Host Plant Phenology Research Articles

Influence of corn, Zea mays, phenological stages in Diatraea saccharalis F. (Lep. Crambidae) oviposition

Abstract: Diatraea saccharalis F. is a major pest to maize, sorghum and sugarcane crops in Latin America and the most damaging insect pest of maize in Argentina. Female moths lay their eggs on lower and upper sides of leaves and sheaths of corn plants. Oviposition behaviour of different species of corn stem borers is influenced by host plant phenology in different ways. Host pubescence affects oviposition behaviour in different species of caterpillars. Oviposition preferences for phenological stages, leaf surface and vertical distribution in corn plants were investigated. Corn plots of 120 m2 were sown with a Pioneer pubescent cultivar in six planting dates, each one replicated three times according to a completely randomized design. Throughout the season 14 samplings were carried out, during which plants were randomly chosen within each of the six treatments and exhaustively examined in order to count the number of egg masses and their location in the leaf surface and in the vertical structure of the plant. Diatraea saccharalis preferred laying their eggs on the lower sides of leaves located in the middle stratum of corn plants whose phenological stages were older than V10. Our study suggests that attention should be paid to the influence of crop phenological stage in the location of egg masses in futures studies, as oviposition preference can change through plant maturation.

Larval Performance in Relation to Labile Oviposition Preference ofCrocidolomia pavonana[F.] (Lepidoptera: Pyralidae) Among Phenological Stages of Cabbage

Abstract Crocidolomia pavonana (=binotalis) [F.] demonstrates oviposition peaks in the field that we believe to be correlated with host plant phenology. In previous two-choice laboratory experiments, we found the highest relative proportion of oviposition on cabbage to correspond either to plant growth stages ≈7–8 wk or ≈9–11 wk old, depending on the alternate host plant with which it was presented. In cabbage-only trials, leaves from 7- to 8-wk-old plants were preferred. Inconsistency in preference led to the question of whether oviposition on either cabbage growth stage would confer adaptive advantages in offspring performance. We simulated oviposition on four phenological stages of cabbage in two ways. In a study of complete immature development, growth rate, pupal weight, and survivorship were measured. We also compared food utilization efficiency during the fourth larval instar by analyzing growth rate, efficiency of biomass accumulation, and frass production by analysis of covariance (ANCOVA). For b...

Effects of Host Plant Phenology on Oviposition Preference ofCrocidolomia pavonana(Lepidoptera: Pyralidae)

Field studies have demonstrated mixed success in trap cropping to manage Crocidolomia pavonana (=binotalis) [F.], a major pest of cruciferous crops in Asia. A possible explanation for this is an influence of host plant phenology on oviposition preference. We tested this in simultaneous two-choice oviposition bioassays under laboratory conditions. In cylindrical cardboard experimental arenas, with 5-cm2 leaf windows, individual C. pavonana females were offered eight sequential phenological stages of cabbage (Brassica oleracea L., Capitata group, cultivar Gloria) with a constant stage of preflowering Indian mustard (Brassica juncea, variety rugosa, cultivar Green Wave). Results showed a significant effect of cabbage developmental stage on oviposition preference. We continued with two-choice bioassays, using whole leaves, in screen cage experimental arenas. Females were offered the three most preferred phenological stages of cabbage and differing stages of four potential trap crop alternatives: preflowering Indian mustard; preflowering Chinese cabbage (B. rapa L., variety pekinensis [Lour.] Olsson); preflowering, flowering, and “with silique” sawi manis (B. rapa, variety parachinensis [Bailey] Tsen and Lee); and preflowering and flowering sayur pahit (B. rapa, variety parachinensis [Bailey] Tsen and Lee). Results indicated that the phenological stages of both plants had a significant effect on relative oviposition preference. However, patterns of preference changed in the context of the different plant species combinations. In addition, implicit hierarchical preference order was frequently contradicted. These results have implications for the improvement of trap cropping strategies to manage C. pavonana and for the potential success of biological control of Plutella xylostella [L.], where these pests occur in complex.

