Christina D. Hoddle

The Lesser of Two Weevils: Molecular-Genetics of Pest Palm Weevil Populations Confirm Rhynchophorus vulneratus (Panzer 1798) as a Valid Species Distinct from R. ferrugineus (Olivier 1790), and Reveal the Global Extent of Both

The red palm weevil (RPW) is a major pest of palms. It is native to southeast Asia and Melanesia, but in recent decades has vastly expanded its range as the result of multiple accidental anthropogenic introductions into the Middle East, Mediterranean Basin, Caribbean, and U.S.A. Currently regarded as a single species, Rhynchophorus ferrugineus (Olivier), RPW displays remarkable color variation across its range, and consequently has a taxonomic history littered with new species descriptions and synonymization. We compared DNA sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene from RPW populations throughout the native and invaded ranges, to investigate the specific status and invasion history of this serious economic pest, and to identify possible common routes of entry. Analyses of COI haplotype data provide conclusive support, corroborated by sequences of additional nuclear gene regions, for the existence of at least two predominantly allopatric species. The true R. ferrugineus is native only to the northern and western parts of continental southeast Asia, Sri Lanka and the Philippines, and is responsible for almost all invasive populations worldwide. In contrast, the second species, which is currently synonymized under R. ferrugineus and should be resurrected under the name R. vulneratus (Panzer), has a more southern distribution across Indonesia, and is responsible for only one invasive population; that in California, U.S.A. The distribution of COI haplotypes is used to discuss the possible existence of further cryptic species, sources and routes of entry of different invasive populations, and the implications of our findings for current control methods.

Competition between honeydew producers in an ant-hemipteran interaction may enhance biological control of an invasive pest.

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an invasive citrus pest in southern California, which secretes honeydew and has the potential to spread a lethal bacterial disease, huanglongbing, of citrus. In urban citrus, Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), also an invasive pest, tends honeydew-producing hemipterans. We used field data to determine whether the mutualistic relationship between L. humile and six established species of honeydew producers may hinder or favor the establishment of D. citri and its biological control with Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) in citrus via competition or mutualism for ants, respectively. In the field, L. humile and D. citri are engaged in a mutualistic relationship. Ants harvest solid honeydew secreted by psyllid nymphs and tended more than 55% of observed D. citri colonies. Linepithema humile displayed a preference hierarchy when tending honeydew producers infesting citrus. It responded equally or less intensively to D. citri than to other honeydew-producing species. Consequently, the mutualism between L. humile and D. citri was affected by the presence of other honeydew-producing species, and the percentage of D. citri colonies tended by L. humile. The number of ants per D. citri colony also decreased as the number of other honeydew producers increased. Diaphorina citri density was also affected by the presence of other honeydew producers. Both colony size and the number of D. citri nymphs counted per tree decreased as the number of other honeydew producers increased. Our results indicate that competition between honeydew producers for the mutualist ant L. humile may hinder the establishment of D. citri by possibly facilitating increased biological control.

How Far Can the Red Palm Weevil (Coleoptera: Curculionidae) Fly?: Computerized Flight Mill Studies with Field-Captured Weevils

ABSTRACT Adult Rhynchophorus ferrugineus (Olivier) captured in pheromone-baited traps in commercial date palm orchards in the Al Ahsaa Directorate, Kingdom of Saudi Arabia, were used in computerized flight mill studies to determine the flight characteristics of this highly invasive and destructive palm pest. Flight mill studies were run at three different time periods, winter (December), spring (March), and summer (May). Of the 192 weevils tethered to flight mills ∼30% failed to fly>1 km. Of those weevils flying>1 km(n=139), 55% flew>10 km, and of these flyers 5% flew>50 km in 24 h. Flying weevils exhibited an average weight loss of 20–30% and nonflying control weevils lost ∼9–13% body weight in 24 h. Male and female weevils flying in summer (average laboratory temperature was ∼27° C) flew the longest average distances (∼25–35 km), exhibited highest weight reductions (∼30%), and greatest mortality rates (∼80%). Consequently, time of year not weevil sex or color morph had a consistent and significant effect on flight activity, weight loss, and survivorship rates. Flight activity was predominantly diurnal commencing around 5:00 a.m. and peaking between 9–11:00 a.m. before tapering off. The distribution of flight distances combined across season and sex was mesokurtic (i.e., normally distributed).

