Indigenous parasitoids (Hym., Chalcidoidea) of Phyllocnistis citrella Stainton (Lep., Gracillariidae) in Jaguariúna, São Paulo State, Brazil: preliminary results

Abstract: The citrus leafminer, Phyllocnistis citrella Stainton, is native to Asia and was detected for the first time in Brazil in 1996. The objectives of this study were to conduct a survey of parasitoids attacking citrus leafminer in Jaguariúna, one of the citrus production regions of São Paulo State, Brazil, and to determine whether indigenous species were providing effective control of this pest species. The collections of new leaves were made weekly at citrus groves in Jaguariúna from October 1996 to October 1997. Of the six indigenous parasitoids which were found, Galeopsomyia fausta LaSalle was the most abundant parasitoid of P. citrella in this region, accounting for more than 90% of the specimens collected. Thus, this species is a serious candidate for biological control of the citrus leafminer in this region of Brazil. Other species collected were Horismenus sp., Cirrospilus 'sp. C', Elasmus sp., Eupelmus sp. and Conura (Ceratosmicra) sp. The mean percentage of parasitism was 39.28% (6.19−86.21%) in unsprayed orchards and 21.38% (1.33−56.63%) in orchards that were occasionally treated with fungicides, acaricides and insecticides Temik and Dipterex.     

Structure and composition of the assemblage of parasitoids associated to Phyllocnistis citrella Pupae Stainton (Lepidoptera: Gracillariidae) in citrus orchards in Southern Brazil

The structure and composition of the assemblage of pupal parasitoids of Phyllocnistis citrella Stainton, the citrus leafminer, were studied in two citrus orchards (Citrus deliciosa Tenore cv. Montenegrina and Citrus sinensis (L.) Osbeck x Citrus reticulata Blanco hybrid Murcott), in Montenegro County (29 degrees 68'S and 51 degrees 46'W), southern Brazil. At fortnightly samplings, from July 2001 to June 2003, all the new shoots from 24 randomly selected trees were inspected. The species richness reached five native species in the Murcott orchard, and six in Montenegrina. In Murcott, the presence of Ageniaspis citricola (Hymenoptera: Encyrtidae), an exotic species, was detected in the first year of sampling, probably migrating from the nearby areas where it had been released for the miner control. In Montenegrina, its presence was only registered in the second year. A. citricola in both areas was dominant and changed the community structure of parasitoid complex of P. citrella in both orchards.     

Premiers résultats sur l'acclimatation d'Ageniaspis citricola Logvinovskaya (Hym., Encyrtidae), parasitoïde spécifique de Phyllocnistis citrella Stainton (Lep., Gracillariidae), en Tunisie

First results on releasing experiments of Ageniaspis citricola Logvinovskaya (Hym., Encyrtidae), a parasitoid of Phyllocnistis citrella Stainton (Lep., Gracillariidae) in Tunisia . Trials were conducted to reduce the population of the citrus leafminer Phyllocnistis citrella in Citrus orchards by releasing the imported specific parasitoid Ageniaspis citricola in Tunisia. Adults of the parasitoid were released in 69 orchards between 1 June and 23 December 1996, corresponding to the two main flushes of Citrus . Results indicate that the parasitoid was established in 27 orchards reaching a maximum percentage of parasitism of 28%. In 1997, A. citricola is established in some Citrus groves proving its real acclimatization in Tunisia, with a maximum percentage of parasitism reaching 45%.     

Impact of Phyllocnistis citrella (Lepidoptera: Gracillariidae) on leaf area development and yield of mature citrus trees in the Mediterranean area

