Cent Parasitism Research Articles

Effect of neem oil based nanoemulsion on egg parasitoid, Trichogramma chilonis (Ishii) (Hymenoptera: Trichogrammatidae)

Botanical biopesticides are alternative to hazardous synthetic insecticides. In the present study neem oil based nanoemulsion was synthesized using neem oil and tween 80. The particle size was estimated as 159.2 nm. The emulsion was characterized using particle size analyzer and TEM to confirm the formation of nano emulsion of neem oil. Trichogramma chilonis (Ishii) is an effective egg parasitoid of lepidopterous pests. It controls pests in eggs stage prior to its damaging to crops. The parasitoid is vulnerable to insecticides or oil sprays applied to the crops. The present study revealed the effects of neem nanoemulsion with T. chilonis under the controlled laboratory conditions. Different concentrations i.e., 50, 100, 500, 1000, 5000, 10000 ppm were tested on T. chilonis . The biological effects viz., per cent parasitism, adult emergence were found significantly reduced and increased mortality in all the concentrations of macroemulsion of neem oil (66.78 ± 0.50, 71.69± 1.02; 48.45 ± 0.35, 52.26 ± 0.60; 31.75 ± 0.35, 26.00 ± 0.39 in 10000 and 5000 ppm, respectively) as compared with nanoemulsion (75.40 ± 0.03, 78.26 ± 0.29; 52.50 ± 0.52, 57.85 ± 0.60; 19.57 ± 0.27, 16.25 ± 0.25 in 10000 and 5000 ppm, respectively and control (88.00 ± 0.12; 82.00 ± 1.26; 2.25 ± 0.02, respectively). These studies showed that the 10000 and 5000 ppm concentrations of nanoemulsion of neem oil were found less toxic to T. chilonis .

Potential natural enemies of the invasive rugose spiraling whitefly, <i>Aleurodicus rugioperculatus</i> Martin in India

A invasive rugose spiraling whitefly (RSW) <em>Aleurodicus rugioperculatus</em> Martin (Hemiptera: Aleyrodidae) was found infesting coconut, banana, custard apple and several ornamental plants in Tamil Nadu, Andhra Pradesh and Kerala for the first time in India. The identity of the pest species was determined through morphological and molecular tools. Furthermore cytochrome c oxidase-I gene (658 bp) of RSW was sequenced (GenBank accession number KY209909) which would serve as an ideal molecular diagnostic marker for its identification irrespective of its phenotypic plasticity. During the survey, several natural enemies were recorded and maximum parasitism was recorded by <em>Encarsia guadeloupae</em> Viggiani (Hymenoptera: Aphelinidae) and its COI gene was sequenced and deposited as <em>Encarsia</em> sp. (GenBank accession number KY223606). Per cent parasitism ranged from 20.0 to 60.0 % in different collection locations, highest parasitism being recorded in Kerala as compared to other states. The predators recorded were <em>Mallada</em> sp., few coccinellids and predatory mites. This communication is the first report of the rugose spiraling whitefly, its host plant range and associated natural enemies in India.

Potential natural enemies of the invasive rugose spiraling whitefly, <i>Aleurodicus rugioperculatus</i> Martin in India

A invasive rugose spiraling whitefly (RSW) <em>Aleurodicus rugioperculatus</em> Martin (Hemiptera: Aleyrodidae) was found infesting coconut, banana, custard apple and several ornamental plants in Tamil Nadu, Andhra Pradesh and Kerala for the first time in India. The identity of the pest species was determined through morphological and molecular tools. Furthermore cytochrome c oxidase-I gene (658 bp) of RSW was sequenced (GenBank accession number KY209909) which would serve as an ideal molecular diagnostic marker for its identification irrespective of its phenotypic plasticity. During the survey, several natural enemies were recorded and maximum parasitism was recorded by <em>Encarsia guadeloupae</em> Viggiani (Hymenoptera: Aphelinidae) and its COI gene was sequenced and deposited as <em>Encarsia</em> sp. (GenBank accession number KY223606). Per cent parasitism ranged from 20.0 to 60.0 % in different collection locations, highest parasitism being recorded in Kerala as compared to other states. The predators recorded were <em>Mallada</em> sp., few coccinellids and predatory mites. This communication is the first report of the rugose spiraling whitefly, its host plant range and associated natural enemies in India.

