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PubMed2003

Overwintering of Heliothis virescens (F.) and Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in cotton fields of northeast Mississippi.

Following the 1995-2001 crop seasons, population densities of pupae of tobacco budworm, Heliothis virescens (F.), and corn earworm, Helicoverpa zea (Boddie), overwintering in cotton fields, Gossypium hirsutum L., in Monroe County, MS, were estimated by digging a total of 43,542 m-row. Densities of pupae varied greatly among years with the highest densities occurring in years with low rainfall in the late summer and early fall. The sex ratio of pupae was variable and significantly male-biased in some years. The total area-wide, tobacco budworm population emerging from all overwintering sites was estimated from catches in pheromone traps whose absolute efficiency is known. After the introduction of Bacillus thuringiensis Berliner (Bt)-transgenic cotton in 1996 but before a several-fold increase in use of herbicide resistant (HR)-transgenic cotton cultivars in 2001, local cotton fields accounted for <2% of the total overwintered tobacco budworm population. In the pretransgenic cotton production era, it is estimated cotton fields typically accounted for <10% of the overwintered tobacco budworm population. Driving surveys of the tillage status of cotton fields and pheromone trapping to determine the timing of adult emergence in the spring indicate that--until the 2000 crop season--postseason tillage destroyed most tobacco budworm and corn earworm pupae overwintering in cotton fields. Adoption of HR-transgenic cultivars has quintupled cotton field area planted no-till, but the contribution of cotton fields to overwintered tobacco budworm populations has remained low. Preemptive tillage of cotton fields to kill overwintering tobacco budworm pupae would not appreciably suppress in-season population densities of this pest. However, the absence of such tillage might increase the rate at which the tobacco budworm develops resistance to insecticides and counteradaptation to antibiotic host plant resistance traits including the Bt-transgenic trait.

Animals↗
PubMed2003

Physiological and antioxidant responses of cotton and spurred anoda under interference and mild drought.

The influence of plant interference and a mild drought on gas exchange and oxidative stress was investigated using potted plants of two cotton species (Gossypium hirsutum L. cv. Delta Pine 5415, and Gossypium barbadense L. cv. Pima S-7) and spurred anoda (Anoda cristata L. Schlecht.) of the Malvaceae. Without interference, cotton and spurred anoda had similar net photosynthesis (Pnet) but different pigment profiles. Stomatal conductance (gs) and transpiration rate (E) were greater in spurred anoda than cotton. Net photosynthesis and biomass in cotton were reduced more by spurred anoda interference than by intraspecific interference. With interference, the xanthophyll cycle conversion state and alpha-tocopherol levels increased in cotton, but remained unchanged in spurred anoda. Catalase, ascorbate peroxidase (APX) and glutathione reductase (GR) activities were not influenced by plant interference. Without interference, spurred anoda had lower APX, and similar catalase and GR activities compared with cotton. Mild drought increased APX activity more than 40% in cotton, and 26% in spurred anoda. Upon drought recovery, drought-induced APX activity was still higher in cotton, and GR activity was higher in previously drought-stressed cotton and spurred anoda plants compared with well-watered plants. The greater impact of spurred anoda interference than intraspecific interference on cotton biomass is due mainly to reduced carbon gain in cotton.

Antioxidants↗
PubMed2001

Effects of Bt cotton and crylac toxin on survival and development of pink bollworm (Lepidoptera: Gelechiidae).

