Laboratory screening supports the selection of sesame (Sesamum indicum) to enhance Anagrus spp. parasitoids (Hymenoptera: Mymaridae) of rice planthoppers

Planthopper (Delphacidae) pests have broken out frequently in Asia over the last decade leading to interest in enhancing the impact of natural enemies by growing nectar plants on the bunds that border rice fields. Such targeted use of plant diversity is popular in other crop systems but there is a marked lack of information on the scope for its use in rice, particularly the important aspect of which plant species to use. This study used Y-tube olfactometer assays to measure the response of two important parasitoids of delphacid pests to candidate nectar plants. Anagrus optabilis exhibited significant attraction to the air from six of the seven plant species whilst Anagrus nilaparvatae appeared more selective, exhibiting attraction to only seven of the 23 plants screened and repulsion to one. Sesamum indicum, Emilia sonchifolia, and Impatiens balsamena were the only three plants attractive to both parasitoids. Laboratory longevity of adult female A. nilaparvatae and A. optabilis with access to sesame flowers was significantly greater than with access to sesame from which the flowers were removed plus water. Similarly, both parasitoids parasitized significantly more brown planthopper (Nilaparvatae lugens) eggs in the presence of sesame flowers. Handling time of A. nilaparvatae was reduced from 31.29 to 18.36 min by access to sesame nectar. Findings show that sesame has a marked beneficial effect on key parameters of Anagrus spp. and justifies further evaluation of its utility as a nectar plant to improve biological control in Asian rice systems.