Showing papers in "Environmental Entomology in 1999"
TL;DR: Two novel and simple mathematical models of arthropod temperature-dependent development are proposed and gave upper T L and lower T temperature threshold estimations, and the estimations obtained were better by using equation 1 rather equation 2.
Abstract: Two novel and simple mathematical models of arthropod temperature-dependent development are proposed. These models are easy to use and have 3 (equation 1) and 4 (equation 2) ecologically meaningful parameters, respectively. Each parameter can be estimated using nonlinear regression. These models were used to compare developmental rates at constant temperatures for our own experiments on Lobesia botrana (Dennis & Schiffermuller) and for data from 6 insect species described (a total of 13 stages). In all cases, we obtained an accurate nonlinear description of the rate of development against temperature given by the adjusted R 2 ([Kvalseth, 1985][1]). The adjusted R 2 calculated extended from 0.86 to 0.99 and were identical for our equations 1 and 2. In all cases, equation 2 provided the lowest residual sums of squares. The models gave upper T L and lower T temperature threshold estimations, and the estimations obtained were better by using equation 1 rather equation 2. Confidence intervals for each parameter were given and a comparison between estimated and observed temperature thresholds were presented.
[1]: #ref-11
632 citations
TL;DR: The results indicate that an adaptive seasonality is a natural consequence of the interaction between developmental parameters and seasonal temperatures, and although this adaptive phenology appears to be resilient to temperature fluctuations, changes in climate within the magnitude of predicted climate change under a CO2 doubling scenario are capable of shifting a thermologically hostile environment to a thermally benign environment.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a natural disturbance agent of considerable consequence in western pine forests. This economically and ecologically important insect has a strong requisite for maintaining a strict seasonality. Given this ecological requirement, it is somewhat surprising that no evidence for diapause or other physiological timing mechanism has been found. Seasonality and phenological timing for this species are apparently under direct temperature control. We investigate the consequences of direct temperature control by first constructing a computationally efficient phenology model based on previously published temperature dependent developmental data. We explored the dynamic properties of this model when subjected to observed microhabitat temperatures representing a range of thermal habitats from one region of the mountain pine beetle distribution. We also investigated the consequences of global climate change on phenology and seasonality. Our results indicate that an adaptive seasonality is a natural consequence of the interaction between developmental parameters and seasonal temperatures. Although this adaptive phenology appears to be resilient to temperature fluctuations, changes in climate within the magnitude of predicted climate change under a CO2 doubling scenario are capable of shifting a thermally hostile environment to a thermally benign environment. Similarly, increasing temperature by the same amount resulted in phenological disruption of a previously favorable thermal habitat. We discuss the implications of these results for restricting the current distribution of mountain pine beetle, and the potential for shifting distribution caused by global climate change.
203 citations
TL;DR: It appears that jasmonic acid induces resistance to insect herbivores in tomato plants and that this resistance produces no measurable costs to tomato plants.
Abstract: Plants can be treated with natural plant elicitors to induce resistance to herbivores. To use elicitors in agriculture we must know the net effects of induction on plant yield. For 4 yr, I induced plant resistance to insect herbivores in tomato plants using the natural plant hormone jasmonic acid. Foliar jasmonic acid application increased levels of polyphenol oxidase, an oxidative enzyme implicated in resistance against several insect herbivores. Induced plants received 60% less leaf damage than did control plants. I then looked at the effects of this induction on seedling survivorship, phenology, fruit production, and plant biomass in the presence and absence of herbivores. Induced plants produced fewer flowers than control plants, but this did not translate into differences in yield between treatments. In addition, there was no difference in yield between induced and control plants under natural and experimentally reduced herbivore levels. This lack of effect on yield may have been caused by low levels of herbivory in the unmanipulated controls. Thus, it appears that jasmonic acid induces resistance in tomato plants and that this resistance produces no measurable costs to tomato plants. Elicitors such as jasmonic acid may be valuable pest management tools, especially when there are high densities of herbivores that can reduce yield.
166 citations
TL;DR: The effect of refuge strips and cover crops on enhancing the seasonal activity-density of carabid beetles was greater in refuge strips than in control areas without refuge strips; however, the presence of a refuge strip did not alter carabids populations in the surrounding subplots in either year.
Abstract: Carabid beetles are important predators of arthropods and weed seeds in annual crops but may be limited in impact by the frequent and intense disturbances imposed on these systems. Pitfall trap sampling conducted in 1996 and 1997 examined the effect of refuge strips and cover crops on enhancing the seasonal activity-density of carabid beetles. The study site followed a soybean, Glycine max L. Merr, oats, Avena sativa L., and corn, Zea mays L., rotation. Refuges consisted of a central strip of 3 perennial flowering plants, Agastache foeniculun (Pursh) O. Kuntze, Origanum vulgare L., and Scropularia nodosa L, with orchard grass, Dactylis glomerata L., white clover, Trifolium repens L., and sweet clover, Melilotus officinalis L., seeded on each side. A cover crop was present only in 1996 and consisted of frost seeded red clover, Trifolium pratense L. A total of 5,117 and 2,316 carabid beetles was captured in pitfall traps comprising 14 species in 1996 and 20 species in 1997. Carabid beetle seasonal activity-density was greater (1996) or equal (1997) in refuge strips than in control areas without refuge strips; however, the presence of a refuge strip did not alter carabid populations in the surrounding subplots in either year. In 1996, subplots containing a cover crop had significantly higher carabid beetle activity-density than subplots without a cover crop. There was no carryover effect of cover crop on beetle activity-density in 1997. Among the most abundant species, a greater proportion of captures of the fall breeding species Pterostichus melanarius (Illiger), Pterostichus permundus (Say), and the spring breeding species Poecilus lucublandus (Say) occurred in the refuge strips. The spring breeders Poecilus chalcites (Say), Harpalus herbivagus Say, and Agonum cupripenne (Say), and the phytophagous fall breeder Harpalus pensylvanicus (De Geer) occurred in greater proportions in the crop areas. The potential use of these strategies for conserving carabid beetles in agricultural systems is discussed.
