Third-generation Larvae Research Articles

Population Source of Third-Generation Oriental Armyworm in Jilin, China, Determined by Entomology Radar, Trajectory Analysis, and Mitochondrial COI Sequences.

The armyworm, Mythimna separata (Walker) (Lepidoptera: Noctuidae), is an important polyphagous pest with a strong migratory ability. Recently, third-generation larvae have become an increasingly serious pest threat in Jilin Province of northeast China. To investigate the population source of this species, scanning entomological radar observations and insect mitochondrial cytochrome oxidase I (COI) genes were used in this study. Five main results were found: (1) The peak period in captured second-generation moths was from mid to late July. The temperature and wind speeds were optimum for the moths to have migrated. Strong southwesterly winds occurred during the peak migration period. (2) Radar observations indicated that most of the moths’ migration took place at a height of 600 m, often in a dense layer which formed at heights of 350–800 m. (3) Analyses of adult ovarian development and larval haplotypes showed third-generation larvae were progeny of both locally produced progeny and immigrant moths. (4) Based on our back-tracking and haplotype analyses, immigration led to an outbreak originated in the same source area to the southwest. (5) Emigration of second-generation moths was confirmed by both radar observation and mtDNA analysis. Forward trajectories indicated that the moths were capable of immigrating far from their overwintering range. These results are useful for improving the forecasting systems of this insect pest species.

Phenotypic plasticity of the Cydalima perspectalis Walker life cycle stages development in the Crimea

The box tree moth ( Cydalima perspectalis Walker) is an invasive insect that has rapidly colonized the vast area of the European continent, damaging tonatural and ornamental box trees. In order to develop effective phytophagous control measures there are features of the local populations seasonal development that have been studied in the Crimea. It is determined that during the growing season in the green spaces of the Crimean parks there is a temporary overlapping of both development stages and generations of the C. perspectalis populations. An important seasonal adaptation of C. perspectalis to the habitat’s conditions is thermal sensitivity reduction and development acceleration of all life cycle stages in the second summer generation under the influence of photoperiod. This flexibility of ontogenetic requirements for the transition to diapause provides higher phenological variability in populations. There is identified the temperature and photoperiod impact to development rate of larvae and the influence of relative humidity to development rate of pupae. With identical thermal reaction norms for development of the overwintered larvae, for complete of life cycle of the one generation life cycle in the Southern coast of the Crimea conditions needed the sum of growing degrees-days are 80 °С higher than in the Foothill Crimea. It is identified relative constancy of growing degrees-days needed for complete of the second summer generation of C. perspectalis . It allows considering them as a tool for determining the timing of effective treatment of third-generation larvae before they cause severe damage. For the comparability of the research results with the available publications, it was proposed to use the temperature threshold of 9.5 °С when calculating the growing degrees-days.

Biology and Management of the Pecan Nut Casebearer (Lepidoptera: Pyralidae)

Abstract The pecan nut casebearer, Acrobasis nuxvorella Neunzig, is a key pest of pecan nut production throughout the pecan producing regions of the central and southwestern United States and northern Mexico. Economic loss is primarily due to first-generation larvae that feed internally in developing nutlets soon after pollination in the spring. Damage by second-generation and third-generation larvae can also result in economic loss. We summarize pecan nut casebearer distribution, life history, crop injury, and current management practices including orchard scouting, monitoring adult activity with pheromone traps, and chemical, biological and regulatory controls. Insecticides are the sole means of controlling pecan nut casebearer but must be properly timed to kill young larvae before they tunnel into pecan nuts. Effective management requires orchard scouting to assess egg abundance and nut entry by larvae to determine the need for and optimum timing of insecticide treatment. An on-line, degree-day model, PNCforecast, uses pheromone trap data to predict oviposition activity and optimum dates for sampling orchards to assess pecan nut casebearer egg infestations. This IPM program is enhanced by the availability of diacylhydrazine insecticides that are toxic to Lepidoptera larva but preserve beneficial insects that suppress secondary pests of pecans.

