Cassava Mealybug Phenacoccus Manihoti Research Articles

A simple PCR‐based method for detecting Anagyrus lopezi (Hymenoptera: Encyrtidae) and Prochiloneurus pulchellus (Hymenoptera: Encyrtidae), primary and hyper parasitoids of the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae)

AbstractEstimating parasitism rates in the field is essential for developing and evaluating biocontrol strategies using parasitoids. In this study, we developed a simple polymerase chain reaction (PCR)‐based method for detecting parasitism of the cassava mealybug Phenacoccus manihoti Matile‐Ferrero (Hemiptera: Pseudococcidae) by the primary parasitoid Anagyrus lopezi De Santis (Hymenoptera: Encyrtidae) and its hyperparasitoid Prochiloneurus pulchellus Silvestri (Hymenoptera: Encyrtidae). Primers were designed to amplify partial cytochrome c oxidase subunit I genes of each species, and their sensitivity was evaluated with mealybugs that had been parasitized by A. lopezi 0, 3, and 6 days earlier, and mummified mealybugs containing A. lopezi pupae that had been parasitized by P. pulchellus 0, 3, 6, 9, and 12 days earlier. The detection rate of parasitism by A. lopezi was 100% for all ages of A. lopezi. The detection rate of parasitism by P. pulchellus ranged from 94.1% to 100%, depending on its developmental stage. For P. pulchellus, template DNA was diluted 10 times before PCR because PCR with the original concentration showed low detection rates, presumably due to the presence of PCR inhibitors. Overall, our primers can be considered sufficiently sensitive to be used for detecting each species.

Susceptibility baselines for the invasive mealybugs Phenacoccus manihoti and Paracoccus marginatus (Hemiptera: Pseudococcidae) in cassava ecosystem against selected neonicotinoid insecticides

In recent years, an invasive cassava mealybug Phenacoccus manihoti has been threatening cassava cultivation alongside another invasive papaya mealybug Paracoccus marginatus which invaded the country more than a decade ago. In order to evaluate their responses against the commonly used neonicotinoid insecticides: thiamethoxam 25 WG and imidacloprid 17.8 SL, acute toxicity experiments to determine the susceptibility baselines in populations of two invasive mealybugs in the cassava agro-ecosystem, namely, cassava mealybug P. manihoti and papaya mealybug P. marginatus were performed upto 15 generations. A systemic uptake method was used for the bioassay. The LC50 values of thiamethoxam for F1 generation were 3.298 ppm whereas it was 1.066 ppm for F15 in cassava mealybug. The LC50 values of F1 generation were 2.014 ppm and that of F15 generation was 1.384 ppm when tested with imidacloprid. In the case of papaya mealybug, the LC50 values ranged from 6.138 ppm (F1) to 2.503 ppm (F15) for thiamethoxam and 7.457 ppm (F1) to 3.231 ppm (F15) for imidacloprid. All the susceptibility indices calculated were less than threefold. The rate of resistance development was negative in all cases showing that none of the tested populations harboured any resistance without insecticidal selection pressure. Tentative discriminating doses were fixed for both chemicals with the help of LC95 values obtained from the bioassay experiments, namely five ppm for both thiamethoxam and imidacloprid in the case of cassava mealybug and 10 ppm and 15 ppm, respectively, for thiamethoxam and imidacloprid in the case of papaya mealybug.

Generalist Predators Shape Biotic Resistance along a Tropical Island Chain.

Islands offer exclusive prisms for an experimental investigation of biodiversity x ecosystem function interplay. Given that species in upper trophic layers, e.g., arthropod predators, experience a comparative disadvantage on small, isolated islands, such settings can help to clarify how predation features within biotic resistance equations. Here, we use observational and manipulative studies on a chain of nine Indonesian islands to quantify predator-mediated biotic resistance against the cassava mealybug Phenacoccus manihoti (Homoptera: Pseudococcidae) and the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae). Across island settings, a diverse set of generalist lacewing, spider and ladybeetle predators aggregates on P. manihoti infested plants, attaining max. (field-level) abundance levels of 1.0, 8.0 and 3.2 individuals per plant, respectively. Though biotic resistance-as imperfectly defined by a predator/prey ratio index-exhibits no inter-island differences, P. manihoti population regulation is primarily provided through an introduced monophagous parasitoid. Meanwhile, resident predators, such as soil-dwelling ants, inflict apparent mortality rates up to 100% for various S. frugiperda life stages, which translates into a 13- to 800-fold lower S. frugiperda survivorship on small versus large islands. While biotic resistance against S. frugiperda is ubiquitous along the island chain, its magnitude differs between island contexts, seasons and ecological realms, i.e., plant canopy vs. soil surface. Hence, under our experimental context, generalist predators determine biotic resistance and exert important levels of mortality even in biodiversity-poor settings. Given the rapid pace of biodiversity loss and alien species accumulation globally, their active conservation in farmland settings (e.g., through pesticide phasedown) is pivotal to ensuring the overall resilience of production ecosystems.

