Mealybug avoidance responses to ladybird semiochemicals

The predatory ladybird Cryptolaemus montrouzieri Mulsant is a very effective natural enemy of the citrus mealybug, Planococcus citri (Risso), and has a worldwide distribution. This study investigated how the citrus mealybug responded to semiochemicals from the ladybird. In laboratory experiments, mealybug response to semiochemicals left by ladybirds on leaf surfaces was measured. The results indicated that the presence of ladybirds can change the settling behaviour of P. citri. The exposure of plant material to C. montrouzieri had a significant influence on the settling of mealybugs added to the same plant. The distribution of citrus mealybugs in the Petri dishes was significantly affected by the previous presence of ladybirds. The avoidance response may aid in the biological control of mealybugs by coccinellids released onto crops infested with mealybugs.     

Intraguild predation of Planococcus ficus parasitoids Anagyrus pseudococci and Leptomastix dactylopii by Nephus kreissli

Intraguild predation of the mealybug parasitoids Anagyrus pseudococci (Girault), and Leptomastix dactylopii Howard (Hymenoptera: Encrytidae) by Nephus kreissli Fürsch & Uygun (Coleoptera: Coccinellidae) was studied. The latter is a native predator of the important pest Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae) on grapevines in Turkey. For this purpose, P. ficus of different ages parasitised by A. pseudococci or L. dactylopii, or by both A. pseudococci and L. dactylopii, were served to fourth instars and adults of N. kreissli as food. Experiments were conducted using two different treatments: no-choice (served unparasitised or only one stage of parasitised mealybug) and choice (served unparasitised and only one age of parasitised mealybug together), under controlled environmental conditions. Both fourth instars and adult predators were fed on two- and four-day-old mealybugs parasitised by A. pseudococci or on two-, four- and six-day-old mealybugs parasitised by L. dactylopii or by either A. pseudococci or L. dactylopii. The predators could not consume six-day-old mealybugs parasitised by A. pseudococci, eight-day-old mealybugs parasitised by L. dactylopii, or those parasitised by either of these parasitoids which had become mummified. While it was found that the adult predators preferred parasitised mealybugs to unparasitised, the larvae did not show a pronounced preference between parasitised and unparasitised mealybugs (except for mealybugs parasitised by A. pseudococci).     

Host selection behaviour and specificity of the solitary parasitoid of mealybugs Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera,Encyrtidae)

The host selection behaviour of Anagyrus sp. nr. pseudococci was compared in no-choice tests among five mealybug species of different geographical and phylogenetic origin, including the Mediterranean native host, Planococcus ficus and four exotic mealybug species, one of the same genus, Pl. citri, two Pseudococcus species, Ps. calceolariae and Ps. viburni and a more distant one, Phenacoccus peruvianus. All five studied mealybug species were recognised by the parasitoid as potential hosts and parasitised, but the behavioural pattern of host recognition, host handling and the level of host acceptance of Anagyrus sp. nr. pseudococci significantly varied among the five studied species, indicating a clear preference for the two Planococcus species, Pl. ficus in particular. The results suggest that A. sp. nr. pseudococci has a broader host range and a more generalist behaviour in comparison with other Anagyrus species. Practical implications of the findings are discussed.     

Spatial distribution of ants (Hymenoptera: Formicidae), vine mealybugs and mealybug parasitoids in vineyards

The mutualistic association between some ant species and honeydew‐producing Hemiptera has been shown to influence the distribution patterns and abundance of these hemipterans and their natural enemies. We studied the spatial distribution patterns of three ant species, mealybugs and mealybug parasitoids for two consecutive growing seasons on three wine grape farms in the Western Cape, South Africa. During the study period, no ant or mealybug controls were applied. Ant and mealybug monitoring was conducted on a total of 21 ha using a presence/absence sampling system, while parasitoids were collected from infested mealybug females. Spatial analysis by distance indices was used to analyse spatial distribution of insects and ArcView? was used to map the gap, patch and local association indices where significant association and disassociation occurred. Significant associations were found between some ants and parasitoids, while significant disassociations between the ants Crematogaster peringueyi and Linepithema humile; and also between Crematogaster peringueyi and Anoplolepis steingroeveri were found. Interspecific competition between ant species could play a role in the distribution of parasitoids and mealybugs. Our results stress the importance of monitoring for ants and mealybugs and further highlight the importance of restricted chemical applications against ants during the growing season.     

