影响柑桔树开花结果性能的生态生理因素

本文报道1988年和1989年春夏之际异常和正常的桔园小气候环境对柑桔树开花结果物候期、抽梢生长、幼果发育、生理落果、当年果实产量和品质等性能的影响。结果表明,柑桔树的座果率受许多生态生理因素制约,但第一次生理落果主要与开花期桔园的小气候环境有关,第二次生理落果则与树体营养生理代谢密切相关。据此提出了预测预报柑桔树第二次生理落果的指标及其防御措施。     

Distribution ofGeotrichum candidum citrus race in citrus groves and non-citrus fields in Japan

The presence ofGeotrichum candidum citrus race, the citrus sour rot pathogen, was examined in soils of citrus groves and non-citrus fields of Japan. Soil samples were collected from 223 sites (118 sites in citrus groves, and 105 sites in fields cultivated with 33 species of non-citrus plants and in evergreen broad-leaved forest) in 11 main citrus-growing prefectures, and Hokkaido, a non-citrus-growing area. Of 236 soil samples from citrus groves, 95.76% containedG. candidum citrus race and 0.42% contained the non-citrus race; while of 210 samples from non-citrus fields, 62.85% and 4.76% contained the citrus race and the non-citrus race respectively. All of the citrus race isolates obtained either from citrus groves or non-citrus fields were pathogenic on lemon (Citrus limon) and satsuma mandarin (Citrus unshiu), but some of these isolates failed to infect orange (Citrus sinensis). The non-citrus races were pathogenic on ripe tomato fruit (Lycopersicon esculentum) and ripe muskmelon fruit (Cucumis melo var.reticulatus). Results indicated that citrus sour rot pathogen is widely distributed in citrus groves and non-citrus fields of diverse plant species in Japan.     

Nontarget impact of spinosad GF-120 bait sprays for control of the Mexican fruit fly (Diptera: Tephritidae) in Texas citrus

Bait sprays containing the toxicant spinosad (GF-120) were applied to citrus groves in the Rio Grande Valley of Texas where Mexican fruit flies were detected in surveillance traps. The sprays were applied as a supplement to a continuous sterile insect release program. Sterile fly captures were 47-63% lower in the treated groves compared with control groves. Eight of 10 secondary pest populations declined in the test groves subsequent to spray applications, but they also declined in the control groves, suggesting that the decline was a seasonal phenomenon rather than a result of the bait sprays. Citrus whitefly, Dialeurodes citri (Ashmead), populations increased modestly and citrus blackfly, Aleurocanthus woglumi (Ashby), populations remained unchanged compared with pretreatment levels. Thus, no outbreaks of secondary pests occurred as a result of the spinosad bait sprays in this instance, as has been reported for malathion bait sprays in citrus. The bait sprays had no detectable effect on populations of specific indicator species of parasitoids (including Aphytis spp. and Comperiella bifasciata Howard), or on numbers of beneficial insects in general, in the treated groves.     

Establishment and yearly/seasonal occurrence of the exotic coccidophagous ladybird <Emphasis Type="Italic">Cryptolaemus montrouzieri</Emphasis> (Coleoptera: Coccinellidae) in citrus groves in Shizuoka City,central Japan: a 5-year survey on adult numbers

Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) is a ladybird native to Australia, preying on mealybugs and soft scales, and has been utilized worldwide as a biological control agent. It has long been recognized that C. montrouzieri that was introduced into the main island of Japan had failed to become established. The present study monitored yearly and seasonal occurrence of C. montrouzieri adults in citrus groves at Shizuoka Prefectural Fruit Tree Research Center in Shizuoka City, central Japan in 2008–2012 by using sticky traps and beating citrus trees. Adults of C. montrouzieri were continuously captured for 5 and 4 years in a pesticide-free citrus grove and a neighboring reduced-pesticide grove, respectively. Larvae of C. montrouzieri were observed consuming a cottony scale, Pulvinaria aurantii Cockerell, on citrus trees. These results provide unequivocal evidence for the ladybird’s establishment in central Japan. The number of trapped ladybird adults exhibited four peaks a year: in mid-April, early to late June, mid-August, and late September to early October. Adult numbers in each grove varied largely across years, showing a great increase followed by a rapid decline during a period of 4 years. Factors affecting the seasonal/yearly occurrence of C. montrouzieri adults in citrus groves are discussed.     