Induction of leaf curling in cassava plants by the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae)

Induction of leaf curling in cassava plants by the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae)

Range of host plants, spatial distribution, and insect predator of Phenacoccus manihoti (Hemiptera: Pseudococcidae) as an emerging pest of cassava plants in Bali, Indonesia

Abstract. Supartha IW, Widaningsih D, Susila IW, Yudha IKW, Utama IWEK, Wiradana PA. 2022. Range of host plants, spatial distribution, and insect predator of Phenacoccus manihoti (Hemiptera: Pseudococcidae) as an emerging pest of cassava plants in Bali. Biodiversitas 23: 3022-3030. The cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae) is a very destructive pest in cassava farming in Indonesia. The insect has already made its way into Indonesia, where it has attacked cassava plants with indications of a bunchy top, which may cause plant death. The objectives of this study were to 1) discover and identify an invasive pest of cassava mealybug pest, P. manihoti, that attacks cassava plants in Bali; 2) map the distribution and abundance of these pest species populations on cassava plants in Bali; 3) describe the structure of the pest population in cassava plantations in Bali; 4) identify the dominant factors that influence the population structure of P. manihoti in Bali, and 5) evaluate the predator fauna in regulating the population. The findings revealed that the mealybug species that attacked cassava in Bali was P. manihoti, an exotic species that had never been published earlier. With a high population abundance, the pest has spread far and effectively overall in regencies/cities in Bali Province. In all regency/city regions, the population structure of P. manihoti was dominated by age groups of instar-1 and two nymphs, with the exception of the Buleleng Regency, which was dominated by age groups of nymphs instar 3 and 4. The nature of polyphagy and cosmopolite features that are readily adaptable to the environment and host plant variables, farming pattern, temperature and rainfall factors were the key factors impacting the population structure of P. manihoti in the field. Cryptolaemus montrouzieri, Chrysoperla carnea, and Scymnus sp. were discovered to have a role in managing P. manihoti populations in the field. The predator fauna community is structurally diverse, abundant, and has a low dominance. Cryptolaemus montrouzieri was the most dominant of the three producer species in the field. These results indicate that there is a positive potential shown by predatory mealybugs in the field and can be used as an initial model by related parties in formulating policies related to controlling insect pests of cassava plants.

Assessing adverse impact of the native biological control disruptors in the colonies of the recent invasive pest Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) in India

New challenges appear with every biological invasion and presses need to probe their ecological interactions. In the comprehensive yet complicated food web associated with the niche of the recently invaded cassava mealybug (CMB) Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae), there was a multitrophic interaction structured vertically as well as horizontally. Altogether 45 species: thirty four species of insects from six orders (Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, and Neuroptera) and eleven species of spiders (Araneae) were grouped under four trophic levels into 11 guilds. The analysis of trophic guild structure and interaction indicated that many indigenous parasitoid species, which qualified to be placed under the fourth trophic level, actively parasitized the potential native predators of cassava mealybug (CMB) and thereby negatively impacted the natural biological control of CMB. Most of these resident hyperparasitoid species were recorded for the first time, to be associated directly or indirectly with CMB. The species diversity at fourth trophic level could be viewed as a bioindicator and one of the most important determinant factors on the success rate of any biological control program. No indigenous primary parasitoids were documented on CMB from any of the sites sampled. In the absence of any indigenous parasitoids and high level of parasitization of the potential CMB predators, the long-term and indirect ecosystem risks will be significant until the introduction and establishment of the proven classical biological control agent, Anagyrus lopezi (De Santis) (Encyrtidae: Hymenoptera) from other countries. • First comprehensive study involving multitrophic interactions in the niche of invasive pest Phenacoccus manihoti. • Many indigenous parasitoid species actively parasitized the potential native predators of CMB. • Negatively impact on the natural biological control of CMB. • No indigenous primary parasitoids documented. • We assess the long-term and indirect ecosystem risks due to CMB and spread to other countries.

