Rearing of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in order to multiply the parasitoid Semielacher petiolatus Girault.
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The present work has shown that a citrus leaf can support the nutritive needs of 5 individual P. citrella. Beyond this number of feeding larvae leaf mortality results as larval densities increase. An increasing number of female P. citrella (> 6 females per suitable leaf) adversely affects rearing due to competition for oviposition sites and resource limitation for developing larvae. To maximize efficient production of P. citrella, a quantitative relationship between ovipositing females, larval densities, and leaf quality needs to be determined. Our results indicate that one ovipositing female should have access to six leaves under rearing conditions. INTRODUCTION To control exotic pests, classical biological control attempts to seek in the pest’s original country its natural enemies (e.g., the case of Aleurothrixus floccosus) for release in the invaded territory. Classical biological control has been used for citrus leafminer in different countries that have been recently invaded over the period 1993-1995 (Heppner, 1993; Beattie and Smith 1993; Garijo and Garcia, 1994; Anagnou-veroniki, 1995; Berkani, 1995; Ortu and al., 1995; Argov and Rossler, 1996; Aytas and al., 1996; Jerraya et al., 1996). One major difficulty has been the mass rearing of leafminers to supply to parasitoids being used in the biological control program. To maximise rearing efficiency we have investigated the precise conditions needed for maximum leafminer multiplication to mass rear parasitoids for of augmentative releases. MATERIALS AND METHODS One hundred two year old plants (Poncirus trifoliata), maintained in greenhouses were selected for rearing studies, pinched, and isolated in one of three cages (A, B, and C). These plants were carefully looked after and subjected to fertigation and pinching to promote healthy continuous growth. Seventeen days after pinching, grown leaves become suitable for oviposition by P. citrella. When P. citrella was released into cages with plants there were approximately 500 leaves/cage for females. We introduced 40, 80 and 160 couples respectively in cages A, B and C on June 11, 2002. These cages were kept inside an experimental greenhouse where temperature and humidity were controlled (average temperature 30°C and RH 80-90 %) (after Smith and Hoy, 1995). One week after inoculation the first batch of oviposition occurred and we focused on % of mortality, rate of infestation, rate of eclosion, number of eggs, of larvae and of pupae in each cage. This was followed a second set of observations done one week later (i.e., 15 days post-inoculation on June 25 2002). Statistical analyses were done using (SAS, 2000). RESULTS AND DISCUSSION P. citrella offspring 7 days after inoculation – Table 1 We found that: 1) The rate of P. citrella eclosion was the same whatever the cage density. This means that the activity of laying starts almost in a simultaneous manner for all the females and that the duration of incubation was comparable across the three cages stocked with different densities of ovipositing females. 2) The absence of the third instar larva in the three cages shows either there is a delay in oviposition or that the conditions of the cages were not favourable for rearing as under optimal conditions, the duration of the egg stage and first instar larva (L1) are 2 days and 1 day, respectively. 3) If the density of initial inoculation affects the rate of female oviposition in cages, we can say that this capacity is about 97 % in the cage A, 73% in the cage B, and declines to 59 % in the cage C. This suggests that increasing the density of ovipositing females in cages adversely affects oviposition rates. 4) Numbers of eggs laid per leaf were 5, 9, 18 in the cages A, B and C, respectively. Consequently survivorship rates of first and second instar larvae were affected, most likely a result of overpopulation and resource depletion which resulted in mortality rates of 6%, 65% and 79% for cages A, B and C, respectively. Oviposition deterring pheromones applied to leaves on which have freshly deposited eggs do not deter further oviposition by females under crowded conditions. 5) P. citrella has a male:female sex ratio of 1:1. Therefore, we can estimate that the number of females produced per cages was 40 in cage A, 80 in cage B and 160 in cage C. These female populations, laid 2470 eggs (494 x 500), 4720 (944 x 500) and 8975 eggs (1795 x 500) in cages A, B, and C, respectively. In this way, we calculated the fecundity per female per cage as 61 for cage A, 59 for cage B, and 56 for the cage C. The differences between the fecundity values were not significant and were similar to values considered as being around the average fecundity for female P. citrella.Keywords:
Gracillariidae
Eulophidae
Encyrtidae
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Biological study of Orius minutus (L.) when fed with Thrips spp., egg of Corcyra cephalonica (Stainton) and Tetranychus spp. revealed that the total development of the 1st, 2nd, 3rd, 4th and 5th nymphal stages were 7.67+-1.11, 8.16+-1.54 and 10.52+-1.12 days, respectively while those of the female were 17.21+-2.83, 18.71+-2.87 and 6.64+-2.31 days, respectively and the male were12.82+-2.23, 16.45+-1.51 and 5.82+-2.23 days, respectively. These indicated that Thrips spp. and egg of C. cephalonica suited for mass-rearing process of Orius sp. The biological life table of O. minutus were constructed and the population statistics obtained were the net reproductive rate (R sub(0)) =4.2266 and 7.125, the capacity for increase (r sub(c))=0.086 and 0.3646, the finite rate of increase(lambda) = 1.0898 and 1.44 and the cohort generation time(T sub(c)) = 16.7598 and 13.4386 days when fed with Thrips spp. And C. cephalonica eggs, respectively.
