Article

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

USDA-ARS Western Cotton Laboratory, 4135 E Broadway Road, Phoenix, AZ 85040, USA.
Pest Management Science (Impact Factor: 2.74). 02/2005; 61(1):75-84. DOI: 10.1002/ps.949
Source: PubMed

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.

1 Bookmark
 · 
93 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Select populations of Colorado potato beetle, Leptinotarsa decemlineata, in Wisconsin have recently become resistant to soil-applied neonicotinoids in potato. Sub-lethal insecticide concentrations persisting in foliage through the growing season may select for resistance over successive years of use. Over the two years of this study, our aim was to document the in-plant insecticide concentrations over time resulting from four different types of soil-applied insecticide delivery for thiamethoxam and imidacloprid in potato and to measure the impact upon L. decemlineata populations following treatments. After plant emergence, insect life stages were counted and plant tissue was assayed weekly for nine consecutive weeks using ELISA. Peak concentration of both imidacloprid and thiamethoxam occurred in the first sample week following plant emergence. Average concentration of both insecticides dissipated sharply over time as the plant canopy expanded 50 days after planting in all delivery treatments. Both insecticides were detected at low levels during the later weeks of the study. Among plant concentrations of both neonicotinoids were highly variable throughout the season. Populations of L. decemlineata continued to develop and reproduce throughout the period of declining insecticide concentrations. Sub-lethal, chronic exposure to soil-applied systemic insecticides resulting from these delivery methods may accelerate selection for resistant insects in potato.
    Pest Management Science 01/2014; · 2.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The guava-psyllid, Triozoida limbata (Enderlein), is a severe pest of guava orchards, reducing fruit production. This communication shows the results of an experiment aimed to test nicotinoid insecticides for controlling the guava-psyllid at a high-density level of infestation. Unsatisfactory control of this pest was achieved with imidacloprid AL 100 g/L, at 5, 10 or 20 mL sprayed once onto the guava stem; with imidacloprid SC 200 g/L, at 0.6 mL in 2 L of water/tree and with thiacloprid SC 480 g/L, at 0.2 mL in 2 L of water/tree, both sprayed twice (15 day interval) on the guava foliage. Possible causes of the failure are discussed in relation to several factors, since previous research showed satisfactory control of the guava-psyllid with these insecticides.
    Ciência e Agrotecnologia 01/2009; 33. · 0.40 Impact Factor
  • Value in Health 01/2011; 14(7). · 2.19 Impact Factor

Full-text (2 Sources)

Download
59 Downloads
Available from
May 21, 2014