A field study investigating the insecticidal efficacy against Diaphorina citri Kuwayama on Kinnow mandarin, Citrus reticulata Blanco trees

Thirty-minute test to detect insecticide resistance under field conditions: the case of the Asian citrus psyllid

BACKGROUND

Diaphorina citri Kuwayama is one of the most destructive citrus pests worldwide. It is controlled mainly through applications of conventional insecticides. Methodologies used to estimate resistance to insecticides do not correlate with field efficacy, and do not provide timely and reliable information to make decisions at a site where spraying is needed. The use of diagnostic doses with 30-min exposure is proposed for estimating the resistance of D. citri to imidacloprid, spinosad, malathion and chlorpyrifos at the orchard level.

RESULTS

Under laboratory conditions, we estimated the lowest doses that caused 100% mortality within 30 min of exposure (diagnostic dose) in a susceptible D. citri colony. The diagnostic doses for imidacloprid, spinosad, malathion and chlorpyrifos were 7.4, 4.2, 1.0 and 5.5 mg a.i. L-1 , respectively. Under field conditions, we applied the diagnostic doses to D. citri feeding on Citrus aurantifolia Swingle at five localities in Michoacan state, Mexico (Nueva Italia, Santo Domingo, El Varal, Gambara and El Ceñidor). Additionally, the field efficacy of these insecticides against these populations was evaluated. A significant correlation between field efficacy and mortality was observed with the diagnostic doses for imidacloprid, malathion and chlorpyrifos (R2  ≥ 0.93). The correlation for spinosad could not be estimated because the mortality caused by the diagnostic dose and its field efficacy at all study sites was consistently >98%.

CONCLUSIONS

Field efficacy and resistance were estimated based on the field diagnostic doses with 30-min exposure for all tested insecticides. Consequently, growers and pest management technicians can estimate the performance of the evaluated insecticides at the orchard level and before insecticide application. © 2023 Society of Chemical Industry.

Residual Behavior and Dietary Risk Assessment of Chlorfenapyr and Its Metabolites in Radish

Chlorfenapyr, as a highly effective and low-toxicity insect growth regulation inhibitor, has been used to control cross-cruciferous vegetable pests. However, the pesticide residue caused by its application threatens human health. In this paper, the residue digestion and final residue of chlorfenapyr in radish were studied in a field experiment. The results of the dynamic digestion test showed that the half-life of chlorfenapyr in radish leaves ranged from 6.0 to 6.4 days, and the digestion rate was fast. The median residual values of chlorfenapyr in radish and radish leaves at 14 days after treatment were 0.12 and 3.92 mg/kg, respectively. The results of the dietary intake risk assessment showed that the national estimated daily intake (NEDI) of chlorfenapyr in various populations in China were 0.373 and 5.66 µg/(kg bw·d), respectively. The risk entropy (RQ) was 0.012 and 0.147, respectively, indicating that the chronic dietary intake risk of chlorfenapyr in radish was low. The results of this study provided data support and a theoretical basis for guiding the scientific use of chlorfenapyr in radish production and evaluating the dietary risk of chlorfenapyr in vegetables.

Lethal and sublethal effects of emamectin benzoate on life-table and physiological parameters of citrus red mite, Panonychus citri

The citrus red mite (Panonychus citri) is a challenge to manage in citrus orchards due to resistance against several pesticides. There is a necessity therefore to find new pesticides for effective control of P. citri. This study was designed to evaluate the lethal and sublethal effects of emamectin benzoate against P. citri. The results showed that the LC50 of emamectin benzoate to adults of P. citri was 0.35 (0.26-0.43) mg a.i. L-1 and the LC90 was 1.44 (1.16-1.96) mg a.i. L-1. The sublethal concentration exposures (LC10 and LC30) had a significant negative impact on the larval, protonymph, and deutonymph developmental periods. Male longevity was much lower in LC30 treatments than in the controls. Although female longevity was unaffected, the fecundity (eggs per female) was decreased in the sublethal concentration treatments. Results revealed that the adult pre-oviposition period (APOP) and total pre-oviposition period (TPOP) were increased. Other growth parameters r, λ, and R0 decreased, whereas mean generation time (T) increased due to pesticide exposure. The survival rate (Sxj), age-specific fecundity and net maternity, life expectancy (Exj), and reproduction (Vxj) was reduced by LC10 and LC30 exposure. An increase in malondialdehyde (MDA) contents with increasing emamectin benzoate concentration demonstrates that emamectin benzoate induces oxidative stress in P. citri. The activity of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT) was decreased due to LC30 and LC10 treatments compared to the control. Detoxification enzyme activity (cytochrome P450, glutathione-S-transferases, GST and acetylcholinesterase, AChE) was increased in treated mites compared to the control. This study demonstrates that emamectin benzoate has both a lethal effect on citrus red mite and sublethal effects on its biology and physiology. It is, therefore, potentially an effective pesticide for management of P. citri.

Citrus Genus and Its Waste Utilization: A Review on Health-Promoting Activities and Industrial Application

Citrus fruits such as oranges, grapefruits, lemons, limes, tangerines, and mandarins, whose production is increasing every year with the rise of consumer demand, are among the most popular fruits cultivated throughout the globe. Citrus genus belongs to the Rutaceae family and is known for its beneficial effects on health for centuries. These plant groups contain many beneficial nutrients and bioactive compounds. These compounds have antimicrobial, anticancer, antidiabetic, antiplatelet aggregation, and anti-inflammatory activities. Citrus waste, generated by citrus-processing industries in large amounts every year, has an important economic value due to richness of bioactive compounds. The present review paper has summarized the application and properties of Citrus and its waste in some fields such as food and drinks, traditional medicine practices, and recent advances in modern approaches towards pharmaceutical and nutraceutical formulations.

Quantification of insecticide spatial distribution within individual citrus trees and efficacy through Asian citrus psyllid reductions under different application methods

BACKGROUND

Citrus greening disease (Huanglongbing, HLB) has infected >90% of Florida's oranges and thus growers are desperate to improve pest management strategies. In this field study, insecticide application efficacy was investigated with liquid chromatography mass spectrometry to determine if insecticide concentration and distribution were effective at killing the target pest Asian citrus psyllids (ACP). Sample discs attached to leaves were sprayed with imidacloprid and malathion at a field site in Florida. Application method, canopy height and depth, cardinal side of tree, and leaf side were considered to assess the spatial distribution of insecticides throughout citrus trees. Furthermore, ACP were inspected before and after insecticide applications to quantify psyllid population response.

RESULTS

Our findings show that although insecticide concentrations were high enough to kill ACP, the spatial distribution of insecticides throughout individual trees was highly variable and live ACP were detected after insecticide application. The top side of leaves received significantly more insecticide than the underside of leaves. Additionally, inadequate distribution to different areas of the tree canopy was observed for all application methods tested (aerial, ground speed-sprayer, and ground side-sprayer). Inspections of ACP populations before and after insecticide applications resulted in reductions of 85% (malathion) and 48-80% (imidacloprid).

CONCLUSIONS

The variability in insecticide spatial distribution due to application method allows remaining ACP to continue spreading citrus greening disease to unprotected trees. Further research is needed to improve insecticide application methods and technology for citrus trees in order to implement effective pest management strategies and fully target ACP to eliminate HLB. © 2020 Society of Chemical Industry.