ARE THE LARVAE OF Spodoptera cosmioides ABLE TO DETECT VOLATILES ORGANIC COMPOUNDS FROM DIFFERENT HOST PLANT SPECIES?

HILL JORGE GUILLERMO; PAEZ JEREZ, PAULA; FERNANDEZ, PATRICIA C.; VERA MARIA TERESA

Buenos Aires

Congreso; 6TH CONGRESS OF THE LATIN AMERICAN ASSOCIATION OF CHEMICAL ECOLOGY; 2021

The arrival of genetically modified soybean (Glycine max) cultivars with both insecticide action (Bt-toxins) and herbicide-tolerant traits have increased the production and yield of soybean in South America. Spodoptera cosmioides (Lepidoptera: Noctuidae) is a Bt-tolerant polyphagous species frequently associated with host plants from the Amaranthus genus with reported herbicide-resistant populations. The high capability to survive in Bt-soybean cultivars turned S. cosmioides into a serious pest. Our goal was to determine if S. cosmioides larvae are able to respond to volatile organic compounds (VOCs) released by two Amaranthus species, A. hybridus (native) and A. palmeri (exotic), and two commercial soybean varieties (one expressing the Cry1Ac protein and other non-Bt soybean, being both resistant to glyphosate). We used a dual-election air-stationary olfactometer, which consists of a glass tube (50 x 4 cm; length:diameter). Fourth and fifth-instar starved (24 h) larvae (35 per treatment) were allowed to crawl from the middle of the olfactometer to its ends. Larvae were reared on an artificial diet. The following treatments (emitted VOCs) were tested: Bt-soybean leaf vs. air (control); A. hybridus branch (containing from four to six leaves) vs. air (control); Bt-soybean vs. non-Bt soybean; A. hybridus vs. A. palmeri; non-Bt soybean vs. A. palmeri; Bt-soybean vs. A. palmeri; and Bt-soybean leaf with pods (reproductive stage) vs. A. palmeri. Larvae responded to VOCs from both host plants when Amaranthus and soybean species were compared against air. Spodoptera cosmioides did not show any preference between neither the soybean varieties nor the Amaranthus species. However, significantly more larvae moved to the arm containing A. palmeri when this was offered vs. the soybean varieties. Our findings demonstrated a potential host preference of S. cosmioides by Amaranthus species; therefore, the presence of these weeds should be considered when planning S. cosmioides management strategies in soybean.