Predatory Role of <I>Neoseiulus fallacis</I> (Acari: Phytoseiidae): Spatial and Temporal Dynamics in Washington Red Raspberry Fields

The seasonal abundance of spider mites and their predator Neoseiulus fallacis (Garman) (Acari: Phytoseiidae) was determined during three consecutive years in Washington State red raspberry fields. Tetranychus urticae Koch (Acari: Tetranychidae), Eotetranychus carpini borealis (Ewing) (Acari: Tetranychidae), and N. fallacis were commonly found in Skagit and Whatcom Counties. E. carpini borealis colonized the fruiting canes earlier in the season than T. urticae. The two phytophages overlapped in midseason, but T. urticae entered diapause earlier than E. carpini borealis and N. fallacis. Densities of N. fallacis increased with increase in spider mite densities. However, the numerical response of the predator was more evident for T. urticae than for E. carpini borealis. Nevertheless, the predator was spatially associated with the two prey species. The spatial and seasonal distribution of N. fallacis in relationship to host plant phenology and prey distribution may influence the effectiveness of this predator as a biological control agent against spider mites in red raspberry. Densities of the predator increased too late to prevent spider mite damage. The predatory role of N. fallacis could be enhanced by introducing or conserving predators that are more tolerant to climatic factors that prevail in and around the cane canopy in the beginning of the season.

DESCRIPTION, BIOLOGY, AND MATERNAL CARE OF PACHYCORIS KLUGII (HETEROPTERA: SCUTELLERIDAE)

The life cycle of Pachycoris klugii on its native host, Cnidoscoulus multilobus (Euphorbiaceae), is reported in detail for the first time. Egg, nymphs, and adults are described and illustrated. Extensive variation was observed in the color pattern of adults. Maternal behavior was related to egg parasitism, habitat and host plant phenology. The tachinid fly Trichopoda pennipes was observed parasitizing adults and the scelionid wasp Telenomus pachycoris parasitized eggs of P. klugii.

Adaptation of a generalist moth, Operophtera brumata, to variable budburst phenology of host plants

AbstractThe adaptation of three allopatric populations of a generalist moth, Operophtera brumata (L.), on two tree species, Prunus padus (L.) and Quercus robur (L.) which represent the extremes of the timing of budburst in spring, was studied in Finland and Sweden. The synchrony of the hatching and budbursting was monitored, and its importance to dispersal and growth of larvae was assessed by rearing cohorts of larvae, whose hatching dates were manipulated, on both hosts. In addition, the realised heritability of the hatching time was estimated.Experimental populations hatched in approximate synchrony with the budburst of their original host species. As a result of the manipulation of the hatching dates of larvae, the growth rates of larvae decreased and the dispersal rates increased on both hosts in relation to the ageing of foliage. The realised heritability of hatching times was rather high (0.63). There were fewer differences in the host use efficiency and behaviour of the experimental populations than in the hatching phenology. The synchrony of hatching with the budburst of the local dominant host plant is probably a result of stabilising selection.

Will climate change have a different impact on different trophic levels? Phenological development of winter moth Operophtera brumata and its host plants

Will climate change have a different impact on different trophic levels? Phenological development of winter moth <i>Operophtera brumata</i> and its host plants

Molecular Phylogeny of the North American &lt;I&gt;Enchenopa binotata&lt;/I&gt; (Homoptera: Membracidae) Species Complex

The North American Enchenopa binotata (Say) species complex is a model of sympatric speciation in which phytophagous insects are hypothesized to diverge through host-plant specialization resulting from changes in host plant usage that alter life history timing. A robust phylogeny is needed to evaluate the historical relevance of the prediction that sister taxa differ in critical life-history traits. Phylogenetic analysis using parsimony and likelihood criteria of 2305 nucleotides in sequences from mitochondrial COI, COII, tRNA-Leucine, and 12S genes revealed two pairs of sister taxa. Both pairs of sister taxa differ from each other in the timing of egg hatch in the spring that is mediated by differences in host-plant phenology. Host plant mediated timing of egg hatch results in asynchronous life histories among sister taxa facilitating reproductive isolation. Sister taxa of Enchenopa from Celastrus and from Viburnum differ in their diurnal and temporal spans during which mating occurs. Mating of Enchenopa from Liriodendron takes place after that of its sister species on Cercis. These results support the hypothesis that speciation could have been initiated through a shift to a host plant that alters life-history timing.

