Effectiveness of two biopesticides against the invasive tomato pest Tuta absoluta

Abstract

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is among the most devastating pests worldwide of solanaceous plants, particularly of tomato (Solanum lycopersicum L.). Since its recent introduction into sub-Saharan Africa, it has become an additional widespread tomato pest throughout the region. When no control measures are taken, yield losses caused by T. absoluta larvae can reach 100%. Chemical control remains the primary management option despite its many adverse effects and increasing inefficiency due to the species' endophytic habits and ability to develop insecticide resistance. Safer and more effective alternatives are therefore urgently required. Here, we investigated the effectiveness of two bioinsecticides compared to that of a widely used deltamethrin-based synthetic insecticide, in preventing damage caused by T. absoluta larvae to tomato leaves and fruits, thereby affecting tomato yield. A field trial was conducted in 2018 and 2019 in northwestern Senegal using a randomized complete block design. Damage caused by T. absoluta affected approximately 65% of total leaf area and 3-24% of the fruits. Damage to the leaves caused by other insect species or other factors was less significant. At the dose applied, the chemical insecticide did not significantly reduce the surface area of leaflets affected by T. absoluta or other causal agents, the number of T. absoluta mines on the leaflets, or the proportion of fruits damaged. In contrast, the azadirachtin and Bacillus thuringiensis (Bt) formulations rapidly and significantly reduced damage to both leaves and fruits. The proportion of fruits damaged was reduced by a factor two and the total tomato yield was improved, particularly when the Bt formulation was used. In addition to their effectiveness in reducing damage caused by T. absoluta larvae to tomato leaves and fruit, and increasing the yield of marketable fruits, the viability of these organic alternatives was shown. The scope of our results is discussed in the context of T. absoluta control, in particular in integrated pest management programmes for tomato crops.

Prevalence, attachment ability and strength of the biological control agent Bacillus thuringiensis on tomato

“…The authorized Bt biopesticides are often used on tomato plants to control insects (i.e. Lepidoptera and Noctuids larvae) (Gonzalez et al, 1982;Sarr et al, 2021;Stephan et al, 2014) on stem and leaves. Although tomato fruits are not the primary target for biopesticides, some sprayed droplets can also deposit on them.…”

A review of the management of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) with special reference to biological control using plant extracts

“…The most bacterial control agents used to manage T. absoluta is Bacillus thuringiensis, [29,30,31,32] and Saccharopolyspora spinosa [33] . Also, several entomopathogenic fungi are used in the control of tomato leaf miner: Metarhizium anisopliae [34,35] ; Beauveria bassiana [36,37,38] , Aspergillus oryzae [39] , Saria farinosa [40] , Clonostachys sp [38] and Purpureocillium lilacinum [40] .…”

Comprehensive Dissipation of Azadirachtin in Grapes and Tomatoes: The Effect of Bacillus thuringiensis and Tentative Identification of Unknown Metabolites

“…12 The combination of both biopesticides drastically reduces the negative effect to both leaves and fruits affected by lepidoptera pests, being complementary between them. 13 In addition, when more than one compound is applied to treat pests, it may allow a longer persistence of defenses. 3 On the other hand, Bt has pesticide degradation properties, 14−18 metabolites.…”

“…The proteins with the highest pesticide potency are the CRY and vegetative insecticidal proteins (VIP), which have a high specificity for lepidoptera species, highlighting the specificity of biopesticides for which they are more recommended than synthetic pesticides . The combination of both biopesticides drastically reduces the negative effect to both leaves and fruits affected by lepidoptera pests, being complementary between them . In addition, when more than one compound is applied to treat pests, it may allow a longer persistence of defenses …”