Cytotype Affects the Capability of the Whitefly Bemisia tabaci MED Species To Feed and Oviposit on an Unfavorable Host Plant.

The acquisition of nutritional obligate primary endosymbionts (P-symbionts) allowed phloemo-phageous insects to feed on plant sap and thus colonize novel ecological niches. P-symbionts often coexist with facultative secondary endosymbionts (S-symbionts), which may also influence their hosts' niche utilization ability. The whitefly Bemisia tabaci is a highly diversified species complex harboring, in addition to the P-symbiont "Candidatus Portiera aleyrodidarum," seven S-symbionts whose roles remain poorly understood. Here, we compare the phenotypic and metabolic responses of three B. tabaci lines differing in their S-symbiont community, reared on three different host plants, hibiscus, tobacco, or lantana, and address whether and how S-symbionts influence insect capacity to feed and produce offspring on those plants. We first show that hibiscus, tobacco, and lantana differ in their free amino acid composition. Insects' performance, as well as free amino acid profile and symbiotic load, were shown to be plant dependent, suggesting a critical role for the plant nutritional properties. Insect fecundity was significantly lower on lantana, indicating that it is the least favorable plant. Remarkably, insects reared on this plant show a specific amino acid profile and a higher symbiont density compared to the two other plants. In addition, this plant was the only one for which fecundity differences were observed between lines. Using genetically homogeneous hybrids, we demonstrate that cytotype (mitochondria and symbionts), and not genotype, is a major determinant of females' fecundity and amino acid profile on lantana. As cytotypes differ in their S-symbiont community, we propose that these symbionts may mediate their hosts' suitable plant range. IMPORTANCE Microbial symbionts are universal in eukaryotes, and it is now recognized that symbiotic associations represent major evolutionary driving forces. However, the extent to which symbionts contribute to their hosts' ecological adaptation and subsequent diversification is far from being fully elucidated. The whitefly Bemisia tabaci is a sap feeder associated with multiple coinfecting intracellular facultative symbionts. Here, we show that plant species simultaneously affect whiteflies' performance, amino acid profile, and symbiotic density, which could be partially explained by differences in plant nutritional properties. We also demonstrate that, on lantana, the least favorable plant used in our study, whiteflies' performance is determined by their cytotype. We propose that the host plant utilization in B. tabaci is influenced by its facultative symbiont community composition, possibly through its impact on the host dietary requirements. Altogether, our data provide new insights into the impact of intracellular microorganisms on their animal hosts' ecological niche range and diversification.

A new species of eriophyoid mite, Aceria tripuraensis sp. n. (Acari: Eriophyoidea), on Hibiscus macrophyllus from India.

A new species of Eriophyidae (Acari: Prostigmata: E riophyoidea) mite, Aceria tripuraensis n. sp., is described from the closed bud galls of Hibiscus macrophyllus Roxb. ex Hornem. (Malvaceae) in India. Aceria tripuraensis n. sp. is distinguished by having a prodorsal shield with distinct rounded lobes on the postero-lateral margins and two pairs of submedian lines. The tarsal solenidia with unusual transverse sculptures, are 2.5x longer than the empodia. Twenty Aceria species are now known to inhabit malvaceous plant hosts and those are listed here along with type localities and host plant details. A key to all known species of Aceria recorded from Hibiscus spp. is also provided.

TESTING SIDE-EFFECTS OF COMMON PESTICIDES ON A. SWIRSKII UNDER GREENHOUSE CIRCUMSTANCES.

