1 Primary resources may affect the structure of species assemblages in upper trophic levels of food webs. These bottom‐up effects may involve important ecological processes that affect pest control. For example, population densities of natural enemies may increase when alternative preys are favoured by a new resource.
2 Ants, particularly Solenopsis geminata Forel (Myrmicinae), are recognized as effective predators of herbivores eggs. In the present study, we tested the hypothesis that the addition of a primary resource in a banana agroecosystem will increase pest control of the banana weevil Cosmopolites sordidus Germar (Coleoptera, Curculionidae) by ants.
3 Using stable isotope analyses, we showed that S. geminata used the new resource pathway provided by the addition of a cover crop. This change was revealed by increased δ13C values (13C/12C) in a cover crop treatment (C4 plant) compared with a banana (C3 plant) in bare soil treatment.
4 We also showed that the abundance of S. geminata, as measured with pitfall traps, was 4.8–5.4‐fold higher in the cover crop treatment than in the bare soil treatment. Estimation of egg predation rates was in the range 7.8–70.3%, which occurred in plots with the lowest and highest S. geminata numbers, respectively.
5 The addition of a new primary resource in this system changed the origin of the carbon consumed by predators and increased their densities. The increased ant abundance resulted in increased predation of weevil eggs, which was consistent with our hypothesis. These results will be useful for the design of cropping systems that enhance the biological regulation of pests.
The center of diversity of the genus Musa (Musaceae) is in Southeast Asia, a region not studied in detail and where new species and varieties continue to be reported. A new wild banana species, M. chunii Häkkinen from Yunnan, China is described and illustrated based on observed morphological characteristics in the field. This extremely rare new species was only found in Tongbiguan Nature Reserve, Dehong District, West Yunnan. A key to M. chunii and related taxa is provided. In addition, critical notes regarding M. rubra Kurz identity are given. 相似文献
Infestation of banana and plantain suckers by nematodes (Pratylenchus good-eyi, Radopholus similis and Helicotylenchus multicinctus) and weevils (Cosmopolites sordidus) increased with time from establishment in a field of eight different cultivars. There was a strong association between nematode and weevil infestation; suckers infested with nematodes were more than four times more likely to be infected by weevil than suckers without nematodes. Weevil damage, measured by percentage coefficient of infestation (PCI) at harvest of the bunch, was higher on a plantain (cv. Gonja) and on an east African highland cooking banana (cv. Lusumba) than on the sweet and multi-purpose cultivars. There was a correlation between numbers of male weevils caught in a plot and the mean PCI measured in the plot, but no correlation with female numbers. 相似文献
Visceral leishmaniasis (VL) is a disease that results in approximately 50 000 human deaths annually. It is transmitted through the bites of phlebotomine sandflies and around two‐thirds of cases occur on the Indian subcontinent. Indoor residual spraying (IRS), the efficacy of which depends upon sandfly adults resting indoors, is the only sandfly control method used in India. Recently, in Bihar, India, considerable sandfly numbers have been recorded outdoors in village vegetation, which suggests that IRS may control only a portion of the population. The purpose of this study was to revisit previously published results that suggested some sandflies to be arboreal and to rest on outlying plants by using Centers for Disease Control light traps to capture sandflies in vegetation, including banana plants and palmyra palm trees, in two previously sampled VL‐endemic Bihari villages. Over 3500 sandflies were trapped in vegetation over 12 weeks. The results showed the mean number of sandflies collected per trap night were significantly higher in banana trees than in other vegetation (P = 0.0141) and in female rather than male palmyra palm trees (P = 0.0002). The results raise questions regarding sandfly dispersal, oviposition and feeding behaviours, and suggest a need to refine current control practices in India and to take into account an evolving understanding of sandfly ecology. 相似文献
Pollination ecology of Musa itinerans Cheesman (Musaceae), a pioneer species in the tropical rain forest, was explored in Xishuangbanna, South Yunnan, China. This research involved flowering phenology, nectar production, visitation patterns of pollinators and bagging experiments. It was found that (1) flowering of M. itinerans occurred a whole year round with a peak at the early dry season (Nov.) and the daily flowering pattern had two obvious peaks in the early morning and in the late evening, respectively; (2) nectar production occurred at two obvious peaks, during the day and in the night-time (from 8 am to 12 pm, and from 8 pm to 12 am, respectively), which allowed the two different foragers to visit at specific times; and (3) long-tongue fruit bats ( Macroglossus sobrinus ) and sunbirds ( Arachnothera longirostris ) were both effective pollinators of Musa itinerans. 相似文献
Market crop wastes of banana (Musa acuminata) leaves and pseudo-stem sheaths, sweet potato (Ipomoea batatas) vines and Solanum aethiopicum (traditionally known as nakati) were collected from three major markets in Kampala (Uganda). The wastes were evaluated for chemical composition during the dry and wet seasons, rumen degradation using three cannulated indigenous mature ewes, and digestibility using 12 indigenous intact growing male goats, 4–6 months old and weighing 15.8 kg (S.D. 2.1). The goats in the digestibility study were kept in metabolism cages and fed the wastes as sole diets, either fresh or wilted.
Mean dry matter (DM) content was 97, 121, 197 and 216 g/kg for pseudo-stem sheaths, nakati, sweet potato vines and banana leaves, respectively. Crude protein (CP) was 34, 109, 112 and 114 g/kg DM for pseudo-stem sheaths, banana leaves, sweet potato vines and nakati, respectively. The chemical composition was similar among seasons and markets for the banana based wastes. However, for sweet potato vines and nakati, the wet season wastes had significantly higher CP and lower NDFom and ADFom. Chemical composition was different (P<0.05) among the markets for nakati. Effective degradability differed (P<0.05) between the wastes, averaging 0.43 (banana leaves), 0.47 (pseudo-stem sheaths) and 0.56 (nakati) to 0.69 g/g DM incubated (sweet potato vines). DM intake, N retention and digestibility were not significantly affected by wilting. Average DM intake was 176, 270 and 559 g/day; CP intake was 26, 30 and 63 g/day, while metabolizable energy (ME) intake was 1.3, 1.7 and 5.1 MJ/day for nakati, banana leaves and sweet potato vines, respectively. N retention (as a fraction of N intake) was −0.51 (banana leaves), 0.62 (nakati) and 0.39 (sweet potato vines). The organic matter (OM) and CP digestibilities of banana leaves were low, averaging 0.52 and 0.49, respectively. The high moisture content of nakati wastes resulted in low intake, whereas banana leaves had a low degradation rate and a low N retention. Market sweet potato vine wastes were sufficient to provide the CP and ME required by growing goats under tropical conditions. 相似文献