Species-specific COI primers for rapid identification of a globally significant invasive pest, the cassava mealybug Phenacoccus manihoti Matile-Ferrero

The globally invasive cassava mealybug Phenacoccus manihoti Matile-Ferrero is a pernicious pest of cassava, and its recent introduction into Asia has raised considerable alarm. To slow or prevent further invasion, an accurate, simple, and developmental-stage-independent detection method for P. manihoti is required. In the present study, a PCR method based on a species-specific mitochondrial DNA cytochrome oxidase I (SS-COI) marker was developed for rapid identification of P. manihoti. One pair of SS-COI primers (PMSSZW-1F and PMSSZW-1R) was designed based on sequence variations in the COI gene among P. manihoti and related mealybug species. Specificity of the primer pair was validated on 21 closely related species. Sensitivity tests were performed on four immature developmental stages and female adults. Efficacy tests demonstrated that at the relatively low concentration of (135.2±14.7) pg μL−1 resuspended DNA, the specific fragment was detected in all replicates. Furthermore, the SS-COI primer pair was assayed on three populations of P. manihoti from major exporting countries of cassava. The PCR assay was proved to be a rapid, simple, and reliable molecular measure for the identification of P. manihoti. This tool will be useful for quarantine, monitoring, and management of this invasive pest.

Biological control of an invasive pest eases pressures on global commodity markets

In an increasingly globalized world, invasive species cause major human, financial, and environmental costs. A cosmopolitan pest of great concern is the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae), which invaded Asia in 2008. Following its arrival, P. manihoti inflicted measurable yield losses and a 27% drop in aggregate cassava production in Thailand. As Thailand is a vital exporter of cassava-derived commodities to China and supplies 36% of the world’s internationally-traded starch, yield shocks triggered price surges and structural changes in global starch trade. In 2009 a biological control agent was introduced in Asia-the host-specific parasitoid, Anagyrus lopezi (Hymenoptera: Encyrtidae). This parasitoid had previously controlled the cassava mealybug in Africa, and its introduction in Asia restored yield levels at a continent-wide scale. Trade network and price time-series analyses reveal how both mealybug-induced production loss and subsequent parasitoid-mediated yield recovery coincided with price fluctuations in futures and spot markets, with important cascading effects on globe-spanning trade networks of (cassava) starch and commodity substitutes. While our analyses may not imply causality, especially given the concurrent 2007–2011 food crises, our results do illuminate the important interconnections among subcomponents of the global commodity system. Our work underlines how ecologically-based tactics support resilience and safeguard primary productivity in (tropical) agro-ecosystems, which in turn help stabilize commodity markets in a similar way as pesticide-centered approaches. Yet, more importantly, (judiciously-implemented) biological control can deliver ample ‘hidden’ environmental and human-health benefits that are not captured by the prices of globally-traded commodities.

Effective biological control of an invasive mealybug pest enhances root yield in cassava

Insects provide critical ecosystem services to humanity, including biological control of pests. Particularly for invasive pests, biological control constitutes an environmentally sound and cost-effective management option. Following its 2008 invasion of Southeast Asia, biological control was implemented against the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae) through the introduction and subsequent release of the host-specific parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) in Thailand. In this study, we quantify yield benefits of mealybug biological control in Thailand’s cassava crop by using two different types of manipulative field trials: i.e., ‘physical exclusion’ cage trials and field-level ‘chemical exclusion’ assays. In cage trials with two popular cassava varieties, root yield and total dry matter (or ‘biological yield’) were a respective 4.0–4.2 times and 3.5–3.9 times higher in the presence of biological control. Extrapolating results from cage trials, biological control thus ensured an approximate yield gain of 5.3–10.0 T/ha for either variety. Under chemical exclusion trials, P. manihoti populations attained levels of 3266 ± 1021 cumulative mealybug-days (CMD) over a 10-month time period, and no longer impact yields. Moreover, under effective P. manihoti control, both root yield and biological yield increased with season-long CMD measures, and pest management interventions-including insecticide sprays-led to notable reductions in yield. This study is the first to show how biological control effectively downgrades the globally invasive P. manihoti to non-economic status and restores yields in Thailand’s cassava crop. Our work emphasizes the economic value of biological control, reveals how current P. manihoti populations do not necessarily cause yield penalties, and underlines the central importance of nature-based approaches in intensifying global agricultural production.

