Injury to preflowering and flowering cotton by brown stink bug and southern green stink bug

The impact of brown stink bug, Euschistus servus (Say), and southern green stink bug, Nezara viridula (L.), injury was evaluated on preflowering and flowering cotton, Gossypium hirsutum L., plants in no-choice tests. Vegetative stage cotton seedlings and reproductive structures, including flower buds (square) and bolls, were infested with adults and/or nymphs of both species. There were no significant differences in height, height to node ratio, square retention, and flower initiation for cotton seedlings or plants with a match-head square between southern green stink bug adult- or brown stink bug adult-infested and noninfested treatments. Abscission for individual large squares (precandle) and multiple squares (medium and small square on the same sympodial branch) was not significantly different among infested and noninfested treatments for the following species and developmental stages: brown stink bug adults, southern green stink bug adults, and third and fourth to fifth instar southern green stink bug nymphs. In boll infestation studies, the relationship between boll maturity, expressed as heat units beyond anthesis, and boll growth, abscission, hard locked carpels, seedcotton yield, and seed germination was measured. Brown stink bug induced abscission in bolls that had accumulated > 0-350 heat units beyond anthesis. Boll growth and seedcotton yield was significantly lower for bolls infested with brown stink bug through 266.5 and 550 heat units beyond anthesis, respectively. The proportion of hard locked carpels per boll was significantly greater for the infested treatment in a cohort of bolls that accumulated from 51 to 400 heat units beyond anthesis. Seed germination in bolls infested with brown stink bug was significantly lower in bolls aged 101-600 heat units beyond anthesis.     

Boll injury and yield losses in cotton associated with brown stink bug (Heteroptera: Pentatomidae) during flowering

Brown stink bug, Euschistus servus (Say), was infested on cotton, Gossypium hirsutum L., plants during reproductive stages to determine the effects on boll injury and seedcotton yield. During each week in 2002 and 2003, significantly more bolls with > or = 1 injured locule, bolls with > or = 2 injured locules, and bolls with discolored lint were recorded on stink bug-infested plants compared with that on noninfested plants. Significantly fewer bolls displayed external injury on the boll exocarp compared with bolls with only internal locule injury. Boll injury was significantly underestimated by the presence of external symptomology. The boll population increased 6.6- and 5.1-fold from weeks 1-5 in 2002 and 2003, respectively. There was a corresponding 6.2- and 4.6-fold increase in 2002 and 2003, respectively, for total bolls injured from weeks 1-5. Percentage of boll injury ranged from 10.7 (week 4) to 27.4 (week 2) in 2002 and from 9.2 (week 3) to 16.0 (week 2) in 2003. Percentage of injury was greatest during weeks 1 and 2 in both years and also in week 5 in 2002. Brown stink bug significantly reduced seedcotton yield of bolls present on cotton plants during weeks 1, 2, and 5 in 2002 and in weeks 4 and 5 in 2003. However, total seedcotton yield, as a function of bolls exposed to brown stink bug and subsequent bolls produced on plant in the absence of stink bugs, was not significantly different for plots infested during weeks 1-4 in 2002 and weeks 1-3 in 2003. Flowering period and boll population influence the severity of stink bug injury on seedcotton yield. Infestation timing and number of bolls should be considered, in addition to insect densities, when initiating treatments against brown stink bug.     

Cotton boll age influences feeding preference by brown stink bug (Heteroptera: Pentatomidae)

Cotton plants were infested with brown stink bug, Euschistus servus (Say), to define cotton boll age classes (based on heat unit accumulation beyond anthesis) that are most frequently injured during each of the initial 5 wk of flowering. Bolls from each week were grouped into discrete age classes and evaluated for the presence of stink bug injury. Brown stink bug injured significantly more bolls of age class B (approximately 165-336 heat units), age class C (approximately 330-504 heat units), and age class D (approximately 495-672 heat units) during the initial 3 wk in both years and in week 5 in 2002 compared with other boll ages. Generally, the frequency of injured bolls was lowest in age class A (< or = 168 heat units) during these periods. The preference by brown stink bug for boll age classes B, C, and D within a week was similar when ages were combined across all 5 wk. Based on these data, bolls that have accumulated 165.2 through 672 heat units beyond anthesis (approximately 7-27-d-old) are more frequently injured by brown stink bug when a range of boll ages are available. The boll ages in our studies corresponded to a boll diameter of 1.161-3.586 cm with a mid-range of 2.375 cm. A general protocol for initiating treatments against stink bugs is to sample bolls for evidence of injury as an indicator of presence of infestations in cotton. Sampling bolls within a defined range, which is most likely to be injured, should improve the precision of this method in detecting economic stink bug infestations in cotton.     

