Survival Of Instars Research Articles

EGG STORAGE OF Podisus nigrispinus (HEMIPTERA: PENTATOMIDAE) PREDATORS AT LOW TEMPERATURES

ABSTRACT Podisus nigrispinus are bedbug predators that are used as biological control agents of defoliating larvae in eucalypt plantations. The mass rearing of natural enemies produces large numbers of insects, but the number of predators produced may not coincide with the timing of the outbreaks of pest populations in the field. The aim of this study was to evaluate the effects of different storage periods on the eggs of P. nigrispinus at low temperatures of 5, 13 and 15ºC. The treatments consisted of periods of 5, 10, 15 and 20 days of storage of predator eggs at each temperature indicated. After the different periods of storage, the eggs were removed, and the egg viability, the survival and duration of nymphal instars and the sex ratio of emerged adults were evaluated. Egg storage at 5ºC reduced the percentage of hatched eggs, while viability values close to 50% were observed for storage periods of up to 10 days at 13ºC and up to 15 days at 15ºC. For these treatments, the survival rates of nymphs were similar to those of the control. The different storage periods had no effect on the duration of the nymphal stage or the sex ratio of P. nigrispinus at any of the temperatures. Therefore, the storage temperature of 5ºC caused the death of the majority of the embryos, while it is possible to store P. nigrispinus eggs up to 10 and 15 days at 13 and 15ºC, respectively.

Egg Hatch and Survival and Development of Beet Webworm (Lepidoptera: Crambidae) Larvae at Different Combinations of Temperature and Relative Humidity.

To understand the role that temperature and humidity play in the population dynamics of the beet webworm, Loxostege sticticalis L. (Lepidoptera: Crambidae), egg hatch, survival of first-fifth instars, survival of the full larval stage, survival curves, and larval development rates were investigated at combinations of four temperatures (18, 22, 26, and 30°C) and five relative humidities (RH; 20%, 40%, 60%, 80%, and 100%). We found that greatest egg hatch rate, survival rates of the first and second instars, and survival rate of the complete larval stage occurred at 22°C and 60-80% RH; the lowest values for these parameters were observed at 30°C and 20% RH. Survival of first instars was significantly affected by the interaction of temperature and relative humidity. However, survival of third and fourth instars was neither affected by temperature nor relative humidity, and that of fifth instars was significantly affected only by relative humidity level. The survival curve for larvae was well described by a type III Weibull distribution. Duration of larval stage decreased as temperature increased, but was not affected by relative humidity. We therefore conclude that eggs and early instars are the most critical stages for survival to the pupal stage, and 22-26°C and 60-80% RH are the optimum conditions for their survival and development. These findings confirm that temperature and relative humidity are the critical environmental factors affecting the population growth of L. sticticalis, with temperature being more important.

Comparison of Biology betweenHelicoverpa zeaandHelicoverpa armigera(Lepidoptera: Noctuidae) Reared on Artificial Diets

Abstract The objective of this study was to compare growth and development of Helicoverpa zea Boddie and Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) larvae that were feeding on an artificial diet. Neonate larvae of H. zea and H. armigera were collected in maize fields cultivated at the Brazilian Agricultural Research Corporation, Embrapa Maize & Sorghum, in Sete Lagoas (Minas Gerais) and in farmers' cotton fields in Luis Eduardo Magalhaes (Bahia), respectively. Bioassays were conducted in the laboratory using individual larvae in 50 mL plastic cups fed a white bean—based artificial diet and maintained at a temperature of 26 ± 2 °C and a relative humidity of 47 ± 10%. The following larval biological parameters were evaluated: number and duration of instars, survival of larval instars and pupae, larval biomass, larval head capsule size, and larval length. An adaptation index was computed for comparison of development of the 2 species. Significant differences were observed between the species for al...

Occurrence of first crab instars of the Atlantic ghost crabOcypode quadrata(Decapoda: Brachyura: Ocypodidae) along the coast of Maine, U.S.A.

