摘要:

Greenhouse studies were conducted to determine the effects of four soil textures and four soil drying periods on southern corn rootworm,Diabrotica undecimpunctata howardiBarber, egg and larval survival and maturation. Soil drying intervals had the most detrimental effect on survival. After 4 d of soil drying (no water added to pots), only 20% of larvae survived to pupation. Low clay or organic matter and low levels of soil moisture were not conducive to survival of southern corn rootworm. The interaction of soil texture and soil drying indicates that at 4 d of soil drying, larval survival decreased (70%) in all soils, except dark-textured soils (35% decrease) compared with 2 d of soil drying. Low levels of soil moisture slowed developmental time of larvae. Eggs and first instars were the stages most negatively affected by moisture stress and different soil textures. However, in quartz-sand, the more mobile stages had low survival, probably because of cuticle abrasion from soil particles. The results of these experiments demonstrate the importance of considering the effects of rapidly drying soil on survival of southern corn rootworm and not simply the percentage of soil moisture at any one time.

DOI:10.1093/ee/19.3.697

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A Y-tube behavioral bioassay was developed to investigate attraction of the diamondback moth,Plutella xylostella(L.), to volatiles from host plants. During the scotophase, male and female moths were attracted to volatiles of homogenized leaves of Oriental mustard,Brassica juncea(L.) Cosson, plants at the flower bud stage, and to the odor of Oriental mustard seedlings. The response of both sexes increased with age from 1 to 7 d. Females were more strongly attracted when they were allowed prior access to both mates and plants, but the effect of these factors on males was ambiguous. Neither sex responded to volatiles during the latter half of the photophase. Females that responded to volatiles in a standard bioassay subsequently laid more eggs than did nonresponders and yet still contained similar numbers of mature eggs in their ovaries. This implies that egg load is related to responsiveness to plant volatiles. The patterns of response are interpreted in relation to reproduction in this species.

DOI:10.1093/ee/19.3.704

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

This study compared oviposition byHeliothis armigera(Hübner) andH. punctigera(Wallengren) on four cotton cultivars: a smooth-leaf cultivar (‘Deltapine Smooth Leaf’) and a genetically similar hirsute cultivar (‘Deltapine 16’), an okra leaf cultivar (‘Coker 201 Okra Leaf’) and a near-isogenic normal-leaf cultivar (‘Coker 201 Normal Leaf’). In the glasshouse, ‘Deltapine Smooth Leaf’ plants received the lowest number of eggs and ‘Coker 201 Normal Leaf’ the highest. In the field, ‘Deltapine Smooth Leaf’ had the fewest eggs and ‘Coker 201 Okra Leaf’ the most. BothHeliothisspecies exhibited similar oviposition on different structures on each cultivar for each plant growth stage. Most eggs were laid on mature leaves. In the glasshouse, the lower leaf surface received more eggs than the upper; the upper surface received more eggs in the field. Terminal buds received the fewest eggs in the glasshouse, but in the field, egg numbers on terminal buds, bracts, stems, petioles, and stipules were similar. Analysis of the relative effect of the okra leaf and smooth-leaf traits on oviposition indicates higher oviposition on the okra leaf than on the smooth-leaf plants, although trichome density might in part be responsible for some of the differences.

DOI:10.1093/ee/19.3.710

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The influence of sprinkler irrigation on dispersal of nuclear polyhedrosis virus (NPV) in remains of NPV-killed lepidopterous larvae on soybean was examined.Anticarsia gemmatalisHübner andPseudoplusia includens(Walker) larvae in late stages of infection with their respective NPV isolates were placed on separate rows in the upper canopy of caged soybean plants. After death of the infected larvae, the cages were removed, and the plants were immediately irrigated by sprinkler. Leaflets were collected and bioassayed for NPV with second instars of the respective host. Dispersal of NPVs from cadaver remnants on the plants occurred without irrigation but was significantly increased by 0.25 cm water from sprinkler irrigation. The majority of each NPV was moved into the lower canopy (P<0.05). Additional irrigation totaling 1.25 or 6.25 cm did not significantly increase dispersal of theP. includensNPV but did increaseA. gemmatalisNPV in the lower canopy. Virus dispersal was less affected when irrigation was delayed until 7 d after larval death. However, the highest volume (6.25 cm) resulted in significantly higher larval mortality in the irrigated plots (P<0.05).

DOI:10.1093/ee/19.3.717

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Soil-dwelling larvae of the cranberry girdler,Chrysoteuchia topiaria(Zeller), are difficult to detect even at densities causing severe damage to plantings of commercial cranberry (Vaccinium macrocarponAit.). This study examined plant preference of this insect as a potential monitoring tool in cranberry bogs. Girdler larvae preferred grasses to Douglas fir seedlings and to cranberry plants. Among the seven grass species evaluated, foxtail (Alopecurus pratensisL.) and red top (Agrostis albaL.) were most heavily infested. Preference in these experiments is expressed as movement of larvae to these plants rather than as oviposition preference by adult females. Foxtail is suggested as a useful monitoring tool in cranberry bogs because detecting girdler larvae on this plant is easy even at very low levels of girdler infestation on cranberry plants. It is suggested that this method of attracting and monitoring also be incorporated in the protocol of experimental studies of control measures for this insect, or as a potential trap crop.