Seasonal population trends and damage to citrus trees by the leafminer Phyllocnistis citrella Stainton were studied in the Valencia area of eastern Spain from 1996 to 1999. The area-wide seasonal flushing pattern of citrus trees and leafminer population trends were determined in 10 mature citrus orchards. In the 10 orchards, the annual percentage of new shoots that developed in the spring ranged from 51 to 96% for individual orchards (mean of 80%). Phyllocnistis citrella populations damaged new leaves from July to November. During this period, approximately 45% of the new leaf area was lost due to leafminer mining. In addition, at three mature citrus orchards, two 'Navelina' sweet oranges from 1996 to 1999 and one 'Clementine' mandarin (variety 'Clemenules') in 1998 and 1999, the leaf area damage, spring flushing pattern, and crop yield were determined in trees sprayed one to three times a year with abamectin (Epimeck, 0.02%) to control P. citrella and compared with nonsprayed control trees. In these three orchards, damaged leaf area in summer-fall flushes was on average 52% in nonsprayed and 8% in sprayed trees. No significant differences were found between sprayed and nonsprayed trees in the spring flushing and flowering pattern, number of fruits or fruit diameter. In Mediterranean areas, P. citrella damaged only 5-15% of the annual new leaf area of mature trees and yield was usually not affected by the pest.     

Biological aspects of Cirrospilus neotropicus Diez & Fidalgo (Hymenoptera: Eulophidae), parasitoid of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae)

The biology of Cirrospilus neotropicus Diez & Fidalgo reared on third instar Phyllocnistis citrella Stainton larvae having Citrus limonia Osbeck as host plant, was evaluated under controlled conditions (25 +/- 1 masculineC; 12h photophase). The survival, immatures development, longevity, sex ratio, host feeding and oviposition ratio of C. neotropicus, were registered. Two groups of parasitoid females were evaluated: one, with parasitoids obtained from P. citrella pupae collected in citrus orchards and the other group came from laboratory rearing. These females, after mating, were maintained individually on gerbox containers with honey and pollen as food source. At each 48h, 12 P. citrella larvae were changed. The average biological cycle of the female progenies from orchard and laboratory generation groups were 11.8 and 11.6 days, respectively. The males progenies had biological cycles of 11.6 and 10.9 days, as well. The shortest immature survival period, for both studied groups was the larval (57.3% - orchard group and 57.4% - lab group). The mated females average longevity (21.8 days) was superior than the non mated ones (9.1 days) for the orchard group. The average daily oviposition rate for this last group was also significantly superior (2.8 eggs /day) than the lab group (1.6 eggs / day). The same trend was observed for the average daily host feeding rate (1.7 larvae /day for the orchard group and 0.9 larvae/ day for the lab group). These data suggest that C. neotropicus have potencial as a biological control agent of P. citrella.     

Seasonal variation of immature stages of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Citrus sinensis orchards under two management systems

Phyllocnistis citrella Stainton is considered an important pest of citrus, causing both direct (reduction on the photosynthetic area) and indirect damage (facilitation of invasion by bacteria that cause citrus canker). The lack of information about the population dynamics of P. citrella, considering the cultivation systems and varieties grown in citrus orchards in Rio Grande do Sul, Brazil, motivated this study. It aimed to evaluate the seasonal variation of immature stages of P. citrella, from June 2002 to July 2003, in two orchards of Citrus sinensis, cv. 'Valencia', one maintained according to organic management principles and the other under conventional ones. Fortnightly samplings were carried out, being one shoot collected from each one of 27 randomly chosen plants. The leaves were analyzed for the presence of eggs, larvae, pupae and mines of P. citrella. Leafminer was recorded from October 2002 to April 2003 in the organic orchard, and from November 2002 to July 2003 in the conventional one. A relationship between population size and resource availability (young leaves) was observed. However, population establishment does not depend exclusively on the existence of resources, but also on suitable climatic conditions. This was evidenced by the absence of attacks on the first shooting, which began in late winter. Meteorological factors and resource availability as a whole explain about 64% and 53% of the observed variation in the population size of P. citrella, respectively in the organic and conventional orchards.     