If a grower uses predatory mites, and should use chemical compounds, he needs to be very careful in his choice of products. The selected products have to be efficient against the target pest and at the same time compatible with the present beneficial's. Useful tools for such product selection under greenhouse circumstances are side effects lists. These lists are freely available on the websites of producing companies of biological control agents. But not all products (e.g. newly developed ones) have been tested for side effects. Moreover the information already available in these tables is not based on field tests. For this reason, we have developed a protocol for quick screening of side effects of chemical plant protection products under field conditions. For these experiments we have chosen the predatory mite Amblyseius swirskii as test organism, because this is an often used phytoseiid mite, which is very sensitive to pesticides. Hibiscus rosa sinensis is the standard reference plant in our side effects trials because the chosen predatory mite has shown very good control of pests on this plant species. The experimental design consists of eight test objects in 4 replications. Test object 1 is a positive reference (water spray) and test object 2 a negative reference (deltamethrin spray, a product with long residual activity against beneficial organisms). The plot size is 0,68 m2 and each plot contains 32 Hibiscus plants. The greenhouse temperature is set at 20±2°C. The test strategy has the following sequence: introduction of an overdose of Amblyseius swirskii mites 14 days before spraying the pesticides > precount of predatory mites 4 days before application (4DBA) > spray application (A) for the 6 test products and for the 2 references > counting's after application (1, 2, 4, 8 en 12 weeks after application = 1 till 12WAA). The counting's of the number of predatory mites are performed on 20 Hibiscus leaves/plot under a binocular. Because of the absence of any food sources for the A. swirskii mites, it's necessary to re-introduce a high dose of predatory mites in the Hibiscus crop every 4 weeks, especially 2 weeks before the counting's 4, 8 and 12WAA; these introductions are carried out by hanging out 7 sachets with predatory mites (250 mites/sachet or 2500 mites/m2) on each test plot and after 10 days they are removed. In our first experiments the following commercial products have been tested: Pyrethro Pur (rapeseed oil + pyrethrins), Actara (thiamethoxam), Rizolex 500 SC (tolclofos-methyl), Topsin 500 SC (thiophanate-methyl), Floramite 240 SC (bifenazate), Cycocel 75 (chlorrmequat chloride), Vertimec (abamectin), Match (lufenuron), Nocturn (pyridalyl), Neemazal-T/S (azadirachtin), Tracer (spinosad), Envidor (spirodiclofen), Carex 10SC (pyridaben), Nissorun (hexythiazox) and Scelta (cyflumetofen). As expected the water treatment was safest for A. swirskii and deltamethrin killed most of the mites, even if they were re-introduced after 8 or 12 weeks. Also pyrethrins and spinosad showed very negative effects. Abamectin and bifenazate showed intermediate negative effects and should be used with caution. The other products were safe to use in combination with predatory mites. These screening tests will be repeated yearly with new and popular products of which the side effects in practice are currently uncertain.

Selection of a fungal isolate for the control of the pink hibiscus mealybug Maconellicoccus hirsutus.

BACKGROUND: Maconellicoccus hirsutus Green is a widely distributed pest of numerous crops. Although synthetic pesticides are used to control this pest, entomopathogenic fungi may provide an alternative control mechanism. Three experiments were carried out to select a fungal isolate with the potential to be used as a microbial control agent. The in vitro growth of five isolates of Beauveria bassiana sensu lato (Bals.) Vuill and Metarhizium anisopliae sensu lato (Metschn.) Sorokín, along with three isolates of Lecanicillium lecanii (Zimm.) Zare & W. Gams and Isaria fumosoroseus (Wize), was assessed at four temperatures. The in vivo sporulation of eight selected isolates was then evaluated, followed by the susceptibility of third-instar M. hirsutus to a single dose (1 × 10(8) conidia mL(-1) ) of each of these isolates. RESULTS: Growth was greatest by isolates of I. fumosoroseus and L. lecanii at 15 and 20 °C and by isolates of M. anisopliae at 25 and 30 °C. In vivo conidium production was greatest when infected with B. bassiana isolate GHA and M. anisopliae isolate Ma65. Mortality was greatest when inoculated with M. anisopliae isolates Ma65 and Ma129. CONCLUSION: Isolate Ma65 shows the best potential to be developed as a microbial control agent for M. hirsutus.

Life history of Paracoccus marginatus (Hemiptera: Pseudococcidae) on four host plant species under laboratory conditions.

