Cent Parasitism Research Articles

Evaluation of Aphytis melinus De Bach (Hymenoptera: Chalcidoidea: Aphelinidae) in Citrus Orchards as a Biocontrol Agent of Black Scale, Parlatoria ziziphi (Lucas) (Hemiptera: Coccoidea: Diaspididae) in Egypt

The black parlatoria scale, Parlatoria ziziphi (Lucas) (Coccoidea: Diaspididae), is one of the most important pests attacking citrus trees in different parts of the world including Egypt. This work deals with rearing, release and evaluation of the parasitoid, Aphytis melinus De Bach (Hymenoptera: Aphelinidae) to control P. ziziphi biologically. In all, 250000 adult parasitoid individuals were released monthly on citrus at five locations in Cairo, Giza and Qalyubiya governorates during 2006 and 2007. At Heliopolis (Cairo), where A. melinus was present prior to the augmentative release, the per cent parasitism in the control block was 15 and 75% while it was 73 and 87% in the treatment block during the two years under consideration. At Dokki (Giza) also, A. melinus was present prior to the augmentative releases and the peak of parasitism reached 18 and 82% in the control block, compared to 86 and 91% in the treatment block. At El-Qanater El-Khriya and Tukh in Qalyubiya, A. melinus was present prior to the augmentative releases. In El-Qanater El-Khriya, the peak of parasitism reached 41 and 67% in the treatment block, compared to 8 and 46% in the control block. In Tukh, the peak of parasitism reached 31 and 65% in the treatment block, compared to 4 and 35% in the check block. At Qalub, where the parasitoid was not present prior to the augmentative releases, the peak of parasitism reached 22 and 36% in the treatment block, compared to 0 and 22% in the control block during the two years, respectively.

Genetic Improvement of Egg Parasitoid Trichogramma chilonis Ishii for Combined Tolerance to Multiple Insecticides and High Temperature

A strain of Trichogramma chilonis Ishii, an effective parasitoid of lepidopteran pests was developed for tolerance to three major groups of insecticides, i. e., endosulfan (organochlorine), monocrotophos (organophosphate) and fenvalerate (synthetic pyrethroid) and to high temperature (32-38°C) through selection. After 81 generations of selection, there was an increase in parasitism from 35% to 90-95% and decrease in mortality from 100% to 57-70% after 6h of constant exposure to three insecticides and high temperature. Interestingly 46.8 and 2.9 fold increase in tolerance was observed in males compared to 18.5 and 1.3 fold increase in females of MITT (multiple-insecticide and temperature tolerant) strain when exposed to endosulfan and fenvalerate sprays, respectively, while in case of monocrotophos, females and males were 465-fold and 25-fold more tolerant, respectively, than susceptible strain. At higher temperatures of 40 and 45°C, the per cent mortality of tolerant adults was 0.0 and 9.2%, respectively, compared to 59.7 and 96.1% in susceptible population after 6h of exposure at these temperatures. At high variable temperature (32-38°C), per cent mortality in MITT was 57.1 compared to 98.5% in susceptible population after 24h of constant exposure. The mean per cent parasitism at 32°C, 36°C, 38°C and at variable temperature of 32-38°C was significantly higher in tolerant strain (46.7, 45.0, 18.3 and 63.3%) compared to susceptible strain (54.0, 6.7, 0.0 and 0.0%), respectively. These studies suggest that the improved strain of T. chilonis will provide effective control of the pest even at harsh climatic conditions and under high insecticide pressure in different economically important crops.

