Michael Brewer/John Gordy, Texas A&M AgriLife Research/ExtensionDavid Kerns, LSU AgCenterDavid Buntin, University of GeorgiaNick Seiter, University of ArkansasTom Royer/Ali Zarrabi, Oklahoma State UniversityJeff Gore, Mississippi State University

Background and added analyses can be found in a poster by Gordy et al. at: http://ccag.tamu.edu/sorghum-insect-pests/

What is an optimal spray threshold which results in optimal yield protection?

I. Background: Aphid & Sorghum Damage II. Thresholds for susceptible hybrids Multi-site field experiment (Methods/Results) To the field (Learning/Application)III. Next Steps and Discussion

Financial supporters (Funding and in-kind)

State Grain Sorghum Boards (TX, LA, AR) USDA NIFA Crop Protect & Pest Manage., Applied Res. & Dev. (TX, LA) United Sorghum Checkoff Program/Dow AgroSciences Monsanto/Syngenta/Pioneer/A&M, seed and harvesting

Introduction

Courtesy of M. Way/M. Brewer/G. Odvody, AgriLife Research,R. Villanueva, AgriLife Extension

Asexual reproduction, required green host primarily Sorghum sp.Plant damage caused by general plant decline, head emergence problemsHoneydew and aphids reduce harvest effectiveness

Pre-flowering arrival/increase Less grain/ Aphids/honeydew

No heads at harvest

Background: Aphid & Sorghum Damage

Threshold Experiment for susceptible hybrids

Late PlantingAphids arrived pre-boot

Early PlantingEscaped damage

LGC, UGC, OK, NLA, AR

A. Reyes, C. Stanton, AgriLife Research

2014 1 LGC: Corpus Christi, TX 4 NLA: Winnsboro, LA 2015 1 LGC: Lower Gulf Coast (Brewer) Planted: May 1 (2nd planting) 2 UGC: Upper Gulf Coast (Gordy) Planted: July 16 (3rd planting) 3 OK: Oklahoma (Royer) Planted June 4 (2nd planting) 4 NLA: North LA (Kerns) Planted: May 29 (2nd planting) 5 AR: Arkansas (Seiter) Planted June 9 (2nd planting) 6 GA: Georgia (Buntin) Planted June 15 (1st planting) 7 MS: Mississippi Delta (Gore) Yield failure, birds

Materials & Methods

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Plot size: 40 ft by 4 rows, data taken on inner two rowsAction triggers for foliar insecticide (0 GA only), 50, (100 to 125) , 250 & 500 aphids/leaf & UTC Transform (sulfoxaflor) 1.0 oz per acre, 10-15 GPA

First aphids arrived at 5-6 leaf, pre-flowerSorghum Hybrids: 2014 LGC: RTX430, 1 spray maxNLA: RTX430, 2 sprays max 2015LGC: Dekalb DKS 53-67, 1 spray maxUGC: Dekalb DKS 53-67, 4 sprays maxOK: DK53-67, 1 spray maxNLA: TX430, irrigated, 2 sprays maxAR: P83P99, irrigated, 3 sprays maxGA: SS800A, 3 sprays max

Sorghum ‘S’ Hybrids: Threshold Experiment

Measurements: weekly Aphid density (aphid/leaf) 20 leaves per plot, 10 top-half, 10 bottom-half used quick aphid checker (5-10 min per plot)

Yield

Results in pictures (Upper Gulf Coast Location, J. Gordy)

500 Aphids/Leaf250 Aphids/Leaf50 Aphids/Leaf

Aphiddensities tolerable

Aphiddensities too high

50/100 (S)Few aphids 7-14 DAT, no injury, no yield loss, natural enemies reduced

LGC: 1 sprayUGC: 4 spraysNLA: 2 spraysGA/AR: 3 sprays

250 (S) Few aphids 7-14 DAT, sooty mold detected, no yield loss, abundant natural enemies

