Impact of the Biological Control Agent Gyranusoidea tebygi Noyes (Hymenoptera: Encyrtidae) on the Mango Mealybug, Rastrococcus invadens Williams (Homoptera: Pseudococcidae), in Benin

The distribution of Rastrococcus invadens among different host plants and the impact of the mealybug on mango growth were investigated on 2067 trees in three surveys across all the ecological zones of Benin. The first survey started in 1989, less than 1 year after the first release of the exotic parasitoid Gyranusoidea tebygi. Within 3 years, G. tebygi had colonized the entire area of infestation, and was found on practically all infested mango trees as well as other infested host plants. By 1991, the incidence of R. invadens on the secondary host plants had declined significantly. The percentage of infested mango trees declined from 31.0% in 1989 to 17.5% in 1991, highest populations being found in the coastal savanna. During the same period, the mean percentage of infested mango trees having indigenous predators declined from 42.3 to 20.9%. Average mealybug densities declined steadily from 9.7 females/48 leaves in 1989, with 3.2% of all mango trees having densities above 100 mealybugs, to 6.4 females/48 leaves in 1991, with 1.3% of all trees having densities above 100 mealybugs. In multiple regression analyses, based on 23 meteorological, agronomic and plant variables, the duration of the parasitoid's presence proved to be a major factor. It influenced mealybug population densities and sooty mould incidence, which, in turn, affected the production of new leaves. In all analyses, the impact of rainfall, for example, on the sooty mould or the mealybug was less important than the effect of G. tebygi. The present study demonstrates for the first time on a large scale the impact of G. tebygi on R. invadens and, indirectly, on its main host plant, mango.     

Population Dynamics and Life Tables of the Mango Mealybug, Rastrococcus invadens Williams, and its Introduced Natural Enemy Gyranusoidea tebygi Noyes in Benin

Life table data for Rastrococcus invadens and its introduced natural enemy Gyranusoidea tebygi were obtained in the field and in the laboratory. The mealybug population's potential rate of increase ranged from 0.066/day to 0.078/day. The potential for increase of the parasitoid was double that of its host. Seasonal fluctuations in abundance of R. invadens were followed from 1988 to 1992 on mango trees in southern Benin. The population density of R. invadens decreased during the rainy seasons and peaked during the dry seasons. Mealybug field sex ratios were extremely variable, and the impact of such variability on the mealybug's potential rate of increase was analyzed. The populations of the exotic encyrtid G. tebygi, introduced into Benin in 1988 for control of the pest, were synchronized with the host populations. The spatial patterns of parasitism distribution in relation to the host population density were either independent or directly density-dependent, both at the tree level and for larger zones. However, reducing the scale of analysis resulted in different types of relationships. The impact of predators was a minor factor in the population dynamics of the mealybug. Four of the six species of hyper-parasitoids attacking mealybugs parasitized by G. tebygi developed high populations. In the two orchards studied, mealybug populations eventually collapsed and disappeared. This fact is discussed as being an indication that the biological control of the mango mealybug by G. tebygi was achieved by non-equilibrium local dynamics, and should be evaluated in a meta-population perspective.     

Competition between two primary parasitoids,Gyranusoidea tebygi Noyes and Anagyrus mangicola Noyes,attacking the mealybug Rastrococcus invadens Williams and the influence of a hyperparasitoid Chartocerus hyalipennis Hayat

Two primary parasitoids of the mealybug Rastrococcus invadens Williams, (Hemiptera: Pseudococcidae), Gyranusoidea tebygi Noyes and Anagyrus mangicola Noyes (Hymenoptera: Encyrtidae), were studied. Both primary parasitoids were capable of eliminating the mealybug host but on occasions the parasitoids went extinct before the mealybugs. Three of four parasitoids known to attack G. tebygi also attacked A. mangicola. The latter species was more heavily parasitized than the former, especially by the gregarious species Chartocerus hyalipennis Hayat. In competition experiments the presence of hyperparasitoids slightly slowed the speed of extinction of either the mealybug or the primary parasitoid. A. mangicola was heavily parasitized by C. hyalipennis and the primary went extinct while many suitable mealybug hosts were still available. There were two situations where the primary parasitoids were in direct competition; in the first G. tebygi was more successful than A. mangicola while the reverse was true for the second. It is likely that the superiority of either parasitoid would depend on particular conditions but the introduction of A. mangicola is unlikely to lessen the control being exerted in West Africa by G. tebygi.     

