Imidacloprid soil movement under micro-sprinkler irrigation and soil-drench applications to control Asian citrus psyllid (ACP) and citrus leafminer (CLM)

Abstract

Imidacloprid (IM) is used to control the Asian Citrus Psyllid (ACP) and citrus leafminer (CLM), which are related to the spread of huanglongbing (HLB or citrus greening) and citrus canker diseases, respectively. In Florida citrus, imidacloprid is mainly soil-drenched around the trees for proper root uptake and translocation into plant canopy to impact ACP and CLM. The objective of this study was to determine the effect of imidacloprid rate, and irrigate amount on concentration of imidacloprid in the soil following drench application to citrus trees in three age classes. The plots were established at the Southwest Florida Research and Education Center, Immokalee, using a randomized complete-block design for three age classes of trees: one-year-old trees (B1), three to five-year-old trees (B2), and eight-year-old trees (B3). The treatments were a combination of two rates each of imidacloprid (1D, 2D) and micro-sprinkling irrigation (1I, 2I). Imidacloprid and bromide (Br-) used as tracer were applied simultaneously. Soil moisture and concentrations of imidacloprid and Br were monitored using soil cores from hand held augers. Soil moisture content (θV) did not differ under two irrigation rates at any given observation day or depth, except following heavy rainfall events. Br- was lost from the observation depths (0–45 cm) about two weeks after soil-drench. Contrarily, imidacloprid persisted for a much longer time (4–8 weeks) at all soil depths, regardless of treatment combinations. The higher retardation of imidacloprid was related to the predominantly unsaturated conditions of the soil (which in turn reduced soil hydraulic conductivities by orders of magnitude), the imidacloprid sorption on soil organic matter, and the citrus root uptake.Findings of this study are important for citrus growers coping with the citrus greening and citrus canker diseases because they suggest that imidacloprid soil drenches can still be an effective control measure of ACP and CLM, and the potential for imidacloprid leaching to groundwater is minimal.

Effect of Systemic Insecticides Applied via Drench on the Mortality of Diaphorina citri on Curry Leaf

“…Another study found a mean lethal concentration of 0.0001 g L −1 for thiamethoxam applied in a liquid diet for insects in the laboratory [26]. Although the LC 50 found by these authors is lower than that in the present study, the application via drench can be affected by other factors, such as heavy rainfall and irrigation systems that can cause soil leaching [43].…”

Control efficacy and joint toxicity of thiamethoxam mixed with spirotetramat against the Asian citrus psyllid, Diaphorina citri Kuwayama

“…Plenty of studies focused on evaluation of control efficacy of many single insecticides via different application methods against ACP have been documented. 19,27,29,30,[53][54][55][56][57][58][59][60][61][62] For example, a single foliar spray of chlorpyrifos, fenpropathrin and oxamyl before spring growth significantly reduced ACP adults at an average of 10-to 15-fold over 5-6 months compared to untreated trees. 61 Pan et al 57 reported that foliar sprays of tolfenpyrad at 50 mg/kg and bifenthrin at 22.5 mg/kg provided excellent control efficacies of 95.3 to 99.8% and 91.3 to 99.1% against ACP within 14 DAT, respectively, which were both greater than those of tolfenpyrad at 50 mg/kg (79.02 to 91.36%) and bifenthrin at 30 mg/kg (82.86 to 91.65%) within 15 DAT, in this study (Table 3).…”

“…At present, neonicotinoids are widely used to sustainably manage ACP because of their key trait of long retention circulating within the vascular system of a citrus tree, 29,30,56,58,59 whose residues can move into new flushes fed preferentially by ACP. Fletcher et al 58 found that significant reductions of ACP population were observed about 2 weeks after imidacloprid soil-drench applications at 550 g/L, and under continued control for 4 to 8 weeks. Cheng et al 35 reported that a thiamethoxam soil-drench application at 100 mg/mL effectively controlled ACP up to 30 DAT, but only for 7 DAT using a dinotefuran foliar spray at 150 mg/mL.…”

“…Application of insecticides is one of the most important tactics for ACP control to minimize infection and spread of HLB in citrus groves. Plenty of studies focused on evaluation of control efficacy of many single insecticides via different application methods against ACP have been documented 19,27,29,30,53–62 . For example, a single foliar spray of chlorpyrifos, fenpropathrin and oxamyl before spring growth significantly reduced ACP adults at an average of 10‐ to 15‐fold over 5–6 months compared to untreated trees 61 .…”

Effect of Microsprinkler Irrigation under Plastic Film on Photosynthesis and Fruit Yield of Greenhouse Tomato

“…It has advantages of decreasing the restriction of horizontal root growth and short irrigation duration [12,13]. For this reason, microsprinkler irrigation has achieved good results with total growth amount and yield in winter wheat, summer corn, lawn, seedlings, and other crops [12,[14][15][16]. However, the shape, area, and uniformity of soil wetting in the microsprinkler irrigation area are affected by wind speed.…”