The Invasive Rugose Spiraling Whitefly Aleurodicus rugioperculatus Martin in India

A new invasive rugose spiraling whitefly (RSW) Aleurodicus rugioperculatus Martin was found infesting coconut, banana and several ornamental plants in Tamil Nadu, Andhra Pradesh and Kerala for the first time in India. The identity of the pest was determined through morphological and molecular tools. Furthermore COI gene (658 bp) of RSW was sequenced (GenBank accession number KY209909) which would serve as an ideal molecular diagnostic marker for its identification irrespective of its phenotypic plasticity. During the survey, several natural enemies were recorded and maximum parasitism was recorded by Encarsia guadeloupae Viggiani and its COI gene was sequenced and deposited as Encarsia sp. (GenBank accession number KY223606). Per cent parasitism ranged from 20.0 to 60.0% in different collection locations, highest parasitism being recorded in Kerala as compared to other states. The predators recorded were Mallada sp., few coccinellids and predatory mites. This communication is the first report of the rugose spiraling whitefly, its host plant range and associated natural enemies in India.

Biology, Relative Parasitization of Larval Endoparasitoid <I>Campoletis cholrideae</I> Uchida on <I>Heliocoverpa armigera</I> Hübner under Sole and Chickpea-coriander Intercropping System

The <em>Campoletis cholrideae</em> is a single most prominent parasitoid in chickpea for major pest <em>Heliocverpa armigera</em> under natural ecosystem. The purpose of present study was to investigate how weather parameters and cropping system influence on the biology, per cent parasitization in sole and intercropping system, under laboratory and field conditions. In sole crop, mean parasitism by <em>C. chlorideae</em> on the larvae of <em>H. armigera</em> during 2013 and 2014 was 60.61 %, 44.66 % respectively. Egg-larval and cocoon formation to adult emergence periods 10.16 ± 0.215, 4.25 ± 2.02 days respectively and female and male parasitoid could survive with a mean longevity of 4.50 ± 2.012 and 3.25 ± 1.85 days, respectively. Higher parasitism of 76.67% occurred on 8<sup>th</sup> collection of 11<sup>th</sup> S.W March and 60.67% on 1<sup>st</sup> collection of 11<span>th</span> S.W of March for respective years. The progeny of sex-ratio varied in two seasons, the mean sex ratio (M:F) were 1:1.62; 1:1.07 respective years in sole crop. In intercropping ecosystem, the overall mean parasitism by <em>C. chlorideae</em> on larvae of <em>H. armigera</em> during 2013 and 2014 with 76.96 %, 66.67 % respectively. Higher parasitism was observed (90 %) on 6<sup>th</sup> collection of 11<sup>th</sup> S.W March and 80 % on 1<em>st</em> collection of 11<sup>th</sup> S.W of March for respective years. However there was steep escalation in female sex ratio in chickpea-coriander cropping system when compared with sole crop. The overall mean sex ratio were (M:F) is 1:1.90; 0.98:1.0 respective years in chickpea-coriander intercropping. A correlation with abiotic factors revealed a non-significant positive correlation with maximum temperature, evening relative humidity (RH), rain fall and sunshine hours. There was a negative correlation between parasitism and minimum temperature and morning RH in respective years under sole crop. In case of intercropping system, the result elucidated that a significant positive correlation exist with evening RH and rainfall (r= 0.951; r= 0.900 and r= 0.926; r= 0.931) in respective years. These results suggested that different parameters, especially cropping system and temperature, were very important for the parasitism of <em>C. chlorideae</em> on <em>H. armigera</em>.

