Traps for Gauging Fumigation Effectiveness in Commercial Facilities - - PowerPoint PPT Presentation

Traps for Gauging Fumigation Effectiveness in Commercial Facilities

James F. Campbell USDA ARS CGAHR, Manhattan Kansas

Evaluation of Treatment Efficacy

 Question: what impact does a

management tactic such as fumigation have on pest populations in mills

 Problem:

 Difficult to accurately

measure pest population

 Difficult to replicate, have

adequate controls, or isolate impact from other concurrent tactics

In Depth Analysis from Two Mills

 Use results of red flour beetle monitoring projects

from two flour mills in the same geographic area

 Six or more years of monitoring data  Total of 23 fumigations performed

 Evaluate impact of fumigations and IPM on pest

populations as measured using pheromone trapping

 Immediate reduction following treatment  Rebound after treatment  Determine what factors impact fumigation efficacy

 Determine if risk thresholds can be developed for

flour mills based on monitoring data

Mill #1

 Monitored continuously - July 2002 - December 2008  Eleven structural fumigations performed, with ten

complete inter-fumigation periods of monitoring data

 Nine with methyl bromide  Two with sulfuryl fluoride

 Starting in November 2004, IPM program improved

 Regular aerosol treatments (1% or 3% synergized

pyrethrins and methoprene)

 Enhanced sanitation  Targeted sanitation and residual insecticide application

in areas where pheromone trap captures were elevated

Mill #2

 Monitored continuously between March 2003

• December 2008

 Twelve structural fumigations were performed,

with 11 complete inter-fumigation periods of monitoring data

 12 with methyl bromide

Pheromone Trapping Program

Tribolium castaneum – red flour beetle Dome Traps Mill #1: 55 traps Mill #2: 32 traps

Mill #1 – Mean Trap Capture

Mill #1 – Mean Trap Capture

Change in Mill Management Aerosol treatments Enhanced sanitation Targeting trap hot spots

Mill #1 – Mean Trap Capture

Mean Trap Capture – Mill #1 Mean Trap Capture – Mill #2

Change in Mill Management Aerosol treatments Enhanced sanitation Targeting trap hot spots

Mill #1 and #2 – Mean Trap Capture

92±2% 78±8% Percent Reduction in Mean Beetle Capture

 Mean capture

(beetles/trap/2 week period) last monitoring period before fumigation compared to mean capture first monitoring after fumigation

Fumigation Efficacy – Initial Reduction in Beetle Captures

 Two mills did not differ from each other in

reduction in trap capture after fumigation

 85±5% reduction in beetles/trap/period (23

fumigations)

 11±3 beetles/trap/period immediately before

fumigation

 1±0 beetles/trap/period immediately after

fumigation

 Only 3 fumigations had no captures

immediately after fumigation

Effect of Season on Efficacy

 Fumigations sorted into spring (April - June) (n=9)

and fall (October – December) (n=11) periods

 Temperature during fumigation for combined mills  Outside temperature differed between seasons

(F=8.90; d.f.=1,16; P=0.0083)

 Fall (11.81.8C) cooler than spring (18.91.2C)

 Inside temperature did not differ between

seasons (F=0.03; d.f.=1,16; P=0.8625)

 Spring (24.61.2C) and fall (24.40.6C)

Impact of Season on Fumigation Efficacy: Reduction in Mean Trap Capture

(F=2.86; d.f.=1,18; P=0.1083) Also no difference in the mean number captured immediately after fumigation

Mechanism

 Beetle capture immediately after fumigation

could result from:

 Survival within structure  Prediction: number captured after

fumigation should be proportional to number present before fumigation

 Test: positive correlation between captures

before and after fumigation (Pearson Correlations,

P<0.05)

Mechanism

 Beetle capture immediately after fumigation

could result from:

 Movement into structure after treatment  Prediction: captures after fumigation

should be greater after warm season fumigations then after cool season fumigations

 Test: no significant difference between

seasons (GLM: P>0.05)

Rebound after Treatment

 How numbers captured change over time after

treatment – rate of increase or rebound

 Rebound influenced by…  Survival within the structure  Immigration

 Recolonization by individuals driven out during

treatment

 Colonization by new individuals (own movement or

infested inbound products)

 Reproduction - impacted by environmental

conditions and management tactics

Fumigation Efficacy – Rebound in Beetle Captures

Time after Fumigation (Days) Mill #1 Mill #2

spring summer fall

Population Growth

from Price (1984) Exponential Growth Logistic Growth to Carrying Capacity

 Different simple models for population growth with

and without competition

 Tested how well trap captures after fumigation fit

models, but none explained results well for either combined or individual fumigations

