The role of dung beetle species in nitrous oxide emission, ammonia volatilization, and nutrient cycling.

This study evaluated the role of dung beetle species alone or associated under different species on nitrous oxide (N2O) emission, ammonia volatilization, and the performance of pearl millet [Pennisetum glaucum (L.)]. There were seven treatments, including two controls (soil and soil + dung without beetles), single species of Onthophagus taurus [Shreber, 1759] (1), Digitonthophagus gazella [Fabricius, 1787] (2), or Phanaeus vindex [MacLeay, 1819] (3); and their assemblages (1 + 2 and 1 + 2 + 3). Nitrous oxide emission was estimated for 24 days, when pearl millet was planted in sequence to assess growth, nitrogen yield (NY), and dung beetle activity. Dung beetle species presented greater N2O flow of dung on the 6th day (80 g N2O-N ha-1 day-1) compared to soil and dung (2.6 g N2O-N ha-1 day-1). Ammonia emissions varied with the presence of dung beetles (P < 0.05), and D. gazella had less NH3-N on days 1, 6, and 12 with averages of 2061, 1526, and 1048 g ha-1 day-1, respectively. The soil N content increased with dung + beetle application. Dung application affected pearl millet herbage accumulation (HA) regardless of dung beetle presence, and averages ranged from 5 to 8 g DM bucket-1. A PCA analysis was applied to analyze variation and correlation to each variable, but it indicated a low principal component explanation (less than 80%), not enough to explain the variation in findings. Despite the greater dung removal, the largest species, P. vindex and their species combination, need to be more studied to get a better understanding about their contribution on greenhouse gases. The presence of dung beetles prior to planting improved pearl millet production by enhancing N cycling, although assemblages with the three beetle species enhanced N losses to the environment via denitrification.

Host Range and Phenology of Sugarcane Aphid (Hemiptera: Aphididae) and Natural Enemy Community in Sorghum in Haiti.

To determine the factors leading to outbreaks of the sugarcane aphid, Melanaphis sacchari, (Zehntner) (Hemiptera: Aphididae) in sorghum in Haiti, a survey was carried out on farms during two cropping seasons, spring and fall of 2018. A total of 45 plots in three Haitian regions were monitored from the five-leaf stage to grain ripening. Infestation with M. sacchari was significantly higher in spring than in fall, except in one location. Melanaphis sacchari populations varied significantly according to phenological stages of sorghum, with significantly higher abundance during the heading and flowering stages than other stages. In and around sorghum fields, the sugarcane aphid was observed on plants from three families: Poaceae, Malvaceae, and Cucurbitaceae. Aphid natural enemies found in sorghum fields consisted of eight species of ladybeetles (Coleoptera: Coccinellidae), one hoverfly (Diptera: Syrphidae), one lacewing (Neuroptera: Chrysopidae), and one predatory midge (Diptera: Cecidomyiidae). In addition to these predators, two parasitoid species, Adialytus sp. (Hymenoptera: Braconidae) and Pachyneuron aphidis (Bouché) (Hymenoptera: Pteromalidae), emerged from sugarcane aphid mummies. Predator and parasitoid densities were highly affected by growing season, with most of the biological control happening in fall. This study provides insights on sugarcane aphid management in Haiti and the Caribbean Islands.