KNOWLEDGE FOR LIFE
Onion disorders
CABI PEST AND DISEASE PHOTOGUIDE TOIntroduction
This photo booklet has been produced
by the CABI-led Plantwise programme
(www.plantwise.org) to aid extension officers
and other plant health advisors in diagnosing
the most common pests, diseases and
abiotic problems of coffee around the world.
The symptoms presented on a real plant
sample can be compared with the photos
in this guide to identify possible causes.
The booklet is organized into two broad
sections, one showing the common insect
pests that attack the crop and the other
showing the various symptoms of poor health.
In the symptoms section, the images are
arranged by plant part, with similar-looking
symptoms displayed together. Some biotic
and abiotic factors cause more than one type
of symptom, so there may be multiple images
in different parts of the photo booklet for a
specific problem. The photos for a particular
problem are cross-referenced to make it easy
to find all the relevant photos.Contents
Sign or symptom Box #
Insects 1–16
Leaf 17–33
Edible portion 34–43
Root 44–461
Cutworms
Agrotis ipsilon Worldwide
• Larvae are brown with grey band along mid-line, brown head.
• Adults are brown moths.
• Most damage is on seedlings, larvae chew stem at soil line
and plant falls over; chew holes in leaves.
Photo: Whitney Cranshaw, Colorado State University, Bugwood.org
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Bean seed fly and Onion fly
Delia platura and Delia antiqua Worldwide
• White, legless and headless maggots, up to 8 mm long.
They eat leaves and bulbs. Delia antiqua is a more specialised pest,
D. platura will usually only infest diseased or damaged plants.
• Both flies can act as entry points for pathogens, especially
Fusarium and bacterial diseases.
Photo: Whitney Cranshaw, Colorado State University, Bugwood.org
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Beet armyworm
Spodoptera exigua
• Young larvae pale green/yellow, with pale stripes; older larvae are
dark brown with darker stripes; mature larvae can reach between
25-30 mm long.
• Eggs greenish to white colour.
• Insect feeds on green part of leaves and make irregular holes.
Photo: Marina Young, Rural Agricultural Development Authority, Jamaica
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Asia, Africa, Central America,
Caribbean, Oceania
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Leek Moth
Acrolepiopsis assectella Asia, Africa
• Greyish-white to pale green larvae with brown head, about
10 mm long; white eggs.
• Bores into the leaf creating translucent windows that turn
into holes.
• Can attack the neck of the onion leading to neck rot.
• Damage is usually first noticed at the edge of the field.
Photo: Mariusz Sobieski, Bugwood.org
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Onion Weevil
Ceutorhynchus suturalis* Africa
• Typical C-shaped weevil grub.
• Appear similar to a maggot but with well developed head
capsule and insect type legs.
*related species shown
Photo: Norman E. Rees, USDA Agricultural Research Service – Retired, Bugwood.org
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Wireworm Agrypnus spp. Conoderus spp. and Heteroderes spp. and others Worldwide
• Larvae have slender, cylindrical bodies and a relatively hard;
yellowish to brown in colour and about 20 mm long.
• Seedlings may be eaten off below ground.
• Holes chewed in developing seedlings.
Photo: Frank Peairs, Colorado State University, Bugwood.org
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Leek Moth
Acrolepiopsis assectella Asia, Africa
• Adults 8-9 mm long, reddish brown to grey in colour.
• Wingspan 15-16 mm, with white triangle shaped spot on
folded wings.
• Active at night.
Photo: Martin Evans, wildguideuk.com
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