Chinese researchers discovered that some individuals of tomato moth (Absolutely all) have developed resistance to tetraniliprole. The pest attacks several solanaceous crops, including tomatoes, peppers and potatoes. The study, carried out with 18 populations of Absolute T. from northern China, revealed moderate resistance to the insecticide. The Huailai population showed 36,2-fold greater resistance compared to the susceptible YN-S strain.
The application of chemical insecticides is the main measure used to control invasive pests such as Tuta absolute. However, unjudicious use of these products has resulted in the development of resistance to many common pesticides such as organophosphates, pyrethroids and others. In China, pest populations in Yunnan and Xinjiang have already shown moderate resistance to insecticides such as spinosad and indoxacarb.
Diamide insecticides such as tetraniliprole have been introduced as a new hope for controlling resistant pests. These insecticides act on insects' ryanodine receptors, causing uncontrolled release of calcium, muscle paralysis and death. Tetraniliprole has shown significant efficacy against several agricultural pests. However, the study revealed that the Huailai population of Absolutely all developed moderate resistance to tetraniliprole, in addition to cross-resistance to other diamidic insecticides such as chlorantraniliprole and flubendiamide.
The first case of resistance to chlorantraniliprole in China was reported in 2012, in a population of Plutella xylostella collected in the field. Since then, cases of moderate to high resistance to commercial diamides, such as chlorantraniliprole, flubendiamide and cyantraniliprole, have been reported in species such as Spodoptera exigua, Spodoptera litura e Chilo suppressalis. In 2017, Absolutely all invaded China through the Xinjiang Uyghur Autonomous Region. Recent research has shown that field populations of Absolutely all from Xinjiang exhibit significant resistance to chlorantraniliprole.
Tetraniliprole is a diamidic insecticide recently registered in that country. It was developed to control agricultural pests from multiple orders of insects in crops such as corn, tobacco, rice and vegetables (it is still in the registration phase in Brazil). Chinese scientists point out that recent reports have demonstrated significant efficacy of tetraniliprole against notorious pests such as Spodoptera frugiperda e Agrotis ipsilon. However, few results have been published on the development of resistance to tetraniliprole in Absolutely all. Widespread application or successive selections of tetraniliprole against primary lepidopteran pests, including Cnaphalocrocis medinalis, C. suppressalis e S. exigua, could accelerate the development of resistance.
Researchers monitored the susceptibility of Absolutely all to tetraniliprole in 18 field populations from northern China. The Huailai population showed 36,2-fold greater resistance to tetraniliprole compared to the susceptible YN-S strain. Additional testing revealed that this population also exhibited cross-resistance to chlorantraniliprole (12,2-fold) and flubendiamide (6,7-fold), but little resistance to other insecticides such as broflanilide, spinosad, metaflumizone, and indoxacarb.
Genetic analyzes indicated that resistance to tetraniliprole in the HL population is:
(a) autosomal (males and females have the same chance of inheriting resistance genes);
(c) incompletely dominant (a single resistance allele, received from one of the parents, is not sufficient to confer complete resistance to the insecticide);
(c) polygenic (resistance is controlled by several different genes, each contributing a little. This characteristic generates great variability in the insect population in relation to the level of resistance, even among individuals of the same species).
Furthermore, the scientists explain, the enzymatic activity of P450 monooxygenase and glutathione S-transferase was significantly higher in the resistant population compared to the susceptible one.
P450 monooxygenase is responsible for metabolizing several substances, including insecticides; glutathione S-transferase (GST) binds to insecticide molecules and neutralizes their toxins, allowing the insect organism to eliminate them safely.
The development of resistance to tetraniliprole by Absolutely all highlights the urgent need to implement effective resistance management strategies. A practical approach is to rotate insecticides with different modes of action to reduce selective pressure on a single insecticide. Genetic and cross-resistance studies are essential to understand and slow the evolution of resistance.
Increasing metabolic detoxification is one of the main mechanisms of insecticide resistance in several pests. The study revealed that combined treatment with piperonyl butoxide increased the toxicity of tetraniliprole, indicating that P450 detoxification plays a role in resistance. The elevated enzyme activity in the resistant population suggests that resistance to tetraniliprole may be partially attributed to metabolic detoxification.
The discovery that resistance to tetraniliprole in Absolutely all is polygenic and incompletely dominant suggests that the evolution of resistance may be slow but persistent, making resistance management an ongoing challenge. It is crucial that researchers continue to monitor pest susceptibility and develop new integrated pest control approaches.
Tetraniliprole (tetraniliprole, C22H16ClF3N10O2, CAS 1229654-66-3, IRAC 28), a relatively new insecticide from the diamide class, acts, in simple terms, as follows…
• Prohibited: tetraniliprole enters the pest's body through ingestion or contact.
• Target: the pesticide travels to the ryanodine receptors located in the membranes of the endoplasmic reticulum.
• Connection: tetraniliprole binds to ryanodine receptors.
• Disturbance: The binding of tetraniliprole to ryanodine receptors disrupts the delicate balance of calcium flow within cells. Calcium, an essential signal for several cellular functions, becomes unregulated, throwing the cell into chaos.
• Paralysis: Calcium dysregulation leads to uncontrolled muscle contraction and paralysis. The pest is unable to move, feed or defend itself.
• Death: Without the ability to perform basic functions, the pest succumbs to multiple organ failure and dies.
The full study can be read at doi.org/10.1016/j.pestbp.2024.106019
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