Odour and feeding preference of noctuid moth larvae conditioned to vanillin diet and non-vanillin diet

It is largely accepted that larval experience influence host-plant preference of larvae. In general, larval experience with a host plant induces both an odour and feeding preference for that plant. In a previous study, exposure of three noctuid stem borer species, i.e. Sesamia nonagrioides, Busseola fusca and B. nairobica, to a vanillin-enriched medium induced an olfactory preference for the odours of this medium in the larvae of these species. Here, we checked if the exposure to a vanillin-enriched medium also induced a feeding preference for this diet. Different life stages (i.e. neonate larvae to adults) of the three species were conditioned to an artificial diet enriched with vanillin over two generations. Thereafter, two-choice tests on third-generation larvae were done using a Y-tube olfactometer for odour preferences and diet choice experiments. Larvae of all three-species conditioned to the vanillin diet oriented significantly towards the odour of this diet, whereas the non-conditioned larvae did not. Still, apart for B. fusca, the conditioned larvae did not exhibit a feeding preference for this diet, thus odour preference did not match the feeding choice of the conditioned larvae. The implication of this result on insect’s adaptability to a new host plant in a changing environment is discussed.

Comparison of a sprayable pheromone formulation and two hand-applied pheromone dispensers foruse in the integrated control of oriental fruit moth (Lepidoptera: Tortricidae).

The efficacy of integrated programs using a sprayable pheromone formulation or one of two hand-applied pheromone dispensers, and a conventional oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae) control program, was compared using 4-5-ha blocks of peach orchard at three Niagara Peninsula farms during 2000-2002. In the integrated programs, chlorpyrifos and mating disruption with 3M Sprayable Pheromone, Isomate OFM Rosso, or Rak 5 hand-applied dispensers were used to control first-generation larvae, and mating disruption alone was used to control second- and third-generation larvae. In the conventional program, chlorpyrifos was used to control first-generation larvae, and pyrethroid insecticides were used to control larvae of the later generations. All programs were effective at maintaining fruit infestation by G. molesta below the industry tolerance level of 1%. An integrated program using sprayable pheromone required the use of more supplementary insecticide applications to control second- and third-generation larvae than a program using hand-applied dispensers. The elimination of insecticide sprays from integrated program blocks did not result in an increase in damage by plant bugs, Lygus spp. (Hemiptera: Miridae) or by the plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae).

Chinese TortrixCydia trasias(Lepidoptera: Olethreutidae): Suppression on Street-Planting Trees by Mass Trapping with Sex Pheromone Traps

Mass trapping to control the Chinese tortrix Cydia trasias (Meyrick) by removal of males using sex pheromone traps was evaluated in three plots of Chinese scholar-trees Sophora japonica L. in Beijing, China, in 2000. The traps, baited with 0.25 mg C. trasias synthetic sex pheromone (60% E8, E10-dodecadienyl acetate (E8, E10–12:Ac) and 40% E8, E10-dodecadien-1-ol (E8, E10–12:OH), were deployed in the trapping plots at a density of one trap per two trees. The trees in all plots were planted ≈4.5 m apart along pedestrian paths. In the trapping plot on Zhichun Road, the mating rates of caged virgin females were reduced by 70.65% and 66.48% when compared with the control plots during the overwintering- and second-generation moth flight-period, respectively. Population densities of hibernating larvae on tree trunks during the third generation were significantly lower than those of the overwintered generation (the third generation of the previous year). Tunneled petioles caused by first- and second-generation larvae were reduced by 47–79% and 62–81%, respectively. Bored seed pods caused by third-generation larvae were reduced by 87–96%. Higher initial populations in the trapping plot on North Shuangyushu Road may have led to the higher observed petiole and seed pod injuries than in the other two plots during the second and third generations. Thus, male removal using sex pheromone traps is a promising means of effectively controlling C. trasias on street-planted Chinese scholar-trees.

Integrated control of oriental fruit moth (Lepidoptera: Tortricidae) in peach orchards using insecticide and mating disruption.

