Spatial dispersion and sampling of citrus whitefly,Dialeurodes citri,for control decisions in a citrus orchard

1 Monitoring the citrus whitefly Dialeurodes citri (Ashmead) in citrus orchards in Israel is necessary for control decisions in IPM in the period before the establishment of natural enemies. The main damage caused by D. citri is due to sooty mould, which colonizes the sweet secretions of this pest. 2 Using Taylor’s Power Law to describe the variance–mean relationship, the dispersion of the citrus whitefly was found to be aggregated at all developmental stages. The action threshold was estimated using regression of sooty mould level on egg or larval counts. 3 Two-stage sampling plans were constructed in different pest generations, for eggs and larval stages, on the basis of the variance between leaves on a tree and the variance between trees in a plot. 4 Fixed sample size plans were prepared, with possible numbers of trees and the numbers of leaves per tree to be sampled, in order to attain a given precision level. 5 Sequential sampling plans were also drawn up, on the basis of four leaves per tree, where trees are sampled until a decision can be reached. The maximum number of trees to be sampled was set according to the corresponding fixed sample size plan. 6 Simulation of the sequential sampling plans showed them to be highly reliable in terms of the decision reached with economy in sample size for high and low infestation levels.     

Reproduction of three eulophid wasps that parasitise larvae of the citrus leafminer

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) (CLM), is a citrus pest indigenous to Southeast Asia. It was discovered in Israel in 1994. The pest attacks the young foliage of citrus, and damage is caused by the larvae tunnelling under the epidermis of young leaves, leading to foliage destruction. The present study documents basic biological parameters of three exotic eulophid wasps in the laboratory: Semielacher petiolatus, Quadrastichus citrella and Teleopterus sp. S. petiolatus females preferred to lay eggs in the 3rd larval instar of CLM, but did not lay eggs in the 1st instar. Its development ranged from 9 to 14 days. Female longevity was 30.2±5.9 days, its daily oviposition was 12.16±0.68 eggs/day, the total number of eggs oviposited per female was 278.9±74.1, and the number of CLM larvae parasitised was 260.0±68.3. Q. citrella preferred to lay in the 3rd and 4th instar larvae, but not in the 1st instar, its development ranged from 9 to 14 days, female longevity was 40.6±1.9 days, oviposition came to 8.3±0.6 eggs/day, the total number of eggs oviposited was 281.3±64.9/female and the number of parasitised CLM larvae was 276.5±63.7. Teleopterus sp. preferred to lay eggs in the 3rd larval instar, its development required 11–17 days, female longevity was 28.7±3.8 days, its daily number of offspring was 5.2±0.38 offspring/day and with emergence of 138.9±27.7 offspring/female. This knowledge enabled us to maintain high quality cultures for their releases in Israel.     

Mortality factors affecting the leaf-mining stages of Phyllonorycter (Lepidoptera: Gracillariidae) on oak and birch 1. Analysis of the mortality factors

Mortality of life stages of Phyllonoycter species in mined leaves of oak and birch was investigated in a Cheshire locality during 1974. Phyllonotycter species are mostly bivoltine, but P. cavella is univoltine. Parasitism and host-feeding (predation) by Hymenoptera caused most mortality. Parasitism was heaviest in the first generations, with ectoparasitism predominating, although endoparasitism caused inore mortality in the second generations. The incidence of host-feeding increased to leaf-fall when more mines contained host-fed remains than either parasites or healthy Phyllonoycter . Host-feeding occurred particularly in the first three (sap-feeding) larval instars; ectoparasitism affected mainly the two subsequent (tissue-feeding) larval stages and pupae; and endoparasitism occurred in all stages although affected hosts are killed only from the fourth larval instar onwards. Highest mortality was suffered by tissue feeders in the first generation but by sap feeders in the second. Total mortality was greatest in second generation mines and, in a given generation, survival curves for Phyllonotycter were similar on both tree species. The observed density of second generation mines relative to first in the sample was higher than predicted from first generation mortality levels, and this is discussed.     

Natural and manipulated populations of the treehole mosquito, Ochlerotatus triseriatus, at its northernmost range limit in southern Ontario, Canada.

