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PASTURE GRASSHOPPERS The Midwest Cattleman · August 24, 2023 · P9
By Dave Boxler, Nebraska Extension Educator
Much of Nebraska has stem tissue and by cutting
had several years of below off leaves or stems.
normal precipitation, which
may allow grasshoppers to Control
become a problem. A grasshopper integrated
The 2023 Rangeland pest management (IPM) pro-
Grasshopper Hazard Map gram called Reduced Agent
(Fig 1) indicates ten counties and Area Treatment (RAAT)
in Nebraska that had fall was developed by research-
adult grasshopper numbers ers at the University of Wy-
averaging over 15 per square oming to improve grasshop-
yard. These data are based on per control in pastures and
the 2022 adult survey, which rangeland. This chemical
is a good indicator of possible control strategy utilizes the
grasshopper issues for the insecticide Dimilin which
summer of 2023. Economic interferes with the molting
thresholds for grasshopper process of grasshoppers. Di-
densities in rangeland vary milin is applied in alternat-
from 8 to 40 grasshoppers ing strips, reducing applica-
per square yard. The thresh- tion costs by 50 to 60% and
olds are influenced by sever- reducing the amount of in-
al factors, including the cost secticide used by 65 to 70%,
of control product, projected Monitoring Approximately 50 species compared to conventional
forage yield, and the value of One of the better methods of grasshoppers are found broadcast treatments. The
forage considered for treat- for determining grasshopper on rangeland in Nebraska, RAAT system provides up to
ment. density is to count the num- though generally fewer than 85% control, depending upon
Grasshoppers consume up ber of grasshoppers using 10 species ever reach eco- rate of growth of the forage,
to 50% of their body weight the square foot method. With nomic levels, accounting for the size of the grasshoppers
every day in forage. A rate this method, sample at mul- 95 percent of the damage. and the coverage obtained.
of just 2.7 grasshoppers per tiple sites about 50 to 75 feet Grasshoppers defoliate grass
square yard equals 12,971 apart. Select a point sever- by direct feeding on leaf and
grasshoppers per acre. An al feet away and visualize a
acre with 69.7 grasshoppers one-foot square area around
per square yard equates to the point. Walk toward the
the consumption of forage by point, counting any grass-
one cow per day. hoppers you see in or jump-
Pasture grasshopper spe- ing out of this area. Repeat
cies that are most damaging 18 times, total the number of
are found in areas with less grasshoppers, and divide by
than 30 inches of annual 2. The resulting number will
rainfall. The western two- be the number of grasshop-
thirds of Nebraska fall into pers per square yard.
this rainfall category. With
the occurrence of consecutive Life Cycle
years of drought, grasshop- The developmental stages
per outbreaks are possible. of all grasshoppers include
The past several years south- the egg, nymphal, and adult
western, southcentral, and stages. Most species overwin-
western Nebraska has expe- ter as eggs. Normally, grass-
rienced below normal precip- hopper eggs will remain in
itation. This type of weather the overwintering stage until
pattern can play a large role the ground temperature
in rangeland grasshopper reaches 50° to 55° Fahren-
outbreaks, and monitoring heit. Newly hatched grass-
grasshopper numbers is im- hoppers look like miniature
portant to figuring out what adults except they lack wings,
action may be required. and their sex organs are not
developed. As young grass-
hoppers grow, they shed their
skin (molt). Depending upon
the species, they might molt
four to six times, with five
molts being the average. The
rate at which nymphs devel-
op is influenced by tempera-
ture and food quality. Most
species reach the adult stage,
30 to 50 days after hatching.