Stink Bug Feeding Induces Fluorescence in Developing Cotton Bolls

Background

Stink bugs (Hemiptera: Pentatomidae) comprise a critically important insect pest complex affecting 12 major crops worldwide including cotton. In the US, stink bug damage to developing cotton bolls causes boll abscission, lint staining, reduced fiber quality, and reduced yields with estimated losses ranging from 10 to 60 million dollars annually. Unfortunately, scouting for stink bug damage in the field is laborious and excessively time consuming. To improve scouting accuracy and efficiency, we investigated fluorescence changes in cotton boll tissues as a result of stink bug feeding.

Results

Fluorescent imaging under long-wave ultraviolet light showed that stink bug-damaged lint, the inner carpal wall, and the outside of the boll emitted strong blue-green fluorescence in a circular region near the puncture wound, whereas undamaged tissue emissions occurred at different wavelengths; the much weaker emission of undamaged tissue was dominated by chlorophyll fluorescence. We further characterized the optimum emission and excitation spectra to distinguish between stink bug damaged bolls from undamaged bolls.

Conclusions

The observed characteristic fluorescence peaks associated with stink bug damage give rise to a fluorescence-based method to rapidly distinguish between undamaged and stink bug damaged cotton bolls. Based on the fluorescent fingerprint, we envision a fluorescence reflectance imaging or a fluorescence ratiometric device to assist pest management professionals with rapidly determining the extent of stink bug damage in a cotton field.     

Feeding preference and movement of Nezara viridula and Euschistus serous (Hemiptera: Pentatomidae) on individual cotton plants

Experiments were conducted in an environmental growth chamber to determine the movement and feeding preferences of Nezara viridula (L.) and Euschistus serous (Say) on individual cotton plants. Fifth instars were caged by species on a single cotton plant (FM 9063 B2F) containing four discrete boll sizes ranging from 1.1 to 3.0 cm in diameter over a period of 5 d per replication. Two digital video cameras were simultaneously focused on each of the four bolls per plant to visually confirm stink bug resting and movement. During the study, a total of 4,080 h of video footage was recorded and analyzed. Results showed that N. viridula and E. serous did not prefer the exact same boll sizes. In a trial with eight stink bugs per plant, N. viridula spent more time on the three larger boll classes, 1.6-2.0, 2.1-2.5, and 2.6-3.0 cm. In a separate trial with one stink bug per plant, N. viridula spent more time on the larger boll classes while E. serous exhibited the strongest preference for 1.1-1.5 and 2.1-2.5 cm bolls. N. viridula moved more often than E. serous and both species moved more often during photophase compared with scotophase. Regardless of species or number of bugs released, bolls in the smallest boll size class fell off the plant about 3 d after the bugs were released. These results confirm that scouts who are estimating stink bug damage should select bolls in the 2.1-2.5 cm diameter boll size class.     

Relationship between external stink bug (Hemiptera: Pentatomidae) boll-feeding symptoms and internal boll damage with respect to cotton lint gin-out and fiber quality

