Walker, G.P., Zareh, N., & Arpaia, M.L. 1999 Effect of pressure and dwell time on efficiency of a high-pressure washer for postharvest removal of California red scale (Homoptera : Diaspididae) from citrus fruit.. Biocontrol Dordecht 44(1): 47-58.

Notes: The most common economic injury caused by California red scale, Aonidiella aurantii (Maskell), to citrus is downgrading of fruit caused by the presence of scale on the fruit. In the packinghouse, scale can be removed from fruit by subjecting the fruit to high-pressure water sprays that physically dislodge the scale. In this study, we evaluated a FMC Freshgard 4000 washer at several pressures and dwell times (the time from when a fruit enters the high-pressure washer to when it exits) for scale removal. Removal of total scale (live and dead) at 22.1, 13.6, and 10.2 atmospheres was 97-99.9, 95-98, and 97%, respectively. Live scale (which comprised 13-21% of scale on fruit before treatment) were more difficult to remove by high-pressure washing than dead scale. Removal of live scale at 22.1, 13.6, and 10.2 atmospheres was 93-99.7, 88-97, and 92% of live scale, respectively. The previously recommended pressure was 22.1 atmospheres, but results of this study support changing the recommended pressure to 10.2-13.6 atmospheres because the washer is almost as effective at these pressures as it is at 22.1 atmospheres. The advantage of slightly greater scale removal at 22.1 atmospheres compared with 13.6 and 10.2 atmospheres is offset by greater probability of causing economically significant injury to the fruit at higher pressures. Dwell time also affected scale removal. As dwell time increased 2.3-fold from 10-23 s, the number of scale remaining decreased by 6.1-fold.