Establishment and spread of Gyranusoidea tebygi noyes and Anagyrus mangicola noyes (hymenoptera: encyrtidae), two biological control agents released against the mango mealybug Rastrococcus invadens williams (homoptera: pseudococcidae) in Africa

Two specific endophagous parasitoids Gyranusoidea tebygi and Anagyrus mangicola, of Indian origin, were mass‐reared at the International Institute of Tropical Agriculture in Cotonou and released against the mango mealybug Rastrococcus invadens, in collaboration with national biological control programmes. G. tebygi was released in the following countries: Benin, Gabon, Ghana, Nigeria, Sierra Leone and Zaire. In Togo, it had been released earlier and studied during another project. This parasitoid is now established in all areas infested by the mango mealybug. In addition, it established itself without previous release in Congo and Côte d'Ivoire. A. mangicola has been released in Benin, Gabon and Sierra Leone since 1991, and by mid‐1993 was recovered from a few sites. It seems locally established in southern Benin.     

Host Stage Selection and Sex Allocation by Gyranusoidea tebygi (Hymenoptera: Encyrtidae), a Parasitoid of the Mango Mealybug, Rastrococcus invadens (Homoptera: Pseudococcidae)

Host stage selection and sex allocation by Gyranusoidea tebygi Noyes (Hym,, Encyrtidae) were studied in choice and no-choice experiments in the laboratory. The parasitoid reproduced on first, second, and third instars of the mango mealybug, Rastrococcus invadens Williams (Hem., Pseudococcidae), and it avoided hosts that were already parasitized. Host feeding was occasionally observed. Sex ratios of the offspring produced by individual wasps were highly biased in favor of females, whereas the sex ratio of groups of wasps foraging under crowded conditions varied from male biased in smaller hosts to female biased in larger hosts. Females had longer developmental times than males, developed faster in larger mealybugs than in smaller ones, and were always larger than males emerging from the same host instar. Their size increased with the instar of the host at oviposition. About 90% of all ovipositions in second and third instar nymphs resulted from an attack with multiple stings, starting with a sting in the head of the host for the most part. The function of these head stings is either to assess quality of the host or to subdue hosts prior to oviposition. Encounter rates, number of attacks, and number of stings during one attack increased, while ovipositions decreased with host instar. Time investment per oviposition and time spent preening increased with increasing host age because older hosts defended themselves more vigorously than younger ones. Thus, while fitness of the parasitoid increased with host size, fitness returns per time decreased. The implications of this host selection behavior for the biological control of the mango mealybug are discussed.     

Interactions between the Parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera: Encyrtidae) and its Mealybug Hosts Tridiscus sporoboli (Cockerell) and Trionymus sp. (Homoptera: Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffalograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhopus nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug–parasitoid interactions through choice and no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs adult female, third and fourth instars, first and second instars, and eggs. Choice studies indicated that rate of parasitism increased with host size. The mean rates of parasitism on mealybugs in the choice studies were 100% for adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating mealybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all post-egg mealybug age classes, but first and second instars were less often parasitized than older mealybugs.     

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.     

红火蚁与扶桑绵粉蚧互惠关系对松粉蚧抑虱跳小蜂和美棘蓟马的影响

蚂蚁与蜜源昆虫互作是物种间重要的关系之一,发挥着重要的生态功能。红火蚁Solenopsis invicta Buren是重要的入侵害虫,对生物多样性的影响已被熟知,但它与蜜源昆虫互作的生态学效应却不被充分理解。本研究评价了红火蚁与扶桑绵粉蚧Phenacoccus solenopsis Tinsley这两种入侵害虫之间的互作对寄生性天敌和粉蚧竞争性昆虫的影响。研究发现红火蚁的照看显著减少了寄主植物上粉蚧重要寄生蜂松粉蚧抑虱跳小蜂Aenasius bambawalei Hayat的种群数量,提高了寄主上粉蚧的存活率,有利于寄主上粉蚧种群的扩增和繁殖。同时红火蚁的存在也显著降低扶桑寄主上粉蚧竞争性昆虫美棘蓟马Echinothrips americanus Morgan成虫和幼虫的数量,抑制了美棘蓟马种群的竞争力,使得粉蚧可以占有更多的寄主植物,为粉蚧种群的繁殖提供了更好的条件。可见,红火蚁与扶桑绵粉蚧的互惠关系的生态效应可能是通过它们与多物种互作综合形成的结果。     

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.     

