Gláucia Cordeiro

Cerambycidae and other Coleoptera Associated with Branches Girdled by Oncideres saga Dalman (Coleoptera: Cerambycidae: Lamiinae: Onciderini)

Abstract Species of Oncideres Serville, often referred to as twig girdlers, girdle tree branches prior to oviposition to promote larval development. The behavior creates a unique niche that is utilized by other beetle species. The objective of this study was to compare emergence of insects from branches girdled by Oncideres saga Dalman in an intercropping system and a monoculture of Acacia mangium Willd. in the Atlantic Rainforest of Minas Gerais, Brazil. Twenty-four Coleoptera species emerged from the branches: 17 Cerambycidae; three Cleridae; and one individual each from Cantharidae, Cucujidae, Elateridae, and Trogossitidae. Although branches from the intercropping system yielded more individuals, branches from the monoculture had higher species richness, including almost all of the cerambycid species and all of the potential predators. The use of girdled twigs may confer a reproductive advantage to subsequent cerambycid colonists, which are probably attracted to the volatiles released by the girdled branch. Beetles belonging to other families may prey on the Cerambycidae dwelling inside the branches. Potential predators may be ecologically important, contributing to the natural biological control of O. saga. Collecting and burning the infested branches is the technique most extensively used to control the twig girdlers. However, this also destroys beneficial organisms as well as the subsequent colonists that depend upon these branches.

Active response of soybean to defoliator Anticarsia gemmatalis Hübner: strategies to overcome protease inhibitor production

Los mecanismos de resistencia endogenos de las plantas contra insectos herbivoros pueden permitir el desarrollo de estrategias alternativas para el control de plagas. La activacion de la via de las lipoxigenasas con la produccion de acido jasmonico, hormona responsable por la activacion de los genes inhibidores de proteasa, es una de las principales formas de defensa directa de las plantas contra los insectos. En el presente estudio, cultivares de soya en estadio V3, susceptibles y resistentes a insectos herbivoros fueron utilizadas para investigar las alteraciones en la actividad de LOX y la concentracion de PIs, en respuesta al ataque de orugas en cuarto y quinto instar de Anticarsia gemmatalis (Lepidoptera: Noctuidae) por 24 y 48 horas. La actividad de LOX (0,00 a 0,007 nm s-1/mg) y la concentracion de inhibidores de proteasa (60 a 125 mg de inhibidor de tripsina/ mg de proteina y 90 a 120 mg de inhibidor de tripsina/mg de proteina despues de 24 y 48 horas del ataque respectivamente) aumenta en respuesta a los danos ocasionados por A. gemmatalis. La actividad proteolitica disminuyo aproximadamente en 50% en los cultivares con diferentes grados de resistencia. El aumento del perfil enzimatico del intestino medio de A. gemmatalis puede estar relacionado al aumento de las enzimas tripticas para compensar la inhibicion de proteasas por sustancias entomotoxicas de los cultivares de soya.

Does mechanical damage on soybean induces the production of flavonoids

The response of plants to grazing includes the production of chemical defense compounds such as proteases inhibitors and secondary metabolites as flavonoids, which makes them less palatable to feeding and negatively affecting the physiology of insects. The aim of this study was to evaluate the phytochemical response of soybean cultivars (Glycine max (L.) Merrill) resistant (IAC-17, IAC-24) and susceptible (IAC-P1) to insects after mechanical damage. These cultivars were mechanically injured, and after 24 hours samples of these plants were analyzed by HPLC to identify and quantify flavonoids. The flavonoids daidzein, quercetin, and rutin were quantified, with the highest concentration of daidzin in soybean cultivars after mechanical damage. Rutin was biosynthesized by IAC-24. The cultivars IAC-PL1, IAC-17, and IAC-24 did not show a flavonoid response to mechanical damage. The soybean cultivars are not dependent on mechanical damage to produce flavonoids.

Protease inhibitory, insecticidal and deterrent effects of the trypsin-inhibitor benzamidine on the velvetbean caterpillar in soybean

The recognition of protease inhibitors with insecticidal activity is important as a basis for the development of mimetic peptides with potential use as biorational insecticides. We sprayed benzamidine on soybean plants and assessed whether this potent synthetic trypsin-inhibitor has protease inhibitory, insecticidal and deterrent effects on the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae). Activity of trypsin inhibition in soybean leaves was increased and total proteolytic activity in the midgut extract from larvae fed on these leaves was reduced by benzamidine. Different concentrations of benzamidine sprayed on the plant caused approximately 50 % of larval mortality, and larval choice and moth preference and oviposition were all negatively affected. Low concentrations of benzamidine increased mortality and hindered insect choice and oviposition as well as higher doses. Since many synthetic protease inhibitors are usually expensive, small doses of benzamidine may be effective to protect soybean against A. gemmatalis attack. Our results highlight the potential of synthetic protease inhibitors for insecticidal and deterrent purposes in insect pest management.

Sexual Dimorphism in the Twig Girdler Oncideres ocularis Thomson (Coleoptera: Cerambycidae)

ABSTRACT: The ability to distinguish gender among insects is essential to their study and management. The objective of this work was to find sexual dimorphism between males and females of Oncideres ocularis Thomson, 1868 based on their external morphology. Twenty-seven morphometric variables from the body of males and females of this beetle were measured. The length of body, elytra, length and width of the head, and length of antennae were found to have different dimensions between genders. The antennae in males can be two times longer than the elytra, while in females it is one and a half times longer. The length of the last antennal segment of males is almost seven times longer than the pedicel, while in females the difference is only about two and a half times longer. Males and females of O. ocularis can be separated based on the length of the last antennal segment.

Ocorrência de Compsosoma perpulchrum em eucalipto, no estado de Minas Gerais, Brasil

The species of genus Eucalyptus are the most used in the forestry sector, mostly because of its fast growth and adaptation to the different conditions of soil and climate in Brazil. However, a few insects, such as Compsosoma perpulchrum (Vigors, 1825) (Coleoptera: Cerambycidae) can become pests of girdled E. grandis Hill ex. Maiden in the State of Parana. The objective of this work was to report the occurrence of C. perpulchrum in an eucalypt stand in the municipality of Paula Cândido, Minas Gerais State, Brazil. Girdled trees and branches were inspected and measured in March, 2008. The damaged trees were E. urophylla S. T. Blake and most of the girdle occurred in the middle third of the tree height. The length of the girdle range was 3.63±0.18 cm. The length and diameter of the girded branches were 0.94±0.04 m and 0.90±0.06 cm, respectively. This is the first report of the insect damage to this eucalypt species in the State of Minas Gerais.