The role of host plant phenology in the development of the oak leafroller moth, Tortrix viridana L. (Lepidoptera: Tortricidae)

Phenological coincidence between the insect and its host plant was studied in natural environment. Two phenological events were controlled: degree to which larval eclosion coincided with budburst in oaks, and synchrony between the duration of the insect development and growth of host plant leaves. Both factors varied from one season to another, and among the early, normal and late-flushing trees. These two phenological factors were compared in respect to their effect on the herbivore, using average pupal weights and densities as estimations of the insect success. Developmental synchrony to host plant appeared to be of a decisive importance for the successful development of the insect larvae. In contrast, the synchrony between eclosion and budburst did not influence strongly pupal weights and densities in given case, when variation in bud-flushing dates (about 10 days) did not exceed the T. viridana ability to resist starvation under the spring conditions. Two distinct peaks of larval eclosion from the eggs, collected in winter, were registrated under constant laboratory conditions. The larvae tended to hatch earlier on the trees with higher rates of average leaf growth (2-year data). Thus, two sympatric populations of the herbivore, differing in the dates of egg hatching, coexist in the same area.

Synchronization of Shoot Elongation in the BambooPhyllostachys heterocycla(Monocotyledoneae: Gramineae) and Emergence of the Gall MakerAiolomorphus rhopaloides(Hymenoptera: Eurytomidae) and its InquilineDiomorus aiolomorphi(Hymenoptera: Torymidae)

Adult emergence of the gall maker Aiolomorphus rhopaloides Walker and its inquiline, Diomorus aiolomorphi Kamijo, was examined in three stands of the bamboo, Phyllostachys heterocycla Matsumura. A. rhopaloides emerged from the galls from mid-April to early May, coinciding with the bamboo bud elongation period. This synchronization suggests that eggs laid in the new shoots have a nutritional advantage for resulting larvae, and that a slight advance or delay in emergence may reduce suitable oviposition sites, causing population fluctuations. D. aiolomorphi emerged from late April to early June during the bamboo shoot elongation period and females could lay eggs in elongated shoots providing relatively higher nutrition for larvae. The difference in the gall density on P. heterocycla and P. bambusoides Siebold and Zuccarini is explained on the basis of synchronization with host plant phenology.

Evidence for Reproductive Diapause in the Fritillary &lt;I&gt;Speyeria idalia&lt;/I&gt; (Lepidoptera: Nymphalidae)

Reproductive characteristics of a northeastern Kansas population of the fritillary Speyeria idalia (Drury) were studied. Hemolymph juvenile hormone (JH) titers, ovarian development, and fat body utilization were monitored weekly in adult females over their entire 1997 flight period, which extended from mid-June to early October. Dissections of female reproductive systems revealed that S. idalia females mate just once, soon after they emerge in mid- to late June. Gas chromatographic-mass spectrometric determinations of juvenile hormone suggested that they undergo a reproductive diapause through mid-August related to the absence of or very low titers of juvenile hormone. Oogenesis and fat body depletion do not commence until late August/early September, soon after which oviposition occurs. The onset of oogenesis coincides with a rapid rise in hemolymph titers of JH I, JH II, and JH III. The predominant juvenile hormone homolog was JH II, but both JH I and JH III exhibited smaller, concomitant peaks. Four fundamentally different lepidopteran reproductive strategies have been recognized based on various reproductive characteristics and the type of gonadotropic hormones used to stimulate oogenesis. Speyeria idalia exhibits a type of reproductive strategy that has not been documented in Lepidoptera, typified by protandry, female monandry, long-lived (>8 wk) females that feed throughout their adult lives, greatly delayed oogenesis that occurs late in adult life, and apparent juvenile hormone control of gonadotropic processes. This reproductive strategy appears to be an adaptation to the phenology of larval host plants, namely coordinating the life cycle with that of the seasonally restricted violets on which larval survival of this monophagous species depends.

