الفهرس 
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Abstract
1-Laboratory assays of entomopathogenic nematodes against sugar cane stem borer Sesamia cretica:
The laboratory studies of the current work, were conducted in Plant Protection Department, Faculty of Agriculture, Minia University. It was conducted to assay the potential of two species of entomopathogenic nematodes a local isolate of Steinernema carpocapsae (AT4) and an imported species, Heterorhabdities bacteriophora (HP88) against Sesamia cretica. The bioassay data of the cumulative mortality percentages of Sesamia cretica last (larval) instar larvae during 4 days post exposure to different concentrations of the entomopathogenic nematode Steinernema carpocapsae (AT4) in the laboratory show that the cumulative mortality after 4 days post nematode application reached 40% with the concentration of 50 infective juveniles and 86% with the concentration of 600 IJs /ml. of Steinernema carpocapsae (AT4). The calculated LC50 value was 152.8 IJs/ml. and the total numbers of emerged juveniles from insect cadavers with the treated concentrations were 86450, 116077, 123400, 114050 and 100030 infective nematode juveniles /insect cadaver, respectively. In contrast, pupae of S. cretica exposed to Steinernema carpocapsae (AT4) were less affected than the last (larval) instar larvae, whereas the mortality percentage was 20% with the use of lower nematode concentration and reached 80% with the higher nematode concentration and the calculated LC50 was 482 IJs/ml. The emerged infective juveniles from the pupa cadaver were 45120, 84030, 90116, 77600 and 62224.
The tested imported entomopathogenic nematode, Heterorhabditis bacteriophora (HP88) against the lastinstar larvae of S. cretica explained obvious effect causing mortality after 4 days from application ranged between 44 to 88% with the concentrations of 50 and 600 IJs and the estimated LC50 was 67 IJs/ml. The emerged juveniles from the last instar larvae at the concentrations of 50, 100, 200, 400 and 600 IJs/ml. were 72200, 100144, 114500, 97600 and 88450 infective juveniles /cadaver. As for the exposure of S. cretica pupae to the imported species Heterorhabditis bacteriophora (HP88), the mortality of pupae ranged between 40 and 80% with concentrations of 50 and 600 IJs/ml. of water suspension and the counted LC50 was 150.5 IJs/ml.
2- Laboratory assays of entomopathogenic nematodes against the red palm weevil Rhynchophorus ferrugineus:
Other laboratory studies were conducted for evaluating the effect of the two tested entomopathogenic nematodes Steinernema carpocapsae (AT4) and Heterorhabditis bacteriophora (HP88) against the red palm weevil. The cumulative mortalities of the 3rd instar larvae of the red palm weevil caused by the exposure to the imported species, H. bacteriophora (HP88) at the concentrations of 50, 100, 200, 400 and 600 IJs/0.5 ml were 50, 58, 70, 78 and 84% after 12 days (from) post nematode exposure, respectively. The calculated LC50 of H. bacteriophora (HP88) was 113.5 IJs/0.5 ml. The emergence of infective juveniles (stage) of H. bacteriophora (HP88) from the cadavers of 3rd instar larvae of the red palm weevil after 12 days post exposure to the following nematode IJs concentrations 50, 100, 200 , 400 and 600 IJs/0.5 were 30, 430, 366, 90 and 30 infective juveniles/insect cadaver. The cumulative mortalities of the last instar larvae during 12 days post exposure to H. bacteriophora (HP88) were 37, 42, 55, 68 and 78% at the nematode concentrations of 50, 100, 200, 400 and 600/0.5 ml. of nematode suspension, respectively. The estimated LC50 was 279.1 IJs/0.5 ml. The counted emerged nematode infective juveniles of H. bacteriophora (HP88) from the cadavers of last instar larvae after 12 days post exposure to 50, 100, 200, 400 and 600 IJs/0.5 ml. were 500, 1200, 2750, 1788 and 1400 nematode infective juveniles/insect cadaver, respectively.
Cumulative mortality percent of the red palm weevil adult during 12 days post exposure to different concentrations of H. bacteriophora (HP88) were 32, 36, 46, 52 and 70% at the nematode IJs concentrations of 250, 500, 1000, 2000 and 4000 IJs/0.5 ml. LC50 value was 2001 IJs/0.5 ml. The emerged infective juveniles of H. bacteriophora (HP88) were 877, 2540, 5178, 8300 and 3520/adult insect at the tested concentrations of 250, 500, 1000, 2000 and 4000 IJs/0.5 ml., respectively.
