Some interactions ofSerratia marcescens nucleopolyhedrosis virus andBlepharipa pratensis [Dip.: Tachinidae] inLymantria dispar [Lep.: Lymantriidae]

The entomopathogensSerratia marcescens Bizio and nucleopolyhedrosis virus were each fed alone and in combination with the parasiteBlepharipa pratensis (Meigen) to 4th-instar gypsy moth,Lymantria dispar, (L.) larvae. At LD₃₀ for NPV, the presence of the parasite enhanced polyhedrosis about 30%, but the total number of gypsy moth larvae and pupae killed (85%) was not significantly different from the number killed by the parasite alone (93%). When the parasite was combined withS. marcencens, a strain nonpathogenic inL. dispar, total mortality was not significantly different from that in insects exposed only to the parasite (89 and 86%, respectively), but parasite survival was reduced about 12%. However, deaths not attributable to the parasite could not be ascribed to the bacterium either.     

Potential ofGeocoris punctipes [Hemiptera: Lygaeidae] andNabis spp. [Hemiptera: Nabidae] as predators ofEpilachna varivestis [Coleoptera: Coccinellidae]

Predation byGeocoris punctipes (Say) andNabis spp. onEpilachna varivestis Mulsant was studied in the laboratory at 26.7°C and in field cages containing soybeans. Both predator groups fed uponE. varivestis eggs, 1st, 2nd and 3rd stage larvae, but not upon 4th stage larvae, pupae, or adults. G. punctipes females produced significantly fewer eggs when fedE. varivestis eggs or 1st stage larvae than those fedGalleria mellonella (L.). Longevity of maleG. punctipes was significantly reduced when fedE. varivestis eggs; however, female longevity was not affected. Results from field cage tests indicated bothG. punctipes andNabis spp. could significantly reduce the density ofE. varivestis.     

The pathogenicity of an entomopoxvirus fromOthnonius batesi [Col.: Scarabaeidae] and its possible use as a control agent

In a natural population ofOthnonius batesi Oll. at Glen Innes, N.S.W., 4.0% of larvae in 1972 and 2.2% in 1973 were exhibiting symptoms of virus infection, whilst 0.8% of pupae and adults from the same population were infected in 1972. These figures, and field observations of infected larvae, suggested that the pathogenicity of the virus was low. In laboratory experiments withO. batesi the infection had little effect on mortality, and no significant effect on duration of the first instar, food intake, or larval growth. The vast accumulation of virus in the fat body probably results in mortality prior to, or during, the pupal period. Temperature had a marked effect on both % infection (optimum 30°C) and production of viral spheroids (optimum 25°C). Very little viral development occurred below 20°C. In a host range study onlyO. batesi, Rhopaea verreauxi Blanch. andR. morbillosa Blkb. were infectedper os. The possible use of the virus as a control agent is discussed.     

Vectoring gypsy moth nuclear polyhedrosis virus byApanteles melanoscelus [Hym.: Braconidae]

Gypsy mothLymantria dispar L. larvae were exposed toApanteles melanoscelus (Ratzeburg) females contaminated with nuclear polyhedrosis virus. Three methods of contamination (ovipositor, total body surface, and exposure to infected hosts) and two exposure periods (2 and 24 hours) were tested. A significantly greater incidence of larval mortality caused by virus occurred among larvae exposed to contaminated than among larvae exposed to uncontaminated parasites for 2 and 24 hours. No significant differences occurred in larval mortality caused by virus for the 3 methods of contamination for the 2- and 24-hour tests or in parasite emergence from larvae parasitized by contaminated or uncontaminated parasites.     