We evaluated the effects of Bacillus thuringiensis (Bt) toxin CrylAc on survival and development of a susceptible strain and laboratory-selected resistant strains of pink bollworm, Pectinophora gossypiella (Saunders). For susceptible and resistant strains tested on artificial diet, increases in CrylAc concentration reduced developmental rate and pupal weight. In greenhouse tests, survival of resistant larvae on transgenic cotton that produces CrylAc (Bt cotton) was 46% relative to their survival on non-Bt cotton. In contrast, Bt cotton killed all susceptible larvae tested. F1 hybrid progeny of resistant and susceptible adults did not survive on Bt cotton, which indicates recessive inheritance of resistance. Compared with resistant or susceptible larvae reared on non-Bt cotton, resistant larvae reared on Bt cotton had lower survival and slower development, and achieved lower pupal weight and fecundity. Recessive resistance to Bt cotton is consistent with one of the basic assumptions of the refuge strategy for delaying resistance to Bt cotton. Whereas slower development of resistant insects on Bt cotton could increase the probability of mating between resistant adults and accelerate resistance, negative effects of Bt cotton on the survival and development of resistant larvae could delay evolution of resistance.

Animals↗
PubMed2002

Oviposition on and mining in bolls of Bt and non-Bt cotton by resistant and susceptible pink bollworm (Lepidoptera: Gelechiidae).

Transgenic cotton that produces insecticidal crystal protein Cry1Ac of Bacillus thuringiensis (Bt) has been effective in controlling pink bollworm, Pectinophora gossypiella (Saunders). We compared responses to bolls of Bt cotton and non-Bt cotton by adult females and neonates from susceptible and Cry1Ac-resistant strains of pink bollworm. In choice tests on caged cotton plants in the greenhouse, neither susceptible nor resistant females laid fewer eggs on Bt cotton bolls than on non-Bt cotton bolls, indicating that the Bt toxin did not deter oviposition. Multiple regression revealed that the number of eggs laid per boll was negatively associated with boll age and positively associated with boll diameter. Females also laid more eggs per boll on plants with more bolls. The distribution of eggs among bolls of Bt cotton and non-Bt cotton was clumped, indicating that boll quality rather than avoidance of previously laid eggs was a primary factor in oviposition preference. Parallel to the results from oviposition experiments, in laboratory no-choice tests with 10 neonates per boll, the number of entrance holes per boll did not differ between Bt cotton and non-Bt cotton for susceptible and resistant neonates. Also, like females, neonates preferred younger bolls and larger bolls. Thus, acceptance of bolls by females for oviposition and by neonates for mining was affected by boll age and diameter, but not by Bt toxin in bolls. The lack of discrimination between Bt and non-Bt cotton bolls by pink bollworm from susceptible and resistant strains indicates that oviposition and mining initiation are independent of susceptibility to Cry1Ac.

Animals↗
PubMed2002

Evaluation of the natural refuge function for Helicoverpa arnigera (Lepidoptera: Noctuidae) within Bacillus thuringiensis transgenic cotton growing areas in north China.

The density of Helicoverpa armigera (Hübner) populations on Bacillus thuringiensis Berliner (Bt) transgenic cotton, corn, peanut, and soybean; differences in its development on Bt cotton and common (nontransgenic) cotton; and the potential for mating among populations from Bt cotton fields and other crop fields were investigated in the suburbs of Xinxiang City (Henan Province) and Langfang City (Hebei Province) in the southern and northern parts of north China, respectively. Although development of H. armigera on Bt cotton was much slower than on common cotton, there was a still high probability of mating between populations from Bt cotton and other sources due to the scattered emergence pattern of H. armigera adults, and overlap of the second and third generations. In a cotton and corn growing region, early and late planted corn provided suitable refugia for the third and fourth generations of H. armigera, but not for the second generation. In a cotton and soybean/ peanut mix system, noncotton crops provided a natural refugia from the second- to fourth-generation H. armigera, but function of the refuge would closely depend on the proportion of Bt cotton. Consequently, it may be necessary to compensate the original mixed cropping patterns in different areas for delaying resistance development of H. armigera to Bt cotton.

Animals↗
PubMed2001

First steps to improve cotton crop management in Thailand.

