Freeze Mortality Characteristics of the Mold Mite Tyrophagus putrescentiae, a Significant Pest of Stored Products

Abstract

The mold mite Tyrophagus putrescentiae (Shrank) is a common pest of stored food products. Until recently, commodity and facility treatments have relied on acaricides and fumigants to control this mite. However, T. putrescentiae will cause infestations in areas where acaricide or fumigant use may be restricted, prohibited, or highly impractical. Because temperature is an essential factor that limits the survival of arthropod species, extreme temperatures can be exploited as an effective method of control. Making low-temperature treatments reliable requires better temperature-time mortality estimates for different stages of this mite. This was accomplished by exposing a representative culture (eggs, nymphs, and adults) of noncold-acclimated T. putrescentiae to subfreezing temperatures to determine their supercooling points (SCPs), lower lethal temperatures (LLTs) and lethal times (LTimes) at set temperatures. The results indicate that the adult and nymphal stages of T. putrescentiae are freeze intolerant; based on 95% CIs, the adult LLT90 of -22.5 degrees C is not significantly different from the SCP of -24.2 degrees C and the nymphal LLT90 of -28.7 degrees C is not significantly different from the SCP of -26.5 degrees C. The egg stage seems to be freeze tolerant, with an LLT90 of -48.1 degrees C, significantly colder by approximately 13.5 degrees C than its SCP of -35.6 degrees C. The LTime demonstrates that 90% of all mite stages of T. putrescentiae can be controlled within commodity or packaged product by freezing to -18 degrees C for 5 h. By achieving the recommended time and temperature exposures, freezing conditions can be an effective way of controlling mites and reducing chronic infestations.

Cold Tolerance of Bed Bugs and Practical Recommendations for Control

“…However, based on the SCP and LLT estimates reported here and by Benoit et al (2009), bed bugs are not freeze tolerant because LLT mortality data were within the 95% CI for the SCP estimates (Lee et al 1992). Freeze tolerance would have been suspected if the SCP was substantially higher than the LLT estimates (Bouchard et al 2006) or if a signiÞcant proportion of individuals survived temperatures below the SCP estimate (Eaton and Kells 2011).…”

“…This type of variability has previously occurred in nonchemical control with mold mites (Eaton and Kells 2011) and webbing clothes moths (Brokerhof et al 1992). This variability may be a factor of target site nonspeciÞcity of cold injury and the diversity of physiological, biochemical, and gross anatomical systems that may be affected by cold temperatures as described in more detail by Teets and Denlinger (2013).…”

“…Eggs were set up in a similar manner and collected as previously described. Temperatures within the vials were recorded with a 24 gauge copperconstantan thermocouple (Eaton and Kells 2011). For each exposure, vials containing speciÞc Stages and Fed Status were randomly assigned to temperatures: 0, Ϫ5, Ϫ10, Ϫ15, Ϫ20, Ϫ25, Ϫ30, Ϫ35, and Ϫ40ЊC.…”

“…Therefore, only eggs and unfed Þrst instars were used in the second CCD to limit the number of treatments. For the second CCD data set, unfed Þrst instars and eggs (0 Ð7 d old) were housed in 1.5-ml centrifuge tubes (Fisher, Pittsburg, PA) and placed within an aluminum heating block (described in more detail by Eaton and Kells 2011) to maintain precise temperature settings (within 1Ð2ЊC) throughout the duration of the experiment.…”

Efficacy and Application Considerations of Selected Residual Acaricides Against the Mold Mite <I>Tyrophagus putrescentiae</I> (Acari: Acaridae) in Simulated Retail Habitats

“…Mold mites, T. putrescentiae, were reared in 0.946-liter Mason jars (Jarden Home Brands, Daleville, IN) on semimoist dog food (Eaton and Kells 2011). Jar lids were replaced with mesh screen with Þlter paper (P5, Fisher, Pittsburgh, PA) on both sides of the screen to provide ventilation.…”