140 citations
TL;DR: Seasonal patterns of cold-hardiness, as measured by supercooling points in the laboratory, were compared with seasonal patterns of host tree phloem temperatures at several geographic sites for 2 beetle generations to better understand cold tolerance capabilities.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins, spends the majority of its life cycle within the phloem of pine trees, experiencing exposure to temperatures below −30°C in many parts of their expansive range. To better understand cold tolerance capabilities of this insect, seasonal patterns of cold-hardiness, as measured by supercooling points in the laboratory, were compared with seasonal patterns of host tree phloem temperatures at several geographic sites for 2 beetle generations. Larvae were found to be intolerant of tissue freezing, and supercooling points measured appear to be a reasonable estimate of the lower limit for survival. Of the compounds analyzed, glycerol was found to be the major cryoprotectant. No differences in supercooling points were found among instars or between larvae collected from the north and south aspect of tree boles. Both phloem temperatures and supercooling points of larvae collected from within the phloem were found to be different among the geographic sites sampled. Mountain pine beetle larvae appear to respond to seasonal and yearly fluctuations in microhabitat temperatures by adjusting levels of cold hardening.
125 citations
TL;DR: Host aphids of the parasitoid Diaeretiella rapae (M’Intosh,) are defined for Washington State, together with a listing of world findings, and D. rapae was shown to switch or alternate successfully between hosts, which suggests that certain host habitats might be used in conjunction with farmlands to enhance host opportunities for the Parasitoid and improve its population stability.
Abstract: Host aphids of the parasitoid Diaeretiella rapae (M’Intosh,) are defined for Washington State, together with a listing of world findings. Specifics are given on host habitats frequented by the parasitoid, comparative population abundance, associated parasitoid species, and host switching. D. rapae is a common parasitoid of Brachycorynella asparagi (Mordvilko), Hayhurstia atriplicis (L.), Brevicoryne brassicae (L.), Diuraphis noxia (Kurdjumov), and sometimes Myzus persicae (Sulzer). In total, 19 species of aphids were positively linked with D. rapae and 6 are reported as hosts for the first time— Acyrthosiphon lactucae (Passerini), Phorodon humuli (Schrank), Dysaphis plantaginea (Passerini), Brachycaudus tragopogonis (Kaltenbach), Uroleucon ivae Robinson, and Braggia sp. D. rapae was shown to switch or alternate successfully between hosts, which suggests that certain host habitats might be used in conjunction with farmlands to enhance host opportunities for the parasitoid and improve its population stability. Two of its primary aphid hosts, B. asparagi and D. noxia, reached pest status shortly after their arrival in Washington but are less problematic today, in part at least because of host switching and acceptance by D. rapae.
107 citations
TL;DR: These materials, or their active ingredients, may be useful in protecting fruit from attack by codling moth larvae by preventing larvae from orienting to and arriving at fruit.
Abstract: Nonhost chemicals may be useful for controlling insect pests of crop plants by interfering with orientation to, and selection of, host plants. Essential oils of 27 plant species were tested in 2 different laboratory assays for evidence of arrest and repellency of neonate larvae of the codling moth, Cydia pomonella L. In an olfactometer in which larval upwind movement toward apples was assessed, greatest arrest was achieved with oils of lavender, Lavandula officinalis L.; pennyroyal, Mentha pulegium L.; and cypress, Cupressus sempervirens L. . Oil of lavender was most effective in preventing larvae from moving upwind in the olfactometer. In a barrier assay, essential plant oils were applied to the distal ends of a glass rod (15 cm long) on which larvae were placed. Larvae crossed the barrier to reach apples impaled on each end of the glass rod. The most effective repellents in this barrier assay were rue, Ruta graveolens L.; garlic, Allium sativum L.; patchouly, Pogostemom cablin (Blanco); and tansy, Tanacetum vulgare L., oils. These 4 plant essential oils were most effective in causing larvae to turn away at the oil barrier. These materials, or their active ingredients, may be useful in protecting fruit from attack by codling moth larvae by preventing larvae from orienting to and arriving at fruit.
106 citations
TL;DR: The results reported here indicate that the use of imidacloprid may not be compatible with the coccinellid predator C. maculata.
Abstract: The coccinellid predator Coleomegilla maculata (DeGeer) is found throughout the central and eastern United States and is a potential biological control agent for interiorscapes. Currently, the systemic insecticide imidacloprid is widely used in interiorscape and landscape integrated pest management. Effects of imidacloprid on the fitness and behavior of C. maculata were examined by confining groups of adults with inflorescences of treated sunflower, Helianthus annus L. 'Big Smile'; chrysanthemum, Chrysanthemum morifolium Ramat. 'Pelee'; and dandelion, Tarax- acum officinale Wiggers. Confinement with inflorescences from imidacloprid-treated plants signif- icantly decreased the general mobility of C. maculata in each plant system. The magnitude of the reduction in mobility varied with plant species. In the sunflower bioassay, survivorship was lower for beetles exposed to imidacloprid at the label rate and twice the label rate (38.3 6 6.60 and 20.0 6 6.71% survival, respectively) than for beetles confined to untreated controls (97.5 6 2.50% survival). Also, in the sunflower bioassay, beetles exposed to the label rate and twice the label rate of imidacloprid took longer to produce their 1st eggs (9.78 6 2.01 and 14.00 6 2.10 d after bioassay respectively) than beetles from untreated controls (2.56 6 0.50 d after bioassay). The results reported here indicate that the use of imidacloprid may not be compatible with the coccinellid predator C. maculata.
