High Levels Of Parasitism Research Articles

Isolation and characterization of polymorphic microsatellites isolated from the spotless starling (Sturnus unicolor) and cross‐species amplification in the European starling (Sturnus vulgaris)

AbstractSpotless and European starlings (Sturnus unicolor and Sturnus vulgaris) have attracted attention from researchers interested in sexual selection, evolution of parental care and reproductive strategies. Both species show high levels of intraspecific nest parasitism and extra‐pair paternity, but research in this area is hampered by a lack of molecular markers specific for these species. Here, we describe a set of primers for nine microsatellite loci in spotless starlings, eight of which are highly polymorphic (7.37 alleles in average). These microsatellites are also polymorphic in European starlings (6.75 alleles in average).

Mechanism of egg recognition in defenses against conspecific brood parasitism: American coots (Fulica americana) know their own eggs

Hosts of avian brood parasites use a variety of defenses based on egg recognition to reduce the costs of parasitism; the most important of which is rejecting the parasitic eggs. Two basic recognition mechanisms are possible: “true recognition”, whereby hosts recognize their own eggs irrespective of their relative frequency in the clutch, and minority recognition (or “recognition by discordancy”), whereby hosts respond to the minority egg type. The mechanism of recognition has been experimentally studied in a handful of species parasitized by interspecific brood parasites, but the mechanism used in defenses against conspecific brood parasitism is unknown. I experimentally determined the mechanism of egg recognition in American coots (Fulica americana), a species with high levels of conspecific brood parasitism, egg recognition, and rejection. I swapped eggs between pairs of nests to alter frequencies of host and “parasite” eggs and then used two criteria for recognition: egg rejection and nonrandom incubation positions in the clutch. Eight of 12 nests (66%) given equal frequencies of host and parasite eggs showed evidence of true recognition. In contrast, only one of eight (12.5%) nests where host eggs were in the minority showed evidence of recognition by discordancy. The nonrandom incubation positions of parasitic eggs indicates that birds sometimes recognize parasitic eggs without rejecting them and provides a means of assessing recognition on a per nest basis in species with large clutches. Adaptive recognition without rejection may also be an important evolutionary stepping stone to the evolution of egg rejection in some taxa.

Drought stress differentially affects leaf‐mining species

Abstract 1. The impact of climate change on phytophages is difficult to predict, due in part to variation between species in their responses to factors such as drought stress. Here, the hypothesis that several species within the leaf‐mining feeding guild will respond in a consistent way to changes in rainfall patterns is tested, using a manipulative field experiment.2. Summer drought, enhanced summer rainfall, and control treatments were imposed on a calcareous grassland community, and the responses of five leaf‐mining species were assessed.3. One leaf‐mining species was more abundant under enhanced rainfall, one was more abundant under drought, and the other three species showed no consistent response to the rainfall treatments. Higher parasitism levels under drought may partly explain the response of one species (Stephensia brunnichella) to the treatments.4. These results show that generalisations relating to drought stress impacts cannot be drawn at the feeding guild level for leaf‐mining insects.

Factors Influencing the Incidence of Cowbird Parasitism of Least Bell's Vireos

Least Bell's vireo (Vireo bellii pusillus) is a federally endangered subspecies of Bell's vireo subject to high levels of brood parasitism by brown-headed cowbirds (Molothrus ater). Brood parasitism greatly reduces the reproductive success of the vireo. We examined the relationship of vegetation structure surrounding nests and of activity near the nest to the incidence of brood parasitism by brown-headed cowbirds of least Bell's vireos. We examined vegetation structure at 3 spatial scales: microhabitat (0–1 m from a nest), mesohabitat (1–11.3 m from a nest), and macrohabitat (greater than 11.3 m from a nest). Nests with high microhabitat cover and mesohabitat cover within 5 m of the nest had a lower incidence of parasitism than those with low cover at these scales. Unparasitized nests had fewer trees greater than 8-cm diameter at breast height (dbh) within 11.3 m, and they had less canopy cover within 5 m than parasitized nests. Cowbirds parasitized nests farther from the edge of the riparian habitat more often than nests near the edge. Activity near the nest did not differ significantly between parasitized and unparasitized nests. We suggest that microhabitat cover is the most important habitat feature influencing the incidence of brood parasitism of least Bell's vireos, and we conclude that cover near the nest reduces the chance that a cowbird will observe nesting activity. We suggest that habitat management for improved breeding success of least Bell's vireos focus on increasing the density of understory vegetation.