Anthocoridae
Heliothis
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The citrus mealybug, Planococcus citri (Risso) was found in large numbers infesting custard apple at Indian Institute of Horticultural Research Farm, Bangalore during August-October 2004. Sampling of infested custard apple fruits during this period revealed the presence of Leptomastix dactylopii Howard. Adult parasitoids were recovered after five years of its release in 1983 and again in 2004 in the present study indicating the permanent establishment. In general, the activity of parasitoids particularly on mealybugs on custard apple was very low. The natural parasitisation by L. dactylopii ranged from 0.41 to 2.72 percent but the presence of L. dactylopii indicated that there is some scope of exploiting L. dactylopii in the suppression of P. citri infesting custard apple.
Custard-apple
Mealybug
Encyrtidae
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Whitefly
Aphelinidae
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The sweetpotato whitefly, Bemisia tabaci, is a pest of greenhouse-grown tomato. Restrictions on insecticides in enclosed structures and the presence of commercial pollinators limit the options for the chemical control of whiteflies in greenhouses, increasing the importance of biological controls. Dicyphus hesperus is a zoophytophagous mirid predator native to North America. Three release rates of D. hesperus were evaluated on greenhouse tomato for control of the sweetpotato whitefly. The release rates were one, two or three adult D. hesperus per tomato plant each week for three weeks in cages containing four tomato plants and one mullein banker plant. There were fewer whitefly eggs in cages receiving predators than untreated cages one week after the third release, and fewer whitefly nymphs in cages receiving predators two weeks after the third release. There were no statistical differences in whitefly eggs or nymphs among predator release treatments. The highest release rate resulted in a 60% reduction in whitefly nymphs. Forty-two days after the first predator releases, there were no differences among release treatments in the number of D. hesperus. Our results indicate that D. hesperus can contribute management of B. tabaci on greenhouse tomato, but that it may be insufficient as a sole strategy.
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Se evaluó el efecto de depredación de Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae) sobre ninfas de Diaphorina citri Kuwayama (Hemiptera: Liviidae) mantenidas en condiciones experimentales para la cría de Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae). Se realizó un ensayo empleando jaulas con capacidad para 9 plantas de Murraya paniculata (L.) Jack (Rutaceae) infestadas con un promedio de 600 ninfas de D. citri y 100 adultos de T. radiata por jaula. Tres jaulas fueron expuestas a las hormigas y una sin exposición (Control). En cada jaula se contabilizó el número de ninfas sanas y parasitadas y el número de adultos de D. citri y T. radiata, cada 2 días durante 15 días. La exposición a la depredación por W. auropunctata afectó de forma significativa el número de ninfas que alcanzaron el estado adulto y el número de ninfas parasitadas por T. radiata (prueba exacta de Fisher). En las jaulas expuestas, cerca del 3% de las ninfas sobrevivieron al estado adulto en contraste con 18% en la jaula control. De igual manera se vio afectada la acción del parasitoide, con un 24% de ninfas parasitadas en las jaulas expuestas en contraste con 66% en la jaula control. Wasmannia auropunctata tiene gran potencial como controlador de esta plaga en viveros de cítricos. La hormiga también consume T. radiata de forma indirecta al consumir ninfas de D. citri parasitadas.
