Marçal Pedro Neto

Driving factors of the communities of phytophagous and predatory mites in a physic nut plantation and spontaneous plants associated

Seasonal changes in climate and plant diversity are known to affect the population dynamics of both pests and natural enemies within agroecosystems. In Brazil, spontaneous plants are usually tolerated in small-scale physic nut plantations over the year, which in turn may mediate interactions between pests and natural enemies within this agroecosystem. Here, we aimed to access the influence of seasonal variation of abiotic (temperature, relative humidity and rainfall) and biotic (diversity of spontaneous plants, overall richness and density of mites) factors on the communities of phytophagous and predatory mites found in a physic nut plantation and its associated spontaneous plants. Mite sampling was monthly conducted in dicotyledonous and monocotyledonous leaves of spontaneous plants as well as in physic nut shrubs over an entire year. In the dry season there was a higher abundance of phytophagous mites (Tenuipalpidae, Tarsonemidae and Tetranychidae) on spontaneous plants than on physic nut shrubs, while predatory mites (Phytoseiidae) showed the opposite pattern. The overall density of mites on spontaneous plants increased with relative humidity and diversity of spontaneous plants. Rainfall was the variable that most influenced the density of mites inhabiting physic nut shrubs. Agroecosystems comprising spontaneous plants associated with crops harbour a rich mite community including species of different trophic levels which potentially benefit natural pest control due to increased diversity and abundance of natural enemies.

Biologia e tabela de vida do ácaro-vermelho Tetranychus bastosi em pinhão-manso

The objective of this work was to determine the biology and life table of Tetranychus bastosi on physic nut (Jatropha curcas). The experiment was carried out under controlled conditions at 26oC and 75% RH, with photophase of 12 hours. The eggs used in the experiments were obtained from stock culture. Evaluations were performed twice a day for the biology of the mite, and once a day for reproductive parameters. The average life cycle of females was 9.63 days and that of males was 8.94 days. The sex ratio was 0.65, and the mean longevity of females was 16 days, with average production of 59 eggs per female. The life table parameters obtained were: liquid reproduction rate (Ro), 45.41 individuals; average generation length (T), 12.66 days; intrinsic growth rate (rm), 0.0538 female per female per day; finite growth rate (λ), 1.023 female per female; and time required for doubling the population (TD), 3.15 days. The spider mite T. bastosi develops well and presents a high reproductive potential on leaves of physic nut.

First Report of Giant Grasshopper Tropidacris collaris (Orthoptera: Acridoidea: Romaleidae) Attacking Plantations of Acacia mangium (Fabaceae) in Brazil

In 2012, plantations with trees of genus Acacia occupied an area of 148,311 ha, representing the second most extensive type of forest plantations in Brazil, excluding pinus and eucalyptus plantations. The species Acacia mearnsii De Wild and Acacia mangium De Wild are the most commonly planted in Brazil (Abraf, 2013). In that same period Tocantins was the Brazilian state with the highest rates of new forest plantation areas, including Eucalyptus and Pinus, and other species such as A. mangium (Abraf, 2013). Among the pests of A. mangium are the twig girdler beetles of the genus Oncideres (Cordeiro et al., 2010; Lemes et al., 2012; Lemes et al. 2013). Other harmful insects have also been reported, e.g., caterpillars, leaf-cutting ants and grasshoppers of Acrididae family (Lunz et al., 2011). In Brazil, a number of species of grasshoppers cause economic losses, at least 23 of them being considered pests (Anonymous, 1982). Rhammatocerus schistocercoides, Schistocerca pallens and Stiphra robusta are among the major locust/grasshoppers pests in Brazil (Xavier-Santos et al., 1999). In addition to these, Tropidacris collaris (Orthoptera: Romaleidae), known as the ‘‘blue-winged grasshopper’’ or ‘‘giant grasshopper’’, cause losses to agriculture in the State of Pará, especially in cassava crops (Roel, 2001) and ornamental plants (Ribeiro et al., 2013) and also is an important pest of several crops in Argentina (Pelizza et al., 2011; Pelizza et al., 2012). Although this is considered a polyphagous species, adults prefer leaves of trees and shrubs (Carbonell et al., 1986). They occur mainly in the rainy season and their nymphs are gregarious and consume virtually any type of plant material that they find (Carbonell et al., 1986; Chagas et al., 1995; Pelizza et al., 2012). In this paper we report the first record of an outbreak of T. collaris in A. mangium, in the state of Tocantins, Brazil. Surveys were conducted in an area of 98.13 ha of Acacia mangium De Wild, in which the trees were 12 months of age, and at 3.5 3 2.5 m spacing, located in the city of Natividade, State of Tocantins, Brazil (11u579300S and 41u359600W, altitude 323 m, average annual temperature between 23 and 26uC and average annual rainfall between 1500 and 1800 mm). This area was monitored after grasshoppers had been reported damaging the trees. We first surveyed areas that had a history of grasshoppers or where it had rained recently, to determine the level of infestation. We also verified the presence or absence of grasshoppers, their life stage (solitary, gregarious or migratory), maturity (egg stage, nymph stage and adult), reproductive phase (mating or oviposition), density and physical size. Adults and nymphs specimens were prepared and sent for determination to Dr. Carlos Franklin Sperber, Department of General Biology, Universidade Federal de Viçosa, Minas Gerais, Brazil. Specimens were deposited in the Regional Museum of Entomology of Universidade Federal de Viçosa (UFVB), in the Laboratory of Entomology of the Universidade Federal do Tocantins (UFT) and in the Braxcel Florestal S.A. The species was identified as Tropidacris collaris (Stoll, 1813) (Orthoptera: Romaleidae) (Fig. 1), a grasshopper usually reported exceeding 10 cm in length (Carbonell et al., 1986; Lange et al., 2008). Tropidacris collaris is found in most of South America, from Colombia to Argentina (Carbonell, 1986) and it is very abundant in the Northeast region of Brazil, occurring from dry to rain forests, and also in Brazilian savannah (Santos et al., 2007). This species occurs all over Brazil with sudden population