Vitex agnus-castus is a Preferred Host Plant for Hyalesthes obsoletus

Abstract

Hyalesthes obsoletus Signoret (Homoptera: Cixiidae) is a polyphagous planthopper that transmits stolbur phytoplasma (a causative agent of "yellows" disease) to various weeds, members of the Solanaceae, and wine grapes (Vitis vinifera L.) in Europe and the Middle East. Planthoppers were collected by hand vacuuming eight native plant species. Vitex agnus-castus L., a shrub in the Verbenaceae, hosted the largest number of H. obsoletus, although Olea europaea L. also served as a host for adults. Using a Y-olfactometer, we compared the planthoppers relative preference for V. agnus-castus, Convolvulus arvensis, and V. vinifera. V. agnus-castus was more attractive to both male and female H. obsoletus than the other plants. H. obsoletus antennal response was stronger to volatiles collected from V. agnuscastus than from Cabernet Sauvignon variety of V. vinifera. To determine if V. agnus-castus would serve as a reservoir for the pathogen, H. obsoletus were collected from leaf and stem samples of native V. agnus-castus, and were tested by polymerase chain reaction (PCR) for the presence of phytoplasma DNA. While 14% and 25% (2003 and 2004, respectively) of the insects tested positive for phytoplasma DNA, none of the plant samples tested positive. To determine if V. agnus-castus could serve as a host plant for the development of the planthopper, we placed emergence cages beneath field shrubs and enclosed wild-caught H. obsoletus in a cage with a potted young shrub. We found adult H. obsoletus in the emergence cases and planthopper nymphs in the soil of the potted plant. We concluded that V. agnus-castus is attractive to H. obsoletus, which seems to be refractory to phytoplasma infections and warrants further testing as a trap plant near vineyards.

Opportunities for Napier Grass (Pennisetum purpureum) Improvement Using Molecular Genetics

“…The disease symptoms include yellowing of foliar material, smaller leaves, a proliferation of tillers, yellow to purple streaking and shortening of internodes to the extent that clumps appear severely stunted, resulting in a low biomass yield and eventual death of the plant, although this only occurs after cutting or grazing the grass [118]. However, the level of expression of the symptoms in phytoplasma-infected plants partly depends on the virulence of the strain, strain interference and phytoplasma concentration [122] and the abundance of insect vectors and phytoplasma-infested host plants [123]. The primary mode of transmission of the disease is by vegetative propagation of infected planting material or by phloem-feeding insects belonging to the families Cicadellidae (leafhoppers), Delphacidae (planthoppers) and some psyllids (Psylloidea) [124,125].…”

Mating Behavior of Hyalesthes obsoletus (Hemiptera: Cixiidae)

“…As the spread of the disease through European vine areas is more and more alarming (Johannesen et al 2008), H. obsoletus is considered an important threat for viticulture and many studies have been undertaken to provide knowledge for supporting sustainable control practices, dealing primarily with the planthopperÕs biology, ecology, and transmission ability (e.g., Bressan et al 2007, Lessio et al 2007, Johannesen et al 2008, Kaul et al 2009). Recently, the role of olfactory cues in host plant selection has been investigated (Sharon et al 2005, Riolo et al 2009). However, the knowledge of intraspeciÞc communication is still lacking.…”

Crepis foetida L.: New host plant of cixiid planthopper Hyalesthes obsoletus Signoret 1865 (Hemiptera: Cixiidae), vector of stolbur phytoplasma

“…U Evropi je pokazano da su biljke koje su izvori zaraze stolbur fitoplazmom vrste na kojima Hyalesthes obsoletus kompletira svoje razviće: Convolvulus arvensis i Urtica dioica ili u južnoj Francuskoj Lavandula angustifolia. U Izraelu H. obsoletus kompletira ceo životni ciklus na Vitex agnus-castus, ali populacije koje izleću nisu zaražene fitoplazmom što znači da ova biljna vrsta nije istovremeno i rezervoar biljka (Sharon, 2005).…”

“…Dosadašnjim istraživanjima je utvrđeno da su širom južne Evrope i u Nemačkoj glavne biljke domaćini, na kojima se odvija razviće larvi H. obsoletus, poponac (Convolvulus arvensis L.) i kopriva (Urtica dioica L.) (Langer i Maixner, 2004), dok je u južnoj Francuskoj to Lavandula angustifolia L. (Sforza, 1999), a u Izraelu Vitex agnus-castus L. (Sharon, 2005).…”