Does father know best? The case of Spodoptera cosmioides (Lepidoptera: Noctuidae)

HILL, JORGE GUILLERMO; PAEZ JEREZ, PAULA; HERRERA LINARES, FACUNDO; FERNÁNDEZ PATRICIA CARINA; VERA MARIA TERESA

La Plata

Congreso; XI Congreso Argentino y XII Congreso Latinoamericano de Entomología; 2022

UNIVERSIDAD NACIONAL DE LA PLATA, CEPAVE-CONICET, FELA, MUSEO DE LA PLATA, SEA

The black armyworm Spodoptera cosmioides is a relevant pest in many soybean agroecosystems of South America. Like its congeners, this is a polyphagous species that is able to attack 126 plants from 40 different families. In the soybean fields of Argentina, farmers claimed that S. cosmioides is commonly associated with difficult to control and herbicide-resistant weeds belonging to Amaranthus genus. However, this hypothesis has not yet found solid bases. In this work, we tested if S. cosmioides males are differentially attracted to female sex pheromone when this stimulus is perceived in Bt and non-Bt soybean fields with different Amaranthus infestation levels. We used synthetic sex pheromone traps for capturing S. cosmioides adult males. Traps were hung at 1.5 m in soybean circular plots (radius = 15 m) with three Amaranthus infestation levels: low (0-14%; weed coverage), moderate (15-39%) and high (≥40%). We used five traps per infestation level and soybean variety. Traps were weekly monitored from March 29th 2022 to May 3rd 2022 covering soybean reproductive stages. The number of S. cosmioides adults captured was fitted using a generalized linear model with a Poisson distribution. We used the infestation level plus the soybean variety as factors. The interaction between factors was also analyzed. The number of males was significantly affected by Amaranhus infestation level, but not by soybean variety. No interaction between factors was found. Moths were mostly captured in soybean plots with a low Amaranthus infestation level. The lowest capture was recorded in those plots with moderate level of Amaranthus. Our findings show that when S. cosmioides males are in the search of females, the adults may prefer soybean fields where Amaranthus weeds are less abundant. This may result from volatiles released by Amaranthus species which may interfere with those released by crop plants modulating the reproductive behavior of moths. Further studies confirming the results obtained in a single campaign will contribute to evaluate an integrated pest management (IPM) that includes both allomones and pheromone-based strategies and an efficient weed management.