Caught off guard: folk knowledge proves deficient when addressing invasive pests in Asian cassava systems

Farmers’ knowledge, attitudes, and beliefs are of paramount importance in shaping the on-farm adoption and diffusion of integrated pest management (IPM). In particular, for invasive pests, this (gendered) knowledge base can dictate how fast and effective farmers respond to emerging threats. In this study, we employ qualitative and quantitative methods to assess agro-ecological knowledge and pest management behavior of small-scale cassava growers in rural Vietnam and Laos, when faced with two new biotic threats, i.e., the invasive cassava mealybug Phenacoccus manihoti and cassava witches broom disease. Despite their pronounced impact on crop yields, farmers overall had limited knowledge of recent invaders and regularly ascribed their appearance to “climate change". Growers were largely unaware of preventative tactics for pest control, and resorted to curative measures (e.g., unguided pesticide sprays) at the P. manihoti invasion front. Farmers’ attitudes toward invasive pests were highly context- and locality-dependent, and knowledge scores differed between households positioned along a gender continuum. Though women assumed a minor role in IPM decision-making and possessed comparatively deficient knowledge, they favored agro-ecological approaches and took on key tasks in the selection of propagation material. Gender roles in cassava crop protection are equally context-dependent, yet women may be well-positioned to promote IPM practices such as the use of disease-free planting material. Future extension should thus pay attention to (a) strengthening (women) farmers’ knowledge base, to empower them as change agents and drive IPM adoption, and (b) transferring local innovations between sites, eventually through visual educational aids. Given the increasing importance of invasive pests in many developing countries, our work emphasizes how adult education and (adaptive) co-learning should become core components of mitigation programs.

Pengujian kekhususan inang parasitoid Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) pada empat spesies kutu putih yang berasosiasi dengan tanaman singkong

A parasitoid, Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) was introduced from Thailand into Indonesia in early 2014 to control the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae). To determine its potential uses and effect on non-target species, behavioural observation of the parasitoids were made on four species of mealybugs, i.e. P. manihoti, Paracoccus marginatus Williams-Granara de Willink, Pseudococcus jackbeardsleyi Gimpel-Miller, and Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae). For that purposes, a set of tests were conducted which includes host susceptability, preference, and suitability. Tests were conducted by exposing a female parasitoid to 3rd instar nymphs of each mealybug species in a petri dish. For susceptability test, parasitoid A. lopezi encounterend P. manihoti more often (13.70 ± 7.18 visits per 30 minutes) as compared to P. marginatus (985 ± 10.24), P. jackbeardsleyi (6.60 ± 3.62), and F. virgata (5.75 ± 4.09). So did ovipositor probing occurred more on P. manihoti (8.20 ± 5.68 probes per 30 minutes) than on P. marginatus (0.70 ± 1.84), P. jackbeardsleyi (0.35 ± 0.68), and F. virgata (0.10 ± 0.45). For preference test, host encounter and ovipositor probing by the parasitoid were more common on P. manihoti as opposed to other mealybug species. Out of four mealybug species tested, P. manihoti was the only suitable host for parasitoid development, with the number of progenies emerged 7.40 ± 2.17 individuals per 3 female parasitoids exposed in 24 hour. Host specifity exhibited by parasitoid A. lopezi may prevent adverse effect to other mealybug species inhabiting cassava fields.

Environmental Suitability of the Cassava Mealybug Assessments Using Ecological Niche Modelling

The cassava mealybug (Phenacoccus manihoti) is one of the main pests in the world and the risk of invasion posed by this pest is becoming more and more serious with regard to increasing areas of planting cassava in Asia. It is urgent to analyze the potential geography distribution of P. manihoti among cassava in China. In this study, three different ecological modeling methods (Maxent, ENFA and Mahalanobis typicality) were used to predict its potential distribution. The results show that Maxent has the best prediction performance, followed by ENFA, and Mahalanobis typicality has the poorest performance. Based on prediction outcome of Maxent suitable areas of P. manihoti in China are limited in Hainan, Yunnan, Guangxi, Guangdong, Fujian and a few regions of Sichuan, Hunan and Jiangxi. The jackknife analysis indicates that four variables have notable influence on the distribution pattern of P. manihoti, including in in Temperature annual range, Min temperature of coldest month, r, Temperature seasonality and Isothermality.