Pre-dispersal seed predation byBruchidius villosus(Coleoptera, Bruchidae) inLaburnum anagyroides(Fabaceae, Genisteae)

The pre-dispersal seed predator, Bruchidius villosus (Coleoptera, Bruchidae) destroyed ca. 8% of seeds of its major host-plant, Laburnum anagyroides (Fabaceae, Genisteae), a tree-like legume, in Hungary. However, almost 40% of the pods were infested by the beetle. Females did not show a resource concentration response: with increasing number of seeds per pod, the number of uninfested seeds also increased. A high seed abortion rate of 75% left an average of two full-grown seeds per pod. Females laid three-four times more eggs on pods than the number of full-grown seeds present in a pod. Despite this, a high level (ca. 15%) of egg parasitism and pod abortion that reached levels up to 50% on pods which already bore bruchid eggs, decreased the infestation level. Larval parasitisation rate of B. villosus by chalcids and braconids exceeded 30%.

Do parasites matter? Assessing the fitness consequences of haemogregarine infection in snakes

Although much research in evolutionary ecology is based upon the premise that high levels of parasitism impair the host's functioning, the assumed link between parasitism and fitness has been assessed for relatively few kinds of animals. At our study site in tropical Australia, keelback snakes ( Tropidonophis mairii (Gray, 1841), Colubridae) are heavily infected with haemogregarine blood parasites: 90% of snakes that we tested carried the parasite, with the proportion of erythrocytes containing haemogregarines averaging 15% and ranging up to a remarkable 64%. Prevalence increased with snake body size, but intensity decreased with age. Unlike lizards studied previously, the snakes did not respond to haemogregarine infection by releasing immature erythrocytes into the circulation. In striking contrast to results from a recent study on a sympatric snake species, we did not find any empirical links between parasite numbers and several measures of host fitness (body condition, growth rate, feeding rate, antipredator behaviour, locomotor performance, reproductive status, reproductive output, and recapture rate). The association between this parasite and its host thus appears to be surprisingly benign, suggesting that host–parasite interactions sometimes may have only trivial consequences for host fitness in natural populations. Plausibly, host–parasite coevolution weakens or eliminates fitness costs of parasitism.

Effects of the introduced ectoparasitePhilornis downsion haemoglobin level and nestling survival in Darwin's Small Ground Finch (Geospiza fuliginosa)

Abstract: The physiological impacts and fitness costs of parasitism by an introduced ectoparasitic fly,Philornis downsi(Muscidae), were studied in nestlings of Darwin's Small Ground Finch,Geospiza fuliginosa(Geospizinae), on the Galápagos Archipelago. Whole blood haemoglobin (Hb) concentration was used to measure host response to ectoparasitism due to its high repeatability and validity, as well as for its key role in aerobic activities that affect fitness, such as flight capacity and nestling begging intensity. Increased numbers of ectoparasitic larvae ofP. downsiwere strongly correlated with lower Hb levels in nestlings in the absence of blood parasites. Furthermore, immature red blood cell counts were negatively correlated with Hb level and positively correlated withP. downsiintensity. Nestlings with high levels of parasitism suffered higher mortality, which varied with clutch size. Our results provide evidence that endemic Galápagos bird populations are physiologically compromised byP. downsiand experience substantial fitness costs due to ectoparasitism.

