摘要:

Mean development times at the chamber level for eggs, larvae, and pupae of the armyworm,Pseudaletia unipuncta(Haworth), were determined under daily temperature reigmes which yielded the same degree-day (DD) accumulation per day, but differed in the amplitude of temperature variation. Regimes with 0, 6.5, and 13°C amplitudes were tested at 9 and 14 DD/d accumulation rates. For each treatment combination, mortality and the distribution of development times were also determined. In general, all life stages developed more quickly under higher amplitude regimes. A nonlinear model predicted this developmental acceleration for some life stages under low accumulation rate regimes, but incorrectly predicted effects of amplitude under high accumulation rate regimes. Nonlinear development rates with respect to temperature and decreased high temperature inhibition were indicated. Other inexplicable effects were observed. Additional instars occurred in some insects descended from a Maryland collection, but never in insects descended from New York collections. Protogyny was observed.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1422

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The oviposition responses ofAtherigona soccataRondani, commonly known as the sorghum shootfly to seedlings of maize, which is not a host plant, that had been sprayed with acetone extracts of sorghum seedlings were investigated. Sorghum cultivars susceptible to the shootfly(CSH-1), resistant (IS 2122, IS 2123, and IS 2205), and wild sorghum,Sorghum arundinaceum(Desv.), were used. The possibility also was investigated of diverting shootfly egg laying in the field to maize sprayed with sorghum seedling extract. All of these extracts elicited significantly greater oviposition (67–91%) on treated maize seedlings than (9–33%) on untreated controls. Oviposition stimulant activity of CSH-1 extract decreased as the extracted plants grew older. The results suggest that a chemical oviposition stimulant is perhaps widespread among cultivated and wild sorghums, and it may serve as a kairomone in host finding and egg laying by the shootfly. In the field, maize seedlings sprayed with sorghum seedling extract served as good a host as the susceptible sorghum (‘Serena’) for shootfly oviposition. About 50–66% of shootfly eggs were laid on maize sprayed with sorghum seedling extract, either planted around sorghum or in strips alternating with strips of sorghum, compared with 6–17% laid on untreated maize. Because shootfly larvae cannot survive on maize, diverting oviposition onto maize would result in a reduction of the pest population. Our studies demonstrated the potential for using an oviposition stimulant for diverting shootfly eggs onto nonhost plants as a strategy for the management of the pest.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1432

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The biology of the alfalfa weevil,Hypera postica(Gyllenhal), was studied in Louisiana during 1986 to 1988 on alfalfa,Medicago sativa(L.). Post-estivation migration of adults in the fall occurs during late November and early December. Fall oviposition during December and January resulted in 58 to 81% of alfalfa stems with egg clusters. Egg viability of eggs laid in the fall was estimated at 75%. Alfalfa weevil egg clusters contained an average of 10.9 (1986–1987) to 13.3 (1987–1988) eggs per cluster. The position of egg clusters in the alfalfa canopy, relative to the base of the stem, indicated that 95 and 50% of all clusters were below 40 and 18 cm, respectively. An ovipositional preference was found with eggs generally laid between the upper 30% and lower 80% regions of the alfalfa stem. Alfalfa weevil larvae were first detected in February. Egg eclosion in 1987 was highly synchronized as indicated by larval counts increasing from 4 to 90 per sweep between 3 and 10 February. In 1988, larval emergence gradually increased from 4 February (≦10/sweep) to 3 March (60/sweep). Head capsule widths were 0.15, 0.28, 0.42, and 0.55 mm for first, second, third, and fourth instars, respectively. Corresponding body lengths were 1.4, 2.8, 4.6, and 6.6 mm for first, second, third, and fourth instars, respectively. The marked decline of alfalfa weevils in April is presumably indicative of adult migration from alfalfa to summer estivation sites. Degree-day accumulations are used to describe and predict spring hatch of the alfalfa weevil in Louisiana.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1443

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Temperature preference and effects of photoperiod on oviposition behavior of five species of pteromalid wasps were investigated using house fly pupae,Musca domesticaL.. as hosts. All five species were exposed to treatments (temperature and photoperiod) for 24 h and then held at 25°C for progeny development. Mean parasitoid emergence for the five species in descending order wasMuscidifurax raptorGirault&Saunders (46%).Pachycrepoideus vindemiaeRondani (37%),M. zaraptorKogan&Legner (26%),Urolepis rufipesAshmead (14%). andSpalangia nigroaeneaCurtis (<1%). Length of photophase (6, 12, or 18 h) did not significantly effect parasitoid emergence for any species. Temperature, however, had a significant effect on oviposition behavior, and the five species appeared to respond differently to the different temperature levels (20, 25, and 30°c). Temperature had a significant quadratic effect on oviposition behavior ofM. raptor,P. vindemiae, andU. rufipes. Emergence levels ofM. raptorwere highest from hosts held at 25 and 30°c. Emergence ofP. vindemiaeandU. rufipeswas highest from hosts held at 25°C. Temperature had a significant linear effect on the oviposition behavior ofM. zaraptor; highest emergence occurred from hosts held at 30°C. Emergence levels forS. nigroaeneawere too low to make comparisons between treatments. Effects on fly eclosion, sex ratios, and parasitoid-induced mortality for the five species are reported along with possible reasons for lowS. nigroaeneaemergence.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1452