合成性信息素对柑桔潜叶蛾的田间引诱作用

目前柑桔潜叶蛾的防治主要依赖化学农药, 而且生产中缺少有效测报技术。为此, 我们于2009年6月30日至10月6日在浙江宁波通过有机合成柑桔潜叶蛾Phyllocnistis citrella（鳞翅目, 细蛾科）的3种性信息素化合物顺7, 顺11, 反13-十六碳三烯醛、顺7, 顺11-十六碳二烯醛和顺7-十六碳烯醛, 配制成不同浓度比例的混合物, 进行田间试验比较其引诱活性。结果表明, 单一的顺7, 顺11, 反13-十六碳三烯醛对柑桔潜叶蛾雄蛾就可以显示较强的引诱作用, 而顺7, 顺11-十六碳二烯醛单一成分没有引诱活性, 顺7, 顺11, 反13-十六碳三烯醛与顺7, 顺11-十六碳二烯醛的二元混合物30∶1~3∶1之间活性较强, 而在30∶1的质量比例时诱虫量最高。含顺7-十六碳烯醛的三元混合物, 当顺7, 顺11, 反13-十六碳三烯醛∶顺7, 顺11-十六碳二烯醛∶顺7-十六碳烯醛三者比例为100∶10∶3时有显著增效作用。剂量与诱捕活性试验显示每枚诱芯1 mg顺7, 顺11, 反13-十六碳三烯醛的剂量引诱作用最强, 随浓度降低, 引诱作用下降。诱捕器在0.8~1.5 m之间的不同悬挂高度对诱捕数量无显著影响。结果说明, 顺7, 顺11, 反13-十六碳三烯醛、顺7, 顺11-十六碳二烯醛和顺7-十六碳烯醛组成的三元混合物诱芯可以作为柑桔潜叶蛾的诱杀技术并应用于其生物防治和预测测报。     

Natural enemies of three mealybug species (Hemiptera: Pseudococcidae) found on citrus and effects of some insecticides on the mealybug parasitoid Coccidoxenoides peregrinus (Hymenoptera: Encyrtidae) in South Africa

The population density of mealybug species in some South African citrus orchards has increased to pest status in recent years. The characterization of the natural enemy complex and quantification of their contribution to the control of Planococcus citri (Risso), Pseudococcus longispinus (Targioni-Tozzetti) and Pseudococcus calceolariae (Maskell) on Citrus limon (L.) and Citrus reticulata (Blanco) was investigated through intensive sampling. Eight primary and four secondary parasitoids, and two predator species were identified from P. citri and P. calceolariae. Anagyrus pseudococci (Girault) and Coccidoxenoides peregrinus (Timberlake) were the most common species, accounting for 44% and 21% of the total. Of the five primary parasitoids reared from P. longispinus, A. pseudococci and Anagyrus sp. were predominant, comprising 41% and 30%. Nymphal and adult parasitism (range = 0-26% vs. 0-66%) and predation (range = 0-5.6% vs. 0-4.1%) varied significantly between host trees and mealybug species (P < 0.001). The numbers of nymphal instars and adult stages of P. calceolariae and P. longispinus and the nymphal stage of P. citri that were parasitized and killed by predators correlated significantly with the total number of hosts on which they acted (P < 0.01), suggesting a density-dependent association. Laboratory bioassay of nine contact insecticides (methidathion, methomyl, methyl-parathion, parathion, profenofos and prothiofos) against C. peregrinus indicated that all were highly toxic, causing 98-100% mortality in < 6 h of treatment. The IGRs fenoxycarb and triflumuron did not cause significant parasitoid mortality (P > 0.05). However, a mixture of pyriproxyfen and mineral oil caused a marginally significant mortality (P < 0.05).     

Establishment of Citrostichus phyllocnistoides (Hymenoptera: Eulophidae) as a biological control agent for the citrus leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae) in Spain

A program of introduction of exotic parasitoids for the biological control of the citrus leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) was carried out in València (Spain) between 1996 and 1999. Eleven species of parasitoids were imported through a total of 37 shipments coming from nine countries. Six species were released in the field, the encyrtid Ageniaspis citricola (Logvinosvskaya), and the eulophids Quadrastichus sp., Semielacher petiolatus (Girault), Galeopsomyia fausta LaSalle, Cirrospilus ingenuus (Gahan), and Citrostichus phyllocnistoides (Narayanan). A. citricola was recovered in summer in many release points, reaching nearly 50% of parasitism and dispersing more than 300 m, but it was not able to overwinter. Quadrastichus sp. and S. petiolatus established temporarily in some sites, but produced little differences in parasitism or density of host population. In 1999, a substantial expansion of C. phyllocnistoides of more than 30 km in all directions was observed from one release point. In 2000 and 2001 this parasitoid expanded to all citrus grown in continental Spain and the Balear Islands, becoming the most abundant parasitoid in all the orchards, and displacing native and other introduced parasitoids. As a consequence, parasitism on second instars increased from less than 16% to 65% and on third instars from 35–38% to 59%. Overall, the mean percentage of parasitism increased from 20–25% to near 60%. Apparently, C. phyllocnistoides reduced by 34% the number of eggs and early instars of the host, and by 72% the number of adults. Damage to citrus foliage decreased by 56%.     

