Laboratory and greenhouse evaluation of insecticides for the control of Crocidosema sp. (Lepidoptera: Tortricidae) in soybean

Abstract

The Neotropical bud borer, Crocidosema aporema (Walsingham 1914) (Lepidoptera: Tortricidae), is a secondary pest of soybean in Brazil. Outbreaks have become more frequent in soybean fields following the development of practical resistance to Cry1Ac-expressing soybean derived from Bacillus thuringiensis Berliner (Bt). Recent molecular and morphological studies suggested that the species responsible for these outbreaks differ from C. aporema and may represent an undescribed species within the genus Crocidosema. Due to the resistance of Crocidosema sp. to Cry1Ac soybean and the increased use of insecticides, we conducted laboratory (diet-overlay and leaf bioassays) and greenhouse (artificial infestation) evaluations of selected insecticides against Crocidosema sp. In diet-overlay assays, L2 larvae were more susceptible to spinetoram, chlorantraniliprole, chlorfenapyr, indoxacarb, and thiodicarb than to flubendiamide and triflumuron. In accordance with diet-overlay results, insecticides with higher lethality achieved greater control in leaf bioassays (>77% control at 6 days after field-dose application) and greenhouse trials (>96% control). In contrast, flubendiamide- and triflumuron-based products were consistently less effective (<66% control) across both assay types. These findings provided practical guidance for optimizing chemical control of Crocidosema sp. in soybean production systems in Brazil and other South American countries.