Parasitism of maternal investment selects for increased clutch size and brood reduction in a host

The allocation of resources to young that will ultimately be left to die appears counterintuitive. Yet obligate brood reduction has evolved in a number of species, despite the waste of reproductive investment this may incur. Here we test whether brood parasitism could be one factor leading to the evolution of obligate brood reduction because surplus eggs in the nest during incubation offer some protection from the costs of parasitism. Surplus eggs could benefit females in two ways. First, additional eggs may protect against the direct costs of parasitism by facilitating recognition and removal of parasitic eggs with greater accuracy. Second, additional eggs may protect against the indirect costs of parasitism as parasites often damage or remove host eggs when entering the host nest; surplus eggs may be an essential insurance strategy against this damage. We test these possibilities in the Montezuma Oropendola (Psarocolius Montezuma), a species experiencing high levels of parasitism by Giant Cowbirds (Scaphidura oryzivora) throughout their range. Overall rejection rates of cowbird eggs were high (72%), and experimental addition of parasitic eggs to empty, one-, and two-egg nests demonstrated that recognition success was unaffected by the presence of additional host eggs for comparison. However, the value of surplus eggs when one egg was removed or damaged by a parasite was high; 31.6% of successful two-egg clutches lost a single egg during incubation and would have failed to produce a chick without a second egg. This was directly attributable to parasitism in at least 33% of all cases. Therefore, despite highly developed host defenses against direct costs of parasitism (recognition and removal of parasitic eggs), the associated indirect costs (egg damage and removal) could play an important role in selection for a clutch size that results in more chicks than can be raised

Biological control of the coffee berry borer Hypothenemus hampei (Coleoptera: Curculionidae) by Phymastichus coffea (Hymenoptera: Eulophidae) in Colombia

The potential of the eulophid parasitoid Phymastichus coffea LaSalle to control coffee berry borer Hypothenemus hampei (Ferrari) populations under field conditions in Colombia was evaluated. Parasitoid adults were released one, five and nine days after artificial infestations of 90-, 150- and 210-day-old coffee berries with H. hampei females. The position of the beetle inside the berry and the parasitism levels were assessed ten days after each P. coffea release. Parasitism of H. hampei by P. coffea was significantly affected by the age of the berries at the time of infestation, and by the position of the beetle inside the berries. Highest levels of parasitism were recorded in 150-day-old berries (75-85%) and in 90-day-old berries (75%) when P. coffea were released one day after the artificial infestation with H. hampei. In 150-day-old berries, highest levels of parasitism were recorded for H. hampei found in the outer layer of the endosperm followed by beetles penetrating the exocarp. Increasing the time of P. coffea releases after the artificial infestations with H. hampei led to decreased levels of parasitism in beetles attacking 90- and 150-day-old coffee berries. Low levels of parasitism were recorded in H. hampei females infesting older coffee berries because most of the beetles had already constructed galleries deep in the endosperm of the berries, i.e. out of reach of the parasitoid. The potential of P. coffea for biological control of coffee berry borer in Colombia is discussed.

Does fundamental host range match ecological host range? A retrospective case study of a Lygus plant bug parasitoid

Abstract Using the retrospective case study of Peristenus digoneutis (Hymenoptera: Braconidae) introduced in the United States for biological control of native Lygus plant bugs (Hemiptera: Miridae), laboratory and field studies were conducted in the area of origin to evaluate whether the fundamental host range of P. digoneutis matches its ecological host range. Furthermore, it was determined whether these approaches would have been indicative of the post-introduction host range of P. digoneutis in North America [Day, W.H., 1999. Host preference of introduced and native parasites (Hymenoptera: Braconidae) of phytophagous plant bugs (Hemiptera: Miridae) in alfalfa-grass fields in the north-eastern USA, BioControl 44, 249–261.]. Seven non-target mirid species were selected to define the fundamental host range of P. digoneutis in the area of origin in Europe. Laboratory choice and no-choice tests demonstrated that all selected non-target species were attacked by P. digoneutis and were largely suitable for parasitoid development. To confirm the validity of the fundamental host range, the ecological host range of P. digoneutis in the area of origin was investigated. Peristenus digoneutis was reared from 10 hosts, including three Lygus species and seven non-target hosts from the subfamily Mirinae. Despite the fact that laboratory tests demonstrated a high parasitism level in non-targets, ecological assessments in both North America (Day, 1999) and Europe suggest a much lower impact of P. digoneutis on non-target mirids, with low levels of parasitism (below 1% in Europe). Therefore, ecological host range studies in the area of origin provide useful supplementary data for interpreting pre-release laboratory host range testing.