Adult populations of Ocypode quadrata have not been reported north of Cape Cod, Massachusetts, but their megalopae, which invade sandy beach habitats, have been recovered recently from the coasts of Massachusetts and Maine. Two megalopa specimens were reported from Maine beaches at Kennebunkport and Kennebunk in 2012. More recently in September 2014, a specimen was collected from Pemaquid Beach, Bristol, Maine, ~ 96 km north of the Kennebunkport-Kennebunk region. Herein, we also report the occurrence of three specimens of first crab instars from Goose Rocks Beach, Kennebunkport, collected on October 2–3, 2014. These juvenile crabs were found slightly above the tide line of the previous high tide, where they were preserved and measured (mean carapace width x carapace length = 6.34 ± 0.38 mm x 5.64 ± 0.34 mm; mean carapace width/carapace length ratio = 1.13). This is the first evidence for megalopa to first crab metamorphosis of ghost crabs in the cold waters beyond Cape Cod. Conformation of survival of early crab instars of O. quadrata, a primarily southern latitude brachyuran, to adulthood in Gulf of Maine waters requires further collections and experimentation.

Do defensive chemicals facilitate intraguild predation and influence invasion success in ladybird beetles?

Egg predation and cannibalism are believed to be common phenomena among many species of aphidophagous predatory ladybird beetles despite the presence of alkaloid based defensive chemicals in all life stages. We identified defensive chemicals from eggs of three congeneric species, one introduced into North America (Coccinella septempunctata L.), and two native (C. transversoguttata richardsoni Brown, and C. novemnotata Herbst), and examined the effects of ingested defensive chemicals on first instars. Ingested congeneric alkaloids were not toxic to first instars, likely because the three congeners produce the same principal alkaloids, precoccinelline and coccinelline, in similar amounts. First instars of the three congeners accumulated alkaloids ingested through egg cannibalism and congeneric predation. Egg consumption doubled the amount of alkaloids in first instars when they fed on conspecific or congeneric eggs, in comparison to a pea aphid diet. No detrimental effects of ingested congeneric alkaloids on development or survival of first instars were observed among these congeners. Chemical defenses of eggs are therefore not likely to be important in favoring the invasive species, C. septempunctata, in interactions with these native congeneric species. Because the invasive species is the most aggressive predator, having the same types of alkaloids may facilitate disproportionate intraguild predation on native congeners by C. septempunctata thereby potentially enhancing the invasion success of this introduced species.

Susceptibility to Disease Across Developmental Stages: Examining the Effects of an Entomopathogen on a Grasshopper (Orthoptera: Acrididae) Pest

An important but under studied component of grasshopper ecology is how pathogens affect grasshopper population dynamics. However, insect population responses to disease may depend upon age demographics which vary temporally. In a field experiment, we varied grasshopper [Camnula pellucida (Scudder)] developmental stage (3rd instar, 4th instar, 5th instar, and adults) and fungal pathogen exposure (lab and field) and measured grasshopper mortality and survival. Lab exposed grasshoppers were directly inoculated with the pathogen, while field exposed grasshoppers were passively exposed to naturally occurring spores. Disease increased grasshopper mortality rates and decreased overall survival. However, this effect varied with grasshopper developmental stage and mode of pathogen exposure. Adults were far less susceptible to fungal infection than nymphs. Disease mortality was 52% higher in lab exposed grasshoppers compared to individuals exposed to a natural fungal epizootic in the field. Lab exposure decreased 3rd instar survival rates more than exposure to the pathogen in the field. In contrast, grasshopper survival was invariant with disease exposure for 4th and 5th instars due to peak levels of naturally occurring fungal spores. By August 2010, the field epizootic was declining and food availability became the most important determinant of adult grasshopper survival. Therefore, age demographics may need to be considered when predicting how grasshopper populations will respond to disease.

Cold Storage Enhances the Efficacy and Margin of Security in Postharvest Irradiation Treatments Against Fruit Flies (Diptera: Tephritidae)

Cold storage is used to preserve fruit quality after harvest during transportation in marketing channels. Low temperature can be a stressor for insects that reduces survivorship, and cold storage may contribute to the efficacy of postharvest quarantine treatments such as irradiation against quarantine insect pests. The combined effect of irradiation and cold storage was examined in a radiation-tolerant fruit fly, Bactrocera cucurbitae Coquillet (melon fly), and a radiation-intolerant fruit fly, Ceratitis capitata (Wiedemann) (Mediterranean fruit fly) (Diptera: Tephritidae). Third instars on diet or in papaya were treated with a sublethal radiation dose of 30 Gy and stored at 4 or 11 degrees C for 3-13 d and held for adult emergence. For both fruit fly species, survival of third instars to the adult stage generally decreased with increasing cold storage duration at 4 or 11 degrees C in diet or papaya. Survivorship differences were highly significant for the effects of substrate (diet > papaya), temperature (11 > 4 degrees C),and irradiation (0 > 30 Gy). Few Mediterranean fruit flies survived in any cold storage treatment after receiving a radiation dose of 30 Gy. No melon fly larvae survived to the adult stage after irradiation and 11 d cold storage at 4 or 11 degrees C in papayas. Cold storage enhances the efficacy and widens the margin of security in postharvest irradiation treatments. Potentially irradiation and cold storage can be used in combination to reduce the irradiation exposure requirements of quarantine treatments.

