Eight Egyptian isolates of entomopathogenic nematodes (EPN), four belong to the genus Heterorhabditis and four belong to Steinernema were evaluated against adult females of the soft tick Argas persicus and engorged females of the hard tick, Boophilus annulatus in the laboratory. Results indicated that two EPN isolates (A4 and 10k) of Heterorhabditis were rapidly fatal and have high pathogenicity (100% mortality after 72 hours) against A. persicus when treated with 1000 nematode Infective Juveniles (IJs/ml). Meanwhile, only one isolate (5B) of Steinernema gave accumulated mortality of 93.33% against A. persicus. Furthermore, Heterorhabditis isolates (10 K and A4) caused 93.33% and 86% mortality to B. annulatus. The most effective EPN isolates of Steinernema were 5B and AT4 against B. annulatus, they both gave ca 86.7% mortality. The LC 50 values of Heterorhabditis spp. (A4 and 10K isolates) after 72 hrs post infection and LT 50 were (27.03 and 257.03 IJs/ml) and (11.94 and 19.2 hrs.), respectively against A. persicus. While, the LC 90 was 360.24 and 765.72 IJs/ml for A4 and 10K isolates, respectively. Meanwhile, A4 and 10K isolates exhibited relatively high values of LC 50, LC 90 and LT 50 against B. annulatus, represented by (358.57±0.71 and 812.83 IJs/ ml); (1258.9 and 2485.9 IJs/ml.) and (25.64 and 51.28 hrs.), respectively. The present study cleared that Entomopathogenic nematodes (EPN) isolates of the genus Heterorhabditis spp. (A4 and 10K) are potentially useful biological tools for tick control.
The efficiency of three isolates of entomopathogenic nematodes indigenous in Egypt, (i. e. Heterorhabditis bacteriophora (EKB20), Steinernema sp. (B32) and Heterorhabiditis sp. (Kasassien isolate)) were determined in the laboratory and field compared with imidacloprid insecticide on the larvae and adults of the red Palm weevil, Rhynchophorus ferrugineus. Results showed that isolates of entomopathogenic nematodes, B32 and EKB20 are more effective than Kasassien against R. ferrugineus larvae at inoculum levels of 1000 and 2000 Infective Juveniles (IJs)/mL. Both isolates of B32 and EKB20 were faster killers achieving more than 90% mortality to the 3 rd instar larvae of the red palm weevil after 72 hrs. Field evaluation showed that Kasassien and EKB20 achieved higher levels of control against diferent stages of R. ferrugineus reaching 100% reduction than the isolate B32 (80.33 % reduction). When the level of palm weevil infestation was moderate (1-3 weevil tunnels/ tree, the reduction percent was 80.33, 100 and 80.66% when the trees were treated with EPN isolates of EKB20, Kasassien and B32 respectively. There was no significant effect when the trees with higher infestation (more than 3 tunnels/palm tree) level were treated with EPN. While as imidacloprid insecticide gave 100% mortality in the three levels of infestation. The current work has indicated that EPN are considered promising biocontrol agents, if correctly applied and released in an integrated control schemes against the red palm weevil.
The virulence of the mother and subcultures of Verticillium lecanii (Zimm.)Viegas maintained on an artificial medium (MYB) was determined. Each passage obtained from the artificial medium was divided into two isolates, the first was left on the artificial medium to obtain the following passage, while the other was subsequently potentiated on a natural insecthost, the mealy bug Icerya seychellarum (Hemiptera: Monophlebidae). The LT 50 value on the mealy bug I. seychellarum exposed to a fungus concentration of 1.7×10 8 spores/ml was calculated. The LT 50 value of the different subcultures (passages) on the natural host was as low as 4.6 days for the zero (mother) passage followed by 5.8, 7.4, 11.3,13.9 and 17.7 days for the five derived passages (subcultures on MYB ), respectively, while these values were low for those subcultures potentiated on I. seychellarum. The higher mortality percentage (100%) was obtained after 13 days using the zero passage (mother culture) followed by 94.4, 79.8, 51.7, 44.9 and 36.0% mortality for 1 st , 2 nd ,3 rd , 4th and 5th subcultures (passages) maintained through the used artificial medium [MYB]), respectively. These results proved that the ascending number of passages of V. lecanii through the used artificial medium (MYB) loses its virulence against I. seychellarum. On the other hand, these results proved that potentiation of V. lecanii passages on a suitable insect-host (I. seychellarum) increase its virulence again and shorten the period of LT 50 . Comparing the five passages potentiated on the natural insect-host (I. seychellarum) and those revealed that have been continuously maintained on the artificial medium, it was found that the virulence of the potentiated subcultures obtained from the natural insect-host was increased by 1.9 fold for the 5 th passage relative to the virulence of the same continuously obtained subculture from the artificial medium.
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