Note on the natural enemies ofPsylla hyalina [Homoptera: Psyllidae] onAlbizia lebbeck

A survey of the natural enemies associated withPsylla hyalina infestingAlbizia lebbeck has revealed 2 primary parasitoids, 1 hyperparasitoid, 5 coccinellids, 1 lygaeid and 3 fungal pathogens, all being new records forP. hyalina.      

Larval parasitoids and pathogens of the groundnut leaf miner,Aproaerema modicella (Lep.: Gelechiidae), in India

Natural enemies of the groundnut leaf miner,Aproaerema modicella (Deventer), were studied at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) located near Hyderabad in peninsular India. Hymenopterous parasitoids attacking leaf miner larvae were the most important group of natural enemies. Nine primary and eight secondary parasitoids emerged from host larvae, and killed up to 50% of the leaf miner larvae sampled. The trophic relationships between primary and secondary parasitoids are incompletely understood. The influence of pathogens of this species is reported for the first time. These pathogens killed up to 30% of the leaf miner larvae. The combined effects of all mortality agents killed up to 95% of the leaf miner larvae per sample period. However, use of insecticides in sprayed plots reduced the efficacy of parasitoids. The impact of predators on larval populations was not studied and may explain underestimates of leaf miner mortality rates.      

Natural enemies of the pumpkin caterpillarDiaphania indica [Lepidoptera: Pyralidae] in Tamil Nadu

The survey for the natural enemies associated with the pumpkin caterpillar,Diaphania indica revealed the presence of 20 species of parasitoids, predators and pathogens. Of these, 16 were parasitoids belonging to the familiesBraconidae, Ichneumonidae, Bethylidae, Elasmidae andChalcididae. Except for 3 species the remaining parasitoids were new records forD. indica. The predators recorded were ants and spiders. A microsporidia also was recorded for the first time onD. indica.      

Landscape complexity differentially benefits generalized fourth,over specialized third,trophic level natural enemies

The differential loss of higher trophic levels in the face of natural habitat loss can result in the disruption of important trophic interactions, such as biological control. Natural enemies of herbivorous pests in cropping systems often benefit from the presence of natural habitats in surrounding landscapes, as they provide key resources such as alternative hosts. However, any benefits from a biological control perspective may be dampened if this also enhances enemies at the fourth trophic level. Remarkably, studies of the influence of landscape structure on diversity and interactions of fourth trophic‐level natural enemies are largely lacking. We carried out a large‐scale sampling study to investigate the effects of landscape complexity (i.e. the proportion of non‐crop habitat in the landscapes surrounding focal study areas) on the parasitoid communities of aphids in wheat and on an abundant extra‐field plant, stinging nettle. Primary parasitoid communities (3rd trophic level) attacking the cereal aphid, Sitobion avenae, had little overlap with the communities attacking the nettle aphid, Microlophium carnosum, while secondary parasitoids (4th trophic level) showed high levels of species overlap across these two aphids (25 vs 73% shared species respectively), resulting in significantly higher linkage density and lower specialization for secondary than primary parasitoid webs. In wheat, parasitoid diversity was not related to landscape complexity for either primary or secondary parasitoids. Rates of primary parasitism were generally low, while secondary parasitism rates were high (37–94%) and increased significantly with increasing landscape complexity, although this pattern was driven by a single secondary parasitoid species. Overall, our results demonstrate that extra‐field habitats and landscape complexity can differentially benefit fourth, over third, trophic level natural enemies, and thereby, could dampen biological control. Our results further suggest that fourth trophic‐level enemies may play an important, yet understudied, role in linking insect population dynamics across habitat types.     