Occurrence of the exotic predatory ladybird Platynaspidius maculosus (Coleoptera: Coccinellidae) in citrus groves in Shizuoka City, Central Japan: seasonal prevalence of adults captured on sticky traps

Platynaspidius maculosus (Weise, 1910) (Coleoptera: Coccinellidae) is a ladybird beetle that preys on aphids and is distributed in China, Taiwan, and Vietnam. Recently, P. maculosus has invaded the southern parts of Japan; it was recorded on Okinawa Island in 1998, in Kagoshima Prefecture in 2006, and in Fukuoka Prefecture in 2010. In citrus groves in Shizuoka City, Central Japan in 2009–2012, the exotic ladybird was monitored by use of yellow sticky traps set inside citrus tree canopies. Adults of P. maculosus were captured in three out of the eight groves in 2010. This capture might be the first record of the ladybird from Honshu Island. Adults were trapped in three consecutive years, 2010–2012, in two groves; this suggests the possibility that the ladybird has become established in Shizuoka City. Adults were almost continuously caught on the traps from late April through October, being more abundant in early autumn (early September to early October), late spring (late April to mid-June), and mid-summer (early July to early August). During these periods, citrus shoots are growing and aphids are abundant. This finding suggests that the exotic ladybird might prey on citrus-infesting aphids, thereby reproducing in citrus groves. Based on the results obtained, potential impacts of the exotic ladybird on native aphidophagous ladybirds are also discussed.     

The influence of host fruit and temperature on the body size of adult Ceratitis capitata (Diptera: Tephritidae) under laboratory and field conditions

The adult body size of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), varies in natural conditions. Body size is an important fitness indicator in the Mediterranean fruit fly; larger individuals are more competitive at mating and have a greater dispersion capacity and fertility. Both temperature during larval development and host fruit quality have been cited as possible causes for this variation. We studied the influence of host fruit and temperature during larval development on adult body size (wing area) in the laboratory, and determined body size variation in field populations of the Mediterannean fruit fly in eastern Spain. Field flies measured had two origins: 1) flies periodically collected throughout the year in field traps from 32 citrus groves, during the period 2003-2007; and 2) flies evolved from different fruit species collected between June and December in 2003 and 2004. In the lab, wing area of male and female adults varied significantly with temperature during larval development, being larger at the lowest temperature. Adult size also was significantly different depending on the host fruit in which larvae developed. The size of the flies captured at the field, either from traps or from fruits, varied seasonally showing a gradual pattern of change along the year. The largest individuals were obtained during winter and early spring and the smallest during late summer. In field conditions, the size of the adult Mediterannean fruit fly seems apparently more related with air temperature than with host fruit. The implications of this adult size pattern on the biology of C. capitata and on the application of the sterile insect technique are discussed.     

Enumerative and binomial sampling plans for citrus mealybug (Homoptera: pseudococcidae) in citrus groves