Host-plant mediated effects of root herbivory on insect seed predators and their parasitoids

The effects of root herbivory on a tephritid seed predator (Terellia ruficauda) and its parasitoids were investigated. Soil fauna were manipulated by insecticide treatment; host plant (Cirsium palustre) phenology and the oviposition behaviour of both tephritid and parasitoids (Pteromalus elevatus and Torymus chloromerus) recorded. Although insecticide-treated (and hence reduced root herbivory) plants had larger flowerheads, population abundances of both tephritids and parasitoids were greater on thistle plants subjected to root herbivory. Percentage parasitism was similar in both treatments. Root herbivory is thought to enhance the nutrient quality of plants and this may have resulted in the tephritid preferentially feeding on thistles whose roots had been attacked. Parasitoids on these plants were probably affected by a combination of increased plant attractivity (as for the tephritids), smaller flowerheads aiding ovipositor entry and more tephritid hosts being present. This is the first study to show that root herbivores, through plant-mediated interactions, can affect seed herbivores and also, albeit indirectly through the host, natural enemy trophic levels.

Synchronization of gallers with host plant phenology

AbstractIn addition to various bottom‐up effects, the synchronization of herbivores with their host plant phenology determines quality and quantity of food resources and affects the preference–performance linkage and abundance of herbivores. The synchronization has a more critical meaning for such short‐lived galling insects as cecidomyiid adults and young aphid stem mothers than for other insects. This review, first, presents general information about gall midges and gall aphids, together with their life history patterns and some ecological attributes. Second, some important topics of galling insect–host plant relation are briefly reviewed. Then, synchronization patterns between gall midge emergence and host plant phenology are analyzed to discuss the adaptive strategies of gall midges and to show how the amount of available food resources is affected by the time lag in synchronization. The spatial distribution pattern and the preference–performance linkage of aphid stem mothers is also discussed in relation to synchronization.

Does the presence of ant nests matter for oviposition to a specialized myrmecophilous Maculinea butterfly?

More than 50% of the lycaenid butterflies have an ant-associated lifestyle (myrmecophily) which may vary from coexistence to specific mutualistic or even parasitic interactions. Ant-related host-plant selection and oviposition has been observed in some myrmecophilous lycaenids. Therefore, it is remarkable that there is no evidence for this behaviour in the highly specialized, obligate myrmecophilous butterflies of the genus Maculinea. In contrast with previous findings, our results provide evidence for ant-related oviposition patterns in Maculinea alcon in relation to the distribution of specific host-ant nests (i.e. Myrmica ruginodis) based on repeated egg counts during the flight period in two populations. We also show that ant-related oviposition can be counterbalanced by intraspecific competition and oviposition deterrency when host plants already carry several eggs. Therefore, the absence of a correlation between egg load and the presence of host-ant nests at the end of the flight period should be interpreted carefully Whether ovipositional cues are obtained either directly (from ants or their nests) or indirectly (from vegetation structure), and whether alternative explanations based on the phenology and growth form of host plants are possible, is discussed.