Parasitoids associated with the common pistachio psylla, Agonoscena pistaciae, in Iran

The parasitoids associated with the common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer, were investigated at three pistachio plantations in Rafsanjan, Iran. Of the 6504 wasps emerging from mummified psyllids, 46% were the primary parasitoid Psyllaephagus pistaciae Ferrière, and the remaining 54% represented six species of hymenopterous hyperparasitoids, including Chartocerus kurdjumovi (Nikol’skaja), Marietta picta (André), Pachyneuron aphidis (Bouché), Pachyneuron muscarum (Linnaeus), Psyllaphycus diaphorinae (Hayat), and Syrphophagus aphidivorus (Mayr). Lysiphlebus fabarum Marshall, the parasitoid of Aphis gossypii Glover and Aphis craccivora Koch present on weeds, was found to be an alternative host for three major hyperparasitoids of A. pistaciae. The most abundant hyperparasitoid was S. aphidivorus, appearing during the growing season in all trial locations on psyllids and aphids in pistachio orchards. The weed-infesting aphids, along with their primary parasitoid, can act as a reservoir of A. pistaciae secondary parasitoids. Therefore, parasitized aphids allow populations of secondary parasitoids to increase and consequently to apply higher pressure on P. pistaciae. We detected that two primary parasitoid species, including P. pistaciae and L. fabarum, attacking different species of hosts interact indirectly through shared secondary parasitism. It is suggested that the community structure of A. pistaciae may be influenced by apparent competition, although more work is needed to provide firm evidence.     

The role of natural enemy guilds in Aphis glycines suppression

Generalist natural enemy guilds are increasingly recognized as important sources of mortality for invasive agricultural pests. However, the net contribution of different species to pest suppression is conditioned by their biology and interspecific interactions. The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is widely attacked by generalist predators, but the relative impacts of different natural enemy guilds remains poorly understood. Moreover, low levels of A. glycines parasitism suggest that resident parasitoids may be limited through intraguild predation. During 2004 and 2005, we conducted field experiments to test the impact of different guilds of natural enemies on A. glycines. We contrasted aphid abundance on field cages with ambient levels of small predators (primarily Orius insidiosus) and parasitoids (primarily Braconidae), sham cages and open controls exposed to large predators (primarily coccinellids), and cages excluding all natural enemies. We observed strong aphid suppression (86- to 36-fold reduction) in treatments exposed to coccinellids, but only minor reduction due to small predators and parasitoids, with aphids reaching rapidly economic injury levels when coccinellids were excluded. Three species of resident parasitoids were found attacking A. glycines at very low levels (<1% parasitism), with no evidence that intraguild predation by coccinellids attenuated parasitoid impacts. At the plant level, coccinellid impacts resulted in a trophic cascade that restored soybean biomass and yield, whereas small natural enemies provided only minor protection against yield loss. Our results indicate that within the assemblage of A. glycines natural enemies in Michigan, coccinellids are critical to maintain aphids below economic injury levels.     

Evaluation of the impact of natural enemies on Plutella xylostella L. (Lepidoptera: Yponomeutidae) populations on commercial Brassica farms

Abstract 1 Accurate assessment of the impact of natural enemies on pest populations is fundamental to the design of robust integrated pest management programmes. In most situations, diseases, predators and parasitoids act contemporaneously on insect pest populations and the impact of individual natural enemies, or specific groups of natural enemies, is difficult to interpret. These problems are exacerbated in agro‐ecosystems that are frequently disrupted by the application of insecticides. 2 A combination of life‐table and natural enemy exclusion techniques was utilized to develop a method for the assessment of the impact of endemic natural enemies on Plutella xylostella populations on commercial Brassica farms. 3 At two of the experimental sites, natural enemies had no impact on P. xylostella survival, at two other sites, natural enemy impact was low but, at a fifth site, natural enemies drastically reduced the P. xylostella population. 4 The calculation of marginal death rates and associated k‐values allowed the comparison of mortality factors between experimental sites, and indicated that larval disappearance was consistently the most important mortality factor, followed by egg disappearance, larval parasitism and pupal parasitism. The appropriateness of the methods and assumptions made to calculate the marginal death rates are discussed. 5 The technique represents a robust and easily repeatable method for the analysis of the activity of natural enemies of P. xylostella, which could be adapted for the study of other phytophagous pests.     