Biological Control of Anastrepha spp. (Diptera: Tephritidae) in Mango Orchards through Augmentative Releases of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae)

Diachasmimorpha longicaudata (Ashmead) parasitoids were released by air on a weekly basis over 1600 ha of commercial mango orchards, backyard orchards, and patches of native vegetation, at a density of ca. 940 parasitoids/ha. Releases were made during 2 consecutive years, beginning at flower onset and lasting until the end of the production cycle. Two areas, 7 km apart, were compared. In one area parasitoids were released, whereas the other area was used as a control. During the 2nd year treatments were reversed. Fruit was sampled in commercial mango orchards and in backyard orchards to assess levels of parasitism in fruit fly larvae. Highly significant differences in percentage parasitism were found in release and control zones in backyard orchards. Furthermore, trapping results indicated that D. longicaudata releases were associated with ca. 2.7-fold suppression of Anastrepha spp. populations in backyard orchards. Results suggest that suppression might be affected by environmental conditions and by the parasitoid:fly ratio achieved. Anastrepha obliqua McQuart populations were suppressed more effectively by use of parasitoids than those of Anastrepha ludens Loew, perhaps due to the type of host fruits used by each species. Augmentative parasitoid releases in marginal areas surrounding commercial orchards (backyard orchards, wild vegetation) can substantially suppress fly populations. Through this approach, the number of flies that later move into commercial orchards can be significantly reduced. Such a strategy, when combined with sound orchard management schemes, can allow growers to produce clean fruit without the need to resort to the widespread use of insecticides.     

Diversity of flies (Diptera: Tephritidae and Lonchaeidae) in organic citrus orchards in the vale do Rio Caí, Rio Grande do Sul, southern Brazil

This study was carried out in the Counties of Montenegro and Pareci Novo located in the region of the Vale do Rio Cai, Rio Grande do Sul, Southern Brazil, aiming to determine the fruit fly species of Tephritidae and Lonchaeidae that occur in organic orchards of sweet orange [Citrus sinensis (L.) Osb.] cultivar Céu, and Murcott tangor (Citrus reticulata Blanco x C. sinensis), during the fruit ripening stages in 2003 and 2004. Eight McPhail traps baited with integral grape juice diluted to 25% were installed in four orchards, two in each citrus species. The traps were checked weekly, when the baits were changed, the flies separated and preserved in 70% ethyl alcohol. Fruits were also sampled from the orchards, placed in containers with damp soil and closed with a mesh. The tephritid flies represented 86.2% of all captured flies in the four orchards during both years. Five Tephritidae species were captured from traps: Anastrepha fraterculus (Wiedemann), Anastrepha grandis (Macquart), Anastrepha pseudoparallela (Loew), Anastrepha dissimilis Stone and Ceratitis capitata (Wiedemann). The captured species of Lonchaeidae were: Neosilba zadolicha McAlpine & Steyskal, Neosilba n.sp.3, Neosilba sp. and Lonchaea sp. Anastrepha fraterculus was found in 99% of the fruit samples, both in 'Céu' orange and 'Murcott' tangor, and Neosilba n.sp.3 were only obtained from 'Murcott' tangor fruits.     

