1a. Objectives (from AD-416)
The goal of this research is to systematically demonstrate complete ACP mortality over the course of harvesting, packing, and shipping periods of fresh California citrus destined for Australia.
1b. Approach (from AD-416)
Phase 1 (year 1) Objective: Design, refine and execute experiments that allow ACP population densities to be traced through chemical and physical processes that are consistent with CA citrus production and distribution to Australian markets. Specifically, we will test the following hypotheses: a) Commercial harvesting, cleaning, and packing practices effectively remove or kill all ACP life stages. b) ACP life stages cannot survive a simulated shipping scenario at 3 - 6 C for greater than 14d, even with potential food sources present. c) ACP mortality outcomes in a) and b) above are not statistically affected by citrus fruit age, species, and variety. Phase 2 (year 2) Objective: Quantitatively monitor ACP population density and mortality as infested citrus fruit is harvested, cleaned, packed, and shipped to Australian ports (simulation). Specifically, we will test the following hypotheses: d) ACP population densities in the field have no statistical effect on mortalities observed in a-c above). e) ACP mortalities observed in a-d) above are consistent between packing houses and shipping companies involved in the export of CA citrus to Australia.
3. Progress Report
This Trust agreement was established to support Objective 1 of the in-house project and is related to finding methyl bromide alternatives for postharvest applications. The Asian citrus psyllid is a quarantine pest of citrus. Soak tanks and wash lines consistent with commercial cleaning and packing protocols of California were used to demonstrate that adult Asian citrus psyllids are completely washed from citrus fruit that is submerged, flooded, or sprayed at high-pressures (~200 psi) and nearly 99% remain trapped by the solution until they drown or drain. Probit 9 level mortality (99.9968%) of adult Asian citrus psyllid was observed after >3.3 min exposure to forced-air at temperatures used in commercial dryers (118-138F). The cumulative effect of consecutive “systemic” postharvest cleaning and packing elements on the removal and mortality of Asian citrus psyllid was demonstrated by calculating joint probabilities. For example, if infested fruit is first run over a 6ft span of brushes before drying, independent from washing, the joint probability estimate of Probit 9 security is achieved with a reduced exposure of ~2.7 min. The use of washing procedures, including dunking, flooding, and high-pressure spraying as part of cleaning and packing protocols results in “Asian citrus psyllid-free fruit”, as there is zero joint probability of Asian citrus psyllid remaining on the fruit surface, irrespective of orange cultivar.