The stink bug Dichelops furcatus: a new pest of corn that emerges from soybean stubble.

Over the last decades, Argentine and Brazilian farmers have adopted no-tillage cultivation systems and multiple cropping, which have decreased the abundance of traditional pests, such as Nezara viridula, and favored the development of some stink bugs of secondary importance, like Dichelops furcatus, D. melacanthus and Euschistus heros. No-till farming leaves the soil undisturbed, to mitigate erosion, and sufficient crop residue on the field, which is used by D. furcatus as a shelter under unfavorable conditions, and as a shelter against insecticides. Moreover, implementing multiple cropping systems increases crop rotation from soybean to corn, and places overwintering adults of D. furcatus in contact with corn seedlings in spring. Attacks of this stink bug species produce deformation and abortion of corn seedlings, resulting in up to 50% corn yield reduction. The increasing abundance of D. furcatus intensifies the damage on developing pods and seeds of soybean, becoming a primary pest of soybean, and a new pest of corn. Here we summarize the current knowledge about D. furcatus, its biology, life cycle, and geographical distribution pattern in South America. Additionally, we describe the general causes and consequences of D. furcatus as a new pest of corn that emerges from crop stubble. Then, we provide an overview of the chemical control, natural enemies, and possible agronomical practices to improve sustainable crop production methods to control this pest. © 2022 Society of Chemical Industry.

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.

Digestive activity and organic compounds of Nezara viridula watery saliva induce defensive soybean seed responses.

The stink bug Nezara viridula is one of the most threatening pests for agriculture in North and South America, and its oral secretion may be responsible for the damage it causes in soybean (Glycine max) crop. The high level of injury to seeds caused by pentatomids is related to their feeding behavior, morphology of mouth parts, and saliva, though information on the specific composition of the oral secretion is scarce. Field studies were conducted to evaluate the biochemical damage produced by herbivory to developing soybean seeds. We measured metabolites and proteins to profile the insect saliva in order to understand the dynamics of soybean-herbivore interactions. We describe the mouth parts of N. viridula and the presence of metabolites, proteins and active enzymes in the watery saliva that could be involved in seed cell wall modification, thus triggering plant defenses against herbivory. We did not detect proteins from bacteria, yeasts, or soybean in the oral secretion after feeding. These results suggest that the digestive activity and organic compounds of watery saliva may elicit a plant self-protection response. This study adds to our understanding of stink bug saliva plasticity and its role in the struggle against soybean defenses.