枣园桃蛀果蛾寄生蜂种类及其与寄主的关系

桃蛀果蛾(Carposina sasakii Matsumura)是我国十分重要的果实性害虫,其中枣受害最严重,因其幼虫在果实内蛀食危害、高度隐蔽性的生活而较难防治。寻找有效天敌,开展生物防治成为必然。2009年与2010年研究调查了我国大枣部分产区陕西、山西、河南与宁夏枣园桃蛀果蛾寄生性天敌,共发现了3种寄生蜂,即中华齿腿姬蜂(Pristomerus chinensis Ashmead)、章氏小甲腹茧蜂(Chelonus(Microchelonus)zhangi Zhang)和金小蜂(Pteromalidae),3种寄生蜂均从桃蛀果蛾的茧中羽化而出,其中中华齿腿姬蜂和章氏小甲腹茧蜂为优势天敌,但它们表现出十分明显的地域性分布。同时,对中华齿腿姬蜂和章氏小甲腹茧蜂羽化、寄生率以及与寄主之间的关系进行了初步研究,结果表明,中华齿腿姬蜂越冬代成虫出蛰活动始于6月中旬,越冬代寄生率较低,第1代成虫羽化在8月下旬至9月上旬,这代寄生蜂具有较高的寄生率,可达25%;章氏小甲腹茧蜂第1代成虫羽化集中在8月中下旬和9月上旬,由于在2009年与2010年对样地进行不施用杀虫剂的管理,该天敌在2010年自然寄生率显著提高,最高时可达64.52%。因此,科学管理,合理保护与利用当地天敌成为实现该害虫生物防治的关键。     

Evaluation of a banker plant system for biological control of Bemisia tabaci (Hemiptera: Aleyrodidae) on tomato,using two aphelinid parasitoids under field-cage conditions

ABSTRACT

This study evaluated the potential of two aphelinid parasitoids, Encarsia sophia (Girault & Dodd) and Eretmocerus hayati (Zolnerowich & Rose) to control the sweetpotato whitefly Bemisia tabaci, (Gennadius) using a banker plant system over two consecutive years. The parasitism rates of both parasitoids on a tomato (Solanum lycopersicum L.) crop were determined using melon, Cucumis melo L. (Cucurbitaceae) and castor bean, Ricinus communis L. (Euphorbiaceae), as banker plants, respectively. The emergence rates of Er. hayati and En. sophia parasitoids from parasitised whiteflies on both banker plants exceeded 90% and 85%, respectively, which is 17–20 percentage points higher than that on the pupal card under field cage conditions. Parasitism (%) on banker plants was significantly higher for both parasitoids in the third week after release as compared to adult releases in the first year, reaching 15.2?±?1.3 and 24.0?±?1.4% for En. sophia and Er. hayati, respectively. However, no significant difference in parasitism (%) was observed between banker plant and pupal card release treatments in the second year. The combined release of the two parasitoids during the second year clearly showed a continuous increase in parasitism, which was higher than parasitism in the single parasitoid-release treatments by the 4th week after release. Whitefly populations were significantly lower in all parasitoid-release treatments than in the no-release control by 4–6 weeks into the study period in the second year, while no other significant differences were observed between treatments in either year. This study found that both banker plants efficiently supported populations of both parasitoids and improved their emergence compared to the pupal card.     

Weak parasitoid-mediated apparent competition between two Phyllonorycter (Lepidoptera: Gracillariidae) leaf miner species on a deciduous oak Quercus dentata

Parasitoid assemblages and the rates of parasitism on tissue-feeding larvae of two Phyllonorycter leaf miner species, P. persimilis and P. leucocorona , were studied from the autumn generation in 2002 to the summer generation in 2005 to understand whether parasitoids mediate interactions between the two leaf miner species. Fourteen species of parasitoids emerged from P. persimilis and 11 emerged from P. leucocorona . The parasitism rate was high: 24.1–92.6% in P. persimilis and 58.9–81.7% in P. leucocorona . Thus, parasitism was a major mortality factor in the present Phyllonorycter species. The parasitoid composition was distinctly different between the two host species, although most parasitoids were able to parasitize both leaf miner species. The analysis based on the quantitative parasitoid overlap revealed that the present parasitoids could mediate interactions between the present leaf miner species, but their effects would be weak. This is attributable to parasitoid's preferential uses of either of the leaf miners as a host.     

Spatial distribution of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) larvae in three scales.

The spatial distribution of larvae of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), the citrus leaf miner, in leaves, shoots, and tree crowns of Montenegrina tangerine (Citrus deliciosa Tenore) and Murcott tangor (Citrus sinensis L. Osbeck x Citrus reticulata Blanco) was determined. Fortnightly samplings from July/2001 to June/2003, in orchards located in Montenegro (29 degrees 68' S and 51 degrees 46' W), RS, Brazil, were carried out. At each sampling occasion eighth shoots randomly selected were collected. The spatial distribution pattern of P. citrella larvae between tree crowns and in the shoots was aggregated in most sampling occasions in both citrus species. Nevertheless, on the leaves, this pattern followed a random distribution, as indicated by the indices I, Idelta and k parameter.     