104 citations
TL;DR: Differences in fitness and behavior must exist between nematodes reared under standard laboratory procedures and those in nature, as demonstrated by infectivity in 2 species of entomopathogenic nematode.
Abstract: Infectivity is an important measure of virulence in insect pathogens. The proportion of entomopathogenic nematodes that invaded a host, Galleria mellonella (L.), was used as a measure of infectivity in 2 species of entomopathogenic nematodes: S teinernema carpocapsae (Weiser) and Heterorhabditis bacteriophora Poinar. We compared infectivity between nematodes emerging directly from cadavers into sand with nematodes that were applied to sand in aqueous suspensions after collection in a White trap. Assay arenas consisted of 10 G. mellonella larvae in petri dishes filled with moist sand. After 20 or 44 h the larvae were removed and the number of nematodes that had invaded was counted after dissection. Infectivity of H. bacteriophora was significantly greater when nematodes emerged directly into sand compared with the aqueous application. After 24 h, a11% of H. bacteriophora from cadaver treatments had penetrated into a host, whereas infectivity of aqueous treatments was 4–10 times lower. A similar trend was observed after 48 h. The infectivity of S. carpocapsae from cadaver treatments was a24% in both treatments. An additional experiment was conducted for H. bacteriophora, which consisted of 3 treatments: nematodes directly from cadavers, nematodes applied in aqueous suspension, and nematodes in aqueous suspension that were exposed to an extract from macerated host cadavers. Higher infectivity was observed in the amended aqueous suspension compared with aqueous nematodes without the extract. This study emphasizes that differences in fitness and behavior must exist between nematodes reared under standard laboratory procedures and those in nature.
102 citations
TL;DR: It is demonstrated that photosynthetic adjustments can significantly contribute to plant tolerance resulting from arthropod injury, and evidence here indicates that an active plant defense through antibiosis comes at the cost of reduced capacity for physiological tolerance and compensation.
Abstract: Plant tolerance to injury from insect herbivores has several advantages as a pest management approach. However, its use is limited because mechanisms conferring plant tolerance are not well understood. We hypothesize that plant physiological responses, specifically photosynthesis, substantially contribute to plant tolerance to arthropod injury. This hypothesis was tested on 3 wheat ( Triticum eastivum L.) lines that differed in their mode of resistance to the Russian wheat aphid, Diuraphis noxia (Mordvilko). The lines were ‘Arapahoe’ (a susceptible line), PI 137739 (an antibiotic line), and PI 262660 (a tolerant line). These lines were grown in a greenhouse, aphids were maintained on plants for 1 wk, and physiological responses of these lines were determined. Light curve and fluorescence data indicated that the primary mechanism for photosynthetic rate reduction in aphid-injured leaves is via interference of the photochemical efficiency at the initial stage of photosynthesis. Aphid-injured seedlings had lower light-saturation points, which suggested less efficient use of light energy compared with control seedlings. Immediately after aphid removal, aphid injury reduced chlorophyll fluorescence and photosynthetic rates in all lines, but PI 137739 (with antibiosis) had significantly greater photosynthetic rate reduction. Photosynthetic rates of the tolerant line, PI 262660, began recovering 3 d after aphid removal with complete photosynthetic recovery 7 d after aphid removal. This gradual photosynthetic compensation did not occur in the other 2 lines. PI 262660 also had greater leaf area and more dry matter when compared with the other cultivars. This study demonstrates that photosynthetic adjustments can significantly contribute to plant tolerance resulting from arthropod injury. Moreover, evidence here indicates that an active plant defense through antibiosis comes at the cost of reduced capacity for physiological tolerance and compensation.
94 citations
TL;DR: A simple meteorological and behavioral model is created that can be used to predict the spread of the beetle infesting soybean, Glycine max (L), throughout the Midwest and results support the hypothesis that the origin of the population of western corn rootworm infested soybean is Ford County, IL.
Abstract: A behavioral change in some western corn rootworm, Diabrotica virgifera virgifera LeConte, populations is threatening the effectiveness of crop rotation, a successful management strategy for controlling this pest. We created a simple meteorological and behavioral model that can be used to predict the spread of the beetle infesting soybean, Glycine max (L.), throughout the Midwest. We used data collected in Illinois, Indiana, Michigan, and Ohio to create maps of observations to evaluate the model. We displayed data on the maps using thresholds of 10, 20, and 40 western corn rootworm beetles per 100 sweeps. Counts above a threshold represent populations searching for plants other than corn, Zea mays L., and adapted to the soybean–corn rotation. According to our model, the population adapted to soybean spreads 10–30 km per year depending on the directions of the prevailing storms and winds. The model underestimates the observed spread to the south. The model fits the Illinois data best when a threshold of 10 adults per 100 sweeps is used to visualize data and test the model. The model fits the Michigan data better with a threshold of 20 beetles, but is insensitive to the visualization and evaluation threshold for other areas. Model results support the hypothesis that the origin of the population of western corn rootworm infesting soybean is Ford County, IL. We predict that populations of western corn rootworm will be infesting soybean in much of Ohio, lower Michigan, and southern Wisconsin during the next 5 yr and eastern Iowa within the next 10 yr.