Developmental time,longevity, reproductive capacity and sex ratio of the mealybug parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

Key biological parameters of Anagyrus sp. nr. pseudococci reared on the citrus mealybug Planococcus citri (Risso) were determined. The mean longevity of female wasps was 21.1 days, the median lethal time (LT₅₀) was 22 days, the mean number of offspring per female was 30.2 wasps and the sex ratio of the progeny was slightly male biased (1.1 males per female). Wasps fed with water showed a significantly lower longevity compared to that recorded for wasps fed with syrup for bee nutrition mixed with water. The longevity of female wasps was significantly higher compared to males when the syrup-water solution was provided as food. Longevity was significantly higher for female wasps fed with syrup and water in comparison with those exposed to host mealybugs. The mean development time of female and male wasps was 14.7±0.1 and 14.5±0.1 days, respectively.     

Asymmetrical intraguild predation between natural enemies of the citrus mealybug

The ability of a predator to discriminate against parasitized prey determines the extent of asymmetrical intraguild predation, which is often crucial for the outcome of biological control. Anagyrus nr. pseudococci (Girault) (Hymenoptera: Encyrtidae), a parasitoid of the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), suffers from intraguild predation by coccinellids occurring in the same habitat. The level of intraguild predation on A. nr. pseudococci by Nephus includens (Kirsch) (Coleoptera: Coccinellidae) at different immature stages has been investigated with and without simultaneous offer of extraguild prey. Larvae of A. nr. pseudococci appeared to face increased intraguild predation at early developmental stages, whereas mummification provided adequate protection against the predatory coccinellid. Different predation levels on unparasitized vs. parasitized hosts at various developmental stages in choice assays indicated that N. includens preferences might be determined not solely by palatability of the prey but also by its ability to protect itself.     

Specificity of <Emphasis Type="Italic">Anagyrus</Emphasis> sp. nov. nr. <Emphasis Type="Italic">sinope</Emphasis> and <Emphasis Type="Italic">Leptomastix dactylopii</Emphasis> for six mealybug species

In order to understand better non-target effect and potential uses, the host specificity of two parasitoid species (Anagyrus sp. nov. nr. sinope Noyes & Menezes and Leptomastix dactylopii Howard) (both Hymenoptera: Encyrtidae) for six mealybug species [Ferrisia virgata (Cockerell), Phenacoccus madeirensis Green, Phenacoccus solani Ferris, Planococcus citri (Risso),Pseudococcus longispinus (Targioni-Tozzetti) and Pseudococcus viburni (Signoret)] (all Hemiptera: Pseudococcidae) was studied through behavioral observations and laboratory rearing. The selected mealybug species represent major subfamilies and tribes of Pseudococcidae. Except for F. virgata, all mealybug species induced examinations by Anagyrus sp. nov. nr. sinope and L. dactylopii. Anagyrus sp. nov. nr. sinope was specific to P. madeirensis, which was the only mealybug species selected for oviposition and suitable for complete development of the parasitoid. No encapsulation of Anagyrus sp. nov. nr. sinope in P. madeirensis was observed. Leptomastix dactylopii accepted multiple species for oviposition, with the ranking of species preference as P. citri > P. viburni > P. longispinus > P. solani > P. madeirensis. Only P. citri, P. longispinus and P. viburni supported the development of L. dactylopii. Parasitoids developing in P. longispinus and P. viburni suffered from high encapsulation rates, while no encapsulation was observed when developing in P. citri. The results of this study suggest that Anagyrus sp. nov. nr. sinope is highly host specific. Leptomastix dactylopii, on the other hand, has a wider host range. The use of Anagyrus sp. nov. nr. sinope in a mealybug biological control program is limited to P. madeirensis and L. dactylopii to P. citri. The results presented in this study also lead us to question the accuracy of the reported host range of L. dactylopii, which include all six mealybug species tested.     