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Mortality of boll weevil,Anthonomus grandisBoheman, larvae and pupae resulting from exposure to high temperatures can be partitioned into two categories, “desiccation” and thermal death. Larvae and pupae that die from thermal death turn a greybrown color after death, do not move when probed or squeezed, and lose the resiliency of their integument. Those dying from “desiccation” will show the same characteristics but do not turn the grey-brown color; they generally retain the same color as live insects but have a very dried-out appearance. Thermal death is a function of exposure time and high temperatures. Low levels of thermal mortality appear in ≤3 h at 54.4°C. An estimated 99% mortality should result from a 2-h 18-min exposure at 60°C. Because soil surface temperatures sometimes reach 60°C, high temperatures may be an important cause of mortality in some locations. A model for forecasting time and temperature thresholds for thermal mortality is presented.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1457

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Effects of host and nonhost substrates on probing and preoviposition activity were monitored for adult summerform pear psylla,Cacopsylla pyricolaFoerster. Tendency to initiate probing activity during a 15-min observation period was similar on a susceptible pear (Pyrus communisL. ‘Bartlett’), a presumed nonsusceptible pear (P. calleryanaDecne.), and apple, but was reduced on quince. Depriving pear psylla access to pear for 4–6 h or 14–16 h before the observation period increased the percentage of psylla that probed during the observation period; effects of host deprivation on tendency to probe were independent of substrate. Tendency to initiate probing onP. communiswas greater on lower leaf surfaces than upper leaf surfaces, which may suggest that probing is initiated in response to cues received at the leaf surface. The percentage of pear psylla that probed during the observation period was not affected by age ofP. communisfoliage. Mean probe duration and mean percentage of the 15-min observation period spent probing were unaffected by substrate; both measures increased linearly with amount of time that pear psylla were deprived of pear before the observation period. Mean percentage of the observation period spent in contact with the leaf surface was higher forP. communisandP. calleryanathan non-Pyrusspecies. Despite extensive probing activity on apple, very little preoviposition behavior was noted; similarly, age ofP. communisfoliage did not affect tendency to initiate probing behavior, but did affect preoviposition activity. These two results suggest that probing and preoviposition activities were released by different cues.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1463

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Leptocorisa oratorius(F.) adults preferredEchinochloa cruz-galli(L.) over rice,Oriza sativaL., var. IR 36, for resting sites, whereas rice was preferred overEleusine indica(L.),Echinochloa colona(L.),Brachiaria mutica(Forsk.),Paspalum conjugatumBerg.,P. paspalodesL., andDigitaria ciliaris(Retz.).L. oratoriusoviposited on all plant species, but those confined for 8 d on flowering rice laid more eggs than those confined on weeds. Females began oviposition 2 wk after molting, and fecundity was consistent for 5 wk. Nymphs completed their development only onE. cruz-galli,E. colona,D. ciliaris, or rice after panicle emergence. Results indicate that weed control is an important factor inL. oratoriusmanagement programs.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1469

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

This study presents concurrent measurements of the vertical profiles of aphid density and airstream temperature within the planetary boundary layer over east-central Illinois for 16 collection periods during a variety of synoptic weather conditions in the 1984 and 1985 growing seasons. Aphid density was determined at a fine altitudinal resolution between the ground surface and an altitude of ≈1,000 m using two helicopter-mounted collectors. These collectors allowed sampling of insects at>20 altitudes in a single flight, captured insects in a condition that permitted easy identification, and permitted accurate calculations of air volume and insect density. Vertical distribution of aphids on individual collection days was interpreted with respect to lapse rate of air temperature. The results of this study indicate that inversion layers produce stratification of aphids in the atmosphere and that aphids migrating into the Midwest are concentrated in zones within the planetary boundary layer.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1473

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The population dynamics of the woolly whitefly,Aleurothrixus floccosus(Maskell), and its parasites on citrus were studied in an interior valley citricultural region of California. The development of populations was followed by leaf sampling and field observation from the initial pest colonization of the study site through 3 consecutive yr. The two major natural enemies found wereCales noackiHoward andEretmocerussp. Early in the study,C. noackidisplacedEretmocerussp. as the dominant parasite present. Parasitism byC. noackiwas responsible for substantial reductions in the whitefly population. High summer temperatures appeared to have a disruptive effect on biological control of the woolly whitefly by inhibiting the increase of parasite populations while pest population growth continued. However,C. noackipopulations recovered during cooler weather and apparently were able to effect rapid suppression of the whitefly outbreak.

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1485

出版商:Oxford University Press    

年代:1990

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/19.5.1491

出版商:Oxford University Press    

年代:1990

数据来源: OUP