The biology, damage and within-tree distribution on the spruce bud midge on black spruce in Newfoundland

The spruce bud midge (Rhabdophaga swainei) has one generation a year on black spruce (Picea mariana) in Newfoundland. Newly hatched larvae enter primordia of flushing buds in late June and early July and larvae mature by fall to overwinter within buds. Pupation occurs within buds the following spring and adults emerge in June. Virgin females averaged 86 eggs upon dissection. Platygaster rhabdophagae, Mesopolobus sp., Torymus sp., and Tetrastichus sp. were responsible for high parasitism levels of spruce bud midge larvae. Terminal buds were attacked significantly more than lateral or uppermost lateral buds. The number of infested buds was significantly higher in the top third of the crown than in the bottom crown third, but was not significantly different among north, east, south and west crown exposures. The apical meristem never developed in infested buds, and these buds did not flush. The growth of bud primordial cells is redirected by R. swainei to produce gall tissues that provide nutrients and an overwintering shelter for the larva. Attack of the terminal leader causes a slight loss in height growth but normal leader growth resumes the following year.

Experiments on egg discrimination in two North American corvids: further evidence for retention of egg ejection

In the absence of brood parasitism in North America, black-billed magpies, Pica hudsonia (Sabine, 1822), and yellow-billed magpies, Pica nuttalli (Audubon, 1837), may have retained egg-discrimination behaviour that evolved in Eurasian magpies, Pica pica (L., 1758), in response to parasitism by Old World cuckoos. We further examined this hypothesis by testing the egg-discrimination abilities of black-billed magpies and the American crow, Corvus brachyrhynchos Brehm, 1822, which has no history of brood parasitism. In addition, we tested an alternative hypothesis that black-billed magpies evolved or retained egg discrimination to counter conspecific parasitism by testing their ability to eject foreign conspecific eggs and by using a signal detection model to estimate the level of conspecific parasitism required for ejection to be favoured. Black-billed magpies ejected all non-mimetic eggs and 62% of mimetic eggs. Significantly more mimetic eggs were ejected during the incubation stage than during the laying stage. Magpies ejected significantly more non-mimetic eggs than mimetic eggs overall, but there was no difference in ejection frequency during incubation. American crows ejected 21% of non-mimetic eggs and 8% of mimetic eggs. There was no significant difference in ejection frequency of the two egg types. Black-billed magpies ejected 11% of conspecific eggs and a relatively high level of conspecific parasitism (22%–49%) would be required to select for conspecific ejection, which provides little support for conspecific parasitism as a current selection pressure for maintaining egg discrimination. Thus, black-billed magpies appear to have retained egg rejection in the absence of parasitism through speciation from Eurasian magpies.

Is parasitism of numerically dominant species in macrolepidopteran assemblages independent of their abundance?

