A need for disclosure of the identity of microorganisms, constituents, and application methods when reporting tests with microbe-based or pesticide-based products

Abstract

Plant growth-promoting microorganisms, biological control agents, pesticides, and a variety of stimulants to enhance plant performance are commonly tested and commercially applied worldwide on increasing scales each year (Bashan et al. 2014; Calvo et al. 2014; Lugtenberg and Kamilova 2009). In recent years, inoculation of plants with microorganisms to enhance productivity has become widespread, with more sophisticated and complex formulations and application methods. These formulations use a variety of application techniques, such as using natural and synthetic polymers or add more than one microorganism to the inoculants. These microbial consortia in inoculants may have over ten different microorganisms. Inoculants may have synthetic vitamins, plant hormones, and humic and fulvic acids. Other inoculants add different plant or algae or seaweed extracts, protein hydrolytes and amino acids as stimulants, as well as bulking materials, such as clays, minerals (vermiculite and perlite), talcum, or undisclosed soil fractions. Numerous adhesives, surfactants, stabilizing and dispersing materials, and preservatives to enhance survival and dispersal of the microorganisms are commonly added. The identity of these components in microbial formulations is often not disclosed in the product label. Specific details of application are usually explained by the manufacturer on the container label, but rarely in a formal publication. As product formulations change, performance of bacterial strains in the product may change. Hence, it might not be possible to objectively compare the effects of an inoculated microorganism in laboratory experiments with the effects of the same microbe in a commercial formulation. This results from some components in the formulations having synergistic bioactivities that are greater than a single strain of microorganism. As an example, the plant growth-promoting bacterium Azospirillum brasilense strain AZ39 is one of the most common Azospirillum strains used in Latin America. Yet, its performance significantly varies, depending on the specific formulation and the method of inoculation. Similar phenomenon occurs with rhizobia. Pesticides are commonly used in agriculture and are classified, according to the pest organism, in insecticides, fungicides, herbicides (weeds killers), nematocides, and rodenticides. The first three pesticides are those most used. Pesticides differ greatly for their chemical structures, and this result in a great variety of toxicological properties, most of them contain aromatic rings and some are chlorinated, just to mention a few chemical characteristics. Field rates depend on several factors including soil type (Bremner and Mulvaney 1976; Cervelli et al. 1976). Usually, pesticides are applied in formulations containing several other constituents often not disclosed in the product label, as mentioned above for the microbial inocula. These additives may include solvents, by-products of the target compounds, salts, chemical vehicles of the target compound, etc. Obviously toxicological studies of the target pesticide should also consider the effect of all other constituents; these effects may be synergic or antagonist with those by the target pesticide (Cervelli et al. 1976). * Yoav Bashan ybb0001@auburn.edu