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The extensive use of chemical insecticides to control mosquitoes led to the development of insecticide resistance and environmental health hazards. This caused a surge in interest in eco-friendly biocontrol agents. The present study aimed to explore the susceptibility of different instar larvae of the common mosquito, Culex pipiens Linnaeus, 1758, to the mermithid nematode, Romanomermis iyengari Welch, 1964. Moreover, the effects of R. iyengari on the mosquito pupal developmental time, adult emergence, longevity, female fecundity, as well as egg-hatching rate were determined after larval treatment with an LC50 quantity of the nematode pre-parasites. Different instars of Cx. pipiens (1st–4th) were exposed separately to R. iyengari at concentrations of 1–6 pre-parasites/mosquito larva. Mortality rates of mosquito larvae were observed and the LC50 values were calculated. The estimated LC50 values for the 1st–4th larval instars were 3.18, 2.73, 3.79 and 4 pre-parasites/larva, respectively. Mean percent mortality of the 1st–4th larval instars ranged from 10–94%, 16–100%, 4–100% and 0–52%, respectively. The results indicated that exposure of 4th larval instar to the LC50 of R. iyengari pre-parasites significantly prolonged the duration of pupal development, reduced the percentage of emerged adults and reduced mosquito female fecundity compared with the control. In contrast, adult longevity and the egg-hatching rate did not differ between the control and the exposed group. In conclusion, this isolate of R. iyengari could be a promising biocontrol agent for Egyptian Cx. pipiens. Other trials are required to assess the biocontrol potential of this parasite in field conditions. [ABSTRACT FROM AUTHOR]

The tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) is an important pest of tomato crops in South America and it has recently been introduced to the Mediterranean area including Egypt. It is a devastative insect pest of tomato plantations. Susceptibility of T. absoluta larvae and pupae to the entomopathogenic nematode (EPNs) species; Steinernema monticolum and Heterorhabditis bacteriophora (HP88), was determined in both laboratory and field. Leaf bioassays were conducted in the laboratory to evaluate the nematode's efficacy in killing the insect larvae. H. bacteriophora (HP88) killed 80% of the 4th instar larvae at 600 nematode-infective juveniles (IJs)/ml and 100% at 1200 IJs/ml 72 h post treatment. At the same time, when S. monticolum IJs were used in the laboratory at 600 (IJs)/ml, 80 and 87% mortality was recorded on the 3rd and 4th instar larvae, respectively. Such mortalities were 84 and 89% at 1200 IJs/ml of S. monticolum, respectively. Field efficacy of the two tested nematode species after foliar application on tomato plants was evaluated. Total recorded mortality at H. bacteriophora varied along 3 consecutive years from around 60% in years 2011 and 2012 to 80% mortality in 2013. When S. monticolum was applied, mortality percent varied from 58 to 61% in years 2011 and 2012, respectively and reached a maximum of 67% in 2013. These results indicated that H. bacteriophora (HP88) was more virulent than S. monticolum against T. absoluta in the laboratory and in the field. [ABSTRACT FROM AUTHOR]

The entomopathogenic nematode Heterorhabditis bacteriophora Pionar (HP 88) and the bacterium Bacillus thuringiensis Berliner var. kurstaki were tested in the laboratory against the black cutworm, a widely distributed polyphagous insect pest of vegetables and field crops. The experiment was conducted under 15.7 °C (14 to 19 °C) to simulate the average winter temperature in Egypt. The two biocontrol agents influenced Agrotis ipsilon differently where H. bacteriophora had a more promising control levels than that of B. thuringiensis. Generally, nematode concentration of ca 500 infective juveniles/insect vial was highly effective (100% mortality) within nine days post nematode infection. The highest concentration of the bacterium B. thuringiensis var. kurstaki (2,000 Intern. Units/mg) gave significant larval control after 12 days of bacterial infection. Combined effect of both the nematodes and the bacteria did not result in significantly greater control than that achieved by the nematodes used alone. The present results indicated that nematodes could be used successfully against the black cutworm, Agrotis ipsilon larvae during the winter which is the active season of this insect pest in Egypt. [ABSTRACT FROM AUTHOR]

A species of a fresh water amphipod, Gammarus sp., collected from Wadi El-Rayan, Fayoum governorate, Egypt was described. Predation rate of Gammarus sp. on mosquito larvae was calculated. Gammarus sp. was found feeding on second instars more than first ones and it didn't feed on 3rd or 4th instars mosquito larvae. Effect of light and aeration on the survival of Gammarus sp. was also tested. Light had no significant effect on the survival of Gammarus, while aeration significantly increased its life period under laboratory conditions. [ABSTRACT FROM AUTHOR]

In the presence of second larval instars of three mosquito species the preparasites of Romanomermis culicivorax swam near the water surface in an orthokinetic manner. When the preparasites were ca. 1 mm from the host, they stopped and swam klinotactically toward the host. During this phase, the preparasites secreted a small amount of a putative adhesive material from the anterior region and host contact was completed. The adhesive appeared to aid in attachment of the preparasites to the host and initiation of the search-boring phase. The preparasites glided over the host until a suitable penetration site was found. The penetration phase was initiated by probing with the odontostyle. This was followed by partial paralysis, decreased intestinal peristaltic movement, and temporary cardiac arrest in all host mosquitoes which was probably related to injection of esophageal secretions. SEM observations showed that the abdominal walls were the most frequent site for penetration. As the preparasites entered through the penetration hole, microorganisms adhering to the cuticle of the preparasites were retained by the adhesive which accumulated around the penetration site. Thus, microbial contamination of the host was avoided by a mechanical cleansing mechanism. Penetration was usually completed in less than 10 min.