摘要:

Damage to fruit of eight accessions and cultivated varieties of tomato by natural infestations of beet armyworm,Spodoptera exigua(Hübner), in Southern California ranged from 0.1 to 10%. This field damage was significantly correlated with 9-d weight and survival ofS. exigualarvae reared to pupation from third instar in the laboratory on fruit of these tomato test entries. Two accessions ofLycopersicon esculentumvarietycerasiformeand one small-fruited cultivated variety ofL. esculentumsustained lowest damage in the field (1–50% of susceptible controls).S. exigualarvae had reduced survival and reduced 9-d weight (≈20% of susceptible controls). Time to pupation was also increased on these three lines (30% greater than controls). The resistant fruits had high concentrations of total glycoalkaloids in the fruit tissue (5.4 to 25.4 mg/g dry weight versus 1.8 mg/g in a susceptible fruit) and this may have been the basis of the antibiosis. Phytosterol concentrations in the fruits were not sufficiently high to potentially alleviate glycoalkaloid toxicity. In binary choice tests between fruit and foliage of the most resistant line,L. esculentumvarietycerasiformeLA 1320, larvae ofS. exiguafed on fruit 70% less than larvae in choice tests between the fruit and foliage of susceptible ‘VFN 7718’. Larval nonpreference for fruit apparently contributes to resistance in LA 1320. The resistance toS. exigua, of LA 1320 predicted by this mechanism, is close to observed levels of resistance in the field.

DOI:10.1093/ee/23.4.937

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Controlled infestation with eggs of western corn rootworms,Diabrotica virgifera virgiferaLeConte, was used in a 2-yr study on the effects of wheel traffic-induced soil compaction on corn rootworm establishment, survival, and larval injury to the roots of maize,Zea maysL. Root injury ratings and cumulative emergence of adults of western corn rootworms, as taken from emergence cages, were lowest in plots where eggs had been infested into compacted interrows. Measurements of soil bulk density, air-filled porosity, and air permeability were taken on core samples to characterize soil physical properties in relation to soil compaction. Lowest rootworm survival and injury coincided with higher bulk density, lower air-filled porosity, and lower air permeability values characteristic of soil from the compacted interrow plots. Survival and establishment of western corn rootworm larvae were associated with greater soil pore continuity in uncompacted plots. Soil compaction induced by controlled wheel traffic may have potential as a management strategy for reducing larval corn rootworm movement into strip intercropped maize adjacent to areas previously planted to maize and rotated into a crop that is not a host for corn rootworms.

DOI:10.1093/ee/23.4.943

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Infestations of the sweetpotato whitefly,Bemisia tabaci(Gennadius), in fields of spring-grown cantaloupes,Cucumis meloL., near Yuma, AZ, were measured by counts of eggs, first to mid-fourth instars, late-fourth instars (red-eyed nymphs) and adults. All stages were sampled from leaves at the terminal and crown portions of the plant. Adults were sampled at 0700 and 1300 hours on the entire leaf, and immature stages were counted in a 1-cm2area from each of four quadrants of a leaf. Adult whiteflies were more abundant on samples collected at 0700 hours and on terminal leaves in all fields. There were no significant differences between leaf sections for any immature life stage, but red-eyed nymphs were more abundant on crown leaves, whereas eggs had higher densities on terminal leaves. The power law and patchiness regressions indicated that all life stages were aggregated, but there were distinct degrees of aggregation between leaf positions.

DOI:10.1093/ee/23.4.949

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Taking into account the limits of previous models proposed to predict European corn borer,Ostrinia nubilalis(Hübner) infestation time, complementary research in physiology, population dynamic, and modeling was used to propose a mechanistic model to describe this phenomenon. Diapause is the main process that determines infestation time in this pest. Recent work on diapause has demonstrated the heterogeneity of this development phase. This model describes the first phase of the diapause process, wing disk development. The model proposed consists of two parts; the first component takes into account the influence of temperature as a nonlinear function and the second (normal distributions) represents the variability in development time among a population for each stage. This model has been estimated by maximum likelihood from laboratory data obtained with a destructive sampling under three variable sinusoidal temperature regimes 9–21, 12–34, and 18–42°C with a photoperiod of 12:12 (L:D) hallowing diapause induction. This unique model describes the development under these different temperature ranges with a 2% precision (0.5 d) and has been validated under field conditions. The development of populations ending their development before winter is correctly represented (10% precision). The model is not adapted to describe the population ending their development after winter. The estimated model correctly predicts diapause development for temperatures above 4°C. This report presents novel data in modeling research and demontrates a convincing correlation between laboratory and field collected data.

DOI:10.1093/ee/23.4.955

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The effects of greenbug,Schizaphis graminum(Rondani), feeding on the nonstructural carbohydrate concentrations of field-grown seedling and vegetative sorghum plants,Sorghum bicolorMoench, were measured by high-performance liquid chromatography. Four individual experiments were completed for each of the plant growth stages to compare nonstructural carbohydrate concentrations between greenbug-infested and uninfested plants. Greenbug-infested seedling plants tended to have greater concentrations of nonstructural carbohydrates in the shoots and lower concentrations in the roots when compared with uninfested plants. The concentration of sucrose in the shoots of seedling plants increased and starch in the roots decreased in a linear relationship with increasing greenbug density. In contrast to seedling plants, roots of greenbug-infested vegetative plants had a greater concentration of total nonstructural carbohydrates and shoots had a reduced concentration. The starch concentration in the shoots of infested vegetative plants decreased with increasing greenbug density. These results demonstrate that sorghum plants at these two growth stages respond differently to greenbug feeding in their ability to maintain nonstructural carbohydrate concentrations.