Parasitism of Bemisia tabaci (Homoptera: Aleyrodidae) by Eretmocerus mundus (Hymenoptera: Aphelinidae) on cassava

Parasitism rates of Bemisia tabaci (Gennadius) and searching and oviposition behaviours of its parasitoid Eretmocerus mundus Mercet were compared on two cassava varieties: a glabrous variety, Nase 4 and a hirsute variety, MM97/0245 with c. 88 leaf hairs/cm 2 . Parasitism was assessed after potted plants of both varieties were exposed in open fields to natural infestation by B. tabaci and its natural enemy. For the behavioural studies, naive, less than 24-h-old females were individually observed on infested cassava leaflets under a microscope for a maximum of 1 h each. The different foraging behaviours were recorded using the computer software 'The Observer 5.0' (Noldus Ltd, Wageningen, The Netherlands). Total per cent parasitism and parasitism by E. mundus did not differ significantly between varieties. Upon encounter with leaf hairs, the parasitoids stopped and groomed before resuming the host search. The frequency of repeat probing, host feeding and antennation after probing and host feeding were higher on the glabrous than on the hirsute variety, while the converse was observed when feeding on liquids on the leaf. The duration of host assessment, initial probing, grooming and resting on the leaf was higher on the glabrous than on the hirsute variety. Leaf hairiness at the density investigated caused some changes in the behaviour of the parasitoids, but did not have an overall effect on field parasitism. Since cassava is generally considered to have glabrous leaves and the variety MM97/0245 is one of the most hirsute varieties, we discount leaf hairiness as a factor in determining levels of parasitoid activity.

Parasitism and hyper parasitism on Pyrilla Perpusilla Walker in sugarcane ecosystem

The seasonal variation in parasitism on Pyrilla perpusilla Walker (Lophopidae: Homoptera) in situ by parasitoids were examined at fortnightly interval, from April to December 2004 (Plant crop) and 2005 (Ratoon crop) in sugarcane ecosystem. These fields were kept free from insecticidal applications. During, 2004 there was no parasitization in the month of April while 3.7± 0.2 per cent nymphs were parasitized in May first fortnight. With the increase in Pyrilla population, rise in parasitization by Epiricania melanoleuca (Epipyropidae: Lepidoptera) started and reached its peak 80.5± 4.9 per cent on nymphs in November second fortnight. Adult parasitization (6.2± 0.5%) was noticed in May first fortnight and touched its peak at 77.0± 5.1 per cent in November second fortnight. While during 2005 parasitization were observed at 82.3± 4.8 per cent on nymphs and 75.0± 3.9 per cent on adults in November second fortnight. The range of parasitization by E. melanoleuca on nymphs+ adults was 5.0± 0.4 to 78.8± 5.0 per cent and 4.8± 0.7 to 78.7± 4.4 per cent during 2004 and 2005, respectively. Significant negative correlation with maximum (r=−0.825) and minimum (r=−0.800) temperature and non significant positive correlation with Relative humidity (r=0.352) and Rain fall (r=0.242). Per cent parasitism by egg parasitoids (combined) viz., Parachrysocharis javensis, Cheiloneurus pyrillae and Ooencyrtus pyrillae varies from 23.8± 2.9 to 83.0± 5.8 per cent from the month of July to December based on egg mass but based on individual eggs it was 9.6±2.1 to 78.2±5.2 per cent. Highest parasitization was in the month of December. No hyper parasitoid recorded on egg of E. melanoleuca. The hyper parasitoid Ecthrodryinus sp. (0.7±0.2 to 2.3± 0.2 per cent) and Fusarium sp. (0.4± 0.1 to 6.8± 2.3 per cent) recorded on pupae of E. melanoleuca from September to November.

Plant Volatile Diversity in Different Tomato Genotypes and its Influence on Parasitization Efficiency of Trichogramma chilonis Ishii on Helicoverpa armigera (Hubner)