Interaction effects of Bacillus thuringiensis subsp. kurstaki and single nuclear polyhedrosis virus on Plutella xylostella

The interaction effects of Bacillus thuringiensis subsp. Kurstaki and HaSNPV on the survival of second instars of Plutella xylostella were evaluated under laboratory conditions. The exposure of second instars to the combination of HaSNPV (2.3×103, 3.8×104, 6.6×105 occlusion bodies (OB) ml−1) and B. thuringiensis subsp. kurstaki (2.4×101, 3.4×103, 4.7×105 spores ml−1), indicated an additive effect in the toxicity of most combinations. Synergism occurred when the lowest concentration of the combination of B. thuringiensis (2.4×10−1 spores ml−1) and HaSNPV (2.3×103 OB ml−1) was applied. When the larvae were fed on leaf discs contaminated with both B. thuringiensis and HaSNPV, their growth and developmental rates were decreased and a reduction in their pupation rate, pupal weight as well as the emergence rate of adults was observed. The LT50 values correlated negatively with B. thuringiensis and HaSNPV concentrations.

Implications of saline concentrations for the performance and competitive interactions of the mosquitoesAedes aegypti(Stegomyia aegypti) andAedes albopictus(Stegomyia albopictus)

Aedes albopictus (Stegomyia albopictus) (Diptera: Culicidae) has probably supplanted Aedes aegypti (Stegomyia aegypti) throughout most of its historical range in the U.S.A., although Ae. aegypti still exists in large coastal cities in southern Florida. We measured salt concentrations in field containers along an axis perpendicular to the coast and examined intraspecific outcomes in these species under different salt concentrations in a factorial study using varying intra- and interspecific densities in different conditions of salinity to order to determine if salt could mitigate the documented competitive superiority of Ae. albopictus. Salt in field containers declined away from the coast, with maximal values similar to our lower salt concentrations. Egg hatching and short-term survival of pupae and late instars were not affected by salt concentrations; survival of early instars of both species decreased at higher concentrations. In high salt conditions, Ae. aegypti achieved higher survival. In the longterm experiment, both species displayed longer development times. Salt did not affect interactions for either species; Ae. aegypti survived in the highest salt conditions, regardless of density. The tolerance of Ae. aegypti to high salt concentrations may allow it to use coastal containers, although because salt did not mediate interspecific interactions between Ae. aegypti and Ae. albopictus, the ultimate effects of salt on the coexistence of these species or exclusion of either species remain unknown.

Effects of Chlorantraniliprole and Thiamethoxam Rice Seed Treatments on Egg Numbers and First Instar Survival of <I>Lissorhoptrus oryzophilus</I> (Coleoptera: Curculionidae)

Effects of treatment of rice seeds with an anthranilic diamide, chlorantraniliprole, and a neonicotinoid, thiamethoxam, on egg laying and first instar survival in rice water weevil, Lissorhoptrus oryzophilus Kuschel, were examined under greenhouse conditions. Exposure of adult weevils to rice (6-7 leaf stage) grown from seeds treated with chlorantraniliprole and thiamethoxam resulted in reduction in numbers of eggs and first instars. The low egg numbers by adults exposed to chlorantraniliprole-treated plants was confirmed as a sublethal effect on adults: adult survival was not impacted after 4 d of feeding on foliage from chlorantraniliprole-treated plants but the number of eggs laid by these weevils was reduced when released on untreated plants. Furthermore, a comparison of first instar emergence from chlorantraniliprole-treated plants and from untreated plants infested with weevils previously exposed to this chemical suggested that chlorantraniliprole was also reducing egg or first instar survival. In contrast, adults that fed on foliage from thiamethoxam-treated plants showed increased mortality. Possible sublethal effects of thiamethoxam on the number of eggs laid by adults were investigated by infesting untreated plants with weevils that survived exposure to thiamethoxam via foliar feeding (7 microg active ingredient/seed). Prior exposure to thiamethoxam through adult feeding reduced egg numbers. However, potential larvicidal or ovicidal effects of thiamethoxam seed treatments could not be detected in this study because of low first instar emergence from both thiamethoxam-treated plants and from untreated plants infested with weevils previously exposed to this chemical. These experiments revealed that the two seed treatments accomplish weevil control in different ways.