The cumulative mortality percent of the red palm weevil 3rd instar larvae during 12 days post exposure to different IJ concentrations of Steinernema carpocapsae (AT4) ranged between 48 to 90% with the use of infective juvenile concentrations between 50 to 600 IJs/0.5. The calculated LC50 was 43.82 IJs/0.5 ml. The production of invasive larvae 12 days post exposure to nematode infective juveniles was 120, 634, 1425, 1214 and 890 infective juveniles/ insect cadaver. The exposure of the last instar larvae of the red palm weevil to Steinernema carpocapsae (AT4) in the laboratory caused varied mortalities of 40, 46, 58, 78 and 82% with nematode concentrations of 50, 100, 200, 400 and 600 IJs of Steinernema carpocapsae (AT4)/0.5 ml. The calculated LC50 for the last instar larvae was 109.8 IJs. The emerged dauer larvae from the insect cadaver were 692, 1450, 2140, 1200 and 940 at the above mentioned concentrations, respectively. Mortality percentages of the adult stage of the red palm weevil caused by Steinernema carpocapsae (AT4) at 250, 500, 1000, 2000 and 4000 IJs/0.5 ml. were 36, 40, 48, 58 and 76%, and the numbers of emerged infective juveniles per insect cadaver were 36700, 42500, 65240, 24180 and 20143, with the above-mentioned nematode concentrations, respectively respectively. The estimated LC50 recorded was 700.7 IJs/ 0.5 ml.
3- Field application of the entomopathogenic nematodes against sugar cane stem borer Sesamia cretica during 2016:
Field application of Heterorhabditis bacteriophora (HP88) against sugarcane stem borer during 2016 (15 April 2016) was achieved at sunset time using knapsack sprayer. The reduction percentages of the dead plant hearts 14 days post nematode exposure to the tested concentrations of 200, 400, 600, 800 and 1000 IJs/ml. were 39.1, 56.5, 73.9, 73.9 and 78.3%, respectively. While the reduction percentages caused by Steinernema carpocapsae (AT4) were 34.0, 46.0, 66.0, 72.0 and 74.0 at the above-mentioned tested concentrations, respectively. These results revealed the superior of H. bacteriophora (HP88) than Steinernema carpocapsae (AT4) in reducing the infestation by Sesamia cretica to sugarcane. It was obvious that the reduction percentages were increased with time post treatment that these results are in opposite with the results usually obtained with most chemical insecticides. It may be attributed to the propagation of the natural enemies i. e. entomopathogenic nematodes and their persistence in the environment contrary to chemical insecticides that mostly degraded in the environment when time passed.
4-Field application of the entomopathogenic nematodes against sugar cane stem borer Sesamia cretica during 2017:
The reduction percentages of the dead plant hearts during 2017 after 14 days post nematode exposure to the tested concentrations of H. bacteriophora (HP88) were 45.5, 59.1, 77.3, 77.3 and 81.8%, at the tested nematode IJs concentrations of 200, 400, 600 and 1000 IJs, respectively. While the reduction percentages caused by Steinernema carpocapsae (AT4) were 43.2, 49.1, 67.9, 73.6 and 75.5% during 2017 at the tested nematode IJs concentrations of 200, 400, 600 and 1000 IJs, respectively.
5- Field application of the entomopathogenic nematodes against date palm insect pests during 2017:
The reduction in the infestation with the red palm weevil after, two, four and eight weeks post nematode application with Steinernema carpocapsae (AT4) during 2017 positive control results was in ascending with time post application contrary to H. bacteriophora (HP88) where reduction of infestation was in descending with the passing time post treatment. The reduction of infestation with the red palm weevil ranged between 44.4 to 76.9% with Steinernema carpocapsae (AT4) at the rate of 1000 IJs/ml. and between 77.8 to 84.6% at the rate of 4000 IJs/ml. after two and eight weeks post nematode application, respectively. While reductions in infestation with the red palm weevil using H. bacteriophora (HP88) ranged between 33.3 to 7.7% and between 55.6 to 30.8% at the concentrations of 1000 and 4000 IJs/ml. after two and four weeks post nematode treatment, respectively. These results shed the light on a possible problem may occur when H. bacteriophora (HP88) used against the red palm weevil contrary to Steinernema carpocapsae (AT4). This result can be attributed to the encapsulation that occur against H. bacteriophora (HP88) while Steinernema carpocapsae (AT4) was not reported to be encapsulated by Rhynchophorus ferrugineus hemocytes.