Refuge theory proposes that a determinant of species richness (and percent parasitism) is the presence of host refuges. Plant structural refuges are good predictors of species richness for endophytic herbivores, but not for exophytic herbivores. For exophytic herbivores other traits such as relative abundance may provide refuge from parasitism. Using unbiased data on both relative abundance and larval parasitism of species in macrolepidopteran assemblages we tested the null hypothesis that percent parasitism was independent of abundance. Numerically subdominant species do not gain refuge from parasitism by persisting at low abundance. Parasitism was not different from what would be expected based on their numbers. Among numerically dominant species there was, nevertheless, a significant positive association between abundance and parasitism rate. However, dominant herbivores displayed high levels of parasitism even in the years when their abundance was low relative to other years. This suggests that dominant species may possess other traits that enhance their susceptibility to parasitoids. Die Refugien-Theorie schlägt vor, dass eine Determinante der Artenzahl (und der prozentualen Parasitierung) die Verfügbarkeit von Wirtsrefugien ist. Strukturelle pflanzliche Refugien liefern eine gute Vorhersage für die Artenzahl endophytischer Herbivorer, jedoch nicht für exophytische Herbivore. For exophytische Herbivore mögen andere Eigenschaften, wie die relative Abundanz, ein Refugium vor Parasitismus bieten. Unter der Verwendung von erwartungsgetreuen Daten sowohl für die relative Abundanz und als auch die larvale Parasitierung der Arten in makrolepidopteren Ansammlungen untersuchten wir die Null-Hypothese, dass die prozentuale Parasitierung unabhängig von der Abundanz ist. Anzahlmäßig subdominante Arten erreichen kein Refugium vor Parasitismus indem sie bei niedrigen Abundanzen persistieren. Die Parasitierung unterschied sich nicht von der, die aufgrund ihren Anzahlen erwartet würde. Unter den anzahlmäßig dominanten Arten gab es nichtsdestoweniger eine signifikante positive Verbindung zwischen der Abundanz und der Parasitierungsrate. Dennoch wiesen die dominanten Herbivoren sogar in den Jahren, in denen ihre Abundanz im Vergleich zu anderen Jahren gering war, hohe Parasitierungsgrade auf. Dies läßt vermuten, dass dominante Arten andere Eigenschaften besitzen könnten, die ihre Anfälligkeit gegenüber Parasitoiden erhöhen.

Are blackcaps current winners in the evolutionary struggle against the common cuckoo?

Blackcaps Sylvia atricapilla reject artificial cuckoo eggs, and their eggs vary little in appearance within clutches, whereas among clutches eggs vary considerably. Low variation within clutches facilitates discrimination of parasitic eggs, whereas high variation among clutches makes it harder for the cuckoo to mimic the eggs of a certain host species. These traits have most probably evolved as counteradaptations against brood parasitism by the common cuckoo Cuculus canorus, even though blackcaps are not regularly parasitised today. In this study, we investigated how fine-tuned the rejection of parasitic eggs is in this species by introducing three types of eggs into their nests: a real non-mimetic egg the approximate size of a cuckoo egg, an artificial mimetic egg the size of a cuckoo egg and a real conspecific egg. As the rejection frequency of both mimetic and non-mimetic artificial cuckoo eggs has been shown to be high in previous studies, the variation in rejection behaviour between individuals is low, indicating that most individuals within the population are able to reject parasitic eggs. Thus, we predict that (1) the intraclutch variation in egg appearance should be generally low in all individuals, and that (2) regarding conspecific eggs, rejection decisions should be highly dependent on the degree of mimicry between parasitic and host eggs. We found support for these predictions, which indicates that due to their highly sophisticated countermeasures against brood parasitism, blackcaps can probably be regarded as current winners of the arms race with the common cuckoo. Furthermore, the high and consistent rejection frequency of cuckoo eggs found throughout Europe for this species supports the spatial habitat structure hypothesis, which claims that woodland-nesting species breeding near trees, like blackcaps, presumably experienced a high level of parasitism throughout their range in the past and, therefore, their rejection behaviour, once evolved, spread rapidly to all populations.

Superparasitism and sex ratio adjustment in a wasp parasitoid: results at variance with Local Mate Competition?