Ochlerotatus triseriatus, the eastern treehole mosquito, reaches its northernmost range limit in the extreme southeast of Canada. As a known vector of West Nile and La Crosse encephalitis viruses and a potential vector of eastern equine encephalitis, its population biology is of interest. In southern Ontario, high larval densities occur in urban woodlots within sugar maple and American beech treehole communities comprising rotifers, nematode worms, mites, other dipterans, and scirtid beetles. Treehole water was characterized by low dissolved oxygen levels and seasonally variable pH and temperature, with the latter being most influential on local populations. Densities were significantly higher (up to 503 larvae 100 ml(-1)) in tree holes close to the forest floor (<1 m) and in experimental tree holes seeded with autumn-shed maple leaves as opposed to leaves of black oak and beech. In this locality, weekly sampling showed Oc. triseriatus to be multivoltine, with mass egg hatching beginning under coldwater (<10 degrees C) conditions in March/April, and thereafter producing three successful generations with a possible, less successful fourth in late summer. Some 1st instar larvae were present in water as cold as 0.7 degree C. Compared with larval psychodids living in the same tree hole, population losses of Oc. triseriatus due to washout during major rainfall events were negligible despite high flowthrough of water derived from stemflow.     

Oviposition behaviour and distribution of egg masses of the European leaf roller,Archips rosanus (L.), on citrus trees

The citrus leaf roller (CLR), Archips rosanus, a threatening pest of leaves and fruitlets on fruit trees, which in recent years has led to considerable damage to different citrus trees in some parts of the Mazandaran province of Iran. Insect activity on citrus trees causes the growth of buds and leaves to stop and foliage to dry. Pest oviposition as egg masses occurs on the host tree’s trunk. Eggs spent a year in the hibernation stage and, in the following spring, hatched the first instar larvae that fed on the opened buds. The distributions of CLR egg masses, deposited in 2015–2016, were evaluated on the Thomson novel cultivar (Citrus sinensis L.) in the northern region of Iran. The results showed that the numbers of egg masses laid on the trees at different height ranges of 0–50, 50–100, 100–150 and 150–200 cm were, respectively, 38.65, 33.78, 18.54 and 9.03%. The mean number of A. rosanus eggs per mass, however, was not significant at different heights of the tree. Also, most of the egg masses were laid in the north and south directions in comparison with the west and east directions, with no significant difference in mean number in different geographical directions.     

樟个木虱形态特征及生物学特性

樟个木虱Triozacamphorae是近年来上海地区香樟上发生的一种新害虫。作者对其形态和生物学特性进行了研究。樟个木虱在上海以 1年发生 2代为主 ,偶发 3代。樟个木虱以低龄若虫在叶片上越冬 ,3月下旬至 4月上旬越冬代羽化 ;第 1代开始于 3月下旬 ,羽化高峰在 6月份 ;第 2代开始于 5月下旬 ,并主要以该代若虫越冬 ;第 3代若虫偶发 ,开始于 7月上旬 ,以若虫越冬。樟个木虱第 1代若虫的平均发育历期为 5 0 72d,1～ 5龄若虫的历期分别为 :1 8 .3 1± 2 .2 1d ,1 4. 90± 9. 92d,6 .1 1± 2 . 2 0d,5 .80±3 . 61d ,5 60± 1 5 1d。成虫的寿命为 3～ 1 1d ,平均寿命为 6 41d。樟个木虱的产卵量为 3 9. 1粒 雌虫。2 4℃下 ,卵历期 5～ 7d不等 ,平均为 5. 3 4± 0 . 5 7d ,卵平均孵化率为 83 . 7%。樟个木虱低龄若虫中 3龄若虫最耐高温 ,其次为 2龄若虫 ,1龄若虫最不耐高温。     

苍耳杆野螟生物学特性的研究

苍耳杆野螟是寄生在苍耳上的1种重要药用昆虫。在湖南（常德）每年发生4代,以老熟幼虫（五龄）在苍耳茎杆蛀道内越冬。室内自然变温下（22．2～25．0℃）饲养,卵期为4．8天,幼虫期为23．6天,蛹期为见11．8天,成虫期为6．1天。每雌可产卵124～585粒,块产。一、二龄幼虫食叶,三龄后蛀茎。     

绿步甲的形态特征及其生物学特性

记述绿步甲Carabus(Coptolabrus)smaragdinus Fischervon Waldheim各虫态的形态特征及其生物学特性。在山东嘉祥,该虫1年发生2代,以成虫在土壤中越冬。成虫在4月至10月活动,分别与7月上旬、9月中旬产卵。卵期平均为8d;幼虫共2龄,历期分别为4d,13～15d;预蛹期约为15d;蛹期为7～8d。成、幼虫以蜗牛和多种鳞翅目昆虫为食。     

Fecundity,autogeny, and the larval environment of the pitcher-plant mosquito,Wyeomyia smithii