Incidence of parasites ofLymantria obfuscata [Lymantriidae: Lepidoptera] in Kashmir

Incidence of parasites ofLymantria obfuscata Walker [Lymantriidae: Lepidoptera] was studied in Kashmir during 1983 and 1984. The only egg parasite reared wasAnastatus kashmirensis Mathur parasitising between 4.49 to 11.92 percent of eggs. From 15 study sites as many as 10475 larvae of different stages and pupae were collected and reared in laboratory.Exorista rossica [Tachinidae: Diptera] was recorded to parasitize upto 8.42 per cent of larvae compared to 0.89 percent byCompsilura sp.Tetrastichus sp. [Eulophidae: Hymenoptera] was observed to be most dominant of the 6 pupal parasites, accounting for 33.41 percent of the measured parasitism, followed byPimpla sp. [Ichneumonidae: Hymenoptera] andTheronia atalantae atalantae [Ichneumonidae: Hymenoptera] which parasitized 6.84 and 4.03 per cent of pupae respectively.Brachymeria intermedia Nees [Chalcididae: Hymenoptera] was recorded to parasitize upto 2.98 per cent whereasBrachymeria lasus Walker recorded for the first time in Kashmir was found to parasitize up to 2.01 per cent, but was not widely distributed in the State.     

Biological control of the oil palm pestLatoia viridissima [Lepidoptera,limacodidae], in Cote d'Ivoire,by a new picornavirus

Among the major oil palm pest insects in the Côte d'Ivoire,Latoia viridissima Holland [Lepidoptera, Limacodidae] is the most frequently observed defoliator. During a pullulation of this species, a natural epizootic permitted us to demonstrate the occurrence of a small isometric RNA virus of 30nm in diameter. The buoyant density of the virus particles was 1.34. The virus capsid contained 2 major proteins with molecular weights of 30,000 (55%) and 31,000 (20%) and 3 minor proteins. One genome component was detected with molecular weight 2,9×10⁶. Agarose gel diffusion tests showed this virus was distinct from any other described insect Picornavirus. Trials with different doses of viral suspensions were tested on industrial oil palm plantation, allocated byL. viridissima, from ground level, using an automatic air carried sprayer. One week after the treatment, a mortality gradient, increasing from 11 to 61% according to the dose applied, was obtained. Two weeks after the treatment the mortality reached 92% of the larvae in the treated parcels. During the next generation, the number of caterpillars on the same parcel was very low.     

A laboratory study of the interaction of two parasites ofLymantria dispar [Lep.: Lymantriidae]: Blepharipa pratensis [Dipt.: Tachinidae] andBrachymeria intermedia [Hym.: Chalcididae]

In the laboratory, pupae ofLymantria dispar (L.) parasitized byBlepharipa pratensis (Meigen) were exposed to femaleBrachymeria intermedia (Nees) to determine whether the females would attack such pupae, and if they did, what was the fate ofB. pratensis. B. intermedia did attack parasitized pupae, andB. pratensis survived these attacks about 78% of the time. However, in those cases whereB. pratensis appears not to have survived, butB. intermedia did survive, the evidence suggests that the host pupae had not been parasitized byB. pratensis at the time of attack. Field observations also support the conclusion thatB. intermedia is not a significant mortality factor ofB. pratensis.     

Larval descriptions and biology ofTephritis dilacerata [Dip.: Tephritidae], a candidate for the biocontrol ofSonchus arvensis in Canada

The immature stages ofTephritis dilacerata Loew are described. Newly emerged males become sexually mature in about 1 week; females in 2–5 weeks. Courtship is described. Mated females lay eggs in groups of 6–7 into unopenedSonchus arvensis L. flower buds. The fly weaves the ovipositor between the bracts into the bud so that the release of latex is avoided. The length of the ovipositor corresponds to the length of the oviposition route. At 24 °C the eggs hatch in 4–5 days and the larvae mature in an additional 9–10 days. The larvae transform the bud into a simple gall and consume developing ovaries and receptacle. Attacked buds rarely flower and therefore do not produce seed. Pupation lasts about 2 weeks. The flies overwinter as adults in Europe, but no diapause occurred in the laboratory. The growth of the gall affects larval survival and when food is scarce some larvae develop at the expense of others. The European distribution of the fly is illustrated.T. dilacerata is considered a promising biocontrol agent forS. arvensis in Canada.     

