摘要:

Attraction of maleMicroplitis croceipes(Cresson) to virgin females was demonstrated for the first time in the field. The males were most active during morning hours beginning as early as 0630, with peak numbers occurring between 0800 and 1100. No males were caught in traps baited with virgin females after 1200. Female flight activity also was greater in the morning than in the evening, but females remained active throughout the day. Flight activity of females began about 1 h later than males. No significant (P<0.05) difference in parasitism byM. croceipeswas detected for host larvae (Heliothisspp.) that were collected from different areas of the cotton plant, or that were feeding on squares, versus flowers versus bolls. Parasitized larvae were collected from all sizes of cotton bolls (up to 40 mm in diameter), but no large (25− to 40−mm) larvae that were collected from the field were parasitized byM. croceipes.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.272

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

On insecticide-free pear trees in an orchard in central Pennsylvania, there was a low correlation between milligram fructose equivalents of foliar honeydew and numbers of pear psylla,Psylla pyricolaFoerster, nymphs per leaf, with the exception of 2 weeks in mid-July when little rainfall occurred (0.13 cm/week). The percentage of sooty-mold-damaged pears was significantly correlated with the seasonal average of nymphs per leaf but not with the seasonal average of foliar honeydew levels. In addition, the seasonal history of pear psylla was monitored on the same trees and early-season pear psylla development was related to pear tree phenology. There were three generations of pear psylla, the second being the largest and most important in regard to fruit development and damage.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.278

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

We examinedTetranychus urticae(Koch) fecundity and development on three peppermint,Mentha piperitaL., leaf age classes which differed significantly (P<0.05) in total phenolic and monoterpene content. Young, expanding lateral leaves had the highest monoterpene and phenolic content. Mature top mainstem leaves had the lowest phenolic content, and old bottom mainstem leaves had the lowest monoterpene content. As leaf phenolic content increased, the number of eggs laid per leaf significantly decreased (P<0.001), and dispersal of immature mites, measured as percent caught in sticky Tack- Trap cages, significantly increased (P<0.001). Development times of immatures on young lateral leaves were significantly longer (P<0.05) than on the more mature mainstem leaves. Increased activity ofT. urticaemay have resulted in reduced feeding rates, which may in turn have accounted for the lower number of eggs laid and the increased development time of immatures on peppermint leaves with high phenolic content. The monoterpene content of leaves was not significantly correlated with spider mite biology, perhaps because monoterpenes are sequestered in plant cells not fed on by spider mites. However, vapors from 5% solutions of menthol and pulegone significantly reduced oviposition and increased mortality of female mites confined in unventilated petri dishes (P<0.05).

ISSN:1754-5692    

DOI:10.1093/ee/13.1.282

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Plum curculio females,Conotrachelus nenuphar(Herbst) (Coleoptera: Curculionidae), were found to oviposit, before fruit set, on mature ‘Granny Smith’ apples attached to major branch junctions in the upper half of standard ‘McIntosh” apple trees. Observations for three growing seasons (1978, 1979, and 1980) within an insecticide-free orchard in southwestern Quebec are presented. Rank correlations between oviposition on these scout-apples and both “June” drop and harvest damage were found. Incidence of scarring was highest (17 to 25% of scout-apples had oviposition scars) in orchard sectors adjacent to a woodlot and lowest (7%) in the central sector of the 1.7-ha experimental orchard. This monitoring technique may be used in apple orchards to indicate when and where to concentrate control efforts.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.286

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Commercial fresh-market tomato fields in southeast Arkansas were monitored forHeliothisspp. during 1981 and 1982. Caterpillar-caused fruit damage, most of which was due toHeliothis,was surveyed during regular plant examinations both years and during harvest in 1982. Oviposition byHeliothis zeain nearby corn plots was also measured during 1982. AlthoughH. virescenswas present in the tomato crop system,H. zeawas the predominant species. In 1981, highestHeliothisegg counts on tomato were found on 5 and 29 May. In 1982,Heliothisegg densities on tomato were very low until 30 June. Although fruit damage was greater in insecticide-free sections of fields during 1982, overall damage was considered to be quite low (ca. 1–2%) in all plots. The proximity of silking-stage corn appeared to be an important factor inH. zeaseasonal population patterns in the tomato system.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.292

