摘要:

Ninety-four unmanaged lodgepole pine stands, from a broad geographical range in the western United States, were examined to evaluate the relationship between stand density and susceptibility to mountain pine beetle (MPB),Dendroctonus ponderosaeHopkins, attack. Population trends were not significantly related to variation in stand density as measured by stand density index (SDI). Percentage of trees killed per hectare by MPB in stands with>80% lodgepole pine did vary significantly with changes in SDI. From these data three SDI zones were identified as follows: 1) stands with SDI's of<125 showed low potential for attack, 2) stands between 125 and 250 SDI showed much greater levels of tree mortality, gradually decreasing toward the 250 SDI, 3) tree mortality decreased in stands as density increased beyond the 250 SDI value.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.738

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Damage potential of fourth- to sixth-instar larvae ofAgrotis ipsilon(Hufnagel) on one- to five-node cotton planted no-till into crimson clover was studied in barrier-enclosed plots. The percentage of cut plants decreased progressively with plant age as in a previous greenhouse study. However, depending on infestation category, only 17–42% as many plants as expected were cut from damage by individual larvae observed in the greenhouse. Duration of cutting activity expressed in cumulative degree-days was very similar to that in the greenhouse, but only half that expected from developmental rates at constant temperature in the laboratory.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.743

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

In bagged grain, probe traps baited with 50 µl of dominicalure 1 released from rubber bands were attractive to lesser grain borer,Rhyzopertha dominica(F.). For aerial trapping, dominicalure was a powerful attractant both inside a warehouse and outdoors. Dominicalure 1, dominicalure 2, and mixtures were equally attractive. On average, pheromone traps captured 8- and 152-fold more insects than check traps inside the warehouse and outdoors, respectively. The Lindgren funnel trap had a significantly greater capture than six other designs tested. Of four dispenser types tested, the O.4-ml polyethylene test tube retained activity longest, up to 30 d under summer conditions. Best aerial trap placement was along walls close to the ground. Trap catch increased with increasing pheromone release rate.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.747

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Field data on preimaginal survival of bluegrass billbug,Sphenophorus parvulusGyllenhal, were collected weekly for three summers, 1982–84, from a hybrid wheatgrass,Elytrigia repens(L.) Nevski ×Pseudoroegneria spicata(Pursh) Löve, nursery near Kaysville, Utah. Population estimates were based on stem samples for early life stages and soil samples for later life stages. Locations of adult feeding and oviposition on host plants were the same. Seasonal populations were similar in all years except for a rapid decline of late instars in 1983. There was much overlapping of life stages, with early instars extending late into the season. Greatest mortality was during the egg stage (40–75%). Larval mortality was high (49–63%) for the root-feeding middle and late instars. Pupal mortality was low (0–16%)for all seasons. No predators, parasites, or pathological agents were found. Implications of bluegrass billbug successfully attacking an unnatural host, a rangeland wheatgrass, are discussed

ISSN:1754-5692    

DOI:10.1093/ee/16.3.752

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Electronically monitored feeding behavior, reproduction, and honeydew production of greenbug,Schizaphis graminum(Rondani), biotypes C (GBC) and E (GBE) were studied on three genotypes of wheat,Triticum aestivumL. We studied resistant and susceptible plants to determine how host-plant genotype alters greenbug feeding behavior and honeydew production on wheat and the relationship between feeding behavior and greenbug resistance. Greenbugs monitored for 24 h on resistant plants performed recognized behaviors (stylets withdrawn from plant, probing, salivating, and ingesting from phloem) 2- to 3-fold more frequently than on susceptible plants. Average duration of a given behavioral event was not modified by resistance, except in the case of phloem ingestion. Total time over 24 h spent with stylets withdrawn from the plant was increased on resistant plants, as was total salivation time, whereas total time spent ingesting from phloem was reduced. Greenbugs on susceptible plants achieved phloem ingestion longer than 15 min within 30 min of the first phloem contact, but those on resistant plants failed to achieve this for up to 4 h. Honeydew production over 5 d was unaffected by host plant. Resistant plants induced greenbugs to expel more honeydew per unit dry-matter weight gain. The data suggest that the greenbug's ability to damage its host plant may allow it to more quickly accept nutritionally enriched phloem sap associated with feeding damage and may result in production of larger, more fecund greenbugs.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.757

