Acaricidal activity of natural monoterpenes on Tyrophagus putrescentiae (Schrank), a mite of stored food

Seven natural monoterpenes (pulegone, eucalyptol, linalool, fenchone, menth one, alpha -terpinene and gamma -terpinene), out of 13 tested, were shown t o possess a high acaricidal activity by vapour action against mobile stages of Tyrophagus putrescentiae. Of these seven, pulegone, menthone, linalool, and fenchone yielded LC90 values of 14 mul/l or below. However, no effect was recorded on egg hatching. Interestingly, the larvae and males of T. put rescentiae presented a mortality rate significantly higher than females (ab out 2-fold) when exposed to the same vapour concentration of the active mon oterpenes. The high acaricidal activity recorded on immature and adult stag es might be primarily related to desiccation, since dead mites presented sy mptoms usually considered to be associated with this phenomenon. Moreover, since larvae and males are significantly smaller than females and their sur face/volume ratios are higher, they tend to lose relatively more water, thu s supporting the notion that the greater acaricidal activity recorded on la rvae and males might be primarily related to desiccation. Nevertheless, act ion by interference with respiratory processes cannot be discarded. The pot ential of these natural monoterpenes for practical use against mobile stage s of T. putrescentiae in warehouses of traditional Spanish dry-cured ham is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.