摘要:

A model (BIOCONTROL-PARASITE) that simulates host and parasitoid population interactions, parasitism rates, and plant damage is described. BIOCONTROL-PARASITE can simulate many different species of phytophagous insects, parasitoids, and plants because specifics of the insect and plant biology are entered through menus at the beginning of a simulation. Augmentative releases of egg and nymphal parasitoids also can be simulated. The accuracy of BIOCONTROL-PARASITE predictions was tested by comparing them with field estimates ofLygus hesperus(Knight), in an alfalfa agroecosystem withAnaphes iole(Girault), andLeiophron uniformis(Gahan) as egg and nymphal parasitoids, respectively. BIOCONTROL-PARASITE predictedL. hesperusnymphal and adult populations, egg and nymphal parasitism rates, and plant state with reasonable accuracy. Simulations with and without parasitoids predicted that egg and nymphal parasitoid populations created by way of augmentative releases would reduce theL. hesperuspopulation, but would not greatly decrease feeding damage and subsequent loss of alfalfa seed. Simulations predicted that releasing both egg and nymphal parasitoids would decreaseL. hesperusegg, nymphal, and adult populations slightly below levels achieved by releasing only egg parasitoids. Estimates of seed yields from simulations with and withoutL. hesperusindicated that about one-third of the alfalfa seed crop would be eaten byL. hesperus.Using BIOCONTROL-PARASITE as a tool for identifying parasitoid species that might be candidates for mass rearing and release as biocontrol agents and to test the applicability and realism of data collected from laboratory experiments of host-parasitoid interactions is discussed. The assumptions and limitations of the model also are described.

DOI:10.1093/ee/23.5.1045

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The application of the concept of committed phloem ingestion (CPI) of aphids was studied for different aphid species feeding on resistant and susceptible plants. Greenbugs,Schizaphis graminum(Rondani) (biotype E), were monitored electronically on wheat,Triticum aestivumL., andSorghum bicolor(L.) Moench, cultivars, and Russian wheat aphids,Diuraphis noxiaMordvilko, were monitored on wheat cultivars. The duration of phloem ingestion (PI) events of these aphids was not randomly distributed and ≍53% of them were<60 min in duration. The minimum PI duration to be considered as committed feeding (threshold of CPI) was determined for each aphid–host combination. Thresholds varied depending on the aphid species and host plants, indicating the difficulty of assigning a single threshold value that could be useful as a measure of host acceptability. Also, if a given threshold duration is chosen as a criterion for having achieved CPI (e.g., 15 min), the proportion of PI events that continues for a long time period varies from host to host. Therefore, we recommend that use of this parameter be discontinued, and that measurements of the time from the beginning of the experiment to PI and the time from the initiation of a probe to PI be substituted for time to first CPI.

DOI:10.1093/ee/23.5.1061

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Parasitoids constitute an important component of the biodiversity of terrestrial ecosystems and have become a recent focus for investigations of pattern and process in ecological communities. This article uses parasitoid guilds to characterize the structure of parasitoid communities associated with endopterygote hosts. Parasitoid guilds are defined by three parameters, the host stage attacked, the host stage killed, and the mode of parasitism (internal or external development). A series of 12 guilds are recognized from the patterns of host exploitation by parasitoids; one that utilizes the host egg stage as a resource for parasitoid development, three that utilize the host larva, four that utilize the host prepupa, two that utilize the host pupa, and two that utilize the host adult. A comparison of the parasitoid guilds across endopterygote host orders illustrates the taxonomic diversity of parasitoids in each guild and provides an indication of some of the more frequent parasitoid taxa associated with each guild. The value of the parasitoid guild as an ecological unit that both classifies the functional ecology of parasitoid species and the structure of parasitoid communities is discussed.

