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
Tissue Injury to Leaves
Abscission -- Leaf prematurely dropped by the plant, often while still green.
Tissue Injury to Leaves
Bleaching Leaf turns white or nearly so. Usually caused by using the wrong
herbicide.
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).
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).
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
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.
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
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.
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.
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.
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).
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.
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.
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
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.
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).
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
Galls
Can occur on all
tissues; leaves,
stems/trunks,
branches, roots, etc.
Ash flower galls
caused by a mite
Olive knot gall
(caused by
Pseudmomonas
bacteria) on olive
main trunk
Galls on oak leaves from
cynipid wasps
Western gall rust on
Ponderosa pine branch
Soybean roots with galls from
root knot nematode (right) vs.
healthy root (left).
Structural Tissue Injury -- Xylem
Many insects, such as the
squash vine borer feed on
xylem tissue.
Tomato wilt is caused by fungi in
the genus Fusarium which plugs
xylem tissue preventing
water/mineral transport.
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 by San Jose
scale on apple.
Phloem discoloration and necrosis
caused by spiroplasma infection.
Structural Tissue Injury –
Interference with Structural Integrity
Stalk breakage (lodging) caused by fungal stalk rot (left) and European
corn borer (right)
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).
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)
Root Injury – Storage Organs
Black rot on carrot (left), nematode injury to carrots (middle), carrot weevil injury (right)