Life history of the mealybug, Paracoccus marginatus Williams and Granara de Willink, on three ornamental plants [Hibiscus rosa-sinensis L., Acalypha wilkesiana (Muell.-Arg.), and Plumeria rubra L.] and one weed species (Parthenium hysterophorus L.) was studied under laboratory conditions. Mealybugs were able to develop, survive, and reproduce on all four hosts; however, there were differences in the life history parameters. Adult females that developed on acalypha and parthenium emerged approximately 1 d earlier than those that developed on hibiscus and plumeria. Adult males had a longer developmental time on plumeria than on the other hosts. Survival of first- and second-instar nymphs and cumulative adult survival were lowest on plumeria. Longevity was not affected by hosts for males and females and averaged 2.3 +/- 0.1 and 21.2 +/- 0.1 d, respectively. On plumeria, 58.9 +/- 1.7% of the adults were females, which was a higher female percentage than on the other hosts. No egg production occurred in virgin females. Prereproductive and reproductive periods of the females were not affected by hosts and averaged 6.3 +/- 0.1 and 11.2 +/- 0.1 d, respectively. Mean fecundity of 186.3 +/- 1.8 eggs on plumeria was lower than on the other three plant species. Life history parameters of P. marginatus on hibiscus, acalypha, plumeria, and parthenium show its ability to develop, survive, and reproduce on a wide variety of plant species.

Adaptation in the asexual false spider mite Brevipalpus phoenicis: evidence for frozen niche variation.

Because asexual species lack recombination, they have little opportunity to produce genetically variable offspring and cannot adapt to changes in their environment. However, a number of asexual species are very successful and appear to contradict this general view. One such species is the phytophagous mite Brevipalpus phoenicis (Geijskes), a species that is found in a wide range of environments. There are two general explanations for this pattern, the General Purpose Genotype (GPG) and Frozen Niche Variation (FNV). According to the GPG model, an asexual species consists of clones that can all survive and reproduce in all the different niches. Alternatively, the FNV model postulates that different clones are specialized to different niches. We have performed a test to distinguish between these models in B. phoenicis. Mites from three populations from three different host plant species (citrus, hibiscus and acerola) were transplanted to their own and the two alternative host plants and mite survival and egg production were measured. Additionally, the mite populations were genotyped using microsatellites. Fitness was seriously reduced when mites were transplanted to the alternative host plant species, except when the alternative host was acerola. We concluded that B. phoenicis clones are specialized to different niches and thus the FNV best describes the broad ecological niche of this species but that there is also some evidence for host plant generalization. This conclusion was strengthened by the observations that on each host plant species the native mite population performed better than the introduced ones, and that three microsatellite markers showed that the mite populations are genetically distinct.

Population structure and host-plant specialization in two Scaptodrosophila flower-breeding species.

In contrast to phytophagous insect species, little attention has been paid to the possibility of host races in the Drosophilidae, although flower-breeding species, where courtship and mating take place on the flowers, are likely candidates. Two species of Scaptodrosophila, S. hibisci and S. aclinata, are restricted to flowers of Hibiscus species (section Furcaria), and the Furcaria specialization likely predated the separation of S. hibisci and S. aclinata. In all, 20 microsatellite loci were analysed in nine populations of S. hibisci and five of S. aclinata. For two pairs of S. hibisci populations in close proximity, but breeding on different Hibiscus species, differentiation between the populations of each of these pairs was similar to that between the populations that were from the same Hibiscus species, but geographically distant, suggesting the early stages of host-race formation. Genetic variability was significantly less in S. aclinata than in S. hibisci, suggesting greater drift effects in the former. However, of 253 alleles detected, 82 were present in both species, 160 in S. hibisci only and 11 in S. aclinata only, indicating that S. aclinata was derived from S. hibisci, following a strong bottleneck at the time of separation--possibly 40,000 years BP. Analyses and interpretation of Hardy-Weinberg equilibrium and F statistics needed to account for null alleles known to be present at eight loci in S. hibisci, and possibly present at other loci. The results emphasize the need for caution in studies where the presence of null alleles is inferred only from population data.