The spatial distribution of the citrus mealybug, Planococcus citri (Risso) (Homoptera: Pseudococcidae), was studied in citrus groves in northeastern Spain. Constant precision sampling plans were designed for all developmental stages of citrus mealybug under the fruit calyx, for late stages on fruit, and for females on trunks and main branches; more than 66, 286, and 101 data sets, respectively, were collected from nine commercial fields during 1992-1998. Dispersion parameters were determined using Taylor's power law, giving aggregated spatial patterns for citrus mealybug populations in three locations of the tree sampled. A significant relationship between the number of insects per organ and the percentage of occupied organs was established using either Wilson and Room's binomial model or Kono and Sugino's empirical formula. Constant precision (E = 0.25) sampling plans (i.e., enumerative plans) for estimating mean densities were developed using Green's equation and the two binomial models. For making management decisions, enumerative counts may be less labor-intensive than binomial sampling. Therefore, we recommend enumerative sampling plans for the use in an integrated pest management program in citrus. Required sample sizes for the range of population densities near current management thresholds, in the three plant locations calyx, fruit, and trunk were 50, 110-330, and 30, respectively. Binomial sampling, especially the empirical model, required a higher sample size to achieve equivalent levels of precision.     

Incidence of Candidatus Liberibacter asiaticus infection in abandoned citrus occurring in proximity to commercially managed groves

Huanglongbing is one of the most devastating diseases of citrus (Citrus spp.). One management tactic against huanglongbing is aggressive management of the vector, the Asian citrus psyllid (Diaphorina citri Kuwayama), with insecticide applications. However, D. citri in abandoned groves are not controlled and therefore pose a risk of reinfestation for nearby commercial citrus. These abandoned groves could serve as a reservoir for the vector, as well as a source of the presumed causal agent for huanglongbing in Florida, Candidatus Liberibacter asiaticus (Las). The current study was conducted to determine the degree to which Las is present in abandoned Florida citrus groves and to compare relative inoculum levels in nearby managed and abandoned groves during times of the year when D. citri are abundant (June, July, and August). In addition, the movement of Las by dispersing D. citri adults from inner and edge rows of abandoned grove plots to the corresponding rows of managed plots was quantified during the same 3 mo. The results of the current study confirmed the presence of Las in both D. citri and plant tissue in abandoned groves at statistically equivalent levels to those in nearby managed groves. The mean number of D. citri adults dispersing from abandoned to managed grove plots ranged from 7.25 +/- 1.70 to 70.25 +/- 21.25 per 4-d intervals. Of those, the mean number of dispersing D. citri adults that were carrying the Las pathogen ranged from 1.00 +/- 0.58 to 1.50 +/- 0.50. Our results indicate that abandoned citrus groves are a significant source of Ca. Las and that dispersing D. citri move this pathogen into nearby managed groves.     

Effect of wind-borne pollens on the population dynamics ofAmblyseius hibisci [Acarina: Phytoseiidae]

Populations ofAmblyseius hibisci (Chant), an important predator of citrus red mite,Panonychus citri (McGregor) exhibited varying responses to field applications of cat-tail,Typha latifolia L., pollen in San Joaquin Valley citrus groves. Predator densities increased to significantly higher levels after pollen treatments during the fall months, and to a limited extent after late winter treatments, but not after early spring treatments. The amount of response appeared to be inversely related to the levels of natural foods present during the various seasons. Results of the wind-borne pollen monitoring studies indicated that population growth inA. hibisci was correlated with the seasonal pattern of pollen fallout. Population growth was slowest in years when pollen catches were low during the late winter and early spring, and fastest in years when peak pollen catches occurred in late winter or early spring. Population growth inA. hibisci did not appear to be markedly responsive toP. citri populations although suppression of prey densities was indicated in ca. 50% of the cases. In laboratory tests,A. hibisci reproduced through 3 generations on 11 of 23 pollens tested.     