Thai cotton growers yearly face serious pest problems consisting of heavy infestation associated with resistance to pesticides leading to expensive and harmful pest control practices. Thanks to a multi discipline research work carried out from 1991 to 1996, a decision-oriented model for cotton crop management was developed and compared to farmers' practices during the 1988 cotton growing season 1998 in Klang Hat district, Thailand. This model, based on plant monitoring, involved a new cotton cultivar (DORA 11 as a replacement for Sri Samrong 60), seed treatment with imidacloprid (at 3.5 g of a.i./kg of seeds), a threshold-based spray of mepiquat chloride, a cotton growth regulator (Pix at 1.5 l/ha) and a set of rules to selectively control with chemical and biological insecticides the major pests the American bollworm (Helicoverpa armigera Hübner) and the cotton leafhopper (Amrasca biguttula biguttula Ishida). This package was more friendly towards environment than farmers' practices since seed treatment does not harm beneficials at the beginning of cotton growing season while 1 and 5 sprays were saved against respectively the American bollworm and sucking pests and more than 50% of the sprays directed against American bollworms involved biological insecticides (Bacillus thuringiensis toxins potentialized by a low dosage of endosulfan). Threshold-based sprays against the main pests, the use of a cotton growth regulator, earliness of cotton cultivar and seed treatment were accountable for savings in pesticide sprays. Involving a biological insecticide and endosulfan at the beginning of cotton growing season and using the same quantity of active ingredient at each spray during the cotton growing season also improved the management of pyrethroid resistance in American bollworm populations was also. There was no significant difference between yields inside farmers' fields and innovation plots. However, thanks to cheaper pest control practices economic results were better. Lastly few improvements of this package are proposed.

Agriculture↗
PubMed2005

[Dynamics of soil enzyme activity and nutrient content in intercropped cotton rhizosphere and non-rhizosphere].

The study with high yield cotton-wheat double cropping system showed that soil urease, invertase, protease and catalase activities in intercropped cotton field had the same changing trends with those in mono-cultured cotton field, but were significantly higher in intercropped than in mono-cultured cotton rhizosphere and non-rhizosphere at all development stages of cotton. During the intergrowth period of wheat and cotton, soil nutrient contents in intercropped cotton rhizosphere and non-rhizosphere were lower than or had little difference with those in mono-cultured cotton rhizosphere and non-rhizosphere, but became significantly higher after wheat harvested. The changing trends of soil nutrient contents in intercropped cotton field had little difference from those in mono-cultured cotton field, but the nutrient absorption peak appeared late. The soil enzyme activities and nutrient contents were generally higher in rhizosphere than in non-rhizosphere of both intercropped and mono-cultured cotton. Soil nutrient contents had significant (P < 0.05, n = 32) or very significant (P < 0.01, n = 32) correlation with the activities of soil urease, invertase and protease, but had little correlation with soil catalase activity.

Agriculture↗
PubMed1994

[Intracranial foreign body granuloma caused by fine cotton fibers: a case report].

Reported here is a rare case of intracranial foreign body granuloma caused by fine cotton fibers originating from the cotton sheet, which was used in the previous operation. The patient was a 54-year-old woman who presented with headache and right hemiparesis. CT scan demonstrated a large enhanced tumor in the left temporal lobe. During the operation, the tumor bled easily and was hard to remove. The brain surface was covered with oxidized cellulose (Oxycell) after the tumor was subtotally removed. Cotton sheets (Surgical Patty) were also used during the operation. The microfibrillar collagen hemostat (Avitene) was not applied. The histological diagnosis was astrocytoma. Radio-chemotherapy was given. CT and MRI on the 40th day after the operation, showed a large tumor in the left temporal lobe, which led to suspicions of tumor recurrence. The second operation disclosed a mass which was harder in consistence than the previous one. The histological diagnosis was foreign body granuloma, which contained a lot of fine cotton fibers. Oxycell was not found in it. The cotton-sheet is well documented as a cause of granuloma in the literature, but it is seldom mentioned that the foreign body granuloma is caused by cotton fibers, scattered in the operative fields. This case report suggests the possibility of cotton-fiber granuloma and our simple experiment indicated that a lot of cotton fiber might be scattered in the operative fields, if dry cotton sheets are used. These results stress that washed cotton sheets should be applied to avoid the possibility of the development of cotton-fiber foreign body granuloma.

