Temperatures lethal for citrus blackfly parasites,Encarsia opulenta andE. Smithi [Hym.: Aphelinidae]

Seasonally acclimatized adult and immature parasites of the citrus blackfly (CBF),Aleurocanthus woglumi Ashby, were exposed to high or low temperature extremes for 3 h periods. Death of all summer adults ofEncarsia opulenta Silvestri andE. smithi Silvestri occurred between 35° and 40°C. Within CBF hosts,E. opulenta were not able to emerge when temperatures reached between 45° and 50°C. In winter experiments adults of bothEncarsia species succumbed between −5° and −10°C. In a comparison of the 2 seasonal tests, a higher percentage ofE. smithi adults were able to survive both higher and lower temperatures thanE. opulenta, but the main interspecific difference was the ability ofE. opulenta within CBF to survive −10° to − 15°C whileE. smithi did not. Limited data forAmitus hesperidum Silvestri [Hym.: Platygasteridae] indicated that the immatures survived better at low, and not as well at high, temperatures as either species ofEncarsia. Florida Agricultural Experiment Station Journal Series # 5549.     

Variations in population levels of citrus blackfly,Aleurocanthus woglumi [Hom: Aleyrodidae] and parasites during an eradication program in Florida

From November, 1976 until October, 1979 citrus blackfly,Aleurocanthus woglumi Ashby and its parasite populations were sampled monthly in urban areas of Broward County, Florida. During this period, the parasites,Amitus hesperidum Silvestri andProspaltella opulenta Silvestri became established and exerted control onA. woglumi populations. Parasite succession was noted in thatA. hesperidum was first abundant and later replaced in abundance byP. opulenta. The 2 parasite species continued to coexist and exert mortality on low pest populations in spite of chemical spraying used for eradication showing that integrated control ofA. woglumi is a definite possibility now that the pest is well established in Florida.

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Résumé De novembre 1976 à octobre 1979, on a échantillonné mensuellement dans les zones urbaines du Comté de Broward, Floride, les populations de la mouche noire des citrus,Aleurocanthus woglumi Ashby et de ses parasites. Pendant cette période les parasites,Amitus hesperidum Silvestri etProspaltella opulenta Silvestri se sont établis et ont limité les populations deA. woglumi. Une succession dans les parasites a été notée:A. hesperidum fut abondant d'abord et remplacé ensuite en fréquence parP. opulenta. Les 2 espèces ont continué à coexister et causent la mortalité des faibles populations du ravageur malgré les traitements chimiques utilisés pour l'éradication; ce qui montre la possibilité d'une lutte intégrée contreA. woglumi maintenant que ce ravageur est bien établi en Floride.

     

Biological control ofAleurocanthus woglumi [Homoptera: Aleyrodidae] in El Salvador

The citrus blackfly,Aleurocanthus woglumi Ash., was first observed in El Salvador in 1965. Its dispersal was followed during a three-year period (1969–1972) in which it infested most citrus orchards in the country. Indigenous natural enemies as the predatorsDelphastus sp. andChrysopa sp., and the pathogenic fungusAschersonia aleyrodis Web. are unable to exert any economic control of the pest. The introduction of the parasiteProspaltella opulenta Silvestri from Mexico brought about the successful biological control of the pest. Life table studies carried out before and after introduction of the parasite helped to assess the value ofP. opulenta as an effective natural enemy of the citrus blackfly.

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Résumé L'Aleurode des citrus,Aleurocanthus woglumi Ash. a été observé pour la première fois en Salvador en 1965. Son extension a été suivie pendant trois ans de 1969 à 1972, au cours desquels il a envahi la plupart des vergers d'agrumes du pays. Les ennemis naturels indigènes, tels que les prédateursDelphastus sp. etChrysopa sp. ainsi que le champignon pathogèneAschersonia aleyrodis Web. ne sont pas capables d'avoir un effet économiquement satisfaisant. L'introduction du Mexique du parasiteProspaltella opulenta Silvestri a été un succès pour la lutte biologique contre ce ravageur. L'étude des tables de vie effectuée avant et après cette introduction confirme la valeur deP. opulenta comme ennemi naturel officace de l'Aleurode des citrus.

