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The mealybug Phenacoccus solenopsis Tinsley has emerged as a widespread and detrimental pest in Moroccan crops. This study investigated the interactions between this mealybug species and its parasitoids, Leptomastix epona (Walker), Anagyrus dactylopii (Howard) and A. aligarhensis Agarwal and Alam (Hymenoptera, Encyrtidae), with a focus on field surveys and functional response dynamics. Field surveys were conducted over 3 years (2021–2023) on Portulaca oleracea (L.), Medicago sativa L. (Fabaceae), and Opuntia megacantha Salm-Dyck (Cactaceae) in Morocco. Functional response and interference experiments were conducted under laboratory conditions to understand parasitoid behaviors and their impact on mealybug populations. Percentages of infestation increased significantly from 2021 to 2023 in the field. In 2023, infestation percentages were 98.7% (P. oleracea), 56.7% (M. sativa), and 47.3% (O. megacantha). Parasitism rates by L. epona in P. solenopsis (P. oleracea) increased from 42.63% (2021) to 51.8% (2023), while they declined for A. aligarhensis from 27.73% to 20.86%, and they slightly decreased for A. dactylopii from 29.63% to 27.39%. Functional response trials indicated a type II functional response for all parasitoids, with L. epona demonstrating superior attack rates (0.92 h−1) and search efficiency (0.90). Handling time was consistent across all three parasitoids (0.04 h). For L. epona, the mutual interference constant (m) was estimated to be 2.20, while it was estimated at 2.07 for A. dactylopii, and at 1.99 for A. aligarhensis. These findings contribute to enhancing our understanding of the intricate relationships between the invasive mealybug P. solenopsis and its parasitoids, with potential implications for sustainable pest management strategies.

The sex pheromone of the azalea mealybug, Crisicoccus azaleae (Tinsley, 1898) (Hemiptera: Pseudococcidae), includes esters of a methyl-branched medium-chain fatty acid, ethyl and isopropyl (E)-7-methyl-4-nonenoate. These compounds are exceptional among mealybug pheromones, which are commonly monoterpenes. Determination of the absolute configuration is challenging, because both chromatographic and spectrometric separations of stereoisomers of fatty acids with a methyl group distant from the carboxyl group are difficult. To solve this problem, we synthesized the enantiomers via the Johnson–Claisen rearrangement to build (E)-4-alkenoic acid by using (R)- and (S)-3-methylpentanal as chiral blocks, which were readily available from the amino acids L-(+)-alloisoleucine and L-(+)-isoleucine, respectively. Each pure enantiomer, as well as the natural pheromone, was subsequently derivatized with a highly potent chiral labeling reagent used in the Ohrui–Akasaka method. Through NMR spectral comparisons of these derivatives, the absolute configuration of the natural pheromone was determined to be S. Field-trap bioassays showed that male mealybugs were attracted more to (S)-enantiomers and preferred the natural stereochemistry. Moreover, the synthetic pheromones attracted Anagyrus wasps, indicating that the azalea mealybug pheromone has kairomonal activity.

The Harrisia cactus mealybug (HCM), Hypogeococcus sp. (Hemiptera: Pseudococcidae), is devastating native cacti in Puerto Rico and threatens cacti throughout the Caribbean, Mexico, Central and North America. In South America, its native area, various natural enemies keep HCM under control. Two South American parasitoids, Anagyrus cachamai Triapitsyn, Logarzo & Aguirre and A. lapachosus Triapitsyn, Aguirre & Logarzo (Hymenoptera: Encyrtidae), were selected as potential biological control agents. Rearing protocol to conduct mass production, specificity studies and several aspects of the biology of these species were studied under laboratory conditions in Argentina. Anagyrus cachamai and A. lapachosus successfully attacked early instars of Hypogeococcus sp., have a balanced sex ratio, exhibited a development time synchronized with that of the host, and presented differences in their reproductive biology and development time. All these characteristics make these parasitoids promising candidates for introduction as biological control agents against the HCM pest in Puerto Rico.

Planococcus ficus (Signoret) and Pseudococcus comstocki (Kuwana) (Hemiptera: Pseudococcidae) are economically important pests occurring in vineyards, causing severe economic losses for growers and compromising bunch production. The partial effectiveness of insecticides used in controlling mealybug infestations as well as their high impact on the environment and on human health have led to the research of alternative and sustainable control methods, including biological control. Several natural enemies are reported to be effective against mealybugs, but their activity may be hindered by tending ants. These social insects are known to exhibit a mutualistic relationship with mealybugs, resulting in extremely aggressive behavior against beneficial insects. Consequently, this study explored a method to mitigate ant attendance by means of sugar dispensers in order to improve ecosystem services, as well as decrease mealybug infestation in vineyards. Field trials were carried out in four commercial vineyards of Northern Italy infested by mealybugs, in which Anagyrus vladimiri Triapitsyn (Hymenoptera: Encyrtidae) and Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) were released as biological control agents. Our results showed that sugar dispensers reduced ant activity and mealybug infestation, leading to a significant enhancement of ecosystem services. The technique showed a great potential in boosting biological control against mealybugs in field conditions, though the field application seemed to be labour intensive and needs to be replicated for a multi-year evaluation.

