Dosage-mortality and time-mortality studies of a granulosis virus in a laboratory strain of the codling moth,Laspeyresia pomonella

Different doses of a granulosis virus were administered to first- and fifth-instar larvae of the codling moth Laspeyresia pomonella. Virus was very pathogenic for both larval instars. The LD₅₀ values for first- and fifth-instar larvae were 5 and 49 capsules/larva, respectively. However, fifth-instar larvae were much more variable in their response to virus than first-instar larvae. Using probit methods it was calculated that 1 capsule could cause death in about 25% of both larval instars but 1578 capsules were required to cause 70% mortality of fifth-instar larvae as compared to 12 capsules for first-instar larvae. This is the first report of a decided difference in variability of response to virus by two larval instars of the same species. A bimodal response by both larval instars was observed in time-mortality studies. Apparently, about 20% of the larvae were very resistant to virus infections.     

颗粒体病毒在小菜蛾种群中的垂直传播方式的初步观察

在室内观察了小菜蛾颗粒体病毒PlutellaxylostellaGranulosisVirus(RxGV)在小菜蛾种群水平上可能的垂直传播途径。结果表明 :(1 )上代小菜蛾Plutellaxylostella(L .)幼虫期饲毒不能将小菜蛾颗粒体病垂直传递到下代 ;(2 )取食病毒的雌蛾产的卵所孵化的幼虫中 ,没病毒感染出现 ,说明病毒不能经小菜蛾成虫体内传播到下一代。 (3 )用小菜蛾颗粒体病毒处理卵卡时 ,其初孵幼虫有少量被病毒感染死亡 ,浓度高时感染率也较高 ,但感染率均在 1 0 %以下 ,说明小菜蛾颗粒体病毒能经卵表垂直传递给下代 ,但传递效率不高。但当用病毒处理叶片上的卵时 ,初孵幼虫死亡率高达 77 73 % ,而且孵化出的幼虫大多数染病且死于 3龄以前 ,因此田间病毒的施用时间可提早到卵高峰期。     

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.     

Mortality factors affecting immature stages of codling moth,Cydia pomonella (Lepidoptera: Tortricidae), and the impact of parasitoid complex

Codling moth, Cydia pomonella Linnaeus (Lepidoptera: Tortricidae), is a serious pest of apples worldwide. This study aimed to evaluate the mortality rate of codling moth eggs, larvae and pupae in the field in commercial and neglected apple and walnut orchards over two years, and to investigate the biodiversity and intensity of parasitoids associated with codling moth in the orchards. Five patches of wax paper containing 1-day-old codling moth eggs were placed in a neglected orchard in order to evaluate parasitism rates. Corrugated cardboard bands were placed around the trunk of 15 trees during late spring and the beginning of summer through to fruiting season to capture and measure parasitism of codling moth larvae. 5285 larvae in total were collected during this study. Mortality rate (egg?+?larvae?+?pupae) varied between the commercial and neglected orchards, reaching a maximum of (42.89% and 66.67%) in neglected apple orchards and (61.03% and 74.76%) in the neglected walnut orchard in 2003 and 2004, respectively. Trichogramma cacoeciae (Hymenoptera: Tichogrammatidae) was the only egg parasitoid recorded. Eight hymenopteran larval and pupal parasitoids belonging to several subfamilies were recorded: Cheloninae, Agathidinae, Cremastinae, Haltichellinae, Chalcidinae, Anomalinae, and Pteromalinae and one dipteran belonging to Tachininae. In conclusion, mortality factors, mainly by parasitoids, are contributing to a general reduction in codling moth larvae populations particularly in neglected orchards. The hymenopteran Ascogaster quadridentata and the dipteran Neoplectops pomonellae can contribute to biological control programmes against codling moth in the coastal region and other regions.     

The transstadial and vertical transmission of a granulosis virus from the corn borer Sesamia nonagrioides

The effects of a granulosis virus from Sesamia nonagrioides were established in the larval, pupal, and adult stages. Different ages of larvae were compared as to their survival rates. Pupae deriving from diseased larvae had a sex ratio that deviated from the expected 1:1; in some of these pupae an incomplete pigmentation was noticed in abdominal segments. Adults deriving from inoculated larvae were less fertile, as measured by oviposition and by hatching rate. Offspring of inoculated parents had a greater incidence of the granulosis virus disease than did offspring of uninoculated parents.     

