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.

Interaction between Uroplata girardi (Coleoptera: Chrysomelidae) and Ophiomyia camarae (Diptera: Agromyzidae) on a shared host Lantana camara (Verbenaceae).

Multiple releases of insect agents intended to target a single plant pest species could result in competitive interactions that in turn might affect the community structure of the phytophagous insects. Two leaf-feeding biological control agents, Uroplata girardi Pic (Coleoptera: Chrysomelidae) and Ophiomyia camarae Spencer (Dipetera: Agromyzidae), were released against the weed Lantana camara L. (Verbenaceae) in South Africa in the 1970s and 2001, respectively. Since the population explosion of O. camarae in 2005, a decline of U. girardi populations had been observed in KwaZulu-Natal (KZN) humid coast, leading to speculation that negative interaction may be operating between the agents. The study therefore was conducted to determine the competitive effect of O. camarae on U. girardi. The study showed that 76% of O. camarae larval mines were formed on uninfested (clean) compared with only 24% formed on U. girardi-infested leaves, suggesting that the fly chose to lay more eggs on clean leaves. Almost the same number of U. girardi larval mines was formed on both O. camarae-infested and clean leaves, indicating that U. girardi females in this case oviposited indiscriminately on the two types of leaves. The survival of U. girardi was 53.8% when reared on clean leaves compared with only 14.6% survival on O. camarae-infested leaves. At the end of the sampling period, densities of U. girardi was over two times higher in single-species than in combined-species treatment. Releasing both agents together did not significantly affect O. camarae densities during the sampling period. In the field, O. camarae densities increased rapidly from spring to autumn, whereas those of U. girardi remained consistently low during the same period. The bias toward oviposition on clean leaves in O. camarae enables its larvae to avoid unfavorable encounters with U. girardi larvae, thus enhancing its development and survival. The apparent inability of U. girardi to distinguish between suitable and unsuitable leaves for oviposition could compromise the fitness of this beetle, and this could explain the suppression of U. girardi populations during summer when O. camarae populations begin to increase rapidly. This study provides evidence for an asymmetric interaction between two introduced agents, and therefore highlights the importance of conducting interaction studies on agents with extensive niche overlap before their release into the environment.

Efficacy of some oils and chemical compounds on Insignorthezia insignis (Browne) (Hemiptera: Ortheziidae) infesting Lantana camara in Alexandria, Egypt.

Field and laboratory experiments were conducted in March, 2008 in El-Nouzha garden, Alexandria governorate. Pre-and post treatment inspections of the insects were examined and recorded before and after (2,4,8, and 12 weeks). Spraying was applied to evaluate the efficiency of the tested compounds, [Mineral oils (KZ oil and Star oil); IGRs (Chlorfluazuron, lufenuron and pyriproxyfen); Neem oil; emamectin benzoate and thiamethoxam]. Percentages of reduction were calculated. The ensign scale insects Insignorthezia insignis (Browne) were collected from treated Lantana camara shrubs to investigate the effect of the tested chemicals on Aspartate transferase (AST), Alanine transferase (ALT) and Alkaline-phosphatase (ALPK) of the insect enzymes activities. From the obtained results, it could be concluded that the tested materials gave good results for controlling both adult and immature stages of the ensign scale insect Insignorthezia insignis (Browne) that infested Lantana camara shrubs, through affecting enzymes activities of the assigned insect pest.

Influence of temperature, photoperiod and humidity on oviposition and egg hatch of the root-feeding flea beetle Longitarsus bethae (Chrysomelidae: Alticinae), a natural enemy of the weed Lantana camara (Verbenaceae).

The root-feeding flea beetle Longitarsus bethae Savini & Escalona, was introduced into South Africa as a candidate biological control agent for the noxious and invasive weed, Lantana camara L. As part of the study to predict the beetles' survival in its new range, the influence of climatic conditions on its egg development and reproductive performance were investigated in the laboratory. The threshold temperature (T degrees) and degree-days (DD) required for egg hatch were determined after exposing the eggs to various constant temperatures (12, 17, 22, 27 and 32 degrees C) in separate growth chambers. The DD required for egg hatch was 178.6, and the temperature threshold required for egg hatch was 11.3 degrees C. Survival of eggs varied from 27 to 56% at 32 and 17 degrees C, respectively, and was optimum between 17 and 25 degrees C. Oviposition was examined under high and low relative humidity (RH) regimes while egg hatch was determined at six RH levels, each maintained in a separate controlled growth chamber set at a constant temperature (25 degrees C). Whilst RH had no influence on oviposition, eggs were highly susceptible to aridity, and continuous exposure to relative humidity below 63% for more than three days was wholly lethal at 25 degrees C. Optimum egg hatch occurred at RH between 85 and 95% for up to 12 days. The effect of day length on oviposition and subsequent egg hatch was investigated under two photoperiod regimes. Neither oviposition nor subsequent egg hatch was influenced by photoperiod. The knowledge obtained will be useful for mass rearing as well as field release programmes for L. bethae.

[Roles of olfaction and vision in orientation behavior of adult Campylomma chinensis Schuh (Hemiptera: Miridae) toward Lantana plants (Verbanaceae)].

Investigations were carried out on the orientation behavior of adult Campylomma chinensis Schuh (Hemiptera: Miridae) toward plant hosts Lantana camara, L. caniara cv. 'Flava', and L. montevidensis (Spreng. ) Briq. (Verbanaceae). Surveys on three Lantana plants showed that the distribution of C. chinensis in inflorescences was not related to floral color (partial correlation coefficient was 0.240, P = 0. 147, n = 40), but to the number of Thrips hawiiensis Morgan (partial correlation coefficient was 0.512, P < 0.0001, n = 40) and the flowers per inflorescence (partial correlation coefficient was 0.451, P < 0.0001, n = 40). In a colour preference experiment, no adult C. chinensis attracted to six different colour plates in longan field. The testing results of four-armed olfactometer indicated that adult C. chinensis had a significantly higher preference for L. camara. It was concluded that olfactory stimuli played an important role in searching for plant hosts of C. chinensis. Solid phase microextraction (SPME) and GC-MS were employed to analyze the volatiles compounds of Lantana, and seven same chemical constituents were detected from the volatiles of three Lantana plants inflorescence.

[Selection behavior of Cuscuta japonica on their hosts].

A field investigation on the selection behavior of Cuscuta japonica on their hosts showed that among the test plant communities, the number of coiling, the time of haustorium occurring, and the rate of coiling of C. japonica on hosts followed the order of B. papyrifera, W. chinensis, I. cairica, and L. camara; but the length of the elongation of C. japonica growing tips from coiling to haustorium occurring was with the order of L. camara, I. cairica, W. chinensis, and B. papyrifera. Furthermore, the growing tips of C. japonica coiled 3 circles in left direction on all selected hosts in 12 hrs, but grew away after contacting PVC rods within 24 hrs. The host diversity of C. japonic was beneficial to the survival of both C. japonica and its hosts. The selection behavior of C. japonica on their hosts had no correlation with the total N contents of different hosts. It could be postulated that the secondary metabolites of hosts made a contribution to the selection behavior of C. japonica on their hosts.