Predation of a biological control agent, Nesidiocoris tenuis (Hemiptera: Miridae), by the spider Leucauge blanda in greenhouse eggplant crops

ABSTRACT

Nesidiocoris tenuis (Hemiptera: Miridae) is used widely around the world as a biological control agent. In Kochi Prefecture, Japan, at the end of each greenhouse eggplant crop production period, the N. tenuis populations that have developed are collected and transferred to ‘natural-enemy-rearing greenhouses’ so that farmers can use the bug in the next production period. However, spider numbers have been increasing at the end of the production periods and it is becoming difficult to collect N. tenuis in some greenhouses. Therefore, we constructed specific primers for N. tenuis mtDNA to test whether the species was being preyed upon by the predominant spider species, Leucauge blanda. In polymerase chain reactions, these primers amplified a 148-bp fragment of the mitochondrial cytochrome oxidase subunit I gene of N. tenuis but not of any of the 13 other arthropod species tested that occurred in eggplant greenhouses. In a laboratory experiment, the rates of detection of N. tenuis DNA in the spiders after the end of a period of feeding on the bug were 90% at 0 h, 60% at 24 h, and 0% at 72 h. In a greenhouse field experiment, the rate of detection of N. tenuis DNA in the spider was 95%. These results suggest that L. blanda is responsible for the observed suppression of N. tenuis populations in greenhouse eggplant crops.

KEYWORDS:

• Biological control agent
• Nesidiocoris tenuis
• specific primer
• spider

Acknowledgements

We thank the farmers of Aki and the staff of Aki Agricultural Promotion Center for allowing us to collect the spiders. We also thank Mr Tomoyuki Okada and Ms Tomoka Oki for their technical help and Mr Oliver Hawdon for English corrections. We also thank Dr Norihide Hinomoto, Prof. Ryo Arakawa, Dr Takanori Ida, Dr Akira Matsuura and Mr Akitatsu Haccho for providing insect materials.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partly financially supported by the Ministry of Agriculture, Forestry and Fisheries of Japan through a research project entitled ‘Development of technologies for mitigation and adaptation to climate change in agriculture, forestry and fisheries’.