Mapping asynchrony between gypsy moth egg-hatch and forest leaf-out: Putting the phenological window hypothesis in a spatial context

Spring phenology in temperate forest ecosystems is responding in diverse ways to global climate change, with unknown consequences for insect disturbances that affect forest productivity. Adaptive forest management that anticipates changes in insect disturbance regimes requires an understanding of the mechanistic links between climate and disturbance behavior. Phenological mismatches between insects and their hosts have the potential to modify patterns of defoliation that are a significant disturbance in temperate forests. Yet the frequency and extent of phenological mismatches have not been quantified over forest landscapes. Forest dwelling, spring-feeding defoliators must synchronize larval emergence annually with leaf-out phenology of host trees. Lack of synchrony can limit population expansion, unless dispersing larvae successfully locate phenologically compatible hosts. We quantified the potential for successful dispersal of an introduced defoliator in a forest landscape by mapping phenological asynchrony from 2000 to 2010. Maps compared MODIS derived leaf-out with gypsy moth egg-hatch from the BioSIM insect phenology model. Mean temporal differences between gypsy moth egg-hatch and leaf-out were sufficient (<−5 or >+10days) to severely limit 1st instar survival in 5 of 11years. Biologically meaningful phenological asynchrony extended over distances of 3.1–4.9km, well beyond typical gypsy moth dispersal thresholds (<1km), meaning that larvae in some parts of the landscape were unable to escape unfavorable phenology by dispersing. Significant spatial heterogeneity in phenological asynchrony clarifies its potential to affect gypsy moth population dynamics and patterns of defoliation disturbance, in contrast with previous field-based research conducted at smaller spatial scales. Our results suggest that delay of leaf-out in this ecosystem due to inadequate winter chilling may disrupt gypsy moth disturbances, as years where host forest phenology is significantly asynchronous over a majority of the landscape become more common. Our modeling approach is relevant and applicable to a wide range of ecological phenomena that require synchrony of phenological interactions across trophic levels. The results inform forest management by illustrating areas in host dominated landscapes that are most susceptible to defoliation in a given year, allowing for improved planning of insect suppression activities.

Influence of crowding and diet on the development and survival of the ladybird Brumoides suturalis (Coleoptera: Coccinellidae) reared on two aphid species

The influence of solitary versus group rearing on the development and survival of the three-striped ladybird beetle Brumoides suturalis (Fabricius) was studied using two aphid species, Acyrthosiphon pisum (Harris) and Aphis gossypii Glover, as diet. Rearing pattern (solitary or group) had no significant influence on the success of rearing, but prey species did. While immature stages developed faster on A. pisum, the survival of early instars was higher on A. gossypii. Diet had no effect on pupal survival.

Effects of the Heavy Metal Cu&lt;SUP&gt;2+&lt;/SUP&gt; on Growth, Development, and Population Dynamics of Spodoptera litura (Lepidoptera: Noctuidae)

Spodoptera litura (F.) larvae were fed with artificial food containing four different concentrations of copper (25, 50, 100, and 200 mg/kg). Copper affected growth, development, and population dynamics of late instar larvae. Our results indicate that the fourth and fifth instar survival rates were significantly reduced at 50-200 mg/kg copper (Cu2+). Moreover, all the Cu2+ treatments significantly reduced pupation and moth emergence rates in a dose-dependent manner. Larvae fed 25 or 50 mg/kg Cu2+ showed significant reductions in development period compared with non-Cu controls, and the pupation duration of animals fed 200 mg/kg was significantly longer than in non-Cu controls. All Cu2+ concentrations significantly reduced individual pupal weights compared with controls. In addition, Cu2+ at some concentrations significantly affected fertility parameters, such as doubling population time (DT), the net reproduction rate (R(o)), the mean generation time (T), the intrinsic rate of increase (r(m)), and the finite increase rate (A). Our study demonstrates that low concentrations of Cu2+ in the diet (25 and 50 mg/kg) shorten the generation time by 4-5 d, whereas higher Cu2+ concentrations (100 and 200 mg/kg) increase DT for 1-2 d.

