摘要:

The flea beetlePhyllotreta cruciferae(Goeze) is selective of its host plants, both between cultivars and between plants of different ages within cultivars. Previous work has associated these preferences with chemical differences between plants. Factors suspected of affectingP. cruciferaebehavior, including host plant chemistry and morphology, were isolated and examined in laboratory assays.P. cruciferaefed equally well on collard and kale cotyledons in both choice and no-choice assays. During 15-min observation periods, flea beetles spent more time on cotyledons than on older leaves of either cultivar. Injured collard and kale cotyledons were fed upon more than uninjured cotyledons in both choice and no-choice assays, and this preference is associated with release of chemical cues from the host. Leaf morphology, however, also affected flea beetle behavior. During 15-min observation periods,P. cruciferaespent more time on 6-wk-old collard leaves than on 6-wk-old kale leaves, and on collard leaf models than on kale leaf models treated with identical leaf extracts. Laboratory results indicate thatP. cruciferaehost preference is associated with chemical and morphological differences and help explain the spatial patterns in population density observed in the field.

DOI:10.1093/ee/22.2.418

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Baseline data were collected on the natural occurrence of the nuclear polyhedrosis virus ofAnticarsia gemmatalis(Hübner) in Louisiana and Texas in preparation for future attempts at introduction and establishment of the virus. The virus was not detected inA. gemmatalislarvae collected from 12 sites in Louisiana or 2 sites in Texas (total n = 3,391) on numerous sampling dates in 1989 and 1990. The only exception was a possible, light infection in one insect collected at a site that had been sprayed withA. gemmatalisnuclear polyhedrosis virus during 1979–1981. The virus was not detected in any of 24 soil samples collected from two sites in Louisiana in spite of detection of as few as 15.9 polyhedral inclusion bodies per g of soil in positive controls. Attempts were made in the laboratory to determine whether the viral infections could persist in adults and be transmitted to the progeny. TheA. gemmatalisnuclear polyhedrosis virus was not so transmitted, even thoughSpodoptera frugiperda(J. E. Smith) adults, the positive control, transmitted their homologous nuclear polyhedrosis virus to 14.3% of their progeny. It is hypothesized that a lack of vertical transmission is the reason that theA. gemmatalisnuclear polyhedrosis virus apparently is not indigenous to the United States.

DOI:10.1093/ee/22.2.425

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Bacillus thuringiensisBerliner toxicity is a dose-dependent phenomenon, and the dose acquired by an individual is directly related to the quantity of treated food consumed. A bioassay was conducted using twoApium graveolens var. rapaceum(L.) cultivars to determine if theB. thuringiensisdose acquired bySpodoptera exigua(Hübner) (Lepidoptera: Noctuidae) larvae was influenced by host plant-induced variation in consumption rates.S. exiguafed the cultivar more suitable for larval growth and development consumed significantly greater leaf surface areas, survived longer, and grew faster than larvae fed the less suitable cultivar.S. exiguafedB. thuringiensis-treated foliage consumed significantly smaller leaf surface areas, had significantly shorter survival times, and grew slower than larvae fed untreated foliage. When leaf surface area consumption was adjusted to reflect theB. thuringiensisconsumed, larvae fed the more suitable cultivar received significantly higher cumulativeB. thuringiensisdoses, but this difference did not explain the observed differences in insect performance. The fact that larvae fed the more suitable cultivar received a greaterB. thuringiensisdose than larvae fed the less suitable cultivar demonstrates that host plant-induced variation in consumption rates can affect theB. thuringiensisdose a herbivore receives. In this particular case, larvae that received the overall greaterB. thuringiensisdoses performed better than larvae that received the overall lower doses, indicating that other factors associated with the host plant play an important role in mediatingB. thuringiensisefficacy.

DOI:10.1093/ee/22.2.432

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Densities of males of the leafrollerArchips podanawere determined by pheromone traps in the Lipetsk district, central Russia, in 1991. Industry emissions at Lipetsk contain especially sulphur dioxide. Densities ofA. podanapeaked at 3–7 km from the nearest source of emission. Male sizes (indicated by length of the aedeagus) tended to be smaller close to heavily polluted areas but did not correlate significantly with densities. Variation in size also peaked close to emission sources.

DOI:10.1093/ee/22.2.438

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The variation in number of European pine sawflies,Neodiprion sertifer(Geoffroy), caught in pheromone traps during 11 d of the peak flight period was in part explained by the weather, measured by a weather station at the study site. Daily average air temperature was the most important variable and was positively related to the log catch; it explained 86% of the variation. A threshold for flight was determined to be ≍+ 11°C. Rain during most of the day inhibited flight, but occasional showers did not. Wind velocity and humidity did not increase the explained part of the variation significantly in a multiple regression model after inclusion of air temperature. Trap sample and weather-recording intervals<1 d did not enhance the correlations. An all-season study showed low correlation between catch and temperature because of varying background population and a considerable distance to the meteorological stations where the temperature data were collected.

