South
Florida
Beef -
Forage
Program
"Article of the Month"
August 2001
Identification of Fall Pasture Insect Pests
Jim Selph
Desoto County Extension Agent
As we approach the end of Summer,it is time to begin to think about the
insect pests that we normally have to deal with, beginning in August, each
year. Those insects normally are: Fall Armyworms and Spittle Bugs.
The Spittle Bug ( Prosapia bicincta) is an insect
with piercing/sucking mouthparts, that inject toxic juices into the plant.
Forages that are particularly susceptible are Bermuda, Limpograss, Pangola, and
Rhodesgrass. Adults of the two-lined spittlebug have the characteristic
leafhopper shape and are dark brown to black with red legs and eyes. It gets
its name from the conspicuous two red to orange lines across its wings. Nymphs
are cream-colored with brown heads and eyes. They produce a white, frothy mass
that completely hides them as they feed.
These nymphs can usually be found in the crowns of the grass by digging
down into the grass at soil level. During the summer, eggs hatch in 15-19 days
and the nymphs begin feeding and producing the frothy mass immediately. Nymphs
feed for 30-50 days before molting into the adult stage. On average, each adult
female lays 45 eggs. There are two and occasionally three generations a year in
Florida. Damage Causes Leaf Burn (Yellow Tips) & Dieback. Leaves will show
streaking or stippling and sometimes complete loss of stand can occur.
When walking through a grass field such as this limpo,
observe for small dark insects that seem to dart away from you as you move
through the field. A close up view of
the crown of the grass will reveal the spittle mass and the immature larvae of
the spittlebug.
The Fall Armyworm (Spodoptera frugiperda) is native to the
tropical regions of the western hemisphere from the United States to Argentina.
It normally overwinters successfully in the United States only in southern
Florida and southern Texas. The fall armyworm is a strong flier, and disperses
long distances annually during the summer months. It is possible for the moth
to move distances as great as 300 miles. The Generation interval in
Florida through late Spring,
Summer and early Fall is about every 30 days, with the peak months being June
through September.
The egg is dome shaped; the base is flattened and the egg
curves upward to a broadly rounded point at the apex. The egg measures about
0.4 mm in diameter and 0.3 m in height. The number of eggs per mass varies
considerably but is often 100 to 200, and total egg production per female
averages about 1500 with a maximum of over 2000.
Pupation normally takes place in the soil, at a depth 2 to 8
cm. The larva constructs a loose cocoon, oval in shape and 20 to 30 mm in
length, by tying together particles of soil with silk.
Duration of the pupal stage is about eight
to nine days during the summer, but reaches 20 to 30 days during the winter in
Florida.
Observe the inverted V on the head of the Fall Armyworm
The moths has a wingspan of 32 to 40 mm. In the male moth,
the forewing generally is shaded gray and brown, with a triangular white spots
at the tip and near the center of the wing. The forewings of females are less
distinctly marked, ranging from a uniform grayish brown to a fine mottling of
gray and brown. The hind wing is iridescent silver-white with a narrow dark
border in both sexes.
 |
 |
| Male | Female |
Monitor or walk through pastures on a regular basis.
By observing the head of the worm you should
be able to identify it as an Armyworm by observing for the inverted V.
The threshhold is 2 to 3 worms per square
foot. If control is attempted, the best
time is when the worms are ½ inch or less in length.
When we find a field that the worms are 1 ¼ inches in lenth,
spraying will not be a viable option.
Adult moths are most active during warm humid evenings.
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Identification of Fall Pasture Insect Pests
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