Anaphes nitens is a solitary parasitoid of the egg capsules of the Eucalyptus snout beetle, Gonipterus scutellatus. Some traits of its natural history suggest that Local Mate Competition (LMC) could account for sex ratio adjustment in this species. We tested whether males emerged early, a prerequisite for fully local mating, and investigated the occurrence and effect of superparasitism on adult size and pre-emergence mortality, factors that might influence sex ratio adjustment. We found in field-collected egg capsules that males emerged first. To investigate the effects of superparasitism on adult size, we compared the sizes of parasitoids that emerged early and late from egg capsules collected in the field, and from egg capsules parasitized and superparasitized in the laboratory. Superparasitism reduced parasitoid size, affecting females more strongly than males, and increased pre-emergence mortality. We estimated A. nitens sex ratio and parasitism rate in the field during 2 years in five localities and during 4 years in a sixth. Following LMC we expected an increase in sex ratio (proportion of males) with increasing parasitism rate (assumed to reflect parasitoid density). We found that sex ratio decreased from 0.38 when the parasitism rate was low (0-20%) to 0.21 when parasitism was high (80-100%). In contrast with field results, a laboratory experiment showed that: (1) at a low parasitism level sex ratio was clearly female biased (0.28+/-0.04), (2) at a high parasitism level sex ratio increased (0.40+/-0.07), (3) male larval survivorship was not lower than female survivorship, and (4) low-quality hosts (i.e. superparasitized) were allocated more males. We conclude that LMC cannot explain the sex ratio adjustment observed in the field, even at low parasitism rates, and alternative explications for highly female-biased sex ratios must be found. One such alternative is female-biased dispersal.

Infection ofFrankliniella fusca(Thysanoptera: Thripidae) in Peanut by the Parasitic NematodeThripinema fuscum(Tylenchidae: Allantonematidae)

Frankliniella fusca (Hinds) is a species of thrips that is a pest of peanuts and an important vector of tomato spotted wilt virus. In previous research, populations of thrips declined in peanut during midseason for unexplained reasons. Nematodes in the genus Thripinema are parasites of thrips that render infected females sterile. A new species, T. fuscum Tipping & Nguyen, was recently described as a parasite of F. fusca in peanut. In 1997 and 1998, the temporal changes in percent parasitism of F. fusca in plots of peanuts were determined. Parasitism of adult female thrips increased from an estimated 1% on seedling peanut each year to a maximum of 68% later in the 1997 growing season and 38% in the 1998 growing season. Treatments of several insecticides for control of thrips reduced percent parasitism of the females on most sample dates in 1997, but parasitism was not significantly affected in 1998. Estimates of the numbers of F. fusca in the flowers and terminal buds of peanuts declined each year as parasitism increased. The very high levels of parasitism in 1997 were associated with near extinction of larval populations of thrips during midseason. As a result, the spread of tomato spotted wilt virus by this vector species was reduced. Thus, T. fuscum may be an important natural enemy of F. fusca responsible for suppression of populations of thrips in peanut.

Trade‐offs in host use by Manduca sexta: plant characters vs natural enemies

There are two principal native host plants for the sphingid moth Manduca sexta L. in south eastern Arizona: Datura wrightii (Solanaceae), and the more recently reported, nonsolanaceous host, Proboscidea parviflora (Martyniaceae). A comparative study on causes and rates of mortality was conducted, since this provided a “natural experiment” for examining potential trade‐offs in host use. The field data identified a dramatic trade‐off between plant quality and predation. D. wrightii appears to provide a high quality food source in growth experiments, and eggs laid on its leaves hatch at high rates. The eggs and larvae, however, underwent extremely high levels of predation and parasitism in the field, and fewer than 0.5% reached the final larval stage. Eggs laid on P. parviflora, on the other hand, suffered low levels of predation and virtually no parasitism, but many eggs did not hatch due to developmental abnormalities induced by the plant, while a large proportion of larvae died after a few days of feeding. Overall, 3% of the eggs reached the final stage on this plant. The maintenance of the two host plants cannot be explained by single factors, but rather by the outcome of multiple factors on the insect fitness, including plant quality, suitability for egg development, predation risk, plant availability and competition with other herbivores. Our data emphasize the importance of predation in shaping host‐plant ranges and support the idea of host‐specific predation rates and “enemy‐free” space.

