INTERACTIONS AMONG THE ENTOMOPATHOGENIC FUNGUS, Cladosporium uridenicolla SPEG., AND TWO WHITEFLIES BENEFICIAL INSECTS, Eretmocerus mundus MERCERT AND Coccienlla undecimpunctata L.: FROM AN IPM PROSPECTIVE | ||||
| Journal of Plant Protection and Pathology | ||||
| Article 3, Volume 30, Issue 7, July 2005, Page 4217-4236 PDF (7.04 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jppp.2005.238989 | ||||
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| Author | ||||
| N. F. Abdel- Baky | ||||
| Economic Entomology Department, Faculty of Agriculture; Mansoura University | ||||
| Abstract | ||||
| Laboratory studies were initiated, for the first time, to evaluate the competitive interactions among the entomopathogenic fungus, Cladosporium uridenicolla and the two whiteflies natural enemies, the internal parasitoid, Eretmoeerus mundus and the coccinellid predator, Coecinella undecimpunctata. The positive and negative effects of these combinations in regulating the population of the silverleaf whitefly, Bemisia argentifolii, were extensively studied. The negative effects on the parasitoid were extremely low. No direct contact or moralities occurred among the parasitoid population when parasitizing the nymphs. Higher percentages of emerging parasitoid adults were also obtained. Meanwhile, when Er. mundus adults were exposed directly to the fungal suspension, the mortality percentage reached 5-7% only. Three to five days after treatment, B. argentifo/ii nymphs were rejected as a host by Er. mundus adult due to the fungal growtti. The majority of Er. mundus females also laid no eggs and no parasitism was detected. The susceptibility of C. undeeimpunctata developmental stage'3 to C. uridenieol/a varied according to spore concentrations and the treated life stages. Eggs were more tolerant to the fungal infection, and hatchability reached 98.5%. The first instar larvae of C. undecimpunetata were more sensitive to infection by C. uridenicol/a, followed by the 2nd instar and pupal. ·Intra-guild predations were detected among the fungus and the predator, because of the predator feeding on the infected SLWF nymphs. Their feeding rates on the nymphs without mycelium varied between 38.65 and 56.5% for the larval instars and adult stage. Meanwhile, when the mycosis appeared on the SLWF nymphs, their feeding rates decreased sharply. Consequently, the pathogen could be considered as the "intra-guild predator" which was directly able to infect the coccinellid predator in the guild. In addition, C. undecimpunctata adults and larvae, that fed on the infected nymphs by the fungus, became also as intra-guild predators of the pathogen. Therefore, the use of both the fungus and the predator in combination had a deleterious effect on the biological control of whiteflies and could minimize the control efficiency. The control efficiency of the three natural enemies of B. argentifolii, when used separately or in combination, varied according to the tested biological agent. Using Er. mundus alone reduced the pest populations by 38.1%, whereas, C. uridenieo/a shared by 19.4% in the pest population reduction. The interaction between C. uridenieola and Er. mundus raised the control efficiency to 57.8%. The use of both Er. mundus and C. undeeimpunctata in combination reduced the pest population by 38.7%. The three biological control agents combined together reduced the pest population by 58.0%. Combination between both C. uridenieola and Er. mundus caused a synergistic relationship (additive). The use of the pathogen in combinations with Er. mundus improved suppression of B. argentifo/ii nymphs. Conversely, antagonism relationship (non-additive) among the pathogen in combinations with the coccinellid predator was detected. Therefore, the combination of C. uridenieo/a and whitefly parasitoids require further studies in other systems. The results suggest that the fungus and the parasitoid or the fungus and the predator may be used together for IPM program of the whiteflies, which may lead to viable control options. The fungus spore application should coincide with the later developmental stage of the parasitoid or the predator developmental stages to pass the sensitive stages in order to conserve these beneficial insects within the system. | ||||
| Keywords | ||||
| Entomopathogenic fungi; Cladosporium uridenieol/a; Eretmoeerus mundus; Coeeinel/a undeeimpunetata; Bemisia argentifo/ii; whitefly natural enemies; interactions; intra-guild predation; Biological control interactions | ||||
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