There are pro and con arguments to host specificity. Generally, it would be desirable to have an organism that was only active against one or more plant parasitic nematodes. This would reduce the chance of killing nontarget beneficial organisms. However, if only one of several damaging organisms is killed by a particular agent, costs may increase if more than one agent must be used.
Killing the target organism is considered more desirable than merely altering behavior or other sublethal effects from which recovery might be possible.
The ability to work with an organism experimentally in the laboratory is a plus and hastens developmental research.
Many candidate organisms have proven difficult to produce on artificial media. If an organism must be reared on its host, this raises the question of how it can be utilized without accidentally introducing the host into a new environment. Organisms which can be reared in fermentation facilities have been the most attractive to commercial entities.
Producing a formulated product that can be applied with equipment currently in use by growers will assure easier acceptance. Considerations would include liquids with a particle size that will not clog standard sprayer screens (e.g. 50-100 mesh/inch), be filtered out in drip irrigation filters, or clog drip applicators, and will stay suspended without agitation. This at first may not seem difficult but many biological insectides marketed as "liquids" are prepared from fermentation media. Some components of the media are initially themselves solids or powders which if not digested in the process must be small enough to not clog application equipment. It is not uncommon for a "liquid" to be prepared from a spray dried fermentation product which has been ground into a powder and then mixed with water or oil. The viscosity of an oil based liquid can change dramatically with temperature and cause problems with calibrating equipment. Powders should be prepared to disperse readily in water. Non-dusty granules similar to the size, weight, and cosistency of commercial fertilizers are a practical consideration.
There are mixed feelings with respect to the desirability of a biological control agent to become established, recycle and provide control for an extended period. This would certainly appear to be desirable from the standpoint of minimizing the need for other methods of control. However, there may be less incentive for commercialization of a product that only needs to be applied a single time.
One should not assume that just because a product is natural or biological that it is safe to use in all situations. For example, some natural insecticides such as pyrethrins can be harmful to fish. Many biological insecticides contain proteins and other substances to which some could become allergic, as is possible with products containing shellfish.
If a product is to be marketed through current agricultural channels, a one-year shelf-life is a minimum requirement. HIgh temperature stability is also desirable as desert agricultural warehouses may commonly exceed 110F during summer months. This is particularly a concern for fermentation products containing living organisms. Bloating or exploding containers quickly discourage otherwise willing distributors.