Population dynamics of Steneotarsonemus concavuscutum, a neglected mite pest in coconut fruits (Cocos nucifera)

The meristematic region of Cocos nucifera fruits can be colonized by various species of mites, including Steneotarsonemus concavuscutum, Steneotarsonemus furcatus, and Aceria guerreronis. The consequence of this colonization is the development of necrotic lesions on the fruit, and sometimes its abortion. Losses are commonly attributed to A. guerreronis alone, owing to the similarities in the injuries caused and its predominance in coconut plantations. However, S. concavuscutum may be the predominant pest species in some crops. Despite the possible impact of S. concavuscutum, little is known about its bioecological aspects, such as the influence of biotic and abiotic factors on its population dynamics. Our objective was to document macroclimatic abiotic factors (temperature, relative humidity, and precipitation) and biotic factors (interspecific competition and predation) interfere in the population dynamics of S. concavuscutum. We evaluated the diversity and abundance of mites in the perianth of coconut fruit naturally infested by S. concavuscutum for 1 year. The species found in the fruits of bunch 6 of the plant, which is the fruit age at which the mites commonly reach the highest abundance, were counted every 2 weeks. We found mites from nine families and S. concavuscutum was the predominant species, representing about 92% of the individuals collected. Predators represented approximately 2% of the total collection, with Neoseiulus baraki as the predominant species. Steneotarsonemus concavuscutum population density ranged from 60 to 397 mites/fruit. The highest population densities of S. concavuscutum were observed in the hottest and driest periods of the year. The population densities of S. concavuscutum were negatively associated with the presence of N. baraki, suggesting that this predator may have a role in the biological control of this pest.

Population Dynamics of Drosophila suzukii (Diptera: Drosophilidae) in Berry Crops in Southern Brazil

Drosophila suzukii (Matsumura) is an invasive species originating in Southeast Asia and considered a severe pest in berry crops in several countries of the Northern Hemisphere and Europe. In South America, the species was first detected in 2013. The objective of the study was to monitor the seasonal activity of D. suzukii in commercial crops of blackberry, strawberry guava, surinam cherry, blueberry, and strawberry during two consecutive harvests and in three properties in the Southern region of Brazil during the 2015/2016 and 2016/2017 harvests, with the aid of traps baited with apple cider vinegar. The highest population peaks were observed during late spring to mid-fall in all areas and plant species studied. It was verified that temperature is the factor that most influenced the seasonal activity of D. suzukii in the field, promoting low catches of the species during winter. However, even during periods of low temperatures (winter period), the presence of D. suzukii in the crops was verified, demonstrating the species' ability to stay in place from year to year, surviving in alternative hosts such as Eriobotrya japonica, a common species in the region. The information on the time of the highest occurrence of the pest in different hosts presented in this study provides the basis for decision-making in relation to the management of D. suzukii, to avoid further economic damage.

Biology and phenology of three leaf beetle species (Chrysomelidae) in a montane forest in southeast Brazil

The population phenology of the cassidines, Coptocyclaarcuata and Omaspidestrichroa, and the chrysomeline, Platyphoraaxillaris, was studied at Serra dos Órgãos National Park, State of Rio de Janeiro, southeast Brazil. Monthly surveys of larvae and adults were conducted between 2008 and 2011 at approximately 1000 m altitude on their respective host plants, Cordiapolycephala (Boraginaceae), Ipomoeaphilomega (Convolvulaceae) and Solanumscuticum (Solanaceae). This is the first observation of larviparity and host record for Platyphoraaxillaris. Although having different life history traits, all species showed similar phenologies. They were abundant from October to March, months of high temperatures and intense rainfall, with two distinct reproductive peaks in the same season. Abundance dropped abruptly during the coldest and driest months, from May to August. Frequently none of these species were recorded during June and July. This phenological pattern is similar to other Chrysomelidae living in subtropical areas of Brazil. Temperature and rainfall appear to be the major factors influencing the fluctuation of these three species.

[The correlations between population of Oriental white stork and climate change in the Poyang Lake National Nature Reserve]

This study analyzed the population dynamics of the Oriental white stork (Ciconia boyciana) wintering in the Poyang Lake National Nature Reserve (PLNNR) from 1985 to 2011, to see if there was any relationship with climate change. Testing of several climate variables-monthly average temperature, monthly average maximum and minimum temperature, as well as monthly precipitation-indicated that the population size of the Oriental white stork in the PLNNR was 1,340±178 ind., with significant linear increase and drastic annual fluctuation. Every single year, the population size only significantly correlated with the average minimum temperature of Nov. In theory, the low temperature of Nov. could drive individuals to choose other wetlands in the middle and lower reaches of the Yangtze River, instead of the Poyang Lake as wintering habitats. Meanwhile, temperatures in wintering areas also showed a carry-over effect on subsequent population size. Temperatures in primary stage and later stage of wintering period were significantly correlated with population size 2-9 years later, while the temperature of Oct. was highly significantly correlated with population size 2-5 years after. Temperatures of Feb. and Mar. in the later stage of wintering period were highly significantly correlated with population size of 8 and 3 years after, respectively. Moreover, the stepwise linear regression result showed that the average maximum temperature of Oct. and average maximum temperature of Mar. 2 years ago, as well as the average maximum temperature of Oct. and the average temperature of Mar. 4 years ago were significant predictor factors of the population size fluctuation of the Oriental white stork, which totally accounted for 79.2% of the population size change.

Effects of predator removal on vertebrate prey populations: birds of prey and small mammals

We studied the effects of removal of breeding nomadic avian predators (the kestrel, Falco tinnunculus and Tengmalm's owl, Aegolius funereus) on small mammals (voles of the genera Microtus and Clethrionomys and the common shrew, Sorex araneus) during 1989-1992 in western Finland to find out if these predators have a regulating or limiting impact on their prey populations. We removed potential breeding sites of raptors from five manipulation areas (c. 3 km² each), whereas control areas had nest-boxes in addition to natural cavities and stick-nests. Densities of small mammals were monitored by snap-trapping in April, June, and August, and densities of mammalian predators (the least weasel, Mustela nivalis nivalis, the stoat, M. erminea and the red fox, Vulpes vulpes) by snow tracking in early spring and late autumn. The yearly mean number of raptor breeding territories was 0.2-1.0 in reduction areas and 3.0-8.2 in control areas. Breeding raptors alone did not regulate prey populations in the long term, but probably caused short-term changes in the population dynamics of both the main prey, the sibling vole (Microtus rossiaemeridionalis) and an alternative prey (the common shrew). The densities of an alternative prey, the bank vole (Clethrionomys glareolus) decreased in raptor reduction areas, most likely due to increased least weasel predation pressure in the absence of breeding avian predators.