Summary Pupae and fourth instar larvae of a southern (30°N, Alabama, USA) population of Wyeomyia smithii Coq. (Diptera: Culicidae) were collected from pitcher plants. Adults which emerged were maintained without food then dissected to determine their egg clutch size. Among females which matured eggs, fecundities were negatively correlated with larval densities in individual pitchers. The mean autogenous fecundity of the overwintering generation did not differ from a summer sample. Adults unable to mature eggs comprised 6–39% of samples, depending on whether collected as pupae or fourth instar larvae. Fecundity was negatively correlated with time to adult eclosion among larvae maintained on unrenewed pitcher contents in the laboratory.Cohorts from this population were reared in artificial containers from egg hatch to adulthood at a single density and a superior or inferior diet. On the superior larval diet, all females survived to reproductive age, and all but one (>99%) produced eggs autogenously. On the inferior diet, survivorship to adult eclosion was significantly less, a high proportion of females died before reaching reproductive age, and only 19% of survivors matured eggs without blood. Protracted larval development induced by the inferior diet did not influence the probability of autogeny among females that survived to reproductive maturity.The relationship between larval environment and reproductive strategies is contrasted across the geographic range of W. smithii. Bloodfeeding occurs among southern populations where density dependent constraints on preimaginal growth are constantly severe. The loss of hematophagy among northern populations may have been facilitated by periods of density independent larval growth.Institute of Food and Agricultural Sciences, University of Florida, Experimental Station Journal Series No. 3645     

柑桔木虱及其防治

柑砧术虱是柑桔新梢期重要害虫,刺吸为害。福建福州在柑桔上一年发生8代,在月桔、九里香上一年约发生10代左右,世代重叠,以成虫在柑桔叶背群集越冬,无完全滞育。4—5月气温22．3℃世代历期42．5天．6-7月27．2℃为24．4天．8月28．1℃为23．2天。10-12月19.6℃为52．9天。成虫寿命长,约历1个月半,越冬代长达半年。田间种群消长与柑桔芽梢抽发期相对应．一年中虫口数量出现3个高峰期,第一峰期3-4月为柑桔春梢主要抽发期,第二峰期5-6月为夏梢主要抽发期,第三峰期8～9月为秋梢主要抽发期,其中以秋梢期虫口数量最大．秋芽受害最重,次为春梢期。本还对柑桔术虱天敌进行调查,并对柑桔术虱卵、若虫和成虫进行药剂防治试验。     

Nitrogen fertilization in citrus orchards

Summary The purpose of this review was to evaluate critically the results obtained in citrus nitrogen fertilization experiments in Israel and in other parts of the world, in order to increase our understanding of the processes involved and to improve the recommendations to growers. Mature citrus trees contain 1–2 kg N/tree, 30–60% of which is in the annual parts (leaves and fruits). 30g N is deposited annually in the tree skeleton. Based on these results and on a review of long-term fertilization experiments with citrus from various parts of the world, it was concluded that 200 kg N/ha applied annually is sufficient to sustain good citrus yields and tree development, about half of which is incorporated in the fruits and one-tenth deposited in the tree, the balance being made up by leaching and gaseous losses. Experiments with¹⁵N labeled fertilizer applications showed that the highest N-uptake rate occurred during fruit set and that in winter the uptake was very low. N reserves in the older tissues played an important part in the development of new leaves and flowers in the spring, when the uptake from the soil was still low. It was concluded that the nitrogen contained in the soil organic matter (2 Mg/ha) and in the mature trees (1 Mg/ha) plays an important part in the regulation of N supply to the growing parts of the tree. More N is derived from these parts with low N fertilization than with an abundant supply. The purpose of fertilization is to ensure proper development of the tree, not the current fruit yield. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1770-E. 1986 series.     

Life history of the sand fly vector Lutzomyia cruciata in laboratory conditions

Lutzomyia cruciata Coquillet (Diptera: Psychodidae: Phlebotominae) is a potential vector of Leishmania sp.; its geographical distribution in Mexico is widespread, but its life history is unknown. The present study gives relevant information on the life cycle, morphology, survival and reproduction of Lu. cruciata observed over successive generations under laboratory conditions. Seven successive generations were produced. A total of 975 adults were obtained in a sexual proportion of 1.1 : 1 (female : male). Each Lu. cruciata female produced 20.7 eggs and 1.9 adults, approximately, with a proportion of eggs per female of 2.7% (first generation) and 21.3% (second generation). The life cycle of Lu. cruciata, from egg to adult, occurred in 52.7 ± 0.52 days. The largest percentage of mortality occurred during the egg stage (48.5%) and the first larval instar (26.5%), whereas in the pupal stage mortality was the lowest (9.1%). Lutzomyia cruciata exhibits sexual dimorphism based on size, which is exhibited as of the second larval instar, males being smaller than females. The maximum survival of females and males was 10 and 15 days, respectively. An overview of the immature stages of the species made with an electronic scanning microscope is included. This paper contributes basic information on aspects of Lu. cruciata that were previously unknown related to its life history.     