Disease-parasitoid relationships in natural populations ofLymantria dispar [Lep.: Lymantriidae] in the Northeastern United States

ImmatureLymantria dispar L. were collected from 6 geographically distinct populations over 2 years to determine correlations between parasitoid and disease incidences. Incidence of the nuclear polyhedrosis virus disease (NPV) was found to be positively correlated with incidences of the parasitoidsApanteles melanoscelus (Ratzeburg) andParasetigena silvestris (Robineau-Desvoidy).     

Response of Galleria mellonella (Lepidoptera: Pyralidae) and Tenebrio molitor (Coleoptera: Tenebrionidae) to Spiroplasma citri inoculation

Injections into 4th instar larvae of Galleria mellonella using either in vitro or in vivo inoculum of the BR-6 isolate of Spiroplasma citri, propagated for one to nine passages, caused 5.7 to 24.7% mortality. Weight gain of the larvae injected at their 4th, 5th, and 6th instar was reduced in the first 4 days after inoculation but final pupal weight of the survivors was not significantly affected. Fourth instar larvae pupated within 10 days after the injection, but more larvae (6–13%) injected with 5th- to 9th-passage cultures pupated 5 or more days later than did larvae injected with 1st to 4th-passage cultures (0–3%). As many as one-third of the injected larvae developed into deformed pupae, with some external appendages missing or with a reduced and distorted thorax or abdomen with uneven tanning of the integument. Spiroplasma multiplied to dense concentrations (10⁸ to 10⁹/ml) in hemolymph smears from injected larvae incubated under oil. Larvae of Tenebrio molitor were not susceptible to S. citri by injection or feeding and G. mellonella were not susceptible by feeding. Transmissibility of S. citri by leafhopper vector to celery and periwinkle plants was retained after propagation for nine successive passages during 7 months in a nonhost insect such as Galleria.     

Transmission of a nuclear polyhedrosis virus inHeliothis zea [Lep.: Noctuidae] larval populations on soybean

Transmission of a nuclear polyhedrosis virus (NPV) inHeliothis zea (Boddie) on soybean was examinated. Artificial infestations ofH. zea were established at densities of 6.5, 19.5 and 58.5 larvae/row-m. Additional larvae infected to die from NPV in the 2nd stage were released into subplots to simulate 5 and 25% mortality levels. Virus transmission from infected to noninfected larvae was correlated with the initial incidence of infection in the population but not the density of larvae/row-m. Deposition of virus on plants from cadavers of larvae that died of virus infection was correlated with the initial incidence of infection in the populations and the density of larvae/row-m. After pupation of larvae in the 1st population, noninfected larvae only were again released to examine transmission of viral inoculum remaining on plants and soil. The percent mortality of larvae collected from the 2nd release was low and did not differ significantly between treatments. The concentration of virus on foliage and in soil after the 2nd release was directly correlated with density of larvae/row-m but not the incidence of infection within the population in the 1st release. This material is based upon work supported in part by the U.S. Department of Agriculture under Agreement N^o 82 CRSR-2-1000.     

Prey selection and baculovirus dissemination by carabid predators of Lepidoptera

Abstract.

• 1 The interaction between coleopteran predators and baculovirus-infected larvae was studied in the laboratory and the field in order to assess the potential role of predators in the dissemination of a nucleopolyhedrovirus (NPV).
• 2 Preference tests using three carabid species, Harpalus rufipes De Geer, Pterostichus melanarius Illiger and Agonum dorsale Pont, showed no evidence of discrimination between healthy and diseased larvae of the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae) as prey items.
• 3 Virus infectivity was maintained after passage through the predator's gut. NPV mortality ranged from 97% to 20% when test larvae were exposed to faeces collected immediately after and 15 days post-infected meal respectively.
• 4 The potential for transfer of inoculum in the environment was estimated in the laboratory by soil bioassay. Carabids continuously passed infective virus to the soil for at least 15 days after feeding on infected larvae.
• 5 Field experiments showed that carabids which had previously fed on diseased larvae transferred sufficient virus to the soil to cause low levels of mortality in larval populations of the cabbage moth at different instars.