The efficacy of an integrated and a conventional oriental fruit moth, Grapholita molesta (Busck), control program was compared using 4-ha blocks of peach at three Niagara Peninsula farms during 1997-1999. In the integrated program, chlorpyrifos was used to control first-generation larvae and mating disruption using Isomate M100 pheromone dispensers was used to control the second and third generations. In the conventional program, chlorpyrifos was used to control first-generation larvae and pyrethroids were used to control larvae of the later generations. The average release rate of pheromone was 23.7-26.4 mg/ha/h over a period of 86-91 d. The pheromone treatment reduced the capture of moths in pheromone-baited traps on average by 98%, suggesting a high level of disruption. The integrated program provided control of oriental fruit moth similar to the control provided by a conventional program. The mean percentage of peach shoots infested with first- and second-generation larvae, and fruit infested with third-generation larvae was not significantly greater in the integrated-program blocks during the 3-yr study. The elimination of insecticide sprays from the integrated-program blocks did not result in an increase in damage caused by plant bugs. The incidence of damage caused by other pests was negligible in both the integrated and conventional blocks.

A behavioral screen for isolating zebrafish mutants with visual system defects.

Optokinetic and phototactic behaviors of zebrafish larvae were examined for their usefulness in screening for recessive defects in the visual system. The optokinetic response can be reliably and rapidly detected in 5-day larvae, whereas the phototactic response of larvae is variable and not robust enough to be useful for screening. We therefore measured optokinetic responses of mutagenized larvae as a genetic screen for visual system defects. Third-generation larvae, representing 266 mutagenized genomes, were examined for abnormal optokinetic responses. Eighteen optokinetic-defective mutants were identified and two mutants that did not show obvious morphological defects, no optokinetic response a (noa) and partial optokinetic response a (poa), were studied further. We recorded the electroretinogram (ERG) to determine whether these two mutations affect the retina. The b-wave of noa larvae was grossly abnormal, being delayed in onset and significantly reduced in amplitude. In contrast, the ERG waveform of poa larvae was normal, although the b-wave was reduced in amplitude in bright light. Histologically, the retinas of noa and poa larvae appeared normal. We conclude that noa larvae have a functional defect in the outer retina, whereas the outer retina of poa larvae is likely to be normal.

Population regulation of a tropical damselfly in the larval stage by food limitation, cannibalism, intraguild predation and habitat drying.

The relative importance of intraspecific, interspecific, and seasonal causes of larval mortality were investigated for aquatic larvae of the giant damselfly Megaloprepus coerulatus in Panama. These larvae live in water-filled holes in fallen and living trees, where they and three other common odonate species are the top predators. By mid wet season, M. coerulatus larvae were found in nearly half of all tree holes that harbored odonates. Although M. coerulatus were typically, but not always, eliminated from holes inhabited by larger hetero-specifics, M. coerulatus were more likely to encounter conspecifics than other odonate species. Hole with less than 11 of water rarely contained more than a single larva. In large holes where M. coerulatus was the only odonate species present, multiple larvae coexisted at a density of one larva per 1-21 of water. There the absence of 2-4 of the 5 larval size classes, despite a continuous input of eggs, suggested that cannibalism was a common cause of mortality. The size of the final instar, which determined adult body size, was correlated positively with tree hole volume for male, but not female, larvae. Experiments showed that when two larvae were placed together in 0.4-1 holes with abundant tadpole prey, the larger larva killed the smaller one. Often the larva that was killed was not eaten. Small larvae were more tolerant of each other than were pairs of medium or large larvae. Before killing occurred, the presence of larger larvae reduced the growth of smaller individuals, relative to controls. 'Obligate' killing was density-dependent. In 3.0-1 holes with ad libitum prey, conspecific killing occurred until the larval density stabilized at one larva per 1-1.5 I, similar to the density found in large holes under field conditions, For M. coerulatus, cannibalism functions to reduce the number of potential competitors for food in addition to providing nutrition. When interactions between paired larvae in small holes were experimentally prevented, competition for food reduced the growth of one or both larvae relative to controls. Holes that were watered during the dry season supported larval densities similar to those in the wet season. Thus, dry season mortality could not be attributed to a decrease in available prey. Rather, M. coerulatus larvae could not survive more than 1 month of complete drying. Because the dry season typically lasts more than 6 weeks, habitat drying is a secondary source of mortality, affecting second- or third-generation larvae that fail to emerge before tree holes dry out completely.