TL;DR: It is indicated that volatile chemicals produced by the plant in response to stimuli from feeding larvae enhance the attractiveness of the plant to female Colorado potato beetles.
Abstract: Unmated adult female Colorado potato beetles, Leptinotarsa decemlineata (Say), were attracted to damaged and chemically treated potato plants in an olfactometer. Significantly more beetles moved upwind to potato plants with damage from larval Colorado potato beetle compared with undamaged plants. More beetles moved upwind toward potato plants treated with regurgitant from Colorado potato beetle larvae or cabbage looper larvae, Trichoplusia ni (Hubner), compared with undamaged plants. Greater numbers of beetles moved upwind toward potato plants treated with N -(17-hydroxylinolenoyl)-L-glutamine (volicitin) or to plants treated with the plant hormone methyl jasmonate, compared with untreated plants. Mechanical injury to potato foliage did not increase beetle attraction when plants were tested 1 or 24 h after injury. These results indicate that volatile chemicals produced by the plant in response to stimuli from feeding larvae enhance the attractiveness of the plant to female Colorado potato beetles.
TL;DR: The selection of pubescent leaves infested with aphids by ovipositing females reflects both the food dependence and predation risk constraints of immature midges.
Abstract: Eggs and neonate larvae of the aphidophagous midge Aphidoletes aphidimyza Rondani are vulnerable to intraguild predation and starvation. The role of A. aphidimyza females in selecting suitable oviposition sites for offspring survival and development was investigated in the laboratory on potato. Oviposition preference, measured as the number of eggs laid in different microhabitats, increased with density of the potato aphid, Macrosiphum euphorbiae (Thomas), and plant pubescence. However, midge females do not discriminate between plants colonized by the coccinellid predator Coleomegilla maculata lengi Timberlake and those that are not. A. aphidimyza egg survival in the presence of C. macula larvae and adults was higher in sites characterized by a high density of trichomes than in other microhabitats. The selection of pubescent leaves infested with aphids by ovipositing females reflects both the food dependence and predation risk constraints of immature midges.
TL;DR: The northerly spread and establishment of A. tsugae may be impeded or perhaps prevented by the cold climate of northern New England, however, these studies are laboratory based and may not completely reflect what occurs in nature and adelgids along the leading edge of the infestation may develop an ability to tolerate colder temperatures in the future.
Abstract: The hemlock woolly adelgid, Adelges tsugae Annand, is not currently found in the U.S. Department of Agriculture plant coldhardiness zones colder than 5a in New England. Cold winter temperatures may be a factor limiting the northern expansion of this pest. Laboratory studies were conducted to determine the low lethal temperature of A. tsugae collected in January, February, and March 1997 from Holyoke, MA, located in plant coldhardiness zone 5a. Adelgids were exposed to temperatures of −20, −25, −30, −35, and −40°C for 2, 4, and 8 h. To correct for experimental mortality, comparisons in survival were made with untreated controls held at 0°C. For samples collected in January and February, a gradual decline in survival occurred as temperatures decreased. In March, differences in adelgid survival were not significant below −20°C. In this month, the percentage of live adelgids after cold treatment was ≤11% for −20°C and <2% for −25 and −30°C. In all months, no adelgids survived after exposure to −35 or −40°C. The minimum low temperature range for plant coldhardiness zone 4b, the next coldest zone north of the Mt. Tom infestation, is −28.9 to −31.6°C and further north in zone 4a it is −31.7 to −34.4°C. Therefore, the northerly spread and establishment of A. tsugae may be impeded or perhaps prevented by the cold climate of northern New England. However, our studies are laboratory based and may not completely reflect what occurs in nature and adelgids along the leading edge of the infestation may develop an ability to tolerate colder temperatures in the future.
TL;DR: The results show that larval and pupal cannibalism and interspecific predation occur more frequently when aphid populations crash, but there is no evidence of coccinellid density-dependent mortality or density- dependent larval dispersal among species.
Abstract: Coccinellid larvae are known to prey upon conspecific and heterospecific eggs, larvae, prepupae, and pupae. This behavior may depend on both the aggregation and intensive search of potential cannibals and predators near aphid colonies and the disappearance of aphids before coccinellid larvae have completed their development. We examined how coccinellid density and prey availability influence cannibalism and interspecific predation of larvae and pupae of 4 species of coccinellids. We determined whether coccinellid mortality and dispersal were density-dependent when prey become scarce, and estimated the leaving rates of Coleomegilla maculata (DeGeer), Adalia bipunctata (L.), and Hippodamia convergens (Guerin) larvae from plants with aphids and plants without aphids. Our results show that larval and pupal cannibalism and interspecific predation occur more frequently when aphid populations crash, but we found no evidence of coccinellid density-dependent mortality or density-dependent larval dispersal among species. However, A. bipunctata and H. convergens were significantly more aggressive and more likely to leave a plant without aphids than was C. maculata. These results suggest that the decision to stay on a plant is not strongly aphid- or pollen-mediated for C. maculata, but the decision to stay or leave does appear to be aphid-mediated for H. convergens and to some extent A. bipunctata. Whether a coccinellid larva stays or leaves and its tendency to cannibalize can affect larval and pupal survival and the population dynamics of each species.
TL;DR: Feeding, development, activity, and other behaviors were assessed among larvae of 13 representative specialist and generalist phytoseiid mite species and factors leading to specific larval life histories and taxonomic associations of larval feeding types are discussed.