Erratum to: Infection and colonization of tissues of the aphid Myzus persicae and cassava mealybug Phenacoccus manihoti by the fungus Beauveria bassiana

Histopathogenesis of living insects of Myzus persicae Sulzer (Hemiptera: Aphididae) and Phenacoccus manihoti Matile‐Ferrero (Hemiptera: Pseudococcidae) by Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) was monitored from penetration through insect death. Important events in aphids included fungal penetration of the integument of the less-resistant leg intersegmental membrane and invasion of natural openings, formation of hyphal bodies in live aphids by three days post-inoculation (PI), and extensive hyphal colonization of the two leg segments closest to the insect body at death of the aphids. Confocal microscopy of green fluorescent protein-labeled B. bassiana in live mealybugs indicated the fungus penetrated the host through the legs and mouthparts. The fungus was scarce in live mealybugs at 1–5 days PI, formed hyphal bodies by six days PI, and growth was limited to parts of dead hosts at 6–7 days PI. In dead mealybugs, hyphal bodies were near solid tissue. Blastospores were in the hemolymph.

Infection and colonization of tissues of the aphid Myzus persicae and cassava mealybug Phenacoccus manihoti by the fungus Beauveria bassiana

Infection and colonization of tissues of the aphid Myzus persicae and cassava mealybug Phenacoccus manihoti by the fungus Beauveria bassiana

Prey Habitat Location by the Cassava Mealybug Predator Exochomus flaviventris: Olfactory Responses to Odor of Plant, Mealybug, Plant–Mealybug Complex, and Plant–Mealybug–Natural Enemy Complex

Exochomus flaviventris Mader is considered to be the most active predator of the cassava mealybug Phenacoccus manihoti Matile–Ferrero in Central Africa. The response of experienced gravid female coccinellids to the odor of cassava plant (var. Zanaga), unparasitized mealybugs, plant–mealybug complex with or without feeding prey (parasitized or not), and plant–mealybug complex with or without conspecific coccinellids was investigated in a Y-tube olfactometer. The odor of uninfested cassava plants was not more attractive than clean air. Dual-choice tests revealed that mealybug-infested plants were preferred to mealybugs alone and mealybug-damaged plants and were the major sources of volatiles that attract females coccinellids to the microhabitat of its prey. The emission of volatile chemicals did not appear to be limited to the infested parts of the plant but did occur systemically throughout the plant. The presence of conspecific coccinellid larvae or adult males did not modify the attractiveness of the mealybug-infested plants. However, when an infested plant with conspecific predator females (alone or with conspecific males) was compared to an infested plant or infested plant with conspecific males, E. flaviventris females showed a preference for the last two sources of odor. The uninfested plant with conspecific males was also preferred to the uninfested plant with conspecific females. In addition, the odor of conspecific males was preferred over that of conspecific females. Female predators preferred the plant infested with unparasitized mealybugs over the plant infested with mealybugs previously parasitized. These results showed that E. flaviventris females use herbivore-induced plant volatiles during foraging and can detect via olfaction the presence of conspecific gravid females and parasitized prey, thus assessing patch suitability from a distance.

Economics of biological control of cassava mealybug in Africa

Abstract Pest populations of the cassava mealybug Phenacoccus manihoti Mat.-Ferr. (Homoptera: Pseudococcidae) were reduced successfully by the biological control agent Apoanagyrus (Epidinocarsis) lopezi De Santis (Hymenoptera: Encyrtidae) throughout most of sub-Saharan Africa. The economics of the project were evaluated based on data from field trials, socio-economic surveys, published results, and financial information provided by the International Institute of Tropical Agriculture (IITA) and the national programmes. Costs and benefits for the biological control of P. manihoti were calculated over 40 years (1974–2013) for 27 African countries, for four different scenarios, taking into account that impact by A. lopezi and speed of the impact differ between ecological zones. A reasonable calculation considering compounded interest resulted in a benefit cost ratio of about 200 when cassava was costed at world market prices, and of about 370–740 when inter-African prices were considered.

Olfactory Responses of Parasitoid Apoanagyrus lopezi to Odor of Plants, Mealybugs, and Plant–Mealybug Complexes

Apoanagyrus (Epidinocarsis) lopezi De Santis is an endoparasitoid used in the biological control of the cassava mealybug Phenacoccus manihoti Matile-Ferrero in Africa. The response of naive and mated females of A. lopezi to odors from cassava plant (var. Zanaga), parasitized or unparasitized mealybugs, and plant–mealybug host complexes with or without feeding hosts was investigated in a Y-tube olfactometer. Dual-choice tests revealed that mealybug-infested plants and mealybug-damaged plants were the major sources of volatiles that attract female parasitoids to the microhabitat of its hosts. The emission of volatile chemicals appears not to be limited to the infested plant part but to occur systemically throughout the plant. On their own, unparasitized mealybugs were more attractive than uninfested plants or parasitized mealybugs alone. Parasitization of P. manihoti by A. lopezi decreased the response of parasitoids to mealybugs or mealybug–plant complexes. Plants infested with unparasitized hosts attracted more female parasitoids than plants infested with parasitized mealybugs. These results indicate that, in the long-range host-searching process, females of A. lopezi respond mainly to mealybug-induced synomones, and specific host-derived cues play a minor role.

