Research confirms resistance of psyllids to pyrethroids and neonicotinoids

Insecticides based on the active ingredients bifenthrin and imidacloprid are no longer effective in controlling the insect that transmits greening in some locations and should be temporarily avoided if control failures are observed after their use.

01.06.2023 | 15:30 (UTC -3)
fundecitrus
Insecticides based on the active ingredients bifenthrin and imidacloprid are no longer effective in controlling the insect that transmits greening in some locations and should be temporarily avoided if control failures are observed after their use.
Insecticides based on the active ingredients bifenthrin and imidacloprid are no longer effective in controlling the insect that transmits greening in some locations and should be temporarily avoided if control failures are observed after their use.

Psyllids collected in orchards in four microregions of the citrus belt of São Paulo and Triângulo and Southwest of Minas Gerais showed a reduction in their susceptibility to insecticides from the pyrethroid and neonicotinoid chemical groups. The information was released on Thursday afternoon (01/06) by the agronomist and researcher at the Arthropod Resistance Laboratory at Esalq/USP Fernando Amaral, in the lecture "Relevance of insecticide rotation in the management of the citrus psyllid to maximize effectiveness and minimize resistance", given at the 44th Citrus Week - 48th Expocitros, at the "Sylvio Moreira" Citriculture Center (IAC), in Cordeirópolis (SP).

In the lecture, Amaral said that 123 cases of psyllid resistance have already been identified in the world, to nine different active ingredients. This situation has already been observed in orchards in Florida (USA), Mexico, China and Pakistan and is now confirmed for the first time in Brazil. The studies were coordinated by the professor of the Department of Entomology and Acarology at Esalq/USP Celso Omoto, with samples from the microregions of Novo Horizonte (Northwest), Bebedouro (North), Santa Cruz do Rio Pardo (Southwest) and Limeira (South). "The reduction in susceptibility is mainly due to the high frequency of use of insecticides from the same chemical group without the correct rotation", explains Amaral.

What to do?

The fight against greening is structurally based on the so-called management tripod, which consists of planting healthy seedlings, eliminating diseased plants and controlling the psyllid. For psyllid control to be effective, it is important that there is no selection of resistant psyllids, that is, individuals capable of surviving applications of a certain pesticide and passing this characteristic on to their descendants. Therefore, according to the study coordinator, Celso Omoto, pyrethroids and neonicotinoids, at this moment, as soon as control failures are observed, need to temporarily leave the citrus grower's list of options to control the insect.

"On an emergency and temporary basis, it is essential to avoid the use of insecticides from these two chemical groups until the susceptibility of psyllids to these products is reestablished", says Omoto. "Furthermore, to prevent psyllids from developing resistance to other chemical groups, it is essential to rotate insecticides with at least four different chemical groups, without sequential applications of insecticides from the same chemical group. It is recommended still use insecticides from chemical groups little used in citrus farming. These actions must be carried out by all producers in the region to be more effective", he adds.

In regions where producers jointly rotated insecticides and avoided the use of products from these chemical groups with verified resistance, the psyllid population reduced significantly.

LS Tractor February