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Size variation of the bean leaf beetle (BLB),Cerotoma trifurcata(Forster), was evaluated, using adults from soybean fields in the Piedmont and Coastal Plain regions of North Carolina. BLBs sampled from the Coastal Plain counties, Currituck and Tyrrell, were largest. Within fields, late-season beetles were larger than beetles from earlier generations. Female BLBs were consistently larger than males in all samples. Multiple-regression techniques indicated that a small but significant amount of beetle size variation could be explained by eight field-related variables: field size, planting date, rainfall, row width, and percent sand, silt, clay, and organic matter in the soil. The magnitude of variation explained and relative importance of the variables differed between the sexes. Eight variables explained only 27 and 45% of variance in female and male size, respectively. The effects of soil moisture, texture, and temperature on adult size (weight) were determined under controlled conditions. In comparisons made among loamy sand, sandy clay loam, and organic soils, adult size was greatest in wet, organic soil and least in dry, loamy sand.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.300

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Arthropods were monitored in soybean,Glycine maxL. Merrill, of early-, medium-, and late-maturity groups planted from April through July in several row spacings at four locations in Mississippi for 1 to 3 years. There were four major predator groups at each location: geocorids [mostlyGeocoris punctipes(Say)], nabids (Nabisspp.), lady beetles (Coccinellidae), and spiders. Geocorid, nabid, and spider populations gradually increased during the summer, but lady beetle populations peaked in midseason. Predator populations were not strongly affected by the three cultural practices: Geocorid, nabid, and spider populations (but not lady beetles) were higher in late-planted than in early-planted soybean; nabid populations (but not geocorids, lady beetles, and spiders) were higher in late-maturing than in early-maturing cultivars; and geocorid and spider populations (but not nabids and lady beetles) were higher in narrow- than in wide-row soybean. Predator population responses to cultural practices were generally similar to responses observed among the defoliating caterpillars. The effects of soybean cultural practices on phytophagous beetles and stink bugs are also discussed.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.305

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

Numerous sweet corn genotypes and cultivars were evaluated for field resistance to aphid-borne maize dwarf mosaic virus infection. The entries displayed wide ranges in symptomatology and yield reactions to severe MDMV infection pressure. Plant barrenness contributed greatly to yield reductions in all trials. The percent infected plants at 45 days postplant was not significantly correlated with yield in two of the three trials. It was shown that poor yield performance of a genotype for the fresh market may not eliminate it as a useful processing sweet corn. The data show evident progress in the development of MDMV resistance in sweet corn, but high ear quality is lacking.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.318

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

The probability of detecting low overwintered populations of boll weevils,Arithonomus grandis grandisBoheman, with infield or border traps at the rate of 2.46/ha was determined. Even though all fields were infested with F1weevils, the parent population was not detected in 20% of the border-trapped fields; however, it was detected in all of the infield-trapped fields. The capture in traps away from overwintering habitat was greater than or equal to the capture in traps adjacent to overwintering habitat. The male boll weevils responded to the traps at a younger average age than the females.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.324

出版商:Oxford University Press    

年代:1984

数据来源: OUP

摘要:

The direct relationship between cigarette smoking and lung cancer is well known. However, this does not mean that all smokers will necessarily develop lung cancer or that nonsmokers will never contact lung cancer. The same kind of reasoning should be applied to the question of competitive exclusion of introduced natural enemies in biological control. In a previous paper, we established an inverse relationship between (1) the rate of (or percent) establishment of a large group of introduced predators and parasites and (2) the number of exotic incumbent species of natural enemies present and the number released simultaneously (see Ehler and Hall [1982] for details). We noted that the empirical evidence was consistent with the competitive-exclusion hypothesis and that therefore the hypothesis should not be rejected. We did not claim that competitive exclusion has occurred frequently or that our results were conclusive, as some have suggested, and we most certainly did not conclude that all (or most) establishment failures involving multiple-species introductions were due to competitive exclusion. Because too many people have read their own erroneous conclusions into our paper, we feel compelled to set the record straight.

ISSN:1754-5692    

DOI:10.1093/ee/13.1.v

出版商:Oxford University Press    

年代:1984

数据来源: OUP