     

The introduction and establishment of parasites of citrus blackfly,Aleurocanthus woglumi in Florida [Hem.: Aleyrodidae]

Three species of laboratory-reared parasites of citrus blackfly,Aleurocanthus woglumi Ashby, were released at Fort Lauderdale, Florida in 1976 following discovery of this citrus pest in residential properties there.Amitus hesperidum Silv. andProspaltella opulenta Silv. were recovered 6 weeks after release and sharp increases in the rate of parasitism were observed throughout the season. Seven months after the initial release, 100% parasitism of citrus blackfly pupae was observed at some release sites, and 95% of the original release sites were found positive for the parasite. Observations after 1 year showed significant levels of parasitism over a large area. The rapid establishment and increase of these parasite species indicate that environmental conditions and the host at Fort Lauderdale are suitable for these species and that they may well provide control of the pest.     

Searching and ovipositional behavior ofAmitus hesperidum [Hym.: Platygasteridae] andEncarsia opulenta [Hym.: Aphelinidae] parasitoids of the citrus blackfly [Hom.: Aleyrodidae]

Searching behavior ofAmitus hesperidum Silvestri andEncarsia opulenta (Silvestri) for immatureAleurocanthus woglumi Ashby was similar. Both parasitoids moved unidirectionally until they encountered a host aggregation at which time they changed to a pattern of short walks with numerous turns. Parasitoid ovipositor insertion was generally at midbody between the host sternites and tergites.Amitus hesperidum females showed a significant preference for 1st instar hosts, have an ovipositional marker, do not feed on exudates from ovipositional wounds (host feed), and have significantly shorter ovipositional times and adult life spans thanE. opulenta which showed a significant preference for 2nd instar hosts, lack an ovipositional marker, and host feed.Encarsia opulenta females showed a significant preference for hosts previously parasitized byA. hesperidum but the reverse was not true. The average number of hosts parasitized by females of both parasitoid species was uninfluenced by the previous presence of the other parasitoid species on the same leaf.     

Synchrony and impact ofAmitus hesperidum [Hym.: Platygasteridae] on its host,Aleurocanthus woglumi [Hym.: Aleyrodidae] in southern Florida

The synchrony of the citrus blackfly (CBF)Aleurocanthus woglumi Ashby and its parasitoidAmitus hesperidum Silvestri was studied in southern Florida.A. hesperidum adults emerge from 4th instar nymphs 160–300 thermal units after CBF adults. This insured excellent temporal synchronization between the parasitoids and the early CBF instars they prefer since egg to 3rd instar nymph in CBF takes 380 thermal units. AlthoughA. hesperidum parasitized only 29% of the surviving 4th instar CBF, it was the factor responsible for the observed decline in the CBF population level in southern Florida.     

Prey selectivity inEuseius tularensis [Acari: Phytoseiidae]

Differences in responsiveness to potential prey and pollen were tested in the facultative predator,Euseius tularensis Congdon. Following isolation without food for 16 h, adult female mites were observed with one of the following potential foods: pollen ofMalephora crocea (Jacquin) Schwantes,Scirtothrips citri (Moulton) 2nd instar larvae,Tetranychus pacificus McGregor nymphs and ♂,Panonychus citri (McGregor) nymphs and ♂,E. hibisci (Chant) larvae, andE. tularensis larvae. Responses were compared using the proportion of encounters that resulted in consumption. This proportion was highest when pollen was encountered, followed byS. citri andT. pacificus. Consumption was much lower in response toP. citri and congeneric larvae. WhenS. citri larvae were encountered a 2nd time, 1 to 2 h after the initial capture and consumption, responsiveness increased to a level equal to the response observed with pollen. These results suggest thatE. tularensis is a more effective biological control agent of citrus thrips (S. citri) than of citrus red mite (P. citri).     

Survey traps for parasitoids, and coccinellid predators of the citrus blackfly, Aleurocanthus woglumi

The attractiveness of sticky traps of eight colors for two parasitoids Amitus hesperidum Silverstri and Prospaltella opulenta Silvestri, and seven species of coccinellid predators of the citrus blackfly, Aleurocanthus woglumi Ashby (Homoptera: Aleyrodidae) was evaluated in insectory and field tests.Yellow traps captured significantly more parasitoids and coccinellids than other colors tested; captures were greatest in traps placed in the lower half of citrus trees. These traps can be used to survey for and monitor the population trends of the citrus blackfly and its natural enemies.

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Résumé Nous avons évalué l'attraction de Amitus hesperidum Silvestri et Prospaltella opulenta Silvestri, parasitoïdes d'Aleurocanthus woglumi Ashby et de 7 espèces de Coccinellides prédatrices de cette espèce, par des pièges à glu de 8 couleurs différentes (jaune, orange, rouge, bleu, vert, noir, blanc et transparent).Les pièges jaunes capturent significativement plus de parasitoïdes et de coccinelles que les autres couleurs; les captures sont plus importantes avec des pièges placés dans la moitié inférieure des citronniers. Ces pièges peuvent être utilisés pour suivre et contrôler l'évolution des populations d'A. woglumi et de ses parasitoïdes et coccinelles prédatrices.

