Insect-associated fungi from naturally mycosed vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Vine mealybug, Planococcus ficus, is a major pest of grapevine, which is present in at least 39 countries. According to American Vineyard Foundation, P. ficus is in the top ranks among major insect-pests of grapevine. It is the ‘top priority concerns’ by grape growers and a ‘threat to the sustainability of wine industry’ demanding a ‘high priority research’. In Douro vineyards, it is considered as an occasional insect-pest; however, its importance is increasing in some localities. The present study investigates the occurrences of P. ficus-associated fungi. Vine mealybugs were observed in two of the four surveyed farms. Out of the 183 collected mealybugs, 58 were dead of which 25 had symptoms of mycosis and 13 were parasitised. Subculturing cadavers and subsequent pathogenicity test yielded 22 entomopathogenic fungi (EPF) including yeasts. The yeast Meyerozyma (=Pichia) guilliermondii, and the EPF Sarocladium kiliense and Purpureocillium lilacinum were the most abundant, i.e. representing 18.18% (N?=?4), 13.64% (N?=?3) and 13.64% (N?=?3) of the isolates, respectively. Considering biological affinities, fungal families Nectriaceae and Microascaceae had the most similar count-data profiles. To our knowledge, this work reports the first isolations of EPF from vine mealybug worldwide; and Pseudocosmospora rogersonii in Europe and as EPF worldwide. The mortality rate originated by mycoses on P. ficus was significantly higher than by its parasitoids, suggesting that fungi as P. ficus biocontrol agents are relatively more important than considered before. Overall, this report provides new insights into the development of mycoinsecticides and conservation biocontrol strategies for P. ficus pest management.     

Field placement of mealybug-infested potted cassava plants for the study of parasitism of Phenacoccus herreni

During 4-day field exposure intervals, Phenacoccus herreni Cox & Williams, third-instar mealybugs on artificially infested potted cassava plants were reduced 73% from initial densities of 235.7–1100.2/infested plant to 63.7–314.2/plant due to dispersal, rain, and predation. Frequency of parasitoid attack did not differ between high and low mealybug densities. The same species of parasitoids, in approximately the same proportions, were reared from mealybugs on artificially infested potted plants as from field mealybugs (Acerophagus coccois) Smith, 88.1% and Epidinocarsis diversicornis (Howard), 11.3%. Parasitoid attack rates on artificially exposed mealybugs, when combined with a simulation model of parasitism, accurately predicted observed levels of stage-specific parasitism in the field population.

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Résumé Pendant des expositions de 4 jours dans la nature de plants en pots de M. esculenta contaminés artificiellement par des P. herreni du troisième stade, les densités de cochenilles ont été réduites de 73%: de 235.7–1100.2/par plant contaminé à 63.7–314.2/par plant, par suite des évasions, de la pluie et de la prédation. Les attaques de parasitoïdes ne changent pas suivant les densités de cochenilles. Les mêmes espèces de parasitoïdes, ont été élevées dans à peu près les mêmes proportions (Acerophagus coccois, 88.1%, et Epidinocaris diversicornis, 11.3%) à partir de cochenilles sur pots artificiellement contaminés ou de manioc de la nature. Les taux d'attaques par les parasitoïdes sur les cochenilles artificiellement exposées, associés à un modèle de simulation du parasitisme, ont permis de prévoir avec précision les niveaux de parasitisme observés pour chaque stade dans la population de la nature.

     

Report of a parasitic wasp (Hymenoptera: Encyrtidae) parasitizing cotton mealybug (Hemiptera: Pseudococcidae) in Pakistan and use of PCR for estimating parasitism levels

A parasitic wasp, Aenasius bambawalei, was studied for its biological parameters and parasitism levels in the cotton mealybug (Phenacoccus solenopsis). Biological parameters including parasitism efficiency, time to pupation, time to eclosion and adult sex ratio were studied under lab conditions. Parasitism levels in field collected mealybug were determined using PCR. Results showed an increase in parasitism over the study period, with higher parasitism levels in 2009 compared to the preceding 2 years.     

粉蚧科一新属一新种(半翅目,蚧总科)

记述粉蚧科1新属1新种,即拟锯粉蚧属Paraserrolecanium gen.nov.及其模式种箭竹拟锯粉蚧P.fargesii sp.nov.。新种模式标本采自陕西省凤县天台山一种箭竹Fargesia sp.叶鞘下茎上,保存在北京林业大学昆虫标本室。     

Biology ofCryptolaemus montrouzieri Mulsant [Coccinellidae: Coleoptera] in relation with temperature

The effect of temperature on the developmental duration ofCryptolaemus montrouzieri Mulsant was quantified by deriving a regression equation for each developmental stage as well as the total life cycle. While the duration of life stages was shorter during summer and longer during winter, the optimum constant temperature for maximal development was found to be 30°C. The adult longevity was extended when reared at 20°C than at 30°C and ambient temperature. The longevity of adults was longer when maintained on grape mealybugMaconellicoccus hirsutus (Green) than on honey and when maintained at 20°C. The fecundity of the predator was higher at 30°C than at 20°C. Eventhough the adults could survive at 10°C, the productive capacity was impaired.      