Abstract: Feeding, development, activity, and other behaviors were assessed among larvae of 13 representative specialist and generalist phytoseiid mite species. Larval feeding types were not associated with degree of specialization. Obligatory-, facultative-, and nonfeeding larvae occurred in highly selective predators as well as in polyphages. Larvae of Phytoseiulus persimilis Athias-Henriot, P. macropilis (Banks), Kampimodromus aberrans Oudemans, Neoseiulus longispinosus (Evans), N. cucumeris (Oudemans), N. barkeri Hughes, and Typhlodromus pyri Scheuten are nonfeeders; larvae of N. fallacis (Garman), N. californicus (McGregor), and Amblyseius andersoni Chant are facultative feeders; and larvae of Galendromus occidentalis (Nesbitt), Euseius finlandicus (Oudemans), and E. hibisci (Chant) are obligatory feeders. Nonfeeding P. persimilis, P. macropilis, and K. aberrans larvae developed fastest. Obligatory-feeding E. finlandicus and E. hibisci larvae developed slowest. With food, larvae of most species rested after some initial activity, whereas obligatory-feeding larvae of both Euseius species frequently moved throughout the stage. Without food, obligatory-feeding larvae and facultative-feeding N. fallacis larvae were most active. Regardless of larval feeding type, larvae without food walked more and developed slower than those with food. Jerking was defined as an avoidance response and was most frequent in N. fallacis larvae but absent in larvae of K. aberrans and N. barkeri and obligatory-feeding larvae. Profiles of larval traits are provided for each species. Factors leading to specific larval life histories and taxonomic associations of larval feeding types are discussed.
TL;DR: The survival of Heterorhabditis bacteriophora, Steinernema carpocapsae, and S. glaseri varied in relation to the bulk density of a sandy loam soil, and rates of movement and infection by the nematodes were strongly correlated with the amount of soil pore space having dimensions similar to or greater than the diameters of the nemate.
Abstract: The survival of Heterorhabditis bacteriophora Oswego Poinar, Steinernema carpocapsae NY001 Weiser, and S. glaseri NC1 Steiner varied in relation to the bulk density of a sandy loam soil. Survival of H. bacteriophora decreased linearly with time (4–70 d) and quadratically with increasing bulk density, whereas S. glaseri survival decreased linearly with time, but increased quadratically with increasing bulk density. Survival of S. carpocapsae decreased quadratically with time, but was unaffected by bulk density. H. bacteriophora and S. glaseri infected larvae of the greater wax moth, Galleria mellonella (L.) for up to 10 wk after soil inoculation, and the incidence of infection showed no significant variation in relation to bulk density or time. In contrast, infection rate by S. carpocapsae increased with bulk density and decreased with time. The combined effects of soil texture and bulk density on movement these of nematode species generally decreased as the bulk density of 3 soil textures increased. However, the degree to which soils of high bulk density reduced movement differed among species and soil textures: H. bacteriophora was the least restricted; whereas, S. carpocapsae was the most restricted. All 3 species moved significantly more in sandy loam, than in loam or silty clay loam. Although movement was reduced at relatively high bulk densities, survival of the 3 nematode species was high. Rates of movement and infection by the nematodes were strongly correlated with the amount of soil pore space having dimensions similar to or greater than the diameters of the nematodes. In a sandy loam soil, H. bacteriophora moved at least 18 cm within 4 d of soil inoculation across all bulk densities tested, whereas S. carpocapsae moved only 9 cm at the 3 lower densities and <9 cm at the highest soil density. S. glaseri showed intermediate levels of movement.
TL;DR: Some species in undisturbed forests are lost after disturbance, even though actual diversity appears to increase, and Braconid wasps show promise as sensitive indicators of faunal changes during disturbance.
Abstract: Braconid wasps were used as an indicator group to test the hypothesis that the degree of disturbance in silvicultural treatments will change the total abundance and composition of species. Wasps were collected with Malaise traps on undisturbed (control), moderately disturbed (pine single-tree selection) and highly disturbed (pine-hardwood seed-tree) research plots of the USDA Forest Service in the Ouachita National Forest of Western Arkansas. We used 3 measures of wasp diversity: (1) numbers of individuals and numbers of species, (2) estimated total species richness and abundance, and (3) observed and estimated complementarity (proportions of species shared or not shared) among treatment types. In all, 1,300 wasps were collected, representing 23 subfamilies, 84 genera, and 251 morphospecies. Raw numbers of individuals and species suggested little difference among treatments. Total species richness estimates projected that the disturbed treatments have twice the number of species as the undisturbed. However, measures of complementarity revealed strongly different species complexes between treatments: undisturbed and highly disturbed treatments had just 24% of their species in common, whereas moderately and highly disturbed treatments shared 42%. Thus, some species in undisturbed forests are lost after disturbance, even though actual diversity appears to increase. Braconid wasps show promise as sensitive indicators of faunal changes during disturbance. These changes are best perceived through species comparisons between treatments when patterns of relative abundance and faunal complementarity are incorporated.
TL;DR: Field efficacy of 2 strains of entomopathogenic nematode, Heterorhabditis bacteriophora Poinar and Oswego, were examined against alfalfa snout beetle larvae, and data suggests that the NC strain will be more appropriate in situations where a biopesticide is desired, and theOswego strain is more appropriate where long-tern insect suppression is desired within more stable ecosystems.