Fumigation Efficacy – Rebound in Beetle Captures

Time after Fumigation (Days)

Mill #1 Mill #2

spring summer fall

 Developed threshold value to compare

rebound rates – 2.5 beetles/trap/2 wk period (= median trap capture prior to fumigation)

Fumigation Efficacy – Rebound in Trap Captures

 Two mills did not

differ from each

• ther in the time

required to reach threshold (Kaplan-

Meier log-rank test: Z=0.702, P=0.402)  Mill #1 did not

reach threshold two times, but Mill #2 did not reach on six

• ccasions

Time after Fumigation (Days)

Combined Mills and Seasons

174±33 days (n=21, 8 did not reach)

Fumigation Efficacy – Rebound in Beetle Captures

 Significant effect of season on rebound to mean beetle

capture threshold (Z=10.389, P=0.006)

Time after Fumigation (Days)

Sorted by Season

248±50 days (n=9, 5 did not reach) 104±21 days (n=9, 3 did not reach)

Proportion of Post-Fumigation Periods that had Not Reached Mean Trap Capture Threshold

Before and After Management Changes (Mill #1)

GLM: F1,166=64.91, P<0.0001

Before and After Management Changes (Mill #1)

GLM: F1,9=0.04, P=0.8438

Before and After Management Changes (Mill #1)

 Change in management increased rebound time  Reduced from 2-3 fumigations/year to 1

fumigation – just in the fall

Time after Fumigation (Days)

49±15 days (n=5, 0 did not reach) 246±71 days (n=5, 2 did not reach)

Mean Threshold

Mechanism

 Slower post-fumigation rebound time after change

in IPM program could result from:

 Reduction in founder population  Prediction: reduced number captured after

fumigation increases rebound time

 Test:

• 1. number captured immediately after

fumigation lower after IPM change (GLM, P<0.05)

• 2. significant negative correlation between

rebound time and number after treatment

(Pearson Correlations, P<0.05)

Mechanism

 Slower post-fumigation rebound time after change

in IPM program could result from:

 Change in season when fumigation performed  Prediction: cooler temperatures inside mill

after fall fumigations results in slower population growth

 Test: comparing change in capture from one

monitoring period to the next: season was significant factor (GLM, P<0.05)

Mechanism

 Slower post-fumigation rebound time after change

in IPM program could result from:

 Increased mortality due to enhanced IPM  Prediction: aerosol treatments, extra

sanitation, and targeted responses reduce pest population size and colonization ability

 Test: comparing change in capture from one

monitoring period to the next: IPM program and interaction between IPM and season were not significant (GLM, P>0.05)

Management Thresholds based on Trapping

 Focused on change in trap capture from one

monitoring period to the next

 If rebound in beetle captures fits an exponential

function, size of increase should increase with increasing mean trap capture

 Goal to keep beetle captures

in the relatively flat portion of the rebound curve – where potential increases will be smaller

Exponential Growth

Risk Thresholds – Mean Trap Capture

 Positive correlation

between number captured and change from the previous period (Pearson

Correlation Coefficient, P<0.001)

 No correlation between

number captured and change in number in next monitoring period (P=0.151)

Risk Thresholds – Mean Trap Capture

 Above and below the 2.5 beetles/trap/monitoring period  Overall - below: 0.34±0.08 above: 1.76±0.8 (Not significantly different Mann-Whitney rank sum test, P=0.607)  Just intervals with increase - below: 0.9±0.2 above: 5.4±1.2 (Significantly different, P<0.001)

Expand Dataset to Include More Mills (Twelve Wheat or Rice Mills)

 691 monitoring

periods in 12 mills

 Significant

difference in captures in next monitoring period above and below threshold

(Mann-Whitney Rank Sum Test, P<0.001)

• 0.37±0.12

1.31±0.72

Conclusions

 Provides baseline data on how fumigation impacts pest

populations – as measured using pheromone traps

 Need to add additional locations/fumigations into analysis  Look at relationship between trap captures and other

measures of pest activity (tailings, inspections, etc.)

 Shows how population rebound can be manipulated to

reduce the need to fumigation – management tactics and especially time of year may contribute

 Need further evaluation of impact of IPM tactics alone and in

combination – especially sanitation

 Model population growth under different conditions  Evaluate how risk thresholds might be used to guide pest

management programs

Acknowledgements

james.campbell@ars.usda.gov ars.usda.gov/npa/cgahr/spiru/campbell Collaborators –

• F. Arthur, M. Toews, and T.

Arbogast Funded in part by – USDA CSREES RAMP, PMAP, Methyl Bromide Alternatives programs Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U. S. Department of Agriculture