Biology, Relative Parasitization of Larval Endoparasitoid <I>Campoletis cholrideae</I> Uchida on <I>Heliocoverpa armigera</I> Hübner under Sole and Chickpea-coriander Intercropping System

The Campoletis cholrideae is a single most prominent parasitoid in chickpea for major pest Heliocverpa armigera under natural ecosystem. The purpose of present study was to investigate how weather parameters and cropping system influence on the biology, per cent parasitization in sole and intercropping system, under laboratory and field conditions. In sole crop, mean parasitism by C. chlorideae on the larvae of H. armigera during 2013 and 2014 was 60.61 %, 44.66 % respectively. Egg-larval and cocoon formation to adult emergence periods 10.16 ± 0.215, 4.25 ± 2.02 days respectively and female and male parasitoid could survive with a mean longevity of 4.50 ± 2.012 and 3.25 ± 1.85 days, respectively. Higher parasitism of 76.67% occurred on 8 th collection of 11 th S.W March and 60.67% on 1 st collection of 11 th S.W of March for respective years. The progeny of sex-ratio varied in two seasons, the mean sex ratio (M:F) were 1:1.62; 1:1.07 respective years in sole crop. In intercropping ecosystem, the overall mean parasitism by C. chlorideae on larvae of H. armigera during 2013 and 2014 with 76.96 %, 66.67 % respectively. Higher parasitism was observed (90 %) on 6 th collection of 11 th S.W March and 80 % on 1 st collection of 11 th S.W of March for respective years. However there was steep escalation in female sex ratio in chickpea-coriander cropping system when compared with sole crop. The overall mean sex ratio were (M:F) is 1:1.90; 0.98:1.0 respective years in chickpea-coriander intercropping. A correlation with abiotic factors revealed a non-significant positive correlation with maximum temperature, evening relative humidity (RH), rain fall and sunshine hours. There was a negative correlation between parasitism and minimum temperature and morning RH in respective years under sole crop. In case of intercropping system, the result elucidated that a significant positive correlation exist with evening RH and rainfall (r= 0.951; r= 0.900 and r= 0.926; r= 0.931) in respective years. These results suggested that different parameters, especially cropping system and temperature, were very important for the parasitism of C. chlorideae on H. armigera .

Natural Parasitism of Lepidopteran Insect Pests in Organic and Conventionally Managed Basmati Rice in Punjab

Natural parasitism of rice yellow stemborer, Scirpophaga incertulas (Walker) and leaffolder, Cnaphalocrocis medinalis (Guenee) in organically as well as conventionally grown basmati rice (Pusa Basmati 1121) was recorded at farmers’ field during 2012. Different stages of stemborer and leaffolder were collected and observed under laboratory conditions for the emergence of parasitoids to record natural parasitism. The parasitism in the eggs, larvae and pupae of rice stemborer and leaffolder ranged from 1.67 to 30.91 and 1.86 to 28.87 per cent in organic and conventional basmati rice, respectively. Egg parasitoids, Trichogramma chilonis, T. japonicum, Telenomus sp. were recorded from the eggs of rice stemborer. Braconid wasps, Stenobracon nicevillei and Bracon sp were recorded from the larvae of stemborer. Tetrastichus sp and Brachymeria sp were the pupal parasitoids with per cent parasitism ranging from 5.09 to 5.36 and 2.83 to 3.17 in conventional and organic fields. Larval parasitoids, Bracon sp and Cotesia sp were recorded from rice leaffolder and the parasitism ranged from 5.88 to 6.02. Pupal parasitoids, Tetrastichus sp and Brachymeria sp were recorded with parasitism ranging from 4.08 to 5.59 per cent.

English

Triungulins are young instar larvae of meloid (blister) beetles. Blister beetles are pest insects feeding on flowering bodies of several agricultural and non agricultural plants. On the contrary Xylocopa letipes Drury is very potential plant pollinator but triungulins of Nemognatha plazata Fab. act as limiting factor of X. letipes population by parasitism. Therefore, any advance knowledge on host parasite association of this model will add great relevance in protecting X. letipes. Triungulins of blister beetle N. plazata ascended on X. letipes body during the visits to flowers of Peltophorum pterocarpum L. and later brought to the Xylocopa nesting. Triungulins used grubs of X. letipes for food. The triungulins N. plazata were different from others by having 1 or 2 stemmata on each side of head and was not parallel sided but pointed and with two short bristles to posterior side of the body. Triungulin aggregations responded as bridge between to substrates, contraction and expansion of biomass for external stimuli and as attractant for N. plazata. The per cent parasitism recorded on X. Letipes was 36.84% and 37. 14% in the years 2014 and 2015 respectively and Xylocopa comfortably carried the load of 23 triungulins on its body.

Biological control of Eucalyptus gall wasp, Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) by its native parasitiods

Utilization of native parasitoids viz. Megastigmus dharwadicus Narendran and Vastrad (Hymenoptera: Torymidae) and Aprostocetus galaWalker (Hymenoptera: Eulophidae) for biological control of eucalyptus gall wasp, Leptocybe invasa Fisher and LaSalle (Hymenoptera: Eulophidae) is reported. Two native parasitoids multiplied in the greenhouse were released in a severely affected eucalyptus plantation spread over an area of 1000 ha. A total of 14,000 heavily parasitized galled seedlings, 1400 M. dharwadicus and 300 A. gala were distributed over a period of six months. The per cent parasitization by these native parasitoids was ascertained before distribution of galled seedlings. Though there was a gradual increase in per cent parasitization, the reduction in gall incidence was not evident up to three months. However, drastic reduction in gall incidence and pest emergence accompanied by very high per cent parasitization was evident within eight months. Post release evaluation conducted during June 2011 and May 2012 indicated the successful control of the pest.

Cotesia flavipes Cameron parasitizing Chilo partellus (Swinhoe): Host-age dependent parasitism, cocoon formation and sex ratio

Investigations on parasitization of different host ages (5 to 20 days old) of Chilo partellus larvae by Cotesia flavipes were carried in the laboratory conditions at 27±2°C and 75±5 per cent relative humidity. Higher parasitization and cocoon formation was recorded on the 17 and 20 day old larvae of C. partellus with 82.61 and 82.46 per cent parasitization and 43.09 and 42.70 cocoon formation, respectively while no parasitization and cocoon was recorded in 5 day old larvae. The 11 and 14 day old larvae were highly preferred recording significantly more female progeny and on par with 17 and 20 days old larvae.

Seasonal Incidence of Pod Fly, Melanagromyza obtusa (Malloch) and Its Hymenopteran Parasitoids on Pigeonpea

The activity of pod fly, Melanagromyza obtusa (Malloch) (Diptera: Agromyzidae) attained peak level during 46th standard week while the population of M. obtusa was minimum (31/100 pods) during 49 th standard week. The peak level of weekly per cent parasitization (18.18%) was observed during 51 st standard week while minimum level of weekly per cent parasitization (6.52%) was observed during 47 th standard week. Simple correlation was worked out between M. obtusa population and weather parameters and it revealed that positive significant correlation with minimum temperature (r = 0.769). Correlation between parasitization and percent was not significant. The regression revealed that the various abiotic factors was found to be most influencing factor, which contributed (R 2 = 0.885 and 0.863) 88.5 and 86.3 per cent variation in M. obtusa population and per cent parasitization, respectively.

Seasonal Incidence of Pod Fly, Melanagromyza obtusa (Malloch) and Its Hymenopteran Parasitoids on Pigeonpea

The activity of pod fly, Melanagromyza obtusa (Malloch) (Diptera: Agromyzidae) attained peak level during 46th standard week while the population of M. obtusa was minimum (31/100 pods) during 49 th standard week. The peak level of weekly per cent parasitization (18.18%) was observed during 51 st standard week while minimum level of weekly per cent parasitization (6.52%) was observed during 47 th standard week. Simple correlation was worked out between M. obtusa population and weather parameters and it revealed that positive significant correlation with minimum temperature (r = 0.769). Correlation between parasitization and percent was not significant. The regression revealed that the various abiotic factors was found to be most influencing factor, which contributed (R 2 = 0.885 and 0.863) 88.5 and 86.3 per cent variation in M. obtusa population and per cent parasitization, respectively.

Effect of Insecticides on Some Biological Parameters of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammtidae)

Bioassay carried out to determine the toxicity of seven insecticides (viz. endosulfan 0.07%, imidacloprid 0.004%, spinosad 0.01%, triazophos 0.08%, thiodicarb 0.075%, novaluron 0.01% and azadirachtin @1ml/L) to Trichogramma chilonis showed that spinosad was the most toxic in all the studies followed by triazophos. Spinosad resulted in only 17.80 per cent parasitization and 3.97 per cent adult emergence from the host eggs, Corcyra cephalonica Stainton treated before parasitization. Novaluron was found to be the safest resulting in 58.93 per cent parasitization and 89.72 per cent adult emergence from the host eggs treated before parasitization. The parasitization in other insecticides ranged from 20.00 to 40.47 per cent. Spinosad was also found highly toxic to all the immature stages of T. chilonis resulting in only 0.46, 0.66 and 0.65 per cent adult emergence when the parasitoid was treated in the egg, larval and pupal stages, respectively. Novaluron was found to be safe to all the immature stages of the parasitoid resulting in 86.75, 87.84 and 87.46 per cent adult emergence when treated in egg, larval and pupal stages, respectively. The parasitoid adult emergence in other insecticides ranged from 57.95 to 88.63 per cent when treated in egg stage, 53.97 to 87.12 per cent when treated in larval stage and 61.46 to 87.15 per cent when treated in pupal stage.

Pupal Parasitization of Anaphaeis aurota Fabricius (Lepidoptera: Pieridae) Infesting Capparis decidua (Forsk.) by Brachymeria albicrus (Klug) (Hymenoptera: Chalcididae)

During the surveys conducted in CIAH Farm and in Desnok, Bikaner in the month of November and December, 2010, Capparis decidua (Forsk.) commonly known as kair was found to be heavily infested with Anaphaeis aurota Fabricius commonly known as Pioneer or Caper white. C. decidu a is a bushy shrub used in landscape gardening, afforestation and reforestation in semi desert and desert areas and it provides assistance against soil erosion. The grown caterpillars of A. aurota easily strip off the branches, devouring leaf after leaf causing great damage. The pupae of A. aurota were found to be parasitized with Brachymeria albicrus (Klug). B. albicrus has been earlier reported from southern India, Orissa and from Haryana as Brachymeria kurukshetraensis Farooqi, HusainaGhai. B. kurukshetraensis Farooqi is a junior synonym of B. albicrus . The mean per cent parasitization of Pioneer butterfly by B. albicrus at CIAH farm and at Desnok, Bikaner was 49.5 and 47.5 respectively and the mean per cent emergence of the mature adult parasitoids from the parasitized pupae was 15.5 and 14.0 respectively.