Abstract: Field efficacy of 2 strains of entomopathogenic nematode, Heterorhabditis bacteriophora Poinar, were examined against alfalfa snout beetle larvae, Otiorhynchus ligustici (L.), in an established alfalfa field. Both strains were applied at 2.5 and 15 billion IJs per hectare using 2 different spray nozzle configurations. H. bacteriophora 'NC' reduced the insect larval population to 0.33-2.3 larvae per 54,900 cm 3 , significantly below the levels in the untreated controls, and reduced the incidence of snout beetle larval feeding and alfalfa stand death. NC occurred in 23-70% of the soil cores during the 1st growing season, but did not persist beyond the I st growing season. The high rate of H bcateriophora 'Oswego' reduced the insect larval population to 1.3 larvae per 54,900 cm 3 , significantly below the levels of the untreated controls but not as low as NC. Oswego also reduced the incidence of snout beetle larval feeding and alfalfa stand death. Oswego could be found in 73-99% of the soil cores during the 1st growing season and persisted for the entire 700 d of the trial. After 700 d, Oswego could be found in 24-44% of the soil cores taken within the treated plots. Evidence of nematode recycli ng was observed in both nematode strains. Data suggests that the NC strai n wou d be more appropriate in situations where a biopesticide is desired, and the Oswego strain is more appropriate where long-tern insect suppression is desired within more stable ecosystems.
TL;DR: The results of substratum-choice experiments indicate that the greater vegetative debris on the soil surface in the conservation tillage fields may explain the greater densities of both species in these fields.
Abstract: We studied the distribution of 2 wolf spider species in 2 soybean, Glycine max (L.), agroecosystems in southwestern Ohio, USA. We used replicated 0.42-ha soybean fields maintained under 2 different tillage regimes (conservation tillage and conventional tillage) and 2 wolf spider species [ Hogna helluo (Walckenaer) and Pardosa milvina Hentz]. We censused the spiders over 4 field seasons (1994–1997) and found a tendency for there to be more of both species in the conservation tillage plots, although this difference was not statistically significant in most years. There were also more P. milvina than H. helluo on most census dates. P. milvina had 2 population peaks in the years we censused for the whole season (1995–1997), which may be explained by a bivoltine life cycle in the fields. We also found that the conservation-tilled fields had more vegetative debris on the soil surface and more standing weeds than the conventionally tilled fields. The conservation-tilled fields also had a greater prey biomass than the tilled fields overall. These differences in habitat structure and prey availability were positively correlated with differences in the abundances of the 2 wolf spider species. The results of substratum-choice experiments conducted in the field and laboratory indicate that the greater vegetative debris on the soil surface in the conservation tillage fields may explain the greater densities of both species in these fields.
TL;DR: Studying predation on and discrimination between con- and heterospecific eggs among adult females and immatures of 13 phytoseiid mite species of different feeding types found generalists showed higher predation rates on heterosPEcific eggs than did specialists; on conspecific Eggs, the results were reversed.
Abstract: We studied predation on and discrimination between con- and heterospecific eggs among adult females and immatures of 13 phytoseiid mite species of different feeding types. Species ranged from specialized predators that feed on densely webbing spider mites (specialists) to polyphagous predators that feed on various kinds of animal and nonanimal food (generalists). Four of 9 generalists, including Neoseiulus californicus (McGregor), Amblyseius andersoni Chant, Neoseiulus fallacis (Garman), and Neoseiulus cucumeris (Oudemans), fed on phytoseiid eggs and preferred heterospecifics versus conspecifics. Their immatures completed development and adult females sustained oviposition by feeding exclusively on phytoseiid eggs, mainly heterospecifics. Also, 2 of 4 specialists, including Galendromus occidentalis (Nesbitt) and Phytoseiulus persimilis Athias-Henriot, accepted phytoseiid eggs as prey but did not discriminate eggs of their own from those of other species. P. persimilis and G. occidentalis suffered high juvenile mortality, and oviposition was negligible when they fed on phytoseiid eggs. Among species that fed on greater than or equal to 1 egg per female per day, generalists showed higher predation rates on heterospecific eggs than did specialists; on conspecific eggs, the results were reversed. Euseius finlandicus (Oudemans), Neoseiulus longispinosus (Evans), Phytoseiulus macropilis (Banks), Neoseiulus barkeri (Hughes), Euseius hibisci (Chant), Typhlodromus pyri Scheuten, and Kampimodromus aberrans (Oudemans) were less attracted to phytoseiid eggs as food.
TL;DR: In mating table experiments, successful matings decreased as the dose of radiation increased, and Untreated males were the most competitive among released codling moths.
Abstract: Environ. Entomol. 28(4): 669-674 (1999) In release-recapture tests conducted in apple orchards in Oroville, WA, a significant relationship was found between the dose of gamma radiation used to treat adult male codling moths, Cydia pomonella (L.), and the number of males recaptured in virgin female-baited sticky traps. Males treated with 100 Gy responded to calling virgin females in larger percentages than those treated with 200 and 250 Gy. However, the percentage of untreated (released) males captured was lower than the percentage of 100 Gy-treated males captured; a possible explanation for this is that untreated males were moving farther away and were less likely to be near the female-baited traps for recapture. Recapture was highest at days 4 and 5 after release, and significantly more males of all treatments were recaptured when dusk temperatures were at or above 16°C. Radiation also had a negative impact on codling moth mating competitiveness in the field. In mating table experiments, successful matings decreased as the dose of radiation increased. Untreated males were the most competitive among released codling moths.
TL;DR: Abundance of macrolepidopterans sampled by both methods was highest in 1991 (a warm, dry year) and lowest in 1992 (a cool, wet year).