Adult↗
PubMed1985

Medical and industrial hygiene characterization of the cotton waste utilization industry.

We studied 260 workers in the cotton waste utilization industry and 310 "blue-collar" control workers from nondusty industries in the same geographic area of the United States by respiratory symptom questionnaire and by pre- and postshift spirometry. We excluded 75 cotton workers and 75 control workers from statistical analysis because of prior hazardous occupational exposures. Plant-wide, 8-hour time-weighted average exposures ranged from 0.28 mg/m3 to 7.80 mg/m3. The overall prevalence of symptoms compatible with byssinosis was 5.9% in cotton workers and 4.7% in the controls. Cotton workers with less than 2 years of employment had a significantly greater prevalence of bronchitis than their control counterparts. The cotton workers with 2 years or more of employment had significantly greater prevalences of bronchitis, shift decrement in forced expiratory volume in 1 second (FEV1) of greater than or equal to 10%, and FEV1/FEV1-predicted less than 80%, than their control counterparts. Regression analysis showed that for matched cotton and control workers, the percentage decrement in FEV1 over the shift was significantly greater for cotton workers; and that in all cotton workers, longevity in industry had a negative effect on the before-shift forced vital capacity (FVC). This study suggests that there are both acute and chronic effects of cotton exposure in the cotton waste utilization industry.

Adult↗
PubMedDate not supplied

PAH and soot emissions from burning components of medical waste: examination/surgical gloves and cotton pads.

This is a laboratory investigation on the emissions from batch combustion of representative infectious ("red bag") medical waste components, such as medical examination latex gloves and sterile cotton pads. Plastics and cloth account for the majority of the red bag wastes by mass and, certainly, by volume. An electrically heated, horizontal muffle furnace was used for batch combustion of small quantities of shredded fuels (0.5-1.5 g) at a gas temperature of approximately 1000 degrees C. The residence time of the post-combustion gases in the furnace was approximately 1 s. At the exit of the furnace, the following emissions were measured: CO, CO2, NOx, particulates and polynuclear aromatic compounds (PACs). The first three gaseous emissions were measured with continuous gas analyzers. Soot and PAC emissions were simultaneously measured by passing the furnace effluent through a filter (to collect condensed-phase PACs) and a bed of XAD-4 adsorbent (to capture gaseous-phase PACs). Analysis involved soxhlet extraction, followed by gas chromatography-mass spectrometry (GC-MS). Results were contrasted with previously measured emissions from batch combustion of pulverized coal and tire-derived fuel (TDF) under similar conditions. Results showed that the particulate soot) and cumulative PAC emissions from batch combustion of latex gloves were more than an order of magnitude higher than those from cotton pads. The following values are indicative of the relative trends (but not necessarily absolute values) in emission yields: 26% of the mass of the latex was converted to soot, 11% of which was condensed PAC. Only 2% of the mass of cotton pads was converted to soot, and only 3% of the weight of that soot was condensed PAC. The PAC yields from latex were comparable to those from TDF. The PAC yields from cotton were higher than those from coal. A notable exception to this trend was that the three-ring gas-phase PAC yields from cotton were more significant than those from latex. Emission yields of CO and CO2 from batch combustion of cotton were, respectively, comparable and higher than those from latex, despite the fact that the carbon content of cotton was half that of latex. This is indicative of the more effective combustion of cotton. Nearly all of the mass of carbon of cotton gasified to CO and CO2 while only small fractions of the carbon in latex were converted to CO2 and CO (20% and 10%, respectively). Yields of NOx from batch combustions of latex and cotton accounted for 15% and 12%, respectively, of the mass of fuel nitrogen indicating that more fuel nitrogen was converted to NOx in the former case, possibly due to higher flame temperatures. No SO2 emissions were detected, indicating that during the fuel-rich combustion of latex, its sulfur content was converted to other compounds (such as H2S) or remained in the soot.

