Ripe fruit offer readily available nutrients for many animals, including fruit fly larvae (Diptera: Tephritidae) and their associated rot-inducing bacteria. Yet, during most of their ontogeny, fruit remain chemically defended and effectively suppress herbivores and pathogens by high levels of secondary metabolites. Olive flies (Bactrocera oleae) are uniquely able to develop in unripe olives. Unlike other frugivorous tephritids, the larvae maintain bacteria confined within their midgut caeca. We examined the interaction between larvae, their associated bacteria, and fruit chemical defence, hypothesizing that bacterial contribution to larval development is contingent on the phenology of fruit defensive chemistry. We demonstrate that larvae require their natural complement of bacteria (Candidatus Erwinia dacicola: Enterobacteriaceae) in order to develop in unripe olives. Conversely, when feeding on ripe fruit, larval development proceeds independently of these bacteria. Our experiments suggest that bacteria counteract the inhibitory effect of oleuropein—the principal phenolic glycoside in unripe olives. In light of these results, we suggest that the unique symbiosis in olive flies, compared with other frugivorous tephritids, is understood by considering the relationship between the fly, bacteria and fruit chemistry. When applied in an evolutionary context, this approach may also point out the forces which shaped symbioses across the Tephritidae.

Symbiotic bacteria enable olive fly larvae to overcome host defences.

Over a period of 18 months the bacteria associated with approximately 70 adult flies of four Dacus species were isolated and identified. The flies were D. tryoni (Froggatt) and D. neohumeralis Hardy from guava (Psidium guajava L.), mulberry (Morus nigra L.) and peach [Prunus persica (L.) Batsch], D. cacuminatus (Hering) from wild tobacco (Solanum mauritianum Scop.), and D. musae (Tryon) from banana (Musa paradisiaca L.), and were collected in the field when these host plants were fruiting. All flies examined were surface-sterilized prior to aseptic dissection in which crop and mid-gut (stomach) or oesophageal bulbs were removed for culturing. Bacteria were also isolated from faeces of field-collected flies, as well as from host fruit surfaces, oviposition sites and larvae-infested tissue in host fruit. The predominant bacteria found in the alimentary tract of flies and in associated fruit specimens were members of the family Enterobacteriaceae. Klebsiella oxytoca, Erwinia herbicola and Enterobacter cloacae were the most frequently isolated species, with Serratia spp., Citrobacter jreundii, Proteus spp., Providencia rettgeri and Escherichia coli, being found less frequently. No one bacterial species was found to be consistently associated with anyone fly species. The bacterial species found most frequently in the alimentary tract were also found in large numbers on the surfaces of host fruit and in stung fruit.

/pdf/bacteria-associated-with-some-dacus-species-diptera-2bfwsvoqtf.pdf

Bacteria associated with some Dacus species (Diptera: Tephritidae) and their host fruit in Queensland

One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non-inoculated gel was provided to the flies fed on non-probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non-inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.

Development of probiotic diets for the olive fly: evaluation of their effects on fly longevity and fecundity

This study focuses on interacting with insects and their ectosymbiont (lato sensu) microorganisms for environmentally safe plant production and protection. Some cases help compare ectosymbiont microorganisms that are insect-borne, -driven, or -spread relevant to endosymbionts’ behaviour. Ectosymbiotic bacteria can interact with insects by allowing them to improve the value of their pabula. In addition, some bacteria are essential for creating ecological niches that can host the development of pests. Insect-borne plant pathogens include bacteria, viruses, and fungi. These pathogens interact with their vectors to enhance reciprocal fitness. Knowing vector-phoront interaction could considerably increase chances for outbreak management, notably when sustained by quarantine vector ectosymbiont pathogens, such as the actual Xylella fastidiosa Mediterranean invasion episode. Insect pathogenic viruses have a close evolutionary relationship with their hosts, also being highly specific and obligate parasites. Sixteen virus families have been reported to infect insects and may be involved in the biological control of specific pests, including some economic weevils. Insects and fungi are among the most widespread organisms in nature and interact with each other, establishing symbiotic relationships ranging from mutualism to antagonism. The associations can influence the extent to which interacting organisms can exert their effects on plants and the proper management practices. Sustainable pest management also relies on entomopathogenic fungi; research on these species starts from their isolation from insect carcasses, followed by identification using conventional light or electron microscopy techniques. Thanks to the development of omics sciences, it is possible to identify entomopathogenic fungi with evolutionary histories that are less-shared with the target insect and can be proposed as pest antagonists. Many interesting omics can help detect the presence of entomopathogens in different natural matrices, such as soil or plants. The same techniques will help localize ectosymbionts, localization of recesses, or specialized morphological adaptation, greatly supporting the robust interpretation of the symbiont role. The manipulation and modulation of ectosymbionts could be a more promising way to counteract pests and borne pathogens, mitigating the impact of formulates and reducing food insecurity due to the lesser impact of direct damage and diseases. The promise has a preventive intent for more manageable and broader implications for pests, comparing what we can obtain using simpler, less-specific techniques and a less comprehensive approach to Integrated Pest Management (IPM).

