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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Publications at this Location » Publication #162402
Title: HEATING CONDITION EFFECTS ON THERMAL RESISTANCE OF FIFTH-INSTAR NAVEL ORANGEWORM (LEPIDOPTERA: PYRALIDAE)

Author
item WANG, SHAOJIN - WASHINGTON UNIV
item Johnson, Judy
item TANG, JUMING - WASHINGTON UNIV
item YIN, X - WASHINGTON UNIVERSITY

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2004
Publication Date: 5/1/2005
Citation: Wang, S., Johnson, J.A., Tang, J., Yin, X. 2005. Heating condition effects on thermal resistance of fifth-instar navel orangeworm (lepidoptera: pyralidae). Journal of Stored Products Research. 41(4):469-478.

Interpretive Summary: Navel orangeworm is a major insect infesting California tree nuts (walnuts, almonds and pistachios) in the field. Methyl bromide fumigation of tree nuts is widely used to meet commercial phytosanitary requirements. However, recent legislation calls for halting the manufacture and use of methyl bromide by the year 2005, generating a need for alternative treatments. Radio frequency heat treatments, alone or in combination with hot forced air, have been suggested as an alternative to fumigants, and it is desirable to understand the effect that different heating rates and preconditioning temperatures may have on the effectiveness of the treatment. Also, the difference between long-term laboratory cultures and recently isolated cultures of test insects must be determined. Laboratory studies using heating blocks to deliver carefully controlled heating rates to fifth instar navel orangeworm found that there was no significant difference in insect mortality resulting from heating rates of 10 and 15 degrees C/minute. The mean mortality at the heating rate of 1 degree C/minute was significantly lower than for faster heating rates (10 and 15 degrees C/minute) only at a single treatment combination. The pretreatment conditioning of fifth-instar navel orangeworm at 30 degrees C for 6 hours enhanced their thermotolerance. Fifth instars from long-term laboratory cultures had at least equal heat resistance to fifth instars from recently isolated cultures. Thus, thermal death kinetic information obtained from the long-term laboratory cultures can be used to develop thermal protocols.

Technical Abstract: Successful development of a thermal treatment protocol can be facilitated with reliable information on fundamental thermal death kinetics of targeted insects under different heating conditions. The effects of heating rates (1, 10 and 15 degrees C/minute), pretreatment conditioning (30 degrees C + 6 hours), and the difference between long-term laboratory cultures and recently isolated cultures on thermal mortality of fifth-instar navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), were studied using a heating block system. There was no significant difference in insect mortality resulting from heating rates of 10 and 15 degrees C/minute. Temperature control at 1 degree C/minute was more uniform than for the other heating rates, resulting in reduced variability for insect mortality. The mean mortality at the heating rate of 1 degree C/minute was significantly lower than for faster heating rates (10 and 15 degrees C/minute) only at 48 degrees C + 30 minute. The pretreatment conditioning of fifth-instar navel orangeworm enhanced their thermotolerance. Fifth instars from long-term laboratory cultures had at least equal heat resistance to fifth instars from recently isolated cultures. Thus, thermal death kinetic information obtained from the long-term laboratory cultures can be used to develop thermal protocols.