Immune response of the hibiscus mealybug, Maconellicoccus hirsutus Green (Homoptera: Pseudococcidae), to oviposition of the parasitoid Anagyrus kamali Moursi (Hymenoptera: Encyrtidae)

Anagyrus kamali Moursi has been recently introduced into the Caribbean as a biological agent against the hibiscus mealybug, Maconellicoccus hirsutus Green. This host has a cellular defense reaction that involves encapsulation and melanization of the endoparasitoid egg. The impact of this immune response on the parasitoid progeny was assessed, as well as the response of the parasitoid countermeasures to overcome it. Under laboratory conditions, significant differences in the immune response were found for different developmental stages of M. hirsutus. The intensity of the immune response varied between second instar, third instar and adult mealybugs. After 30 h, the level of encapsulation was the highest for eggs oviposited in adults: 58% of eggs were encapsulated, followed by third (32%) and second (4%) instars. Three days after oviposition 23, 44 and 86% of the parasitoid eggs oviposited, respectively, in adult, third and second instars were not encapsulated. The unencapsulated parasitoid eggs could hatch and continue their development. Adult mealybugs required 30 h to encapsulate 50% of the eggs, whereas in second and third instars, 50% level encapsulation was never reached. Superparasitism had a saturating effect on the immune system; reduced levels of encapsulation occurred when more than 10 eggs were oviposited in a single mealybug. Wasp larvae were never encapsulated by M. hirsutus.     

Influence of host plant on the mango mealybug,Rastrococcus invadens

Life history traits of the mango mealybug,Rastrococcus invadens Williams, were compared between two neighboring mango trees (Mangifera indica L.), one of which was heavily infested and the other slightly infested. On the infested tree, mealybug survival was high because of good feeding conditions and low escape. The pre-reproductive period of mealybugs on the heavily infested tree was shorter and total offspring production higher than that of mealybugs on the uninfested tree. This significantly affected the intrinsic rate of natural increase and explained the observed differences in population densities among the trees. The results obtained from an additional experiment using juvenile clones from the same two mango varieties, in which environmental factors were uniform, demonstrated the importance of plant genotype on mealybug size and survival.     

Survey of the natural enemies of Dysmicoccus mealybugs on pineapple in Hawaii

Surveys for mealybugs, associated natural enemies and ants were conducted in abandoned pineapple fields on the Hawaiian islands of Oahu and Maui from July 1992 to November 1993. Whole plant samples were taken, and mealybugs and ants found were identified. Mealybug-infested plant parts were isolated and held until natural enemies emerged from parasitized host material. At sample sites where only Dysmicoccus brevipes was present, its densities ranged from a mean of 23 to 157 mealybugs per plant, while in areas with mixed populations of this mealybug and Dysmicoccus neobrevipes Beardsley, densities ranged from a mean of 23 to 118 mealybugs per plant. Ants were present at all sample sites and on all dates. Pheidole megacephala (F.) was the most common ant species found. Anagyrus ananatis Gahan was the most common parasitoid reared. However, it attacked only D. brevipes, the dominant mealybug in the pineapple fields surveyed. Percent parasitization of D. brevipes by A. ananatis in the presence of ants ranged from 0.3 to 9.9%. Percent parasitization of D. brevipes and D. neobrevipes per plant by Euryrhopalus propinquus Kerrich ranged from 0.05 to 2.2%. Mean densities of the predators Lobodiplosis pseudococci (Felt), Nephus bilucernarius Mulsant and Sticholotis ruficeps Weise ranged from 0.05 to 5.75, 0.1 to 1.8, and 0.05 to 0.2 individuals per plant, respectively.     

Host stage preference and parasitism behaviour of Aenasius bambawalei an encyrtid parasitoid of Phenacoccus solenopsis

In Pakistan, the cotton mealybug, Phenacoccus solenopsis Tinsley (Sternorrhyncha (Homoptera): Pseudococcidae), is a serious pest of many cultivated plants. A parasitoid, Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae), is associated with P. solenopsis. In order to mass rear A. bambawalei for a biological control programme, it is important to investigate the parasitoid’s host stage preference and its parasitism behaviour for P. solenopsis in order to optimise production. The present study showed that under both choice and no-choice conditions, the parasitoid preferred third instar and pre-reproductive host stage mealybugs for parasitism. Parasitoid larva developing inside the host exhibited a greater longevity, shorter developmental period and longer body size in these preferred host stages. Our study also confirmed that A. bambawalei showed no attraction to male mealybugs and no host feeding on any host stage was recorded. The ability of the parasitoid to effectively discriminate between suitable and non-suitable stages means that it is feasible to rear it on a mixed population.     

