귤애가루깍지벌레는 감귤의 주요 깍지벌레 중 하나로 시설재배에서 피해가 심하다. 귤애가루깍지벌레는 밀집하여 발생하는 특성을 갖고 있으며, 귤굴나방이나 잎말이나방류 피해 잎에 기생하고 있어 약제 방제가 어려운 원인이 되기도 한다. 제주지역의 친환경 감귤원을 대상으로 천적곤충과 병원성 미생물을 조사하였다. 천적곤충은 기생성 천척은 Anagyrus sp. 1종과 포식성 천적은 혹파리 일종인 Golanudiplosis japonicus와 꼬마남생이무당벌레 Propylea japonica, 무당벌레 Harmonia axyridis, 풀잠자리 Chrysoperla carnea, 호랑풀잠자리 Micromus sp. 5종이었다. Anagyrus sp. 성충을 황색끈끈이트랩으로 연중 시기별 발생양상을 조사한 결과 5월 하순~11월 상순까지 발생하였으며, 귤애가루 깍지벌레 1세대 기간 동안 2회의 발생성기가 나타났다. 그 외에 곤충병원성 곰팡이 일종인 Paecilomyces sp.가 확인되었 는데, 주로 장마철에 자연발생되고 있었다. 귤애가루깍지벌레 생물적 방제를 위해 수입 천적인 Cryptolaemus montrouzieri (상품명: 깍지무당벌레)를 농가에서 구입하여 활용하고 있다.

최근 들어 하우스재배 감귤을 중심으로 발생이 증가하고 있는 귤애가루깍지벌레에 대해 효율적인 발생예찰과 함께 방제시기를 결정하기 위하여 합성 성페로몬을 이용하여 시기별 발생특성을 조사하였다. 귤애가루깍지벌레의 수컷 성충은 합성 성페로몬뿐만 아니라 색에도 반응하였다. 성페로몬의 농도는 5.0 mg까지 농도가 증가할수록 유인력이 높았다. 귤애가루깍지벌레 수컷 성충은 연 4회 발생되고 있었으며, 월동 후 수컷 성충이 처음 발생되기 시작하는 시기는 4월 중하순이었다. 수컷 성충발생이 가장 많은 시기는 제 1세대 발생기인 7월 상중순이었다. 성페로몬트 랩에 유인된 귤애가루깍지벌레 수컷 성충은 한 세대 내에서 3회의 발생성기가 나타났으며, 이는 귤애가루깍지벌레가 1~3령 약충으로 월동하기 때문인 것으로 추정되었다. 트랩에 유인된 수컷 성충의 밀도와 나무의 가지당 평균밀도와는 높은 정(+)의 상관을 갖고 있었다. 수컷 성충의 최대 유인시기를 이용하여 1령 약충 발생 시기를 추정할 수 있었으며, 그 적산온도는 산란전 기간과 비슷한 350DD이었다.

Arrowhead scale, Unaspis yanonensis, is a serious scale insect pest of citrus in Jeju. The sticky taping of 1.0 cm diameter twig was a good survey method for arrowhead scale crawler. There are three times crawler occurrence season - late May to early July, late July to middle September and late September to late October. But the third occurred crawlers are all died during overwintering in open-field groves. This study was conducted to provide information on efficient sampling plan for arrowhead scale within the tree. Twig and fruit was fit for secondary sample unit by two-stage variance analysis. Both sample number per tree (primary sample unit) was eight twigs or fruits. Taylor’s power law was better described the distribution characteristic of arrowhead scale than Iwao’s patchiness regression. The slope of both linear regressions was greater than “1” which means aggregative distribution pattern. Minimum sample size to estimate the density was calculated using by two parameters of Taylor’s power law. To estimate the mean density on twig and fruit by binomial sampling plan, the optimum tally threshold was 5 and 7, respectively.

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.

Temperature-dependent development and oviposition component models were developed for Pseudococcus cryptus Hempel (Homoptera: Pseudococcidae). Egg development times decreased with increasing temperature and ranged from 2.4d at 16℃ to 1.0d at 28℃. Total development times of nymphs reared on citrus leaves decreased from 54.9d at 16℃ to 17.4d at 28℃ and 19.3d at 32℃. As P. cryptus showed an ovoviviparous reproductive behavior, the periods of egg and the 1st nymph were combined. By fitting linear models to the data the lower developmental threshold temperatures for egg-1st nymphs, the 2nd nymphs, the 3rd nymphs, and all nymphs combined were calculated as 8.7, 12.8, 13.1, and 12.1℃, respectively. The thermal constants were 198.6, 84.7, 69.8, and 296.3 degree-days for each of the above stages. The non-linear model based on a Gaussian equation, which fits the relationship between development rate and temperature was well for all stages. Adult longevity decreased with increasing temperature and ranged from 80.4d at 16 to 31.3d at 32.0℃. Also, preoviposition and oviposition periods showed a similar pattern with the longevity. P. cryptus had a maximum fecundity of 111 eggs per female at 28℃, which declined to 102.7 eggs per female at 32℃.