Why Do Efficacy Trials Vary

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Why Do Efficacy Trials Vary So Much?????
Bob Vernon1 and Wim van Herk1
1Pacific Agri-Food Research Centre, Agriculture
and Agri-Food Canada, Box 1000, Agassiz,
British Columbia, CANADA, V0M 1A0
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Myth 1
A wireworms a wireworms a wireworm!
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Canadian wireworm pests
Ctenicera

• Ctenicera destructor/aeripennis (BC, AB, SK, MN)
• C. lobata, C. morula (AB, SK, MN)
• C. pruinina (OR, ID)
• Agriotes obscurus, A. lineatus (BC, NS, PEI)
• A. sputator, A. mancus (NS, PEI)
• Athous spp (AB, SK, MN)
• Limonius canus, L. californicus (BC, AB)
• Melanotus spp (ON)
• Hypolithus spp (SK)

Agriotes
Hypolithus
Limonius
Athous
Melanotus
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EFFICACY
A wireworms a wireworms a wireworm!
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Field insecticide efficacy trials.
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What about the rest of Canada?????
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Field insecticide efficacy trials.
Potato trials 2004 Agassiz, BC (WW
TFB) London, Ont (CPB LH) Kentville, NS
(CPB) Bouctouche, NB (flood)
2005 Agassiz, BC (WW TFB) London, Ont
(WW) Kentville, NS (WW) Winnipeg, Manitoba
(flood)
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British Columbia

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Why the differences????

• Different regions/environments.
• Different species.
• Different toxicities between species.
• Different intoxication periods
• between species.

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REPELLENCY
A wireworms a wireworms a wireworm!
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Soil Windows
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inside yellow line orient inside red line
contact
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Proportion repelled after contact
SP-1 Synthetic pyrethroid
AO Agriotes obscurus
LC Limonius canus
cruiser SP-1 AO
SP-1 AO
SP-1 LC
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Take home messages.

• Different species of wireworms may express
• different responses to insecticides, leading
  to
• -Varying levels of crop protection (esp
  potatoes)
• -Varying levels of intoxication
• -Varying levels of mortality
• -Varying levels of repellency

2. Knowing the wireworm(s) we are dealing with
in research right down to species is a must
if we want to accurately report compare data.
3. This might extend to the applied level as
well.
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Myth 2
Insecticide efficacy is not related to land
preparation prior to planting
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Wireworm Life History Important Information to
Know
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What happens if you go directly from pasture to
potatoes??
In spring, wireworms are near soil surface
feeding on various grasses, weeds, or winter
cover crops. They are attracted to carbon
dioxide CO2.
If the field is plowed green, or if vegetation is
not completely killed before plowing, wireworms
will remain with the green manure until it rots
away due to continued presence of CO2.
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What happens when you plant?
Wireworms mostly pre-occupied with green manure
during planting
Although you might use an insecticide at
planting, you will not kill many wireworms.
Control must be close to 80 in the first month
after planting.
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Planting potatoes in a green-plowed field, even
if you use an effective insecticide, will
not kill enough wireworms to prevent damage!!!!!!
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Best Option Fall or Summer fallow prior to
planting potatoes the next year
Wireworms in grass or pasture in fall will
continue to feed after plowing due to presence
of CO2.
Green manure rots over the winter to leave a
fallowed field with few sources of CO2 in the
spring.
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Spring planting in fallowed field
The primary source of CO2 in the field at this
time is the seed pieces.
The majority of wireworms in the soil will visit
these seed pieces at least once during the
first month after planting.
If there is a granular or liquid wireworm
insecticide in the seed furrow, or if the seed
pieces have been treated with an insecticide, you
have a good chance of killing most wireworms in a
well fallowed field!!!!!
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These scenarios may explain why

• Broadcast treatments sometimes work better
• than in-furrow treatments, or vice versa.
• -Broadcast good in field with random sources
• of C02 (i.e. green manure).
• -In-furrow good in well fallowed fields.

2. Treatments expected to work well (e.g.
Thimet) sometimes give mediocre results.
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Take home messages.

• In research, land prep is a critical variable and
  
• should always be considered and recorded.

2. For growers, they should be informed that
competing CO2 sources at planting (e.g. green
manure) will reduce pesticide efficacy.
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Myth 3
Control of wireworm damage to a crop signifies
control of wireworms
In some cases it does
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In some cases it doesnt.
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OF UNTREATED
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My hypothesis
The most effective soil insecticides will work
well for only about one month (with exception
of fipronil).
In a well fallowed field in spring, the
majority of wireworms in soil will visit the
treated area at least once.
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Myth 5
Choosing wireworms as a study organism is a
smart career move and will guarantee tenure and
promotion in record time.
NOT!!
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