To replace hazardous methyl bromide (MB) post-fumigation on imported fruits, due to insufficient ventilation process in industrial practice, alternative fumigation with liquid ethyl formate (EF) with N2 application, which is multi benefits to safe to workplace and environment, has been developed by APQA. Although EF was found to be shown proven efficacy to invasive external feeders such as mealybugs and scales on export and imported fruits and vegetables, there was still some conflicts to accept one of the phytosanitary disinfestation method somewhere because of on reliable and confirmative studies on between MB and EF in terms of efficacy to mealybugs on perishable commodities. In here, we evaluated comparative efficacy of EF and MB to target citrus mealybug, which was seems to be hard control pest, based on the current disinfestation guideline of them in Korea. The potential benefits of using liquid ethyl formate (EF) for future quarantine use could provide for safer workplace involved on and post-fumigation such as cold and packing storages, cost-effectiveness as well as meet the environmental friendly solution.

Methyl bromide(MB) is a fumigant for quarantine and pre-shipment(QPS) that can eradicate target pests within short fumigation periods. However, MB, an ozone-depleting substance, is scheduled to be phased out in the second decade of this century. In contrast to MB alternatives for soil fumigation, there is no ideal alternative fumigant to MB for QPS of perishable commodities. It is important that all target insect pests are killed within a short fumigation time. The citrus mealybug(Planococcuscitri), a problematicquarantine pest from Korea, was exposed to ethyl formate and phosphine for different times and to different concentrations of EF(0.0∼33.4 mg/L) and PH3(0.25∼1.0 mg/L) in small desiccators. The eggs showed more tolerance than the nymphs and adults. To control the eggs, they were treated with a mixture of EF and PH3 for 2 and 4-hr. The egg stage showed 100% mortality with EF:PH3(25.1:0.25, 16.7:0.5, and 16.7:1.0 mg/L) at 4-hr. Treatment with a mixture of EF and PH3 for 4-hr at 8°C can control all stages of the citrus mealybug.

Methyl bromide (MB), as a fumigant for Quarantine and Pre-Shipment(QPS) could offer eradication of target pests within shorter fumigation period and without phytotoxicity. Therefore, unlike MB alternatives for soil fumigation, there is no ideally MB alternative fumigant for QPS purpose, particularly for perishable commodities. It is critically important that within shorter fumigation time requires killing all target insect pests and without effect of quality and deliver treated fruit and vegetables to the final consumer. The citrus mealybug(Planococcuscitri), problem quarantine pest, was tested with different exposure times(2 and 4-hours) and concentrations(EF(0-200 g/m3) and PH3(10-50 g/m3)) in small desiccators for mixture tests. On sensitivity test with small desiccator, the egg stage showed 100% mortality with 200/25(EF/PH3) g/m3 and the nymph and adult stage showed 100% mortality with 10/10(EF/PH3) g/m3 on 2h. Also, the egg stage showed 100% mortality with 150/25(EF/PH3) g/m3on 4h.

Though quarantine use of methyl bromide(MB) is currently permitted in Korea, there has been phasing out and considering ban in many countries due to their ozone depletion properties. VapormateTM, a new gas formulation of ethyl formate(EF) with carbon dioxide, and VivakilTM, a new gas formulation of phosphine(PH3) with carbon dioxide, are MB alternative fumigants to methyl bromide(MB). For applying on import commodities, the efficacy of EF and PH3 was evaluated for 2hr fumigation on egg, nymph and adult stage of citrus mealybug(CMB), Planococcus citri, at two different temperatures(8, 13℃). The CT(Concentration X Time) product of EF to be expect 99% mortality to egg, nymph and adult stage of CMB were 108.3, 22.4 32.4 gh/m3 at 8℃ and 83.2, 25.1, 29.8 gh/m3 at 13℃, respectively. The CT product of PH3 gas to be expect 99% mortality to nymph and adult stage of CMB were 6.50, 2.55 gh/m3 at 8℃ and 3.72, 3.64 gh/m3 at 13℃, respectively. However, PH3 gas applied at high CT(4.2 gh/m3) for 2hr fumigation was not enough to obtain CT to egg stage of CMB at both temperature conditions. These efficacy data based on CT will be useful to predict the CT model in scale-up fumigation at diverse practical conditions.

The males of cryptic mealybug, Pseudococcus cryptus, were attracted on trap baited with or without a synthetic sex pheromone. The attractiveness of sex pheromone trap was higher than yellow-color sticky trap, but both phenologies were similar. There was a positive relationship between mean density of 2nd nymph to adult cryptic mealybug and the density of the male caught on trap. The density of cryptic mealybug per tree was higher correlated with yellow-color sticky trap than sex pheromone trap. The pattern of cryptic mealybug male occurrence had two to three cohorts in a generation resulted from overwintering stage. The maximum occurring time of 1st to 2nd nymph stage could be estimated from the peak time of trap catch by effective temperature accumulation. The higher and lower threshold temperature was estimated as 10.9 and 32.6℃, respectively and its thermal constant was 360 degree-day. The cryptic mealybug parasitoid, Anagyrus sp., which was first recovered in Jeju in 2009, was well attracted on yellow-color sticky trap. There was a high correlation between the density of Anagyrus sp. and of cryptic mealybug males caught on trap.

Some responses of cryptic mealybug, Pseudococcus cryptus, for a sex pheromone, [(1R,3R)-3-isopropenyl-2,2-dimethylcyclobutyl]methyl 3-methyl-3-butenoate, were studied to develop the applying strategy of sex pheromone trap for efficient monitoring and control-time decision in citrus orchards grown in greenhouse for 2 years (2007-2008). The optimal concentration of a sex pheromone was 1.0㎎ per hexane 100㎕ in a using pheromone lure. There was no significant effect of the attraction of male adults among different colours (white, blue and yellow) of plate-type trap baited with sex pheromone. The more male adults were attracted, as the distance of a pheromone trap form a citrus tree infested with cryptic mealybug was closer. The male adults were caught to sex pheromone trap from middle April to late November, and its peak period was the middle of July. The thermal constant for the next attraction was about 640 degree-days (lower threshold temperature=12℃) after confirmed the first attraction of male adults. The optimum control time for cryptic mealybug after the first attraction of male adults were confirmed was estimated as 450 to 500 degree-days.

Cryptic mealybug (CMB), Pseudococcus cryptus, is a serious scale pest on citrus, especially grown in plastic greenhouse on Jeju island, Korea. Binomial sampling plan was developed using the relationship between infested proportion of twig with less than T scales (pT) and mean density per twig (m) according to the empirical model ln(m)=α+βln(-ln(1-pT)). T was defined as tally threshold and set to 1, 2, 3, 4 and 5 scales per twig in this study. T=3 was the best tally threshold for estimating densities of CMB based on the precision of the model. Binomial model with T=3 provided reliable predictions of mean densities of CMB observed on commercial citrus orchards. The obtaining model was evaluated by resampling validation of Wald's sequential binomial plan and by fit at 95% confidence intervals for independent collected data sets. Binomial sampling program for decision-making of CMB population level was obtained at the action threshold 0.10, proportion of twig infested with more than 3 scales.