Seasonal movement and distribution of the grape mealybug (Homoptera: Pseudococcidae): developing a sample program for San Joaquin Valley vineyards

The grape mealybug, Pseudococcus maritimus (Ehrhorn), is an important pest of table grapes in California's San Joaquin Valley. The mealybug causes direct damage by infesting grape bunches, resulting in very low economic injury levels. To develop a sampling program to help growers predict damage and make control decisions, we destructively sampled six entire grapevines each month to determine mealybug abundance and within-vine distribution. These absolute counts were then used to evaluate several relative sampling methods: sticky tape barriers on canes, excised spur samples, standard-sized pieces of bark, timed counts, and nondestructive counts on spurs. At midseason we sampled additional vines to correlate mealybug numbers with economic damage at harvest. Finally, mealybug life stages and natural enemies were recorded throughout the study. Timed 5-min counts show the strongest correlation with total mealybug numbers, and a simple count of mealybugs on three spurs per vine at midseason is the best predictor of economic damage. Mealybugs completed approximately equals 2.5 generations in 1998. Comparison to data on mealybug development suggests that exceptionally long growing seasons could exacerbate infestations by allowing the completion of a third generation. No mealybugs were found on bunches before early August, when second-generation crawlers moved out of the bark. Grape bunches that touched old wood had significantly higher damage and mealybug densities. The majority of mealybugs were always found in protected locations (under the bark of the trunk, spurs or canes), indicating the need for chemical or biological controls that can penetrate these refugia.     

Host Preference and Progeny Sex Ratio in a Solitary Koinobiont Mealybug Endoparasitoid, Anagyrus Pseudococci (Girault), in Response to its Host Stage

Anagyrus pseudococci (Girault) , a koinobiont endoparasitoid , is a potential biological control agent of the citrus mealybug Planococcus citri (Risso) . This paper examines the effect of host stage of the mealybugs on the parasitoid preference , development , survival and sex ratio of the offspring . Host susceptibility and preference tests showed that the parasitoid had a significant preference for the older host instars . Percentage parasitization increased 4.8 - fold in the adult stage , compared with the second - instar host , although the parasitoid developed and emerged successfully from all stages . Mean developmental time for male parasitoids was faster than for the females . There was some evidence of delayed development of males in young hosts . Higher percentage emergence of parasitoid was observed from older mealybugs . A. pseudococci exhibited maternal adjustment of sex ratio as a function of host size with an increased proportion of females with the increasing host size . Females maximized their fitness by adjusting offspring sex ratio in response to host size without evaluating the future host quality . This information is important for mass rearing of A. pseudococci and for evaluating it in a biological control programme for P. citri.     

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.     

Host location and discrimination mediated through olfactory stimuli in two species of Encyrtidae

The role of olfactory stimuli in host detection and evaluation was studied in two encyrtid Hymenoptera. The first, Epidinocarsis lopezi De Santis, is a monophagous parasitoid of the cassava mealybug Phenacoccus manihoti Matile-Ferrero, itself feeding exclusively on cassava, Manihot esculenta Crantz. The second, Leptomastix dactylopii Howard, is a monophagous parasitoid of the Citrus mealybug, Planococcus citri Risso, but this latter is highly polyphagous. The behaviour of females of both parasitoids (attaction and locomotion) was compared in a tubular olfactometer for the odours of their respective hosts on cassava and poinsettia. Tests were made using: 1) healthy host-plant alone; 2) host-plant infested with unparasitized mealybugs; 3) unparasitized mealybugs only; 4) host-plant infested with parasitized mealybugs and 5) parasitized mealybugs only. Only E. lopezi was attracted by the odour of the host-plant alone, but both species were attracted by the odour of an infested host-plant and that of unparasitized mealybugs. The odour of parasitized mealybugs, alone or on host-plant, induced an undirected activity. The attraction of E. lopezi to the odour of the host-plant alone could be linked to the monophagous diet of its host, whereas the attraction of the two species of parasitoids to the odours of infested host-plants and unparasitized mealybugs could be due to the fact that both parasitoids are specialists. The behavioural response of both species to the odour of parasitized mealybugs revealed a new aspect in host discrimination: the identification of parasitized hosts could be partly mediated through olfactory stimuli, and not only through gustatory stimuli.     