Carbon↗
PubMed1999

Improvements in the hygroscopic properties of cotton cellulose by treatment with an endo-type cellulase from Streptomyces sp. KSM-26.

The effect of enzymatic cellulolysis on the moisture-adsorbing properties of cotton cellulose was investigated, using a highly purified endo-type cellulase from Streptomyces sp. KSM-26. The time course of changes in the hygroscopicity of cotton reflected the time course of changes in the extent of the amorphous state of cotton, which was estimated from the amount of water that could bind to cotton, as determined by differential scanning calorimetry, during the hydrolytic process. The endo-type cellulase increased the degree of freedom of cellulose chains in the amorphous regions of cotton at the initial stage of the hydrolytic reaction, leading to major improvements in the moisture-adsorbing properties of cotton. The cellulase then caused the rapid decrease in the size of the amorphous regions with the release of reducing sugars as endo-cleavages in the amorphous regions increased, which reduced the hygroscopicity. The decrease in the hygroscopicity of cotton during enzymatic hydrolysis was followed by a second increase, as the cotton became more amorphous as a consequence of further hydrolysis of the crystalline regions of cotton. The effect of cellulase on the apparent degree of polymerization and the physical strength of cotton became detectable at the later stage of cellulolysis.

Journal Article↗
PubMed1986

Human ventilatory response to washed and unwashed cottons from different growing areas.

Thirty volunteer subjects were exposed to controlled amounts of respirable dust generated by the carding of cotton in an experimental cardroom. Eighteen exposures each lasting six hours were performed while carding unwashed and washed cottons from the three major growing regions of the United States. Elutriated dust was analysed gravimetrically and was comparable (0.59 mg/m3 +/- 0.04) for all exposures. Spirometry was recorded before and after each exposure. California cotton resulted in a significantly smaller fall in FEV1 than cotton of the same grade from Texas or Mississippi. All washed cottons resulted in reduced declines when compared with unwashed cottons. For 17 subjects breathing zone personal total dust samples were analysed for airborne endotoxin and compared with the individual's pulmonary function response. A significant correlation between endotoxin exposure and acute decrease in FEV1 was seen. The effect on FEV1 per nanogram of airborne endotoxin was greater for Mississippi cotton than for cotton from the other regions. Airborne endotoxin appears to be an important determinant of acute pulmonary effects of cotton dust. Water washing of cotton results in reduced airborne endotoxin and less bronchoconstriction.

Byssinosis↗
PubMed1991

Exposure-related declines in the lung function of cotton textile workers. Relationship to current workplace standards.

To evaluate the effectiveness of the current workplace standards in preventing chronic health effects from cotton dust exposure, a 5-yr longitudinal study of a large multimill population of cotton textile and synthetic process workers, employed at a major U.S. textile company, was conducted. To control for and assess the effect of type of work area on annual change in lung function, we limited the analysis to those 1,817 subjects who, throughout their textile work history at the company, worked exclusively in cotton yarn manufacturing or slashing and weaving, or in synthetic textile mills. The expected effect of smoking on average annual change in lung function was demonstrated for both cotton and synthetic workers. Despite lower overall dust exposure, cotton yarn workers exhibited steeper annual declines in lung function than did workers in slashing and weaving; this difference persisted within each smoking category, indicating a dust potency effect. There were mill differences in annual change in lung function among cotton workers, potentially masking an exposure effect. A smoking-work area interaction persisted after adjusting for mill differences, with the largest annual declines observed in cotton yarn workers who smoke. A significant dose-response relationship was seen in cotton yarn manufacturing between annual declines in FEV1, FVC, and FEF25-75 and average exposure by mill, and the larger declines were found in mills using the highest percentage and lowest grade of cotton. Synthetic textile workers had larger declines than did cotton textile workers, which were not explained by smoking or duration of employment. Unrecognized and unmeasured causative exposures or selection bias could explain this result.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Measuring gene flow in the cultivation of transgenic cotton (Gossypium hirsutum L.).

