Bulletin of the National Research Centre (Nov 2019)
Do the diversity of plants and sulphur application influence the population fluctuation of insect predator?
Abstract
Abstract Background Numerous predatory insects were recorded on different plants; some were fed on the floral nectar and others as visitors. Other insects used any plant as a shelter or associated with their prey. Pollinators and beneficial arthropods suffering from a wide range of chemical pesticides are used. So, seeking for safer alternatives is mandatory to conserve such beneficial arthropods. Sorell-98% is a sulphur formulation which was examined against some insect predators with minimal adverse impacts. Method Agricultural Sorell-98% (commercial Sulphur formulation) was applied to protect many crops against some plant diseases and sucking insect pests (aphis, whiteflies, thrips) and mite pests as well. This formulation was applied at a rate of 30 kg/Feddan after 30 days of plantation. Two rectangular areas (ca. 700 m2 each) were chosen to execute experiments. The first area was in a field which was sown with marrow plant, while the second was in an okra field. Each area was partitioned into four equal plots (ca. 75 m2). Similar plots (third area) were done but received no treatments (second control area). Examination of the mean numbers of the natural enemies was recorded at several intervals and was achieved at 7 am. Samples of 50 plants were inspected—on spot—per plot/time interval in the three experimental zones. The mean number of each predator/time interval and percentage of increase and/or decrease was calculated. Results Results reveal that the abundance of the target predators was affected indirectly in different cultivated plants after sulphur application, as a result of different plant nature and consequently the population of pests invaded. At all inspection periods, it was observed that the mean numbers and abundance of adult predators on marrow plants was more than that reported in an okra field. Under all inspection times, there was a significant difference between the mean numbers of recorded predators, where Coccinella adults recorded the highest mean numbers, followed by Chrysoperla adults. Stethorus adults recorded the least mean number, either before or after sulphur application. Conclusion The abundance of any arthropod predators is closely related with their favourable insect prey and did not relate to a certain plant by itself. The three tested adult predators were—to some extent—affliction from the sulphur application.
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