DOI:10.1093/ee/23.5.1066

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Fruittree leafroller,Archips argyrospila(Walker), obliquebanded leafroller,Choristoneura rosaceana(Harris), and European leafrollerArchips rosana(Robinson), all use Z11–14:OAc and E11–14:OAc as components of their species-specific pheromone blends. Small-plot experiments (0.09 ha) were conducted in the Okanagan Valley of British Columbia to evaluate the effects of atmospheric permeation with different concentrations of Z11–14:OAc and E11–14:OAc, applied in a ratio of 93:7, on pheromone communication of these sympatric species. The relative response of male moths to synthetic and natural pheromone-baited traps in pheromone-treated and untreated plots was used to measure disruption of pheromone communication. The pheromone-disruption blend was released by polyethylene tube-type dispensers applied at various densities. Catches ofA. argyrospilain synthetic pheromone traps decreased by>92 and 97% when pheromone was applied at rates of 5–10 mg/h/ha and 20–40 mg/h/ha, respectively. Catches ofA. argyrospilain virgin female-baited traps were reduced by 99% at pheromone application rates of 20–40 mg/h/ha. Catches ofC. rosaceanaandA. rosanain synthetic pheromone-baited traps decreased by 88–96% when the pheromone disruptant was applied at rates of 20–40 mg/h/ha. In pheromone-disrupted plots, more maleA. argyrospilawere caught in traps baited with pheromone blends ofC. rosaceanaandA. rosanacontaining a higher percentage of Z11–14:OAc than the reported pheromone blend ofA. argyrospila.These results suggest an alteration of the normal pheromonal response ofA. argyrospilaon exposure to a high concentration of Z11–14:OAc for a sustained time.

DOI:10.1093/ee/23.5.1084

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Wild geranium,Geranium dissectumL., was treated between late March and early April to control the F1larval generation of the tobacco budworm,Heliothis virescens(F.), and bollworm,Helicoverpa zea(Boddie). Treatments were a single mowing, a single application of the herbicide (2,4-dichlorophenoxy) acetic acid (2,4-D), four applications ofHeliothisnuclear-polyhedrosis virus (Elcar) formulated withBacillus thuringiensis(Thuricide) and Gustol (a feeding stimulant), and an untreated check. Tarnished plant bugs,Lygus lineolaris(Palisot de Beauvois) and beneficial arthropods were sampled weekly during a 7-wk period to determine effects of the treatments on their numbers. The Elcar (virus) treatment had no significant effect on numbers of beneficial arthropods orL. lineolaris.Beneficial arthropod numbers were reduced by the mowing and 2,4-D treatments by an average 56.5 and 45.6% (as compared with those in the untreated check), respectively. Tarnished plant bug numbers were reduced by an average 40.5% for adults and 78.8% for nymphs by the mowing treatment, while reductions averaged 65.3% for adults and 72.9% for nymphs after the 2,4-D treatment. The effectiveness of mowing and 2,4-D treatment in reducing numbers ofL. lineolaris, along with their previously reported effectiveness against F1larvae ofH. virescensandH. zeafound inG. dissectum, make these treatments potentially valuable control options for the three pests during the early season before their movement into cotton.

DOI:10.1093/ee/23.5.1091

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Knowledge of the distribution of counts of an insect is an essential element for development of a sequential sampling plan. The objectives of this study were to determine the spatial distribution of red sunflower seed weevil,Smicronyx fulvusLe-Conte, counts in sunflower, and to determine the effect of plant stage on the density. Taylor's power law, Iwao's patchiness regression, and the negative binomial probability model were used to analyze the data. All three indices (b, β, andk) indicated an aggregated distribution of the weevil. Taylor's power law provided a better description than Iwao's patchiness regression. The negative binomial distribution parameterkwas not dependent with mean density, indicating the presence of a commonk(kc). The estimates ofkcranged from 0.4587 to 0.5255. Plant growth stage had a significant effect on the density of the weevil. When most plants were in the bud stages, more weevils were always found in the blooming sunflower heads (>R5.0 stage). When plants were in the anthesis stage (R5.0–6.0), the adult weevils preferred plants of stage R5.4–6.0, which were suitable for oviposition.

