IMPACT OF RAINFALLS ON THE ACARICIDE PROPARGITE WITH AND WITHOUT ADDITION OF ADJUVANTS FOR THE CONTROL OF THE MITE Brevipalpus yothersi

Abstract

Rainfalls may affect the efficiency of pesticides due to a decreased deposit of active ingredient on plants. This should be considered in spraying with acaricides, the main strategy used for the management of citrus leprosis, the main viral disease of the Brazilian citrus culture. Citrus leprosis disease is transmitted by Brevipalpus mites, mainly B. yothersi. The objective of this study was to evaluate the effects of artificial rains on the efficiency of the acaricide propargite in combination or not with adjuvants for the control of the mite B. yothersi. The experiment was conducted using orange plants grown in pots kept under greenhouse conditions. The acaricide propargite was evaluated isolated and with addition of the adjuvants polydimethylsiloxane (20mL cp/100 L of water) and a mixture of phosphatidylcholine (lecithin) and propionic acid (500 mL cp/100 L of water). After the application of the acaricide with and without the adjuvants, the plants were subjected to a 10-mm artificial rainfall at different time intervals: 5 minutes, and 1 and 12 hours after application. Thereafter, B. yothersi mites were transferred to plants for survival evaluation. The artificial rainfall affected negatively the efficiency of propargite isolated and in mixture. The addition of the adjuvant phosphatidylcholine and propionic acid impaired the efficiency of propargite due to an increased runoff of the broth and a decrease in the deposit of active ingredients on plants. We conclude that the acaricide propargite should not be used in combination with the adjuvants polydimethylsiloxane and mixture of phosphatidylcholine and propionic acid in rainy conditions.

Adjuvants plus phytosanitary products and the effects on the physical-chemical properties of the spray liquids

“…However, Sanches et al (2018) evaluating an adjuvant based on lecithin + propionic acid showed that the drastic change in the pH of the spray solution caused by this product can be associated with the reduction in the effectiveness of pest control in citrus. Therefore, it is necessary to analyze the optimal pH range for each phytosanitary case in order to verify their compatibility with the adjuvant.…”

“…Studies show that this adjuvant has as main characteristic the drift reduction due to an increase in the size of droplets generated during the applications (ALVES et al, 2018;ROSS Jr. et al, 2018). However, adverse effects from the use of this compound were observed by Sanches et al (2018), such as a reduction in the effectiveness of the acaricide when used with this adjuvant.…”

The importance of acaricides in the control of citrus leprosis mite and factors that interfere with the efficacy

“…However, more studies should be conducted to verify whether this same result is observed when mites are exposed to successive insecticide sprayings, a common practice in the Brazilian citrus groves. polydimethylsiloxane, associated with the propargite acaricide, did not increase the control efficiency of B. yothersi (Sanches et al, 2018). Decaro et al (2016) observed that adding polydimethylsiloxane to propargite solution resulted in greater spray solution deposit on citrus leaves, while spirodiclofen the mixture with polydimethylsiloxane or phosphatidylcholine adjuvants reduced spray solution deposit, which possibly would result in lower acaricide efficiency in the leprosis mite control.…”