Phenology of Asian Citrus Psyllid (Hemiptera: Liviidae) and Associated Parasitoids on Two Species of Citrus, Kinnow Mandarin and Sweet Orange, in Punjab Pakistan

ABSTRACT The population phenology of Asian citrus psyllid, Diaphorina citri Kuwayama, was monitored weekly for 110 wk on two species of Citrus, kinnow mandarin and sweet orange, at two different research sites in Faisalabad, Punjab Pakistan. Citrus flush growth patterns were monitored and natural enemy surveys were conducted weekly. Flush patterns were similar for kinnow and sweet orange. However, flush on sweet orange was consistently more heavily infested with Asian citrus psyllid than kinnow flush; densities of Asian citrus psyllid eggs, nymphs, and adults were higher on sweet orange when compared with kinnow. When measured in terms of mean cumulative insect or Asian citrus psyllid days, eggs, nymphs, and adults were significantly higher on sweet orange than kinnow. Two parasitoids were recorded attacking Asian citrus psyllid nymphs, Tamarixia radiata (Waterston) and Diaphorencyrtus aligarhensis (Shafee, Alam and Agarwal). The dominant parasitoid species attacking Asian citrus psyllid nymphs on kinnow and sweet orange was T. radiata, with parasitism averaging 26%. D. aligarhensis parasitism averaged 17%. Generalist predators such as coccinellids and chrysopids were collected infrequently and were likely not important natural enemies at these study sites. Immature spiders, in particular, salticids and yellow sac spiders, were common and may be important predators of all Asian citrus psyllid life stages. Low year round Asian citrus psyllid densities on kinnow and possibly high summer temperatures, may, in part, contribute to the success of this cultivar in Punjab where Candidatus Liberibacter asiaticus, the putative causative agent of huanglongbing, a debilitating citrus disease, is widespread and vectored by Asian citrus psyllid.

Field optimization of the sex pheromone of Stenoma catenifer (Lepidoptera: Elachistidae): evaluation of lure types, trap height, male flight distances, and number of traps needed per avocado orchard for detection.

The sex pheromone of Stenoma catenifer was evaluated in commercial avocado orchards in Guatemala to determine operational parameters, such as optimal lure type, trap height, trap density and estimates of the distances that male moths fly. Of four pheromone dispensers tested, gray and white rubber septa were of equal efficacy, whereas 1-ml low-density polyethylene vials and 2×3-cm polyethylene ziplock bags were least efficacious. The height at which wing traps were hung did not significantly affect the number of adult male S. catenifer captured. For monitoring S. catenifer, these data suggest that the pheromone should be dispensed from gray rubber septa in wing traps hung inside the tree canopy at 1.75 m, a height convenient for trap placement and monitoring. Mark-recapture studies of male S. catenifer indicated that, on average, males flew 67 m in one night. However, it is likely that this is an underestimate of the distance that male moths are capable of flying in a single night. Probabilistic modeling of S. catenifer capture data from different numbers of pheromone traps deployed in seven commercial avocado orchards of varying sizes and infestation levels suggested that 10-13 randomly deployed traps per orchard for a 7-day period are needed to detect at least one male S. catenifer with 90% confidence. These data provide sufficient information to develop effective protocols for using the S. catenifer pheromone to detect and monitor this pest in countries with endemic populations that are exporting fresh avocados, and for quarantine detection and incursion monitoring in countries receiving avocado imports from high risk areas.

Bioecology of Stenoma catenifer (Lepidoptera: Elachistidae) and Associated Larval Parasitoids Reared from Hass Avocados in Guatemala

Abstract A 10-wk study of the avocado seed-feeding moth Stenoma catenifer Walsingham (Lepidoptera: Elachistidae), was conducted in a commercial ‘Hass’ avocado (Persea americana Miller [Lauraceae]) orchard in Guatemala. Up to 45% of fruit in the orchard were damaged by larval S. catenifer. Larval-to-adult survivorship for 1,881 S. catenifer larvae in Hass fruit was 37%, and adult sex ratio was 51% female. Four species of larval parasitoid were reared from field-collected S. catenifer larvae. The most common parasitoid reared was a gregarious Apanteles sp., which parasitized 53% of larvae and produced on average eight to nine cocoons per host. Apanteles sp. sex ratio was 47% female and 87% of parasitoids emerged successfully from cocoons. Apanteles sp. longevity was ≈1.5 d in the absence of food, and when provisioned with honey, parasitoids survived for 5–7 d. The mean number of cocoons produced by Apanteles sp. per host, and larval parasitism rates were not significantly affected by the number of S. catenifer larvae inhabiting seeds. Oviposition studies conducted with S. catenifer in the laboratory indicated that this moth lays significantly more eggs on the branch to which the fruit pedicel is attached than on avocado fruit. When given a choice between Hass and non-Hass avocados, S. catenifer lays up to 2.69 times more eggs on Hass.

Inventory of Thysanoptera Collected from French Polynesia

ABSTRACT A survey for Thysanoptera was conducted in the Society (Tahiti, Moorea, and Raiatea), Marquesas (Hiva Oa, Nuku Hiva, Ua Huka, and Ua Pou), and Austral islands (Rurutu and Tubuai) archipelagos in French Polynesia from September 2003 to November 2005. At least 55 thrips species in 36 genera and three families were identified from 823 slide-mounted specimens that were collected from 61 host plants in 33 families. Twelve species are considered to be important pests. The greatest diversity of species, 43 (77%), was collected from the Society Islands, with 60% being recorded from Tahiti alone. Species diversity was intermediate in the Marquesas Islands at 43% (24 species collected), with 35% or 19 species being recorded from Nuku Hiva. Lowest diversity was recorded for the Austral Islands, with 38% or 21 species being found in that archipelago. Less than 10% of collected species are likely to be native, with the majority of identified thrips (>90%) in French Polynesia representing a high diversity of exotic species (leaf, flower, and fungus feeders, and four predatory species) that have successfully infiltrated other island groups in the South Pacific. Survey results and subsequent estimates of thrips species diversity in French Polynesia should be interpreted with caution due to uncontrolled variation in sampling intensity that was affected by survey duration, time of year, and visitation frequency to islands.