     

The effect of gypsy moth metamorphosis on the development of nuclear polyhedrosis virus infection

The development of nuclear polyhedrosis virus (NPV) infection in gypsy moth (Lymantria dispar) was studied before, during, and after host metamorphosis, and in larvae and pupae in the subsequent generation, to determine whether NPV ingested by late instars can replicate in host tissues through metamorphosis and whether it can be vertically transmitted to progeny. Individuals that survived sublethal dosages of NPV did not differ from undosed insects in pupal weight, fecundity, larval and pupal weight of progeny, or response of progeny to NPV challenge. No evidence of NPV infection or of abnormal histology was found in adult tissues examined by light microscopy and no virus was detected on the surface of eggs produced by NPV-treated moths. No NPV-caused mortality was recorded among undosed progeny of dosed or undosed parents. The progeny of dosed parents were neither more resistant nor more susceptible to LdMNPV than were progeny of undosed parents and lethal times did not differ between groups. Examination of larval, pupal, and adult tissues by DNA hybridization revealed that insects in which NPV DNA was detected died prior to adult eclosion. NPV was not detected in any hosts surviving to the adult stage. These results suggest that survivors of sublethal dosages of NPV avoid infection and are therefore incapable of vertically transmitting infectious virus to progeny.     

Microbial control of the fruit tree leafroller,Archips argyrospila [Lep.: Tortricidae] in California

Field populations of larvae of the fruit tree leafrollerArchips argyrospila (Wlk). were practically eliminated following spray application ofBacillus thuringiensis Berliner serotype III at 192 and 80×10⁶ I.U. per litre on the host trees,Cercis occidentalis. Spray applications of lower rates ofB. thurienginsis serotype III at 18.9 and 32.1×10⁶ I.U. per litre and mist application ofB. thuringiensis serotype 1 at 8.0 and 16.0×10⁶ I.U. per litre gave partial control of populations ofA. argyrospila larvae. A granulosis typeBaculovirus, applied by hand sprayer at 1.4×10⁹ granules/ml produced approximately 50% reduction of 5th instarA. argyrospila larvae onC. occidentalis trees. It was concluded thatB. thuringiensis and the granulosis typeBaculovirus are promising control agents forA. argyrospila larvae.     

Infection of the gypsy moth,Porthetria dispar with the entomogenous fungus,Conidiobolus coronatus

Fourth instar larvae of the gypsy moth,Porthetria dispar (L.) were infected with the fungusConidiobolus coronatus (Cost.) Batko using the spore shower technique for varying periods of time. Larvae treated for more than 20 minutes showed 100% mortality. Virulence of the pathogen was increased by inoculating larvae of the wax moth,Galleria mellonella (L.) three times in serial succession. Typical symptoms of the infection were lightening of color, flaccidity, shrinking and finally desiccation of the larvae. Observations on the histopathology of infected larvae showed penetration of the integument by hyphae within 22 hours after inoculation and at 34 hours post inoculation, the hemocoel, head, nervous system and muscles were completely infected. A localized mycelial growth in the digestive system resulted probably due to the ingestion of spores, but penetration of the gut wall was not recorded.     

Effect of 3 insect growth regulators on larval development,fecundity and egg viability of the coccinelidChilocorus bipustulatus [Col.: Coccinelidae]

The effect of 3 insect growth regulators — methoprene, diflubenzuron and RO 13-5223, on the coccinelidChilocorus bipustulatus L. was studied in the laboratory. Feeding onChrysomphalus aonidum (L.) orAspidiotus hederae Vallot (Diaspididae) treated with the IGRs at the concentration of 0.025% a.i. revealed the following: diflubenzuron caused a complete mortality of 1 st instar larvae; methoprene and RO 13-5223 did not arrest larval development but inhibited pupation; fecundity of sexually mature females was not affected by the 3 IGRs but egg hatch was completely inhibited; egg viability was regained when IGR-exposed females had been transferred to an uncontaminated environment.     