Geographical variation in insect developmental period: effect of host plant phenology on the life cycle of the bruchid seed feeder Kytorhinus sharpianus

AbstractThe voltinism of the bruchid Kytorhinus sharpianus Bridwell (Coleoptera: Bruchidae) and the phenology of its host plant Sophora flavescens Aiton (Leguminosae) were observed at four latitudes: Aomori (40°46′ N), Obanazawa (38°37′ N), Kujiranami (37°21′ N) and Mitsuma (36°05′ N) in northeastern Honshu (Japan). Kytorhinus sharpianus life cycle ranged from bivoltine and partially trivoltine in the south to univoltine and partially bivoltine in the north. Sophora flavescens started growing later in spring at higher latitudes. However, the relative growth rate was higher in the north (Aomori) than in the south (Mitsuma). In parallel with this, the first‐generation of adult K. sharpianus appeared later at higher latitudes. When the four local populations were reared at 24 °C, L16:D8 and 65% r.h., males developed faster than females. The mean developmental time showed a saw‐toothed latitudinal cline. The reversion in the latitudinal trend of variation corresponded to the change in the major type of life cycles from univoltine to bivoltine. Two heat units throughout the year and post‐fruiting period were calculated as the sums of degree‐days above the developmental threshold (12 °C) of K. sharpianus. Both heat units decreased in parallel with each other with increasing latitude. The greater growth rate of hosts in the northern population compensated for the smaller heat units. In addition, when the heat units were divided by the degree‐days needed to complete development, the numerical value was the approximate number of generations observed in each locality.

Control of summer and winter diapause in Pidorus euchromioides (Lepidoptera: Zygaenidae) on Chinese sweetleaf Symplocos chinensis

AbstractPidorus euchromioides Walker has two separate diapauses during its life cycle, a winter diapause as a fourth larval instar and a summer diapause as a prepupa in a cocoon. Winter diapause was induced by short photoperiods. The critical day length of 13 h 20 min to 13 h 40 min at 23.3°C under insectary conditions was very similar to the critical day length (13 h 32 min) observed in the field. Sensitivity to day length was restricted to the first 9 days, corresponding to the first and second instars. The duration of larval diapause was not only strongly correlated with the inducing photoperiod, but also dependent on the number of short days experienced during the larval growth period. The shortest diapause occurred at the critical day length, or when the larvae were exposed for 6 days (a critical number of short days) to a photoperiod of LD 12 h:12 h. The summer diapause appeared to be primarily determined by a genetic factor and only occurred in part of the overwintering generation and the first generation. The two different diapause mechanisms play important roles. Winter diapause ensures that P. euchromioides synchronizes its development and activity with the phenology of specific host plants, and summer diapause provides the species with a high degree of adaptation to an unpredictable environment.

THE EFFECTS OF WINTER LENGTH ON THE GENETICS OF APPLE AND HAWTHORN RACES OF RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE).

Host plant-associated fitness trade-offs are central to models of sympatric speciation proposed for certain phytophagous insects. But empirical evidence for such trade-offs is scant, which has called into question the likelihood of nonallopatric speciation. Here, we report on the second in a series of studies testing for host-related selection on pupal life-history characteristics of apple- (Malus pumila L.) and hawthorn- (Crataegus mollis L. spp.) infesting races of the Tephritid fruit fly, Rhagoletis pomonella (Walsh). In particular, we examine the effects of winter length on the genetics of these flies. We have previously found that the earlier fruiting phenology of apple trees exposes apple-fly pupae to longer periods of warm weather preceding winter than hawthorn-fly pupae. Because R. pomonella has a facultative diapause, we hypothesized that this selects for pupae with more recalcitrant pupal diapauses (or slower metabolic/development rates) in the apple-fly race. A study in which we experimentally manipulated the length of the prewintering period for hawthorn-origin pupae supported this prediction. If the period preceding winter is important for apple- and hawthorn-fly pupae, then so too should be the length (duration) of winter; the rationale for this prediction is that "fast developing" pupae that break diapause too early will deplete their energy reserves and disproportionately die during long winters. To test this possibility, we chilled apple- and hawthorn-origin pupae collected from a field site near Grant, Michigan, in a refrigerator at 4°C for time periods ranging from one week to two years. Our a priori expectation was that longer periods of cold storage would select against allozyme markers that were associated with faster rates of development in our earlier study. Since these electromorphs are typically found at higher frequencies in hawthorn flies, extending the overwintering period should favor "apple-fly alleles" in both races. The results from this "overwinter" experiment supported the diapause hypothesis. The anticipated genetic response was observed in both apple and hawthorn races, as allele frequencies became significantly more "apple-fly-like" in eclosing adults surviving longer chilling periods. This indicates that it is the combination of environmental conditions before and during winter that selects on the host races. Many tests for trade-offs fail to adequately consider the interplay between insect development, host plant phenology, and local climatic conditions. Our findings suggest that such oversight may help to explain the paucity of reported fitness trade-offs.