Cotton, Gossypium hirsutum L., bolls from 17 field locations in northeastern North Carolina and southeastern Virginia, having 20% or greater internal boll damage, were studied to determine the relationship between external feeding symptoms and internal damage caused by stink bug (Hemiptera: Pentatomidae) feeding. In 2006 and 2007, two cohorts of 100 bolls each were sampled at all field locations. The first cohort was removed as bolls reached approximately quarter size in diameter (2.4 cm). External and internal symptoms of stink bug feeding were assessed and tabulated. Concurrent to when the first cohort was collected, a second cohort of quarter-size-diameter bolls was identified, tagged, examined in situ for external feeding symptoms (sunken lesions), and harvested at the black seed coat stage. Harvested bolls were assessed for internal damage and locks were categorized (undamaged, minor damage, or major damage), dried, and ginned. Lint samples from each damage category were submitted for high volume instrument and advanced fiber information system quality analyses. Significant, moderately strong Pearson correlation coefficients existed between number of external stink bug feeding lesions and internal damage. Pearson correlation of total external lesions with total internal damage was stronger than any correlation among the other single components compared. Predictability plots indicated a rapid increase in relationship strength when relating external stink bug lesions to internal damage as the number of external lesions increased. Approximately 90% predictability of internal damage was achieved with four (2006) or six (2007) external lesions per boll. Gin-turnout and fiber quality decreased with increasing intensity of internal stink bug damage.     

Cotton boll abscission and yield losses associated with first-instar bollworm (Lepidoptera: Noctuidae) injury to nontransgenic and transgenic Bt cotton

Field tests were conducted in northeastern Louisiana to determine the effects of infestations by Helicoverpa zea (Boddie) on cotton bolls of varying ages. First instars were caged on bolls of nontransgenic ('Deltapine 5415') or transgenic Bacillus thuringiensis Berliner variety kurstaki (Bt) ('NuCOTN 33B') cotton from 29 June to 11 August during 1997 and 1998. Deltapine 5415 bolls that accumulated 179 (7.2 d), 281 (11.2 d), and 253 (10.1 d) heat units beyond anthesis were safe from bollworm-induced abscission at 72 h after infestation, 7 d after infestation, and at the time of harvest, respectively. NuCOTN 33B bolls that accumulated 157 (6.3 d), 185 (7.4 d), and 180 (7.2 d) heat units beyond anthesis were safe from bollworm-induced abscission at 72 h after infestation, 7 d after infestation, and at the time of harvest, respectively. Bollworm larvae reduced seedcotton weights of Deltapine 5415 bolls that accumulated between 58.5 (2.3 d) and 350.5 (14.0 d) heat units beyond anthesis. Seedcotton weights of NuCOTN 33B bolls that accumulated between 0 and 281 (11.2 d) heat units beyond anthesis were reduced by bollworm injury. Deltapine 5415 and NuCOTN 33B bolls that accumulated 426.5 (17.1 d) and 299.5 (12.0 d) heat units beyond anthesis, respectively, before infestation were not injured by first-instar bollworm larvae. These data provide information about late-season insecticide termination strategies for bollworms on nontransgenic and transgenic Bt-cotton. This, in turn, will help pest managers determine when insecticides are no longer economical during the late season.     

Influence of corn on stink bugs (Heteroptera: Pentatomidae) in subsequent crops

In southeastern United States farmscapes, corn, Zea mays L., is often closely associated with peanut, (Arachis hypogaea L.), cotton, (Gossypium hirsutum L.), or both. The objective of this 3-yr on-farm study was to examine the influence of corn on stink bugs (Heteroptera: Pentatomidae), Nezara viridula (L.), and Euschistus servus (Say), in subsequent crops in these farmscapes. Adults of both stink bug species entered corn first, and seasonal occurrence of stink bug eggs, nymphs, and adults indicated that corn was a suitable host plant for adult survival and nymphal development to adults. Stink bug females generally oviposited on cotton or peanut near the interface, or common boundary, of the farmscape before senescence of corn, availability of a new food, or both. Adult stink bugs dispersed from crop to crop at the interface of a farmscape in response to senescence of corn, availability of new food, or both. In corn-cotton farmscapes, adult stink bugs dispersed from senescing corn into cotton to feed on bolls (fruit). In corn-peanut farmscapes, adult stink bugs dispersed from senescing corn into peanut, which apparently played a role in nymphal development in these farmscapes. In the corn-cotton-peanut farmscape, stink bug nymphs and adults dispersed from peanut into cotton in response to newly available food, not senescence of peanut. Stink bug dispersal into cotton resulted in severe boll damage. In conclusion, N. viridula and E. servus are generalist feeders that exhibit edge-mediated dispersal from corn into subsequent adjacent crops in corn-cotton, corn-peanut, and corn-peanut-cotton farmscapes to take advantage of suitable resources available in time and space for oviposition, nymphal development, and adult survival. Management strategies for crops in this region need to be designed to break the cycle of stink bug production, dispersal, and expansion by exploiting their edge-mediated movement and host plant preferences.     