DOI:10.1093/ee/23.4.965

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The effects of seven constant temperatures (ranging from 19 to 36°C) on development, longevity, and fecundity of the oriental fruit fly,Bactrocera dorsalis(Hendel), were investigated in the laboratory. Development of preadults ranged from 30.4 d at 19°C to 17.4 d at 36°C. Egg to adult survival ranged from a high of 50% at 25°C to a low of 28%at 36°C. Adult life spans averaged 155 d at 19°C to 30 d at 36°C. The expectation of life at age 0 of adult females and males did not differ significantly. Females laid the most eggs (1,581 eggs) at 22°C and the fewest (nine eggs) at 36°C. Intrinsic rate of increase ranged from 0.095 at 34°C to 0.005 (individual per female per day) at 36°C. The population had the ability to double with the shortest time at 34°C (7.3 d) to the longest time at 36°C (130.7 d). These data can be used to maximize the production ofB. dorsalisfrom mass-rearing facilities and to develop computer simulation models to predictB. dorsalisdevelopment and population dynamics for sterile insect release and male annihilation programs.

DOI:10.1093/ee/23.4.971

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Periplaneta fuliginosa(Serville) were collected from Clemson, SC, in the Piedmont region, and Charleston, SC, in the coastal region. Maximal developmental rates of eggs and number of nymphs emerging from oothecae hatching at five temperature increments (15, 20, 25, 30, and 35°C) were recorded in the laboratory for each population. Developmental rates were also recorded for the first male and female to mature from 1-d-old nymphs hatched from the same ootheca. For first females, preoviposition (time to first ootheca) and oviposition rates, egg developmental rate, and number of nymphs emerged were recorded. Between 20 and 30°C, coastal nymphs developed 5% faster than Piedmont nymphs. At 15°C, only eight cockroaches reached adulthood after 56 mo. Oviposition and preoviposition rates of the coastal population were about 25% faster. Biologically these differences appear insignificant because they are less than variation in literature values. From data pooled from this experiment and the literature, coefficients of the Sharpe-DeMichele developmental rate model were calculated for egg and nymphal development, preoviposition, and oviposition. The regressions had highr2values and provide a quantitative basis for understanding population processes in this insect.

DOI:10.1093/ee/23.4.979

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Seeds of cowpea,Vigna unguiculata(L.) Walp, line ‘TVu 2027’ are moderately resistant to the cowpea weevil,Callosobruchus maculatus(F.).C. maculatuslarvae exhibit higher mortality and take longer to develop in ‘TVu 2027’ than in more susceptible seeds. Claims have been made (Gatehouse, A.M.R., J. A. Gatehouse, P. Dobie, A. M. Kilminster&D. Boulter. 1979. Biochemical basis of insect resistance inVigna unguiculata.J. Sci. Food Agric. 30: 948–958) that an elevated level of cowpea trypsin inhibitor (CPTI) confers resistance to ‘TVu 2027’. To test this hypothesis, we isolated and purified CPTI and evaluated its impact on cowpea weevil using an artificial seed system. CPTI at dietary levels up to 2.0% (wt/wt) caused no significant increase in mortality of cowpea weevils and only slight delays in within-seed developmental times. These results do not support the hypothesis that CPTI is the basis of resistance in ‘TVu 2027’.

DOI:10.1093/ee/23.4.987

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Gaseous emissions were analyzed by gas chromatography to determine whether increased volatile hydrocarbon production from wheat,Triticum aestivumL., seedlings infested with greenbugs,Schizaphis graminum(Rondani), was associated with virulence. Ethylene production from wheat seedlings was stimulated by greenbug infestation. Ethylene production was greater from virulent combinations of wheat genotypes and green bug biotypes, compared with avirulent combinations, in most cases. A 6-h interaction period was sufficient to trigger increased ethylene production with evolution rates decreasing sharply by 1 d after removal of greenbugs. No other stress volatiles were detected from infested seedlings, although membrane damage (based on electrolyte leakage), chlorosis, and necrotic spots were evident after 4 d in a susceptible genotype. Wheat seedlings were capable of producing increased levels of volatile hydrocarbons in response to stress because exposure to 55 or −70°C produced more acetaldehyde, ethane, ethanol, methanol, and pentane than controls.

DOI:10.1093/ee/23.4.992

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Beet armyworm,Spodoptera exigua(Hübner), larvae were placed on sugarbeet (Beta vulgarisL.) and pigweed (Amaranthus hybridusL.) plants in outdoor chambers in which the plants were growing at either the ambient (≈350μl liter−1) or ambient plus 350μl liter−1(≈700μl liter−1) carbon dioxide concentration. A series of experiments was performed to determine if larvae reduced plant growth differently at the two carbon dioxide concentrations in either species and if the insect growth or survival differed with carbon dioxide concentration. Leaf nitrogen, water, starch, and soluble carbohydrate contents were measured to assess carbon dioxide concentration effects on leaf quality. Insect feeding significantly reduced plant growth in sugarbeet plants at 350μl liter−1but not at 700μl liter−1nor in pigweed at either carbon dioxide concentration. Larval survival was greater on sugarbeet plants at the elevated carbon dioxide concentration. Increased survival occurred only if the insects were at the elevated carbon dioxide concentration and consumed leaf material grown at the elevated concentration. Leaf quality was only marginally affected by growth at elevated carbon dioxide concentration in these experiments. The results indicate that in designing experiments to predict effects of elevated atmospheric carbon dioxide concentrations on plant–insect interactions, both plants and insects should be exposed to the experimental carbon dioxide concentrations, as well as to as realistic environmental conditions as possible.

DOI:10.1093/ee/23.4.999

出版商:Oxford University Press    

年代:1994

数据来源: OUP