

–Early planted (March 29) and late (May 17)

8 Relative Yield Loss Trial 2019

30 A Early planted 25 Late planted A A 20 A 15

10 B B RWW larvae/coreRWW 5 B B 0 Protected Weevils only Borers only Unprotected

Means from 3 corers per plot at two sampling dates

Early: F = 57.8, df = 3, 12; P < 0.001 Late: F = 27.7, df = 3, 12; P < 0.001

Relative Yield Loss Trial 2019 12 Early planted 10 A Late planted A 8

6

4 A Whiteheads/m2 2 A B B B B 0 Protected Weevils only Borers only Unprotected

Early: F = 57.8, df = 3, 12; P < 0.001 Late: F = 27.7, df = 3, 12; P < 0.001

Relative Yield Loss Trial 2019

Early planted Late planted

8000 A A 7000 A 6000 B B B B B 5000

4000

3000

Yield (lbs/acre) Yield 2000 B 1000

0 Protected Weevils only Borers only Unprotected

Early: F = 15.4, df = 3, 12; P < 0.001 Late: F = 3.7, df = 3, 12; P < 0.044

9 Foliar insecticidal control - 2018 Applied 35 days after permanent flood 6 A 5 4

3 B 2 BC

Whiteheads/m2 1 C C 0

P < 0.001

Foliar insecticidal control - 2018

10 9 33 Days after flood A 8 A 7 22 Day after flood A A 6 5 4 3 2 B B B B Whiteheads/m2 B B 1 0

P < 0.001

Apple Snails Recorded high densities in rice and crawfish in Vermilion Parish

Impacts to rice likely minimal, research is on-going.

10 Apple Snails

Crawfish will be impacted

Apple Snail Distribution

*Estimated from detections in rice/crawfish farms

Slow the Spread

Mermentau and Vermilion rivers and tributaries are infested Check surface water irrigation sources for presence of snails

Source crawfish stock from uninfested areas

Egg masses can be transported on boats or other equipment

Report new infestations to AgCenter extension agents

11 Chemical Control

Copper Sulfate is Effective

2 ppm (≈8 lbs crystals/ acre-ft) in rice

Not safe for crawfish!

Crop Oil Reduces Egg Hatch

12 Questions? Blake Wilson [email protected] 985-373-6193

Call me or your extension agent with any questions.

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