Towards an improved understanding of the dynamics of vineyard‐infesting Scaphoideus titanus leafhopper populations for better timing of management activities

This paper deals with supervised management of Scaphoideus titanus (Homoptera Cicadellidae) and describes a phenology model designed for improving the understanding of the within-vineyard dynamics and the timing of insect growth regulator (IGR) applications. The model consists of five components dealing with (a) the beginning of the post-dormancy development of overwintering eggs, (b) the egg hatching patterns, (c) the duration of first-instar nymphs, (d) the development and survival of subsequent instars and (e) the stochastic development of cohorts and their passage into the adult stage. Laboratory data permitted the parameterisation of temperature-dependent development and survival functions. Field data consisting mainly of beating tray catches allowed model parameterisation and validation. The model satisfactorily predicts the dynamics of age structures, the beginning as well as the pattern of egg hatching, the occurrence of the third instar and the emergence of adults. The phenology model is useful for timing IGR applications and for setting up monitoring activities in supervised S. titanus control. The model is an entry point into an adaptive management system, in that real-time weather and monitoring data are continuously integrated into the model for improving its explanatory and predictive capabilities.

Oviposition Preference for Water-Stressed Plants in Orius insidiosus (Hemiptera: Anthocoridae)

Plant species affect the oviposition behavior of the zoophytophagous predator Orius insidiosus. This study was conducted to determine whether manipulating plant quality, via stress, within a single plant species (Phaseolus vulgaris L.) would affect the oviposition behavior of O. insidiosus and the subsequent performance of its offspring. Plants that had water withheld (water-stressed treatment) had about 20% less total dry weight than plants that were watered to alleviate the drought stress (unstressed treatment). In comparison to unstressed plants, unifoliolate leaves and petioles of water-stressed plants had about 20 and 12% less relative water content, 54 and 29% greater sap osmotic potential, and 19 and 70% greater concentrations of amino-nitrogen, respectively. Reproductive O. insidiosus were then presented stressed and unstressed plants in a two choice test to determine oviposition preference. First instar survival on the two treatments was evaluated in no-choice tests. Orius insidiosus laid 70% more eggs per cm2 on the stressed plants. The lifespan of newly-hatched nymphs was the same in both treatments. Eggs were more frequently laid on the leaf vein than the petiole of unstressed plants, whereas in stressed plants oviposition on these parts occurred at equal frequency. These findings suggest that physiological changes in water-stressed bean plants created conditions more favorable for O. insidiosus oviposition. As there was no increase in offspring performance, it is hypothesized that females chose oviposition sites near preferred feeding sites or plant tissues that were less prone to desiccation.

Oviposition and Development of the Tarnished Plant Bug (Heteroptera: Miridae) on Field Maize

Reduced insecticide use in cotton, Gossypium hirsutum L., as a consequence of the Boll Weevil Eradication Program and the broad adoption of Bt cotton, have helped make the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), a consistent pest of cotton each year in the mid-south. Maize, Zea mays L., has been implicated as having a role in the season-long dynamics of tarnished plant bug infestations in cotton. To date, no published information exists describing the quality of maize as a host for tarnished plant bug. No-choice field studies indicated that adult tarnished plant bug females oviposited into maize leaves, tassels, and ears. Laboratory studies showed that first-instar tarnished plant bugs could successfully develop to the adult stage when fed maize silks at the R1 growth stage, tassels before (VT) and during (R1) pollen shed, and milk stage (R3) kernels from the tip and base of the ear. The proportion of nymphs surviving to the adult stage on these tissues was often similar to that of broccoli, Brassica oleracea L. Nymphs did not develop to adults when fed V5 or R1 maize leaves. However, survival of first instars to the adult stage was improved when nymphs fed on tassels with pollen for 6 d and then moved to silks or leaves. Another field study showed that tarnished plant bugs reproduced in maize mainly during the tassel (VE and VT) and the R1-R3 ear growth stages, and a single new generation was produced in maize during these stages. The highest population recorded during the study (24 June 2005) consisted mostly of nymphs and was estimated to be 29,600/ha (12,000/acre). These studies showed that maize is a suitable host for tarnished plant bug reproduction and development, and its production plays a significant role in the population dynamics of the tarnished plant bug in the mid-south.