Evaluation of 15 tomato genotypes (Varieties/hybrids) for their influence on the parasitization efficiency of Trichogramma chilonis Ishii on Helicoverpa armigera (Hubner) eggs under screen house condition revealed significant differences in terms of per cent parasitization. Least parasitization was recorded on Arka Abha (20%) and highest on Arka Ahuti (50%), followed by Anand-1 (46.66%). Olfactory response of T. chilonis to tomato fruit volatiles did not show significant differences. However, leaf volatiles showed significant differences in their attraction to T. chilonis. The fruit volatiles identified from different genotypes comprised 16 compounds, which include alkane hydrocarbons, monoterpenes, sesquiterpenes, diterpenes and other metabolites. It revealed great fruit volatile diversity in terms of number of compounds (qualitative) and their proportions (quantitative). Maximum compounds were identified from variety Ramya and Pusa Ruby (12 each). The major compound present in the fruit volatiles was Linalool-L and its proportionate concentration varied from 1.79 (Pusa Ruby) to 91.12 per cent (Arka Abha). This was followed by heptadecane (present in all the genotypes) and the proportionate concentration varied from 2.89 (A. Saurabh) to 62.9 per cent varalakshmi. The leaf volatile profiles of the genotypes evaluated include 19 compounds. Except genotype varalakshmi in which a-pinene constituted 69.69 per cent of total volatiles, in all other genotypes heptadecane was the main compound and the concentration varied from 21.72 (in Ramya) to 60.75 per cent (in A. Abha). Some of the compounds identified α-phellandrene, a-pinene, trans-caryophyllene, (Z)-α-farnesenc, trans-α-ocimene and selinene are known for their synomonal activity.

Evaluation of Quality of Trichogramma chilonis Ishii from Different Production Units in India

The post-shipment quality of parasitized egg cards of Trichogramma chilonis Ishii obtained from nine production units in South India was evaluated. Evaluations included the number of parasitized eggs per card, per cent parasitism, per cent adult emergence, sex-ratio and parasitizing efficiency on the target host. There was a lot of variation in the card size and the number of eggs per card. The parasitism was more than 90 per cent in the tricho-cards supplied by two units. The adult emergence and sex-ratio was as per the quality standards, Considering the recommendation of 1,50,000 parasitized eggs per hectare of cotton, only three units could reach the quality standards. The parasitizing efficiency of T. chilonis supplied by two units was less than 50 per cent and parasitism ranged between 60 and 73 per cent in the others. There is a need for regulatory agencies to periodically evaluate the quality of Trichogrammatids produced by insectaries based on simple and reliable methods. Trichogramma producers should reach a consensus with respect to the method of producing Tricho-cards and recommendations to be given to farmers. This would ensure the proper utility of Trichogrammatids in biocontrol programmes.

Effect of Low Temperature Storage on the Efficiency of Three Species of Trichogrammatids

The effect of low temperature (4 ± 0.5°C) and refrigerator storage on three trichogrammatids, viz Trichogramma chilonis Ishii, T. pretiosum Riley and T. brasiliense Ashmead was studied under laboratory conditions. T. chilonis and T. pretiosum can be stored for 20 days whereas T. brasiliense for 10 days without adversely affecting their emergence and parasitisation efficiency taking 60 per cent emergence and 60 per cent parasitism as standard. The emergence in 71 brasiliense reached zero per cent after 34 days of storage whereas 20.3 per cent was recorded in T. chiloni s and 1S.7 per cent in T. pretiosum after 60 days of storage. T. chilonis showed the highest emergence and parasitization efficiency followed by T. pretiosum and T. brasiliense .

Factors affecting parasitism by Microctonus aethiopoides (Hymenoptera: Braconidae) and parasitoid development in natural and novel host species.

