Interactions between the Parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera: Encyrtidae) and its Mealybug Hosts Tridiscus sporoboli (Cockerell) and Trionymus sp. (Homoptera: Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffalograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhopus nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug–parasitoid interactions through choice and no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs adult female, third and fourth instars, first and second instars, and eggs. Choice studies indicated that rate of parasitism increased with host size. The mean rates of parasitism on mealybugs in the choice studies were 100% for adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating mealybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all post-egg mealybug age classes, but first and second instars were less often parasitized than older mealybugs.     

Molecular detection of Gluconacetobacter sacchari associated with the pink sugarcane mealybug Saccharicoccus sacchari (Cockerell) and the sugarcane leaf sheath microenvironment by FISH and PCR

Molecular tools for the detection of the newly described acetic acid bacterium Gluconacetobacter sacchari from the pink sugarcane mealybug, Saccharicoccus sacchari Cockerell (Homiptera: Pseudococcidae), and in the sugarcane leaf sheath microenvironment were developed. G. sacchari specific 16S rRNA-targeted oligonucleotide primers were designed and used in PCR amplification of G. sacchari DNA directly from mealybugs, and in a nested PCR to detect low numbers of the bacteria from sugarcane leaf sheath fluid and cane internode scrapings. A sensitivity level of detection of 40-400 cells/reaction was obtained using PCR from exponentially grown bacterial cultures and of 1-10 cells in cane internode scrapings and leaf sheath fluid samples using nested PCR. The specificity of the primer set was demonstrated by the lack of amplification product formation in PCR by closely related acetic acid bacteria, including Gluconacetobacter liquefaciens, and Gluconacetobacter diazotrophicus. A Cy3 labeled probe for G. sacchari was designed and shown to be specific for the species. Investigation of the mealybug microenvironment by whole cell fluorescent in situ hybridization revealed that G. sacchari appears to represent only a minor proportion of the population of the microbiota in the mealybugs tested. This study has shown the usefulness of 16S rRNA-based molecular tools in the identification and detection of G. sacchari from environmental samples and will allow these tools to be used in further ecological research.     

Comparison of Phenacoccus solenopsis specimens from different regions of Pakistan using COI molecular barcoding (Hemiptera: Pseudococcidae)

Because correct identification of insects is crucial for pest management involving chemical or biological control agents, we have used a molecular approach to identify and characterize specimens of the cotton pest Phenacoccus solenopsis Tinsley (Sternorrhyncha: Pseudococcidae) present in different regions of Pakistan. The specimens were analyzed through DNA sequence analysis of their mitochondrial COI (mtCOI) gene using an improved procedure that could distinguish between the pest and its associated parasitoid. Our analysis showed no variation among the mealybug specimens from different geographical locations of Pakistan and confirmed that this is the same species and haplotype that is infesting cotton plants in other parts of Asia. This information will assist in the development of biological control programs against P. solenopsis in Pakistan and other Asian countries.     

Predation of the apefly,Spalgis epius (Lepidoptera: Lycaenidae) on citrus mealybug,Planococcus citri (Hemiptera: Pseudococcidae)

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae) is a serious pest of economically important crops worldwide. The apefly, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) is a potential predator of various species of mealybugs. Earlier investigation on its daily preying capacity and preference for prey stages on P. citri is incomplete. Hence, a study was conducted to find out the daily prey consumption ability and preference for prey stages by different larval instars of S. epius reared on P. citri in the laboratory. Through the 8-day developmental period with four larval instars, the daily prey consumption of S. epius increased from the first to the seventh day and decreased on the eighth day prior to the prepupal stage. Generally, there was a significant difference in the prey consumption on different days. When the prey stages were offered separately, the first to fourth instar larva of S. epius consumed, respectively, a mean of 199.6, 722.6, 1908.8, and 4625.6 eggs or 21.5, 77.0, 168.5, and 670.5 nymphs or 3.2, 7.2, 16.0, and 35.1 adults of P. citri. When an S. epius larva was fed on P. citri eggs, nymphs and adults separately, it consumed a mean of 7456.7 eggs, 937.6 nymphs, or 62.3 adults during its entire development. When the prey stages were offered all together, a single S. epius larva consumed 2618.4 eggs, 170.4 nymphs, and 39.7 adults of P. citri throughout its entire development. The study revealed that S. epius is a voracious predator of P. citri and thus could be utilized as a major biological control agent.     