First report of the fall armyworm,Spodoptera frugiperda (Lepidoptera: Noctuidae), natural enemies from Africa

The fall armyworm (FAW), Spodoptera frugiperda, is a major pest of maize in North and South America. It was first reported from Africa in 2016 and currently established as a major invasive pest of maize. A survey was conducted to explore for natural enemies of the fall armyworm in Ethiopia, Kenya and Tanzania in 2017. Smallholder maize farms were randomly selected and surveyed in the three countries. Five different species of parasitoids were recovered from fall armyworm eggs and larvae, including four within the Hymenoptera and one Dipteran. These species are new associations with FAW and were never reported before from Africa, North and South America. In Ethiopia, Cotesia icipe was the dominant larval parasitoid with parasitism ranging from 33.8% to 45.3%, while in Kenya, the tachinid fly, Palexorista zonata, was the primary parasitoid with 12.5% parasitism. Charops ater and Coccygidium luteum were the most common parasitoids in Kenya and Tanzania with parasitism ranging from 6 to 12%, and 4 to 8.3%, respectively. Although fall armyworm has rapidly spread throughout these three countries, we were encouraged to see a reasonable level of biological control in place. This study is of paramount importance in designing a biological control program for fall armyworm, either through conservation of native natural enemies or augmentative release.     

Defensive Behavior in Primary- and Secondary-Host Generations of the Soldier-Producing Aphid, Pemphigus bursarius (Hemiptera: Aphididae)

The genus Pemphigus comprises several species that produce soldiers (defensive morphs) in galls on the primary host. At the moment, it is unclear if host-alternating species also produce defenders on their secondary host. We therefore examined how P. bursarius morphs of the secondary host generations respond to predators to test whether they show defensive behavior. We further examined how this response compares with the antipredator behavior of soldiers in P. bursarius and P. spyrothecae occurring on the primary host. We performed two manipulative experiments using two predatory species to quantify the behavior of the different morphs in response to predators. In both experiments, secondary host morphs of P. bursarius showed no attacking behavior and antipredator behavior in these morphs was limited to escaping natural enemies by walking away. In contrast, the first instars of the primary host generations in both Pemphigus species showed attacking behavior and were capable of killing the predators.     

Occurrence and direct control potential of parasitoids and predators of the fall armyworm (Lepidoptera: Noctuidae) on maize in the subtropical lowlands of Mexico

Abstract 1 Native natural enemies have the potential to control fall armyworm Spodoptera frugiperda (Smith) in tropical maize grown in Mexico, where this insect pest causes severe economic losses to farmers. It has been proposed that enhancing herbivore‐induced volatile emissions in maize plants may help to increase the effectiveness of natural enemies, which use these volatiles to locate their prey. This will only be of immediate benefit to farmers if the activity of the natural enemies results in a direct reduction in herbivory. Here we report on field surveys for the most common natural enemies in a tropical maize‐growing region in Mexico and the potential effects of these enemies on herbivory by fall armyworm. 2 Caterpillars were collected in maize fields near Poza Rica in the state of Veracruz during January and February 1999, 2000 and 2001. Plants were either naturally infested by S. frugiperda, or artificially infested with laboratory‐reared larvae. Ten species of parasitoids emerged from the collected larvae and eight species of predators that are known to feed on larvae and eggs were observed on the plants. Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae) was the dominant parasitoid species, in 1999 and 2001. 3 Of the nine larval parasitoids collected, six (all solitary) are known to reduce herbivory, whereas one causes the host to eat more (for two species this is not known). This implies that enhancing the effectiveness of solitary endoparasitoids may benefit subsistence farmers in developing countries by immediately reducing herbivory. The overall benefit for the plant resulting from parasitoid activity also has important implications for the evolutionary role of parasitoids in contributing to selection pressures that shape indirect defences in plants.     