Seasonality in the occurrence of two lepidopterous olive pests in Egypt

Abstract Prays oleae Bern, (OM) and Palpita unionalis Hüb., (JM) are two of the most important pests in olive groves in Egypt. A 3‐year monitoring study using sex pheromone traps in semi‐arid and arid olive groves was performed. In the semi‐arid grove, flight pattern of the OM was the same as in other Mediterranean countries, but in dates concordating plant phenology. The moth completes three generations annually: the first flight is in March to April, the second is in May to June and the third occurs in August to October. In the arid olive grove, an interesting flight pattern was observed. First flight was always very close or overlapped with the second one with no male catches during August to October. However, eggs were present most of the season, indicating unusually high female presence and oviposition activity of the OM during the absence of males in the traps. Generally, moth densities were significantly lower in low fruiting years than in higher ones and were also lower in the arid olive grove than in the semi‐arid one. In contrast, JM males were present all season, exhibiting six to seven and three to four overlapping flight peaks in arid and semi‐arid olive groves, respectively. Moth densities were significantly higher in the arid olive grove than those in the semi‐arid one. This study shows that trapping location and fruit bearing year are characteristics that strongly affect the grove‐specific information needed to estimate correctly adult emergence and thus the timing of control measures.     

Monitoring the susceptibility of citrus rust mite (Acari: Eriophyidae) populations to abamectin.

A citrus leaf disk bioassay was developed to monitor the susceptibility of citrus rust mite, Phyllocoptruta oleivora (Ashmead), populations to abamectin. Disks from leaves of several citrus cultivars were equally suitable bioassay substrates, and there was no difference in mortality when mites were sprayed directly or exposed to dry abamectin residue. The concentration-response relationship was determined at intervals over 2 yr for a reference population of citrus rust mites that had been maintained in culture and never exposed to acaricides. Three diagnostic concentrations of abamectin were selected based on the response of the reference population and were used to test the susceptibility of 15 populations of mites from commercial citrus groves. Comparisons with the reference population showed reduced levels of susceptibility in some populations. Populations of citrus rust mites from 6 commercial groves were sprayed twice in 1997 with combinations of acaricides designed to exert different intensities of selection pressure from abamectin. None of these populations showed a change in their response to abamectin in pre- and postspray bioassays, although their susceptibility was usually less than that of mites from the susceptible reference population. Biweekly counts of rust mites on fruit in these 6 groves suggested that, relative to groves which received no abamectin or 1 abamectin spray, mite control was not adversely affected in the groves sprayed twice with abamectin. The bioassay method is discussed in relation to factors that affect the interpretation of results from its use, and factors that may affect the development of resistance to abamectin in citrus rust mite populations are presented. This study has provided baseline data with which the results of ongoing tests of the response of citrus rust mite populations to abamectin can be compared.     

Stability of Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) resistance to hexythiazox in citrus groves

The false spider mite, Brevipalpus phoenicis (Geijskes), is one the most important pests of the citrus groves and transmits the citrus leprosis virus. The acaricide hexythiazox has been widely used for controlling B. phoenicis in citrus groves. The resistance of this species to hexythiazox has already been detected at high frequencies at some locations. In order to implement a resistance management program, studies were undertaken to understand the stability of the resistance of B. phoenicis to hexythiazox by 1) comparing the life-history of susceptible (S) and resistant (R) strains under laboratory conditions, and 2) evaluating the dynamics of hexythiazox resistance in citrus field plots with low (< 20%) and high (> 60%) frequency of resistance, during two years. The frequencies of resistance were estimated with direct contact bioassays on eggs with discriminating concentration of 18 mg of hexythiazox/L of water. There were no significant differences between S and R strains, based on biological parameters evaluated to build fertility life tables. However, the resistance of B. phoenicis to hexythiazox was unstable under field conditions; that is, significant reductions in the frequency of resistance were observed in the absence of selection pressure, either in citrus field plots with low or high frequency of resistance. Therefore, the instability of B. phoenicis resistance to hexythiazox can be exploited in resistance management programs.     

