GRASSHOPPERS: many species, Acrididae and Tettigoniidae

ADULT: The most common short-horned grasshoppers (Acrididae) likely to be encountered in and around corn fields include the American grasshopper (Schistocerca americana), the eastern lubber grasshopper (Romalia microptera), and the migratory grasshopper (Melanoplus sanguinipes).  These grasshoppers range in size from 3/4 to 3 1/2 in. long. Their color ranges from green, gray, or brown to blackish with a wide variety of mottled patterns, stripes, or colored patches. Fore wings usually cover the hind wings and abdomen, but in some species the abdomen extends beyond the wing tips. Hind wings and rear legs may be brightly colored with white, yellow, red or green. They have boxy heads, large oval compound eyes and short antennae rarely longer than the head.  The femora on rear legs are enlarged and flattened and the rear tibia are stick-like with many rear projecting spines.  Meadow grasshoppers are the most common long-horned grasshoppers (Tettigoniidae) that feed on corn leaves, particularly in the southern sweet corn growing regions. These are slender, light to bright green grasshoppers with thread-like antennae longer than the wings. They have slender, more cone-shaped heads with small, bulging, rounded compound eyes.  The rear femora of tettigoniids are not as expanded or flatended as in acridids.

EGG: They are deposited as a frothy mass in soil on roadsides or field margins, preferably in grassy areas. Eggs are sausage-like and vary by species in shape (straight to banana-like) and color (orange to brown). Number of eggs varies by species ranging from 18 to 100. Length of egg stage is quite variable, ranging from 14 d in the American to 6 to 8 mo. in the eastern lubber grasshopper.

NYMPH: Nymphs emerge from a hardened egg mass looking like miniature adults without wings. Color may vary considerably from that of adult. Wing buds become visible, and antennae of short-horned grasshoppers develop more segments, as they molt into later instars. Their development rates (ranging from 3 wk to 2 mo.) are highly affected by temperature and food quality. There is no pupal stage.

GENERATION TIME: Variable by species from 1.5 to 10 mo.

DAMAGE: Grasshoppers are a sporadic but potentially serious pest. Consecutive years of drought are conducive to population increase. Corn in northern through central Florida is more prone to short-horned grasshopper damage during summer months. Adults and nymphs feed on leaves, silks and husks usually beginning near field margins. They feed across leaves leaving large notches, and broken or detached leaf tips. Damage in seedling corn can slow growth and result in uneven ear maturity or poor pollination. Southern corn in the Fall and Spring are more prone to damage by long-horned grasshoppers. This damage can be worse in fields with grass weeds. Meadow grasshoppers often feed on young leaves emerging from the whorl, leaving large notches and holes in emerging leaves.

CONTROL: Non-crop feeding species may be temporarily found within the crop, and crop feeding species may be developing in non-crop areas. A sweep net is a good tool for monitoring grasshoppers and to capture them for positive identification. Grasshoppers often develop in weedy or uncultivated fields or field margins.  Control of vegetation in and surrounding fields should be timed several weeks in advance of planting so grasshoppers are less likely to move onto emerging seedlings.  Grasshopper control can be difficult, particularly with older nymphs and adults.  Pesticides are available for post-emergence foliar applications and may be mixed with baits (e.g., wheat bran) for nymphs of some species, such as the migratory grasshopper. Foliar treatments can be more effective if applied to surrounding non-crop areas to kill developing populations of young crop-feeding grasshoppers before they move into the corn field. Formulations, rates, and pre-harvest intervals of insecticides for grasshopper control are listed below for sweet corn (Table 1) and field corn (Table 2).

Table 1.  Chemical control of grasshoppers in sweet corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
chlorpyrifos (Lorsban) 4 E 0.5 - 1 pt 35 fodder, grain; 14 **  
cyfluthrin (Baythrioid 2) 2 EC 2.0 - 2.8 fl oz 0  
cyhalothrin (Karate, Warrior) 1 EC 2.56 - 3.84 fl oz 1  
diazinon (D-z-n) 50 W 1 lb 7  
diazinon (D-z-n AG500) 4 EC 1 pt 7  
diazinon (D-z-n AG600) WBC 12.75  fl oz 7  
esfenvalerate (Asana XL) 0.66 EC 5.8 - 9.6 fl oz 1  
methyl parathion (Penncap-M) 2 EC 2 - 3 pt 3 ears; 12 forage, grazing  
**harvest or grazing of forage or silage

Table 2.  Chemical control of grasshoppers in field corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
chlorpyrifos (Lorsban) 4 E 0.5 - 1 pt 35 fodder, grain; 14 grazing, silage  
cyhalothrin (Karate, Warrior) 1 EC 2.56 - 3.84 fl oz 21  
dimethoate (Dimate, Dimethoate 400) 4 EC 1 pt 14  
dimethoate (5 LB Dimethoate) 5 EC 12.8 fl oz 14  
esfenvalerate (Asana XL) 0.66 EC 5.8 - 9.6 fl oz 21  
ethyl parathion (Parathion) 8 EC 0.75 pt 12  
malathion (Malathion) 5 EC 1.5 pt 7  
methyl parathion (Penncap - M) 2EC 2 - 3 pt 12  
**harvest or grazing of forage or silage