Heteroptera as vectors of plant pathogens

The ability of piercing-sucking insects to transmit plant disease is closely linked to feeding mode and target tissue. The true bugs (Heteroptera) are generally considered to be of minimal importance as vectors of plant pathogens, although they share similar feeding behaviors with homopterans. Modes of feeding in Heteroptera include "lacerate-and-flush", intracellular penetration to vascular tissue, and an osmotic pump mechanism to acquire cell contents without penetrating the cell membrane. The relationship between heteropteran taxonomy, feeding mode, and the type of pathogens transmitted is explored through a literature survey of feeding behavior and vectoring capability. Transmission by true bugs of fungal pathogens, bacteria, viruses, phytoplasmas, and trypanosomatid flagellatesis summarized; no records exist of bugs transmitting spiroplasmas. Trypanosomatid flagellates of plants appear to be harbored or transmitted exclusively by Pentatomomorpha (Lygaeioidea, Coreoidea, Pentatomoidea, and Pyrrhocoroidea). Bacterial and fungal transmission occurs among families representing both infraorders of phytophagous Heteroptera, but Miridae (Cimicomorpha) are most closely associated with bacteria, whereas Pentatomidae and Coreidae (Pentatomomorpha) predominate in transmission of fungi. Few cases of transmission of phytoplasmas and viruses are documented, but Cimicomorpha (traditionally categorized as destructive lacerate-and-flush feeders) are represented more frequently than expected, considering the tissue specificity of these pathogens. Literature emphasis on the exclusive or predominant role of homopterans as disease vectors may discourage initial investigations of true bugs; based on the results presented here, the necessity of including heteropterans in any survey of potential plant disease vectors is clear.