A laboratory study of aspects of parasitoid host acceptance, suitability and physiological regulation in natural and novel host species was carried out to investigate the degree of variability encountered with different hosts and to determine the value of such observations in host range determination. The parasitoid Microctonus aethiopoides Loan was exposed to a natural host, Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) and three novel hosts, the New Zealand native Nicaeana cervina Broun, the introduced weed biological control agent Rhinocyllus conicus (Froehlich), and a congeneric pest species, Sitona lepidus Gyllenhal (all Coleoptera: Curculionidae). Per cent parasitism of these species was 54%, 43%, 39% and 0%, respectively. The results indicated that for both S. discoideus and R. conicus more males than females were parasitized (69% cf. 45%, and 49% cf. 32% respectively) but host size was not a significant factor. Overall, superparasitism was recorded in about 29% of parasitized weevils and there was evidence that host discrimination to avoid superparasitism occurred in the natural host. Conversely, superparasitism occurred more frequently than would be expected in N. cervina (42%) coupled with higher survival of larvae in superparasitized hosts in this species. The frequency distribution of attack of R. conicus by M. aethiopoides was not different from random. Parasitoid development was more rapid in the natural host, S. discoideus, and parasitoid size was positively correlated with host size. There was a strong positive relationship between parasitoid larval survival and the presence of teratocytes in all hosts. Host fecundity and fertility were reduced by parasitism for most species, and in some cases, by exposure to parasitoids in the absence of detectable parasitism. It was concluded that laboratory observations can provide useful information on the compatibility between host and parasitoid which can complement traditional host range tests to predict field host range.

Effect of Storage on the Emergence and Parasitization Efficiency of Laboratory Reared and Field Collected Populations of trichogramma Chilonis Ishii

The parasitoid, Trichogramma chilonis could be stored in the refrigerator and successfully utilized for 23 days without adversely effecting their emergence and parasitization efficiency. The mean per cent parasitization decreased with the increase in storage period. Among the four populations studied, Muktsar population was most efficient as it showed maximum mean emergence (60.4 %) and mean per cent parasitization (52.1) for 60 days.

Host Plant Preference of Senometopia illota (Curran) (Diptera:Tachinidae) to Helicoverpa armigera (Hubner) (Lepidoptera:Noctuidae) on Pigeonpea and Chickpea

Senometopia illota (Curran) (Diptera: Tachinidae) is a larval-pupal parasitoid on Helicoverpa armigera (Hubner). Host plant preference of S. illota was studied by comparing the percentages of parasitism on pigeonpea and chickpea. The average per cent parasitism was recorded for the months of December and January from 1993 to 1996. It was found that S. illota gives more preference to H. armigera on pigeonpea (17.39%) than chickpea (7.74%).

Stem‐boring insects of fragmented Calamagrostis habitats: herbivore–parasitoid community structure and the unpredictability of grass shoot abundance

Abstract.1. Communities of stem‐boring insects attacking the grass Calamagrostis epigeios (L.) Roth were analysed from twenty‐five pure stands of C. epigeios differing in area and isolation. Insect communities comprised nine phytophagous and eighteen entomophagous species. Most abundant herbivores (attacking > 1% of all shoots) were Tetramesa eximia (Giraud) (Hym. Eurytomidae), Eurytoma sp. (Hym. Eurytomidae), Lasioptera calamagrostidis (Rübs.) (Dipt. Cecidomyiidae), and Eriopeltis sp. (Hom. Pseudococcidae). About 28% of the twenty‐seven species were monophagous, 61% oligophagous (restricted to Poaceae), and 11% polyphagous. Although herbivores generally attacked thick shoots, species‐specific differences in the attacked mean diameter were found.2. The main purpose of this study was to analyse the relative effects of area, isolation and unpredictability of available food resources on the abundance of herbivores, parasitoids and resulting tritrophic effects. Variability of shoot abundance varied greatly between years, and even more between habitats within the same year. On average, shoot density per habitat increased or decreased 2.4‐fold between succeeding years.3. Variability of grass shoot abundance was not related to habitat characteristics such as area, isolation, biomass, shoot density, changes in area or shoot density between years, or shoot features like internode number or diameter, but was negatively influenced by shading of trees. Similarly, habitat area or isolation did not correlate with other habitat features.4. Grass shoot abundance was the most important predictor of species abundance and attack rate of herbivores. In contrast to expectations, area and isolation of habitats did not explain differences in species richness, and only influenced abundance of three species. In addition, even the experimental removal of all grass shoots (and thereby, of all stem‐boring insects) from five habitats in winter did not negatively influence colonization the following year. These results suggest a surprisingly high mobility of this rather specialized community of stem‐boring insects that appeared to superimpose on area and isolation effects. Unpredictability of grass shoot abundance was presumably the main selection pressure for the obviously high dispersal abilities of the Calamagrostis insects.5. Per cent parasitism was mainly influenced by the percentage of attacked shoots. Parasitism of T. eximia by its major parasitoid also correlated with habitat connectivity, emphasizing the hypothesis that a continuum of habitats should be particularly favourable for the third trophic level.

