Prey suitability of Tuta absoluta larvae (Lepidoptera: Gelechiidae) for three predatory phytoseiid mites (Acari: Phytoseiidae) under laboratory conditions

Tomato crop in the Mediterranean Basin has been recently affected by the exotic pest Tuta absoluta (Meyrick), which is difficult to control due to its high reproduction rate and potential to develop resistance to insecticides. In this paper, the suitability and effectiveness of three predatory phytoseiid mites Cydnoseius negevi (Swirski and Amitai), Neoseiulus barkeri (Hughes) and Amblyseius largoensis (Muma), an indigenous species, were evaluated on larvae of T. absoluta under laboratory conditions. First instar larvae of T. absoluta proved to be possible food source for tested phytoseiid mites under laboratory conditions. Females of C. negevi, A. largoensis and N. barkeri were able to feed and sustain oviposition on unfed, first instar larvae of T. absoluta. A diet of insect larvae provided the shortest oviposition period and adult longevity of C. negevi and A. largoensis, while N. barkeri showed the longest corresponding periods. The total and daily number of insect larvae consumed was significantly higher in N. barkeri than in A. largoensis and C. negevi. Likewise, N. barkeri laid significantly higher number of eggs (23.6 eggs / female) than that deposited by C. negevi and A. largoensis (2.5 and 3.9 eggs / female). The sex ratio of the progeny was female biased and ranged: (females / total=0.62-0.68%) when insect larvae were provided for females of C. negevi, A. largoensis and N. barkeri

Behavioural response of alate Aphis craccivora Koch(Homoptera: Aphididae) to volatiles from different cowpea cultivars

The cowpea aphid, Aphis craccivora, is a major insect pest of cowpea in Africa. Volatile organic compounds (VOCs) mediate plant–arthropod interactions that could be used in the management of insect pests. In this study, we established the VOC profile involved in the interaction between A. craccivora and four cowpea cultivars, namely Ex‐Luanda, Katumani 80, Machakos 66 and Ken Kunde 1. Behavioural assays were conducted to study host preference and gas chromatography‐mass spectrometry (GC/MS) for chemical analysis of volatiles. In preference assays, alate A. craccivora had no significant preference for any of the four cowpea cultivars tested. However, in the olfactometer assays, the aphids showed a significant preference for odours from cultivar Ex‐Luanda compared to Katumani 80. Machakos 66 and Ken Kunde 1 elicited neutral responses. In pairwise comparisons, alate A. craccivora did not distinguish between odours of respective cowpea cultivars. GC/MS analysis identified 23 compounds in the volatiles of the four cowpea cultivars. Not all compounds were detected in all cowpea cultivars, and the detected compounds amounts varied in each cultivar. Of these, only four compounds (hexanal, (E)‐2‐hexenal, 1‐octen‐3‐ol and p‐xylene) were emitted in significantly different quantities in the four cultivars. A blend of hexanal and (E)‐2‐hexenal added to cowpea cultivar Ex‐Luanda decreased its attractiveness to A. craccivora compared to the control. Our findings showed differential attractiveness of VOCs of cowpea cultivars to A. craccivora, suggesting that VOCs could be used in the management of A. craccivora