The impact of field application with entomopathogenic nematodes on palm frond borer was investigated with significant reduction percentages in this insect infestation, the reduction of infestation with this insect pest declined with time passing post nermatode application by H. bacteriophora (HP88) from 64.3 to 35.3% and from 71.4 to 52.9% with the lower and higher nematode IJs concentrations of 1000 and 4000 IJs/ml., respectively. While the reduction percentages when Steinernema carpocapsae (AT4) was used increased during the course of the current investigation (8 weeks) from 71.4 to 76.5% and from 78.6 to 88.2% at the lower and higher nematode concentrations of 1000 and 4000 IJs/ml., respectively.
Results of controlling the lesser date moth, Batrachedra amydraula using entomopatogenic nematodes in the field showed that the entomopathogenic nematode, H. bacteriophora (HP88) surpassed Steinernema carpocapsae (AT4) in reducing the infestation with the lesser date moth. These reductions by H. bacteriophora (HP88) increased with the increase of nematode concentration. The high reduction rate of (95.7%) was realized with the concentration of 4000 IJs/ml. of H. bacteriophora (HP88) after two weeks post nematode treatment opposite to the low reduction in insect infestation (66.7 %) that attained with the low concentration of Steinernema carpocapsae (AT4) after eight weeks post nematode application.
Control of the pomegranate butterfly, Virachola livia on date palm fruits in the field by the tested entomopathogenic nematodes (H. bacteriophora (HP88) and Steinernema carpocapsae (AT4) revealed high control impact of 93.8% by H. bacteriophora (HP88) after one week post nematode application at the concentration of 4000 IJs/ml. This reduction was gradually declined reaching 80.9% at the eighth week post nematode treatment. The second tested nematode species Steinernema carpocapsae (AT4) gave less reduction of infestation after eight weeks post nematode treatment by 1000 IJs/ ml. with only 57.1 reduction percentage.
6- Field application of the entomopathogenic nematodes against date palm insect pests during 2018:
The infestation with the red palm weevil after, two, four and eight weeks post nematode application with Steinernema carpocapsae (AT4) during the year 2018 The reduction of infestation through time took an ascending trend with time passing post nematode application contary to the case with H. bacteriophora (HP88) where reduction of infestation was in descending order with the passing time post treatment. The reduction of infestation in the red palm weevil ranged between 55.6 to 84.6% with Steinernema carpocapsae (AT4) at the rate of 1000 IJs/ml. and between 66.7 to 92.3% at the rate of 4000 IJs/ml. after two and eight weeks post nematode application, respectively. While reductions in infestation with red palm weevil using H. bacteriophora (HP88) ranged between 44.4 to 19.2% and between 55.6 to 34.6 % at the concentrations of 1000 and 4000 IJs/ ml. after two and four weeks post nematode treatment, respectively. These results show that H. bacteriophora was less effective than Steinernema carpocapsae (AT4) in controlling this pest.
The effect of field application with entomopathogenic nematodes during 2018 on palm frond borer show decline in the reduction percentages of the infestation with time passing post nematode application by H. bacteriophora (HP88) from 68.8 to 47.1% and from 75.0 to 52.9% with the lower and higher nematode concentrations of 1000 and 4000 IJs/ml., respectively. While the reduction percentages when Steinernema carpocapsae (AT4) was used increased throughout the course of investigation (8 weeks) from 75.0 to 82.4% and from 87.5 to 88.2% at the lower and higher nematode IJs concentrations of 1000 and 4000 IJs, respectively.
Results of controlling the lesser date moth, Batrachedra amydraula by entomopatogenic nematodes show a superior impact of the entomopathogenic nematode, H. bacteriophora (HP88) than Steinernema carpocapsae (AT4) in reducing the infestation with the lesser date moth. These reductions by H. bacteriophora (HP88) increased with the elevation of nematode concentration. The high reduction of the insect infestation was 95.3% was realized with the concentration of 4000 IJs/ml. of H. bacteriophora (HP88) after two weeks post nematode application opposite to the low reduction of 63.8% that was attained with the low concentration of Steinernema carpocapsae (AT4) after eight weeks post nematode application. It was obvious that reduction of infestation caused by the two tested entomopathogenic nematodes decreased with passing time when nematodes were applied against lepidopteran insect pests.
Control of the pomegranate butterfly, Virachola livia on date palm fruits was carried out at Aswan region in 2018 revealing high controlling impact on pomegranate butterfly reached 94.3% by H. bacteriophora (HP88) after two weeks post nematode application at the concentration of 4000 IJs/ml. This reduction gradually declined reaching 76.7% at the eighth week post nematode treatment. The second tested nematode species Steinernema carpocapsae (AT4) had less impact in reducing infestation at the eighth week post nematode treatment with a 53.5% reduction percentage in insect infestation.