Use of systemic insecticides reduces HLB transmission by up to 60%

The application of systemic insecticides with a drench or through trunk injections reduces the numbers of the psyllid Diaphorina citri, a transmitter of Huanglongbing (HLB), feeding on citrus seedlings, by up to 90% and can reduce the transmission of the HLB bacteria by up to 60%. This was discovered in research by the Citrus Plant Protection Fund (Fundecitrus), which evaluated the influence of this kind of agrochemical on the psyllids' behavior. The study was coordinated by the researcher Marcelo Pedreira de Miranda.

The evaluations were performed with the use of an electrical penetration graph, a tool that electronically monitors the activities of the psyllids in real time. Days after the application of the systemic insecticide, the seedlings were taken to the Fundecitrus laboratory for evaluation. The results of the analysis showed that the number of feeding psyllids had reduced by 90% in plants treated with neonicotinoid insecticides compared with the control, which had not been treated.

"The change in feeding habits occurs because when it sucks the sap of the treated plant, the psyllid perceives the difference and stops consuming the sap. This leads to the drop in bacterial transmission, which occurs during feeding,” noted Miranda.

To confirm these results in the field, further studies were developed. The initial data revealed a reduction of up to 60% in the incidence of plants with HLB in treated areas, combined with foliar spraying, compared with areas that received only foliar applications. “The difference between the lab and field test results occurs because the treated seedlings are exposed to the insects for a shorter period in the lab and a higher concentration of agrochemicals is used compared with plants in the field,” the researcher explained.

Miranda said the systemic insecticide had positive effects because of the action within the plants. Applications via drench, allowing the insecticide to be absorbed by the roots, and trunk injections both help the insecticide spread quickly through the plant. “Because of this style of application, external factors such as rain and high temperatures do not reduce the agrochemical's contact with the insect. Besides, it protects the shoots more because when the insecticide penetrates the plants, it mostly reaches those parts, which are preferred by the psyllid for feeding,” remarked Miranda.