Effects of natural occurring plants in olive agroecosystems and insect honeydews on the survival of Chrysoperla carnea (Neuroptera: Chrysopidae)
Abstract: Chrysoperla carnea s. lat. (Stephens 1836) larvae prey on insects including some olive pests, but adults are palyno-glycophagous feeding on pollen, nectar and insect honeydews. Knowledge about potential non-prey foods for adult lacewings is crucial for establishing conservation biological control strategies in crops. In laboratory conditions, we tested the effects of: (i) eleven flowering plant species that bloom sequentially during the year in olive orchards from the northeast of Portugal and (ii) honeydews from the secondary pests of olive trees, Saissetia oleae (Olivier 1791) and Euphyllura olivina (Costa 1839), on the survival of C. carnea s. lat. A pair of newly emerged C. carnea s. lat. were transferred into a glass cage (1.5 l) and provided with one of the food treatments and water. Each treatment had 27 to 35 replicates. Honey (10%) and sucrose (1 M) solutions were used as a positive control while water was used as a negative control. Mortality was checked daily. Survival times among different food treatments were compared using survival analysis (log-rank test). If the overall log-rank test for the survival analysis was significant between group comparisons, the significance of each paired comparison was adjusted to a table-wide level of 5% using the sequential Bonferroni adjustment. C. carnea s. lat. survived several weeks longer when Veronica persica Poir, Lamium purpureum L., Malva sylvestris L. flowers or both insect honeydews were provided than the negative control. Provision of Ranunculus ollissiponensis Pers., Lonicera etrusca Santi, Foeniculum vulgare L. or Daucus carota L. slightly increased the survival time of C. carnea s. lat. The results suggest that establishment of the most beneficial plant species in olive groves could improve the survival of C. carnea s. lat. and consequently its performance as a conservation biological control strategy.