Diapause disruption with tebufenozide for early-instar control of the spruce budworm, Choristoneura fumiferana.
In North America, the eastern spruce budworm, Choristoneura fumiferana Clem., is an important coniferous pest against which tebufenozide has proven effective as a control product. By acting as an ecdysone agonist, tebufenozide can induce precocious moulting in late (fifth-sixth) instars but can also be carried over to the next generation owing to its persistence on foliage. The authors conducted laboratory experiments on first-instar larvae treated with tebufenozide dissolved in acetone. Larvae exposed to doses equal to or above 0.1 microg cm(-2) displayed precocious moulting in the second instar after hibernaculum spinning, which effectively disrupted diapause. Larger doses induced moulting in first instars. Evidence is provided that this dose-response difference is related to whether or not an effective dose of tebufenozide is ingested by the first instar prior to the peak of moulting hormone (20-hydroxyecdysone) in first instars. Doses ineffective to kill first instars are carried over to the second instar, where they induce a precocious moult. This type of response to tebufenozide is dependent on the presence of a moulting machinery (the EcR-USP receptor complex) that is ready for ecdysone transduction. Interestingly, ecdysone levels are low in second instars, as measured by a radioimmunoassay, which suggests that diapause in spruce budworm is maintained by a suppression of ecdysone production. Thus, diapause disruption by tebufenozide may well provide an alternative control strategy for this important pest.
Doucet
Daniel
D
Great Lakes Forestry Centre, Natural Resources Canada, Canadian Forest Service, Sault Ste. Marie, Ontario P6A 2E5, Canada. Dan.Doucet@nrcan.gc.ca
Frisco
Caroline
C
Cusson
Michel
M
Bauce
Eric
E
Palli
Subba Reddy
SR
Tomkins
Bill
B
Arif
Basil
B
Retnakaran
Arthur
A
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004440:Ecdysone / Q000378:metabolism; D004441:Ecdysterone / Q000378:metabolism; D015870:Gene Expression; D006834:Hydrazines / Q000494:pharmacology*; D019476:Insect Proteins / Q000378:metabolism*; D007306:Insecticides / Q000494:pharmacology*; D008018:Life Cycle Stages / Q000187:drug effects*; D009036:Moths / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D028222:Picea / Q000469:parasitology; D018010:Receptors, Invertebrate Peptide / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
C104701:CHR3 protein, Choristoneura fumiferana; D004268:DNA-Binding Proteins; D006834:Hydrazines; D019476:Insect Proteins; D007306:Insecticides; D018010:Receptors, Invertebrate Peptide; D015534:Trans-Activators; D004440:Ecdysone; D004441:Ecdysterone; C082026:tebufenozide