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United States Department of Agriculture

Agricultural Research Service

Research Project: Breaking Citrus Trade Barriers using Novel Postharvest Fumigations: High-Concentration Phosphine at Low Temperature (Horn Method)

Location: Commodity Protection and Quality

2011 Annual Report


1a.Objectives (from AD-416)
The goal of this research is to develop chamber fumigations that facilitate the movement of CA citrus through trade and marketing channels. Several contemporary trade barriers restrict, or possess the potential to restrict, foreign commerce of CA citrus, including: red scale to Korea, bean thrips to Australia/New Zealand, and western flower thrips to Taiwan. An additional feature involves the determination of the insecticidal efficacy of Vaporphos to Asian citrus psyllid via collaboration with FL scientists.


1b.Approach (from AD-416)
Quarantine pests related to these trade barriers will be targeted with the Horn method of using high concentration phosphine fumigant, registered in the US as Vaporphos (Cytec), at temperatures that will not break the cold-chain of the fruit in storage (<5 C). This method is being used successfully by our Chilean reciprocal-trade counterparts, albeit on different insect pests, in citrus exports to Korea, New Zealand, Taiwan, and many other countries.


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 dose-mortality of California red scale to ammonia gas was determined. All life stages of scale treated with gaseous ammonia showed no differences in mortality after 24 hours of exposure to ammonia, relative to those evaluated two weeks post-fumigation. In general, a gradual trend in ammonia toxicity was evident across all California red scale life stages; however, at 7500 ppm only 74, 36, and 43% mortality was respectively observed for first instar, third instar female, and gravid females. The 1st instar scale was the most sensitive stage tested, compared to phosphine and methyl bromide where the gravid females are the most fumigant-tolerant life stage. The lemons showed some rind damage at concentrations of ammonia fumigation of 6000-7500 ppm, suggesting that while higher dosages than those tested might kill scales, they would be detrimental to fruit quality. These results indicate that ammonia fumigation at 22 C is not an effective control method for California red scale with the eggs of the species being the most tolerant life-stage.


Last Modified: 9/22/2014
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