DOI:10.1093/ee/19.3.721

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A simulation model for the population dynamics ofRhyzopertha dominica(F.) was used to compare the effectiveness of various stored-wheat management programs in controlling this insect in the United States. Infestations on day 365 were reduced 88 times when wheat was harvested and stored in August instead of June, 34 times by aerating the grain in September instead of November, 20 times by storing grain at 10% instead of 14% moisture content, 18 times by fumigating in August or September instead of July, four times when wheat was stored at 27°C instead of 32°C, and approximately three times when malathion was used as a protectant. The model simulations provide an overview of the relative advantages of various approaches to managing stored-grain insects in various geographic localities.

DOI:10.1093/ee/19.3.725

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The glossy cauliflower PI234599 has been shown by other authors to have resistance to three species of Lepidoptera, but the relationship between insect resistance and the glossiness of the leaf surface has been unclear. To examine this relationship in a broader range ofBrassica oleraceaL., five species of insect pests were counted under natural infestation on eight glossy genetic lines of broccoli, cauliflower, Brussels sprouts, collards, and kale; six lines reported to have reduced leaf wax; and ten varieties of the same crops with normal leaf wax. Glossy lines consistently had fewer imported cabbageworm,Artogeia rapae(L.), larvae and eggs and fewer cabbage aphids,Brevicoryne brassicae(L.), than other lines. Four of the glossy lines had low numbers of diamondback moth larvae,Plutella xylostella(L.), in all three plantings, but the other four performed differently in separate plantings. Surprisingly, a glossy kale with allelic genes for glossiness to PI234599 had poor resistance to diamondback moth. Glossy lines had the mostPhyllotreta cruciferae(Goeze) in one spring planting, but there were no significant differences in the numbers of this species of flea beetle on various lines in the fall planting at the same location. This study identifies additional promising sources of insect resistance among glossy lines ofB. oleracea, but further study is needed of the variability in resistance to diamondback moths and flea beetles over repeated plantings and among different glossy lines.

DOI:10.1093/ee/19.3.730

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The microhabitat distribution of velvetbean caterpillar,Anticarsia gemmatalisHübner, pupae was studied in soybean field cages and fields during 1985, 1986, and 1987. Larval density did not affect pupal horizontal distribution patterns related to direction and distance from the plant row. Pupae were found equally on both sides of soybean plant rows in a cage study. Pupae were found on and below the soil surface but not on the plant. The majority (84.5%) of pupae were found<2 cm under the soil surface. Soybean with conventional (91 cm) and narrow (51 cm) row spacings had different pupal horizontal distribution patterns. In narrow row spacing, equal numbers and similar dispersion patterns of pupae were found on either side of the plant row. In conventional row spacing, pupal densities varied inversely with distance from the row. Also, pupal densities were slightly biased to the north side (4:6) of the plant rows in 1986, and this trend was extreme (2:8) in 1987 when plant canopy was barely closed. Implications for pupal sampling are discussed.

DOI:10.1093/ee/19.3.740

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Parasitoids and pathogens of soybean looper,Pseudoplusia includens(Walker), and velvetbean caterpillar,Anticarsia gemmatalisHübner, were studied on soybean at three locations in Louisiana during the summers of 1984 and 1985. Nine species of primary parasitoids and one hyperparasitoid were collected from soybean looper larvae and pupae.Meteorus autographaeAshmead was the predominant parasitoid (13.5%) collected during 1984, andCopidosoma truncatellum(Dalman) was predominant (15.9%) in 1985. Total parasitism during 1984 was 34.1%, while parasitism in 1985 was 27.5%. Three entomopathogens,Nomurea rileyi(Farlow) Samson,Entomophthora gammae(Weiser), and a nuclear polyhedrosis virus were collected from soybean looper. Parasitism of velvetbean caterpillar was only 4.5 and 0.7% in 1984 and 1985, respectively, with the most common parasitoid both years beingM. autographae.N. rileyicaused mortality of 10.9 and 14.7% during 1984 and 1985, respectively.

DOI:10.1093/ee/19.3.746

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Egg parasitism ofHeliothis zea(Boddie) and other lepidopterous pests was monitored in a field trial of processing tomato cultivars in 1981 and in several late-season commercial fields of processing tomatoes in the Sacramento Valley of California in 1983, 1985, and 1986. Four species ofTrichogrammawere present:T. pretiosumRiley,T. thalense(Pinto&Oatman),T. deionPinto&Oatman, andT. brevicapillumPinto&Platner. Actual parasitism ofH. zeaeggs exceeded 83% in all fields monitored in 1985 and exceeded 62% in most fields monitored in 1986.Manducaspp. andTrichoplusia ni(Hübner) eggs were also commonly parasitized byTrichogrammaspp. The high levels ofH. zeaegg parasitism recorded in these commercial fields indicates that the current economic threshold, which is based on the abundance of whiteH. zeaeggs, can be increased to account for the mortality caused byTrichogramma. Procedures to incorporateH. zeaegg parasitism into the current integrated pest management program for processing tomatoes are proposed. Acceptable fruit quality at harvest in fields that exceeded the current economic threshold during the growing season provides additional support for increasing the threshold. The effect of insecticide applications onH. zeaegg parasitism is discussed.

DOI:10.1093/ee/19.3.753

出版商:Oxford University Press    

年代:1990

数据来源: OUP