Persistence and Biological Activity of Residues of Granular Insecticides in Organic Soil and Onions with Furrow Treatment for Control of the Onion Maggot (Diptera: Anthomyiidae)

studies with the granular insecticides chlorfenvinphos, chlorpyrifos, isofenphos, and terbufos showed that when these are applied properly as in-furrow treatments for the control of the onion maggot in organic soil, good control is obtained of the first generation maggot and that damage caused by infestation by second- and third-generation larvae is significantly reduced. Survival of onion maggots from eggs to larvae was independent of whether the eggs were placed beside the plant or in the leafaxils of the plant. Fonofos, chlorpyrifos, and isofenphos were more persistent than isofenphos in organic soil and, with the exception of chlorpyrifos, all had declined to less than half the original level by the beginning of September. Significant residues of each of the four insecticides were detected in immature bulbs (64-76 d after seeding) with the level of residue being much higher in the roots and outer skin. Ninety-six days after seeding (2 mo before harvest), insecticide residues in bulbs were below the level of detection.

Two Types of Overwintering Larvae in a Wild Multivoltine Bruchid, Kytorhinus sharpianus BRIDWELL(Coleoptera:Bruchidae)

We studied the seasonal prevalence and the overwintering stage(s) of a wild multivoltine bruchid, Kytorhinus sharpianus, on the host, Sophola flavescens, in Tokyo and Tsukuba. Adult K. sharpianus appeared first on S. flavescens in late April and oviposited on the fresh pods of S. flavescens in mid-June. First-generation adults emerged from early to late August and oviposited until late August. A few second-generation adults emerged form mid-September to mid-October, with most females laying eggs by late October without adult feeding. However, most second-generation larvae did not grow to adulthood in fall, remained at the late final instar during winter, pupated in early April and emerged in late April. The third-generation larvae which hatched in October remained at the first instar during winter and grew to the second instar in late March and to the third instar in early April. A laboratory experiment showed that the late final-instar larvae diapaused at 24°C and 12L-12D, although they grew to adults at 24°C and 16L-8D. These results suggested that K. sharpianus over-winters either at the late final instar in the second generation or at the young instar in the third generation. This species seems to be basically bivoltine in the Kanto district and a few individuals show a trivoltine cycle.

Natural Enemies of the Spotted Tentiform Leafminer, Phyllonorycter blancardella (Lepidoptera: Gracillariidae), in Sprayed and Unsprayed Apple Orchards in Wisconsin

Ten species of primary parasitoids but few predators were found to attack the spotted tentiform leafminer, Phyllonorycter blancardella (Fabricius), in Wisconsin. An ectoparasitoid, Sympiesis marylandensis Girault, and an endoparasitoid, Pholetesor ornigis (Weed) were the most frequently collected parasitoids of tissue-feeding larvae. Scambus decorus Walley, a new parasitoid record for P. blancardella , oviposited on third-generation larvae, producing mostly male offspring. S. decorus adults were also observed feeding on leafminer larvae. S. decorus, P. ornigis , and Pnigalio maculipes (Crawford) are new species records for Wisconsin. Mortality of tissue feeding leafminer larvae is caused primarily by ovipositing parasitoids. It is suggested that host feeding and stinging of hosts without oviposition account for much of the remaining tissue feeder mortality. Parasitism of tissue feeders was highest in unsprayed orchards, lower in sprayed orchards and very low in orchards sprayed specifically for P. blancardella . Mortality caused by P. ornigis was highest during the first and third host generations, whereas eulophid-induced mortality of tissue feeders was greatest during the second host generation. Lower apparent parasitism by P. ornigis in unsprayed orchards may be the result of multiparasitism.