Studies on the application of a nuclear polyhedrosis virus to control populations of the Egyptian cottonworm, Spodoptera littoralis

Variations in the resistance to nuclear polyhedrosis virus (NPV) were found in three populations of Spodoptera littoralis. The LD₅₀ for the most resistant population was 1.07 × 10⁴ PIB/5th instar larva as compared to 8.4 × 10² and 5.8 × 10² PIB/larva in the other two populations. The effect of NPV persisted in larvae which survived and pupated. Some of the pupae died, and those which survived produced normally shaped adults. While fecundity was sharply reduced in the less resistant populations, the effect on the most tolerant population was less pronounced. A 3-year-old inoculum, stored unprotected from daylight and without cooling, was much less effective even against the most sensitive larval population as compared to a relatively fresh and refrigerated batch. Larvae in their 6th instar proved to be approximately 10-fold more resistant to the NPV than 5th instar ones, while the difference in weight was only about twice. These variations in resistance to NPV are also discussed from the point of view of applying S. littoralis NPV in pest control schemes.     

Assessment ofBacillus thuringiensis serotype 14 andSteinernema feltiae [Nematoda: Steinernematidae] for control of theSimulium vectors of onchocerciasis in Mexico

Field evaluations ofBacillus thuringiensis Berliner serotype 14 and the nematodeSteinernema feltiae Filipjev 1934 (=Neoaplectana carpocapsae) were conducted againstSimulium ocharaceum Walker and other simuliid vectors of onchocerciasis in Mexico.B. thuringiensis was highly toxic, causing up to 100 % larval mortality, but only for short distances downstream. Increased dosage did not enhance downstream carry ofB. thuringiensis. Highest rates of mortality were recorded against early instar larvae. Stream treatment withS. feltiae did not result in significant larval mortality because the infectivestage nematodes were either not ingested or were injured during ingestion by the larval mouthparts.     

Experimental studies on parasitization byApanteles Glomeratus V. Relationships between growth rate of parasitoid and host age at the time of oviposition

The growth and development ofApanteles glomeratus L. eggs and larvae in the host larva (Pieris rapae crucivora Boisduval) was investigated by calculating their volume. WhenA. glomeratus eggs increase 90 fold in volume after being laid, larvae hatch from them. The larvae grow exponentially and the growth rate of the parasitoid is dependent on the host stage. Being laid in the 1st instar host, the parasitoids grow more slowly than those laid in 2nd–4th instar host. A pupal host stage prevents the parasitoids’ development. When larvae exceed the threshold size of 5.0×10⁸ μ³, they enter the 2nd instar. A few days after they attain the maximum size of 3.3×10⁹ μ³, they moult and egress from the host body.     

Contact toxicity of some chemical and biological pesticides to several insect parasitoids and predators

Eight pesticides; methyl parathion, malathion (organo-phosphates), toxaphene (chlorinated hydrocarbon), carbaryl (carbamate), pyrethrin (plant derivative),Bacillus thuringiensis, nuclear polyhedrosis virus (Heliothis) (microbial insecticides), and 2,4-DB (postemergence herbicide) were evaluated at the minimum recommended field dose and reduced dosages for contact toxicity toBrachymeria intermedia (Hymenoptera: Chalcididae), Campoletis sonorensis (Hymenoptera: Ichneumonidae), Chelonus blackburni (Hymenoptera: Braconidae), Meteorus leviventris (Braconidae), Voria ruralis (Diptera: tachninidae), Chrysopa carnea (Neuroptera: Chrysopidae), andHippodamia convergens (Coleoptera: Coccinellidae). At minimum field dosages, percent mortality of parasitoids and predators was>27%, for the chemical insecticides. Mortality from pyrethrin was <31%, in all cases and 0% for 5 of the 8 species tested. Mortality of parasitoids and predators exposed toB. thuringiens is and NPV was<4% while mortality from 2,4-DB was<7%. The toxicity of chemical insecticides to parasitoids and predators at reduced dosages in increasing order of toxicity was malathion > carbaryl > toxaphene > methyl parathion.