Whiteflies and whitefly-transmitted viruses cause major agricultural problems in environments ranging from arid to humid climates. Experiments were conducted to assess the effect of some cultural irrigation practices (drip, furrow and sprinkler) on the population of the sweetpotato whitefly, Bemisia tabaci (Gennadius) and on the infection of some whitefly-transmitted viruses in the Egyptian vegetable cropping system. Each irrigation treatment was conducted in cucumber (Cucumis sativus L.), green bean (Phaseolus vulgaris L.), squash (Cucurbita pepo L.) and tomato (Solanum lycopersicum L.). Less than 30% of the plants in each plot displayed whitefly-transmitted virus infection symptoms (Cucumber vein yellowing virus, Squash leaf curl virus and Tomato yellow leaf curl virus). The daily drip irrigation treatment resulted in the lowest whitefly populations (adults and nymphs) and lowest incidences of plants with virus symptoms, while the highest infestations and infections were observed for the weekly sprinkler irrigation treatment and the biweekly furrow irrigation treatment, respectively. Regardless of irrigation treatment, whitefly populations were highly correlated with incidences of plants with virus symptoms. However, percentages of plants displaying virus infection were similar among irrigation treatments on many sample dates within a given crop. Integration of management strategies is essential for sustainable management of whiteflies and whitefly-transmitted viruses. This study demonstrates that certain irrigation methods can affect whitefly populations and incidences of whitefly-transmitted viruses in vegetable crops in Egypt.
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