LGC: 1 sprayUGC: 3 spraysNLA: 1 sprayGA/AR: 1 or 2 sprays

UTC & 500 (S)High aphids 7-14 DAT, damage visible, yield loss, natural enemy zoo

LGC/UGC: 0 sprayNLA: 0 sprayGA/AR: 0 or 1 spray

2014, 2015 More Results in Pictures, Susceptible TX430 & DKS 53-67 (Pics from Lower Gulf Coast Location, M. Brewer/T. Ahrens)

2015 Yield (Susceptible hybrid)—Max Aphid Load Regression

Upper Gulf Coast3rd plant: DKS 53-67

J. Gordy

D. Buntin Georgia1st plant; SS800A

A. Zarrabi/T. Royer Oklahoma2nd plant; DKS 53-67

Lower Gulf Coast2nd plant; DKS 53-67

M. Brewer

2015 Yield Loss estimates in lbs/acre (and % yield reduction) for every 100 aphids/leaf OK: 121 (6.3), UGC: 151 (13), LGC:227 (13), AR: 314 (7.4), NLA: 355 (7.5), GA: 410 (15)

D. Kerns

N. Louisiana2nd plant; TX430

N. Seiter Arkansas2nd plant; 83P99

From Pedigo’s method EIL = C/(V*I*D*K), C = control cost, V = $ value of grain K set at 0.95 as the proportion of the insect population controlled (taken from efficacy studies)I*D is loss estimate estimated from the slope of yield—aphid/leaf regression

Values in a feasible IPM management zone, here ET = 0.7*EIL 2015 ET variation 30 — 135 aphids per leaf2014 ET variation 50 — 125 aphids per leaf 2015 Example Control Cost $15/acre

Aphids/leafControl Cost $20/acre

Aphids/leafControl Cost $25/acre

Aphids/leafMarket Value Location EIL ET EIL ET EIL ET

$3.50/bushel $6.25/cwt

OK 209 146 279 195 348 244UGC 164 115 218 153 273 191LGC 111 78 148 104 186 130AR 80 56 107 75 134 94NLA 71 50 95 66 119 83GA 62 43 82 57 103 72

$5.00/bushel $8.93/cwt

OK 146 102 195 137 244 171

UGC 115 80 153 107 191 134

LGC 78 55 104 73 130 91

AR 56 39 75 53 94 66

NLA 50 35 66 46 83 58

GA 43 30 57 40 72 50

$6.50/bushel $11.60/cwt

OK 113 79 150 105 188 131UGC 59 41 88 62 118 82LGC 60 42 80 56 100 70AR 43 30 58 40 72 51NLA 38 27 51 36 64 45GA 33 23 44 31 55 39

Using thresholds are dependent on:

ID, sampling, and estimating aphid load Insecticide use within same or few days Excellent insecticides available

Key LearningsET values vary but in a feasible IPM management zone Challenging but we can manage this pest2015: 6 locations, 5 states, 4 hybrids, aphids arrive pre-flowering ET variation 30 — 135 aphids per leaf2014: 2 locations, 2 states, 1 hybrid, aphid arrive pre-flowering ET variation 50 — 125 aphids per leaf

Picking a specific threshold for you: 2015 ET variation 30— 135 aphids per leaf2014 ET variation 50 — 125 aphids per leaf

One responsible approach: choose an ET in the lower part of the range and adjust as you get more information

Location, insecticide cost, grain value

Sampling once ( ET) or twice ( ET) weekly

Is hybrid very susceptible ( ET) or less susceptible ( ET) ??

Is it hot and dry ( ET) or rains and natural enemies ( ET) ??

Next Steps & DiscussionInvestigate surrogates for estimating aphid load Work in progress using existing data from UGC, LGC, and LA sites Link to work on developing sampling toolsInvestigate effects of Plant stage of infestation (attempted this year) Plant health (dryland vs. irrigated situations) Hybrid sensitivity Limited data from UGC, LGC, and LA sites suggest value to added work, change in aphid load/damage Natural enemies Limited data that needs to be organized and need to develop common protocols?