Temperature thresholds and degree-day model for Marmara gulosa (Lepidoptera: Gracillariidae)

The developmental thresholds for Marmara gulosa Guillén & Davis (Lepidoptera: Gracillariidae) were investigated in the laboratory by using 17, 21, 25, 29, and 33 degrees C. The lowest mortality occurred in cohorts exposed to 25 and 29 degrees C. Other temperatures caused >10% mortality primarily in egg and first and second instar sap-feeding larvae. Linear regression analysis approximated the lower developmental threshold at 12.2 degrees C. High mortality and slow developmental rate at 33 degrees C indicate the upper developmental threshold is near this temperature. The degree-day (DD) model indicated that a generation requires an accumulation of 322 DD for development from egg to adult emergence. Average daily temperatures in the San Joaquin Valley could produce up to seven generations of M. gulosa per year. Field studies documented two, five, and three overlapping generations of M. gulosa in walnuts (Juglans regia L.; Juglandaceae), pummelos (Citrus maxima (Burm.) Merr.; Rutaceae), and oranges (Citrus sinensis (L.) Osbeck; Rutaceae), for a total of seven observed peelminer generations. Degree-day units between generations averaged 375 DD for larvae infesting walnut twigs; however, availability of green wood probably affected timing of infestations. Degree-day units between larval generations averaged 322 for pummelos and 309 for oranges, confirming the laboratory estimation. First infestation of citrus occurred in June in pummelo fruit and August in orange fruit when fruit neared 60 mm in diameter. Fruit size and degree-day units could be used as management tools to more precisely time insecticide treatments to target the egg stage and prevent rind damage to citrus. Degree-day units also could be used to more precisely time natural enemy releases to target larval instars that are preferred for oviposition.     

蚕豆象的生物学特性

在武昌,蚕豆象Bruchus rufimanus Boheman每年发生一代,以成虫越冬。成虫必须取食蚕豆花后才能正常交配和产卵。4月为交配盛期。4月中、下旬为产卵盛期,最喜欢把卵产到生长已有1l—20天的嫩蚕豆荚上,但不在豌豆荚上产卵。产卵历期约为9天。4月下旬至5月上旬为孵化盛期。幼虫共四龄,在豆粒内的死亡率随着单个豆粒上侵入孔的增多而增高。8月为化蛹盛期,8月中旬到9月上旬为羽化盛期。羽化出的成虫绝大部分藏在豆粒内越冬。从卵发育到成虫羽化约需120天。成虫寿命一般为212天,最长达295天,但不能度过两个冬季。     

The spiders of a citrus grove in israel and their role as biocontrol agents ofCeroplastes floridensis [Homoptera: Coccidae]

A 12 month survey was carried out of the spider population in a commercial citrus grove at Kibbutz Afeq in Northern Israel. The spiders collected from grapefruit foliage and ground cover were identified; young stages were reared to maturity and then identified.Chiracanthium mildei L. Koch represented 52% of all spiders captured during the year andTheridion sp. accounted for 34%. In the undercover,Gnaphosidae spiders represented 43% of the total spiders captured in pitfall traps andLycosidae 35%. A field experiment was carried out to evaluate the effectivness of spiders in biological control of the scaleCeroplastes floridensis Mask. in the citrus ecosystem. Wherever spiders were undisturbed on tree branches, populations ofC. floridensis were not able to develop to a level sufficient to cause economic damage. The increase in the number of scales was minimal: from 47 initially to 56. There was no damage to leaves nor was honeydew or sooty mold observed. During the same time period, on the 3 branches from which spiders had been eliminated, the number of scales increased seven-fold from 44 to 309. Leaves were heavily infested with sooty mold fungi that developed on the honeydew produced by the scales. Contribution from the Agricultural Research Organization, Neve Ya'ar, Regional Experiment Station. P.O. Haifa 31999, Israel. No. 1314-E 1984, series.     