Transgenic Bt cotton NewCott 33B and transgenic tfd A cotton TFD were chosen to evaluate pollen dispersal frequency and distance of transgenic cotton (Gossypium hirsutum L.) in the Huanghe Valley Cotton-producing Zone, China. The objective was to evaluate the efficacy of biosafety procedures used to reduce pollen movement. A field test plot of transgenic cotton (6 x 6 m) was planted in the middle of a nontransgenic field measuring 210 x 210 m. The results indicated that the pollen of Bt cotton or tfd A cotton could be dispersed into the environment. Out-crossing was highest within the central test plot where progeny from nontransgenic plants, immediately adjacent to transgenic plants, had resistant plant progeny at frequencies up to 10.48%. Dispersal frequency decreased significantly and exponentially as dispersal distance increased. The flow frequency and distance of tfd A and Bt genes were similar, but the pollen-mediated gene flow of tfd A cotton was higher and further to the transgenic block than that of Bt cotton (chi2 = 11.712, 1 degree of freedom, p < 0.001). For the tfd A gene, out-crossing ranged from 10.13% at 1 m to 0.04% at 50 m from the transgenic plants. For the Bt gene, out-crossing ranged from 8.16% at 1 m to 0.08% at 20 m from the transgenic plants. These data were fit to a power curve model: y = 10.1321x-1.4133 with a correlation coefficient of 0.999, and y = 8.0031x-1.483 with a correlation coefficient of 0.998, respectively. In this experiment, the farthest distance of pollen dispersal from transgenic cotton was 50 m. These results indicate that a 60-m buffer zone would serve to limit dispersal of transgenic pollen from small-scale field tests.

Agriculture↗
PubMed2001

Larval mortality and development of Pseudoplusia includens (Lepidoptera: Noctuidae) reared on a transgenic Bacillus thuringiensis-cotton cultivar expressing CryIAc insecticidal protein.

The effects of a transgenic Bacillus thuringiensis (Bt)-cotton cultivar (DPL 32) on three instars of the soybean looper, Pseudoplusia includens (Walker), were determined in laboratory studies. First, third, and fifth instars were fed field collected Bt-cotton leaves for 1, 2, four and 7 d or until pupation, and then transferred to artificial diet. Mortality during the larval stage increased linearly in response to an increase in the length of feeding time on Bt-cotton by first and third instars. The maximum mortality of about two out of three larvae occurred for first instars fed on Bt-cotton until pupation. For the fifth instar, there was no significant response to feeding time; however, most of these larvae reached pupation before 4 d of feeding on Bt-cotton. The length of the larval developmental period also increased linearly with an increase in feeding time on Bt-cotton in first and third instars; again, there was no significant response in the fifth instars. For both mortality and larval developmental time, the linear trend lines for the first and third instars were quite similar. Pupal weight declined linearly in the first and fifth instars in response to feeding time on Bt-cotton. Although pupal weight also declined for third instars, the response was not linear. The effect of Bt-cotton appears not to extend past pupation in that there were no significant responses in mortality and developmental time of pupae during the pupal stage. These data indicate that larvae surviving Bt-cotton are adversely affected in several ways, which should be considered in evaluating Bt-cotton suppression of soybean looper infestations.

Animals↗
PubMed2005

Fitness of Cry1A-resistant and -susceptible Helicoverpa armigera (Lepidoptera: Noctuidae) on transgenic cotton with reduced levels of Cry1Ac.