The Impact of Temperature on Biological Aspects and Life Table ofRhopalosiphum padi(Hemiptera: Aphididae) Fed with Signal Grass

ABSTRACT The impact of temperature was evaluated on Rhopalosiphum padi (L.) (Hemiptera: Aphididae). Nymphs, 12-h-old, were placed individually in cylindrical plastic dishes (2.5 × 2.5 cm), with a layer of 1% agar in which leaf disks of signal grass had been placed. The nymphs were reared at 12, 16, 20, 24, 28, and 32°C ± 1°C, RH of 70 ± 10% and 12-h photophase. We evaluated number of instars, duration of each instar and the nymphal period, survival of instars, duration of the reproductive period, daily and total production of nymphs, and longevity of the nymphal and adult phases. To construct the life expectancy table and fecundity, daily observations were made of 70 nymphs at each temperature, from birth to death. Development of R. padi was faster with increased temperature, but they did not complete the last nymphal instar at 32°C. The same pattern occurred for the pre-reproductive, reproductive, and post-reproductive periods. The highest fecundity rates were between 16°C and 24°C. The highest fertility...

Evaluation of Bifenthrin Applications in Tires to Prevent Aedes Mosquito Breeding

The efficacy of maximum label rates of bifenthrin applications to dry tires to prevent Aedes mosquito breeding was investigated by field colonization and bioassay trials in shaded and unshaded locations. Aedes notoscriptus and Culex quinquefasciatus larvae were the most abundant species present in the field colonization trial. Colonization and survival of Ae. notoscriptus larvae to the late instar occurred significantly earlier in treated tires in shaded compared with unshaded locations (P = 0.002). Bifenthrin applications in shaded tires only prevented early instar survival for approximately 2.6 wk. Aedes notoscriptus late instars did not appear in the treated unshaded tires. Culex quinquefasciatus colonized treated tires from the 2nd wk in both shaded and unshaded treatments. In the bioassay, water from bifenthrin-treated tires, through extrapolation, was found to kill approximately 100% of late instar Ae. notoscriptus for only approximately 2.0-2.2 wk in shaded and unshaded tires. Under conditions optimal for Aedes breeding, such as shaded locations, high ambient temperatures, high relative humidity, and high amounts of leaf/organic matter accumulations, bifenthrin may not be effective as a larval control measure in tires for greater than 2.0-2.6 wk.

The fine‐scale population dynamics of spruce budworm: survival of early instars related to forest condition

Abstract 1. A lagged, density‐dependent relationship between survival of early instars and host‐tree condition is revealed during outbreaks of spruce budworm, Choristoneura fumiferana Clem. Persistent damage to hosts leads to deterioration of the stand.2. Resource limitation affects survival during early‐instar dispersal of spruce budworm. Impediments to distinguishing these events with estimates of survival were overcome with a simple model that describes the dispersal and survival processes. The model was used to analyse a recent 15‐year population series from Black Sturgeon Lake and two historical datasets from Green River, in Canada.3. Defoliation‐induced damage to the trees resulted in increased losses of spring‐emerging larvae that are dispersing in search of feeding sites. Losses were further exacerbated by biotic factors such as maternal fecundity, rates of infection by the pathogen, Nosema fumiferanae, and by weather‐related effects on the foraging period.4. Survival of early‐stage budworm larvae in persistent outbreaks declined and the likelihood of other density‐related factors such as rate of mortality from natural enemies increased. These results may reconcile outstanding differences in interpretation of the role of the forest resource in spruce budworm population dynamics and point to a common process linking the dynamics of other well‐known budworm species.

Ecological mechanisms of population change during outbreaks of the spruce budworm

Abstract 1. Stage‐specific survival and recruitment of spruce budworm were measured by frequent sampling of foliage in four outbreak populations over a 15‐year period in Ontario and Quebec, Canada.2. Patterns of change in population density during the outbreak collapse phase were closely linked to changes in survival of the late immature stages, and were determined largely by the impact of natural enemies.3. Host‐plant feedback also contributed significantly to survival patterns throughout the outbreak: annual defoliation influenced survival of fourth and fifth instars and fecundity while cumulative defoliation influenced survival of the very early larval stages (first and second) via impacts on stand condition.4. Inclusion of this host‐plant feedback reveals spruce budworm population dynamics as a function of density‐related trophic interactions that vary in their order and strength of influence over time. This view re‐introduces the importance of forest interactions as a component of dynamics of the spruce budworm.