DOI:10.1093/ee/23.5.1101

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Lygus bug,Lygus hesperusKnight, and beneficial insect populations (Oriussp.,Geocorisspp., andNabisspp.) were quantified in alfalfa strips, which were interplanted within cotton fields. The propensity of alfalfa strips to retain lygus bugs, thereby keeping them out of cotton, and the utility of alfalfa strips as a reservoir for beneficial insects were evaluated from May to August in 1990 and 1991. The following three alfalfa cutting strategies were examined: (1) uncut alfalfa, (2) a 28-d strip-cut treatment, and (3) a 35-d strip-cut treatment. Insect populations were quantified in both the newer alfalfa growth and the older alfalfa growth of the strip-cut treatments. Lygus bug densities were significantly higher in the uncut treatment than in the other treatments, peaking at 520 per 1.9 m2in 1990 and 350 per 1.9 m2in 1991. Lygus bug levels in the strip-cut treatments were low in the newer alfalfa growth (averaging 41.8 per 1.9 m2) and only slightly higher in the older alfalfa growth of the 28-d strip-cut treatment (averaging 65.3 per 1.9 m2). Populations were relatively constant within these three treatments throughout the season. However, in the older growth of the 35-d cutting regime, Lygus bug populations averaged 103 per 1.9 m2. Densities of beneficial insects were also higher in the uncut than the strip-cut treatments, but the higher predator densities apparently did not offset the high Lygus bug population increase. The uncut treatment also lacked Lygus bug egg and nymphal mortality from the alfalfa cutting as compared with the strip-cut treatments. The less frequent cutting, in the 35-d compared with the 28-d treatment, probably also allowed for a buildup of the Lygus bug population. Lygus bug instar distribution, sex, and predator species were also examined in these treatments. It appears that to optimize Lygus bug management, while still producing high densities of predacious insects, strip-cut alfalfa should be used and cut on a 28-d schedule.

DOI:10.1093/ee/23.5.1106

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Estimates of pupation depth in soil for Caribbean fruit flies,Anastrepha suspensa(Loew), are important to future development of sampling and management techniques in fruit groves in southern Florida. Colony-reared, late third instars were placed onto soil surfaces in containers and allowed to burrow and pupate. Experimental units consisted of one larva per container. Soil in containers had a volume of 740 ml, surface area of 95 cm2, and depth of 9 cm. Pupae were excavated from soil after 72 h and their depths were recorded. Soil moisture (10 and 50% field capacity), type (muck, marl, and loam) and compaction (low and high bulk density) were the independent variables tested for their effects on pupation depth. Mean depths ranged between 0.7 cm (loam, 50% field capacity) and 3.3 cm (muck, 10% field capacity, low bulk density). Means differed Significantly because of compaction and the interaction of moisture × compaction. Larvae pupated at a greater depth in soils of low compaction than in soils of high compaction. The difference in depth between low and high compaction was greater for soils of low moisture than for soils of high moisture. The pupation rate was 100% for all treatments. Mean adult emergence rates ranged between 66.7 and 100% but did not differ significantly among treatments.

DOI:10.1093/ee/23.5.1119

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Experiments to determine the effectiveness and time required to sample for males of the European corn borer,Ostrinia nubilalis(Hübner), with blacklight, water-pan,Heliothis-cone, and delta-wing traps, along with sweep-net samples of grassy areas near potato fields were conducted at four sites in 1990 and 1991 on Prince Edward Island. Compared with the blacklight trap, the water-pan trap caught 1.72 times more males in 1990 and 1.97 times more males in 1991. TheHeliothis-coneand delta-wing traps, and sweep-net samples were ineffective for male European corn borer. Blacklight traps required significantly more time to sample than any of the pheromone-based traps. A waterpan trap is an effective tool to monitor adult males of the European corn borer in potatoes on Prince Edward Island. In 1992, the mean number of males per pan trap per week was 7.4 for the Iowa strain, 1.1 for the New York strain, 0.6 for the hybrid strain, and 1.1 for an unbaited trap. This suggests that the Iowa strain predominates in the population of European corn borer on Prince Edward Island.

DOI:10.1093/ee/23.5.1124

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Markov-recapture population size estimates rely on insects (or other animals) marking themselves before arrival in a trap. Assumptions about rates of marking and capture are based upon the sampling scheme, and the estimate is based on the resulting multinomial probability distribution. The original scheme used one marking station per trap, yielding an assumption of equal rates of marking and capture. This paper explores more general schemes that provide better resolution, sometimes with added degrees of freedom, and which provide estimates more quickly than the original scheme (reducing the risk of violating assumptions). The alternative schemes involve varying the ratio of marking stations to traps and multiple marking. The paper continues to describe the maximum likelihood estimates of population size based on these sampling schemes and gives a rough correction for the bias of the population estimate, found by using a jackknife technique. Two standard error confidence limits are explicit expressions obtained using asymptotic maximum likelihood arguments; these work well in conjunction with the corrected estimate if trapping has continued for an extended period. Relative likelihood-based confidence intervals perform better than two standard error intervals over a wide range of parameter values, especially where trapping has not continued for an extended period. The method tends to become biased when used in an open or growing population. Goodness-of-fit tests are possible with the added degrees of freedom but are not very powerful.

DOI:10.1093/ee/23.5.1129

出版商:Oxford University Press    

年代:1994

数据来源: OUP