Synergism of Adjuvants Mixed With Spinetoram for the Management of Bean Flower Thrips,Megalurothrips usitatus(Thysanoptera: Thripidae) in Cowpeas

Abstract

The bean flower thrips, Megalurothrips usitatus (Bagnall) is an economically important insect pest of cowpea, Vigna unguiculata (L.) Walp in south China. Spinetoram is a newly available commercial active ingredient in the spinosyn mode of action group of insecticides that has been recommended for thrips management in China. In this study, the toxicity and efficacy of spinetoram for controlling M. usitatus were evaluated and compared to six other conventional insecticides. In addition, the synergistic effects of adjuvants (Silwet 806, Silwet 618, AgroSpred 910, and AgroSpred Prime) mixed with spinetoram for thrips control on cowpea were evaluated in both the laboratory and the field. Results of this study showed that spinetoram had higher toxicity and field efficacy of M. usitatus than other tested insecticides. A significant increase in efficacy was observed when spinetoram was applied at a recommended rate of 0.67 ml/L, mixed with Silwets (806 and 618) at the rate of 0.5 ml/L. Reductions of 50% and 40% in thrips infestation in the field over treatments without adjuvants were observed 3- and 7-days posttreatments, respectively. However, no significant reduction of M. usitatus was recorded when spinetoram was mixed with AgroSpreds (910 and Prime). Furthermore, no significant differences were found in thrips infestation between spinetoram sprayed alone at the rate of 0.67 ml/L and a reduced rate of spinetoram (0.45 ml/L) mixed with Silwets (806 and 618). The current research shows that Silwets mixed with spinetoram has a synergistic effect in the management of thrips.

A Maximum Dose Bioassay to Assess Efficacy of Spinetoram against Cowpea Thrip Megalurothrips usitatus in China

“…Our results showed that the mortality rates of about 67% (142/212) of the thrip populations exceeded 80%, and 33.96% (72/212) of the populations even exceeded 90%, which indicated that spinetoram still remains effective against cowpea thrips in this region. A previous indoor bioassay also indicated a similar result, that spinetoram had high insecticidal activity against cowpea thrips [9,16,19]. On the other hand, apart from cowpea thrips, spinetoram also actually remains effective against thrip pests in other crop systems.…”

“…Khan et al (2023) discovered that specific temperature and humidity conditions synergistically boost spinetoram's efficacy against Sitophilus granarius and Tribolium castaneum [36]. Tang et al (2022) observed a synergistic impact when combining adjuvants with spinetoram in managing cowpea pests [19]. Furthermore, Tang et al (2016) reported improved efficacy by applying spinetoram prior to the closure of cowpea flowers [37].…”

Assessing the effectiveness of imidacloprid and thiamethoxam via root irrigation against Megalurothrips usitatus (Thysanoptera: Thripidae) and its residual effects on cowpea

“…2022 ). However, they have not met the production needs of cowpea cultivars because of their low field efficacy when applied via foliar spraying ( Tang et al 2022 ). Nevertheless, because these insecticides act systemically, traveling through plant tissues and protecting all parts of the crop, and then acting as neurotoxins against pests, they have been widely applied on seeds and roots of various crops for pest control ( Goulson 2013 ).…”

Parthenogenesis affects interspecific competition between Megalurothrips usitatus and Frankliniella intonsa (Thysanoptera: Thripidae) in changing environment: evidence from life table study

“…Among them, cowpea, Vigna unguiculata (L.) Walp (Fabales: Fabaceae) is the main host plant of M. usitatus . Megalurothrips usitatus can cause damage throughout the vegetative period of cowpea by feeding and laying eggs, especially during flowering/fruiting periods ( Tang et al 2022 , 2023 ). Damaged flower buds/flowers lead to premature abscission, whereas damage to pods causes pericarp scabbing ( Ngakou et al 2008 , Fan et al 2013 , Tang et al 2015a ).…”