Seasonal occurrence of key arthropod pests and associated natural enemies in Alabama Satsuma citrus

Six Alabama Satsuma mandarin orchards (four conventionally sprayed and two unsprayed) were surveyed during 2005 and 2006 to determine the population dynamics of arthropod pests and their natural enemies. Twenty-eight arthropod pest species were encountered; the major foliage pests were citrus whitefly, Dialeurodes citri (Ashmead); purple scale, Lepidosaphes beckii (Newman); Glover scale, L. gloveri (Packard); and citrus red mite, Panonychus citri (McGregor). Two distinct population peaks were recorded for citrus whitefly at most locations. The most important direct sources of citrus whitefly mortality were parasitism by Encarsia lahorensis (Howard) and infection by the pathogenic fungus, Aschersonia aleyrodis Webber. In general, all stages of both scale insects (purple scale and Glover scale) were present in the orchards year-round, indicative of overlapping generations; however, the highest densities were recorded during the early season. Citrus whitefly, purple scale, and Glover scale were more abundant on leaves collected from the interior of the tree canopy than in the exterior canopy. Citrus red mite densities were highest in the spring, with populations declining at the start of the summer, and were more abundant in the exterior canopy than in the interior canopy. The most important natural enemies of citrus red mite were predatory mites belonging to several families, of which Typhlodromalus peregrinus Muma (Phytoseiidae) was the predominant species. Major differences were recorded in the relative abundance of different arthropod pest species in the orchards: citrus whitefly, purple scale, and Glover scale predominated in the unsprayed orchards, whereas citrus red mite infestations were more severe in the sprayed orchards. The results are discussed in relation to the possible effect of orchard management practices on abundance of the major pests.     

From Augmentation to Conservation of Entomopathogenic Nematodes: Trophic Cascades, Habitat Manipulation and Enhanced Biological Control of Diaprepes abbreviatus Root Weevils in Florida Citrus Groves

The use of entomopathogenic nematodes (EPN) for management of the root weevil, Diaprepes abbreviatus, in Florida citrus groves is considered a biological control success story and typically involves augmentation in which EPN are applied inundatively as biopesticides to quickly kill the pest. However, recent evidence indicates that efficacy of EPN applications in Florida citrus depends on soil type. They are very effective in the well drained coarse sands of the Central Ridge but often less so in poorly drained fine-textured soils of the Flatwoods. Moreover, groves on the Central Ridge can harbor rich communities of endemic EPN that might often suppress weevil populations below economic thresholds, whereas Flatwoods groves tend to have few endemic EPN and frequent weevil problems. Current research is examining the ecological dynamics of EPN in Florida citrus groves, the potential impact of EPN augmentation on soil food webs, especially endemic EPN, and whether habitat manipulation and inoculation strategies might be effective for conserving and enhancing EPN communities to achieve long-term control in problem areas. Conservation biological control could extend the usefulness of EPN in Florida citrus and be especially appropriate for groves with persistent weevil problems.     

Seasonal and yearly change in adult abundance of a predacious ladybird <Emphasis Type="Italic">Serangium japonicum</Emphasis> (Coleoptera: Coccinellidae) and the citrus whitefly <Emphasis Type="Italic">Dialeurodes citri</Emphasis> (Hemiptera: Aleyrodidae) in citrus groves

Serangium japonicum Chapin (Coleoptera: Coccinellidae) chiefly attacks whiteflies. This study monitored the adult occurrence of the ladybird and the citrus whitefly Dialeurodes citri (Ashmead) (Hemiptera: Aleyrodidae) in citrus groves in central Japan using sticky traps, thereby examining temporal relationships in their abundance. Many S. japonicum adults were captured in a pesticide-free grove where D. citri adults were very abundant, with few adults in neighboring (organic, reduced pesticide, and conventional) groves harboring small numbers of D. citri. The whitefly adults exhibited a large peak in numbers in late May to early June. Two peaks of the ladybird adult numbers were detected in late May to early June and late June to mid-July, ?6 to 7 days, and nearly 1 month after the peak in whitefly adult numbers, respectively. The ladybird adults found during the first peak period would be those that visited citrus trees mainly for oviposition, and the adults caught during the second peak period would be those that newly emerged after consuming immature whiteflies at the larval stage. Based on a yearly change in adult numbers in the pesticide-free grove, i.e., a large increase in S. japonicum numbers followed by a rapid decline in D. citri numbers, the ladybird’s role in controlling the whitefly is discussed.     

