Psyllids collected in orchards in four microregions of Brazil’s citrus belt showed reduced susceptibility to insecticides from the pyrethroid and neonicotinoid chemical groups. That information was reported earlier this year by agronomist and researcher Fernando Amaral of the Arthropod Resistance Laboratory at the Luiz de Queiroz College of Agriculture/University of São Paulo (ESALQ/USP).
This was the first confirmation of psyllid resistance in Brazil. But Amaral said 123 cases of psyllid resistance have been identified elsewhere in the world, for nine different active ingredients. This situation has been previously observed in groves in Florida, Mexico, China and Pakistan.
The studies were coordinated by Celso Omoto, head professor of the Department of Entomology and Acarology at ESALQ/USP, 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,” Amaral said.
TEMPORARILY DISCONTINUE USE
For psyllid control to be effective in stopping the spread of HLB disease, it is important that there is no selection of resistant psyllids — individuals capable of surviving applications of a certain insecticide and passing this characteristic on to their descendants. Therefore, according to Omoto, growers need to temporarily discontinue the use of pyrethroids and neonicotinoids as soon as control failures are observed.
“On an emergency and temporary basis, it is essential to avoid the use of insecticides from these two chemical groups until the psyllids’ susceptibility to these products is reestablished,” said Omoto.
ROTATE INSECTICIDES
“Furthermore, to prevent psyllids from becoming resistant to other chemical groups, it is essential that insecticides with at least four different chemical groups be rotated, without sequential applications of insecticides from the same chemical group,” Omoto said.
Growers can use insecticides from chemical groups little used in citriculture.
“These actions must be carried out by all producers in the region to be more effective,” Omoto added.
In regions where producers jointly performed insecticide rotation and avoided the use of products from these chemical groups with verified resistance, the psyllid population reduced significantly.
Source: Fundecitrus
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