Progeny production and adult longevity of the mealybug parasitoidsAnagyrus pseudococci,Leptomastix dactylopii,andLeptomastidea abnormis [Hym.: Encyrtidae] in relation to temperature

Progeny production increased and adult longevity decreased with rising temperature within the range 18°C to 30°C for the 3 mealybug parasitoidsAnagyrus pseudococci (Girault),Leptomastix dactylopii Howard andLeptomastidea abnormis (Girault). The Weibull distribution gave a good fit to survival curves for the 3 parasitoids and statistical comparison of Weibullb andc parameters at different temperatures allowed changes in the scale and shape of the curves to be detected. In general, ♀♀ lived longer than ♂♂ for all 3 species, except at high temperature. FemaleL. abnormis attained their maximum progeny production at 24°C and maintained this level up to 34°C. They lived longer than the other 2 parasitoid species at 30°C and showed a type I survival curve throuhout the range of temperatures examined.A. pseudococci andL. dactylopii both required high temperatures (30°C) to attain their maximal progeny production, but werepseudococci tended towards type II, with a larger proportion of the population dying within the first few days.L. dactylopii lived longest at 26°C, with ♀♀ showing a type I survival curve at all temperatures and ♂ survival curves changing from type I to type II at 30°C. The implications of these findings for the population dynamics of the different parasitoids are briefly discussed.      

Impacts of Argentine ants on mealybugs and their natural enemies in California's coastal vineyards

Abstract 1. The Argentine ant, Linepithema humile, tends honeydew‐excreting homopterans and can disrupt the activity of their natural enemies. This mutualism is often cited for increases in homopteran densities; however, the ant’s impact on natural enemies may be only one of several effects of ant tending that alters insect densities. To test for the variable impacts of ants, mealybug and natural enemy densities were monitored on ant‐tended and ant‐excluded vines in two California vineyard regions. 2. Ant tending increased densities of the obscure mealybug, Pseudococcus viburni, and lowered densities of its encyrtid parasitoids Pseudaphycus flavidulus and Leptomastix epona. Differences in parasitoid recovery rates suggest that P. flavidulus was better able to forage on ant‐tended vines than L. epona. 3. Densities of a coccinellid predator, Cryptolaemus montrouzieri, were higher on ant‐tended vines, where there were more mealybugs. Together with behavioural observations, the results showed that this predator can forage in patches of ant‐tended mealybugs, and that it effectively mimics mealybugs to avoid disturbance by ants. 4. Ant tending increased densities of the grape mealybug, Pseudococcus maritimus, by increasing the number of surviving first‐instar mealybugs. Parasitoids were nearly absent from the vineyard infested with P. maritimus. Therefore, ants improved either mealybug habitat or fitness. 5. There was no difference in mealybug distribution or seasonal development patterns on ant‐tended and ant‐excluded vines, indicating that ants did not move mealybugs to better feeding locations or create a spatial refuge from natural enemies. 6. Results showed that while Argentine ants were clearly associated with increased mealybug densities, it is not a simple matter of disrupting natural enemies. Instead, ant tending includes benefits independent of the effect on natural enemies. Moreover, the effects on different natural enemy species varied, as some species thrive in the presence of ants.     

