This document discusses insect pests that damage crops and provides examples of common damage symptoms caused by different types of insects. It lists various symptoms such as defoliation, shot holes, notched margins, skeletonization, streaking, mining, leaf cupping, galling, bark ripping, branch dieback, honeydew and sooty mold, fecal spots, protective coverings, fluffy white wax, armored scales, spittle, frass, and root damage. Examples are given of specific insects that cause each type of damage symptom, such as large caterpillars, sawflies, and slugs causing defoliation or leaf beetles causing shot holes. Diagnosing problems is discussed, emphasizing identifying

1. Insect Pests of crops
AB 3101

2. Recognizing Pest Damage
Symptoms

3. Challenges in diagnosing pest
problems
• Many biotic & abiotic agents can cause similar
injury symptoms
• Different plant species have different pest
problems
• The causal agent (e.g. an insect) may no
longer be present when damage is noticed
• Many plant diseases have no external signs
that allow you to positively identify the cause
• Damage may be the result of multiple factors

4. Diagnosing problems—Ask these
questions first, especially if the cause
is not apparent:
• Identify the plant
• Identify the symptoms—look
for causal agents
• How long as the problem been
apparent?
• What parts of the plant are
affected (old/new)? Is it
moving in the plant? Do
symptoms get worse over
time?

13. Web based tools

14. Damage Symptoms

15. Defoliation
Large caterpillars, Sawflies, Slugs,
Grasshoppers

16. Shot holes
Tiny holes in leaves
like gunshot
typically found on
herbs and salad
brassicas
caused by tiny flying
and jumping insects
which land on
leaves and bore
holes right through.
Leaf beetles

17. Notched margins
bite-shaped damage
round the edges of
shrub leaves,
making a scalloped
pattern
Due an insect with large
strong cutting mouth
parts which is chewing
up the leaves from the
edges inwards
Eg.:- Black
vine weevil,
Two banded
Japanese
weevil, Fuller
rose beetle

18. Skeletonization
Leaves between main ribs
slowly and progressively eaten
until skeleton remains
Symptoms of a
creature that consumes
as it crawls, and has
weaker mouth parts,
and so keeps to the
tender part of leaves
Lepidoptera (Moths),
Hymenoptera
(Sawflies), Coleoptera
(beetles).

19. Streaking
Scrape the
surface of the
leaf
Symptoms of a
creature that consumes
as it crawls, and has
weaker mouth parts,
and so keeps to the
tender part of leaves
Thrips

20. Mining
Boxwood leafminer

21. Leaf cupping
Boxwood psyllid, Aphids

22. Leaf or Twig Galling
Gall wasps and flies

23. Bark ripping
Moth and Beetle borers

24. Branch dieback
Boring beetles and moths, Twig girdler,
Twig pruner, Root feeding beetle
larvae, Scale insects

25. Honey dew and Sooty mold
Aphids, Soft scale insects, Leaf/Tree/Plant
hoppers, Whiteflies, Psyllids, Mealybugs

26. Fecal spots
Lace bugs, Thrips, Some plant bugs, Leaf
beetles

27. Protective coverings
Bagworms, Case bearers

28. Fluffy white wax
Mealybugs, Some aphids, Some scale insects,
Some planthoppers

29. Armored scale insects
Soft or hard white, brown, gray to black wax
covers

30. Spittle
Spittlebugs

31. Frass

32. Root damages
Carrot Root Fly, Cabbage Root Fly,
Onion Fly
Grubs