Key For Identifying Pests Based On Feeding Damage

Feeding DamageThe following key is helpful in arriving at the general pest type based upon feeding damage. Start by select 1a, 1b, or 1c, as appropriate. Then proceed to numbered pairs as instructed.

1a. Leaves with damage – see #2

1b. Twigs or bark with damage – see #10

1c. Roots with damage – see #15

2a. Leaves appearing chewed or skeletonized (veins remaining) with tissue between veins on lower side missing – see #3

2b. Leaves not chewed; either off-colored and appearing “stippled” or silvery, or having galls or swollen tissues – see #5

3a. Leaves chewed mostly along margins – see #4

3b. Leaves chewed mostly underneath, appearing skeletonized: leaf beetles, pear ‘slug'(a wasp larva)

4a. Chewed leaf margins semicircular and smooth; not jagged: cutter bee (common on roses), blackvine weevil (common on euonymous)

4b. Chewed leaf margins jagged and irregular; not smooth and semicircular: grasshoppers; caterpillars; Japanese beetle

5a. Leaves with swellings or galls – see #9

5b. Leaves without swelling or galls, but stippled and silvery – see #6

6a. Leaves silvery in irregular pattern when view from above: thrips (common in privet)

6b. Leaves stippled, sometimes appearing grainy or mealy beneath – see #7

7a. Fine webbing present; leaves mealy beneath: spider mites

7b. No webbing present; leaves not mealy beneath; stippled yellow or brown – see #8

8a. Stippled leaves also curled or distorted; use caution here-some herbicides cause similar symptoms: eriopyid mites; leafhoppers; plant bugs; some aphids

8b. Stippled leaves not curled or distorted: many aphid species

9a. Swelling or galls nipplelike on leaf surface: psyllids; eriopyid mites (gall mites)

9b. Swellings variously shaped, but not nipplelike; sometimes on leaf petiole: gall wasps; spindle midges; gall midges

10a. Damage on twigs or buds only, not on main branches or tree trunks – see #12

10b. Damage on main branches or trunks – see #11

11a. Bark partially or completely chewed down to wood:? rodents (squirrels, mice), grasshoppers (in heavy infestations where food supply is short)

11b. Bark with circular or D-shaped holes; may be oozing sap, pitch or frass (‘sawdust’) may be present: borers (larvae of beetles, wasps, and flies); bark engravers (larvae of beetles)

12a. Twigs or buds forming galls or swollen areas – see #13

12b. Twigs or buds without galls; twigs with or central pith with channels – see #14

13a. Galls in buds: gall-forming eriophyid mites

13b. Galls in twigs: gall midges

14a. Twigs with holes, pith not channeled: borers; bark engravers; weevils

14b. Twigs with channeled pith: shoot-tip borers (larvae of moths); pith borers; cane borers

15a. Young roots with gall-like swellings (caution: some plants such as those n the pea family have nitrogen-fixing nodules on their roots, which look similar; these are beneficial): nematodes

15b. Roots chewed or with holes – see #16

16a. Roots chewed: rodents, insect grubs (beetle and moth larvae)

16b. Roots with holes: root borers; weevils (often these insects are secondary to roots undergoing decay from fungi)


See also Identifying Insect Pests

See also Key To Plant Abnormalities

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