DOI:10.1093/ee/22.2.445

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

On potted host trees in field cages, we evaluated effects of source and condition of excrement from domestic and feral animals on attractiveness to released laboratory-cultured and wild Mediterranean fruit flies (medflies),Ceratitis capitata(Wiedemann). Compared with PIB-7, which is a widely used proteinaceous attractant in bait sprays against medflies, droppings from domestic gamecocks, gamehens, chickens, and feral geckos (lizards) were significantly more attractive, droppings from feral Myna birds were equally attractive, and droppings from horses, cows, goats, and pigs were significantly less attractive. All of these substances were significantly more attractive than water alone. Gamecock droppings collected within 24 h of deposition proved most attractive when tested a few hours after collection or 1 d after removal from cold storage. They were less attractive when tested 2–3 d after collection or a few hours after removal from cold storage. Differences in attractiveness among droppings may be attributed to differences in nitrogen excretion systems and diets among animals from which droppings were collected and to differences in composition and quantity of bacteria associated with droppings. We conclude that chemically characterizing the odor of relatively fresh droppings from birds such as gamefowl or chickens receiving high-protein diets could lead to improved lures for monitoring or eventually controllingC. capitatafemales.

DOI:10.1093/ee/22.2.453

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We determined whether wing lengths ofCulex tarsalis(Coquillett) andAnopheles freeborni(Aitken) varied seasonally; whether size was associated with abundance; and if individuals of a particular size could be associated with riparian, pasture, or rice field habitats within the rice culture agroecosystem of northern California. Significantly, the size of both male and femaleCx. tarsalisincreased as the season progressed. The size of femaleAn. freebornialso increased significantly throughout the season, but the size of males did not. Abundance was not correlated with average wing length nor could any habitat be significantly associated with a particular size group. We conclude that for the species studied here, environmental effects (such as water temperature and seasonal availability of larval nutrients) are more important in determining individual size than the density-dependent processes that regulate the size of mosquitoes that breed in small containers.

DOI:10.1093/ee/22.2.459

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Collections of volatiles were obtained from calling males of the Caribbean fruit fly,Anastrepha suspensa(Loew), under natural light cycles in tests conducted in a greenhouse and compared with collections from males tested under standard laboratory conditions. There was no effect on total amount of pheromone or in amounts of individual components released between 0400 and 2100 hours (EST); i.e., from 2 h before until 2 h after a 12-h photophase. Pheromone periodicity under either regime was fit best by a bimodal distribution, but there were shifts in times of peak production. Under laboratory conditions, there was a small early morning peak at the start of photophase (0600 hours) and a broad afternoon peak ≍4 h before the end of photophase. Under greenhouse conditions, there was a small, broad early morning peak at 0700 hours and a sharp afternoon peak at ≍1700 hours. Flies in the laboratory released significantly higher amounts of volatiles from 1230 to 1630 hours, whereas those in the greenhouse produced Significantly higher levels from 1700 to 2100 hours. Under greenhouse conditions, pheromone production was positively correlated with relative humidity and negatively correlated with light intensity, as indicated by overall light levels measured in lux. It is speculated that high light intensities and low relative humidity, to which males under natural light cycles are exposed, inhibit pheromone production during the middle part of the day, and that environmental variables work in concert with circadian rhythm to control periodicity of pheromone release.

DOI:10.1093/ee/22.2.464

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Ice-nucleating-active bacteria,Pseudomonas syringae(strain 31a), applied as a freeze-dried powder on grain in laboratory tests, caused an increase in the ice-nucleating activity of the grain and an increase in the supercooling point ofCryptolestes ferrugineus(Stephens) adults.Sitophilus granarius(L.) andOryzaephilus surinamensis(L.) also had increased mortality when placed on grain treated with ice-nucleating-active bacteria and held at -lO°C. Cold-acclimatedC. ferrugineus,S.granarius, andO. surinamensiswere more cold hardy than noncold-acclimated insects, but when these insects were held on grain treated with ice-nucleating-active bacteria, their mortality at -1O°C was increased. These results were confirmed in a simulated granary application whenC. ferrugineusadults were placed in vials with 10 g of ice-nucleating-active bacteria-treated wheat before being placed in granaries containing 100 t of grain. Two of the three bins were aerated until the temperature had reached −9 or −15DC. Ice-nucleating-active bacteria increased insect mortality in the aerated bins at bacterial concentrations as low as 10 ppm. The potential of using ice-nucleating-active bacteria as a cold synergist that will make low temperature a more effective means to control stored-product and other insect pests is discussed.

DOI:10.1093/ee/22.2.470

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Predation experiments were conducted in the laboratory to study the potential effect ofOrius tristicolor(White) on the widely used spider mite predator,Phytoseiulus persimilisAthias-Henriot (Acarina: Phytoseiidae). In a 24-h test on English cucumber leaf disks surrounded by a water barrier, we measured rates of escape and mortality ofP. persimiliswhen exposed toO. tristicoloralone or in the presence of western flower thrips,Frankliniella occidentalis(Pergande) (Thysanoptera: Thripidae), and two-spotted spider mites,Tetranychus urticaeKoch (Acarina: Tetranychidae), which acted as alternate prey.O. tristicolorkilledP. persimilisin significant numbers even when thrips were available. The addition of spider mites and thrips to the two predator system significantly reducedO. tristicolorpredation on P. persimilis and thrips. Spider mites were shown to reduceO. tristicolorpredation both through adult mites substituting as acceptable prey and through the mite's webbing acting to lower overall preying activity ofO. tristicolor. When spider mites were available, a negative correlation was observed between thrips killed andP. persimilissurviving, indicating no clear preference ofO. tristicolorfor attacking thrips rather thanP. persimilis. We discuss the significance of the generalized character ofO. tristicolorattack behavior with respect to its use as a thrips predator in the greenhouse, and the potential significance of our laboratory observations for situations requiring biological control of multiple pests.

DOI:10.1093/ee/22.2.477

出版商:Oxford University Press    

年代:1993

数据来源: OUP