A synopsis of the obligate and facultative insect parasitic nematodes

A study of the pathogenicity of a cytoplasmic polyhedrosis virus of the gypsy moth, Porthetria dispar, was conducted. Third- and fourth-instar larvae were highly susceptible to the pathogen even when fed low dosages of polyhedra. Only 30–50% of the treated insects died of polyhedrosis, but the debilitating effects of the virus on larval and postlarval stages were remarkable. Pupal weights were consistently reduced. An inverse and, respectively, a direct, relationship was found between the size of diseased specimens and the developmental periods of larvae and pupae surviving to lethal infection. The highest infected male adults showed a lighter wing coloration. Structural abnormalities and melanotic abdominal inclusions, recorded in diseased adults, were more frequent in females than in males. The presence of melanotic inclusions in diseased females obtained from early larval infection experiments was associated with a greater pupal weight. Lower dosages were the most effective in producing larval mortality and reducing pupal weights and adult emergence. An interference phenomenon due to a mixed virus infection is suspected.     

Production and field evaluation of codling moth granulosis virus for control of Cydia pomonella in the United Kingdom

Codling moth granulosis virus (Cp GV) was produced in larvae of Cydia pomonella reared on artificial diet. The average yield of virus (9 × 10⁹capsules/larva) was increased by raising the larvae on diet containing methoprene, a juvenile hormone analogue. In field trials in 1978 and 1979, one or two high-volume applications of Cp GV at 7 × 10¹⁰ capsules/litre achieved reductions in numbers of mature larvae and damaged fruit that were little different from those obtained by two applications of azinphos-methyl. A field trial in 1980 showed that at concentrations of Cp GV ≥ 6 × 10⁸ capsules/litre, damaged diminished slowly with increasing virus concentration. Following virus application in 1980, Cp GV infectivity was reduced by half in 3 days, but some activity persisted at least 4–8 wk after spraying. The results indicate that codling moth GV is an effective control agent particularly in reducing numbers of larvae and the more severe forms of fruit damage.     

The susceptibility of the pea moth, Cydia nigricana, to infection by the granulosis virus of the codling moth, Cydia pomonella

Laboratory studies demonstrated that neonate larvae of the pea moth, Cydia nigricana, are susceptible to infection with a granulosis virus (CpGV) isolated from the codling moth, Cydia pomonella. Comparative LC₅₀ values for C. nigricana and C. pomonella are 1.90 × 10⁵ and 1.54 × 10⁴ capsules/ml of diet, respectively. The virus extracted from CpGV-infected pea moth larvae is serologically related, and probably identical, to CpGV.     

Integrated control of apple pests in New Zealand 10. Population dynamics of codling moth in Nelson

Abstract

Sampling methods are described for estimating the population density, mortality, and natality of a univoltine population of codling moth attacking mature apple trees (cv. ‘Delicious’) at Nelson, New Zealand. These methods were used to construct life tables for the species over eight generations (1967–68 to 1974–75) on trees variously sprayed and not sprayed with ryania in an integrated control programme. Bait traps provided a sensitive measure of seasonal adult population density. Analysis of the life tables shows that migration of adults was the main key factor and that overwintering larval mortality (particularly that due to bird predation), fecundity, and ryania also made a major contribution to variation in generation mortality. In the absence of ryania the resident population usually increased between generations, whereas it usually decreased when ryania sprays were applied. The density dependence of overwintering larval mortality was due to bird predation, and the inverse density dependence of larval mortality from ryania was due to changes in the site of fruit entry with larval population density. Fecundity was density independent, and inconclusive evidence was obtained on the density dependence of migration. The wide variation in fecundity is attributed primarily to weather conditions. The impact on control strategy of the above key factors, density dependence, and total natural mortality is discussed. Ryania is found to be uneconomic, whereas the granulosis virus of codling moth and male removal with pheromone traps show promise as future control methods. The need to eliminate reservoirs of codling moth close to orchards under integrated pest control is emphasised. Regulation of codling moth populations at Nelson on neglected, unsprayed trees appears to result from intraspecific competition for fruits and cocooning sites, and weakly density-dependent mortality of mature larvae when seeking cocooning sites and while overwintering in their cocoons. Variation in fecundity also cohtributes to fluctuations in abundance of the species. In contrast, at low density in an integrated control programme no intraspecific competition was evident; migration, winter mortality, and fecundity were the main determinants of abundance. This illustrates the need to study pest populations at densities similar to those tolerable commercially.     

