Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulata populations

Abstract

Titers of two systemic neonicotinoid insecticides in citrus trees were measured in conjunction with conventional evaluations of their impact on glassy-winged sharpshooter (Homalodisca coagulata (Say); GWSS) populations. Xylem fluid samples were collected at regular intervals and from multiple locations within field-grown citrus trees to determine imidacloprid and thiamethoxam concentrations using commercial ELISA kits. Uptake profiles varied considerably with peak mean titers of imidacloprid occurring 6-8 weeks after application compared with 2 weeks for thiamethoxam. The persistence of each compound also varied as near-peak levels of imidacloprid were sustained for another 6-10 weeks before gradually declining. In contrast, thiamethoxam titers declined more rapidly after the initial peak, possibly reflecting an application rate only one-quarter of that used for imidacloprid. Within-tree distributions were more similar for the two compounds, with no significant effect due to height of the sample (upper or lower half) or to the quadrant location within the tree, with the exception of one quadrant in the thiamethoxam-treated trees. Substantial reductions in GWSS nymphs and adults were observed in imidacloprid-treated trees during the 2001 trial and were sustained for 4-5 months after treatment. Treatment effects on nymphs were not as well pronounced in the 2002 trial, when overall GWSS infestations were much reduced from the previous year. However, consistently lower adult infestations were still observed in 2002 for both treatments compared with untreated trees. Information on the spatial and temporal profiles in citrus trees was obtained for both compounds to complement field impact data and improve understanding of their pest management potential.

Efficacy of Neonicotinoid Seed Treatments to Reduce Soybean Aphid Populations Under Field and Controlled Conditions in Nebraska

“…Longer thiamethoxam residual effects relative to imidacloprid have also been observed under laboratory conditions against a number of different insect orders (MaienÞsch et al 2001a). Similar results were documented with the same insecticides applied through the irrigation system for citrus trees, where thiamethoxam controlled glassy-winged sharpshooter, Homalodisca vitripennis (Germar), nymphs better than imidacloprid (Castle et al 2005).…”

“…In soybean, neonicotinoid seed treatments have been used to control early season bean leaf beetles (Cerotoma trifurcata Forster) that vector bean mosaic virus (BMV) (Bradshaw et al 2003); however, they may not impact soybean aphid populations (Johnson et al 2008). The insecticide class also is highly effective for control of various piercing-sucking insects, such as soybean aphid (MaienÞsch et al 2001a, Castle et al 2005, Tomizawa and Casida 2005. Neonicotinoid insecticide seed treatments are increasingly being used in the north central United States, including Nebraska, for management of bean leaf beetle in soybean, and they also have been suggested as a possible control method for this new soybean pest.…”

Effects of Kaolin Particle Film and Imidacloprid on Glassy-Winged Sharpshooter (Homalodisca vitripennis ) (Hemiptera: Cicadellidae) Populations and the Prevention of Spread of Xylella fastidiosa in Grape

“…The epidemic of PD in the vineyards of Temecula in Riverside County, California brought into focus the urgent need to control GWSS populations in CA (Castle et al, 2005) around vineyards. Prior to the first applications of imidacloprid which was made in the spring of 2000 for control of GWSS infestations in Temecula, CA; there had been very limited experience with imidacloprid in citrus or against GWSS in any crop (Catle et al, 2005)).…”

Distribution of Chemical and Microbial Pesticides through Drip Irrigation Systems

“…Soil samples containing Imidacloprid were placed in glass jars, transported to the laboratory, and stored in a freezer at -40 °C until analysis. Methanol was used to extract Imidacloprid from the soil samples (Felsot et al, 1998) and ELISA kits (Envirologix, Inc., Portland, ME, USA) for Imidacloprid were used to determine the amount of Imidacloprid in the soil (Castle et al 2005). Soil samples containing EPF were placed in glass jars, and sent overnight with an ice pack to a laboratory for analysis.…”