Plant volatiles guide the new pest Dichelops furcatus to feed on corn seedlings.

BACKGROUND: Recently, in temperate and neotropical regions of South America the generalist stink bug Dichelops furcatus (Hemiptera: Pentatomidae) became a new pest of corn (Zea mays) seedlings. Implementation of no-tillage cultivation system left organic matter covering the soil, which shelters adults of stink bugs during winter. In spring, corn is sowed under soybean stubble and D. furcatus adults start to feed on seedlings. To determine corn-derived volatile organic compounds (VOCs) that attract this stink bug species, we evaluated stink bug preferences from two corn hybrids with contrast germplasm backgrounds, a temperate and a tropical hybrid. RESULTS: Stink bugs preferred to feed on temperate seedlings rather than on the tropical ones. GC-MS and PCA analysis of VOCs suggested that hybrids emitted contrasting blends. Linalool represented 68% of total VOCs emitted from temperate corn, while in the tropical hybrid this compound represented 48%. Olfactometer experiments demonstrated that linalool was attractive to stink bugs. However, 2 h of D. furcatus attack induced emission of 14 additional VOCs in temperate seedlings, and olfactometer bioassay and blend of VOCs emission suggested that perceived volatiles by stink bugs induced feeding avoidance. The increment of VOCs emission was associated with the induction of JA, JA-Ile, ABA, and IAA, and decreasing of SA concentrations. CONCLUSION: This is the first time showing a complete profile of defensive phytohormones induced by stink bugs feeding on corn, and further demonstrating that a blend of corn seedling-associated VOCs, mainly composed by linalool, modulates D. furcatus adults' behavior and feeding preferences. © 2021 Society of Chemical Industry.

Virulence of Metarhizium brunneum (Ascomycota: Hypocreales) Strains Against Stinkbugs Euschistus heros and Dichelops furcatus (Hemiptera: Pentatomidae).

Three strains of fungi belonging to the genus Metarhizium Sorokin (ARSEF 4556, ARSEF 3297, native strain) were assayed against adults and nymphs of the Neotropical brown stinkbug Euschistus heros (F.) and the green-belly stinkbug Dichelops furcatus (F.). The most virulent strain, ARSEF 4556, caused over 90% mortality. The average survival time of the second and fifth instar nymphs and adults following immersion in 1 × 108 conidia ml-1 was 4.8, 5.7, and 5.2 d, respectively. The second instar nymphs were more susceptible than the adults. The LC50 values and median survival times for second instar and adult E. heros were 1.6 × 107 and 3.1 × 107 conidia ml-1 and 6 and 8 d, respectively. Eggs of E. heros and the closely related stinkbug, D. furcatus, were highly susceptible to ARSEF 4556 with the mean mortality of eggs immersed in 1 × 108 conidia ml-1 being 77.4% and 89.7%, respectively. The strain 3297 showed also good aptitudes for stinkbugs control with mortalities higher than 80% against nymphs and adults and eggs mortalities of 75.5% for E. heros and 79.6% for D. furcatus. This study has shown that it is possible to have a two-pronged control strategy, targeting adults and to reduce oviposition and targeting egg clusters to prevent emergence and dispersal of nymphs. Besides early instars of nymphs have been shown to be more susceptible to the fungal strains than late instars and adults.

Injúrias de quatro espécies de percevejos pentatomídeos em plântulas de milho / Injuries of four species of stink bugs to corn seedlings

Neste estudo, foram caracterizadas as injúrias causadas pelos percevejos Dichelops furcatus (F.), Nezara viridula (L.) e Euschistus heros (F.), em comparação com D. melacanthus (Dallas), em plântulas de milho (Zea mays L.). O experimento foi realizado em vasos, em ambiente de telado, em delineamento inteiramente casualizado, com cinco tratamentos (infestação com percevejos de quatro espécies e testemunha, sem infestação) em oito repetições. Na fase vegetativa do milho (estádio V1 até V3), D. melacanthus, na densidade de um adulto/planta, provocou redução na altura, no número de folhas expandidas, na massa seca das raízes e provocou injúrias no cartucho e/ou enrolamento das folhas centrais da planta. D. furcatus, E. heros e N. viridula causaram injúrias, porém, em intensidades diferentes. As injúrias causadas por D. furcatus e N. viridula foram semelhantes na forma e intensidade às de D. melacanthus e as injúrias causadas por E. heros foram menos intensas que as dos demais percevejos estudados.

Injuries caused by the stink bugs Dichelops furcatus (F.), Nezara viridula (L.) and Euschistus heros (F.), compared with Dichelops melacanthus (Dallas), to corn (Zea mays L.) seedlings were studied. The experiment was conducted in a greenhouse in a completely randomized design with five treatments (four species of stink bugs and control, without infestation) using eight replications. In the vegetative stage (V1 to V3) D. melacanthus, at the density of one adult/plant, caused reduction in height, in the number of expanded leaves, in root dry matter, and caused injuries and winding of the central leaves. D. furcatus, E. heros and N. viridula caused injuries, but at different intensities. Injuries caused by D. furcatus and N. viridula were similar in intensity to those by D. melacanthus and the injuries caused by E. heros were less intense than those of the other species.