Treatment thresholds for stink bugs (Hemiptera: Pentatomidae) in cotton

The green stink bug, Acrosternum hilare (Say), the southern green stink bug, Nezara viridula (L), and the brown stink bug, Euschistus servus (Say), were predominant phytophagous Pentatomidae detected during 1995-1997 in cotton in South Carolina. These species occurred in similar numbers in conventional and transgenic cotton 'NuCOTN33B', containing the gene for expression of CryIA(c) delta-endotoxin of Bacillus thuringiensis Berliner variety kurstaki. Adult stink bugs moved into cotton from wild and cultivated alternate hosts during July, and reproducing populations usually were detected in cotton from late July into September. Applications of either methyl parathion (0.56 kg [AI]/ha) directed for stink bugs or lambda-cyhalothrin (0.037 kg [AI]/ha) or cyfluthrin (0.056 kg [AI]/ha) for control of cotton bollworm, Helicoverpa zea (Boddie), provided effective control of pentatomids in NuCOTN33B or conventional 'DP5415' and increased yields compared with untreated plots. Fiber quality did not differ among treated or untreated plots of NuCOTN33B. The ground-cloth technique was used to estimate populations of stink bugs, and data indicated that treatment at one bug per 2 m of row adequately protected cotton from yield loss due to stink bug damage. Observations on boll damage indicated that treatment might be necessary if >20-25% reveal internal symptoms of feeding injury during mid- to late season. More detailed damage thresholds should be developed to complement an approach based on population monitoring. This study validated current recommendations for management of pentatomids in cotton, demonstrated the necessity of threshold use for stink bugs in transgenic cultivars expressing endotoxin from B. thuringiensis, and provided insight into further development of management options for pentatomids in the crop.     

Identification of Stink Bugs Using an Electronic Nose

Stink bugs are recognized as pests of several economically important crops, including cotton, soybean and a variety of tree fruits. The Cyranose 320 was used for the classified investigation of stink bug. Stink bugs including males and females of the southern green stink bugs, Nezara viridula, were collected from crop fields around College Station, TX. Results show that the released chemicals and chemical intensity are both critical factors, which determine the rate that the Cyranose 320 correctly identified the stink bugs. The Cyranose 320 shows significant potential in identifying stink bugs, and can classify stink bug samples by species and gender.     

Pathogenic aspects of Pantoea agglomerans in relation to cotton boll age and Dysdercus cingulatus (Fabricius) transmitting seed and boll rot in cotton germplasm

Bacterial seed and boll rot is a newly emerging cotton disease in Pakistan. Twenty-one cotton varieties were screened to find resistance source against the disease. None of these was found to be resistant. Five cotton varieties (CIM-595, MK2, BT-986, BT-986 & SG-1) having 700–1400 Area under disease progress curve (AUDPC) units were found to be moderately resistant to the disease. SLH-317, FH-942, BT-222, BT-666, MNH-457 ranging from 1401–1700 AUDPC units were moderately susceptible while MNH-456, SLH-336, 9811, FH-942, MNH-886 susceptible to boll rot. Seven varieties (FH-114, FH-113, BT-7, BT-212, SLH-BT-4, BT-212 and FH-941) were highly susceptible to bacterial seed and boll rot indicated by 2001–2300 AUDPC units. Biochemical tests identified bacterial isolates as Pantoea agglomerans. Different inoculation techniques were assessed for bacterial pathogenicity and symptoms of boll rot were only observed in needle punctured bolls. One, two and three weeks old bolls were mechanically inoculated by injecting bacterial suspension to evaluate the boll’s age impact on disease severity. Maximum severity was observed in two weeks old bolls. Red cotton bugs (Dysdercus cingulatus) were fed on artificially inoculated diseased bolls and then transferred on healthy bolls. Diseased symptoms were noticed on healthy cotton bolls. Bacterial colonies were recovered and red cotton bug was confirmed as the disease-transmitting vector.     

