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1.
H. W. Poulsen H. G. Zuckerman C. H. Metzger W. B. Ward W. C. Edmundson E. R. Bennet R. A. Jehle A. B. Beaumont John S. Gardner E. L. Newdick Frank W. Hussey E. J. Wheeler H. C. Moore Marx Koehnke A. G. Tolaas E. E. Isaac H. O. Werner O. Butler William H. Martin K. H. Fernow E. R. Jackman E. B. Tussing E. V. Hardenburg J. B. R. Dickey K. H. Klages G. S. Ralston H. L. Bailey John Tucker 《American Journal of Potato Research》1934,11(8):207-226
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Kate L. Constantine Fernadis Makale Idah Mugambi Duncan Chacha Harrison Rware Alexander Muvea Vincent K. Kipngetich Justice Tambo Adewale Ogunmodede Djami Djeddour Corin F. Pratt Ivan Rwomushana Frances Williams 《Pest management science》2023,79(11):4343-4356
Background
In Kenya, rice (Oryza sativa L.) is mainly produced under irrigation by small-scale farmers. Mwea irrigation scheme (MIS) in Kirinyaga County accounts for 80–88% of rice production. Here, rice is the main source of livelihood and a source of revenue generation for the county. However, a recently established invasive freshwater snail, Pomacea canaliculata (Lamarck) (family: Ampullariidae), a species of apple snail, presents a serious threat to rice production.Results
Household surveys, focus group discussions and key informant interviews highlight apple snail as a serious problem in MIS. Households that observed at least a moderate level of infestation (>20% of cultivated area) experienced significant reductions in rice yield (~14%) and net rice income (~60%). Farmers reported increased use of chemical pesticides for management of apple snail. In addition, the cost of hired labor for physical removal of egg masses and snails is resulting in substantial negative effects on net income. Farmer age, area of land owned, responsibility for decision-making, receipt of extension advice, training, and membership of a farmer organization, were all statistically significant variables to explain farmers awareness of the need for area-wide apple snail management.Conclusion
Strategies to limit the spread of apple snail are urgently needed. A Multi-Institutional Technical Team (MITT) has been established to spearhead management efforts and consolidate advice to farmers on how to manage apple snail. However, without action to mitigate spread, the consequences could be disastrous for rice production and food security in Kenya, and for other rice growing regions across Africa. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献4.
Abdulaziz Anas Rosamma Philip & Isaac Sarojeni Bright Singh 《Aquaculture Research》2008,39(8):885-890
Chitosan has been widely accepted as a wall material for preparing microcapsules of various purposes in human medicine. The possibility of using chitosan as a wall material for microencapsulating nutrients and drugs for aquaculture purposes, specifically to Macrobrachium rosenbergii larvae was evaluated in this study. Two types of chitosan-coated microcapsules were prepared using either acetone (MEC-A) or NaOH (MEC-N) as the cross-linking agents. They were compared with a microbound diet relative to total leaching of nutrients and free amino acids (FAA). Among the microcapsules, MEC-N showed the lowest level of total leaching of nutrients (23.3%) during 5 h of immersion in seawater and released 65% FAA after 60 min. During laboratory trials, 75% larvae had accepted the MEC-N capsule. The results of the study suggest that chitosan can be used as a wall material for preparing microcapsules to deliver drugs and nutrients to M. rosenbergii larvae. 相似文献
5.
Nodulation and root growth increase in lower soil layers of water‐limited faba bean intercropped with wheat
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Below‐ground niche complementarity in legume–cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water‐limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono‐ and intercrops in soil‐filled plexiglass rhizoboxes under water sufficiency (80% of water‐holding capacity) and water limitation (30% of water‐holding capacity). We examined whether intercropping facilitates below‐ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15–30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water‐limited faba bean performance. 相似文献
6.
Landscape Ecology - This study provides a unified, holistic framework for predicting the dynamics of shrub-grass conversion throughout Mediterranean-climate shrublands. This work focuses... 相似文献
7.
Clayton T Larue Michael Goley Lei Shi Artem G Evdokimov Oscar C Sparks Christine Ellis Andrew M Wollacott Timothy J Rydel Coralie E Halls Brook Van Scoyoc Xiaoran Fu Jeffrey R Nageotte Adewale M Adio Meiying Zheng Eric J Sturman Graeme S Garvey Marguerite J Varagona 《Pest management science》2019,75(8):2086-2094
8.
Emamectin is a macrocyclic lactone insecticide with low toxicity to non-target organisms and the environment, and is considered an important component in pest-management programmes for controlling field crop pests. It is a powerful compound for controlling the cotton bollworm Helicoverpa armigera (Hübner). A spray concentration of 25 mg AI litre-1 in a cotton field resulted in over 90% suppression of H armigera larvae up to day 28 after treatment, while similar mortality of the Egyptian cotton leafworm Spodoptera littoralis Boisduval, under the same conditions, was maintained for 3 days only. Emamectin is a potent compound for controlling the western flower thrips Frankliniella occidentalis (Pergande) under both laboratory and field conditions and its activity on adults was over 10-fold greater than that of abamectin. Spray concentrations of 10 and 50 mg AI litre-1 in Ageratum houstonianum Mill flowers resulted in total suppression of adults up to day 11 and of larvae up to day 20 after treatment. Under standard laboratory conditions, emamectin exhibits a considerable activity on the whitefly Bemisia tabaci (Gennadius) and the leafminer Liriomyza huidobrensis (Blanchard). Further studies are required to evaluate its potential activity on the latter pests under field conditions. 相似文献
9.
Cavity spot is a major disease of carrots, causing cavities on the surface of the root. Available commercial varieties show a range of susceptibility but no significant resistance. Seed progeny from 46 tissue culture-derived carrot ( Daucus carota ) somaclones were screened for viability, then 19 selected somaclone families were sown under glasshouse conditions, along with commercial cultivars (Bertan, Nandor, Bolero and Vita Longa) as controls. Mature roots were exposed to Pythium violae in a cavity spot bioassay to determine their response as measured by disease incidence and severity. Some somaclones formed fewer lesions than the least susceptible control cultivar, Vita Longa. Seven somaclonal families that showed a range of susceptibility were sown under field conditions and the assessment was repeated. Although there was little relationship between glasshouse and field-trial results, under field conditions one of the somaclones had a mean incidence of disease, as estimated by transformed data, of 1·9 compared with 37·9 for the most susceptible somaclone and 3·5 for Bolero, the most resistant commercial cultivar. The results indicated that significant genetic variation in susceptibility to cavity spot disease was present in the somaclones. 相似文献
10.
M.E.?Isaac A.M.?GordonEmail author N.?Thevathasan S.K.?Oppong J.?Quashie-Sam 《Agroforestry Systems》2005,65(1):23-31
The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry,
a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion
as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic
matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability
of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and
duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused
on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon
(C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha−1; 15 years: 17.6 Mg C ha−1; 25 years: 18.2 Mg C ha−1) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha−1 but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly
with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease
with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration
rates were 3 Mg C ha−1 y−1, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system. 相似文献