MECHANISMS OF HOPPERBURN: An Overview of Insect Taxonomy, Behavior, and Physiology

Abstract

Hopperburn is a non-contagious disease of plants caused by the direct feeding damage of certain leafhoppers and planthoppers. Although long studied, especially with Empoasca spp. leafhoppers (Cicadellidae: Typhlocybinae), the mechanisms underlying hopperburn have only recently been elucidated. Hopperburn is caused by a dynamic interaction between complex insect feeding stimuli (termed hopperburn initiation) and complex plant responses (termed the hopperburn cascade). Herein we review the nature of the feeding stimuli in hopperburn initiation, especially for Empoasca spp., which we also compare with the planthopper Nilaparvata lugens. Contrary to previous reports, Empoasca hopperburn is not caused solely by toxic saliva. Instead, it is caused by a plant wound response triggered by a unique type of stylet movement, which is then exacerbated by saliva. Electrical penetration graph monitoring has revealed that all Empoasca spp. are cell rupture feeders, not sheath feeders, and that certain tactics of that feeding strategy are more damaging than others. Measuring the proportions of the most damaging feeding led to development of a resistance index, the Stylet Penetration Index, which can predict hopperburn severity in different plants or under different environmental conditions and can supplement or replace traditional, field-based resistance indices.

Empoasca leafhoppers attack wild tobacco plants in a jasmonate-dependent manner and identify jasmonate mutants in natural populations

“…(So far, we have not been able to identify the Empoasca species used in this study because the genus is poorly understood (18). We assume that the species is Empoasca fabae, but further corroboration is required to ascertain the actual species.…”

“…Leafhoppers of the genus Empoasca are hemipterans (family Cicadellidae) that feed on phloem and cell contents of a broad range of host plants (16,17). During feeding, the leafhoppers may induce "hopper burn" in the plant tissue, damage that is characterized by the yellowing of the tissue around the feeding site (18). Empoasca leafhoppers can also vector viruses, bacteria, and fungi and transmit them efficiently to plants as a consequence of their ingestion-egestion feeding behavior (18).…”

“…During feeding, the leafhoppers may induce "hopper burn" in the plant tissue, damage that is characterized by the yellowing of the tissue around the feeding site (18). Empoasca leafhoppers can also vector viruses, bacteria, and fungi and transmit them efficiently to plants as a consequence of their ingestion-egestion feeding behavior (18). For example, cell wall-lacking bacteria of the species Candidatus Phytoplasma (hereafter, Ca.…”

Viral infection induces different detoxification enzyme activities in insecticide-resistant and -susceptible brown planthopper <i>Nilaparvata lugens</i> strains

“…1) Large populations cause the death of rice plants in concentric circular patterns in rice fields (commonly called "hopper burn") and can induce plant mortality across an entire rice field. [1][2][3] BPH is able to migrate over long distances [3][4][5] and is well-distributed across Asia. 6) BPH populations are controlled mainly by insecticides, but the unregulated use of insecticides in many areas have resulted in insecticide tolerance and the outbreak of BPH in tropical Asian countries, 7) including frequent outbreaks in the 1960s and 1970s after the Green Revolution.…”

Salivary gland structure of Ctenarytaina eucalypti (MASKELL, 1890) (Hemiptera) and phloem exudate in Eucalyptus globulus LABILLARDIÈRE, 1799 (Myrtaceae)

“…They secrete both gel-like and watery saliva: the gel-like saliva contains lipoproteins, phospholipids and conjugated carbohydrates, whereas the watery saliva consists of various enzymes (MILES 1999, BACKUS et al 2005. Immunolocalization techniques indicate that salivary proteins in the principal and accessory glands of Sternorrhyncha (e.g.…”