We have received a number of calls on grasshoppers recently.
Permethrin (numerous trade names) is a good choice for vegetable crops because it is labeled for a wide variety of vegetables. However, keep in mind that hoppers can reinfest an area relatively quickly. Many times gardeners have not had an insecticide failure, but a reinfestation. Carbaryl (Sevin) can also be used for grasshopper control but can lead to mite outbreaks as it is very toxic to mite predators.
We often have gardeners who are interested in organic controls.
Nosema locustae, a protozoan, is the active ingredient in a number of products including Semaspore, NOLO Bait, HopperStopper and Grasshopper Attack. These products are selective and will affect only grasshoppers. This is a trait many gardeners find attractive. However, Nosema locustae products may not be as effective in garden situations as they would be under large-scale rangeland conditions due to potential reinfestations from outside the treated area. Also, these products have other potential disadvantages:- They are most effective against nymphal rather than adult grasshoppers. Also some grasshopper species are less susceptible than others.
– Kill can take 3 to 6 weeks after ingestion.
– These baits are perishable and should be kept refrigerated until use. Pay attention to the expiration date.
As mentioned above, reinfestations of uninfected grasshoppers can occur. These products are not effective against adults. Try to treat the nesting area when hoppers are small and populations are concentrated.
Nosema locustae products are allowed in certified organic crop production. Poultry including turkeys, guinea hens and chickens have also been used to help control grasshoppers.
Regardless of method used, the trick is to treat early before the population has matured. Young nymphal stages are much easier to control than adults and are also much less mobile.
(Ward Upham)
