FACTORS AFFECTING THE NATURAL OCCURRENCE OF SOME INSECT BIOCONTROL AGENTS IN CULTIVATED SOIL IN ISMAILIA GOVERNORATE

Document Type : Original Article

Authors

1 Plant Protection Department, Agricultural Research Center, Dokki, Giza, Egypt

2 Plant Pathology Department, Agricultural Research Center, Dokki, Giza, Egypt

3 Soils, Water and Environment Institute, Agricultural Research Center, Giza, Egypt

Abstract

Six hundred forty eight random soil samples from fields culti­vated with vegetables. field crops and fruit trees were examined for the occurrence of biocontrol agents of insect pests using Tenebrio motiler larvae bait. Such agents are found in 24.07% of the total tested soil samples collected at depths of up to 5.0 cm . Such occurrence is de­tected in 53.8% of samples from under fruit trees, in 30.8 % of sam­ples under field crops and in only 15.4% of vegetables soil . Entomo­pathogenic fungi occur at 19.2% and entomoparastic nematodes at 69.78% as an average for five surveyed districts. Other unknown agents also exist in 11.1% of the samples. Tho fungus Eleauveria basalt+. na occurring at 8.4% frequency is found at the live districts except fil­ial! El-Kebeer, while Metarhizium anisoptiae occurring at 10.8% is ab­sent in each of Ismailia and Fayed districts. The entomoparasitic nema­todes Heteromabditis spp. accompanied by the fungus Fuserium spp. are found at the five districts at an average of 59.7%, while the same species of nematodes accompanied by unidentified bacteria is found at each of Ouantara Shark and Ismailia at 10.0%. Other agents are found also in Ouantara Ghat. and Siall El-Kebeer. Soil type affects bioagents occurrence percentage, but not the occurrence itself. B. basslana Is found In high percentage In the soil samples rich in organic matter. The same was recorded with Al. &IMO­ae in clay soil. Nematodes are less frequent in clay soil than other types. No relationship between soil chemical composition and the occurrence of the bioagents is noticed. The herbicides nabu, the fungicides, topsin and sumi-8, the in­secticides. solocron, actollic and the nematicide. nemacur cause the highest inhibitive effect ( 922-96.5 % reduction), whereas the fungi­cides topes and the ridomil, the herbicides gallant and sencor and the nemeticides vydate and furadan have a moderato effect (72.2-83.3% reduction) on the growth of the fungus 8. bossism. The least inhibitive effect on fungal growth is exerted by sulfur (55.6%) and robigan (42.7%). Topsin, vydate, sencor and furadan show the highest inhibitive effect (91.1-94.4 %) to the fungus Metarhizium anisopliao, whereas to-

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