Sorption-desorption of imidacloprid and its metabolites in soil and vadose zone materials

Sorption-desorption is one of the most important processes affecting the leaching of pesticides through soil because it controls the amount of pesticide available for transport. Subsurface soil properties can significantly affect pesticide transport and the potential for groundwater contamination. This research characterized the sorption-desorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) and three of its metabolites, 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone (imidacloprid-urea), 1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine (imidacloprid-guanidine), and 1-[(6-chloro-3-pyridinyl)methyl]-1H-imidazol-2-amine (imidacloprid-guanidine-olefin), as a function of changing soil properties with depth in two profiles extending from the surface to a depth of 1.8 or 8 m. Sorption of each compound was highly variable and hysteretic in all cases. Normalizing the sorption coefficients (K(f)) to the organic carbon or the clay content of the soil did not reduce the variability in sorption coefficients for any compound. These results illustrate the importance of evaluation of the sorption data used to predict potential mobility. Understanding the variability of soil properties and processes as a function of depth is necessary for accurate prediction of pesticide dissipation.     

Effects of calving season on the voluntary waiting period and reproductive performance of Holstein cows in the tropical savannah

The effects of calving season [rainy (RS) and dry (DS)] on the voluntary waiting period (VWP) of 58 Holstein cows raised in the tropical savannah were investigated using data of temperature humidity index (THI), total antioxidant status (TAS), respiratory rate (RR), rectal temperature (RT), glucose, total cholesterol (TC), triglycerides (TG), velocity of uterine regression, and subsequent reproductive performance. Blood samples and clinical data were taken once every week, from calving until the sixth postpartum week. Reproductive data were collected until 180 days postpartum. THI differed between seasons (P < 0.05], as well as TAS (P < 0.001), RR (P < 0.001), RT (P < 0.01), glucose (P < 0.001), TC, and TG (P < 0.05), with higher values in RS. Although the velocity of uterine regression showed to be slower (P < 0.001) during RS, no differences were present regarding uterine health. Days open increased in RS (P < 0.001), but the number of services/conception was similar (P = 0.33). The results suggested cows under heat stress during the rainy season in the tropical savannah are more susceptible to a decline in the reproductive performance due to oxidative, metabolic, and uterine health problems.     

Feeding preference of Thaumastocoris peregrinus on several Eucalyptus species and the relationship with the profile of terpenes in their essential oils

The feeding preference by Thaumastocoris peregrinus, Carpintero and Dellapé (Heteroptera: Thaumastocoridae) on different Eucalyptus species was evaluated through choice tests in a paired comparisons design. Twenty individuals per combination were tested over a 48 h period, and each one was offered leaves of two species at a time, in all possible combinations. Preference was determined by counting the number of insect excrements on each plant as a proxy for effective feeding, and then ranked through a paired comparison matrix. A linearity index was calculated to test for hierarchy preferences and, after that, a cardinal index (David’s score) was calculated to assign a preference value for each species. The essential oils were extracted from leaves of each Eucalyptus species, and their chemical composition determined through GC-MS. The results show a significant and strictly linear feeding preference ranking between the species tested. The order of preference between species was E. viminalis > E. grandis > E. tereticornis > E. dunnii > E. maidenii > E. globulus. The qualitative and quantitative chemical compositions of the essential oils of these Eucalyptus species differed. A significant correlation was found between the feeding preferences and the concentrations of 1,8-cineole as a repellent and p-cymene as a feeding stimulant. These results underline the importance of selecting the right Eucalyptus species in areas infested by T. peregrinus.     

A health evaluation in a colony of captive collared peccaries (Tayassu tajacu) in the Eastern Amazon

This study pretends to determine baseline data on the health and mortality of a colony of captive collared peccaries in the Eastern Amazon (Belém, State of Pará, Brazil) during a 65-months survey. Thirty-nine out of 166 animals (23.5%) died and were examined post-mortem. Monthly mortality averaged 1.2%. The highest mortality rate was observed in newborns (74.4%). Abandonment by the mother and aggression were responsible for 24.1% and 13.8% of the total newborn deaths, respectively. Most frequent causes of non-neonatal death were food poisoning (50.0%) due to an episode of accidental bitter cassava leaves ingestion and traumatism due to aggressions between animals (10.0%). Results from serology for different infectious diseases showed that 4.9% (2/41) collared peccaries had antibodies against Brucella spp. and 9.8% (4/41) animals had antibodies to two different Leptospira spp. serovars, butembo and autumnalis. This is the first survey of morbidity and mortality in captive collared peccaries in the Amazon region.