Lenita J. Oliveira

Detrimental effect of rutin on Anticarsia gemmatalis

O efeito de dieta contendo rutina (quercetina 3-O-rutinosideo) no comportamento e na nutricao do principal desfolhador da soja, Anticarsia gemmatalis Hubner (Lep.: Noctuidae) foi avaliado do terceiro instar ate a formacao da pupa. Rutina e um dos flavonois glicosidicos identificados em folhas da soja selvagem PI 227687. O peso das lagartas e o consumo decresceram com o aumento na concentracao de rutina na dieta. Houve interacao entre o tempo de alimentacao e a dieta no crescimento do inseto; lagartas alimentadas com dieta pura, cujo tempo de alimentacao prolongou-se, originaram pupas mais pesadas. O peso das pupas alimentadas com dieta contendo rutina permaneceu estavel, apesar do maior tempo de alimentacao. Rutina afetou negativamente o crescimento do inseto, nao somente pela inibicao alimentar, mas tambem em consequencia de eventos pos-ingestivos, ja que depois do ajuste do peso de pupa pelo consumo (covariavel), o efeito do tratamento permaneceu significativo. Assim, o efeito negativo de rutina em A. gemmatalis resulta de efeitos pre-ingestivos, indicados pela reducao no consumo, e pos-ingestivos, indicados por baixas conversoes do alimento ingerido em biomassa e assimilacao de alimentos.

Efeito do manejo de solo na população e nos danos de corós em soja

Foram realizados varios experimentos para avaliar o efeito de diferentes sistemas de manejo de solo na populacao de coros (Phyllophaga cuyabana Moser), e seus danos em soja, em areas de plantio direto e de preparo convencional do solo (preparo primario com arado de discos e uma gradagem niveladora). Varios implementos utilizados no preparo primario de solo, como arado de aivecas, arado de discos, escarificador e grade aradora tambem foram avaliados. A flutuacao populacional de coros e a intensidade de dano causado por eles foram similares nas areas de plantio direto e de preparo convencional. Os implementos de preparo primario do solo afetaram a populacao de coros diferentemente, dependendo da epoca em que o preparo de solo foi executado. A mortalidade larval pode ser atribuida mais a exposicao a fatores adversos logo apos o preparo, do que a mudancas nas condicoes do solo. A reducao na populacao de coros foi mais evidente nas parcelas preparadas com implementos mais pesados, como arado de aivecas. O manejo de solo pode ser um componente dentro do manejo de pragas do solo em soja, porem sua utilizacao nao pode ser generalizada.

Aggregation behavior of Phyllophaga cuyabana (Moser) (Coleoptera: Melolonthidae): relationships between sites chosen for mating and offspring distribution

The aggregation behavior of Phyllophaga cuyabana (Moser) was studied and the hypothesis that the cluster distribution of larvae of this pest into the soil is related to the sites where females from the previous generation had aggregated for mating was investigated. Field observations and greenhouse experiments carried out in Londrina County, State of Parana, South Brazil, indicated that: a) during flight, adult females of P. cuyabana select plants, which are more conspicuous for landing and/or attracting males; b) tall plants, nearby soybean fields, might be preferred because female adults do not move far from the mating sites before digging themselves into the soil to lay eggs; c) high density of eggs and larvae occurs close to the adult aggregation sites. There is a negative correlation between larval density in the soil and distance from adult aggregation sites.

Survivorship, larval development and pupal weight of Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae) feeding on potential leguminous host plants

In Brazil, the velvetbean caterpillar Anticarsia gemmatalis Hubner is multivoltine. Several overlapping generations occur with larvae feeding on alternate host plants in areas of warmer temperatures. In this study, the survivorship and development of A. gemmatalis larvae were evaluated on 17 species of cultivated and non-cultivated legumes in laboratory conditions. Larval survivorship on summer legumes varied from 91% on soybean to 5% on showy crotalaria and on velvetbean. On winter legumes, survivorship of A. gemmatalis larvae varied from 90% on white lupin to 25% on common vetch. All larvae fed on yellow lupin died during early development. On non-cultivated summer legumes, 70% of the larvae on Indigofera suffruticosa Millsp., and 55% on I. truxillensis H.B.K. and I. endecaphylla Jacq. reached the pupal stage. Based on survivorship, larval development and pupal weight, the most suitable legumes for A. gemmatalis were soybean, pigeon pea, and white lupin.

Feeding and oviposition preference of Phyllophaga cuyabana (Moser) (Coleoptera: Melolonthidae) on several crops

Laboratory and greenhouse experiments were carried out to study food and oviposition preference by Phyllophaga cuyabana (Moser) on different plant species as Cajanus cajan L. (pigeon pea), Crotalaria juncea L. (sun hemp), Crotalaria spectabilis Roth (showy crotalaria), Crotalaria ochroleuca G. Don (slenderleaf rattlebox), Glycine max [L.] Merrill (soybean), Gossypium hirsutum L. (cotton), Helianthus annuus L. (sunflower), Stizolobium aterrimum [Mucuna aterrima] Piper Tracey (velvetbean) and Zea mays L. (mayze). In no-choice experiments, the number of eggs layed in sunflower, C. juncea and soybean was larger compared to cotton. Despite the fact that the adults did not discriminate among plants, in dual-choice test, the proportion of eggs layed and leaf consumption by P. cuyabana adults in soybean were significantly higher than in C. spectabilis. The larval distribution in the soil was at random in multiple-choice, without any trend of preference, but in dual-choice, when soybean was the control, larvae always preferred to feed on its roots. P. cuyabana adults had preference for more suitable hosts and that could stand their offspring survival. This behaviour can be usefully exploited in an integrated management program for this pest.

Seasonal and vertical distribution of Phyllophaga cuyabana (Moser)(Coleoptera: Melolonthidae) in the soil profile.

Phyllophaga cuyabana (Moser) temporal and vertical distribution patterns were evaluated in the soil profile, in order to subsidize methodology for population sampling, aiming at its management. In insect surveys carried out during three years, in Boa Esperança County, State of Parana, Brazil, Phyllophaga cuyabana was univoltine, with little overlap of the larval stages. Population peaked during December-February, but declined during the colder months, when larvae were in diapause. Different developmental stages exploited distinct soil depths. Eggs and early first instars tended to concentrate between 5 cm and 10 cm deep, but they spread more uniformly through the soil profile, reaching depths up to 30 cm, as they developed. Adults and eggs occurred in the spring (October to December) when active larvae also started to be observed; feeding larvae occurred up to late-April between 0 to 15 cm deep. Diapausing larvae and pupae were observed from early fall to early spring, mostly from 15 cm to 30 cm deep. Throughout the year, the number of insects in the soil (up to 40 cm deep) showed a positive functional relationship with air temperature and evapotranspiration. The relationship of percent distribution of larvae in the soil profile and soil temperature, however, was positive only above 10 cm. To estimate the insect population from November to April, samples can be collected until 20 cm deep; from May to October, however, samplings should be deeper, up to 30 cm.