Etoxazole in cotton: why is it indispensable in the management of the two-spotted spider mite?

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The spider mite (Tetranychus urticaeThe cotton mite has become one of the most challenging pests of cotton in Brazil, requiring multiple applications throughout the growing cycle. This change stems from its high biotic potential, short life cycle, parthenogenetic reproduction (in part), and wide host range (Figure 1). Its tendency to aggregate in protected tissues makes chemical control difficult, and redistribution in the field, driven by mechanized operations, contributes to population outbreaks. Furthermore, the intensified use of broad-spectrum insecticides compromises natural enemies, and sublethal effects (hormesis), coupled with monitoring failures and late decisions, favor rapid population recovery. With a global history of resistance, the mite demonstrates a high capacity for selecting less susceptible individuals. In this scenario, exclusively reactive strategies have proven insufficient, making the integrated use of management tactics essential, focusing on molecules effective against eggs, immature stages, and those that "break" the pest's biological cycle, as well as rotating modes of action.

A Sumitomo Chemical discovery: what makes Etoxazole unique?

Etoxazole, the active ingredient in Smite®, is the result of Sumitomo Chemical Co., Ltd.'s innovation program, focused on developing new chemical structures with novel modes of action. Registered in Brazil since 2007, it stands out for its high affinity with the plant cuticle, promoting excellent adhesion and stability, in addition to exhibiting translaminar action, which is a decisive advantage in crops such as cotton, with dense canopies, to ensure that the active ingredient reaches the population concentrated on the abaxial surface of the leaves, the region where mites feed, lay eggs, and reproduce.

Its distinguishing feature lies in its unique mode of action (IRAC 10B), which inhibits chitin synthesis by acting on Chitin Synthase 1 (CHS1), blocking cuticle formation and preventing molting (Figure 1). This results in high mortality of eggs and juveniles (Figure 2).

Etoxazole also has a strong transovarian effect: exposed females produce non-viable eggs, that is, they do not produce offspring, which directly compromises their reproductive capacity and population growth. In comparative studies, Etoxazole practically eliminated hatching up to nine days after application, while isocycloseram maintained high levels of viable eggs (Figures 3 A and B).

In the context of resistance management (IRM/A), its unique mode of action and efficacy against non-reproductive stages help reduce the population base susceptible to selection, delaying the evolution of resistance. Furthermore, it has a low impact on non-target organisms, making it compatible with more sustainable IPM programs aligned with the concept of more “environmentally friendly” pesticides.

Conclusions and agronomic relevance

The combination of strong ovicidal and juvenile action, a wide safety margin, and a potent transovarian effect gives Etoxazole a strategic role in the management of the two-spotted spider mite. By profoundly interrupting the pest's biological cycle, it reduces its reproductive potential and capacity for reinfestation, allowing for greater efficiency of other IPM tactics. In a scenario of agricultural intensification and increasing cases of resistance, Etoxazole represents an indispensable tool for the sustainability of Brazilian cotton farming.

*Per Juliano Pazini, researcher and R&D coordinator (Insecticides) at Sumitomo Chemical Latin America, Tarcísio Galdino, R&D manager at Sumitomo Chemical Latin America, and LeonardVieira, Marketing Manager for Insecticides and Cotton Crop Leader at Sumitomo Chemical Latin America