A reappraisal of the population dynamics of the pine beauty moth, Panolis flammea, on lodgepole pine, Pinus contorta, in Scotland

The pine beauty moth, Panolis flammea, is a defoliating pest of lodgepole pine (Pinus contorta) forests in Scotland. This article reviews early and recent research on the population ecology of Panolis flammea and presents an analysis of pupal survey data collected between 1977 and 1993. Research in the 1980s suggested that natural enemies, although effective in preventing P. flammea outbreaks on Scots pine (Pinus sylvestris), played an insignificant role in the population dynamics of P. flammea on lodgepole pine. However, analysis of pupal survey data showed that delayed density-dependent action of natural enemies, probably parasitoids, was overlooked during the 1970s and 1980s. Recent research suggests that fungal pathogens are responsible for a decline in the frequency and severity of outbreaks of P. flammea on lodgepole pine. This suggestion, together with the overlooked importance of other natural enemies, indicates that the population ecology of P. flammea in Scotland has changed during the past 20 years and requires a full reappraisal. Received: May 31, 1999 / Accepted: August 18, 1999     

Interactions between the ant Tapinoma nigerrimum (Hymenoptera: Formicidae) and the main natural enemies of the vine and citrus mealybugs (Hemiptera: Pseudococcidae)

Honeydew-excreting hemipterans, such as mealybug pests, can be protected from their natural enemies by tending ants in return for honeydew, thereby compromising the aims of biological control. In this respect, antagonistic interactions between the ant Tapinoma nigerrimum, native to the Mediterranean basin, and the main natural enemies of both the vine mealybug (VMB), Planococcus ficus, and the citrus mealybug (CM), Planococcus citri, were assessed in laboratory conditions. Parasitism of vine and CMs by their respective parasitoids, Anagyrus sp. nr. pseudococci and Leptomastix dactylopii, was negatively affected by the ant T. nigerrimum. Similarly, T. nigerrimum was shown to significantly disrupt the predatory potential of ladybird larvae, Cryptolaemus montrouzieri, when foraging on host CMs. By contrast, the presence of the ant did not negatively influence the predatory activity of C. montrouzieri adults when feeding on CMs. Consequently, the encyrtid parasitoids A. sp. nr. pseudococci and L. dactylopii and the larval stage of the predator C. montrouzieri may be considered as T. nigerrimum-sensitive, whereas the adults of C. montrouzieri may be regarded as T. nigerrimum-resistant predators. Accordingly, the ant T. nigerrimum constitutes a threat to the biological control of mealybugs by either the encyrtids A. sp. nr. pseudococci and L. dactylopii or the larval stage of the ladybird C. montrouzieri. Hence, adequate control of T. nigerrimum is highly recommended before any release of these mealybugs' natural enemies.     

Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica

Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects on other Aleyrodidae or their natural enemies. Handling Editor: Dirk Babendreier.     

Hymenopterous parasitoids of bark beetles [Scolytidae] in Israel: Host relation,host plant,abundance and seasonal history

Twenty six species of parasitoids were recorded from 15 species of bark beetles in Israel. Parasitoids were collected from infested cut branches of broadleaves and trap-trees of pine and cypress. Most of the parasitoids are oligophagous and range fromEcphylus caudatus, a monophagous species exclusive toHypoborus ficus, toHeydenia pretiosa, which develops on 11 species.Scleroderma domesticus, Agrilocida ferrieri andEupelmus nearurozonus are occasional parasitoids of bark beetles.Cephalonomia hypobori, Israelius carthami, S. domesticus, Entedon ergias, Cerocephala eccoptogasteri andRoptocerus xylophagorum are cryptoparasitoids and search for their host in the galleries. Known parasitoids are listed from 15 tree genera belonging to 8 botanical families. A typical range for the common parasitoids is presented with within-tree distribution of pine parasitoids. Relatively monophagous species are usually dominant parasitoids in a specific beetle population, whereas relatively polyphagous parasitoids vary in abundance among different host populations.Calosota spp., 2Eurytoma spp. andDendrosoter hartigii are usually present in small numbers. Information concerning the seasonal history of the parasitoids suggests that the major species may raise about 5 to 7 annual generations. Contribution from the Agricultural Research Organization, Bet Dagan, Israel N^o 1331-E, 1984 series     

