Crop Injury in More Detail

1. Crop Injury in More Detail • Crop Injury • Tissue Injury • Leaves • Structural • Roots • Flowers and Fruiting/Reproductive Tissues • General Systemic Injury • Competition • Water, Light, Nutrients • Allelopathy

2. Tissue Injury to Leaves Abscission -- Leaf prematurely dropped by the plant, often while still green.

3. Tissue Injury to Leaves Bleaching Leaf turns white or nearly so. Usually caused by using the wrong herbicide.

4. Tissue Injury to Leaves Chlorosis Leaf tissue loses its chlorophyll and turns yellow. May occur in spots. Chlorosis in soybeans. Individual leaves (left) and at the field level (right).

5. Tissue Injury to Leaves Crinkling Leaf takes on a crinkled texture. Usually associated with viruses or toxic effects of saliva from homopterous insects. Crinkling may occur throughout the leaf (left) or may be confined to edges (right).

6. Tissue Injury to Leaves Cupping and Curling Leaves cup up or down or they curl inward from the edges. Downward cupping along main vein of each leaflet in soybeans caused by Bean Common Mosaic Potyvirus

7. Tissue Injury to Leaves Edge Feeding Leaves chewed and eaten from the edges. Feeding lesions can have smooth or jagged edges. Usually caused by insects w/chewing mouthparts. Leaf edge feeding on rhododendron leaves by adult black vine root weevils.

8. Tissue Injury to Leaves Hole Feeding Leaves have holes chewed through them. Caused by insects w/chewing mouthparts. Yellow poplar weevil adult feeding on yellow poplar

9. Tissue Injury to Leaves Mines Caused by small, immature beetles or flies that live in-between the upper and lower leaf surfaces. The shape of the mine, along with the plant species being attacked, is useful in identifying the pest species involved. Frass-linear leaf mine on birch leaf. Mines come in many shapes.

10. Tissue Injury to Leaves Mottling Leaf is not uniform in color but is, instead, a mottled mixture of different shades of green to yellow. Soybean leaf mottling caused by the Bean Pod Mottle Virus.

11. Tissue Injury to Leaves Necrosis Areas of dead tissue which usually sloughs off over time. Necrosis simply means dead tissue and may occur in any pattern. Necrosis may be in spots (top left), on leaf margins (above), or follow leaf veins (bottom left). Other patterns are possible as well.

12. Tissue Injury to Leaves Rolling Leaf is rolled up like a cigar. Usually caused by caterpillars that use the rolled leaf as a pupation chamber. Leaves may be rolled entirely (above) or only partially (left).

13. Tissue Injury to Leaves Shothole Small holes in a straight line across the leaf. Usually caused by insects that bore through the developing leaf when the un-emerged leaf is still rolled up in the plant’s whorl.

14. Tissue Injury to Leaves Skeletonization Leaf tissue between the veins is removed but the veins remain intact leaving a skeleton-like appearance. Lindin leaf skeletonized by Japanese beetle. Note that the distal leaf tissue is relatively normal looking indicating that the leaf veins are fully functional.

15. Tissue Injury to Leaves Spots Caused by fungal, bacterial, and viral diseases. Spots vary in size, shape and number and may be solid or only peripheral (e.g. ring spot, frog-eye spot). Fungal leaf spot on soybean Bacterial leaf spot on pepper Viral ring spot on purple cone flower

16. Tissue Injury to Leaves Stippling Large numbers of tiny pin-prick feeding lesions cause by mites or other minute herbivores with piercing-sucking mouthparts. Leaf stippling by leaf hoppers (sucking insect). Non-uniform pattern. Stippling = dead cells surrounding feeding puncture.

17. Tissue Injury to Leaves Windowpaning One side of the leaf is scrapped off leaving the other side intact and translucent. This gives the feeding lesion a window-like appearance. Primarily caused by some young beetle and moth larvae. Cereal leaf beetle windowpaning on wheat (left); European corn borer windowpaning on corn (right).

18. Structural Tissue Injury • Galls (may be on any tissue) • Interference with transport • Xylem injury • Phloem injury • Interference with structural support • Shape/appearance impact • Abnormal growth • Shoot dieback

19. Galls Can occur on all tissues; leaves, stems/trunks, branches, roots, etc. Ash flower galls caused by a mite Galls on oak leaves from cynipid wasps Olive knot gall (caused by Pseudmomonas bacteria) on olive main trunk Western gall rust on Ponderosa pine branch Soybean roots with galls from root knot nematode (right) vs. healthy root (left).

20. Structural Tissue Injury -- Xylem Tomato wilt is caused by fungi in the genus Fusarium which plugs xylem tissue preventing water/mineral transport. Many insects, such as the squash vine borer feed on xylem tissue.

21. Structural Tissue Injury -- Phloem Bark beetle gallery (right): The adult Beetle lays a line of eggs along a gallery. The grubs hatch, eat phloem tissue until they mature. Phloem discoloration and necrosis caused by spiroplasma infection. Phloem discoloration by San Jose scale on apple.

22. Structural Tissue Injury – Interference with Structural Integrity Stalk breakage (lodging) caused by fungal stalk rot (left) and European corn borer (right)

23. Structural Injury – Abnormal Growth Many plant pathogens and some insects cause abnormal growth in plants. Common forms are called rosettes (above) and witch’s brooms (right).

24. Root Injury – Fibrous Roots Varying degrees of corn rootworm injury (left) and resulting lodged plants (right) Phytophthora root rot on alfalfa (left); Fusarium root rot on soybean (right)

25. Root Injury – Storage Organs Black rot on carrot (left), nematode injury to carrots (middle), carrot weevil injury (right)