Anagyrus dactylopii (Howard) (Hymenoptera: Encyrtidae) is a solitary koinobiont endoparasitoid of grapevine mealybugs and has been reported to parasitize 70% of mealybug populations naturally. In the present study, we have isolated and identified by employing a 16S rRNA technique, a total of ten cultivable bacteria from the honeydew of two species of grapevine mealybugs, Maconellicoccus hirsutus and Nipaecoccus viridis . In the honeydew of M. hirsutus, seven bacteria were found, which included Micrococcus luteus , Kocuria rosea , Bacillus aquimaris , Exiguobacterium aquaticum , Staphylococcus pasteuri , Bacillus oceanisediminis and Bacillus flexus . From the honeydew of N. viridis , three bacteria, viz. Bacillus firmus , Microbacterium testaceum and Pesudomonas oryzihabitans, could be recovered. Further, we have collected the headspace from 72 h active cultures of these honeydew-associated bacteria by sorption over adsorbent trap made up of 0.2 g porapak using dynamic headspace sampling technique with pull and push system and tested the behavioral responses of mated females of A. dactylopii to these volatiles in a Y-tube olfactometer. The mated females positively responded to volatiles from five bacteria, which included only two bacteria associated with the honeydew of M. hirsutus, i.e., K. rosea , and S. pasteuri and all the three bacteria from honeydew of N. viridis . This indicates an ability of A . dactylopii to exploit cues associated with the mealybug honeydew for host location. The GC–MS analysis of bacterial headspace revealed six volatile organic compounds (VOCs), viz. propanoic acid, 2-methyl-2,2-dimethyl-1-(2-hydroxy-1-methylethyl) propyl ester; tetradecane; dodecane; 10-heptadecen-8-ynoic acid, methyl ester; 10,13-octadecadiynoic acid, methyl ester and limonen-6-ol, pivalate. Interestingly, limonen-6-ol, pivalate has been found as a common constituent of volatiles from all the three bacteria that were isolated from honeydew of N. viridis . The possible exploitation of bacterial VOCs in enhancing populations of A. dactylopii and promoting conservation biological control of mealybugs in grape vineyards is discussed.

Lateralization is a fundamental principle of the brain organization widespread among vertebrates but rather unknown in invertebrates. Evidences of lateralized courtship and mating behavioral traits in parasitic wasps are extremely rare. Here, courtship and mating sequences and the presence of mating lateralization in Anagyrus sp. near pseudococci, one of the most effective biological control agents of mealybugs, were investigated. Courtship and mating behavior in A. sp. near pseudococci consisted in the male chasing of the female, pre-copula, copula, and post-copula phases. Males mating success was not related to the duration of chasing and pre-copula. High-speed videos showed population-level lateralization in A. sp. near pseudococci during courtship. Most the wasps used the right antenna to start antennal tapping and this led to a higher mating success, although lateralization had no impact on the frequency of the antennal tapping. Both females and males displayed this behavior. Higher mating success was detected when females displayed antennal tapping during sexual interaction, though male tapping was performed with a slightly higher frequency. To the best of our knowledge, this report on behavioral asymmetries of mating traits in A. sp. near pseudococci represents a quite rare evidence of lateralized behavior in parasitic wasps of economic importance. Our findings add basic knowledge on the behavioral ecology of this biocontrol agent with potential implications on the optimization of mass-rearing procedures aimed at using this parasitoid in Integrated Pest Management.

Anagyrus lopezi is a specialist parasitoid was introduced to Indonesia in 2014 to control cassava mealybug, Phenacoccus manihoti. Plesiochrysa ramburi and Cryptolaemus montrouzieri are generalist predator insects associated with the mealybug. Intraguild predation is a crucial competition in an insect community. The study objective was to investigate interference of both predators on healthy mealybug (unparasitized) or parasitized mealybug by A. lopezi (mealybug which containing parasitoid larvae 1-, 3-, 8-, and 14-day old). Experiments were carried out in a non-choice test (served only one unparasitized or parasitized mealybug of a specific parasitoid age) and choice test (unparasitized and parasitized mealybug of a specific parasitoid age together) in laboratory under controlled environmental conditions. Both of predators species able to fed on both unparasitized and parasitized mealybugs of three different age (1-, 3-, and 8- day-old), but both predators discriminated against mealybug were parasitized 14-day old (hardened mummies). Interaction between parasitoid of A. lopezi and both predators showed antagonistic interaction type. We recommended A. lopezi should be released in field at the beginning of the time when the population of the mealybug is still low and could be continued with the predators release when the mealybug population is high.