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Fla. Agr. Exp. Stn. J. Ser. No. 2271     

Importation,colonization and establishment ofAnagyrus indicus [Hym.: Encyrtidae] onNipaecoccus viridis [Hom.: Pseudococcidae] in Jordan

Anagyrus indicus Shafeeet al. was collected on the island of Guam and released in the Jordan River Valley of Jordan in order to regulateNipaecoccus viridis (Newstead) on citrus.A. indicus was originally released in February 1984 and became colonized by April of the same year. It also dispersed by natural means up to 61 km following the original release and colonized that same year on infestedZizyphus sp. By spring of 1985 it became the dominant parasitoid attackingN. viridis. Another parasitoid,Anagyrus kamali Moursi, was collected in Jordan in June of 1985 for the first time. This latter parasitoid apparently moved into the Jordan River Valley by means of natural dispersal from a neighboring country. Infestations ofN. viridis have been greatly reduced in areas whereA. indicus became established. This paper reports the results of research only. Mention of a proprietary product does not constitute an endorsement for its use by USDA.     

Physiological characteristics of citrus plants infested with citrus blackfly

Aleurocanthus woglumi (Ashby, 1915) is an important agricultural pest that causes yield losses of 20–80% in citrus plants by removing plant nutrients while feeding and allowing the formation of sooty mold. The objective of this study was to evaluate physiological changes in citrus plants in response to A. woglumi infestation under field conditions. The experiment was conducted in a citrus orchard in Paço do Lumiar, Maranhão, Brazil. Thirty-two citrus plants were used, including eight of each of the following varieties: Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine. Four random plants with A. woglumi infestation and four plants free from this pest were selected from each variety. The physiological parameters evaluated were photochemical efficiency and gas exchange. Regarding photochemical efficiency, infested plants presented photoinhibition damage, with a performance index of 4.22. The gas exchange parameters of infested plants changed, with reductions in photosynthetic CO₂ assimilation of 69.7% (Tahiti), 64% (Tanjaroa), 68.8% (Nissey) and 63.3% (Ponkan). Plants infested with A. woglumi also presented physiological changes; their photosynthetic CO₂ assimilation, stomatal conductance, instantaneous transpiration, and performance indexes were affected. The infested citrus plants showed photoinhibition of photosystem II. The photosynthetic CO₂ assimilation decreased approximately 70% in Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine plants infested with A. woglumi.     

Studies onBonnetia comta [Dipt.: Tachinidae] parasitizingAgrotis ipsilon [Lep.: Noctuidae] larvae

Laboratory studies showed that 1st-instarBonnetia comta (Fallén) maggots (planidia) had a significant impact (P<0.05) on mortality of all black cutworm (BCW),Agrotis ipsilon (Hufnagel), instars, either by killing 1st- and 2nd-instar BCWs 2.3 to 9.7 days after parasitization or by producing a puparium from older host instars. Diet consumption and utilization by BCW larvae parasitized byB. comta as 4th instars were similar to those of nonparasitized larvae until 1 to 2 days before the parasitoid emerged. In a 2-year host exposure study in Iowa, it was found thatB. comta primarily parasitized released BCWs in June through September and did not seem to play a role in controlling the damaging 1st generation of BCW larvae. Techniques were developed to produce and store large numbers ofB. comta planidia.Bonnetia comta deposited large numbers of planidia on filter paper treated with a fecal supernatant. These planidia could be stored on filter paper in a covered Petri dish at 4.4°C for 5 days with minimal mortality. Preliminary field data show that planidia placed around corn seedlings infested with 4th-instar BCW larvae do parasitize the pest and reduce the hosts cutting potential.     

Classical Biological Control of the Citrus Blackfly <Emphasis Type="Italic">Aleurocanthus Woglumi</Emphasis> by <Emphasis Type="Italic">Amitus Hesperidum</Emphasis> in Trinidad

The citrus blackfly Aleurocanthus woglumi Ashby (Homoptera: Aleyrodidae), a native of South East Asia, was first reported in Trinidad in 1998. As part of a classical biological control programme against the pest, releases of Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) were made in Trinidad from June to August 2000. Field studies were conducted on three commercial citrus farms, two large estates ( >500 ha) and one small orchard (<50 ha) where releases were initially made. Adult blackfly and Amitus populations were monitored weekly with yellow sticky traps. Immature blackfly and parasitism rates were monitored monthly by field sampling. During the study period, citrus blackfly populations declined by more than 98% at all sites while parasitism increased to 60–90%. There were, however, differences between locations, with control at Cumuto being reached within 4 months, at Todd’s Road between 6 and 7 months and at La Gloria about 13 months. This was consistent with the parasitism rates recorded. Although Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) was also introduced, it would seem that A. hesperidum was capable of bringing down and maintaining citrus blackfly populations at acceptable levels by itself.     