Comparative life table statistics of Apoanagyrus lopezi reared on the cassava mealybug Phenacoccus manihoti fed on four host plants

AbstractThe demographic statistics of Apoanagyrus lopezi De Santis (Hymenoptera: Encyrtidae) were studied in the laboratory on its host, the cassava mealybug Phenacoccus manihoti Matile‐Ferrero (Homoptera: Pseudococcidae), reared on four host plants characterized by different levels of antibiotic resistance to the mealybug: two cassava varieties, Incoza and Zanaga (Manihot esculenta Crantz: Euphorbiaceae), the faux‐caoutchouc (hybrid of M. esculenta×M. glaziovii Muel. Arg.) and Talinum (Talinum triangulare Jack:Portulacaceae).Total and daily mean fecundities of female parasitoids were strongly influenced by the host plant but there was no link with antibiotic resistance. The mean duration of the oviposition period was also significantly modified by the host plant and was again not correlated to the level of antibiotic resistance. Net reproduction rates of female parasitoids were nearly 2 times higher on hosts fed on Zanaga and Talinum than on Incoza and Faux‐caoutchouc, and were not related to the total fecundities. The generation time was significantly longer on Faux‐caoutchouc than on the other three plants. The intrinsic rate of increase varied significantly with host plants and was higher on Talinum and Zanaga than on Incoza and Faux‐caoutchouc. With the varieties of cassava, Incoza and Zanaga, it was observed that antibiosis had a significant negative effect on the survival of A. lopezi, which would influence the effectiveness of the parasitoid.

Effect of host plants on fecundity and development of Apoanagyrus lopezi, an endoparasitoid of the cassava mealybug Phenacoccus manihoti

Apoanagyrus (Epidinocarsis) lopezi (De Santis) (Hymenoptera: Encyrtidae) is a solitary parasitoid indigenous to South America, that was introduced to subsaharan Africa in 1981 as a biological control agent against the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Hemiptera; Pseudococcidae), a pest of cassava, Manihot esculenta Crantz, (Euphorbiaceae). These cassava-mealybug and mealybug-parasitoid systems have been studied extensively, both in the laboratory and under field conditions (Fabres, 1981; Lohr et al., 1988; Le Ru & Tertuliano, 1993). Laboratory evaluations of cassava antibiosis resistance,made by estimating the intrinsic capacity for increase rc, showed that the host plant has an important effect on the multiplying capacity of the mealybug (Tertuliano et al., 1993). Data are still lacking on tritrophic aspects of cassava mealybugs and there is no information on interactions between resistant cassava cultivars and A. lopezi. We conducted laboratory experiments to investigate the influence of four host plants previously characterized by different resistance levels of antibiosis to P. manihoti on the oviposition pattern, longevity, fecundity, survival and development time of A. lopezi. These are five important qualities of a parasitoid that influence its efficiency.

Influence de la linamarine dans la relation manioc-cochenille

Summary Cassava Manihot esculenta Crantz (Euphorbiaceae) is distinguished by the presence of Cyanid compounds in leaves, stems and tubers. In plant's tissues,—CN group is linked with D—glucose to form cyanogenic glucosides: mainly linamarin. In Congo, the cassava mealybug Phenacoccus manihoti Matile—Ferrero (Homoptera: Pseudococcidae) is the major pest of cassava. This insect is living mainly on genus Manihot. This oligophagy of P. manihoti towards cassava suggests that the mealybug is adapted to secondary compounds of its host plant, and more particularly to linamarin. This specialization supposes the presence of an enzymatical fittings adjusted. In fact, our results shows that this insect has a linamarase (participating in hydolysis of linamarin), an endogenous and an inductive enzyme in cassava mealybug. As other insects, P. manihoti has an enzymatical fittings hydolysing linamarin. In this insect, the use of hydolysis products is discussed.