Pest description, crop damage and life history Grasshoppers are rarely a problem in snap beans. Grasshoppers eat irregular holes in leaf tissue and can defoliate plants in high numbers, especially when swarming. Damage tends to be greatest on the edges of fields near pasture areas or roadsides. When wild grasses and other plants become dry, grasshoppers migrate to irrigated croplands.
Predators and parasites of grasshoppers are numerous and at times play an important role in maintaining grasshopper populations at low densities. Unfortunately, under favorable weather conditions, population increases may overwhelm the natural controls, and grasshoppers may reach high densities.
A biological control that has been tested extensively and is commercially available is the protozoan Nosema locustae (Nolo Bait). Nolo Bait has a REI of 4 hr and acts slowly. It may not reduce grasshopper populations to noneconomic numbers the year of application. It may be more effective applied in non-cultivated areas such as borders and pasture where grasshoppers breed. Also, the timing of application is important. Two other organisms, the fungal pathogens Beauveria bassiana and Entomophus grylli, are being tested as commercial biological control agents.
Disturbance or maturation of crops may cause grasshoppers to disperse. Take care not to cut vegetation or till soil of fields harboring grasshoppers if susceptible crops are being grown nearby. Large blocks of crops with less crop edge tend to be damaged less than smaller blocks.
Management-chemical control: HOME USE
Follow information on the label about the timing and cutoff date for spraying the particular vegetable you are treating. Spray damaged plants and any grass or weeds surrounding the vegetable garden when young hoppers or winged adults are seen.
- azadirachtin (neem oil)-Some formulations are OMRI-listed.
- bifenthrin (often as a mix with zeta-cypermethrin)
- insecticidal soap-Some formulations are OMRI-listed for organic use.
- pyrethrins (often combined with other ingredients)-Some formulations are OMRI-listed for organic use.
Management-chemical control: COMMERCIAL USE
- alpha-cypermethrin (Fastac EC) at 0.02 to 0.025 lb ai/a. PHI 1 day. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.075 lb ai/a per season.
- bifenthrin (Sniper) at 0.025 to 0.1 lb ai/a. PHI 3 days. REI 12 hr. Do not exceed 0.2 lb ai/a per year.
- bifenthrin/imidacloprid (Brigadier) at 0.06 to 0.0875 lb ai/a. PHI 7 days. REI 12 hr. Do not exceed 0.13 lb ai/a imidacloprid and 0.13 lb ai/a bifenthrin per season. Retreatment interval 7 days.
- bifenthrin/zeta-cypermethrin (Hero EW) at 0.04 to 0.1 lb ai/a. PHI 3 days. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.266 lb/a per season.
- chlorantraniliprole (Coragen) at 0.026 to 0.065 lb ai/a. PHI 1 day. REI 4 hr. Limit 4 treatments. Retreatment interval 3 days. do not exceed 0.6 lb ai/a per season.
- chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.06 to 0.1 lb ai/a. PHI 7 days. REI 24 hr. Retreatment interval 5 days. Do not exceed a total of 31.0 fl oz of Besiege or 0.12 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per growing season. Do not graze livestock or harvest vines for forage or hay.
- dimethoate (Dimethoate 4E) at 0.25 to 0.5 lb ai/a. PHI 0 days. REI 48 hr. Retreatment interval 14 days. Do not exceed 1.0 lb/a per year. Do not feed treated vines.
- esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/a. Apply reduced rates (0.02 to 0.03 lb ai/a) to first and second instar. PHI 3 days. REI 12 hr. Do not exceed 0.2 lb ai/a per season. Do not allow livestock to graze treated fields. Do not harvest treated bean vines for livestock forage, fodder, or hay.
- gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb/a. PHI 7 days. REI 24 hr. Retreatment interval 5 days. Do not graze. Do not exceed 0.06 lb ai/a per year. Do not graze livestock in treated areas or harvest vines for forage or hay.
- lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/a. PHI 7 days. REI 24 hr. Retreatment interval 5 days. Do not exceed 0.12 lb ai/a per year. Do not graze livestock in treated areas or harvest vines for forage or hay.
- malathion (Agri Solutions Malathion 5) at 1 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not graze or feed foliage to livestock.