Phenology of Winter Moth Feeding on Common Heather: Effects of Source Population and Experimental Manipulation of Hatch Dates

1. Winter moth Operophtera brumata outbreaks on common heather Calluna vulgaris have recently caused extensive damage to moorlands in Scotland. 2. The importance of synchrony between O. brumata hatching and C. vulgaris bud-burst in determining subsequent larval survival and development was investigated. 3. Heather-feeding O. brumata populations hatched at least 15 days in advance of an oak-feeding population, and achieved close synchrony with the onset of C. vulgaris shoot growth. 4. Heather-feeding O. brumata biotypes showed significantly greater survival rates than oak-feeding biotypes on C. vulgaris. 5. Experimental delay of O. brumata hatching by 30 days resulted in no drop in larval survival or developmental performance on C. vulgaris, despite a decline in foliar nitrogen concentration over this time. 6. Nutritional compensation mechanisms may explain the apparent insensitivity of O. brumata development to host-plant phenology and nitrogen content.

Progressive restriction of host plant exploitation along a climatic gradient: the willow psyllid Cacopsylla groenlandica in Greenland

1. Host plant selection by the endemic willow psyllid Cacopsylla groenlandica was studied at eight sites in three locations along a N–S climatic gradient in west Greenland.2. C. groenlandica oviposited and developed on four willow species: Salix glauca, S. arctophila, S. uva‐ursi and S. herbacea. Development took place on female catkins of all species and on leaf shoots of S. glauca.3. At sites in southern Greenland, C. groenlandica fully utilized all four willow species. However, there was progressive reduction of host plant species and tissues exploited as latitude increased, such that towards the northern limit of its range the psyllid became highly specialized, feeding only on female catkins of S. glauca, despite the presence of alternative hosts. Where plant growth was tightly constrained within a restricted growing season, the demands of synchronizing with more than one species may have become too great, resulting in specialization on a single host.4. The probable mechanisms producing specialization were between‐species differences in host plant phenology, linked to variation in the growing season, set against the partially non‐overlapping geographical distribution patterns of the host willows.5. A small degree of phenological asynchrony between host plants can be advantageous for the insect. Under favourable conditions the reproductive season can be extended by using a series of host plants with staggered phenologies. Some ‘early’ hosts also create predator‐free space. However, as asynchrony increases, the advantages disappear as the insect becomes unable to exploit the full range of host options.6. The importance of host plant synchrony in the life histories of arctic insects is discussed.

Host-Plant Phenology and Colorado Potato Beetle (Coleoptera: Chrysomelidae) Population Trends in Eastern Washington

Developmental phenology of host plants and population trends for Colorado potato beetle, Leptinotarsa decemlineata (Say), were studied in eastern Washington in 1993 and 1994. Volunteer potato emerged earlier than cultivated potato and served as the earliest food source for the beetle. Hairy nightshade, Solanum sarrachoides Sendtner, first appeared in mid-June, and continued to germinate throughout the season. Overwintered adult beetles moved >300 m to colonize cultivated potato in early spring before germination of nightshade. The number of 1st-generation eggs were highly correlated with the number of adults colonizing potato, indicating that population size of the 1st generation was determined largely by the density of colonizing beetles. Many 1st-generation adults moved off of potato and onto nightshade. These adults hardly moved >100 m if nightshade plants were available on the perimeter of or in the potato fields. Population densities of 2nd-generation beetles were higher on nightshade than on potato. Our results indicate that management strategies should focus on controlling populations of the 1st generation by reducing densities of beetles colonizing potato.