Transmission of cotton seed and boll rotting bacteria by the southern green stink bug (Nezara viridula L.)

AIMS: To determine the ability of the southern green stink bug (SGSB) (Nezara viridula L.) to transmit Pantoea agglomerans into cotton (Gossypium hirsutum) bolls. METHODS AND RESULTS: An SGSB laboratory colony was kept on fresh green beans. A P. agglomerans variant resistant to rifampicin (Rif) (strain Sc 1-R) was used as the opportunistic cotton pathogen. Adult insects were individually provided green beans that were sterilized and then soaked in either sterile water or in a suspension of strain Sc 1-R. Insects were individually caged with an unopened greenhouse-grown cotton boll. After 2 days, live SGSB were collected, surfaced sterilized, ground, serially diluted, and then plated on nonselective media and media amended with Rif. Exterior and interior evidence of feeding on bolls was recorded 2 weeks after exposure to insects. Seed and lint tissue were harvested, ground, serially diluted, and then plated on media with and without Rif. Bacteria were recovered on nonselective media from all insects, and from seed and lint with signs of insect feeding at concentrations ranging from 10(2) to 10(9) CFU g(-1) tissue. The Sc 1-R strain was isolated only from insects exposed to the marked strain and from seed and lint of respective bolls showing signs of insect feeding. Evidence of insect feeding on the exterior wall of the carpel was not always apparent (47%), whereas feeding was always observed (100%) on the interior wall in association with bacterial infections of seed and lint. CONCLUSIONS: Nezara viridula readily ingested the opportunistic P. agglomerans strain Sc 1-R and transmitted it into unopened cotton bolls. Infections by the transmitted Sc 1-R strain caused rotting of the entire locule that masked internal carpel wounds incurred by insect feeding. Bacteria were recovered from penetration points by insects not exposed to the pathogen, but locule damage was limited to the area surrounding the feeding site (c. 3 mm). SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that demonstrates the ability of SGSB to acquire and transmit plant pathogenic bacteria into cotton bolls.     

苗期遮荫对棉花产量与品质形成的影响

为揭示棉麦两熟共生期遮荫对棉花产量与品质形成的影响。在棉花苗期利用模拟棉麦两熟共生期遮荫的方法进行了研究。结果表明,遮荫对棉铃形成的影响因果枝,果节部位而异,遮荫有利于棉株下（1-3果枝）,中（4-6果枝）,上（7-9果枝）部果枝内围（1-2果节）铃的形成,对外围（≥3果节）尤其顶部果枝（≥10果枝）外围铃形成不利,从而决定铃重也随果枝,果节部位相应地变化,但遮荫对单株平均铃重的影响畔 小,变遮荫棉花籽棉产量而论,下,中部果枝的内围铃籽棉产量高于常规棉,在上,顶部果枝则相反,各部位果枝外围铃的籽棉产量均低于常规棉,遮荫棉花内,外围铃分布为1：0.36(常规棉为1：0.58),产量分布为1：0.42(常规棉为1：0.72)。苗期遮荫对棉纤维,棉籽品质性状的影响也主要在顶部果枝和上部果枝外围铃,综合分析遮荫棉花产量与品质的形成,棉花苗期耐遮荫性品种间存在差异。在本研究中以中9418耐遮荫性最强,中棉所19和春矮早次之。     

Crop-specific mortality of southern green stink bug eggs in Bt- and non-Bt cotton,soybean and peanut