Strategies for controlling house fly populations resistant to cyromazine

The objectives of this study were to compare, from both biological and economic viewpoints, the impact of various control strategies and evaluate their effect on cyromazine-resistant Musca domestica L., and beneficial house fly pupal parasitoids on caged-layer farms (240,000 hens) in Argentina. The strategies evaluated were: chemical, chemical + cultural, and chemical + cultural + biological (integrated management). The products used were: cyromazine 1% and 50%, DDVP, azamethiphos with and without z-9-tricosene, lime, and the parasitoids Spalangia endius Walker and Muscidifurax raptor Girault & Sanders. In the absence of control measures, fly density increased quickly and the average parasitism rate was 12%. When only chemical control was used, fly populations were reduced to ca. 40/grid and parasitism averaged 2%. When topical cyromazine was used in conjunction with cultural control (lime), fly populations were reduced more rapidly than those treated with cyromazine 1% feed-through. With the subsequent use of parasitic wasps, high parasitism levels were observed and house flies were reduced to tolerance levels in the shortest time. From an economic and biological point of view, the best treatment for house flies resistant to cyromazine was biological + cultural + chemical with localized applications of topical cyromazine.

Population Dynamics of Manure Inhabiting Arthropods Under an Integrated Pest Management (IPM) Program in New York Poultry Facilities—3 Case Studies

Many arthropods inhabit caged-layer poultry manure, including pest and beneficial species. The primary pests are the house fly, Musca domestica L., and the darkling beetle, Alphitobius diaperinus (Panzer). The house fly is ubiquitous and rapidly infests newly accumulating poultry manure, often reaching enormous numbers. Flies pester farm workers, birds, and when emigration occurs, neighbors. The darkling beetle is a pest in older manure, causing damage to building infrastructure and if infested manure is spread onto fields, the beetles can fly in large numbers to nearby neighbors. The beneficial species comprise a mite and a beetle predator and a complex of parasitoid species, all of which can effectively reduce fly populations. In addition, the use of insecticides alone is no longer a viable fly management option. However, recent fly management developments that can easily be used by poultry producers now make a successful fly management program a reality. In this 20-wk study, arthropod populations under an intensive house fly integrated management program (IPM) in three high-rise, caged-layer poultry facilities in New York were monitored. Producers using IPM strategies successfully established the predatory hister beetle, Carcinops pumilio (Erichson), using three release strategies. Predatory mite populations were low throughout the study; however, strategic releases of parasitoids resulted in very high levels of house fly parasitism. Furthermore, the infrequent house fly outbreaks required only minimal insecticide applications. Producers using this IPM program successfully managed house fly populations in their facilities.

Parasitoid diversity and impact on populations of the diamondback moth Plutella xylostella (L.) on Brassica crops in central México

Three experimental plots were established and maintained during one year at two sites in the state of Queretaro, Mexico, in order to identify species of parasitoids attacking the diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae), and to gather information concerning their relative importance and patterns of population fluctuation. At both sites, the plots were planted with broccoli, cabbage and cauliflower during three cropping seasons. Parasitoid species identified were: Diadegma insulare Cresson, Diadromus (= Thyraeella) collaris Gravenhorst (Hymenoptera: Ichneumonidae); Habrobracon sp. (Hymenoptera: Braconidae); Oomyzus (= Tetrastichus) sokolowoskii Kurdjumov (Hymenoptera: Eulophidae); and Spilochalcis (= Conura) sp. (Hymenoptera: Chalcididae). This last species is a hyperparasitoid of D. insulare. The most abundant and frequently occurring species was D. insulare, it occurred in both localities during all three cropping seasons. The highest levels of parasitism caused by D. insulare on DBM were registered in the spring-summer season of 1996 at `La Soledad' farm with averages of 42.7, 45.0 and 44.5% on cabbage, broccoli, and cauliflower, respectively. Because D. insulare was detected attacking the pest at very low population densities during the initial stages of the crop cycle, it is assumed that the parasitoid has a high searching capacity. Correlation (r) between DBM and D. insulare population numbers was positive and significant. The other species identified occurred sporadically and had little impact on pest populations. The identification of D. collaris represents the first record of this species in North America.