Diaphorina citri
Radiata
Eulophidae
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Following the introduction of Nezara viridula (L.) into North America, the native parasitoid tachinid fly Trichopoda pennipes Fabr. became one of its natural enemies (Jones 1988). Approximately fifteen years ago, T. pennipes was accidentally introduced into Italy in the vicinity of Rome, probably by overseas shipments carrying N. viridula (Colazza et al. 1996). It has since spread rapidly across the Italian peninsula, colonizing first the coastal areas (Solarno et al 2002) and is nowadays relatively common in Italy. Since Nezara viridula is a good disperser (Knight and Gurr 2007), it was only a matter of time before T. pennipes was to be found in Slovenia. The members of the Department of Entomology of the National Institute of Biology have been collecting N. viridula since the beginning of the nineties in the area of Koper (x = 43065.9, y = 401387.3) and Piran (x = 43182, y = 389843), in 2005 also in Mirensko polje (field of Miren) near Nova Gorica (x = 84069, y = 391793) and in 2006 in Mance in the Vipava valley (x = 75669, y = 417956). N. viridula was collected by beating bushes (not always: not in Mance or Miren) and caught from the beating sheet. Both adults and 4th instar nymphs were collected. T. pennipes was found in Koper, Piran and the area of Nova Gorica. The first parasitized animals in Koper were found in the autumn of 2003. In the years 2004 and 2005 parasitized animals were collected also in Piran. However, in 2006, we collected in Piran only one not-parasitized pair of N. viridula. In the area of Nova Gorica we found T. pennipes in 2005. On 18 October 2006, we found in Koper that 77 of the 497 adult N. viridula were parasitized. Of these, 24 females (approx. 0% of the female population) and 53 males (approx. 20% of the male population) were parasitized with T. pennipes. This is in accordance with the parasitization rate during the early years of the introduction into Italy (Solarno et al. 2002). Under laboratory conditions (20-23°C, 18L:8N), 9 maggots emerged from 25 parasitized females. The duration of the pupal stage ranged from 4 to 9 days, only 0 adults emerged. The distribution of T. pennipes is expected to correspond to be the same as the distribution of its host, N. viridula, which covers the Primorska region as far north as Tolmin (pers. comm. A. Gogala and M. Gogala). The consequences of the introduction of such an alien parasitoid or predatory species on the native fauna are well surveyed and can have the potential to be disastrous (Johnson et al 2005, Koch 2003). In Italy, T. pennipes was not found to have any hosts other than N. viridula (Solarno et al. 2002). However, related Trichopoda species introduced to Australia and Hawaii were found to be also attacking native pentatomid species (Sands and Coombs 1999, Johnson et al. 2005). Although it has been shown that population numbers of the economically important pest N. viridula can decline dramatically due to Trichopoda parasitoids (Coombs 2002), it has to be taken into account that T. pennipes is a generalist and will probably not only affect the target host. We therefore, suggest monitoring this species; investigations of its distribution and its effect on N. viridula and other pentatomid species are urgently needed.
Nezara viridula
Tachinidae
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Populations of the blackmargined pecan aphid, Monellia caryella (Fitch), were studied in the field, using sleeve cages to manipulate aphid populations and their natural enemies. Each cage enclosed 10 compound pecan leaves. M. caryella populations were observed to increase rapidly within closed cages from 1 aphid per leaf to 50 aphids per leaf at any time throughout the summer. Opening sleeve cages to allow natural enemies access to the increasing aphid populations always resulted in the decline of aphid numbers compared to their activity in adjacent closed cages. Release of 1 chrysopid or 1 coccinellid larvae per 10 leaves when aphid populations were increasing in closed cages always resulted in the prevention of an aphid outbreak. Laboratory feeding studies of selected chrysopid and coccinellid predators showed average feeding rates of between 25 and 60 aphids per day. Results indicate that natural enemies, particularly predators, play an important role in maintaining M. caryella populations at low levels in the field.