Host plants and natural enemies of Bemisia tabaci (Hemiptera: Aleyrodidae) in China

Abstract The sweetpotato whitefly, Bemisia tabaci, has been a destructive pest in China for over the past two decades. It is an extremely polyphagous insect, being recorded feeding on hundreds of host plants around the world. Potential host plants and natural enemies of B. tabaci in the south, southeast, middle, north and northwest of China were investigated during the last decade. In total 361 plant species from 89 families were recorded in our surveys. Plants in the families Compositae, Cruciferae, Cucurbitaceae, Solanaceae and Leguminosae were the preferred host species for B. tabaci, which therefore suffered much damage from this devastating pest due to their high populations. In total, 56 species of parasitoids, 54 species of arthropod predators and seven species of entomopathogenic fungi were recorded in our surveys. Aphelinid parasitoids from Encarsia and Eretmocerus genera, lady beetles and lacewings in Coleoptera and Neuroptera were found to be the dominant arthropod predators of B. tabaci in China. The varieties of host plant, their distribution and the dominant species of natural enemies of B. tabaci in different regions of China are discussed.     

Impact of natural enemies on <Emphasis Type="Italic">Obolodiplosis robiniae</Emphasis> invasion

The gall midge Obolodiplosis robiniae is a pest of black locust Robinia pseudoacacia. The species was recently introduced into Europe and it is nowadays a usual insect in Slovakia, where two-year field surveys were undertaken during 2007–2008. The main objective of this study was to determine the natural enemies attacking O. robiniae and estimate their influence on midge population, less than 3 years after its introduction. Eight parasitoids and bushcricket Tettigonia viridissima were responsible for midge regulation. The parasitoid complex was not typically that of an introduced species as it was predicted. Firstly, the midge was heavily influenced by a specialized parasitoid Platygaster robiniae, which was a predominant parasitoid and accounted for 98% of all specimens reared. Secondly, annual larval parasitism varied from 5.4 to 10.8%, though the late season average parasitism achieved 26.0% and often exceeded 40%. P. robiniae was also very efficient in exploiting galls and was capable of consistently regulating midge population. The surveys demonstrated that the average cumulative impact of natural enemies on the midge was substantial. Stably around 20% of attacked galls were recorded during the late summer. Bushcrickets were as efficient as parasitoids and played an important role at control, especially during lack of parasitoids. Greater impact of parasitoids was found in the larger settlements than it was in the countryside, when countertendency was valid for bushcrickets. There is an indication that O. robiniae parasitized by specialized parasitoid, and attacked by bushcrickets represents only a moderate risk for R. pseudoacacia or forest stands.     

The natural enemies of Bemisia argentifolii in Martinique

An eight year survey wasconducted in Martinique on vegetable crops andweeds to develop a list of the natural enemiesof the whitefly Bemisia argentifoliiBellows and Perring. More than fifteen speciesof predators and parasitoids were found as wellas one entomopathogenic fungus (Paecilomyces sp.). The primary predators wereladybirds (Delphastus pusillus and D. pallidus) and bugs (Nesidiocoris tenuis, Macrolophus cf. caliginosus, Orius insidiosus). The mostcommon parasitoids were Eretmocerustejanus, Encarsia luteola, E. nigricephala, E. transvena and Amitus bennetti. Observations on the biologyand distribution of these natural enemies are provided.     