Hexamermis glossinae [Nematoda: Mermithidae] parasitizing tsetse [Diptera: Glossinidae] in Kenya

Glossina pallidipes Austen,G. brevipalpis Newstead andG. austeni Newstead were collected from 5 sites along the south Kenyan coast over a 2 year period. They were dissected and examined for nematodes. Three of the sites yielded tsetse parasitized by juvenile mermithids identified asHexamermis glossinae Poinar et al. Glossina pallidipes andG. brevipalpis are new host records for this parasite, whileG. austeni was captured infrequently and only at a site that failed to yield other parasitized tsetse. Parasite prevalence was low (0.16–0.61 %) and did not differ between male and female hosts. More tsetse than expected by chance harboured nematodes during the long rains season (April–August) than during the short rains (September–November) or dry season (December–March). Early juvenile stages (0.5–2.5 mm long) were recovered mainly from tsetse less than 50 days old, while late juvenile stages (35–85 mm long) were only found in flies older than 30 days. Late stages occurred singly while early ones usually occurred as two or more per host.     

Lethal temperatures of citrus blackflyAleurocanthus woglumi [Hom.: Aleyrodidae] and its parasite,Amitus hesperidum [Hym.: Platygasteridae]

Seasonally acclimatized citrus blackfly (CBF),Aleurocanthus woglumi Ashby, and its parasite,Amitus hesperidum Silv. were exposed to extreme temperatures for 3-hour periods and survivorship measured. In summer experiments, the LD₅₀ for CBF adults and 1st instar nymphs occurred between 40° and 45°C. The LD₅₀ forA. hesperidum adults occurred between 35° and 40°C and increased with decreased humidity, although some adults could continue to emerge from parasitized CBF up to 45°C. In winter experiments, the LD₅₀ for CBF eggs and adults occurred between ?5° and ?10°C and for other CBF stages between ?10° and ?15°C. The LD₅₀ for adultA. hesperidum, and survival and emergence of the parasites from CBF both occurred between ?10° and ?15°C. Comparing data from the 2 seasons shows that adults are the most temperature sensitive stage of CBF and the parasite is more temperature sensitive than CBF, especially at higher temperatures. Correlating lethal temperature data with field meteorological conditions shows that short-term temperature exposures cannot be expected to stop the potential spread of CBF orA. hesperidum through Florida.     

Parasitism byEphedrus cerasicola [Hym.: Aphidiidae] developing in different stages ofMyzus persicae [Hom.: Aphididae]

The parasitoidEphedrus cerasicola Stary oviposited in the 4 nymphal instars and in newly moulted apterous adults ofMyzus persicae (Sulzer). Development and reproduction of unparasitized and parasitized aphids at 21°C were compared. Unparasitized aphids developed to adults in 6.5 days and started to reproduce after 7 days. Longevity varied between 7 and 42 days. Net reproductive rate (R₀) was 40.7. In contrast to older nymphs, aphids parasitized in the 1 st instar almost never reached the adult stage before mummification. Aphids parasitized in 2nd, 3rd and 4th instar and as newly moulted adults produced respectively 0.07 %, 2 %, 23 % and 32 % of offspring produced by unparasitized aphids. Corresponding reproductive periods were 1, 1.4, 3 and 4 days. Host age at parasitization had a slight effect on the parasitoid's developmental rate and had no effect on egg or pupal survival, or on the sex ratio of the emerging parasitoids.     

Susceptibility of two Coconut Pests,Oryctes rhinoceros [Col.: Scarabaeidae] andTirathaba rufivena [Lep.: Pyralidae], to the entomoparasitic nematodeSteinernema feltiae [= Neoaplectana carpocapsae]

Bioassay indicated that 1 st instar larvae ofOryctes rhinoceros are resistant to infections by the nematodeSteinernema feltiae (estimated LD₅₀: 90 nematodes) but thatTirathaba rufivena larvae larger than 15 mm are highly susceptible (estimated LD₅₀: 3 nematodes). The “All” strain and the “mexican” strain ofS. feltiae gave very similar responses. In a field trial 300,000 nematodes were sprayed on each of 25 palms to controlT. rufivena. Although some mortality from nematodes was observed, the treatment failed to reduce the pest population significantly.     

