Impact of sulfur dust application on the abundance of two important coccinellid predators in marrow fields

Abstract

For the sake of environmental safety, many sulfur formulations were recommended in many Integrated Pest Management (IPM) programs to protect, particularly, edible vegetables and fruit trees from insect and mite pests as well as plant pathogenic diseases. Such formulations, at the recommended application rates, proved to be safer to mammals. Regarding their safety to beneficial arthropods, diversified results were reported. This study was designed to investigate and evaluate the impact of sulfur formulation against some natural enemies naturally prevailing in some vegetable crops. Sulfur formulation (Agricultural Sorell-98%) was recommended by the Ministry of Agriculture, Egypt, as a protectant for vegetable crops against some plant diseases and piercing-sucking pests (aphis, whiteflies, thrips, and mites) at the rate of 30 kg/Feddan 30 days post plantation. The experiment was undertaken in two similar rectangle areas during the season (2016/2017). Each area about 700 m2 was sown with marrow plant. The first area was divided longwise into two halves, each half comprises six rows and divided horizontally into four plots each about 75 m2. Similar plots were done in the second area but no treatments were made (check area). Monitoring the density fluctuations of the natural enemies in the target areas was undertaken at certain intervals (just before dusting, 2, 12, 24, 48, and 72 h and 7 days after application) and achieved early in the morning (7 am). Fifty plants were inspected per plot per time interval in treated and untreated areas. The average number of each natural enemy/time interval and percent increase or decrease in the population density in the treated half and the untreated one were calculated. The obtained data revealed that the least number of the prevailing adults was recorded at the treated plot after 2 h post treatment for Coccinella and after 12 h for Stethorus adults. In addition, it could be observed that the mean number of the recorded adults occurred in the untreated plot of the first area was increased significantly than that of the untreated second area at 12 and 48 h and after 1 week post treatment, this could be referred to the following: when the treated plot was sprayed with sulfur compound, most of the prevailing adults escaped from the dust and migrate to the untreated plot or other clean plants (untreated plot or other surrounding plants), then they returned back gradually to the treated plot. The obtained results clarify that the intelligent handling of sulfur formulations in order to control some pests and plant diseases with minimal or harmless effects towards the adult predators under investigation must be taken in consideration; thus, this could be more favorable to keep the environment clean and non-polluted. In addition, results throw light on that Stethorus punctillum was more susceptible than Coccinella undecimpunctata especially for the sulfur residues on treated plants.