Comparative effectiveness of entomopathogenic nematode Steinernema feltiae, entomopathogenic bacterium Bacillus thuringiensis and Dichlorvos for control of fungus gnat Lycoriella auripila

Document Type : Complete paper

Authors

• Hamed Latifian ¹
• Reza Talaei-Hassanloui ²
• Shiva Haraji ³
• Valiollah Baniameri ⁴

¹ 1. Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

² Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

³ 3. Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

⁴ Iranian Research Institute of Plant Protection, Tehran, Iran

Abstract

Keywords

• field assay
• pest
• edible mushroom
• insect pathogen
• EP

Main Subjects

• Biocontrol of pests

Extended Abstract

Introduction

The cultivated mushroom, Agaricus bisporus, with a share of 11% of the production of edible mushrooms in the world is considered the most important commercial mushroom in Europe and Iran. The commercial production of this mushroom is threatened by a number of insect pests and diseases globally, of which flies and mosquitoes of the Cecidomyiidae, Phoridae and Sciaridae families are more important. The mushroom sciarid, Lycoriella auripila (Dip.: Sciaridae) causes a quantitative and qualitative reduction in crop yield worldwide i.e. Iran. Considering the importance and necessity of L. auripila control in the cultivation of edible mushrooms and in order to reduce the consumption of chemical pesticides, the present study was conducted to estimate the efficacy of the entomopathogenic nematode S. feltiae and the bacterium B. thuringiensis solely and simultaneously in controlling this mushroom mosquito.

Materials and Methods

Edible mushroom and its pest sciarid were grown in the laboratory. The entomopathogenic nematode S. feltiae (Entonem®) and the entomopathogenic bacterium B. thuringiensis subsp. israelensis strain M.H.14 (BioFlash®) were obtained from the Koppert Company, Netherlands and from Natural Biotechnology Company, Iran, respectively. Dichlorvos EC 50% insecticide produced by Aria Chemi group was used. Effects of different treatments of nematode, bacterium and chemical insecticide on the possibility of controlling the larvae of fungus gnat was investigated in the laboratory and field. In the laboratory study, the efficacies of eight treatments, including three concentrations of S. feltiae (Sf), B. thuringiensis subsp. israelensis (Bti) and Dichlorvos pesticide were investigated. Then, nine treatments, including the interaction of Sf and Bti, were performed in addition to the laboratory treatments in the field test. The yields of mushroom production in control and treatments were compared. Statistical analysis of data was done based on the number of whole insects caught in sticky yellow card traps and larvae attracted to potato slices. In the conducted tests, the reductions of the insect population in the treatments compared to the control were calculated. The experiment was done in a randomized complete block design (block in time). The obtained data were analyzed by ANOVA after normality test in SYSTAT version 13 statistical software. The post-ANOVA means were compared with Tukey's test.

Results and Conclusion

The laboratory experiments showed positive effects of all treatments on controlling this pest. The concentration of 1×106 IJ/m2 Sf and 2/1000 Bti had the highest mortality of pest larvae with 81.6 and 77.4% mean mortality, respectively. Sf at this concentration acted better than Dichlorvos for the control of this pest. In the field measurements, the highest population decline was recorded in Bti with 75.7% control efficacy based on yellow sticky cards and in treatments of Dichlorvos and half-dose of two-biocontrol agent based on potato slices data with 75.3 and 74.8%, respectively. No significant difference was observed between Dichlorvos and Sf treatments for the control of this pest based on yellow sticky card data in field study. Also, two pathogens acted additively in controlling the larvae of this pest. Treatments of Dichlorvos, 1×106 IJ/m2 nematode and 1/1000 bacterium, with 17.04, 16.91 and 16.15 Kg/unit, respectively and without any statistical difference, had higher amounts of mean weights for edible mushroom in the flush units. The estimation of the number of nematodes in the culture bed showed that Sf nematode larvae increased nearly three times after one month, from an average number of 2.23 to 5.75 IJ/ml of the suspension prepared from the soil in culture bed. In the application of nematodes, the recommended concentration and time of use are very important and decisive in their effectiveness. The use of high concentrations of nematodes increases their reproduction and reduces the available food, and this causes the emergence of smaller nematodes, which some researchers consider it as a factor in reducing control of L. auripila and consequently the reduction of edible mushroom production. According to the results of the present study, exposing L. auripila gnats to a concentration of 1 × 106 IJ/m2 of the nematode produced 73% mortality rate in the field survey in mushroom halls, which was in line with the results of some researchers using a similar concentration of Sf. The increase in mushroom production in the 4-week period of in the Sf treatment has been well defined. The obtained results recommend using these two biological control agents to control the L. auripila mosquito in edible mushroom cultivation halls. It is noteworthy that the applications of higher concentrations of Sf nematode and Bt bacterium are not useful and they can even have negative results on the mushroom yield performance. Also, the proper time to apply both agents, is after casing soil in edible mushroom cultivation halls.