Repellency of Plant Extracts against the Legume Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidae)

Abstract

Megalurothrips sjostedti Trybom is an important pest of cowpea (Vigna unguiculata L.) in Africa. To propose an alternative to chemical control, the repellency of 24 plant extracts was evaluated against adult female thrips of M. sjostedti in the laboratory. Plant extracts in ethanol were separately applied on a filter paper disk in a still air visual cue olfactometer. The results showed highly significant differences in repellency among extract type, concentration and their interactions. We classified the level of repellency into four categories as strong, good, moderate and weak or non- repellent based on hierarchical ascendant classification. We identified Piper nigrum, Cinnamomum zeylanicum, Cinnamomum cassia as strong repellents. Five extracts were classified as good, eight as moderate and the remaining eight extracts were weak or non-repellent. Repellency of the extracts increased with the concentration suggesting that the behavioral response of M. sjostedti was dose-dependent. Mono- and sesquiterpene hydrocarbon compounds from seven highly repellent extracts were identified by gas chromatography-mass spectrometry (GC/MS). The use of repellent extracts could be useful in developing integrated pest management strategies for thrips on legume crops. In this regard, the specific modes of action of the identified compounds need to be investigated to incorporate them into the existing crop protection strategies.

Repellence of Myzus persicae (Sulzer): evidence of two modes of action of volatiles from selected living aromatic plants

“…The number of aphids in each section was recorded 10 and 20 min after the test began. The repulsion index was calculated according to the following formula: …”

“…Several authors state that some plants, belonging to the Lamiaceae and Asteraceae family, produce a number of VOCs with repelling properties against pests, including aphids . However, most of the studies were carried out with essential oils or plant extracts . Nonetheless, information available on living plant volatile effects is scarce.…”

“…5 However, most of the studies were carried out with essential oils or plant extracts. 7,8 Nonetheless, information available on living plant volatile effects is scarce. Various odor effects of aromatic plants with potential to influence aphid behavior were investigated in previous studies.…”

Repellent activity of Cymbopogon citratus and Tagetes minuta and their specific volatiles against Megalurothrips sjostedti

“…Results from the current study show that volatiles from T. minuta and from freshly cut leaves of C. citratus were repellent to female M. sjostedti . Evidence of the repellent effect of extracts and essential oils from both plants on several insects, including thrips, has been reported in previous work (Abtew et al, ; Cornelius & Wycliffe, ). In our study, male and female thrips were repelled by the volatiles from freshly cut leaves, but old cut leaves were not repellent to either males or females.…”

“…Bean flower thrips, M. sjostedti , were reared in the Animal Rearing and Containment Unit (ARCU) at icipe at a temperature of 26 ± 2°C, 50%–60% relative humidity and a 12 L:12 D photoperiod. The insects were reared on French bean pods, Phaseolus vulgaris L. Every 2 days, bean pods containing fresh thrips eggs were transferred to clean jars to obtain adult thrips of the same age (Abtew et al, ; Nyasani, Meyhöfer, Subramanian, & Poehling, ). The newly emerged males (≈10 days from oviposition) and females (≈12 days from oviposition) were used in the respective experiments.…”