Predation of codling moth Cydia pomonella L. by the Silvereye Zosterops lateralis (Latham)

Predation of cocooned larvae of codling moth Cydia pomonella by silvereyes Zosterops lateralis was studied in an apple orchard in Nelson, New Zealand. Apple logs with known larval densities were made available to the birds for known periods of time, either in cages or exposed in the apple orchard. The numbers of silvereyes and the natural predation of codling moth were recorded in the same orchard. Predation was density dependent. On caged logs with an initial high density of 32 larvae, 1.1 larvae were consumed per bird‐hour; in contrast, one larva was consumed per 34.5 bird‐hours at three larvae per log. A curvilinear relationship was demonstrated between larval density and the bird‐hours required for predation; this relationship was consistent with the known density dependence of silvereye predation of codling moth. A regression of the total annual winter bird predation of larvae in the orchard on bird numbers was significant. However, the density dependence of predation resulted in declining rates of predation over the winter as larval density declined; the first birds to arrive in the orchard benefitted from particularly high predation rates. As a consequence, fluctuations in bird numbers during the winter had only a secondary influence on predation rates. The numbers of silvereyes in the orchard showed no relationship to the density of the codling moth population present. This study confirmed the importance of silvereyes in the predation of codling moth and a functional, not numerical, rseponse of these birds to codling moth density.     

Life stage toxicity and residual activity of insecticides to codling moth and oriental fruit moth (Lepidoptera: Tortricidae)

The codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are two key pests of apple (Malus domestica Borkh.) in North Carolina. Growers extensively relied on organophosphate insecticides, primarily azinphosmethyl, for > 40 yr to manage these pests. Because of organophosphate resistance development and regulatory actions, growers are transitioning to management programs that use new, reduced-risk, and OP-replacement insecticides. This study evaluated the toxicity of a diversity of replacement insecticides to eggs, larvae, and adults, as well as an assessment of their residual activity, to codling moth and oriental fruit moth. Laboratory-susceptible strains of both species were used for all bioassays. Fresh field-harvested apples were used as a media for assessing the ovicidal activity of insecticides. For larval studies, insecticides were topically applied to the surface of lima bean-based diet, onto which neonates were placed. Toxicity was based on two measures of mortality; 5-d mortality and development to adult stage. Ovicidal bioassays showed that oriental fruit moth eggs were generally more tolerant than codling moth eggs to insecticides, with novaluron, acetamiprid, and azinphoshmethyl having the highest levels of toxicity to eggs of both species. In contrast, codling moth larvae generally were more tolerant than oriental fruit moth to most insecticides. Methoxyfenozide and pyriproxyfen were the only insecticides with lower LC50 values against codling moth than oriental fruit moth neonates. Moreover, a number of insecticides, particularly the IGRs methoxyfenozide and novaluron, the anthranilic diamide chlorantriliprole, and the spinosyn spinetoram, provided equal or longer residual activity against codling moth compared with azinphosmethyl in field studies. Results are discussed in relation to their use in devising field use patterns of insecticides and for insecticide resistance monitoring programs.     

A model of the effect of codling moth granulosis virus on Cydia pomonella

A model was developed based on an initial ingestion phase, followed by a period of virus multiplication and host death, to describe the effects of codling moth granulosis virus (CpGV) concentration and time from initial infection on the percentage of codling moth larvae (Cydia pornonella) dying from virus infection in the laboratory. With modification, this model also described the effect of CpGV concentration on the reduction of damage to fruit by C. pomonella larvae in the field. In both cases, the effect of CpGV increased with the l/10th power of virus concentration. LT₅₀ (time to death of 50% of larvae) was inversely related to virus concentration in the laboratory. The model predicts the threshold concentration for death of larvae, as well as LD₅₀(C₅₀ and LD₉₀(C ₉₀,) for all ages of larvae. The model also predicts that if the majority of larvae entered through the sides of apple fruits, rather than through the calyx or near the stalk (as they probably did in the field), then the efficacy of CpGV in reducing fruit damage would be lowered. This effect of site of entry is especially marked at low virus concentrations.     