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During four growing periods from 1986 to 1989, biological pest control on capsicum was investigated in glasshouses under practical conditions. Aphids, mainly Myzus persicae , caused the most serious pest problems. As biological control agents, the commercially available predatory gall midge Aphidoletes aphidimyza and the green lacewing Chrysoperla curnea were used. Both these natural enemies were released according to the recommendations of the producers. For the releases of the gall midges, small peat samples containing the pupae of the predator were placed at a few spots in the glasshouse (1–2 pupae per m 2 ). The lacewings were introduced as eggs on small mesh‐pieces which were placed on every second plant (10–20 eggs per m 2 ). In these experiments, control of the aphid populations was effective only if the two predators were introduced early and were released several times. During the summer, other natural enemies such as parasitic wasps, syrphids, ladybirds and predatory bugs immigrated from outdoors and enhanced the biological control of aphids.
Myzus persicae
Cecidomyiidae
Beneficial insects
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Abstract In studies in Massachusetts, the population density of Brevicoryne brassicae (L.) was measured over the lifespans of two groups of kale leaves from maturation to senescence, taking into consideration aphid spatial pattern (in colonies or as isolated insects) and aphid size as large (adults), medium-sized (nymphal instars 2–4) or small (first-instar nymphs) individuals. Total aphid densities per leaf in both leaf groups showed similar patterns of initial increase followed by a decrease as leaves aged over the 3–4-week period of leaf survival. Aphid densities reached peak values of 8·14 and 8·64 aphids per leaf for the two leaf groups studied, and 65–67% of all aphids observed occurred in colonies. Host and parasitoid recruitment to the aphid and the parasitoid immature populations were measured using a modification of the technique of Van Driesche & Bellows (1988). Total host recruitments per leaf were 43·7 and 64·6 aphids for the first and second leaf groups. Parasitoid recruitment was 6·8–8·1 for the first leaf group and 8·2–15·8 for the second. Recruitment values indicated 15·6–18.6% parasitism for the aphid cohort on the first leaf group and 12·7–24·4% for that on the second one.
Brevicoryne brassicae
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In organically grown sweet peppers, aphids are the most important pest. The wide range of natural enemies of aphids, that are commercially available, is not a guarantee for successful control but rather an indication that this problem is difficult to tackle. Strategies for control vary among organic growers and it is still not known which natural enemy complexes give the best results. When releasing natural enemies for aphid control, it is important to consider the possible interactions with other pest species and natural enemies present. Within man-made natural enemy communities for multiple pest control, direct and indirect interactions occur which can enhance or disrupt biological control, such as predators eating other predators, behavioural changes, plant responses or apparent competition. Here we investigated the effects of the generalist predatory bugs Orius laevigatus and Orius majusculus on biological control of green peach aphids, Myzus persicae, by the predatory midge Aphidoletes aphidimyza in the absence or presence of thrips. Our results showed that intraguild predation of aphidophageous midges by generalist predatory bugs is a realistic phenomenon, but the risk of disruption of aphid control seems to be limited. The addition of thrips and O. majusculus to predatory midges even enhanced the suppression of aphids. We conclude that a broad system view with predator-prey complexes is required for identifying successful natural enemy complexes for aphid control. INTRODUCTION Aphids are the most destructive pest species in organically grown sweet peppers. The green peach aphid, Myzus persicae (Sulzer), especially the red phenotype, is notorious for its fast reproduction and tendency to colonize flowers and young leaves. This behaviour directly results in reduction in growth of the plant and fruit production. Moreover, the honeydew secreted by these aphids pollutes leaves and fruit, which consequently facilitates growth of sooty mould. Another damaging aphid species in sweet pepper is the foxglove aphid, Aulacorthum solani (Kaltenbach). This species typically induces strong plant responses such as yellow necrotic spots and leaf deformation, which can occur at low aphid densities. At higher densities, aphid-induced damage can result in leaf drop. Biological control of these aphids is mainly based on weekly releases of the