EFFECT OF STINK BUGS ON YIELD, SEED DAMAGE AND AGRONOMIC TRAITS OF SOYBEANS (GLYCINE-MAX)

To evaluate the stability of the trait resistance to insects, under di fferent dates of planting, three resistant and three susceptible genot ypes were tested in an experiment set up at the experimental station o f the Centro Nacional de Pesquisa de Soja (Soybean National Research C enter), Embrapa, in Londrina, PR, Brazil. The study consisted of soybe ans planted at six different dates, starting on 18 October and spaced ca. 15 days from each other. At harvesting, height of plants, height o f first pod, indexes of lodging and leaf area retention were evaluated . Seeds of three meters of row were harvested and of another three met ers were harvested one week later. Results indicated that delay of har vesting did not significantly increase stink bug damage to seeds. The best seed quality were observed on soybeans planted between November 1 5 and December 15. The highest and lowest yields were obtained on soyb eans planted on November 30 and October 18, respectively. Early maturi ty genotypes showed lower yields when planted up to November 15, the m edium group had the lowest yield when planted at October 18, while lat e genotypes yielded less when planted at October 18 and at both Decemb er dates. An interaction between genotypes and dates was observed both for yield and quality of seeds, indicating the need of identifying so urces of resistance to stink hugs with more stable behavior.