Search

Background: Tetranychus evansi and T. urticae spider mites are known major pests of Solanaceae. Smallholders in Africa rely heavily on pesticide treatments. However, farmers claim that pesticides are generally ineffective despite high‐frequency sprays. New management solutions are thus urgently needed. This study assessed the efficacy of using acaricide‐treated nets combined with predatory mite release for controlling spider mites. Results: The results showed the acaricide‐treated net alone was more effective at reducing numbers of T. urticae than T. evansi. We observed the opposite for release of the predatory mite Phytoseiulus longipes. This difference could be explained by the specific dispersion strategies of the two spider mite pests; T. evansi is gregarious, whereas T. urticae dispersed rapidly. Joint application of both techniques resulted in a synergetic effect that reduced T. evansi and T. urticae spider mite numbers close to zero. The synergetic effect could be explained by predator avoidance behaviour of the prey spider mites, resulting in higher prey trapping and killing rates on acaricide‐treated nets, while P. longipes fed on spider mite eggs. Conclusion: These techniques are profitable for smallholders as they are not expensive and avoid residues on the crop. © 2018 Society of Chemical Industry This study was carried out to assess the efficacy of using acaricide‐treated nets combined with predatory mite release for the control of spider mites. [ABSTRACT FROM AUTHOR]

Abstract: The beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a polyphagous insect that is distributed worldwide and was recently reported as an important pest on African indigenous vegetables. Cotesia icipe Fernandez‐Triana & Fiaboe (Hymenoptera: Braconidae) is a recently described parasitoid, reported from various Afrotropical countries. This work investigated the performance of C. icipe on S. exigua infesting Amaranthus dubius Mart. ex Thell. under laboratory conditions. Cotesia icipe was aggressive on the host and successfully oviposited on S. exigua with 70% of parasitoid females ovipositing after 2 hr of exposure. Parasitoid densities significantly affected the parasitism rate and the nonreproductive larval mortality. Parasitism rate was 9.7 ± 0.8% and 59.5 ± 3.1% for a single and cohort of five females released, respectively, when offered 50 host larvae. The cohort female release resulted in significantly higher larval nonreproductive mortality than the single release. However, there was no significant difference between parasitoid release densities in regard to pupal nonreproductive mortality. The larval and pupal mortalities in the presence of C. icipe were significantly higher than the natural mortalities at both parasitoid release densities. The parasitoid sex ratio was female‐biased for the cohort females but balanced when a single female was released. The hind tibia and forewing lengths were not affected by the density of female parasitoids but there were variations according to sex. The implication of these findings on the potential use of C. icipe for biological control of S. exigua in amaranth production systems is discussed. [ABSTRACT FROM AUTHOR]