The performance of Helicoverpa armigera (Hübner) on 15-wk-old cotton plants was compared for a susceptible strain, a near-isogenic laboratory-selected strain, and F1 progeny of the two strains. Glasshouse experiments were conducted to test the three insect types on conventional plants and transgenic plants that produced the Bacillus thuringiensis (Bt) toxin Cry1Ac. At the time of testing (15 wk), the Cry1Ac concentration in cotton leaves was 75% lower than at 4 wk. On these plants, < 10% of susceptible larvae reached the fifth instar, and none survived to pupation. In contrast, survival to adulthood on Cry1Ac cotton was 62% for resistant larvae and 39% for F1 larvae. These results show that inheritance of resistance to 15-wk-old Cry1Ac cotton is partially dominant, in contrast to results previously obtained on 4-wk-old Cry1Ac cotton. Growth and survival of resistant insects were similar on Cry1Ac cotton and on non-Bt cotton, but F1 insects developed more slowly on Cry1Ac cotton than on non-Bt cotton. Survival was lower and development was slower for resistant larvae than for susceptible and F1 larvae on non-Bt cotton. These results show recessive fitness costs are associated with resistance to Cry1Ac.

Animals↗
PubMed2006

Cadherin-based resistance to Bacillus thuringiensis cotton in hybrid strains of pink bollworm: fitness costs and incomplete resistance.

Recessive resistance to Bacillus thuringiensis (Bt) cotton, Gossypium hirsutum L., in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), is associated with three resistance alleles (r1, r2, and r3) of a cadherin gene. Previous experiments based on measurement of fitness components in Bt-resistant and Bt-susceptible strains revealed that fitness costs and incomplete resistance are associated with resistance. Here, we used two hybrid strains of pink bollworm, each containing a mixture of susceptible and resistant individuals, and polymerase chain reaction (PCR) amplifications to test the association between cadherin genotype and fitness components for individuals sharing a common genetic background. All survivors on Bt cotton had two r alleles, confirming that recessive cadherin alleles are tightly linked with resistance to Bt cotton. On non-Bt cotton, significantly greater developmental time for rr than ss larvae indicated a recessive fitness cost, but costs did not affect survival or pupal weight. Incomplete resistance was manifested as longer developmental time, lower survival, and smaller pupal weight in rr individuals developing on Bt cotton compared with non-Bt cotton. As in previous experiments, no significant variation in performance on Bt cotton was detected among rr genotypes. However, a meta-analysis of data from seven experiments revealed that survival on Bt cotton relative to non-Bt cotton was lower in r2r3 and higher in r1r2 compared with the other rr genotypes. Assessment of fitness components associated with cadherin genotypes in hybrid strains of pink bollworm confirms that recessive resistance to Bt cotton is associated with recessive fitness costs and incomplete resistance.

Animals↗
PubMed2002

[Dynamics of predatory natural enemy community in cotton fields].

The dynamics of predatory natural enemy community in cotton field along the Yangtze River in Anhu province was studied. The results showed that there were totally 19 species of predatory natural enemies, and the dominant species were Propylaea japonica, Erigonidium graminicola, Theridium octomaculatum, Misumenops tricuspidatus, Orius minutes and Geocoris ochropterus. The predatory natural enemies in the cotton fields were rather abundant in the whole growing period of cotton, except the rainy season. Among the dominant species, P. japonica, M. tricuspidatus, O. minutes and G. ochropterus were distributed mainly in the upper and middle parts of cotton plants, while E. graminicola and T. octomaculatum mainly in the middle and lower parts of cotton plants. The diversities of the community were relatively high in the early developmental period of cotton, and reached the top level in the bud and flowering period of cotton in the first 10 days of July, then declined successively hereafter. The principal factor affecting the diversity was species richness in the early developmental period of cotton (from shoot period to bud and flowering period), and species evenness in the late developmental period of cotton (from flowering and boll period to boll opening period). The characteristics of the community were relatively analogous before the second 10 days of August (from shoot period to flowering and boll period of cotton), but after this period, the characteristics changed obviously with the features of the dominant species getting more and more conspicuous.

Animals↗