We investigated the lower thermal limits of Anagyrus vladimiri Triapitsyn (Hymenoptera: Encyrtidae), a natural enemy of mealybugs. Parasitoids were cooled to measure supercooling points and the lower lethal temperature LLT 50 . To investigate survival after long-term cold exposure, parasitoid adults and eggs, larvae, and pupae within their host mummy were gradually acclimated. Adults were then exposed for three days to 7 °C, 5 °C, 3 °C, and 1 °C, and immatures for varying durations to 5, 1, and − 4 °C. Parasitoids were investigated for survival and reproduction. To assess the impact of fluctuating temperature, parasitoid pupae were subjected to daily warming to 10 °C from baseline temperatures of 5 °C, 1 °C, and − 4 °C during four-day-cold exposure. Finally, eggs, pupae and adults were exposed to winter conditions in Switzerland in a semi-field setup. The LLT 50 was − 17.24 °C for adults and 0.94 °C for pupae. Both values were above the supercooling points. No adult survived three days at 3 °C and lower. Likewise, no emergence occurred from eggs or larvae exposed for four days and longer to 1 °C or seven days to 5 °C. Pupae were cold-hardier surviving seven days at 5 °C and three days at 1 °C. Parasitoids surviving cold exposure were still able to reproduce. Daily warming decreased emergence of cold exposed pupae at a baseline temperature of 1 °C but not at 5 °C and − 4 °C. No eggs, pupae and adults survived winter conditions in the semi-field experiment. We thus consider A. vladimiri a chill-susceptible species with very limited cold-tolerance of the investigated population and low chances of survival during winter in Northern Switzerland.

1. Vine mealybug Planococcus ficus is an invasive pest of vineyards in many areas of the world. In California, USA, it infests all plant subunits and has a spatial refuge from natural enemies under the bark and on roots. A temporal refuge is created when ants tending the mealybug reduce the efficacy of natural enemies. 2. Biological control of vine mealybug is only partially successful and varies among California grape-growing regions. To improve control and help determine appropriate natural enemies for importation, the effects of weather on mealybug regulation by two parasitoids, Anagyrus pseudococci and Leptomastidea abnormis, and a coccinellid predator, Cryptolaemus montrouzieri, were examined across the ecological regions of California. 3. Weather-driven, physiologically based age-mass structured demographic models of the mealybug and its natural enemies were parameterized using laboratory data and field observations. Temperature was used to define the thermal limits and development rates of each species, and resource supply/demand ratios were used to scale daily per capita growth, fecundity and survivorship rates from maximal values at optimal conditions. 4. The population dynamics of the mealybug and its natural enemies were simulated at 108 locations in California over a 10-year period using observed weather. The simulation data were mapped using a geographical information system (GIS) and analysed using linear multiple regression and marginal analysis. 5. The models predictions indicated that: (i) the parasitoid A. pseudococci has a larger impact on vine mealybug than either L. abnormis or C. montrouzieri; (ii) mealybug densities will be lowest in the hot desert regions of southern California and highest in the cooler areas of northern California; (iii) mealybug density increases with season length and the size of the combined spatial-temporal refuge; (iv) biological control of mealybug could be achieved by reducing the size of the spatial-temporal refuge. 6. Synthesis and applications. Models, no matter how detailed, will always be incomplete; despite this, the complexity of tri-trophic systems can be modelled and the effects of biotic factors and of weather separated. The predictions of our model coincided well with field observations on vine mealybug, and clearly showed why the biological control will require additional species of natural enemies and/or why the size of the spatial and temporal refuges must be reduced.

Vineyard mealybugs (Hemiptera: Pseudococcidae) are economic pests in vineyards, demanding integrated control strategies. Several ant species can facilitate mealybug infestation by protecting them from natural enemies in a mutualistic relationship known as trophobiosis. In the frame of an ant management system, the provision of sugary liquid has proved worldwide to improve mealybug control. In the present study, a field trial was carried out within an important vineyard cultivation area of northern Italy with the aim of testing a lower density (80/ha) of sugar dispenser to facilitate the practicality of this method. The sugar dispensers tested, along with predators and parasitoid release, were effective in reducing mealybug infestations by 22% and resulted in a double increase in larval density of the predator Cryptolaemus mountrouzieri Mulsant. Mealybug parasitism was in general high, but it was not improved by sugar dispensers at this density. Our field validation confirms the importance of ants in mealybug infestation dynamics, and the benefits of ant management in the context of integrated strategies against mealybugs.