Slugs pests in Oregon and the development of novel approaches for their management

Rory Mc Donnell Department of Crop and Soil Science, Oregon State University, Corvallis Gastropods = + Snails Our relationship with slugs Traditionally a repulsive organism

. phobias – American Journal of Clinical Hypnosis Shell-less snails! Slug = snail minus an external shell!

Advantages of no shell: – Squeeze through very tight spaces – Live in environments that snails cannot – Move more quickly i.e. top speed 0.025mph! Slug Body Plan

Keel Ocular tentacles Breathing pore Mantle

Aydin Orstan

Sensory tentacles

Caudal mucus pore Tubercle Slugs as pests . Direct pests of agriculture, horticulture, urban, suburban, and natural areas

Purdue Extension

Choke disease – Jay Pscheidt . Vector human pathogens – e.g. Escherichia coli . Aesthetic damage e.g. mucus and faeces Pest species in Oregon What species are causing the damage? Invasive slugs Predominantly from How confident are you that you can correctly identify different slugs on your farm?

A. Only know it’s a slug B. Know 1 or 2 species C. Know 3 – 5 species D. Know 5 – 10 species E. Know >10 species 0% 0% 0% 0% 0%

A. B. C. D. E. What is this slug? A. Gray field slug B. White soled slug C. Leopard slug D. Banana slug

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A. B. C. D.

Josua Vlach, ODA What is this slug?

A. White soled slug B. Marsh slug C. Banana slug D. Leopard slug

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A. B. C. D. What is this slug? A. Banana slug B. Leopard slug C. White-soled slug D. Dusky slug

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A. B. C. D.

© Evergreen State College - haliotidea

1 cm Roy Anderson - MolluscIreland Current control options

Chemical molluscicides – Metaldehyde e.g. Slug-Fest®, Metarex – Iron Phosphate e.g. Sluggo® – Chelated Iron e.g. Slug Kill® – Methiocarb e.g. Mesurol 75-W® FallBrookFertilizer.com Tillage

Handpicking Traps Barriers e.g. copper © mopatin Which of these molluscicides do you use most often?

A. Metaldehyde B. Iron phosphate C. Chelated iron D. Methiocarb

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A. B. C. D. How satisfied are you with the performance of molluscicides?

A. Very unsatisfied B. Unsatisfied C. Neither satisfied or unsatisfied D. Satisfied E. Very satisfied 0% 0% 0% 0% 0% A. B. C. D. E. How much (approx.) do you spend on molluscicides per acre each year?

A. <$10 B. $11-25 C. $26-50 D. $50 - $100 E. >$100

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A. B. C. D. E. How much (approx.) do you spend on slug control per acre each year?

A. <$25 B. $26 - $50 C. $51 - $100 D. $101 – $200 E. $201 - $500 F. >$500 0% 0% 0% 0% 0% 0% A. B. C. D. E. F. Considering overall costs and damage, how would you rank slugs as a pest on your farm?

A. The worst B. Second worst C. Third worst D. Top 5 E. Top 10 0% 0% 0% 0% 0% 0%

F. Not top 10 A. B. C. D. E. F. New approaches to control

Development of attractants

Biological control using natural enemies

Novel attractants

Forestryimages.org

Biological control using nematodes Biological control using insects 1. Novel attractants

Giant African Snails – idtools.org

examiner.comJames Smith and Glenn Fowler (USDA-APHIS-PPQ-CPHST) Novel attractants Novel attractants

Asian semi-slug

Site 1 Site 2 Food Extract Water Food Extract Water Giant African Snail 200 109 53 26 Asian semi-slug 133 72 103 53

The mean number of collected Giant African Snails and Asian semi slugs was significant greater (P<0.05) in the food extract versus water plots Novel attractants

Extract appeared to increase bait efficacy Potential for point source applications of attractant and molluscicides

Decreased molluscicide use Decreased non-target effects Increased bait efficacy Novel attractants What about novel attractants for other species?

Gray field slug

Highly attractive food source identified for both species in late 2016 Cucumber as a novel attractant 2. Biological Control

Use of natural enemies to suppress a pest populations

Under researched for gastropods even though: – Diverse fauna of natural enemies – Biocontrol agent is available in Europe Biological Control

. Nematode: Phasmarhabditis hermaphrodita

. Lethal to pest slugs and some snails

. 12 million infective juveniles in clay

. Easy to apply

. Gastropod specific

. 89% reduction in damage to winter wheat

. >95% reduction in orchid damage Biological Control Not currently available in

2,522 specimens 11 slug species 5 snail species

geology.com Nematodes 700 dead slugs and snails >40% had associated nematodes Phasmarhabditis hermaphrodita

© Irma Tandingan De Ley Gray Field Slug Marsh Slug Biological Control

How infectiveGiant is African the Snail US strain of the nematode?

Roy Anderson - MolluscIreland

FLICKR - Shadowshador

European Brown Garden Snail Valencia Slug Paul De Ley – UC Riverside Nematodes

Nematodes will likely be an important tool for managing slugs and snails in Oregon

Preliminary screening has identified parasitic nematode species in the state (Ross et al. 2010)

Climate conditions should facilitate biological control

Demonstrated efficacy in Europe for key vulnerable Alloionema appendiculatum – Irma Tandingan De Ley crops Predaceous ground beetles

. Major predators of slugs

. Successfully used in the UK

. Beetle banks -> native grass LePotager.com mounds

. Safe overwintering = spring

. Oregon beetle banks!

Beetle Bank in Oregon - Gwendolyn Ellen If novel tools such as biocontrol were developed for slugs how likely are you to use them if they were the same price as current methods?

A. I would try B. I would wait for others to try first C. I would not try

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A. B. C. If these novel tools were more expensive than current options but gave more reliable control how likely are you to use them?

A. I would try B. I would wait for others to try first C. I would not try

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A. B. C. Conclusions

No quick fix or a single silver bullet for slug and snail control

Must develop novel tools

An Integrated Pest Management (IPM) approach will be key Acknowledgements US Department of Agriculture Oregon Seed Council Agricultural Research Foundation

Matt Klein Maria Cordoba Andy Colton Any questions!

E-mail: [email protected]

Twitter: @RoryJMcDonnell