Fungal Phyllosphere Communities are Altered by Indirect Interactions Among Trophic Levels

Trophic interactions involving predators, herbivores, and plants have been described in terrestrial systems. However, there is almost no information on the effect of trophic interactions on microbial phyllosphere community abundance, diversity, or structure. In this study, the interaction between a parasitoid, an insect herbivore, and the fungal phyllosphere community is examined. Parasitoid wasps have an indirect negative impact on fungal community diversity. On the citrus phyllosphere, the exotic wasp species, Amitus hesperidum and Encarsia opulenta, may parasitize the citrus blackfly (Aleurocanthus woglumi). If parasitism levels are low, the blackfly may produce significant amounts of honeydew secretions on the surface of the leaf. Honeydew deposition provides a carbon-rich substrate for the development of fungal growth persisting as sooty mold on the leaves. Leaves from sooty mold-infested grapefruit (Citrus paradisi) trees were collected from multiple orchards in south Texas. The effect of different levels of exotic parasite activity, citrus blackfly, and sooty mold infestation on phyllosphere mycobiota community structure and diversity was examined. Our results suggest the presence of the parasitoid may lead to a top–down trophic cascade affecting phyllosphere fungal community diversity and structure. Additionally, persistent sooty mold deposits that have classically been referred to as Capnodium citri (and related asexual morphological forms) actually comprise a myriad of fungal species including many saprophytes and potential fruit and foliar pathogens of citrus.     

Successful colonization ofEretmocerus debachi (Hym.: Aphelinidae) in the eastern mediterranean citrus region of Turkey

The whitefly,Parabemisia myricae (Kuwana) is one of the most serious citrus pests in the Eastern Mediterranean region of Turkey. In 1986, a host-specific parasitoid ofP. myricae, the aphelinidEretmocerus debachi Rose and Rosen, was imported from California to Turkey and released into citrus orchards along the Eastern Mediterranean coast. In the following yearsP. myricae-populations were rapidly reduced from about 17 whitefly-immature stages per leaf to less than 0.1 stages per leaf in all citrus orchards where the parasitoids were released. Furthermore,E. debachi was shown to be a good disperser and it is well adapted to the climatic conditions in the Eastern Mediterranean region. Since the successful colonization ofE. debachi, the whitefly is no longer a serious pest and it is difficult to find unparasitized individuals in the Eastern Mediterranean region of Turkey.     

Distribution and effectiveness ofAnaphes diana [=Patasson lameerei] [Hym.: Mymaridae], a parasitoid ofSitona spp. Eggs [Col.: Curculionidae] in the Mediterranean region

Surveys conducted from 1973 to 1984 showed thatAnaphes diana Girault was the predominant parasitoid ofSitona spp. eggs throughout the Mediterranean range of Spain, France, Italy, Greece, Bulgaria, Romania, Turkey and Syria. In each of these countries, the mean percentage parasitism of eggs fluctuated between 1.9 and 23.9%. The impact of the mymarid on its host increased considerably from autumn to spring. Two biotypes ofA. diana, one reproducing bisexually, the other being strictly thelytokous, occur sympatrically in the Mediterranean region. The origin of various consignments ofSitona eggs parasitized byA. diana shipped to Australia for field release of the mymarid is recorded. Egg parasitoids were found in the Damascus area (Syria) that may be adapted to and effective under the hot and dry climatic conditions of South Australia.     

A survey of black scale,Saissetia oleae [Hom.: Coccidae] parasitoids [Hym.: Chalcidoidea] in southern California

A survey of black scaleSaissetia oleae (Olivier) parasitoids present in southern California was conducted between September 1987 and September 1989. From 308 collections of black scale-infested citrus, olive, and oleander twigs from 19 sites in southern California, 1,610 specimens were collected. Nine primary and six secondary parasitoid species were identified. Four primary species were abundant in southern California:Metaphycus bartletti Annecke & Mynhardt,M. helvolus (Compere),Scutellista caerulea (Fonscolombe) (=S. cyanea Motschulsky), andDiversinervus elegans Silvestri. The most common secondary parasitoids wereMarietta mexicana (Howard),Cheiloneurus noxius Compere, andTetrastichus minutus (Howard). In the coastal region of southern California,M. bartletti was the most abundant parasitoid, followed in order byD. elegans, S. Caerulea, andM. helvolus. In the intermediate and interior regions,M. helvolus was most abundant.D. elegans was second most abundant in the intermediate region, but was rare in the interior region.M. bartletti was second in abundance in the interior region and third in the intermediate region.