Population study of Steneotarsonemus spinki (Acari: Tarsonemidae) on three varieties rice sowing in different times.

Pests and diseases are among the most important limiting factors for rice (Oryza sativa) production, as they are responsible for 35 % of economic losses. The adoption of adequate control measures in order to ensure better production rates is required. The Steneotarsonemus spinki mite is a pest that has generated many losses in the rice sector in recent years. The Colombian Agricultural Institute declared in 2005 that the presence of the disease known as “vain grain”, which affects grain quality and crop productivity up to 60 %, generated economic losses for farmers. S. spinki, is part of the complex of organisms that cause “vain grain”. Therefore the objective of this work was to evaluate the population dynamics of S. spinki in different sowing dates in the Agrosavia investigation center of Agustín Codazzi, Cesar, Colombia. For this objective, during 2014 three different rice varieties were sown every 20 +/- 3 days, for a total of seven plantings in a complete block design sown at random in fixed strips with four replications. At 60 days of emergence after each sowing, four plants were taken per replicate per variety at each sampling, with a total of five samplings being performed during the growth stage. In the CI Motilonia entomology unit, the number of mites were counted in the pods of the last three leaves of the central till of each plant. The populations of S. spinki exceeded 100 individuals per plant in some samples, the variety FED 733 presented the largest population of the mite, and the variety FED 2000 represented the smallest one. According to the results, the populations of S. spinki increased in the second semester in advanced physiological stages of the crop. Mite populations appear to have no effect on the yields of the rice varieties evaluated

Entomofauna asociada a pasturas tropicales Cenchrus ciliaris, Chloris gayana y Megathyrsus maximus

Introduction. Pastures are the primary source of food in livestock systems and can be a suitable niche for insects with beneficial and harmful functions. Objective. To estimate the entomofauna associated with three species of pastures, Cenchrus ciliaris, Chloris gayana, and Megathyrsus maximus, in conditions of the Colombian Caribbean. Materials and methods. Ten samplings were carried out in two contrasting periods (August to October 2018 and January to March 2019), three forage species (Cenchrus ciliaris, Megathyrsus maximus, Chloris gayana) within 1000 m2 were used. Arthropods were identified by order and family and typified by functional groups. Diversity and abundance indices by pasture and season were estimated, as well as their correlation with climate. A simple correspondence analysis was performed. Results. A total of 380 insects from 7 orders and 35 families were collected, with the greatest abundance for Hemiptera and Coleoptera. The Shannon’s diversity index was higher for all orders of C. gayana, except for Hemiptera in C. ciliaris. Phytophages were found in a higher percentage (66.84 %), followed by predators (27.11 %). Insect abundance was influenced by the interaction between season and pasture, showing an increase at low temperatures, except for M. maximus. Pastures represented adequate microenvironments to maintain the diversity of insects, the Hemiptera and Coleoptera orders being the most numerous and representative of the functional groups of phytophages and predators, respectively. Conclusion. The entomofauna of C. gayana, C. ciliaris, and M. maximus was similar in insect abundance and diversity, however, insect abundance depended on the influence of the season and pastures

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements