A high incidence of parasitism ofHeliothis SPP. [Lep.: Noctuidae] larvae in cotton in Southeastern Arkansas

During 1981 and 1982, bollworm,Heliothis zea (Boddie), and tobacco budworm,H. virescens (F.), larvae (n=3,666) were collected from 41 cotton fields near Portland, Arkansas (USA) to assess the occurrence of parasitism. Three strategies were employed to controlHeliothis spp. in these fields: (1) release ofTrichogramma pretiosum Riley; (2) insecticidal control; or (3) inaction (check). Insecticide use in nonchemical control fields was reduced, but not eliminated.Heliothis spp. larvae collected in cotton had higher parasitism rates in 1981 (30.9%) and 1982 (50.1%) than had been reported for cotton since the advent of organochlorine insecticide usage. Four species of larval parasites and 1 species of larval-pupal parasite were recorded. The larval parasiteMicroplitis croceipes (Cresson) comprised 90.6% and 94.5% of all parasitic insects reared from field collectedHeliothis spp. in 1981 and 1982, respectively. No difference (P>0.05) in level of parasitism existed betweenH. zea andH. virescens. Differences between treatments occurred only in 1982 whenH. zea larvae were parasitized at a greater (P<0.05) rate in check fields (68.3%) than in insecticidal control fields (44.3%). Higher levels of larval parasitism in cotton fields may be a consequence of reduced insecticide usage and changes in materials applied, particularly the pyrethroids. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Dept. of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Influence of parasitism byEucelatoria bryani [Dip.: Tachinidae] on the consumption and utilisation of chickpea flour diet byHeliothis armigera [Lep.: Noctuidae]

Fourth and 5th instar larvae ofHeliothis armigera (Hübner) parasitised byEucelatoria bryani Sabrosky consumed significantly less chickpea flour diet than unparasitised larvae of the same age in the laboratory. Significant reduction in diet consumption, larval weight gain and frass produced at 24 and 48 h following parasitisation was observed in 5th instar host larvae. Parasitised larvae retained a greater percentage of food ingested (AD) than did the unparasitised ones. Unparasitised 5th instar larvae ofH. armigera were more efficient in converting the ingested food (ECI) and digested food (ECD) into body substance than larvae of similar age parasitised byE. bryani.     

Egg parasitism of the yellow rice borer,Scirpophaga incertulas [Lep.: Pyralidae] in Bangladesh deepwater rice

Studies on deepwater rice in Bangladesh from 1977 to 1980 showed that 61–89% of the egg masses of the yellow rice borer,Scirpophaga incertulas (Walker), were attacked by hymenopterous parasites. Egg parasitism increased from 43–48% in broods 2–4 (May–August) to 64–88% in broods 5–6 (September–November). Parasitism was reduced in broods 4 and 5 in 1979 (because of lower host densities) and in 1980 (possibly due to extreme late flooding). Telenomus rowani (Gahan), active throughout the year, parasitized 64% of the eggs in the masses it attacked, 32 larvae/mass surviving.Tetrastichus schoenobii Ferrière first appearing at medium host densities, increased rapidly to attack half of the brood 5 and 6 masses. More than 98% of the eggs in the attacked masses were parasitized, leaving only 1.6 surviving larvae/mass. In 1979 its appearance was delayed by 10 weeks and fewer masses were parasitized due to lower host densities.Trichogramma japonicum Ashmead andTelenomus sp. (a new record) were less important. Multiple parasitism of masses rose from 7% in brood 2 to 28% in brood 5. Egg parasites clearly reduce the numbers ofS. incertulas, a major pest, and thus probably improve the yields of deepwater rice.     

Influence of Landscape Diversity and Composition on the Parasitism of Cotton Bollworm Eggs in Maize

We deployed >50,000 Helicoverpa armigera eggs in maize fields to assess the rate of parasitism by Trichogramma chilonis across 33 sites during a three-year span (2012–2014) in northern China. Subsequently, we used a partial least squares (PLS) regression approach to assess the relationship of landscape diversity with composition and parasitism potential. The parasitism rate of H. armigera eggs by T. chilonis ranged from 0–25.8%, with a mean value of 5.6%. Landscape diversity greatly enhanced parasitism at all four different spatial scales (0.5, 1.0, 1.5 and 2.0 km radius). Both the proportion of arable area and the total planting area of two major crops (cotton and maize) had a negative correlation to the parasitism rate at each scale, whereas parasitism was positively correlated to the proportion of host crops of H. armigera other than cotton and maize at the 0.5 to 2.0 km radius scales as well as to that of non-crop habitat at the 0.5 and 1.0 km radius scales. The study indicated that maintaining landscape diversity provided an important biocontrol service by limiting H. armigera through the egg parasitoid T. chilonis, whereas rapid agricultural intensification would greatly reduce the presence and parasitism of T. chilonis in China.     

The Effectiveness of Trichogramma chilonis,Trichogramma pretiosum and Trichogramma brasiliense (Hymenoptera: Trichogrammatidae) as Parasitoids of Helicoverpa armigera (Lepidoptera: Noctuidae) on Sunflower (Helianthus annuus) and Redgram (Cajanus cajan)

The performance of three species of trichogrammatids on the pest, Helicoverpa armigera was evaluated in the laboratory and screenhouse conditions in Karnataka, India during 1996-97. Laboratory studies indicated that Trichogramma chilonis and Trichogramma pretiosum were more effective parasitoids of H. armigera than Trichogramma brasiliense. In screenhouse conditions, T. chilonis was the most effective parasitoid of H. armigera eggs on sunflower plants in comparison to the other two trichogrammatid species. When releasing 50?000 per ha on sunflower and redgram, T. chilonis parasitised 50.1 and 11.4% H. armigera eggs, respectively. The position of H. armigera eggs on different plant parts of sunflower had no effect on parasitism by T. chilonis. However, parasitism by the same trichogrammatid among different plant parts of redgram varied significantly. It parasitized 43.4 and 18.7% H. armigera eggs on leaves and flowers, respectively, and significantly fewer, 3.9%, on pods (P&lt;0.05). The growth stage of redgram plants also had an effect on parasitism by T. chilonis, parasitism being extremely low on plants with pods.     

Incidence of the introduced parasitoids Cotesia kazak and Microplitis croceipes (Hymenoptera: Braconidae) from Helicoverpa armigera (Lepidoptera: Noctuidae) in tomatoes,sweet corn,and lucerne in New Zealand

Two parasitoids,Cotesia kazak (Telenga) and Microplitis croceipes (Cresson) have been successfully introduced into New Zealand to improve control of Helicoverpa armigera (Hübner), tomato fruitworm. C. kazak has spread throughout the North Island, but M. croceipes is restricted largely to its release areas in crops in the Gisborne and Hawke’s Bay regions in the East Coast of the North Island and in pine plantations in the central North Island. Rates of mortality of H. armigera from parasitism were studied in processing tomato crops where these parasitoids are a key component of an integrated pest management programme, and in sweet corn, lucerne and soybeans. C. kazak was the dominant parasitoid in tomatoes and soybeans. It emerged from small H. armigera larvae and usually killed the host before it caused major damage to fruit. M. croceipes emerged from larger host larvae than C. kazak. Death rates from parasitism of H. armigera larvae in tomatoes increased from less than 1% caused by native parasitoids prior to parasitoid introductions, to 25–45% in 1988 and 70–80% in 1996 following the establishment of both introduced parasitoids. M. croceipes was the most common parasitoid in lucerne and total mortality from all parasitoids was similar to that in tomatoes. Low rates of parasitism by C. kazak in sweet corn were attributed to the reduced penetration of the adult parasitoid into sweet corn fields and to the protection afforded by sweet corn when H. armigera larvae burrowed into corn cobs. The implementation of an IPM programme based partly on the effectiveness of these parasitoids has contributed to a decrease in insecticide applications to processing tomatoes.     

Parasitoids in low-level populations ofLymantria dispar [Lep.: Lymantriidae] in different forest physiographic zones

A 2-year study was conducted on the distribution of parasitoids of gypsy moth,Lymantria dispar (L.) (Lep.: Lymantriidae), in mesic and adjacent higher elevation transition and xeric forest habitats in Vermont (U.S.A.). In both years, overall parasitism ranged from 12–18% in each habitat. When analyzed according to the life stage at which the host was collected, parasitism rates of greater than 40% were obtained among the late instars.Parasetigena silvestris (Robineau-Desvoidy) andPhobocampe disparis (Viereck) were recovered most commonly from the mesic habitat, andCotesia melanoscelus (Ratzeburg) andBlepharipa pratensis (= Sturmia scutellata) (Meigen) were most common in collections from the xeric area. Parasitism byCompsilura concinnata (Meigen) occurred at similar levels in all three habitats, and this species was responsible for the highest parasitism rates on the site, reaching 40% among the late instars in 1985. Percent parasitism byC. concinnata increased three-four-fold from 1984 to 1985, while parasitism by other species declined.     

Parasites of birch casebearer larvae in Newfoundland [Lep.: Coleophoridae]

The birch casebearer,Coleophora fuscedinella Zeller, is the most important pest of white birch,Betula papyrifera Marsh, in Newfoundland. A total of 31 species of parasites and hyperparasites were reared from birch casebearer pupae in this study. An additional 7 species are known to parasitize this casebearer in Newfoundland. Only 3 species were numerous:Itoplectis quadricingulata (Provancher),Cirrospilus cinctithorax (Girault) andHabrocytus semotus (Walker). In western Newfoundland, there was an increase in percent parasitism by all parasites from 5.4% in 1973 to 7.5% in 1974 and to 16.3% in 1975. In central Newfoundland, percent parasitism was about 7% in 1974 and 1975.     

Susceptibility of larvae ofHeliothis zea,H. virescens,andH. armigera [lep.: Noctuidae] to 3 baculoviruses

The pattern of virulence (based on inclusion bodies) for 3 baculoviruses ofHeliothis, i.e. a unicapsid, nuclear polyhedrosis virus (HzSNPV); a multicapsid, nuclear polyhedrosis virus (HaMNPV); and a granulosis virus (HaGIV) was the same (HzSNPV>HaMNPV>HaGIV) for 3 species ofHeliothis. Based on numbers of nucleocapsids, however, the HaGIV was ca 2X more virulent than the HaMNPV for larvae ofH. virescens, (F.), and the HaMNPV was about 6X more virulent than the HaGIV for larvae ofH. armigera (Hübner). The fastest rate of larval mortality was obtained with HzSNPV. Although the mortality rate for HaGIV was faster than that of HaMNPV forH. virescens andH. armigera, it was slower than that of HaMNPV for larvae ofH. zea (Boddie). The pattern of susceptibility ofHeliothis species to HzSNPV and HaMNPV wasH. zea>H. virescens>H. armigera. Differences in susceptibility of the least susceptible species (H. armigera) and the most susceptible species (H. zea) to HzSNPV was ca. 1.6 X. Larvae ofH. zea, however, were ca. 4 to 6 X more susceptible to HaMNPV than were larvae ofH. virescens orH. armigera. A different pattern of susceptibility was recorded for HaGIV when larvae were challenged with HzSNPV and HaMNPV. Larvae ofH. virescens were ca. 20 and 35 X more susceptible to HaGIV than were larvae ofH. zea andH. armigera, respectively.     

The release ofOpius concolor andO. Concolor var.Siculus [Hym.: Braconidae] against the spring generation ofDacus oleae [Dipt.: Trypetidae] on Corfu

Releases ofOpius concolor Szepl. andO. concolor var.siculus Mon. were carried out in the spring to determine if they could be used as a biological control agent against the heavy infestation ofDacus oleae Gmel. which occurs on Corfu at that time. At an initial density of 300–400 parasites per tree the mean parasitism rates of 3rd stage larvae ranged from 30–50% in the 1st week following the release, indicating thatOpius could work well in the spring in the tall trees with large numbers of ripe and heavily infested fruits that are found on Corfu.     

Effect of host plant on parasitism ofHelicoverpa armigera (Lep.: Noctuidae) byMicroplitis demolitor (Hym.: Braconidae)

Microplitis demolitor Wilkinson is an important larval parasitoid ofHelicoverpa armigera (Hübner) andH. punctigera (Wallengren) in Australia. The effect of host plant on parasitism of second instarH. armigera byM. demolitor was investigated in a glasshouse experiment. Parasitism was low (0%) on chickpea. Moderate to high levels of parasitism (22.4% to 75.4%) were recorded on sorghum, sunflower, maize, cotton and soybean. The results suggest that releases of larval parasitoids into chickpea are unlikely to enhance parasitismlevels during the first spring generation ofHelicoverpa spp.     

Effect of hosts and parasite density on the egg parasiteTrichogramma pretiosum [Hym.: Trichogrammatidae]

When females ofTrichogramma pretiosum Riley were confined with host eggs at a density of 2/150 eggs, they produced 12 times more female progeny on eggs of potato tuber moth than on eggs ofHeliothis armigera (Hübner) and 13,6 times more on eggs ofSitotroga cerealella (Olivier) than on eggs ofHeliothis. At a density of 4/150 eggs, the correspondent figures were 13 and 8 times. The percentage emergence fromHeliothis eggs was from 0,29 to 0,14 times as great as from tuber moth orSitotroga. From 15 to 140 times more runts were observed amongTrichogramma fromHeliothis eggs than among those from tuber moth eggs and 8 times more thant among those fromSitotroga eggs. This may explain the low recoveries in South Africa ofT. pretiosum in eggs ofH. armigera collected in cotton fields after mass liberation of the parasite. An increase in parasite density from 1/300 eggs to 16/300 eggs resulted in a decrease from 29 to 14 in the hosts parasitised per female, a decrease in the proportion of female progeny from 72 to 39%, a decrease in the female progeny per female from 18 to 4,8, and an increase in the proportion of runts from 2,4 to 12,4%. It is suggested that in mass culture ofTrichogramma unduly high parasite densities should be avoided in order to reduce the effect of mutual interference and raise the output of female progeny.     

Eggs of stored-product lepidoptera as hosts forTrichogramma evanescens [Hym.: Trichogrammatidae]

Eggs were collected fromAnagasta küehniella (Zeller),Ephestia cautella (Walker),E. elutella, (Hübner),E. figulilella (Gregson), andPlodia interpunctella (Hübner) and exposed to adults of the egg parasite,Trichogramma evanescens Westwood, in a free choice experiment. Host eggs were ranked by decreasing percentages of parasitization as follows:E. elutella > E. cautella > E. figulilella > A. küehniella > P. interpunctella. Differences in percent parasitization were not significant betweenEphestia spp., butA. küehniella andP. interpunctella were parasitized significantly less often. Average percentage egg hatch after exposure toTrichogramma ranged from 5.0 to 9.3%, except forPlodia where it averaged 33.3%. It appears that inundative releases ofTrichogramma into commodity storages could play an important role in suppression of stored-product moth populations.     

Biological and ecological studies of the parasitoidChelonus inanitus [Hym.: Braconidae] in Israel

Only one species ofChelonus Panzer,Chelonus inanitus (L.), was found to be widespread in all areas of Israel. The parasitoid was particularly widespread in alfalfa fields but also was present in cotton, sugar beet, artichoke and corn. Spodoptera littoralis (Boisd) andS. exigua (Hbn.) were the main hosts ofC. inanitus although it might develop in other Lepidoptera species. A study of its population showed that adults were present in the spring, summer and autumn but not during the winter. In most cases the population density of the parasitoid appeared to be related to that of the hosts. Parasitism and sex ratio ofC. inanitus in alfalfa fields were studied. The number of males (average of 75%) was higher than that of the females. Percentage of parasitism in larvae ofS. littoralis andS. exigua reached up to 39.8% and 13.5% respectively. The parasitism values in eggs ofS. littoralis were up to 71%.     

Parasitoids ofPectinophora gossypiella [Lep.: Gelechiidae] andEarias spp. [Lep.: Noctuidae] in the Punjab

Observations on the parasitoids of cotton bollworms in the Punjab were made during 1978 and 1979. The 2 trichogrammatid egg parasitoids, viz.Trichogramma achaeae Nagaraja & Nagarkatti andTrichogrammatoidea sp. nearguamensis Nagaraja (MS) were recovered fromPectinophora gossypiella (Saunders) in addition to 1 braconid egg-larval parasitoidChelonus sp. and 7 larval parasitoids, viz. 4 braconidsApanteles angaleti Muesebeck,Bracon greeni Ashsmead,Camptothlipsis sp. andRogas sp., 1 elasmid,Elasmus johnstoni Ferrière, 1 bethylid,Goniozus sp. and 1 ichneumonid,Scambus lineipes (Morley). FromEarias insulana Boisduval andEarias vittella F., 3 trichogrammatid egg parasitoids,T. achaeae, Trichogramma chilonis Ishii, andT. sp. nearguamensis 2 braconid larval parasitoids,B. greeni andRogas sp. and 1 chalcid pupal parasitoid,Brachymeria nephantidis Gahan, were recovered. One eurytomid hyperparasitoid,Eurytoma braconidis Ferrière was also recovered from the cocoons ofB. greeni. Of these parasitoids,T. achaeae, T. sp. nearguamensis, Camptothlipsis sp. andS. lineipes fromP. gossypiella, T. achaeae andB. nephantidis fromEarias spp. andE. braconidis fromB. greeni are new records.     

Survey for parasites ofSesamia calamistis (Lep.: Noctuidae) andEldana saccharina (Lep.: Pyralidae) in southwestern Nigeria

Field surveys were conducted during 1990–92 to document the relative abundance of different species of parasites of the lepidopterous stem borersSesamia calamistis Hampson andEldana saccharina Walker in maize fields in southwestern Nigeria. Species of parasitoids detected on both stem borers included the larvalpupal parasitoidsSturmiopsis parasitica Curran (Diptera: Tachinidae) andBrachymeria feae Masi (Hymenoptera: Chalcididae), and the larval parasitoidDolichogenidea polaszeki Walker (Hymenoptera: Braconidae). The braconidCotesia sesamiae (Cameron) was found attackingS. calamistis. The hyperparasitoidExoristobia dipterae (Risbec) (Hymenoptera: Encyrtidae) was detected on a pupa ofS. parasitica. Parasitic nematodes belonging toMermis sp. and/orHexamermis sp. were found infesting larvae of both stem borers. Overall, larval/pupal parasitization levels at Ibadan were low and ranged from 4.2 to 22.8% forS. calamistis and 1.2 to 13% forE. saccharina. Of the parasites found,S. parasitica was the most common, followed by nematodes. Four hymenopteran egg parasitoids were found attackingS. calamistis: Telenomus busseolae Gahan,T. isis Polaszek (Scelionidae),Lathromeris ovicida Risbec, andTrichogrammatoidea eldanae Viggiani (Trichogrammatidae). Egg parasitization ranged from 13.4 to 41.5%. The only egg parasitoid detected onE. saccharina wasTelenomus applanatus Bin and Johnson, which inflicted only 5% parasitization.     

The biology and behaviour ofIphiaulax varipalpis [Hymenoptera: Braconidae] as a parasite ofDirphya nigricornis [Coleoptera: Cerambycidae]

The ability of the braconid parasite,Iphiaulax varipalpis Cary to control the beetleDyrphya nigricornis Olivier was evaluated. Field collected samples and specimens reared in polyethylene paper tubes under laboratory conditions (23.0°C±1.0 at 70% r.h) were used. Field parasitism was low (10.72%) while laboratory parasitism was high (57.66%). The parasite detected the hosts very easily in the laboratory. This ability is minimised in thick canopies ofCoffea arabica L. Host colonization was brisk (90 seconds) and confined to a near absolute area of discovery, measuring 4.18±0.41 cm. The parasite reproduces gregariously with female lifespan being approximately double the male period. The parasites are very active at the age of 10 days. As they age their potential fecundity (232 oocytes) reduces drastically with oviposition.      

Trichogramma egg parasitism ofHelicoverpa armigera on short-duration pigeonpea intercultured with sorghum

The levels of egg parasitism byTrichogramma spp. (Hymenoptera: Trichogrammatidae) on populations ofHelicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were recorded on sorghum (Sorghum bicolor L.) and on two flushes of flowers on short-duration pigeonpea (Cajanus cajan L.).H. armigera oviposition was concentrated on the early flowering stage of sorghum and the flowering and early podding stages of both flushes of pigeonpea. Parasitism on sorghum increased rapidly as egg density increased and reached a peak of 74.6%. Parasitism on pigeonpea was concentrated onH. armigera eggs laid on the first flush of pigeonpea flowers with a maximum of 69.2%. These high levels of parasitism on pigeonpea coincided with the period of parasite activity on sorghum. The levels of parasitism then declined rapidly and only very low levels were detected on a second flush of flowers. This rapid decline resulted in the overall egg mortality caused byTrichogramma on pigeonpea to be low, with a maximum of 7.8% caused by parasitism, compared to 34.4% on sorghum. The pattern of parasitism suggests that a transfer of parasites occurred from sorghum to pigeonpea. The rapid decline of parasitism on the pigeonpea indicates that parasite populations cannot be sustained on pigeonpea once the influx from sorghum stops. The results are discussed in terms of a possible method of encouraging the transfer of parasites from sorghum to short-duration pigeonpea by producing a more continuous cropping environment.     

First observations on the parasitoids associated with lepidopterous pests of cotton in Burkina faso

A study was conducted in Burkina Faso from 1991 to 1994 on the parasitoids associated with the following lepidopterous pests of cotton:Helicoverpa armigera (Hübner),Earias spp.,Diparopsis watersi (Rothschild),Spodoptera littoralis (Boisduval),Syllepte derogata (F.) andAnomis flava (F.). Thirty-nine primary parasitoid species and ten secondary parasitoid species were collected. The mean annual parasitism rates were lower than 20%, except forS. derogata pupae (42.9%). Maximum weekly parasitism rates could be high, with 61.5% recorded forS. derogata pupae and 32.9% forH. armigera larvae. The highest parasitism rates were found forMeteorus laphygmarum Brues (Braconidae) onH. armigera, Xanthopimpla aliena Krieger (Ichneumonidae),Brachymeria olethria (Waterston) andB. citrea (Steffan) (Chalcididae) onS. derogata, Aleiodes dedivus (Szépligeti),Dolichogenidea sp. (Braconidae) andBrachymeria feae Masi onEarias spp., an unidentified Tachinidae onA. flava andMetopius discolor Tosquinet (Ichneumonidae) onS. littoralis. Secondary parasitoids are mainly associated withApanteles spp. (Braconidae) which parasitizeS. derogata larvae. Some species of these secondary parasitoids such asNesolynx phaeosoma (Waterston),Pedobius amaurocoelus (Waterston) (Eulophidae) andAphanogmus fijiensis (Ferrière) (Ceraphronidae) may also attack certain Braconidae or Chalcididae that are primary parasitoids of other lepidopterous pests.     

Greenhouse whitefly control through the combined use of the colour attraction system with the parasite waspEncarsia formosa [Hym.: Aphelinidae]

The combined use of colour attraction (yellow sticky plates) andEncarsia formosa (Gahan) parasites reduced the greenhouse whiteflyTrialeurodes vaporariorum (Westwood) population in a spring tomato crop to an extremely low level. Whiteflies were strongly attracted to yellow sticky plates while the parasite,E. formosa, was not attracted so long as suitable and sufficient hosts were present. As the numbers of whiteflies declined, parasites were increasingly trapped by the plates. The percent parasitization increased continuously during the experiment, reaching about 90%, indicating the complete compatibility of colour attraction and biological control.