Phenology and control of the onion maggot (Diptera: Anthomyiidae) in Michigan onion production

The phenology and control of the onion maggot, Delia antiqua (Meigen) (Diptera: Anthomyiidae), were investigated in commercial onion fields in Michigan from 1978 to 1980. First-generation emergence of adults occurred at 399 Dδ (degree-days) (4.4°C base). Second- and third-generation emergence occurred at 1142 and 1840 D°. Adult flight activity was correlated with time of damage to onion plants by 1st and 2nd generation larvae. Third-generation larvae were only observed on unharvested mature onions. Phenologies of the various life-stages are compared to development rates determined in the laboratory. Application of foliar insecticide sprays for adult control did not provide additional protection from root maggot damage where granular insecticides had been applied at planting. Recommendations for onion maggot control are discussed.

Effects of copper, nickel and zinc on the life cycle of the caddisfly Clistoronia magnifica (limnephilidae)

AbstractThe caddisfly Clistoronia magnifica (Banks) (Limnephilidae) was exposed to copper, nickel and zinc in life cycle tests. The copper test included continuous exposure of first‐generation aquatic larvae and pupae, second‐generation larvae and pupae and third‐generation larvae. The aerial adults and eggs were exposed only to body burdens obtained as larvae and pupae. Nickel and zinc tests included first and second‐generation exposure. Copper concentrations of ≥17 μg/L prevented completion of the life cycle, and significant reduction in adult emergence occurred at 13.0 μg/L. The no‐observed‐effect level for copper was 8.3 μg/L. Nickel concentrations of ≥250 μg/L prevented completion of the life cycle. The no‐observed‐effect level for nickel was 66 μg/L. At the highest zinc concentration (5,243 μg/L), no effects were observed on any of the life stages.

Differential responses of biotypes of the pea aphid, Acyrthosiphon pisum (Harris), to a chemically defined diet

Four clones of the pea aphid, Acyrthosiphon pisum (Harris), collected from different regions in North America (St-Jean and Ile-aux-Coudres, Quebec, in Canada, and New Mexico and Kansas in the United States) were reared on an aseptic chemically defined diet and characterized into biotypes. The clones from St-Jean and Kansas appeared similar and represent one biotype, whereas those from New Mexico and Ile-aux-Coudres were different from each other, as well as from St-Jean and Kansas. Third-generation larvae were produced only by biotypes St-Jean and New Mexico; however, none of them reached the adult stage.The amount of diet ingested and its utilization by different clones also varied. In 24 h, the total diet ingested by flrst-instar larvae from St-Jean, Kansas, New Mexico, and Ile-aux-Coudres was 164,140, 112, and 65 μg per aphid respectively. During the same period the larvae increased their weights by 28, 13, 10, and 10% respectively. Total, or percent increase in weight, was however not proportional to the amount of diet ingested, thus reflecting on the relative efficiency of diet utilization by different clones.

Studies of British Anthomyiid Flies. VI.—The annual Cycle of Generations in some Anthomyiid Root Flies

Field and laboratory studies have shown that the several root-infesting Anthomyiid flies differ greatly in the number of generations composing their annual cycle and in the minimum temperature conditions necessary for full activity.Onion flies (Delia antiqua (Mg.) ) were mainly univoltine in laboratory cultures. Of 369 first-generation pupae studied in 1953, only 141 (about 40 per cent.) gave rise to flies in July-August and 228 (about 60 per cent.) entered a diapause, in which 196 (about 85 per cent, of those entering diapause) remained until the following spring. In 1954, 99 per cent, of the first-generation pupae from univoltine flies and 97 per cent, of those from bivoltine flies entered the overwintering diapause in July. It then appeared that exposure to low temperatures during the development of the first-generation larvae had induced diapause in the pupae. This was confirmed by the unexpectedly high proportion (49 per cent.) of wild first-generation pupae which entered the overwintering diapause in July in the cool summer of 1954. It was also established that the spring oviposition period for D. antiqua began about the end of May, and it appeared that, in the field, air temperatures of approximately 70°F. were necessary to stimulate egg-laying. First-generation flies emerged in the second and third weeks of July, their numbers depending on the temperature in June. A few second-generation flies, together with late first-generation flies, may emerge in September, but the temperature is then too low for oviposition and there seem to be no third-generation larvae.