Abstract: In a 3-yr study (1991–1993), we compared blacklight and Townes-style Malaise traps for assessing richness and abundance of forest macrolepidoptera in 4 small watersheds in the Fernow Experimental Forest in West Virginia. From early May through mid-August each year, sampling was conducted by one 8-W blacklight trap and 5 Townes-type Malaise traps in each watershed. Light traps were operated 1 night each week; Malaise traps operated continuously with the samples collected every 10 d. Over all years, macrolepidopteran species richness and abundance were 343 and 36,160 and 273 and 28,246 for light trap and Malaise trap samples, respectively. Percentage of total macrolepidopteran species per family was similar in both collecting methods although both diurnal and nocturnal lepidopterans were represented in Malaise samples. Differences were noted in percentage of total abundance by family. For example, geometrid abundance was similar in both sample types and represented the highest overall abundance, whereas the proportion of arctiids and notodontids was higher in light trap samples, and proportional abundance of noctuids was higher in Malaise trap samples. There were 135 and 65 species unique to light trap and Malaise trap samples, respectively. Abundance of macrolepidopterans sampled by both methods was highest in 1991 (a warm, dry year) and lowest in 1992 (a cool, wet year). Minimum ambient temperature and rainfall significantly affected the sizes of samples from blacklight traps, based on multiple-regression analysis. Moonlight in the absence of cloud cover reduced moth catch in blacklight traps. Mean ambient temperature, but not total rainfall, during trapping periods significantly affected the sizes of Malaise-trap samples based on a multiple autoregression analysis.
TL;DR: Enhancing gene flow between beetles surviving on transgenic plants and susceptible beetles in refugia should be advantageous in managing beetle resistance to transgenic Plants.
Abstract: Colorado potato beetle dispersal and reproduction was investigated under field and laboratory conditions. Movement and mating of newly emerged summer-generation Colorado potato beetle adults was monitored in the field using a mark-recapture technique, and beetle mating within experimental plots was recorded. The number of degree-days (DD) required for the beetles to become reproductive was tested in an environmental chamber using 10°C as a developmental threshold. A computer-linked flight mill system was used to quantify the influence of mating on the flight behavior of male and female beetles. Adult dispersal started within the first 24 h after eclosion from the pupae, but a significant proportion of newly emerged beetles stayed close to the place of their larval development until reaching reproductive maturity. The beetles required at least 34 DD before mating produced viable offspring, and females did not start laying eggs until a minimum of 51 DD after eclosion. Mating had a pronounced effect on beetle flight, decreasing flight activity of the females and increasing flight activity of the males. Enhancing gene flow between beetles surviving on transgenic plants and susceptible beetles in refugia should be advantageous in managing beetle resistance to transgenic plants.
TL;DR: Mycotrol ES could be an important component of integrated brown citrus aphid management in the future because of its relatively rapid kill at the application rates.
Abstract: Single- and multiple-dose bioassays and field trials were conducted to evaluate the efficacy of various isolates of entomopathogenic fungi against the brown citrus aphid, Toxoptera citricida (Kirkaldy). Single-dose bioassays demonstrated that brown citrus aphid is susceptible to several isolates of Beauveria bassiana (Balsamo) Vuillemin, Paecilomyces fumosoroseus (Wize) Brown & Smith, and Metarhizium anisopliae (Metschnikoff) Sorokin. Overt mycosis ranged from 23.1% ( M. anisopliae ARSEF 759) to 78.0% ( B. bassiana SARC 6000). In multiple-dose bioassays, good dose–-response was obtained with 3 B. bassiana isolates. The 6-d LD50 values for these isolates ranged from 119 to 995 conidia per square millimeter. There was a strong correlation (slopes >1.30) between rapid rise in mortality and dosage increase for all 3 isolates. Replicated field trials of the B. bassiana (strain GHA)-based mycoinsecticide Mycotrol ES provided relatively rapid kill at the application rates. The 5-d Abbott percentage efficacies of Mycotrol ES were, respectively, 79.8 and 94.4% at the half and full rates (2.5 × 1013 and 5 × 1013 conidia per hectare). Proportions of overt mycosis ranged from 0.67 at the half rate to 0.80 at the full rate. Mycotrol ES could be an important component of integrated brown citrus aphid management in the future.
TL;DR: Colony population size of Coptotermes acinaciformis (Froggatt), a species of mound- building, wood-eating, subterranean termite from tropical Australia, was estimated using a mark— recapture protocol and by direct counts of individuals collected from mounds, suggesting that the difficulties with mark-recapture protocols are not limited to 1 habitat type or species, and that mark—recaptur protocols do not estimate population size accurately.
Abstract: Colony population size of Coptotermes acinaciformis (Froggatt), a species of mound- building, wood-eating, subterranean termite from tropical Australia, was estimated using a mark— recapture protocol and by direct counts of individuals collected from mounds. The mark—recapture estimates varied widely within and between colonies (0.4—19.1 million), depending on definitions of recaptures (intensity of color), and could be 10 times larger than the direct counts (1.2—1.6 million). Assumptions of the mark—recapture protocol were shown to be violated in field and laboratory tests. Nile blue A, a fat-stain marker, did not persist and was transferred by cannibalism. Marked individuals did not mix uniformly with unmarked individuals; instead, foragers displayed feeding-site fidelity. The likelihood of recapture differed between castes and instars, there was a higher recapture rate of large workers and soldiers relative to small workers. These violations would increase population estimates from mark—recapture protocols. These results agree with those found for temperate species, suggesting that the difficulties with mark—recapture protocols are not limited to 1 habitat type or species, and that mark—recapture protocols do not estimate population size accurately.
TL;DR: The data suggest that early-instar cabbage looper larvae are negatively affected by whitefly infestations, but older instars become omnivores, consuming plant material as well as immature whiteflies, and emphasize the importance of the looper’s larval stage in interspecific interaction.
