Inheritance, Fitness Cost, and Management of Lambda-Cyhalothrin Resistance in a Laboratory-Selected Strain of Ceratitis capitata (Wiedemann)

SIMPLE SUMMARY: The Mediterranean fruit fly (medfly), Ceratitis capitata, is considered one of the most destructive and economically damaging pests of citrus and other fruit crops worldwide. Current control practices in Spain rely on the use of insecticides (mainly lambda-cyhalothrin, spinosad, and deltamethrin) and the release of sterile males. However, the sustainability of medfly control programs is threatened by reports of resistance to lambda-cyhalothrin in field populations. In this work, we used a laboratory-selected lambda-cyhalothrin-resistant strain to study key factors required for devising effective insecticide resistance management strategies. Specifically, we have (1) determined that the inheritance of resistance is autosomic (non-associated to the sexual chromosome), completely dominant (a single copy of the gene is enough to confer resistance), and polygenic (controlled by more than one gene); (2) observed that resistant individuals present fitness alterations in regard to biological parameters (lower survival in the first growth stages, a slower developmental time, and higher adults’ weight and longevity); and (3) shown under laboratory conditions that the alternation of lambda-cyhalothrin with spinosad helped delay the development of resistance. Taken together, our results indicate that it would be advisable to encourage the rotation of these insecticides to manage the resistance problem. ABSTRACT: The management of the medfly, Ceratitis capitata, in Spanish citrus crops relies mainly on the use of insecticides and the release of sterile males. However, the development of resistance to different insecticides in field populations, including lambda-cyhalothrin, implies a threat for the sustainable control of this pest. The inheritance, fitness cost, and management of lambda-cyhalothrin resistance were examined in the laboratory-selected W-1Kλ strain. We have demonstrated that lambda-cyhalothrin resistance in W-1Kλ is autosomic, completely dominant, and polygenic. In addition, individuals from W-1Kλ showed a lower embryo to pupal viability, a slower developmental time from egg to pupae, and an increase in adults’ weight and longevity. We did not find significant trade-offs in the activity of digestive hydrolytic enzymes, with the exception of higher α-amylase activity in W-1Kλ females. A comparative study with different insecticide treatment strategies showed that lambda-cyhalothrin resistance increased when several consecutive treatments with this insecticide were applied. However, the alternation of this insecticide with spinosad was enough to delay the development of resistance. Our results indicate that the rotation of lambda-cyhalothrin with spinosad—a practice already used in some fields—may contribute to prevent the development of resistance.