Marietta leopardina (Hymenoptera: Aphelinidae) and Aprostocetus (Aprostocetus) sp. (Hymenoptera: Eulophidae) are Obligate Hyperparasitoids of Tamarixia radiata (Eulophidae) and Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae)

Marietta leopardina and Aprostocteus (Aprostocetus) sp. that emerged from Diaphorina citri nymphs collected from the Pakistani Punjab and exposed in quarantine to D. citri nymphs parasitized by Tamarixia radiata or Diaphorencyrtus aligarhensis successfully emerged from both of these primary parasitoids. Marietta leopardina and A. (Aprostocetus) sp. did not reproduce on unparasitized D. citri nymphs. These exposure experiments confirmed that M. leopardina and A. (Aprostocetus) sp. are obligatory hyperparasitoids of T. radiata and D. aligarhensis in the Diaphorina-Tamarixia-Diaphorencyrtus system. Marietta leopardina y Aprostocteus (Aprostocetus) sp. emergidos de ninfas de Diaphorina citri recolectadas en Punjab de Pakistan fueron expuestos en cuarentena sobre ninfas de D. citri parasitadas por Tamarixia radiata o Diaphorencyrtus aligarhensis, logrando emerge con exito de estos dos parasitoides primarios. Marietta leopardina y A. (Aprostocetus) sp. no se reproducieron en ninfas de D. citri no parasitadas. Estos experimentos de exposicion confirmaron que M. leopardina y A. (Aprostocetus) sp. son hiperparasitoides obligatorios de T. radiata y D. aligarhensis en el sistema de Diaphorina-Tamarixia-Diaphorencyrtus.

Lepidoptera and Associated Parasitoids Attacking Hass and Non-Hass Avocados in Guatemala

Abstract A 5-mo survey for fruit feeding Lepidoptera attacking Hass and non-Hass avocados (Persea americana Miller [Lauraceae]) was conducted in Guatemala from 1 November 2006 to 1 April 2007. In total, 6,740 fruit were collected from 22 different areas in Guatemala. Eight species of Lepidoptera, of which at least two are species new to science, were reared from avocado fruit. Reared Lepidoptera were Amorbia santamaria Phillips and Powell, Cryptaspasma sp. nr. lugubris, Euxoa sorella Schaus, Histura n. sp., Holcocera n. sp., Micrathetis triplex Walker, Netechma pyrrhodelta (Meyrick), and Stenoma catenifer Walsingham. Hymenopteran parasitoids were reared from larvae of C. sp. nr. lugubris and S. catenifer. One species of parasitoid, Pseudophanerotoma sp., was reared from field collected C. sp. nr. lugubris larvae. The dominant parasitoid reared from S. catenifer was a gregarious Apanteles sp. Other parasitoid species reared from S. catenifer larvae were Brachycyrtus sp., Macrocentrus sp., and Pristomerus sp. The oviposition preference of C. sp. nr. lugubris for avocado fruit hanging in trees, dropped fruit on the ground, or exposed avocado seeds was investigated by studying the oviposition preferences of adult female moths and determining egg hatch times in the laboratory, and by investigating the longevity of avocado fruit on the ground under prevailing field conditions. Together, data from these studies suggested that C. sp. nr. lugubris may be an unrecognized pest of avocados that causes hanging fruit to drop to the ground prematurely. The influence of season and altitude on the phenology and distribution of avocado feeding Lepidoptera in Guatemala is discussed.

How Many Primary Parasitoid Species Attack Nymphs of Diaphorina citri (Hemiptera: Liviidae) in Punjab, Pakistan?

Summary Hussain & Nath (1927) stated that 9 species of parasitoids attack nymphs of Diaphorina citri Kuwayama (Hemiptera: Liviidae) in Punjab Province of Pakistan. Foreign exploration for natural enemies of D. citri over Mar 2011 to Mar 2013 in Punjab Pakistan resulted in the collection of 3,675 parasitoids representing at least 13 different species. However, just 2 species of primary parasitoids, Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) (55% of collected specimens) and Diaphorencyrtus aligarhensis (Shafee, Alam & Agarwal) (Hymenoptera: Encyrtidae) (28% of collected material) attacked D. citri nymphs and 5 species of hyperparasitoids attacked the immature stages of these two primary parasitoids. The remaining 11 parasitoid species that were identified likely attacked unnoticed insect species that co-infested foliage with D. citri nymphs. We conclude that Hussain & Nath (1927) overestimated the number of primary parasitoids attacking D. citri nymphs in Punjab Pakistan.