Parasitoids of obscure mealybug,Pseudococcus viburni (Hem.: Pseudococcidae) in California: establishment of Pseudaphycus flavidulus (Hym.: Encyrtidae) and discussion of related parasitoid species

To improve natural suppression of the obscure mealybug, Pseudococcus viburni (Signoret), the parasitoids Pseudaphycus flavidulus (Brèthes) and Leptomastix epona (Walker) (Hymenoptera: Encyrtidae) of Chilean origin were released in California's Central Coast vineyards from 1997 to 1999. A survey for parasitoids of P. viburni was conducted in the Edna Valley appellation wine grape region from 2005 to 2007, 6–8 years after classical biological control releases were discontinued. Two survey methods were used. First, field collections of obscure mealybugs from commercial vineyard blocks (2005–2007) and, second, placement of “sentinel mealybugs” on potted (1 L) grape vines (2006 only). From both survey methods, P. flavidulus was recovered, albeit levels of parasitism were low (less than 0.6%). We also placed longtailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), on potted plants concurrent with placement of sentinel obscure mealybugs in the vineyard in order to measure parasitoid activity on this closely-related mealybug species. No P. flavidulus were recovered from P. longispinus. Other encyrtid parasitoids reared from either P. viburni or P. longispinus were Anagyrus pseudococci (Girault), Leptomastix dactylopii Howard, Leptomastidea abnormis (Girault), Coccidoxenoides perminutus Girault, and Tetracnemoidea peregrina (Compere). A hyperparasitoid, Chaetocerus sp., was also reared. The data are discussed with respect to biological control of vineyard mealybugs and newly developed controls for the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae). Because Pseudaphycus species reared from mealybugs are superficially very similar a taxonomic key and discussion of host relationships for selected Pseudaphycus species are provided.     

Cryptolaemus montrouzieri as a predator of the striped mealybug,Ferrisia virgata,reared on two hosts

The striped mealybug, Ferrisia virgata (Cockerell) (Hemiptera: Pseudococcidae), is a cosmopolitan pest of a variety of agricultural crops including cotton. To investigate the biological control potential of the predatory ladybird Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) against this pest, we evaluated its developmental and reproductive fitness when feeding on F. virgata reared on pumpkin fruits or on cotton leaves and compared this to a diet of Planococcus citri Risso (Hemiptera: Pseudococcidae) reared on pumpkin fruits. F. virgata and P. citri reared on pumpkins were equally suitable prey for the pre‐imaginal stages of C. montrouzieri. Duration of total immature development was 1 day longer in C. montrouzieri offered F. virgata reared on cotton as compared with F. virgata or P. citri reared on pumpkin, whereas no significant difference was observed in survival rates. Diet significantly influenced the reproductive fitness of C. montrouzieri. Females offered P. citri reared on pumpkin had significantly shorter pre‐oviposition periods and higher fecundity and fertility than those given F. virgata reared on pumpkin or cotton leaves. F. virgata grown on cotton leaves supported the reproduction of C. montrouzieri better than F. virgata reared on pumpkin. Our study established that C. montrouzieri can successfully complete its development and reproduction when fed exclusively on F. virgata and indicates its potential as a biological control agent of this emerging cotton pest.     

Suitability of five mealybug species (Hemiptera,Pseudococcidae) as hosts for the solitary parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

Anagyrus sp. nr. pseudococci is an endoparasitoid which has been used as a biological control agent of mealybug pests. In this study, we compared the suitability of five mealybugs species with different phylogenetic relationships and geographical origins as hosts of this parasitoid. The selected mealybugs were: (1) a Mediterranean-native species, Planococcus ficus, sharing a long co-evolutionary history with the parasitoid; (2) three exotic species, the Afrotropical Planococcus citri, the Australasian Pseudococcus calceolariae and the Neotropical Pseudococcus viburni, with a recent history; and (3) the Neotropical Phenacoccus peruvianus, with no previous common history with the parasitoid. Host suitability was assessed based on different fitness parameters, such as body size, developmental time, emergence rate and sex ratio. The parasitoid was able to complete development in all mealybug species. Nevertheless, its emergence rate significantly varied among mealybug species, with the highest values observed in Pl. ficus and Pl. citri, intermediate values in Ps. calceolariae and the lowest ones in Ps. viburni and Ph. peruvianus. The body size of adult wasp females varied with host suitability and was positively correlated with other measures of parasitoid fitness, including the emergence rate and the sex ratio. The parasitoid developmental time differed among mealybug species but did not correlate with any other measure of fitness. A female biased sex ratio was found in the parasitoid progeny emerged from all mealybug species, except in Ps. viburni and Ph. peruvianus. There was a direct relationship between the proportion of females in the parasitoid progeny and the emergence rate.     

