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p AGRICULTURAL RESEARCH CENTER, HASTINGS, FLORIDA
Hastings ARC Research Report 1983-1 Jan. 1983
DIAGNOSIS OF INSECT OR SIMILAR DAMAGE ON CROPS IN THE HASTINGS AREA
R. B. Workman, Assoc. Entomologist
Different species of insects damage Florida crops at various times during the year and
many times damage occurs but the insect producing it is rot--re c-found .-Lfe.ctive
control generally depends on applying a prescribed treat ie [Jjre.p[p tiX-os becomee
injurious. Some damage characteristics are listed below which may be useful n ocat-
ing or identifying the pests attacking some NE Florida cops. Hplsem.ade when aves
are small become progressively larger as the leaves grow out. ~hug- '~4fl sht hole
produced by a 1/2" long diamondback moth larva in a cabb ie bud leaf may be 1" r more
across when the leaf is fully grown. If the edge of a h).AS6a- IT, bf Pi gjt corky,
the damage is old and the insect has, likely, moved or plpa-ret--fr---Whe -dmag is old
and insects cannot be found, treatment is unnecessary. A key for identifying the cater-
pillars of cabbage is available at ARC, Hastings and from County Agents in the area. A
number of these caterpillars also attack other crops.
Molecricket: Raised tunnels, 1/4 x 1/2", occur on soil surface of seedbeds. Plants
fall over but are not cut off or fed on.
Cutworms: Plant stem with hole in side or cut off at soil surface. Several plants in
row usually affected. End of leaf often pulled into hole in soil surface where cutworm
is feeding. Damage most common in newly set fields where cutworms were present in pre-
ceeding cover crop.
Diamondback moth larvae: Small holes, 1/8" + occur in leaves. Bud leaves not tied with
silk nor is growing tip destroyed. Shallow tunnels may be produced on top of heads.
Slender, whitish, netted, pupal sacs, 1/2" by 1/8" long often persist on lower leaves.
abbae webworm: Bud leaves contain small, 1/8" +, holes and silk webbing which collects
dirt and trash. Growing point often fed on preventing head formation. Plant lopsided.
Cabbage looper: Large holes occur in leaves and lower head near maturity. Loopers are
hard to find and may have moved to an adjacent plant where little damage is evident.
Fresh droppings indicate that looper is nearby. Pupal cocoon is of white, tangled silk
with one side flattened against the leaf.
Imported cabbageworm: Feeds as above but more openly and is readily found. Often visi-
ble from above. Pupal cocoon papery with sharp projections and fastened to leaf by
tail and silk loop around the middle.
Fall armyworm & cutworms: Holes in the lower leaves, caterpillars boring into heads
in fall. Fall armyworms are most common in or near fields previously in late corn or
sorghum where populations built up.
POTATO -- DAMAGE TO TUBERS
Scavengers: Different species of small, 1/4" +, clear to whitish worms feeding in
damaged or rotting potatoes or seed pieces. Do not damage healthy plants.
Cutworms and Beet Armyworm: Mostly shaTlow holes, 1/8-1" + in diameter, in sides of
tubers which are usually greened due to the lack of soil coverage.
Mole cricket: Holes, 3/8-1/2" in diameter, often penetrating deep into tuber.
Damage can occur at any depth in soil. Tubers often not greened.
Rats: Large, somewhat shallow holes in tubers with marks from teeth visible.
Tuberworm: Small, 1/8" + diameter holes and tunnels in tubers. Tunnels contain
spongy residues and have a corky lining which can be cut out of tuber. Present during
hot, dry weather when soils crack open and on unprotected tubers stored during the
s "-mer. On eggplant, mines leaves and feeds around stem of fruit.
Fire Ant: A recent problem. Tunnels similar to tuberworm but larger and
with many holes through skin. The ants may nest in hollowed tubers.
Wireworm: Tunnels 1/8" dia. or less, usually 1/8-1/2" deep into tuber. Often
fresh and not lined.
Nut rass: Tunnels similar to wireworm but pointed at distal end. Remnants of grass
aay remain in tuber.
POTATO -- DAMAGE ABOVE GROUND
Cabbage looper and Armyworms: Irregular shaped holes in leaves. Fresh droppings in-
dicate that insect is nearby. Shake plants over middles to dislodge for ID.
Colorado Potato Beetle: Irregular shaped holes in leaves made by humpbacked, reddish,
black-spotted larvae. First appearance is usually along one edge of the field which
may be spot treated to limit spread.
Stink Bugs and Plant Bugs: Flower and upper leaf terminals curl and hang down.
Aphids: Leaves are curled and yellowed, turning brown and falling off with heavy in-
festations. Aphids attack the lower leaves first, moving upwards as numbers increase.
Parasitized aphids are swollen and straw colored often persisting on the leaves after
populations have declined.
Leafminers: Brownish, winding tunnels, 1/16" + wide, occur in lower leaves near har-
vest. Damage low. Treatment not necessary.
CORN -- SORGHUM
Cutworms: Plants cut off at soil surface. Leaves often pulled into hole in soil where
cutworm is feeding.
Chinch bug: Young plants wilt and die. Holes not visible in leaves. Small black and
white winged or red plant bugs, 1/16" long, found between leaves or in soil at base
of plant. Damage is from sucking sap from plants.
Lesser cornstalk borer: Plants fall over and die. Stems are hollow with dirt-covered
vsilk tubes in soil about roots. Most common in dry soils. Borers are smooth cater-
pillars, 5/8" + long, with green and brown bands. May tunnel in young cabbage stems.
Sorghum webworm: Thin silk webbing in head. Kernels hollowed out and consumed by
1/2" + long hairy, green caterpillars with 4 brownish longitudinal stripes.
Fall armyworm and Corn earworm: Leaves have several to many holes in row. Silks of
ears cut off. Feeding in tip of ear, extending downward. Husks with 1/4" + diameter
emergence holes in side. Varicolored and striped caterpillars feed in leaf whorls from
time of emergence. At maturity they move to soil and pupate in brown, shiny, segmented
cocoons, 3/4" + long. One end is pointed and moves when disturbed.
Aphids: Leaves with yellowish to reddish tinge. Masses of soft-bodied green to black,
winged and wingless, insects in leaf whorls and about ears.
Stinkbugs: Ear with scattered brown kernels caused by stinkbugs piercing husks
with beak and sucking juices out. Also cause drop of citrus fruit, okra, tomato, etc.
Sorghum midge: Sorghum heads are blighted, seeds hollow. Orange gnats, 1/12" long,
fly about heads in morning and evening. Early sorghum escapes most damage.
Grain beetles & Weevils: Kernels and seeds hollowed out, may contain white, legless
grubs. Whitish "sawdust" about damage. Reddish to black beetles, 1/8" + long,
found on surface and in crevices. Numbers multiply rapidly in storage if untreated.