Incidence and transmission of a granulovirus in a large codling moth [Cydia pomonella L. (Lepidoptera: Tortricidae)] rearing facility

Incidences of potential per os Cydia pomonella granulovirus (CpGV) transmission within a large codling moth colony were identified. CpGV was detected in the water which is used to wash egg sheets. When pre-neonates were extracted from eggs prior to emergence and tested for the presence of CpGV, 40% were found to carry amounts of CpGV detectable by a polymerase chain reaction (PCR) assay, suggesting possible transovarial transmission of the virus. Although symptoms typical of virus infection and larval death were found infrequently within communal rearing trays, the frequency with which CpGV DNA was detected by PCR assays increased from a mean of 31% of 10-day-old larvae to 94% of 25-day-old larvae. CpGV in codling moth cadavers remained virulent after being held at 60 degrees C for 3 days under conditions similar to the treatment of spent diet at the rearing facility before its disposal. PCR tests of surface samples taken from air filters and rearing rooms of the rearing facility were found to contain CpGV. Bioassays of surface samples from the diet trash bin and a filter through which outside air is passed before entering the rearing chambers resulted in significant codling moth neonate mortality. The virulence of CpGV in dust from the spent diet and the original inadvertent positioning of the diet trash bin directly below one of the air intake ducts are suggested as a possible additional source of CpGV contamination within the facility.     

Aseptic rearing of Epiphyas postvittana (Lepidoptera: Tortricidae) on a meridic diet

The light brown apple moth, Epiphyas postvittana (Walker), was reared aseptically from newly hatched larvae to adults for three generations on a meridic diet. Growth and development on this diet were comparable with that on oligidic diets and on host‐plants. At 25 ± 1°C, 50–60% R.H., and 12‐h photophase, the average larval period was approx. 28 days, pre‐pupal and pupal 11–12 days, and pre‐oviposition approx. 2 days; the incuva‐tion period of eggs was approx. 7 days. The average developmental period from egg to adult was thus about 49 days; 89 % of larvae reached the adult stage. The average fecundity was 598 eggs per female, and the sex ratio was nearly 1:1. There were no differences in the rate of development or in fecundity of insects reared on media with and without a mould inhibitor.     

Biological Control of the Potato Tuber Moth (Phthorimaea operculella Zeller) in the Republic of Yemen Using Granulosis Virus: Biochemical Characterization, Pathogenicity and Stability of the Virus

A granulosis virus infecting the potato tuber moth, Phthorimaea operculella, has been identified, isolated and purified from diseased potato tuber moth larvae collected from potato fields in the highland basin Qa al-Boun of the Republic of Yemen. The granulosis virus was propagated by feeding potato tuber moth larvae with potatoes treated with a concentration of one granulosis virus-infected fourth instar larva to 5l of water (corresponding to an occlusion body (OB) concentration of 2 106 OB ml-1). Restriction enzyme analysis of viral DNA revealed that the isolated virus seemed to correspond to an isolate from the Lima region of Peru. A median LC 50 value of 7.3 104 OB ml-1 was calculated for a purified virus preparation. Different preparations of the granulosis virus were investigated for their persistence in the field on tubers and leaves. A purified virus preparation (PoGV) applied to potato tubers and exposed in the open had a half-life of 1.3 days. On leaves, the activity of granulosis virus spray deposits of an unpurified virus preparation (PoGV I) and of a glycerine-formulated preparation (PoGV II) also declined with exposure time. Mortalities of potato tuber moth larvae of 43% for PoGV I and 49% for PoGV II were recorded when first instar larvae were fed with potato leaves collected 2 days after treatment. After 8 days, 25.8% of the larvae had died from PoGV I treatment and 19.4% from PoGV II. Neither preparation displayed any effect 17 days after application.     

Particle films for suppression of the codling moth (Lepidoptera: Tortricidae) in apple and pear orchards

Studies were conducted in 1997 and 1998 to evaluate the effects of three particle film formulations consisting of kaolin and adjuvants on neonate larvae, ovipositing adult females, and eggs of the codling moth, Cydia pomonella (L.). Neonate larval walking speed, fruit discovery rate, and fruit penetration rate on apple host plants coated with particle films were significantly lower than on host plants without particle films in laboratory assays. Females oviposited less on host plants covered with a particle film residue than on untreated plants in laboratory choice and no-choice tests. Hatch rate of codling moth neonate larvae was unaffected by particle films sprayed on host plants either before or after oviposition. Fruit infestation rates were significantly reduced on particle film-treated trees compared with untreated trees for both first- and second-generation codling moth in field trials in both apple and pear orchards. Particle films appear to be a promising supplemental control approach for codling moth in orchards where moth density is high, and may represent a stand-alone method where moth densities are lower.     