Endocrocin and Its Derivatives from the Japanese Mealybug Planococcus kraunhiae

The Japanese mealybug, Planococcus kraunhiae, is suitable as a model insect for biosynthetic studies on mealybug pigments. Four yellow pigments, including two novel ones, were isolated from the mealybug bodies and characterized as endocrocin, a dicarboxylic acid named fujikonaic acid (1), emodin 1-O-β-D-glucopyranoside and 7-hydroxyemodin 1-O-β-D-glucopyranoside (2). The enzymatic activity of emodin 1-O-glucosyltransferase was observed in the extracts of insect bodies.     

Physiological and morphological development of Anagyrus ananatis at constant temperatures

The lower developmental temperature threshold (T ₀) and the Degree Days (DD) required for the encyrtid endoparasitoid Anagyrus ananatis Gahan to develop from egg to adult on the pink pineapple mealybug (PPM), Dysmicoccus brevipes (Cockerell) (Hemiptera: Pseudococcidae), were determined. The T ₀ was estimated to be about 12.65 °C for both females and males. In contrast, females and males required about 275 and 265 DD, respectively, to complete development from egg to adult. Temperatures from 19 to 29 °C were optimal for mass rearing of A. ananatis, with the optimal temperature being around 24 °C. At this temperature, A. ananatis could complete almost two generations in the time it takes PPM to complete only one generation. Although A. ananatis is a koinobiont, the mealybug host was killed within a few (6–8) days after parasitization. The developmental stages of A. ananatis were described (e.g., appearance, size, color) and their time periods quantified when reared on PPM at 23.5 ± 0.5°C. Encyrtiform eggs were inserted through the dorsal surface of the PPM and were attached to the host via a slender stalk. This immature parasitoid remained attached to the host cuticle via the stalk until entering the prepupal stage. The host mealybug mummified during the parasitoid’s prepupal stage. First adult eclosion occurred at 24 days post-parasitization.     

The more,the merrier? Obligate symbiont density changes over time under controlled environmental conditions,yet holds no clear fitness consequences

Symbiotic bacteria are highly diverse, play an important role in ecology and evolution, and are also of applied relevance because many pest insects rely on them for their success. However, the dynamics and regulation of symbiotic bacteria within hosts is complex and still poorly understood outside of a few model systems. One of the most intriguing symbiotic relationships is the obligate, tripartite nutritional mutualism in sap‐feeding, economically‐destructive mealybugs (Hemiptera: Sternorrhyncha: Pseudococcidae), which involves γ‐proteobacteria hosted within β‐proteobacteria hosted within the mealybugs. The present study examines whether there is population variation in symbiont density (i.e. infection intensity, or titre) in the citrus mealybug Planococcus citri (Risso) and how this impacts host life‐history. Symbiont density is found to differ significantly between populations when reared under controlled environmental conditions, indicating that the density of symbiont infections is influenced by host or symbiont genotype. However, symbiont density changes in populations over multiple generations, indicating that symbiont densities are dynamic. Surprisingly, given that the symbionts are essential nutritional mutualists, the density of the symbionts does not correlate significantly with either host fecundity or development. Higher levels of symbionts have no clear benefit to hosts and therefore appear to be superfluous, at least under constant, optimized environmental conditions. Excessive symbiont density may be an evolutionary artefact from a period of inefficient vertical transmission when the balance of conflict between host and symbiont was still being established.     

Effect of Coleus Size and Variegation on Attack Rates, Searching Strategy, and Selected Life History Characteristics of Cryptolaemus montrouzieri (Coleoptera: Coccinellidae)

Twenty-four-hour attack rates and the search strategy of third instar Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) attacking 1 to 16 third instar Planococcus citri Risso (Homoptera: Pseudococcidae) were measured on green and yellow-variegated Solenostemon scutellarioides (L.) Codd (= Coleus blumei (Bentham)) (Labiatae) plants of different sizes. Selected life history characteristics of C. montrouzieri fed different amounts of P. citri as prey from third instar to adults were also examined. On average, predators attacked 1 to 4 mealybugs, depending on the number of mealybugs and plant size. There was no effect of plant color on attack rates. Attack rates were positively related to prey density, whereas the estimated area searched by predators was inversely related to prey density. Analyses suggest that leaf area was the plant characteristic that most affected attack rates. Predators fed few prey had a decrease in body weight and survival. The implications for the use of C. montrouzieri in biological control are discussed.