Biology of Gregarious Parasitoids of Uzi Fly, Exorista bombycis Louis (Diptera: Tachinidae)

Biology of indigenous parasitoids namely. Trichopria sp., Exoristobia philippinensis Ashmead and Spalangia endius Walker of the uzi fly Exorista bombycis Louis was studied in the laboratory. All the parasitoids lived significantly longer in the presence of host and diet compared to either diet or host. They preferred to parasitize 2-4 days old host pupae and per cent parasitism was highest (4.23,5.0 and 8.43) on this age group. Adult parasitoids mated soon after emergence. The average fecundity was higher in E. philippinensis and Trichopria sp. compared to S. endius . Arrhenotokous parthenogenesis occurred in all the three species of parasitoids.

Does gall diameter affect the parasitism rate of Asphondylia borrichiae (Diptera: Cecidomyiidae)?

Abstract. 1. Fertilized field plots of Borrichia frutescens (L.) de Candolle produced plants with a higher apical‐leaf nitrogen content than control plots.2. Gall frequency of the cecidomyiid Asphondylia borrichiae Rossi & Strong on stems of B.frutescens, increased significantly on fertilized plots after approximately 3 months.3. Fertilizer treatment did not result in changes in stem density but did tend to increase proportion of stems flowering and overall plant size. Galls are not normally found on flowering stems.4. Galls grew at a faster rate and to a larger final size on fertilized plots.5. On three sampling dates, per cent parasitism of galls was the same on fertilized and control plots; therefore, this study does not support the galldiameter hypothesis.

Effect of Insecticides on the Occurrence and Association of Whitefly, Aphid and Parasites on Cotton

Observations in cotton field sprayed with insecticides showed that Aphis gossypii Glov. parsltlsm by Aphis gossypii Timberlake was very high in plots treated with fenvalerate. Triazophos and fenvalerate registered high populations of aphids which precluded the incidence of the whitefly Bemisia tabaci (Gennadius). Elimination of aphids by monocrotophos and methyl demeton provided a better habitat for B. tabaci . Positive association between the aphid and its parasite was seen in phosalone (r = 0.67), mineral oil (r = 0.52), endosulfan(r = 0.52), fish oil rosin soap (r = 0.51), methyl demeton (r = 0.50), neem oil (r = 0.48), fenvalerate (r = 0.48) and check (r = 0.65). Monocrotophos and triazophos had no association. The linear regressions showed that fenvalerate, phosalone and check plots permitted 96.9, 58.8 and 40.2 per cent parasitism respectively while only 13.8 to 31.5 per cent parasitism was observed in other insecticidal treatments. For occupation and development, there was a negative association between the aphid and whitefly in plots treated with phosalone (r = - 0.81), minerai oil (r = - 0.77), methyl demeton (r = - 0.72) and endosulfan (r = - 0.46).

Effect of some insecticides on the parasitoids and predators of the cotton whitefly, Bemisia tabaci Genn.