Intraguild predation of Planococcus ficus parasitoids Anagyrus pseudococci and Leptomastix dactylopii by Nephus kreissli

Intraguild predation of the mealybug parasitoids Anagyrus pseudococci (Girault), and Leptomastix dactylopii Howard (Hymenoptera: Encrytidae) by Nephus kreissli Fürsch & Uygun (Coleoptera: Coccinellidae) was studied. The latter is a native predator of the important pest Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae) on grapevines in Turkey. For this purpose, P. ficus of different ages parasitised by A. pseudococci or L. dactylopii, or by both A. pseudococci and L. dactylopii, were served to fourth instars and adults of N. kreissli as food. Experiments were conducted using two different treatments: no-choice (served unparasitised or only one stage of parasitised mealybug) and choice (served unparasitised and only one age of parasitised mealybug together), under controlled environmental conditions. Both fourth instars and adult predators were fed on two- and four-day-old mealybugs parasitised by A. pseudococci or on two-, four- and six-day-old mealybugs parasitised by L. dactylopii or by either A. pseudococci or L. dactylopii. The predators could not consume six-day-old mealybugs parasitised by A. pseudococci, eight-day-old mealybugs parasitised by L. dactylopii, or those parasitised by either of these parasitoids which had become mummified. While it was found that the adult predators preferred parasitised mealybugs to unparasitised, the larvae did not show a pronounced preference between parasitised and unparasitised mealybugs (except for mealybugs parasitised by A. pseudococci).     

白蜡绵粉蚧血细胞的显微形态与超微结构观察

为研究蚧虫血淋巴中血细胞的种类及其结构特征,本文采用荧光显微镜、扫描电镜和透射电镜观察了白蜡绵粉蚧Phenacoccus fraxinus Tang(半翅目:蚧总科:粉蚧科)雌成虫血细胞的显微形态超微结构.结果显示,在荧光显微镜和扫描电镜下观察识别出白蜡绵粉蚧血淋巴中的5种血细胞,即原血胞、浆血胞、粒血胞、类绛色血胞和囊血胞.在透射电镜下,原血胞的细胞核明显,表现出高的细胞质密度;浆血胞最典型的特征是细胞质中有大量的囊泡;粒血胞的细胞质中有发达的粗面内质网和许多玫瑰形的细颗粒;类绛色血胞最典型的特征是有许多结晶,并在细胞质空泡区内分布更多;囊血胞透明性强,具有围核空间,膨大成潴泡状.     

Mealybug, Phenococcus solani, and barley aphid, Sipha maydis, response to endophyte-infected tall and meadow fescues

Mealybugs and aphids are insects which damage grass species. The effects of fungal endophytes on the feeding of the mealybug, Phenococcus solani Ferris (Homoptera: Pseudococcidae), and barley aphid, Sipha maydis Passerini (Homoptera: Aphididae), on tall fescue, Festuca arundinacea Schreb. and meadow fescue, Festuca pratensis Huds., were studied under greenhouse conditions. Mealybugs preferred endophyte‐free (E–) clones over their endophyte‐infected (E+) counterparts. E+ plants had a significantly lower number of mealybugs than E– plants. A mixture of E+ and E– plants supported intermediate mealybug numbers, between pure plantings of E+ and E– grasses. Barley aphids released on to plant materials were deterred from feeding and could not persist on E+ plants. E– plants did not survive because of aphid damage, while E+ plants generally re‐grew, but were damaged to some degree. The results showed that the use of pure stands of endophyte‐infected grasses or a mixed stand of infected and non‐infected plants may increase the persistence and durability of turf and forage grass species in the presence of foliar damaging insects.     

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.      

Host–plant relationships and natural enemies of the invasive mealybug,Rastrococcus iceryoides Green in Kenya and Tanzania

The invasive mango mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae), believed to be native to southern Asia has rapidly invaded Kenya and Tanzania. A survey was carried out from February 2008 to July 2009 to study its geographical distribution, host–plant relationships and associated parasitoids in both countries. Our results infer that R. iceryoides is widely distributed across the coastal belts of both countries. Rastrococcus iceryoides was recorded from 29 cultivated and wild host plants from 16 families. Twenty‐one of these host plants are new records. Among the cultivated host plants, M. indica (407.68 ± 9.26/twig and 75.68 ± 7.13/leaf in Kibaha, and 595.86 ± 17.2/fruit in Kinondoni) and Cajanus cajan (L.) Millspaugh (18.15 ± 4.22/leaf and 233.62 ± 18.9/twig in Morogoro) recorded the highest levels of infestation. Parkinsonia aculeata (394.62 ± 11.7/twig, 0.15 ± 0.03/leaf and 8.44 ± 0.94/fruit in Kinango), Caesalpinia sepiaria Roxb. (3.33 ± 0.76/leaf and 155.81 ± 9.16/twig in Kinondoni) and Deinbollia borbonica Scheff. (2.70 ± 0.66/leaf and 112.65 ± 5.3/twig in Kibaha) were found to be the most heavily infested wild host plants. Six parasitoid species were recovered and are reported here for the first time to parasitize R. iceryoides. Anagyrus pseudococci Girault was the most dominant species accounting for 21% parasitism on M. indica and 20% parasitism on P. aculeata in Tanzania and Kenya, respectively. Despite this, the ability of the parasitoid to regulate the population of R. iceryoides was inadequate. Therefore, there is a need for foreign exploration and introduction of efficient coevolved natural enemies from its aboriginal home of southern Asia to minimize its impact on horticulture in Africa.