Increasing insecticide use against stink bugs erodes benefits accrued to cotton production in the southeastern USA by eradication of the boll weevil and widespread use of Bt-transgenic cotton. Biological control programs designed to mitigate the impact of these pests would be beneficial; therefore, we sought to identify and assess naturally occurring biological control agents of stink bug eggs in cotton, peanut and soybeans, three important crops and stink bug hosts in the region. Two studies were conducted utilising digital imaging of sentinel egg masses to capture enemies present and sequential imaging over time to characterise the type and amount of damage inflicted on the egg masses. The first study utilised plots of soybean, Bt cotton, non-Bt cotton and peanut. The second study focused on ant predation in cotton by excluding fire ants from half of the plots. Sentinel egg masses of the southern green stink bug were placed in all plots at weekly intervals and were photographed at placement and at intervals over 72 h. Surviving egg masses were collected and held in the laboratory to assess parasitism in the first study. Predation of eggs was high in peanut (74–86%) and soybean (39–65%), and lower in Bt (26–34%) and non-Bt (4–21%) cotton over the two years. Parasitism was low overall (0.17–19.0%). Most egg predation in cotton and peanut was attributable to fire ants, whereas long-horned grasshoppers dominated in soybean. Exclusion of fire ants in cotton significantly reduced egg mortality, indicating their predominance as mortality agents in cotton.     

Boll weevil (Coleoptera: Curculionidae) survival through cotton gin trash fans

There is concern that cotton gins may serve as loci for reintroduction of boll weevils, Anthonomus grandis grandis Boheman, to eradicated or suppressed zones when processing weevil-infested cotton from neighboring zones. Previous work has shown that virtually all weevils entering the gin in the seed cotton will be removed before they reach the gin stand. Those not killed by the seed cotton cleaning machinery will be shunted alive into the trash fraction, which passes through a centrifugal trash fan before exiting the gin. The objective of this study was to determine survival potential of boll weevils passed through a trash fan. Marked adult weevils were distributed in gin trash and fed through a 82.6-cm (32.5-in.) diameter centrifugal fan operated across a range of fan-tip speeds. A small number of boll weevils were recovered alive immediately after passage through the fan, but all were severely injured and did not survive 24 h. In another experiment, green bolls infested with both adult- and larval-stage weevils were fed through the fan. Several teneral adults survived 24 h, and there was no evidence that fan-tip speed affected either initial survival of weevils, or the number of unbroken boll locks that could harbor an infesting weevil. Thus, designating a minimum fan-tip speed for ensuring complete kill is not possible for the boll weevil. Experiments suggest that a device installed in a gin that partially crushes or cracks bolls open before entering a trash fan will increase mortality, possibly enough that further precautions would be unnecessary.     

Delayed maturity associated with southern green stink bug (Heteroptera: Pentatomidae) injury at various soybean phenological stages

Delayed maturity in soybean, Glycine max (L.) Merr., occurred in response to infestation by southern green stink bug, Nezara viridula (L.), in 4 yr of field studies. Maturity delays followed stink bug infestation that occurred only during the pod set and filling stages (R3-R5.5), and infestations at R3-4 and R5 resulted in delayed maturity more consistently than did infestation at R5.5. Infestation levels of six stink bugs per 0.3 m of row for 7-14 d generally were required to delay soybean maturity. The greatest impact on seed yield and quality parameters followed stink bug infestations that occurred during R3-R5.5, which corresponded closely with the periods of infestation that resulted in delayed maturity. If both delayed maturity and yield reduction are considered, the pod elongation through late pod filling stages were most critical for protecting soybeans from southern green stink bugs.     

Toxicity of insecticides in a glass-vial bioassay to adult brown, green, and southern green stink bugs (Heteroptera: Pentatomidae)

Adult brown, Euschistus servus (Say); green, Acrosternum hilare (Say); and southern green, Nezara viridula (L.), stink bugs were collected from soybean, Glycine max (L.) Merr., in fall 2001 and 2002 near Stoneville, MS, and Eudora, AR. A glass-vial bioassay was used to determine LC50 values for the three species of stink bugs for the pyrethroids bifenthrin, cypermethrin, cyfluthrin, lambda-cyhalothrin, and permethrin, and the organophosphates acephate, dicrotophos, malathion, and methyl parathion. Results confirmed findings of other researchers that the brown stink bug was less susceptible to pyrethroid and organophosphate insecticides than were green and southern green stink bugs. The susceptibility of all three stink bug species to the insecticides tested was very similar at both test locations. The study established baseline insecticide mortality data from two locations in the mid-South for three stink bug species that are pests of soybean and cotton, Gossypium spp. Data from the tests are valuable for future use in studies on resistance and in resistance monitoring programs.     

