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Silverleaf Whitefly (SLW): Threats and management

issues for broad-acre crops

Richard Sequeira – QDPI Entomology, Emerald

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Acknowledgments

Dr. Paul De Barro – CSIRO

Dr. Peter Ellsworth – University of Arizona

Mr. David Kelly – QDPI, Emerald

Dr. Ali Duale – QDPI Entomology

Ms Alison Shields – QDPI Entomology

Mr. Andrew Moore – QDPI Entomology

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Presentation Overview

The Problem & Summary

Basic aspects of the problem

What you can do about it

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The Threat:Many field crops under threat of elimination due to SLW

– soybean, peanut, sunflower, navy bean, adzuki bean

What Can You Do About It?• Choice of right crop for the right area

• Choice of right crop variety

• Where to plant it (location)

• When to plant it (time of year)

• What chemicals to use - Give nature a helping hand

Summary & Take Home Message

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Distribution• Distributed world-wide• Major pest since early 1980s

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Distribution & History in Australia

•Introduced to Australia in the early 90s

•First identified by Robin Gunning of NSW Ag. as SLW

•Rapidly spread along the Qld & northern NSW coast

•Endemic in coastal horticultural areas

•First discovered in Emerald in 1996

•First major outbreak in cotton in Emerald 2001-02 season

•Now in all major valleys in c/s Qld and n/ NSW

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SLW: IdentificationEggs

Adult 0.8-1.2 mm

Large nymphs 0.6 mm

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SLW Life Cycle

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SLW: Why Is It a Serious Pest?• Wide host range, > 500 plant species

Sesame

Soybean

Weeds – native Rosella

Cotton

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SLW: Why Is It a Serious Pest?

• High reproductive capacity, > 300 eggs

Nymphs and adults on lablab

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SLW: Why Is It a Serious Pest?• Short life cycle, egg to adult in 3 weeks

• Acquires resistance quickly, 2-3 cyclesHigh levels of resistance to Pyrethroids, OPs, Carbamates

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SLW: Why Is It a Serious Pest?

• Capable of reaching outbreak population densities very rapidly

MANAGEMENT

SYSTEM

CLIMATEAfter P. De Barro, CSIRO

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Management Practices Can Cause SLW Outbreaks

• Use of broad-spectrum insecticides

(Ops, Carbamates, Pyrethroids)

• Poor farm hygiene:

Crop residues and abandoned crops

Broadleaved weed hosts in-field

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Production System Can Facilitate SLW Outbreaks

Emerald and surrounding areasCrop Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

SorghumCottonPeanutsD/L CottonSorghum (late)SoybeansD/L SorghumMungbeansPumpkinsRockmelonsWatermelonsD/L SunflowerD/L PulsesCornNavy BeansWheatChickpeas

PlantingFloweringHarvesting

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Climate Can Facilitate SLW OutbreaksNumbers of generations for silverleaf whitefly across a range of locations.

Location

Generations1 Oct – Mar*

Mar – Oct ** Mar –Dec***

Generations per Year

Longest Generation (days, approx)

Narrabri* 4-7 (6) 6-9 (8) 122 days 15 Apr - 15 Aug

Goondiwindi* 5-8 (6) 7-10 (8) 118 days 15 May - 10 Sept

St George* 5-8 (7) 7-11 (9) 102 days 1 Jun - 10 Sept

Biloela* 6-8 (7) 7-11 (9) 92 days 1 Jun - 1 Sept

Emerald* 6-8 (7) 9-12 (10) 77 days 15 May - 1 Aug

Richmond** 6-8 (7) 11-15 (13) 61 days 15 May - 15 Jul

Katherine** 7-9 (8) 13-17 (15) 30 days 15 Jun - 15 Jul

Kununurra** 8-10 (9) 14-18 (16) 30 days 15 Jun - 15 Jul

Broome** 9-10 (9) 14-18 (16) 30 days 15 Jun - 15 Jul

Bundaberg*** 5-7 (6) 7-11 (9) 87 days 1 Jul – 25 Sept

Bowen*** 7-11 (9) 10-14 (12) 45 days 1 Jun – 15 Jul

Ayr*** 7-11 (9) 10-14 (12) 45 days 1 Jun – 15 Jul

Gatton*** 4-7 (5) 6-10 (8) 108 days 15 May – 1 Sept 1 Generations from 1st of the month to 1st of the month. (After P. De Barro, CSIRO)