Parasitic Potential of some Braconid Parasitoids against Okra Fruit Borers

In surveys conducted in Coimbatore district during 2009-10, Okra fruit borers, Earias vittella Fabricius, Earias insulana Boisdual and Helicoverpa armigera (Hübner) were the serious pests causing 50 per cent loss. During the survey, three hymenopteran parasitiods viz., Bassus spp., Brachymeria lasus Walker, Goryphus spp., of the families Braconidae, Chalcididae and Ichneumonidae against Earias spp. and the dipteran parasitoid, Carcelia illota (Tachinidae ) against H. armigera were recorded with 0.00 to 10.00 per cent parasitization. All the parasitoids recorded were not amenable for mass culturing, and hence, other braconid parasitoids viz., Bracon brevicornis Wesmael, Bracon hebetor Say and Chelonus blackburni Cameron were studied for their parasitic potential against fruit borer complex. Cent per cent parasitization was observed with B. brevicornis against all instars of E. vittella and H. armigera, higher parasitizaion of 100 and 97.50 per cent was observed by B. hebetor at a parasitoid-host ratio of 5:10 on second instar larvae of H. armigera and fourth instar larvae of E. vittella respectively. The egg - larval parasitoid, C. blackburni recorded the highest parasitization of 70.54 per cent and 64.58 per cent against E. vittella and H. armigera at a parasitoid host ratio of 5:100. For B. brevicornis and B. hebetor, highest cocoon formation and parasitoid emergence was recorded at 4:10 ratio against third and fourth instars. In C. blackburni, the parasitoid host ratio of 3:100 yielded the highest number of adult parasitoids. B. brevicornis was found to be more effective against fruit borers.

Occurrence of Aphidophagous Syrphids in Aphid Colonies on Cabbage (<i>Brassica oleracea</i>) and their Parasitoids

Syrphid (<em>Diptera: Syrphidae</em>) larvae and pupae (149) were collected from an organically grown cabbage field maintained by Department of Agricultural Biology, Faculty of Agriculture, University of Peradeniya. Out of them 15 adults of syrphids emerged and were identified as <em>Allograpta javania</em> and <em>Episyrphus viridaureus</em> (Wiedemann). Most larvae died during rearing. Out of the remaining, 66.7% were parasitized. A significant correlation coefficient (0.83) between the mean number of cabbage aphids and syrphid larvae was noticed. Three species of hoverfly parasitoids, <em>Diplazon orientalis</em> (Cameron) and <em>Diplazon laetatorius</em> (F.) (Ichneumonidae) and <em>Syrphophagus </em>sp. (Encyrtidae) were reared. The <em>Diplazon laetatorius</em> is found to be a new record from Sri lanka. The most frequently found parasitoid was <em>Diplazon laetatorius</em> and the per cent parasitism was 50. The per cent parasitism of <em>Diplazon orientalis</em> and <em>Syrphophagus</em> sp. was 42.3 and 6.3 respectively. Morphological details of each parasitoid species is presented. A significant correlation coefficient (0.91) between total hoverfly larvae and the parasitized hoverfly larvae was noticed. At the beginning of observations, the number of the parasitized larvae was small. As the number of syrphid larvae feeding in cabbage aphid colonies was increasing, the percentage of parasitized larvae increased. During observations in a conventional cabbage field at Paingamuwa area in the Kandy District, 40 syrphid larvae and pupae were collected. Out of them, thirteen adults of syrphids emerged and were identified as <em>Allograpta javania</em> and <em>Episyrphus viridaureus</em>. Most larvae died during rearing. Out of the remaining 10.37% were parasitized. Total number of hoverfly larvae in the insecticide free vegetable field was more than four times higher than the conventionally managed field. Predators of aphids other than syrphids were found at the two sites in low numbers. <br /><br />DOI: <a href="http://dx.doi.org/10.4038/tar.v21i1.2591">http://dx.doi.org/10.4038/tar.v21i1.2591</a><br /><br /><em>Tropical Agricultural Research</em> Vol. 21(1): 99-109 (2009)

Long-term efficacy of Encarsia dispersa Polaszek (Hymenoptera: Aphelinidae) for the biological control of Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae) in tropical monsoon Australia