Host stage selection of the mealybug parasitoid Anagyrus spec. nov near sinope

The mealybug parasitoid Anagyrus spec. nov near sinope (Hymenoptera: Encyrtidae) is an undescribed parasitoid of the Madeira mealybug, Phenacoccus madeirensis Green (Homoptera: Pseudococcidae). We investigated the preference of Anagyrus spec. nov near sinope for six developmental stadia (first‐ and second‐instar nymphs, third‐instar immature females, third‐ or fourth‐instar immature males, pre‐reproductive adult females, and ovipositing adult females) of P. madeirensis and the fitness consequences of the host stage selection behavior. In the no‐choice test, Anagyrus spec. nov near sinope parasitized and completed development in all host stadia except third‐instar immature males. When all host stadia were offered simultaneously, the parasitoids preferred third‐instar immature and pre‐reproductive adult females. Dissection of the stung mealybugs revealed that the clutch size (number of eggs per host) was approximately four and three in the third‐instar and pre‐reproductive females, respectively, and one egg per first‐instar nymph. Parasitoids emerged from P. madeirensis parasitized at third‐instar or pre‐reproductive adult female completed development in the shortest duration, achieved a higher progeny survival rate, larger brood and body size, and the lowest proportion of males. We showed that the continued development of mealybugs had significant influence on the fitness of the parasitoids. Although deposited as eggs in first‐ or second‐instar nymphs, parasitoids emerged from mummies that had attained third‐instar or adult development achieved similar progeny survival rate, brood size, body size, and sex ratio as those parasitoids deposited and developed in third‐instar or adult mealybugs. By delaying larval development in young mealybugs, Anagyrus spec. nov near sinope achieved higher fitness by allowing the parasitized mealybugs to grow and accumulate body size and resources. We suggest that the fitness consequence of host stage selection of a koinobiont parasitoid should be evaluated on both the time of parasitism and the time of mummification.     

Does the host plant affect the benefits from mutualisms? The invasive mealybug and ghost ant association

1. The benefits to trophobionte hemipterans are affected by the ant tending level, which is a widely accepted statement. The ant tending level is closely related to multiple factors. It is clear that the ant tending level can be affected by the temporal factor, age‐specific, the density of the hemipterans, and quantity and quality of honeydew produced by hemipterans. 2. Few studies of ant–hemipteran mutualisms have reported the patterns of host plants‐dependent effects, and whether host plants influence the ant tending level that is also unclear. As such, laboratory experiments were conducted to test whether the colony growth rate of an invasive mealybug Phenacoccus solenopsis Tinsley, parasitism of Aenasius bambawalei Hayat, an dominant parasitoid of P. solenopsis, are affected by tending by ghost ants (Tapinoma melanocephalum(Fabricius)], host plants (tomato and cotton), and interactions between the two factors. The difference in the ant tending level between the host plants was also determined. 3. The results showed that mealybug colony growth and parasitism were significantly affected by ant tending and host plant separately. There were significant interactions between the independent factors on the mealybug colony growth rate and percentage parasitism. These results suggest that benefits to mealybugs are host plant‐dependent.     

Host instar susceptibility and selection and interspecific competition of three introduced parasitoids of the mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae)

Three previously introduced parasitoids (Acerophagus papayae Noyes and Schauff, Anagyrus loecki Noyes and Menezes, and Pseudleptomastix mexicana Noyes and Schauff [Hymenoptera: Encyrtidae]) of the mealybug Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) were studied for their host instar susceptibility and sex ratio, host instar selection, and interspecific competition in the laboratory. All three parasitoids were able to develop in the second instars, third-instar females, and adult females of P. marginatus. No progeny emerged from first-instar mealybugs. The proportion of female emergence was increased with increasing host size. Parasitoids selected their host instars for oviposition when they had a choice. Between second- and third-instar hosts, A. papayae and P. mexicana had significantly higher parasitism in second-instar mealybugs, whereas A. loecki had higher parasitism in the third-instar mealybugs. When competed with either one or two parasitoid species, A. papayae was significantly more successful in second-instar hosts and A. loecki was significantly more successful in third-instar mealybugs. P. mexicana was significantly less competitive when with A. papayae in both second and third instars, with A. loecki in third instars and with both A. papayae and A. loecki in second and third instars. Overall, A. papayae provided a better control of the host, when present singly or with the other two parasitoids. This information is important in evaluating the efficiency of A. papayae, A. loecki, and P. mexicana and understanding the outcome of their recovery and establishment in field studies conducted in Florida.