/pdf/ectomosphere-insects-and-microorganism-interactions-1jr0g0u3.pdf

“Ectomosphere”: Insects and Microorganism Interactions

Inhibition of growth of Dacus oleae larvae in untreated green olive fruits occurred in a high percentage when the parents were treated, in the laboratory, with 1% streptomycin sulphate plus a spreader-wetter in the following ways: – (a) brief immersion of the olives in which the parent insects grew as larvae; (b) brief immersion as fully grown larvae; (c) spraying of adults; (d) allowing parent females to oviposit for a few hours in treated olives, prior to ovipositing in untreated ones. In the last case, the degree of inhibition of progeny growth was related to the time between the maternal treatment and the birth of the progeny.



RESUME

INHIBITION DU DEVELOPPEMENT LARVAIRE DE DACUS OLEAE (DIPTERA: TEPHRITIDAE) PAR LA STREPTOMYCINE II. EFFET DU TRAITEMENT DES PARENTS



Le developpement larvaire de Dacus oleae dans des olives vertes non-traitees est inhibe a un pourcentage eleve quant les parents ont ete traites, au laboratoire, avec 1% de sulfate de streptomycine associe a un produit dispersant-mouillant, selon les modalites suivantes: (a) immersion breve des olives dans lesquelles les parents se sont developpes comme larves; (b) immersion breve des larves a developpement complet; (c) pulverisation des adultes; (d) oviposition des femelles pour quelques heures dans des olives traitees, avant de pondre dans des olives non-traitees. Dans ce dernier cas, l'inhibition de la descendance fut influencee par le temps separant le traitement de la mere et la naissance de la descendance.

Inhibition of larval growth of dacus oleae (diptera: tephritidae) by streptomycin ii. effect of treating the parents

The growth of larvae of the olive fruit fly, Dacus oleae (Gmelin), in picked green olives could be inhibited if the olives were dipped briefly into 1% and 5% streptomycin sulphate solutions in tap water plus a spreader-wetter (Tzanakakis & Stavrinides, 1973). The percent of fruits in which larval growth was inhibited varied with the time between treatment and oviposition. A small preliminary experiment of treating the fruit on the trees is reported here. Sixteen fruit-bearing twigs, (A-P), accessible from the ground, were selected on the periphery of four neighbouring olive trees in a grove of Halkidiki (N. Greece). The exposure of each twig is shown in Fig. 1. Two trees were of the variety Megaritiki and two of Koutsourelia. Inhibition of larval growth by treating fruit with streptomycin in the laboratory had been proved with olives of both these varieties (Tzanakakis & Stavrinides, 1973). For each tree, the following procedure was followed: In mid-September, four twigs were selected, each bearing 31-169 fruits. After removing fly-infested fruits, the twigs were covered with a dense muslin of synthetic material. On 4.X.1973 two twigs were uncovered and the fruit was sprayed to run-off, with a small low pressure hand sprayer. Surrounding foliage was also by necessity sprayed but not necessarily to run-off. One twig received 1% streptomycin sulphate solution in tap water plus 0.05% Agral 90 (a spreader-wetter), and the other (control) only water plus Agral 90. After allowing approximately 15-30 min for the spray to dry, the twigs were caged again to protect them from infestation by olive fruit flies in the grove. A week later, female flies of a laying age were introduced to each caged twig. Seven flies on the Megaritiki

A preliminary field experiment on the inhibition of larval growth of Dacus oleae by streptomycin.

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Inhibition of larval growth of dacus oleae (diptera: tephritidae) by streptomycin ii. effect of treating the parents

A preliminary field experiment on the inhibition of larval growth of Dacus oleae by streptomycin.