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Beach strawberry,Fragaria chiloensis(L.) Duchesne, clone CL-5, is resistant to feeding by adult black vine weevil (BVW),Otiorhynchus sulcatus(F.). Using a membrane filter feeding bioassay, no evidence for a chemical basis for this resistance could be obtained. Leaf toughness of a susceptibleFragaria×ananassa(Duchesne) cultivar and clone CL-5 did not differ. Removal of tomentum from the underside of fresh or freeze-dried CL-5 leaf disks rendered them as susceptible to BVW feeding as disks from a nonresistant cultivar. This, and other evidence, demonstrates that antixenosis exhibited by leaves of beach strawberry clone CL-5 to BVW is due, at least in part, to the dense covering of simple hairs on their abaxial surface.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.764

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Third-instar larvae ofMusca domestica, Ophyra aenescens, Fannia canicularis, andFannia femoraliswere exposed to parasitic nematodes in the laboratory. Four strains ofSteinernema feltiae, two ofSteinernema bibionis, and one ofHeterorhabditis heliothidiswere tested on moist filter paper in petri dishes. Considerable variability in infectivity within and among hosts was noted for the different nematode strains. Strains ofS. feltiaewere more infective thanS. bibionisorH. heliothidis, but all could infect the four hosts.F. femoraliswas highly resistant to infection byS. bibionisandH. heliothidis.Further tests on chicken manure and fly rearing medium showed that infectivity of several nematodes forM. domesticaandF. canicularislarvae was markedly less than on filter paper.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.769

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

In 1983, alfalfa seed chalcids (ASC),Bruchophagus roddi(Gussakovsky), emerged from overwintered alfalfa,Medicago sativaL., seeds between 2 May and 5 August. In 1984, this emergence occurred between 15 April and 3 August. Seeds were sorted from screenings that had been collected in the fall in 1982 and 1983 from four locations in Oklahoma. Peak emergence of ASC was in mid-June, with significantly higher emergence occurring during the entire month of June. ASC emerged earlier at lower elevations and at more southern locations than at higher elevations or at the most northern location. Male ASC emerged earlier and in greater numbers than females until early June. Thereafter, more females emerged. Overall, 60% of emerging ASC were female. A small number of ASC (39) emerged the second year (1984) from seeds collected in the fall of 1982.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.774

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Spider fauna was sampled in 1983 and 1984 from action sites of adult European corn borer (ECB),Ostrinia nubilalis(Hübner). The ground-dwelling spider community was best characterized as a hunting guild and consisted primarily of Lycosidae, Thomisidae, and Gnaphosidae. A gnaphosid species,Gnaphosa parvulaBanks, is a new state record for Iowa. Total ground spiders reached greatest numbers by June and declined thereafter. The foliage-dwelling spider community was characterized as both an orb-web guild and a hunting guild. Tetragnathidae, Araneidae, Salticidae, Thomisidae, and Oxyopidae accounted for 89% of the foliage-inhabiting spiders. Effects of carbaryl and fenvalerate applied for adult ECB control were tested on the spider fauna in action sites. Spider populations were generally not affected, except for the foliage spider family, Tetragnathidae, whose numbers were significantly reduced for 28 d in 1984 in treated action sites. It is suggested that beneficial spider populations, particularly ground-dwellers, could be protected from adverse effects of insecticide treatments if treatment was timed to miss peak densities and the application was primarily directed at the upper foliage canopy

ISSN:1754-5692    

DOI:10.1093/ee/16.3.779

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Standard ‘Golden Delicious’ and ‘Stayman’ apple trees were sampled to determine spatial patterns of tufted apple bud moth,Platynota idaeusalis(Walker). Trees were divided into upper and lower levels vertically, and directionally into areas of the tree facing the row alleyway (BROW) and areas of the tree facing the tree row (WROW). In 1982 in unsprayed trees, significantly more summer-brood egg masses were deposited in the upper areas. Significantly more fall-brood egg masses were deposited in the upper and BROW areas. In 1983, low numbers of summer- and fall-brood egg masses were found, and there were no differences between levels or between row directions. Both broods of larvae were located more in the lower than upper levels. In sprayed trees, more larvae were found in the WROW areas, but in unsprayed trees there was no difference between row directions. Calculated sample sizes were large because of low proportions of infested spurs.

ISSN:1754-5692    

DOI:10.1093/ee/16.3.786

出版商:Oxford University Press    

年代:1987

数据来源: OUP