Author: Joseph Morse and Richard Stouthamer

Between 1914 and 2007, a quarantine protected California avocado groves from pests that might be introduced into the state along with fresh, imported avocados. Soon after Mexican avocados were first allowed entry on 1 February 2007, live specimens of several species of armored scales (Family
Diaspididae) not believed to be present in California were detected on Hass avocados entering the state from Mexico. In order to determine if this was a dangerous situation, we examined fruit entering California via the Blythe border station and found eight species of scales, seven of which are believed
to be exotic to the state (Morse et al. 2009). Over an 8-month period, September 2007 - April 2008, we estimated that 67 million Mexican Hass avocados entered California and based on samples from 140 trucks containing 15.6% of the total volume of fruit entering the state, approximately 47.6 million live,
sessile scales (first instars and older that can’t move from where they are attached; including females which can produce more crawlers) and an additional 20.1 million live eggs and crawlers (the life stages that can establish new populations; some species produce eggs and other species hatch eggs internally and birth live crawlers) were imported. The only species found on Mexican avocados believed to already be present in California was latania scale (Hemiberlesia lataniae), which is a parthenogenetic species (females only). Interestingly, latania scale was relatively rare on Mexican avocados but a common species (and one that was previously unknown) was the very similar Hemiberlesia sp. near lataniae, which is a sexually reproducing species. The other 6 exotic species
found were Abgrallaspis aguacatae, Abgrallaspis perseae, Acutaspis albopicta, Diaspis miranda, Diaspis sp. near miranda, and Pinnaspis strachani.