条纹小斑蛾的生物学特性

条纹小斑蛾Thyrassia penangae(Moor)是乌蔹莓(Japanese cayratia)的重要害虫,在南昌1年发生4～5代,以老熟幼虫结茧越冬。由于该虫各世代总有极少部分个体进入滞育,少数进入越夏的个体1年只发生2代或3代。羽化时间多出现在上午7～10时,羽化后当日或次日下午交配,交配时间集中在下午3～6时,交配一般可持续12个h左右。成虫羽化后需取食花蜜做补充营养才能充分产卵。产配后次日即可产卵。第1代成虫常将卵数十粒聚产于幼嫩叶片的背面,以后各代主要聚产于花蕾上,平均每雌产卵量为43粒。幼虫为4龄。第1代主要取食叶芽、幼枝及嫩叶,以后各代主要取食花蕾。在自然条件下各虫态发育历期:卵为4～7d;幼虫为10～14d;非滞育的茧期(指幼虫结茧后的预蛹至成虫羽化的日期)为8～11d,越夏茧期为32～40d,越冬茧期为205～224d。成虫寿命为3～13d。     

Field evaluation of commercial formulations of the codling moth granulovirus: persistence of activity and success of seasonal applications against natural infestations of codling moth in Pacific Northwest apple orchards

Inundative applications of the codling moth (CM), Cydia pomonella L., granulovirus (CpGV), which target neonate larvae before or during initial entry into fruit, offer potential for selective control of this key pest. In field tests on apple we compared the persistence and efficacy of single applications of three CpGV products approved for organic orchards in North America. In addition, the success of repeated (2–14) applications of one product (Cyd-X) as a principal control measure for CM in apple orchards was monitored following operational use by cooperating growers at four separate locations. In the first study, an early season application of all products at label rates remained highly effective for the first 24 h (averaging 94% larval mortality relative to controls) and moderately effective after 72 h (averaging 71% mortality) during dry sunny conditions. Significant activity remained up to 14 days, suggesting prolonged survival of the virus in UV-protected locations, such as the calyx of fruit. A second application later in the season was slightly less effective. Data obtained from commercial sites provide circumstantial evidence for the effectiveness of well-timed CpGV applications against CM outbreaks. In all cases where first generation larvae were targeted beginning at egg hatch (≈250 degree days) and treated areas monitored (0.3–1.6 ha plots), fruit damage during the second larval generation was reduced or eliminated. Based on the number of live larvae recovered throughout the season, mortality rates remained high (80.3–100% across sites). The cumulative number of moths caught in pheromone-baited traps was reduced (66–94%) in the second flight. Data from tree bands placed to catch diapause-destined larvae indicated overwintering generations remained low in treated sites (0.18 larvae/band).     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Susceptibility of the summer fruit tortrix moth, Adoxophyes orana (Lepidoptera: Tortricidae), to chlorpyrifos and strategies for insecticidal control in orchards

The susceptibility of populations of the summer fruit tortrix moth, Adoxophyes orana, from apple orchards in Kent, England, to chlorpyrifos was determined in 1992, 1994 and 1995, by topically dosing larvae feeding on leaves or adults adhered to pheromone trap sticky bases. LD₅₀ values (range 6.3 to 23.2 ng chlorpyrifos per individual) for first or second generation males, second generation females or for first generation fourth instar larvae collected in the field were significantly greater (2–3 fold) for populations from orchards with a long history of treatment with broad-spectrum organophosphorous and other insecticides than for those from untreated orchards (range 1.6 to 8.1 ng chlorpyrifos per individual), though there was considerable variation between sites and years. Twelve replicated orchard experiments between 1993 and 1995 were used to examine a range of different strategies for insecticidal control. Applications of chlorpyrifos against overwintered larvae feeding in trusses in spring gave, at best, a 75% reduction in larval numbers, insufficient to prevent damage by the subsequent generation in summer. However, two applications of fenoxycarb (one immediately pre-and one immediately post-blossom of apple cv. Cox) completely prevented successful subsequent development of the pest, and a single (post-blossom) spray nearly so. The timing of application of chlorpyrifos against first generation larvae hatching from eggs in June was shown to be critical and currently used methods of spray-timing were unreliable. The effective persistence of chlorpyrifos was short (< 7 days). Though good control could be achieved with a single spray, a better strategy was to apply a series of sprays at 7-day intervals to cover the egg hatch period. Sprays of Bacillus thuringiensis at the same timing intervals gave, maximally, an 80% reduction in larval numbers, but usually less: improved control was not achieved by applying a programme of sprays compared to a single spray, though a novel, more potent, formulation was significantly more active. Triazophos was also effective as an egg hatch spray. Sprays of chlorpyrifos or tebufenozide between late September and mid-October 1995 against second or third instar larvae migrating to overwintering sites before diapause, failed to reduce significantly the numbers of subsequent overwintering larvae or the numbers that emerged to feed on blossom trusses in spring.