Defense Response of Native and Alien Mealybugs (Hemiptera: Pseudococcidae) Against the Solitary Parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

The host behavioral and immune (encapsulation) defenses against the parasitoid Anagyrus sp. nr. pseudococci were compared for five mealybug species with different phylogenetic relationships and geographical origins: i) a Mediterranean native mealybug species, Planococcus ficus, with a long co-evolutionary history with the parasitoid; ii) three alien mealybugs species, Planococcus citri, Pseudococcus calceolariae and Pseudococcus viburni, with a more recent co-evolutionary history; and iii) a fourth alien mealybug species, Phenacoccus peruvianus, with no previous common history with the parasitoid. Three host defense behaviors were registered: abdominal flipping, reflex bleeding and walking away. The native host Pl. ficus and its congener Pl. citri exhibited the lowest probability of defense behavior (0.11?±?0.01 and 0.09?±?0.01 respectively), whereas the highest value was observed in P. viburni (0.31?±?0.02). Intermediate levels of defense behavior were registered for Ps. calceolariae, and Ph. peruvianus. The probability of parasitoid encapsulation was lowest and highest for two alien host species, Ph. peruvianus (0.20?±?0.07) and Ps. viburni (0.86?±?0.05), respectively. The native host Pl. ficus, its congener Pl. citri and Ps. calceolariae showed intermediate values (0.43?±?0.07, 0.52?±?0.06, and 0.45?±?0.09, respectively). The results are relevant with respect to biological control and to understand possible evolutionary processes involved in host range of A. sp. nr. pseudococci.     

The passionvine mealybug,Planococcus minor (Maskell) (Hemiptera: Pseudococcidae), and its natural enemies in the cocoa agroecosystem in Trinidad

Planococcus minor (Maskell) is native to South Asia, but it is also present in several Neotropical locations including the island of Trinidad in the southern Caribbean. The mealybug poses a serious threat to uninfested countries in this region as well as the mainland U.S. As part of an effort to gather much needed information on P. minor, 33 cocoa (Theobroma cacao L.) field sites on the island were surveyed in 2006 with a view to assess the occurrence and pest status of the mealybug. P. minor was identified from 20 field sites, indicating that it was well distributed across the island on this crop, which appeared to be a reliable indicator host plant. Infestation levels were generally low and populations were sparsely distributed across the field sites categorized into three habitat types. The following year, nine field sites were surveyed for natural enemies of P. minor using laboratory-infested potatoes in sentinel traps. Species from four insect orders and six families were collected and identified. The major predators belonged to the families Cecidomyiidae and Coccinellidae. Two primary parasitoids, Leptomastix dactylopii Howard (Encyrtidae) and Coccidoxenoides perminutus (Girault) (=Pauridia peregrina Timberlake, =Coccidoxenoides peregrinus (Timberlake)) (Encyrtidae), were reared from different mealybug stages, along with several hyperparasitoids. The primary parasitoids were probably introduced fortuitously. These diverse natural enemies were recovered throughout the sampling period from the different habitat types. The identification of key natural enemies associated with P. minor has important implications for the implementation of biological control in newly infested areas.     

Intra‐ and interspecific interactions between Nephus includens and Cryptolaemus montrouzieri

The introduced coccinellid Cryptolaemus montrouzieri is extensively used by biological control practitioners against mealybugs. Potential risks on native guilds of natural enemies have recently been recognized, as C. montrouzieri has managed to establish in many of the regions, it has been released. We investigated in the laboratory the direct trophic interactions between Cryptolaemus montrouzieri and Nephus includens, a predatory coccinellid native to the Mediterranean region. For both adult coccinellid species, predation rates on conspecific or heterospecific juvenile stages, with different amounts of shared prey, were recorded after 24 h. Both predators consumed eggs and larvae, but only C. montrouzieri preyed upon pupae. In general, cannibalism decreased with shared prey abundance, regardless of species. A high level of asymmetry was found on intraguild predation, in favour of C. montrouzieri. The probability of displacement threat of N. includens by C. montrouzieri in nature, in addition to possible effects of the studied trophic interactions on the outcome of biological control, is discussed.     

