Produtividade de genótipos de soja sob infestação da lagarta-da-soja e de percevejos / Yield of soybean genotypes under infestation of the velvetbean caterpillar and stink bugs

Three soybean experiments, one for each maturation group (early, semi-early, and medium), were installed in the field in Assis, State of São Paulo, during the 2003/2004 growing season to evaluate damage caused by Anticarsia gemmatalis (Hubn.) and by the soybean stink bug complex, Euschistus heros (F.), Piezodorus guildinii (West.), and Nezara viridula (L.). The experiments were installed again in 2004/2005, with the exception of the early cycle group. Defoliation caused by A. gemmatalis was evaluated by the percentage estimate of leaf area cut in the first year only, due to low caterpillar infestations in 2004/2005. All three stink bug species were present in both growing seasons. In 2003/2004, E. heros was predominant over the other two; in the following year, all three species occurred in similar numbers. The productivity criterion was adopted to evaluate stink bug damage. Based on both growing seasons and mainly considering productivity, a few lines could be selected within each maturation group for new field studies or for hybridizations in breeding programs. Among the early germplasm varieties, lines IAC 98-4540, IAC 98-4576, and IAC 98-3123 can be highlighted as promising; the latter also showed little defoliation by A. gemmatalis; in the semi-early group, IAC 98-4017, IAC 98-2663, and IAC 98-4250 were prominent, with steady productivity in both years; in the medium group, IAC 98-4136, the most productive, as well as IAC 98-4140 and IAC 98-4133, all with little defoliation, can be pointed out as promising.

Avaliação de Danos de Percevejos e de Desfolhadores em Genótipos de Soja de Ciclos Precoce, Semiprecoce e Médio / Evaluation of Damage in Soybean Genotypes of Three Maturity Groups Caused by Stink Bugs and Defoliators

The damage of stinkbugs and defoliators in soybean genotypes was evaluated, under field conditions, at Tarumã and Ribeirão Preto, State of São Paulo, Brazil. Three experiments, one for each of three maturity group, were carried out, in the 1997/98 and 1998/99 seasons. In Tarumã, infestations of Diabrotica speciosa (Germar) and Cerotoma sp. occurred in both seasons and Anticarsia gemmatalis Hubn. in the second; in Ribeirão Preto, this caterpillar occurred only in the second year. Only in the first year in Tarumã, stinkbug infestations [predominantly Piezodorus guildinii (West.)], fluctuated above the economic injury level (EIL); in Ribeirão Preto, the stinkbug infestations did not exceed the EIL. Defoliaton damage was estimated by the percentage of eaten leaf area (PAFC). Percentage of foliar retention (PRF) and yield were used to evaluate the stinkbug damage. Considering both years and both locations, among the early maturing genotypes (110 days), 'IAC-22' showed susceptibility to defoliators while 'IAC-17' confirmed its resistance to this group of pests as well as to stinkbugs. Among the genotypes of 120-day maturity group, IAC 93-3379 could be distinguished for the high yield, showing stability by this criteria. IAC 93-3275 and IAC 93-3237 presented low yield and high PAFC and PRF, mainly in Tarumã. Regarding the genotypes of 135-day maturity group, susceptibility to stinkbugs was observed in 'IAC Holambra-Stwart', 'IAC PL-1' and IAC 87-2048; however, this line showed high yield under low infestation. Also, IAC 78-2318, IAC 93-1789 and IAC 93-1796 presented the lowest PRF, indicating to be less susceptible to this disorder.

Avaliaram-se os danos causados por percevejos e por desfolhadores em genótipos de soja de ciclos precoce, semiprecoce e médio, em experimentos de campo instalados em Tarumã e Ribeirão Preto, SP, em 1997/98 e 1998/99. Em Tarumã, ocorreram os crisomelídeos Diabrotica speciosa (Germar) e Cerotoma sp. nos dois anos e Anticarsia gemmatalis Hubn. no segundo; em Ribeirão Preto, apenas no segundo ano ocorreu a lagarta. Com relação a percevejos, somente no primeiro ano em Tarumã as infestações [predominância de Piezodorus guildinii (West.)] flutuaram acima do nível de dano econômico; em Ribeirão Preto, essas infestações foram baixas. Os danos de desfolhadores foram avaliados pela estimativa da porcentagem de área foliar cortada e os de percevejos pela estimativa da porcentagem de retenção foliar e pela produtividade. Considerando-se os dois anos e as duas localidades, no grupo precoce, 'IAC-22' exibiu suscetibilidade a desfolhadores enquanto 'IAC-17' confirmou sua resistência a esse grupo de pragas e também a percevejos. Dentre o germoplasma de ciclo semiprecoce, a linhagem IAC 93-3379 destacou-se pela maior produtividade, demonstrando estabilidade para esse critério. As linhagens IAC 93-3275 e IAC 93-3237 apresentaram baixa produtividade e altos índices de desfolha e de retenção foliar, principalmente em Tarumã. Nos genótipos de ciclo médio, verificou-se suscetibilidade aos percevejos em 'IAC Holambra-Stwart', 'IAC PL-1' e IAC 87-2048, embora esta linhagem seja produtiva em condições de baixa infestação. Ainda neste grupo, as linhagens IAC 78-2318, IAC 93-1789 e IAC 93-1796 apresentaram os menores índices de retenção foliar, indicando serem pouco suscetíveis a essa anomalia.