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SLW Risk Assessment for Broad-acre Crops

Seasonal Risk Level Region Crop Crop Risk Winter Oct Nov Dec Jan Feb Mar Apr

CQ Soybean VH X X XX XX XXX XXX XX Peanuts M-H XX XX XX Navy M? XX XX Sunfl M-L X X Mungs L-M X X X X X XX XX Q Coast Soybean VH X X X XX XX XXX XXX XX Peanuts M-H X X X X X XX XX XX Mungs L-M X X X X X XX XX XX Burnett Soybean H X X XX XXX XX Peanuts M X X XX XX XX Navy M? X X X X X XX XX Mungs L-M X X X X X XX XX Sunfl M-L XX XX X SQ/DD Soybean M X X XX XX X Mungs L-M X X X XX X X Sunfl M-l X X XX XX X X Navy M-L? X XX XX X NSW-NR Soybean H X XX XXX XXX XX Azuki H X XX XX X Lucerne H X X X X X X X S/Legs H X X X X X

Risk Rating; X - Low, XX - Medium, XXX - High

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SLW Management……depends on 3 basic keys

• Proper samplingThresholds for each cropWhich part of the plant to sampleHow frequently to sample

No protocols developed to dateOn-going research on susceptibility and

management of grain and pulse crops

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SLW Management……depends on 3 basic keys

• Effective chemical use What is NOT effective?Pyrethroids, Ops, Carbamates

What is effective?IGRs, neonicotinoids (acetamiprid, thiomethoxam),

diafenthiuron

Bio-rationals (oils, soaps) – calendar spraying

What can you afford to use?Proper coverage is essential

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SLW Management……depends on 3 basic keys

• Avoidance

• Do not plant when other host crops in the area are finishing

• Do not plant adjacent to cucurbits, sweet potato and other good host crops

• Varietal differences within a crop – some more susceptible than others

University of Arizona

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Give Nature a Helping Hand

Parasitic wasps

Encarsia Eretmocerus

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Give Nature a Helping HandMean number of large nymphs on sow thistle 2001 vs 2002

0.00.51.01.52.02.53.03.54.04.5

NE NW SE SW FoleyRd

District

Mea

n ny

mph

s/cm

2

20012002

Source: Paul De Barro, CSIRO

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Give Nature a Helping HandSLW nymphs on cotton2001-02 versus 2002-03

0.00.20.40.60.81.01.21.41.61.82.0

Oct

_01

Nov

_01

Dec

_01

Jan_

02

Mar

_02

Oct

_02

Nov

_02

Dec

_02

Jan_

03 Mea

n (lo

g X

+ 1)

nym

phs

/ cm

sq

Source: Paul De Barro, CSIRO

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Give Nature a Helping HandSLW: Parasitism Levels in Cotton

0

20

40

60

80

100

Morowitz Tessman Sullivan EAC Barsby Oregan Walters

EFE Foley Rd FSE NE NW SE SW

% P

aras

itism

17/12/200223/01/2003

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What lies ahead?Is SLW here to stay?More than likely

Will it be a problem everywhere, every year?In some years, some spots

Given the current levels of natural mortality – annual problems unlikely, unless flared by local practices

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ConclusionsSLW can be managed effectively by making

well informed choices• Choice of right crop for the right area

• Choice of right crop variety

• Where to plant it (location)

• When to plant it (time of year)

• What chemicals to use - Give nature a helping hand

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Sensible and informed choices can avoid this