Fourth instar larvae of cotton leafworm, Spodoptera littoralis (Boisd.), fed on castor bean leaves treated with sub-lethal concentrations of both alcohol and hexane extracts of Egyptian conyza and Challenger 36% SC insecticide as well to study their effects on mortality, food consumption and utilisation of food. The tested insecticides exhibited relatively high mortality in alcoholic extract of Egyptian conyza (5.0% concentration) followed by Challenger (1.0% concentration). Results showed a slight reduction in the consumption index for larvae treated with both alcoholic extract and Challenger at low concentrations, while hexane extract (5%) recorded significant increase. The approximate digestibility (AD) was reduced in all treatments of alcoholic extract and the relative growth rate insignificantly decreased at 5% concentration, whereas AD increased for larvae fed on Challenger 0.25% concentration. The lower concentration of alcoholic extract of conyza and all treatments of Challenger pesticides induced insignificant decrease in the efficiency of conversion of the ingested food, while hexane extract exhibited insignificant increase. Challenger at all tested concentrations achieved insignificant decrease in the efficiency of the conversion of digested food with respect to the control.
Background: 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. Method: 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 m 2 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 m 2. 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. Results: 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. Conclusion: 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.
Background: The larval internal parasitoids in the genus Meteorus attack certain lepidopterous larvae in different Egyptian fields. Two species, M. rubens and M. gyrator were the most abundant species reared from several lepidopterous larval species, which feed on different host plants in the two selected Governorates in Egypt throughout two successive years. Aim: This work presents a method specifically designed to improve the abundance and the parasitizing potential of M. gyrator in open fields to parasitize and develop on a broad range of noctuid’s pests by releasing considerable number of the parasitoid adults. Also it deals with some aspects of the basic biology of M. gyrator parasitizing Spodoptera littoralis and Autugrapha ni, as mass-rearing hosts. Methodology: 1- Population Dynamics Biweekly samples of lepidopterous larvae were collected from different host plants in the fields of Giza and Faiyum Governorates, for two successive years (November, 2017 to October, 2019). Collected larvae were confined individually under constant conditions until pupation or the emergence of the internal parasitoid’s larvae for pupation. 2- Laboratory Rearing Cultures of some insect larvae, Heliothis armigera, Spodoptera exigua, Agrotis ipsilon, Sesamia cretica, S. littoralis and Autographa ni were reared in laboratory under constant conditions to act as hosts for mass-production of the parasitoid, M. gyrator. Results: Obtained results reveal that A. ipsilon was the main host of M. rubens, it was more abundant in both years and localities of the survey. Meteorus gyrator was recorded at fewer numbers; it was reared from S. littoralis, S. exigua, S. critica, Heliothis spp. and Autographa spp. The parasitism percentage by M. rubens averaged 23.10% at Giza. While in the case of M. gyrator it averaged 3.25%. In Faiyum, the corresponding figure averaged 12.96% parasitism for M. rubens; while it averaged 6.93%, for M. gyrator. To increase the efficacy of M. gyrator, mass production experiments were carried out, suggesting that Autographa ni was the most suitable for mass-rearing than S. littoralis. Conclusion: To increase the efficacy of M. gyrator as an endoparasitoid, its numbers in the field should be increased by releasing a considerable number of adults, to control lepidopterous larval pests.
The present work was carried out to study the biological aspect of B. brevicornis when reared on different hosts (Ephestia kuehniella, Galleria mellonella, Corcera cephalonica, Sesamia cretica, Spodoptera littoralis and Pectinophora gossypiella). Our Results assured that the type of host had great impact on the durations of the immature stages and longevity of the parasitoid. The highest & lowest incubation periods were when reared the parasitoids on Pectinophora gossypiella (45.75±1.4hours) and E. kuehniella (39.87±0.95 hours) respectively, the difference was insignificant at the other hosts. Duration of larval stages was significant shorter when parasitoid reared on S. cretica (1.86±0.079 days) than the rest hosts. The longer pupation period was recorded when parasitoid reared on Pectinophora gossypiella (7.6±0.13 days), but was insignificant on the other hosts. The highest duration period of immature stage was when reared B.brevicornis on P. gossypiella (12.75±0.74 days) but insignificant difference when reared on G.mellonella [ 9.16±0.22 days ] and S. cretica [ 9.91±0.14 days ]. The mean duration of male longevity of parasitoids was longer when reared on E. kuehniella (15.73±0.73 days) and shorter when reared on C.cephalonica (11.75±0.51 days). The mean duration of female parasitoids was highest when reared parasitoids on S. cretica (19.6±0.51 days). The total number of eggs laid per female of B.brevicornis during its life span was highest on Galleria mellonella (268.88±19.65 eggs), and lowest on C.cephalonica (78.1±10.63 eggs). A percentage of eggs hatchability was significantly lowest when reared on S. littoralis (0.09±0.02642 %) than when reared on the other hosts, while percentage of emergence was insignificantly different when reared on Sesamia cretica (87.36±3.92 %) and Pectinophora gossypiella (87.02±3.85 %).
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