In an evaluation of the effects of different insecticides against the natural enemies of whitefly, Bemisia tabaci Genn., cotton crop treated with synthetic pyrethroids recorded 9.7 per cent parasitism due to aphelinid and it was on par with endosulfan. Pyrethroids were highly detrimental to the predators, recording the lowest number of 2 to 4.3 of early and 0.3 to 1.2 late occurring predators per 10 leaves. The insecticides of natural origin showed 15.8 to 18.1 per cent parasitoid activity and maintained 3.4 to 7.9 predators/l0 leaves. Triazophos and deltaphos recorded the lowest parasitism and predation levels, whereas fenpropethrin recorded a higher level (14.8 per cent) of parasitism.

The influence of host distribution, sex, and size on the level of parasitism by Itoplectis conquisitor (Hymenoptera: Ichneumonidae)

Abstract. 1. Parasitism of the bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae), on red cedar was studied at Manassas, Va., U.S.A.2. Fifteen parasitoids, five of which were hyperparasitoids, attacked the pupal stage of the bagworm. The Ichneumonid Itoplectis conquisitor alone accounted for 58% of the parasitized bagworms.3. Parasitism by I conquisitor (Say) was inversely related to host size, but independent of host distribution within a tree. Male bagworms experienced disproportionately higher levels of parasitism than females. We conclude that it is small size that renders bagworms susceptible to parasitism rather than sex per se.4. Ovipositor lengths of I.conquisitor were insufficient to penetrate the larger bagworm hosts (>57 mm); and in fact, as bagworm size increased, the proportion of the I.conquisitor population capable of penetrating the pupa declined abruptly. We suggest that the mechanical difficulties with oviposition, and perhaps the defensive capabilities of larger hosts, are responsible for the relationship between host size and per cent parasitism.5. I.conquisitor could be an important selective agent for bagworm size at pupation, but it is not likely to act as a significant control agent of population density.

Patterns of parasitism by Trybliographa rapae, a cynipid parasitoid of the cabbage root fly, under laboratory and field conditions

ABSTRACT. The spatial patterns of parasitism of the cabbage root fly caused by the cynipid parasitoid Trybliographa rapae (Westw.) have been studied in a laboratory system, within field cages and in a natural situation. Continuous observations during the laboratory experiments showed the parasitoids to spend proportionately more time on the patches of high host density. This resulted in the per cent parasitism per patch being directly density dependent. Similar patterns of parasitism were found from the field cage system, and also from experiments using the natural parasitoid population and either manipulated or natural host densities. While mutual interference was marked in the laboratory experiments, there was little or no sign of it within the larger field cages.

Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies

ABSTRACT. Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers. The strongest effects of galling were the total elimination of the species‐rich cocoon‐attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura. All tachinid larval parasitoids were also eliminated by the galling habit. The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers. General patterns in per cent parasitism by non‐tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non‐tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non‐tachinid larval parasitoids. The galling habit had a long‐term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.

Seasonality ofEurytomasp.—a parasitoid on okra petiole maggot,Melanagromyza hibisciSpencer

Abstract Studies on the seasonal abundance of Eurytoma sp. a parasitoid on okra petiole maggot, Melanagromyza hibisci Spencer were conducted for one year. Per cent parasitism ranged from 10 to 68 during the study period. However, there was no significant relationship between percentage parasitism on host density. Data further revealed that parasitoid response to host density was weak.

Preference of Hyposoter didymator (Thunberg) to Spodoptera litura (Fabricius) on different host plants

Preference of the exotic parasite Hyposoter didymator (Thunberg) to parasitise Spodoptera litura (Fabricius) feeding on 8 different host plants was studied in the laboratory. In a no-choice test, maximum perference was for host larvae on castor and beetroot, followed by tobacco cv. Xanthi, cauliflower, cowpea, okra and cabbage, larvae on tobacco cv. Jayashri remained Unparasitised in both nochoice and multi-choice tests. Per cent parasitism obtained on the host plants (except tobacco cv. Jayashri)by multi-choice test was statistically similar. Per cent adult emergence was higher on cabbage, cauliflower, castor and beetroot than on other host plants. However, the food plants of the host seemed to have no effect on the developmental time and sex ratio of the progeny.