Egg parasitoids of Thaumetopoea pityocampa (Den. & Schiff.) (Lep., Thaumetopoeidae) and their impact in SW Turkey

Abstract: Egg parasitoids (Hym., Chalcidoidea) and egg parasitism were studied in 132 egg batches of the pine processionary moth collected from stands of Pinus nigra Arnold and P. brutia Ten. in SW Turkey, at four places in heights of 800–1010 m a.s.l. in October 1998, beyond the caterpillars’ hatch. The egg batches deposited on P. nigra were high‐significantly smaller than those found on P. brutia. In this mountainous regions, Baryscapus servadeii (Dom.) and Ooencyrtus pityocampae (Mercet) were the most abundant egg parasitoids of Thaumetopoea pityocampa (Den. & Schiff.). Considering the different sampling places, Trichogramma sp. was found maximally in 3.1% of the parasitized eggs. Additionally, the hyper‐parasitoid Baryscapusransversalis Graham (mean infestation 1.8%) and Pediobius bruchicida (Rond.) (0.1%), both occurring in both sexes, and Anastatus bifasciatus (Fonsc.) (0.1%), only females, were established. The primary parasitoid O. pityocampae dominantly parasitized the eggs placed near the top of the batches, and B. servadeii was found mainly in eggs near the base. The rate of parasitism of the egg batches was very variable. The impact of egg parasitoids and predators varied from 24 to 35.9% depending on the sampling place. The hatching rate of the caterpillars was reduced to 50.7–65.6%. Under laboratory conditions, the emergence dynamics of the parasitoids showed a peak of B. tranversalis in December of the year, in which the host eggs were laid. Baryscapus servadeii emerged mainly in March–May of the following year, when the second part of O. pityocampae appeared. A large part of both parasitoids emerged before sampling of the batches. In O. pityocampae 1.65% and in B. servadeii 2.23% males developed under laboratory conditions. A rate of 15.7% of O. pityocampae and 7.9% of B. servadeii died in the eggs. The polyembryonic Trichogramma sp. (see also Tsankov et al., 1996a ) attacked 1.8% of the eggs. Up to 20 (mean 12) dead pupae were found in one egg. Minor parts of eggs were undeveloped (2.9%) and 0.6% totally empty.     

Geissospermum argenteum (Angiosperma: Apocynaceae): a reservoir of parasitoids of fruit flies (Diptera: Tephritidae) in an upland forest in the Brazilian Amazon

1. This work aimed to assess the potential of Geissospermum argenteum Woodson (Apocynaceae) as a reservoir of fruit fly (Diptera: Tephritidae) parasitoids (Hymenoptera) in an upland forest in Brazil.
2. The study was conducted in a remnant of primary upland forest, in which were distributed 10 plots (0.5 ha each). All individuals of G. argenteum with diameters greater than 5 cm at a height of 1.3 m were inventoried. Two trees per plot were selected to assess the total production of fruit. Collectors were installed under the canopy projection of each tree. The fruits were counted and weighed in the field and were transported to the laboratory, to determine the dry mass. Samples of fruits were collected to investigate their infestation by fruit flies and percentage of parasitism.
3. A total of 394 specimens of G. argenteum were identified in the 5 ha investigated area, of which only 126 produced fruits during the 12 months of the assessment. Production ranged from 59 to 2478 fruits per plant (0.59 and 19.73 kg of fresh mass, respectively). Fifty-nine fruit samples were collected from 44 plants, from which 7703 puparia were obtained. Only Anastrepha atrigona Hendel emerged from the puparia. The mean infestation rate was 554.9 puparia/kg of fruit (0.4–1628.6 puparia/kg). Four species of parasitoids were obtained, with mean percentage of parasitism of 2.27% (0.23–9.01%).
4. Our results show that G. argenteum is a reservoir of fruit fly parasitoids, highlighting the importance of its conservation in native habitats, as well as its multiplication in areas close to commercial orchards.