Shotgun proteomic analysis of wing discs from the domesticated silkworm (Bombyx mori) during metamorphosis

Proteomic profiles from the wing discs of silkworms at the larval, pupal, and adult moth stages were determined using shotgun proteomics and MS sequencing. We identified 241, 218, and 223 proteins from the larval, pupal, and adult moth stages, respectively, of which 139 were shared by all three stages. In addition, there were 55, 37, and 43 specific proteins identified at the larval, pupal, and adult moth stages, respectively. More metabolic enzymes were identified among the specific proteins expressed in the wing disc of larvae compared with pupae and moths. The identification of FKBP45 and the chitinase-like protein EN03 as two proteins solely expressed at the larval stage indicate these two proteins may be involved in the immunological functions of larvae. The myosin heavy chain was identified in the pupal wing disc, suggesting its involvement in the formation of wing muscle. Some proteins, such as proteasome alpha 3 subunits and ribosomal proteins, specifically identified from the moth stage may be involved in the degradation of old cuticle proteins and new cuticle protein synthesis. Gene ontology analysis of proteins specific to each of these three stages enabled their association with cellular component, molecular function, and biological process categories. The analysis of similarities and differences in these identified proteins will greatly further our understanding of wing disc development in silkworm and other insects.     

Fruit Bins Washed with Steinernema carpocapsae (Rhabditida: Steinernematidae) to Control Cydia pomonella (Lepidoptera: Tortricidae)

A bin washing apparatus (drencher) was used to treat late-instar codling moth, Cydia pomonella Linnaeus-infested wooden fruit bins with the entomopathogenic nematode Steinernema carpocapsae . Sentinel late-instar codling moth larvae were placed in strips of wood, made from dismantled bins, that were subsequently screwed into the corners of real bins before treatment. Pre-soaking the bins with water prior to treatment and covering the bins with a plastic tarp post-treatment, to maintain a high humidity, significantly increased sentinel codling moth mortality. Treatment for 1 min with 50 S. carpocapsae infective juveniles mL -1 water resulted in more than 80% mortality over 6 h in which the nematodes were continuously pumped through the drencher. The temperature of the water in the bin washer was ≤15°C and the chlorine in the city water was too low to harm the nematodes. The key disadvantage of washing the bins was the labour involved. It may be possible to reduce post-treatment holding time and increase codling moth mortality by holding the bins at a higher temperature post-treatment, however this parameter was not included in the study. The presence of the codling moth granulosis virus within the larvae did not influence the nematode-induced codling moth mortality over a range of concentrations and two temperatures in laboratory trials.     

The hormonal regulation of the larval diapause in the codling moth, Laspeyresia pomonella (Lep. Tortricidae)

The hormonal control of the facultative diapause of the codling moth has been investigated. The diapause can be divided into 4 phases or periods: (1) diapause induction by short-day conditions (SD) in young larvae, (2) initiation of the diapause in the early last larval instar by a high titre of juvenile hormone, (3) onset and maintenance of diapause with inactivity of the neuroendocrine system, as evidenced by the results of neck-ligation experiments, (4)termination of diapause by the production of ecdysteroid.Diapause-induced larvae pupated after spinning the cocoon, if the state of induction was changed by injection with the anti-juvenile hormone precocene II at the beginning of the last larval instar and subsequent results of neck-ligation experiments, (4) termination of diapause by the production of ecdysteroid. treated with juvenile hormone during the first 1.5 days after the last larval moult and subsequently reared under SD. Under LD, continuous application of juvenile hormone during the last larval instar and after spinning did not prevent the insects from moulting to either a supernumerary larva, a pupa or a larval-pupal intermediate. Termination of diapause, i.e. pupation, was achieved by injecting diapausing larvae with 20-hydroxyecdysone. Although juvenile hormone was found to have a prothoractropic effect in diapausing larvae, no pupal moult could be induced by the application of the hormone. Contrary to the hormonal situation before pupation of nondiapausing larvae, no juvenile hormone could be detected before or during the pupation of larvae after diapause.     

Selection of a strain of the granulosis virus of the codling moth with improved resistance against artificial ultraviolet radiation and sunlight

A six-step sequence of selection of the granulosis virus of Laspeyresia pomonella led to a strain with increased resistance to sunlight. Each step consisted of irradiation of dry deposits of the virus on apples with near range ultraviolet light, infection of freshly eclosed codling moth larvae with the irradiated virus, and propagation of the virus thus produced in large fifth-instar larvae. Compared with the original virus, the new strain was 5.6 times more resistant to artificial ultraviolet irradiation in the laboratory and remained twice as long infective in the field.