Abstract: The wide distribution, polyphagy, and the often severe effects of whiteflies, Bemisia spp., on their host plants cause a great potential for interspecific interactions between whiteflies and other insect herbivores. Feeding of the silverleaf whitefly, B. argentifolii Bellows & Perring, on collards, Brassica sp., induced high levels of pathogenesis-related proteins (e.g., chitinase, b-1,3-glucanase, peroxidase, and lysozyme) that are considered to play defensive roles against phytopathogens and insect pests. Total protein contents, however, were comparable with those of control plants. Development of cabbage looper larvae, Trichoplusia ni (Hubner), was 20.8% slower on whitefly-infested leaves than on control leaves; relative growth rate was reduced by 18% ( P ≪ 0.01). Final larval weight and survival were not affected by whiteflies. When feeding on whitefly-infested leaves, larvae were found more frequently on the adaxial side of the leaf, which is whitefly-free. The data suggest that early-instar cabbage looper larvae are negatively affected by whitefly infestations, but older instars become omnivores, consuming plant material as well as immature whiteflies. In the field, only 4% of the loopers survived to pupation on whitefly-infested plants, but 18% survived on the whitefly-free plants. The data emphasized the importance of the looper’s larval stage in interspecific interaction and stressed the potentially significant effect of whiteflies on other herbivores in agroecosystems.
TL;DR: Serological data are discussed as supporting the hypothesis of beetle aggregation behavior as an important component of bacterial wilt epidemiology and suggest the proportion of A. vittata that harbored at least some E. tracheiphila cells may be .5 times higher than theportion of beetles that can, alone, transmit disease in a short time.
Abstract: Serological assays were used to estimate the proportion of Acalymma vittata (F.) that harbored Erwinia tracheiphila (E. F. Smith) Holland, the causal agent of bacterial wilt in cucurbits. These proportions were related to the proportion of A. vittata that transmitted disease in single beetle caged bioassays. The serological assays classified beetles as harboring the bacteria when the titer was above '10 5 cells per beetle. From 7.1 to 10.7% of the A. vittata captured as they emerged from soil that had been in cucurbits the previous year tested positive for the presence of E. tracheiphila. Also, from 0 to 8.3% of beetles captured on squash traps during this time of beetle emergence tested positive. This provides strong serological evidence for A. vittata serving as the primary overwintering reservoir for E. tracheiphila. During the growing season, the proportion of beetles testing positive with serological assays varied and ranged up to '53, 78, and 39% in 1995, 1996, and 1997, respectively. These serological proportions were 3.6—5.1 times higher than the proportion of beetles that trans- mitted disease in single beetle caged bioassays, and explained 44—49% of the variation in the proportion of beetles that were able to transmit disease in the caged bioassays. We suggest the proportion of A. vittata that harbored at least some E. tracheiphila cells may be .5 times higher than the proportion of beetles that can, alone, transmit disease in a short time. We discuss these data as supporting the hypothesis of beetle aggregation behavior as an important component of bacterial wilt epidemiology.
TL;DR: The influence of interspecific, intraspecific insect infestation, and mechanical damage of 3 host plant species on the attraction, landing, and oviposition of Mamestra brassicae (L.) was studied in a wind tunnel.
Abstract: The influence of interspecific, intraspecific insect infestation, and mechanical damage of 3 host plant species on the attraction, landing, and oviposition of Mamestra brassicae (L.) was studied in a wind tunnel. The presence of aphids did not affect the attraction, landing, or oviposition of mated females. However, when plants damaged by female locusts were used it was found that M. brassicae females were significantly attracted/landed and oviposited more often on the damaged plants than on undamaged cabbage plants. Mated females oriented significantly more often to cabbage plants damaged by conspecific larvae, compared with undamaged plants. Also, these females oviposited more on damaged plants than on control plants. When the damage was increased (from 20 to 80%), the females laid more on damaged plants, but the difference with respect to undamaged plants was not significant. When chrysanthemum plants damaged by M. brassicae larvae were used, mated females did not show any difference in attraction, landing, and oviposition between damaged or control plants. The females were initially attracted/landed and oviposited significantly more often on mechanically damaged cabbage plants, compared with undamaged plants. However, when mechanically damaged tomato plants were used, the mated females did not show any difference in the 1st attraction to damaged and undamaged tomato plants. But, these same females oviposited significantly more on undamaged plants than on damaged tomato plants.
TL;DR: Nematode load or mated status may negatively influence the ability of a beetle to locate food and oviposition sites in pinewood nematode-associated pine wilt.
Abstract: The pinewood nematode, Bursaphelenchus xylophilus ([Steiner & Buhrer 1934][1]) [Nickle 1970][2], and its cerambycid beetle vector, Monochamus carolinensis (Olivier) have a commensal relationship. The nematode is transported from infested to uninfested host trees by beetle vectors. The influence of nematode load, the number of 4th-stage dispersal juveniles (JIV) carried per beetle, and the mated status of female beetles on the flight performance of M. carolinensis were investigated using a flight mill. Beetles that carried >10,000 JIV had a significantly shorter flight distance and duration than beetles carrying <10,000 JIV. Unmated females outperformed their mated counterparts on all measures of flight. In North America, pine wilt is primarily associated with exotic, ornamental pines. The limited and widely separated distribution of these trees may require a long flight by M. carolinensis to locate feeding and oviposition sites. Thus, nematode load or mated status may negatively influence the ability of a beetle to locate food and oviposition sites.
[1]: #ref-23
[2]: #ref-18