parasitoids, Aphidius colemani Viereck and Aphidius ervi Haliday, and the predatory midge, Aphidoletes aphidimyza (Rondani). Additionally, growers release the slower reproducing wasps Aphelinus abdominalis (Dalman) and chrysopid, syrphid or coccinellid predators. Despite releases of mulitple natural enemies, biocontrol programs often do not succeed. One reason could be that these natural enemies interact with biocontrol agents that are released to control other pest species, such as generalist predatory mites and predatory bugs for the control of thrips. We recently showed that predatory mites strongly disrupt the biological control of aphids using the predatory midge, A. aphidimyza, because of hyperpredation of the midge eggs (Messelink et al., a Gerben.messelink@wur.nl Proc. First IC on Organic Greenhouse Hort. Eds.: M. Dorais and S.D. Bishop Acta Hort. 915, ISHS 2011 172 2011). Another threat for predatory midges could be the predation by generalist Orius bugs, which are mainly used for controlling thrips. These predators are known to feed not only on thrips, but also on aphids and the aphidophagous predator A. aphidimyza (Christensen et al., 2002). Such interactions have been referred to as intraguild predation (Fig. 1), which occurs when one predator species (the intraguild predator) kills and eats another predator species (the intraguild prey) with whom it also competes for shared prey (Polis et al., 1989; Holt and Polis, 1997). In theory, intraguild predation can disrupt biological control (Rosenheim et al., 1995), but in practice, results are mixed (Janssen et al., 2006, 2007; Vance-Chalcraft et al., 2007). Here we examine the effects of Orius laevigatus (Fieber) and Orius majusculus (Reuter) on the biological control of aphids with predatory midges in the presence of thrips as an alternative prey for Orius. Furthermore, we discuss the role of species interactions in developing management strategies for aphid control in sweet pepper. MATERIALS AND METHODS Rearing Sweet pepper plants, Capsicum annuum L. ‘Ferrari’ (Enza Zaden), were grown in rockwool blocks in a greenhouse compartment. We used the red phenotype of the green peach aphid, M. persicae, which was cultured on sweet pepper plants. Western flower thrips, Frankliniella occidentalis (Pergande), were cultured on flowering chrysanthemum plants, ‘Mirimar’. The predatory midge, A. aphidimyza, and predatory bug, O. laevigatus (Fieber), were obtained from Koppert Biological Systems (Berkel en Rodenrijs, The Netherlands), whereas the predatory bug, O. majusculus, was obtained from Biobest NV (Westerlo, Belgium). Greenhouse Experiment A cage experiment was carried out to assess the effects of predatory bugs on the suppression of aphids, in the presence of the predatory midge A. aphidimyza. Thrips were introduced to a subset of cages to provide an alternative prey for the predatory bugs. Individual flowering sweet pepper plants, ca. height 30 cm with 15–17 leaves, were put into a single cage (diameter 30 cm, height 40 cm, top with side-openings covered with insect gauze). Cages were placed on tables and maintained, at an average of 21°C, in one greenhouse compartment. The lower plant stem and roots in rockwool extended through a sealed hole at the bottom of the cages in order to allow automatic supply of a standard nutrient solution with an ebb-and-flow system. There were 8 treatments, with 4 replicates per treatment: (1) aphids only, (2) aphids + O. laevigatus + thrips, (3) aphids + O. majusculus + thrips, (4) aphids + A. aphidimyza, (5) aphids + A. aphidimyza + O. laevigatus, (6) aphids + A. aphidimyza + O. majusculus, (7) aphids + A. aphidimyza + O. laevigatus + thrips and (8) aphids + A. aphidimyza + O. majusculus + thrips. Each plant was infected with 20 aphids of mixed age, which were collected with a fine brush from the culture on sweet pepper. Adult thrips were introduced three times in the destined treatments in densities of 20, 20 and 40 females per plant after 1, 11 and 23 days post aphid release, respectively. Repeated releases of thrips were necessary because thrips proved to be controlled effectively. The predatory midge A. aphidimyza was introduced 10 days after aphid release by adding 10 pupae per cage in humid vermiculite. The adult midges emerged within 4 to 7 days, and no mortality of pupae was observed. Ten adult female predatory bugs were introduced 17 days after aphid release in each cage. The densities of all insects were assessed once, 28 days after aphid release, by checking all parts of each plant under a stereomicroscope (40x). For statistical analyses, we performed a standard ANOVA on the log transformed densities of insects. Differences among treatments were tested at the 5% level using Fisher’s Least Significant Difference (LSD) method.
Intraguild predation
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