Phytoseiid mites (Acari: Mesostigmata) associated with tea gardens in north of Iran

Predator mites of Phytoseiidae family are among the most important biocontrol agents in the world. These beneficial mites are considered as natural enemies of many pests and herbivore mites, and can feed on different growth stages of pests (egg, larva or nymph). Five species of Phytoseiidae mites were found during a survey conducted on tea plants, Camellia sinensis (Theaceae), in the Mazandaran and Guilan Provinces in the north of Iran, on the coast of the Caspian Sea, the major tea-growing region of Iran. Some of these species are recorded for the first time in tea gardens of Iran.     

Extended larval development time for aphid parasitoids in the presence of plant endosymbionts

Abstract 1. Variation in plant chemistry does not only mediate interactions between plants and herbivores but also those between herbivores and their natural enemies, and plants and natural enemies. 2. Endophytic fungi complete their whole life cycle within the host plant’s tissue and are associated with a large diversity of plant species. Endophytes of the genus Neotyphodium alter the chemistry of the host plant by producing herbivore toxic alkaloids. 3. Here we asked whether the endophyte‐tolerant aphid species Metopolophium festucae could be defended against its parasitoid Aphidius ervi when feeding on endophyte‐infected plants. In a laboratory experiment, we compared life‐history traits of A. ervi when exposed to hosts on endophyte‐infected or endophyte‐free Lolium perenne. 4. The presence of endophytes significantly increased larval and pupal development times, but did not affect the mortality of immature parasitoids or the longevity of the adults. Although the number of parasitoid mummies tended to be reduced on endophyte‐infected plants, the number of emerging parasitoids did not differ significantly between the two treatments. 5. This shows that the metabolism of individual aphids feeding on infected plants may be changed and help in the defence against parasitoids. An increase in parasitoid development time should ultimately reduce the population growth of A. ervi. Therefore, endophyte presence may represent an advantage for endophyte‐tolerant aphid species through extended parasitoid development and its effect on parasitoid population dynamics.     

The spitting image of plant defenses: Effects of plant secondary chemistry on the efficacy of caterpillar regurgitant as an anti‐predator defense

In the arms race between plants, herbivores, and their natural enemies, specialized herbivores may use plant defenses for their own benefit, and variation in plant traits may affect the benefits that herbivores derive from these defenses. Pieris brassicae is a specialist herbivore of plants containing glucosinolates, a specific class of defensive secondary metabolites. Caterpillars of P. brassicae are known to actively spit on attacking natural enemies, including their main parasitoid, the braconid wasp Cotesia glomerata. Here, we tested the hypothesis that variation in the secondary metabolites of host plants affects the efficacy of caterpillar regurgitant as an anti‐predator defense. Using a total of 10 host plants with different glucosinolate profiles, we first studied natural regurgitation events of caterpillars on parasitoids. We then studied manual applications of water or regurgitant on parasitoids during parasitization events. Results from natural regurgitation events revealed that parasitoids spent more time grooming after attack when foraging on radish and nasturtium than on Brassica spp., and when the regurgitant came in contact with the wings rather than any other body part. Results from manual applications of regurgitant showed that all parameters of parasitoid behavior (initial attack duration, attack interruption, grooming time, and likelihood of a second attack) were more affected when regurgitant was applied rather than water. The proportion of parasitoids re‐attacking a caterpillar within 15 min was the lowest when regurgitant originated from radish‐fed caterpillars. However, we found no correlation between glucosinolate content and regurgitant effects, and parasitoid behavior was equally affected when regurgitant originated from a glucosinolate‐deficient Arabidopsis thaliana mutant line. In conclusion, host plant affects to a certain extent the efficacy of spit from P. brassicae caterpillars as a defense against parasitoids, but this is not due to glucosinolate content. The nature of the defensive compounds present in the spit remains to be determined, and the ecological relevance of this anti‐predator defense needs to be further evaluated in the field.