Introductions of Encarsia dispersa Polaszek (Hymenoptera: Aphelinidae) for the biological control of spiralling whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae), were made directly onto Thursday Island, Torres Strait Queensland, in May 1994. Its efficacy was monitored intermittently for 7 years on 10 Acalypha wilkesiana Mull. Arg. (Euphorbiaceae) and two Terminalia catappa L. (Combretaceae) plants. Marked declines in whitefly densities were recorded on all hosts approximately 10 months after parasitoid releases. Declines in whitefly densities over the first 2 years were mostly matched with increases in per cent parasitism; these declines generally coinciding with wet seasons, with small resurgences occurring over the first dry season following the first decline. Whitefly densities and per cent leaves infested on T. catappa, and on A. wilkesiana with flat leaves were low by the latter half of the study. In contrast, A. wilkesiana with convoluted leaves seemed to inhibit the parasitoid by providing physical refuges for whitefly nymphs, resulting in higher whitefly numbers with low parasitism, particularly in dry conditions. Ten to 12 years after these initial declines, whitefly densities have remained low. Adults and larvae of Cryptolaemus affinis Crotch (Coleoptera: Coccinellidae) and larvae of Acletoxenus quadristriatus Duda (Diptera: Drosophilidae) were observed preying on whitefly nymphs during the study. Overall, sampling data suggested that A. dispersus was under biological control. It may be prudent to maintain A. wilkesiana with convoluted leaves (acting as host refuges) on the Torres Strait islands to retain parasitoid persistence, thereby maintaining controlled and stable populations of A. dispersus. In addition, because of the pest's wide host range and the ability for hosts with closed leaf structures, such as A. wilkesiana with convoluted leaves, to harbour higher pest numbers, movements of these plants within or out of tropical areas could pose a significant quarantine risk.

Population dynamics of an Arctiid caterpillar–tachinid parasitoid system using state‐space models

1. Population dynamics of insect host-parasitoid systems are important in many natural and managed ecosystems and have inspired much ecological theory. However, ecologists have a limited knowledge about the relative strengths of species interactions, abiotic effects and density dependence in natural host-parasitoid dynamics. Statistical time-series analyses would be more informative by incorporating multiple factors, measurement error and noisy dynamics. 2. We use a novel maximum likelihood and model-selection analysis of a state-space model for host-parasitoid dynamics to examine 21 years of annual census data for woolly bear caterpillars (Platyprepia virginalis) and their locally host-specific tachinid parasitoids (Thelaira americana). 3. Caterpillar densities varied by three orders of magnitude and were driven by density dependence and precipitation from the previous March but not detectably by parasitoids, despite variable and sometimes high (>50%) parasitism. 4. Fly fluctuations, as estimated from per cent parasitism, were affected by density dependence and precipitation from the previous July. There was marginal evidence that host abundance drives fly fluctuations as a generic linear effect but no evidence for classical Nicholson-Bailey coupling. 5. The state-space model analysis includes new methods for likelihood calculation and allows a balanced consideration of effect magnitude and statistical significance in a nonlinear model with multiple alternative explanatory variables.

Parasitising Efficiency of the Pupal Parasitoid, Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) on Chilo partellus (Swinhoe) at Different Exposure Periods

Pupae of Chilo partellus (Swinhoe) were exposed to one-day-old mated females of Tetrastichus howard (OlIifO) for different periods to determine optimum period of exposure for laboratory production. The percentage parasitism varied significantly from 20 to 80 with different exposure periods. The number of parasitoids obtained per pupa (138.0) and females (71 %) were significantly higher when pupae were exposure for 12 hours and it decreased significantly on increasing exposure period. Though the per cent parasitism was vlry low when the pupae were exposed for 12 hours, the number of parasitoids obtained/ 100 pupae was highest (2760). However, considering progeny production and per cent females obtained, 12 hours exposure period is most suitable for avoiding superparasitism in the lahoratory production of the parasitoid.

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.