临海柑橘园橘小实蝇种群数量消长规律

【背景】近年来,随着种植结构的改变以及南方携虫水果的频繁调运,橘小实蝇逐渐向北扩散危害,对水果生产造成严重威胁。【方法】2008～2010年应用性诱剂的监测方法对柑橘园橘小实蝇种群数量进行了定点、系统的跟踪监测;并结合气象资料和田间调查情况,通过对当旬成虫数量与当旬及其前延逐句气象要素的筛选来建模,进而确定影响橘小实蝇种群数量的主要气象因子。【结果】临海柑橘园橘小实蝇种群数量时序变化呈单峰型曲线,其性诱成虫初见期在6月下旬至8月初,高峰期在9月上旬至11月上旬,11月中旬后成虫数量逐渐下降,到12月下旬未诱集到成虫。气象因子筛选和建模结果表明,柑橘园橘小实蝇成虫种群数量年度变动以旬平均温度为决定要素,季节性变化以旬降雨量为决定要素。【结论与意义】临海柑橘园橘小实蝇种群数量随温度和土壤湿度的增大而增长。本研究对提高橘小实蝇监测预警水平、有效控制橘小实蝇危害具有重要意义。     

Population dynamics and functional response of Citrostichus phyllocnistoides (Narayanan) (Hym., Eulophidae) on citrus leaf-miner, Phyllocnistis citrella Stainton (Lep., Phyllocnistidae) in Fuzhou region of south-east China

Abstract:  Population dynamics of the citrus leaf-miner (CLM) Phyllocnistis citrella Stainton, and its major parasitoid Citrostichus phyllocnistoides (Narayanan) were investigated from June to September 1994 at the teaching and research farm of the Fujian Agricultural and Forestry University (FAFU), south-east China. Based on the field investigation, the functional and numerical responses of C. phyllocnistoides were studied in laboratory experiments. During the survey period, four peaks of CLM and C. phyllocnistoides populations were observed in the growing stage of summer shoots and two peaks of CLM and C. phyllocnistoides populations, respectively, in the growing stage of fall shoots. C. phyllocnistoides is the most abundant parasitoid both in seasonal and spatial dynamics, and demonstrates a Holling type III functional response to CLM. Parasitism varied with the densities of both parasitoid and host. A 1 : 10 ratio was recorded to be an optimal proportion of C. phyllocnistoides to CLM.     

Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves

Studies were conducted to assess population densities and phenology of the psyllid Diaphorina citri Kuwayama at two citrus groves in east-central Florida. One grove contained young, irrigated grapefruit trees and the other contained mature, nonirrigated orange trees. The two groves were sampled weekly for eggs, nymphs, and adults on flush shoots; for adults on mature leaves; and for adults captured on yellow sticky card traps. Because infestations of immature D. citri develop strictly on young flush, the abundance of flush was assessed weekly. Overall means of 26.5, 16.8, and 0.27 eggs, nymphs, and adults per flush shoot, respectively, were observed in the young grapefruit trees. In the grove of mature orange trees, overall means of 16.0, 12.7, and 0.31 eggs, nymphs, and adults per flush shoot were observed, respectively. Flush abundance was an inconsistent indicator of the mean density of D. citri per flush shoot. Mean density per shoot by itself was an inconsistent indicator of overall population levels of D. citri at each study site because few shoots were sometimes present when mean densities per shoot were high. May, June, and July were periods of time when immature D. citri were consistently present and most abundant at each study site, but the study indicated large infestations could occur at any time of the year depending on environmental factors and flush availability. Yellow sticky traps were effective for both male and female D. citri and useful for gauging adult population trends.