     

Status of biological control by egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae) in citrus in Florida and Puerto Rico

Eggs of Diaprepes abbreviatus (L.) were routinely monitored in citrus groves at ten locations in Florida during 1997 and 1998 to study egg parasitism. One citrus location was studied in Puerto Rico. No native parasitoids were recovered from 1,337 D. abbreviatus egg masses studied in Florida citrus. In contrast, an average of 35.5% (range 12.5 to 68.8%) parasitism of egg masses was reported in Puerto Rico. The parasitoids Aprostocetus gala, Horismenus spp, and Quadrastichus haitiensis were recovered from the eggs of D. abbreviatusfstudied in Puerto Rico. The Horismenus parasitoids were suspected hyperparasitoids. Releases of the parasitoid Ceratogramma etiennei from Guadeloupe were initiated during 1998 at each of the Florida research sites. By the end of 1998, C. etiennei had been recovered from D. abbreviatus eggs at two of nine locations in Florida citrus. The parasitoid was recovered from 1 of 34 egg masses at one of these locations during the month of September and from 3 of 34 egg masses at the other location during the month of November. Whether or not C. etiennei establishes itself at one or more locations in Florida remains to be seen.     

Changes in predation and parasitism of the citrus leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) populations in Spain following establishment of Citrostichus phyllocnistoides (Hymenoptera: Eulophidae)

The citrus leafminer, Phyllocnistis citrella, is a pest native to Southeast Asia which threatened the citrus industry in the Mediterranean region upon its introduction in 1993. Immediately afterward, a classical biological control program was implemented in Spain. The exotic parasitoid Citrostichus phyllocnistoides was the only introduced parasitoid to become established. In 2006, data on both the incidence of P. citrella and the impact of its natural enemies were collected following the same protocols used in 1997–1999 when C. phyllocnistoides was not yet present. C. phyllocnistoides constituted 99.4% of the parasitoids collected in 2006 corresponding to a decrease in the incidence of P. citrella from 3.2–5.1 to 1.8–2.4 mines per leaf in 1997–1999 and 2006, respectively. Mortality caused by natural enemies on P. citrella in 2006 was 93.3% (18.0% parasitism, 40.8% feeding punctures and 34.5% predation). C. phyllocnistoides, which preferentially parasitizes P. citrella second instar larvae, has displaced most of the indigenous parasitoids that moved onto P. citrella mainly parasitizing third instar larvae, upon its introduction. Because C. phyllocnistoides is an idiobiont parasitoid and preferentially parasitizes P. citrella second instars, this stage has become dominant in the orchards. The shift in the relative abundance of P. citrella larvae has prompted generalist predators to prey mostly on second instars and has contributed to the displacement of the native non-specific parasitoids, which principally utilize third instars, from the system. Both indigenous predators and the introduced parasitoid are key players in the natural regulation of P. citrella.     

Comparison of Diadegma insulare (Hymenoptera: Ichneumonidae) and Microplitis plutellae (Hymenoptera: Braconidae) as biological control agents of Plutella xylostella (Lepidoptera: Plutellidae): field parasitism, insecticide susceptibility, and host-searching

Parasitism of Plutella xylostella (L.) third and fourth instars was evaluated in a cabbage field in Geneva, NY, in 1999. Over the entire season, average parasitism was 33.6% for third instars and 53.6% for fourth instars, and the main parasitoids were Diadegma insulare (Cresson) and Microplitis plutellae Muesbeck. In the early season, total parasitism was low, and mainly caused by D. insulare. However, later in the season, parasitism reached >80% for the fouth instars and 50% for the third instars. Our survey indicated that M. plutellae heavily parasitized P. xylostella, and provided higher parasitism rates than D. insulare in the late season. Comparison of these two species in laboratory bioassays indicated there were no significant differences in susceptibility to four insecticides commonly used in crucifer fields. For both parasitoids, an experience with P. xylostella on a damaged leaf increased their host-searching efficacy. Compared with M. plutellae, D. insulare was a better host-searcher both for the naive and the experienced adults. Although both parasitoids can cause high mortality rates of P. xylostella, D. insulare may be more suitable to be released in fields to enhance natural control against P. xylostella.