Relationships of abscised cotton fruit to boll weevil (Coleoptera: Curculionidae) feeding, oviposition, and development

Abscised cotton, Gossypium hirsutum L., fruit in field plots planted at different times were examined to assess adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), use of squares and bolls during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Although boll abscission is not necessarily related to infestation, generally more bolls abscised than squares and abundances of fallen bolls were not related to the planting date treatments. During 2003, fallen squares were most abundant in the late-planted treatment. Although large squares (5.5-8-mm-diameter) on the plant are preferred for boll weevil oviposition, diameter of abscised squares is not a reliable measurement because of shrinkage resulting from desiccation and larval feeding. Fallen feeding-punctured squares and bolls were most abundant in late plantings but differences between fallen feeding-punctured squares versus fallen feeding-punctured bolls were found in only one treatment in 2003. During the same year, fallen oviposition-punctured squares were more numerous in the late-planted treatment than in the earlier treatments. Treatment effects were not found on numbers of oviposition-punctured bolls, but fallen oviposition-punctured squares were more common than bolls in the late-planted treatment compared with earlier treatments each year. Dead weevil eggs, larvae, and pupae inside fallen fruit were few and planting date treatment effects were not detected. Living third instars and pupae were more abundant in fallen squares of the late-planted treatment than in the earlier treatments and bolls of all three treatments. This study shows that fallen squares in late-planted cotton contribute more to adult boll weevil populations than bolls, or squares of earlier plantings.     

The degree of susceptibility of nectary-inoculated cotton flowers and bolls to subsequent seed infection by Aspergillus flavus is determined at or before anthesis

In greenhouse and field studies, cotton (Gossypium hirsutum L.) flowers were inoculated with Aspergillus flavus at the involucral nectaries. Bolls developing from early-season flowers had significantly higher percentages of A. flavus-infected seed than did bolls from flowers formed later in the season. Seeds from bolls inoculated 2 weeks after anthesis had the same infection levels as those from flowers inoculated at anthesis. These results indicate that early-season flowers are predisposed to A. flavus infection and that the degree of susceptibility at anthesis is retained through early boll development.     

Effect of kinetin concentration and methods of application on seed germination, yield components, yield and fiber properties of the Egyptian cotton (Gossypium barbadense)

Two field experiments in 1993 and 1994 as well as a laboratory germination experiment were conducted on the Egyptian cotton cultivar Giza 75 (Gossypium barbadense) to determine the effect of six concentrations of kinetin (6-furfurylaminopurine) ranging from 0 to 10.0 mg l(-1) and three different methods of application: (A) seeds were soaked for 24 h before germination (laboratory experiment) or sowing (field experiment) in solutions of different kinetin concentration, (B) cotton plants were sprayed twice with different kinetin concentrations at 60 and 75 days after sowing (DAS) during the square initiation and the beginning of bolling stages, at volume solution of 480 l ha(-1). (C) Seeds were soaked in kinetin solutions before sowing as method A. In addition cotton plants were sprayed twice as method B with the same kinetin concentrations. Kinetin application improved seed viability and seedling vigour as shown by lengths of the hypocotyl, radicle and the entire seedling, as well as seedling fresh weight. Moreover, significant increases were recorded in the number of open bolls/plant, boll weight, lint and seed indices, seed cotton yield/plant, and seed cotton and lint yields/plot. The highest means were obtained at 5 mg kinetin l(-1) concentration and under method C of application. Treatments generally, had no significant effects on lint percentage, yield earliness and fiber properties. These results show that, the use of kinetin at 5 mg l(-1) for pre-soaking seeds before planting and spraying cotton plants at 60 and 75 DAS with the same concentration could improve cotton germination, seed cotton and lint yields.