Grasshoppers are a generalist group of plant feeders. Short-horned grasshoppers (family Acrididae) are most commonly observed in soybean. They have short, thread-like antennae with enlarged hind legs which aid in jumping. Grasshoppers have chewing mouthparts, and the adults have two pairs of wings that are folded over their ‘backs’ when not flying. Adults of some species can exceed 2 inches in length. The color patterns of grasshoppers vary considerably because there are multiple species observed in soybean, colors change as they molt from one life stage to another, and because their colors may change to match their environment.
Grasshoppers are an occasional pest of soybean. However, some fields in Tennessee require an insecticide application in most years. Grasshoppers feed primarily on foliage and are part of the defoliating pest complex in soybean, but feeding on flowers, pods and other plant parts is sometimes observed. Leaf feeding is characterized by irregular holes that extend in from the leaf margins or between the leaf veins. Plants are most susceptible to damage when they are small, from the time of emergence to V2. Thus, most serious infestations are seen on seedling soybean plants. Both immatures (nymphs) and adults may feed on the main stems of seedlings and reduce plant stands to the point where replanting is needed. However, serious damage is usually caused by large numbers of nymphs. Grasshopper infestations are often worse following a dry year.
Grasshoppers tend to concentrate on field edges first before dispersing further into the field and are easily observed or caught with a sweep net. However, insecticide treatment is generally based on average defoliation levels and the potential to cause stand loss.
Treatment is suggested when an unacceptable level of stand loss is occurring or defoliation exceeds 30%. Treatment specifically for grasshoppers is rarely needed once blooming has begun, but as part of a defoliator complex, treatment is recommended between first bloom (R1) and full seed (R6) when 20% or more defoliation is observed.
|Insecticide (Trade Names) for GRASSHOPPERS||Lb Active Ingredient per Acre||Amount Formulation per Acre||Performance Rating|
|acephate 90 (Orthene 90S)||0.30 - 0.50||0.33 - 0.56 lb||8|
|bifenthrin (Brigade 2E, Discipline 2E, Fanfare 2E)||0.063 - 0.10||4 - 6.4 oz||7|
|chlorpyrifos (Lorsban 4E, Nufos 4E)||0.25 - 0.50||8 - 16 oz||7|
|chlorpyrifos (Lorsban Advanced 3.755)||0.25 - 0.47||8.5 - 16 oz||7|
|diflubenzuron (Dimilin 2L), for immatures only||0.031||2 oz||8|
|esfenvalerate (Asana XL 0.66E)||0.03 - 0.05||5.8 - 9.6 oz||7|
|β-cyfluthrin (Baythroid XL 1)||0.0155 - 0.022||2.1 - 2.8 oz||7|
|γ-cyhalothrin (Declare 1.25)||0.0125 - 0.015||1.28 - 1.54 oz||7|
|λ-cyhalothrin (Karate 2.08, Warrior II)||0.025 - 0.030||1.6 - 1.9 oz||7|
|Z-cypermethrin (Mustang Max 0.8E)||0.020 - 0.025||3.2 - 4 oz||7|
- Grasshoppers are primarily a problem in reduced-tilled fields because tillage can destroy egg masses.
- A beneficial cultural practice is to mow ditch banks and field edges before crop emergence to minimize the optimal habitat for grasshoppers before they relocate into cropping fields.
- For more information see http://www.utcrops.com/soybean/soybean_insects/SoybeanGrasshop.htm.