Comparative development and reproduction of Planococcus ficus and Planococcus citri (Hemiptera: Pseudococcidae) on grapevine under field conditions

相似文献   

Vine mealybug sex pheromone increases citrus mealybug parasitism by Anagyrus sp. near pseudococci (Girault)

The present study was aimed at elucidating the role of lavandulyl senecioate (LS), the sex pheromone of Planococcus ficus, in host selection of the parasitoid Anagyrus sp. near pseudococci. Field trials were carried out in Portugal, Italy and Israel. The effect of LS on the parasitism rate of the wasp was determined by exposing sentinel mealybugs combined with pheromone dispensers impregnated with LS, in comparison with other baits: lavandulyl isovalerate (LI); planococcyl acetate (PAc); and unbaited control traps. In addition, in order to study the host location behavior of A. sp. near pseudococci, pheromone dispensers were placed at three different distances: inside the trap, 30 or 60 cm away from the trap. The number of parasitoid females inside the traps, the number of parasitized mealybugs, and the number of days required for the first parasitoid emergence were recorded. The response of A. sp. near pseudococci females to different doses of LS (25–1350 μg) was also evaluated using sticky plate traps. The rate of mealybug parasitism by A. sp. near pseudococci was significantly increased by LS in the three parasitoid populations. PAc and LI had no significant effect on the wasp parasitism rate in most of the trials. However, the Italian population of the parasitoid responded to PAc, showing apparently a different behavioral pattern. The number of parasitoid females trapped did not significantly differ between tested doses of LS. The use of LS as an arrestant in host location by the A. sp. near pseudococci female is discussed.     

Effects of three mealybug species on the development,survivorship and reproduction of the predatory lady beetle Cryptolaemus montrouzieri Mulsant

The lady beetle Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) is an important predator of mealybugs. The development, survivorship, longevity and reproduction of C. montrouzieri feeding on three different mealybug species [Dysmicoccus neobrevipes Beardsley, Ferrisia virgata Cockerell and Planococcus minor (Maskell)] were investigated in the laboratory at 26 ± 1°C, 75-–90% RH and 14:10 (L:D) h photoperiod. Results indicated that, when feeding on different mealybugs, no significant differences were observed between developmental periods and survivorship of C. montrouzieri (from egg to adult), but differences were recorded between the sex ratios, preovipositional periods, adult longevities and reproduction of the differently treated lady beetle populations. The highest sex ratio (0.56), the longest preovipositional period (6.6 days) and adult longevity (84.8 days for females and 93.9 days for males), and the maximum fecundity (659.0 eggs/female) of C. montrouzieri were recorded when feeding on F. virgata. Moreover, C. montrouzieri had a high net reproductive rate (313.66), intrinsic rate of increase (0.0816) and finite rate of increase (1.085) when feeding on F. virgata. Results indicated that the population growth of C. montrouzieri may increase faster when feeding on F. virgata than feeding on either of the other two mealybugs.     

Biological control of citrus mealybug,Planococcus citri with an introduced parasite,Leptomastix dactylopii in India

Planococcus citri (Risso) is one of the major pests of citrus orchards in India. For the control ofP. citri, an encyrtid parasite,Leptomastix dactylopii How. was introduced from West Indies in 1983. The parasite was mass bred and inoculative releases were made in 2 selected citrus orchards where infestation of mealybug on fruits (sweet orange, seedless lime and acid lime) ranged from 38 to 65 per cent. Establishment of the parasite in the 2 release orchards resulted in complete control of the mealybug within 3 to 4 months. No insecticidal sprays were required subsequently for the control ofP. citri in the following seasons. Contribution No. 152/85 of the IIHR, Bangalore — 560089.