Identification of Cotton Fleahopper (Hemiptera: Miridae) Host Plants in Central Texas and Compendium of Reported Hosts in the United States

Abstract

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter), is an early-season pest of developing cotton in Central Texas and other regions of the Cotton Belt. Cotton fleahopper populations develop on spring weed hosts and move to cotton as weed hosts senesce or if other weed hosts are not readily available. To identify weed hosts that were seasonably available for the cotton fleahopper in Central Texas, blooming weed species were sampled during early-season (17 March–31 May), mid-season (1 June–14 August), late-season (15 August–30 November), and overwintering (1 December–16 March) periods. The leading hosts for cotton fleahopper adults and nymphs were evening primrose (Oenothera speciosa T. Nuttall) and Mexican hat [Ratibida columnifera (T. Nuttall) E. Wooton and P. Standley], respectively, during the early season. During the mid-season, silver-leaf nightshade (Solanum elaeagnifolium A. Cavanilles) was consistently a host for fleahopper nymphs and adults. Woolly croton (Croton capitatus A. Michaux) was a leading host during the late season. Cotton fleahoppers were not collected during the overwintering period. Other suitable hosts were available before previously reported leading hosts became available. Eight previously unreported weed species were documented as temporary hosts. A compendium of reported hosts, which includes >160 plant species representing 35 families, for the cotton fleahopper is provided for future research addressing insect–host plant associations. Leading plant families were Asteraceae, Lamiaceae, and Onagraceae. Results presented here indicate a strong argument for assessing weed species diversity and abundance for the control of the cotton fleahopper in the Cotton Belt.

cotton fleahopper, host plant, cotton pest

The cotton fleahopper [Pseudatomoscelis seriatus (Reuter); Hemiptera: Miridae] was first reported in Texas cotton (Gossypium hirsutum C. Linnaeus) by Howard (1898). The fleahopper is an early-season pest that uses piercing-sucking mouthparts to feed on developing cotton fruit (i.e., squares). The affected squares are shed by the cotton plant, resulting in yield losses. Fleahopper adults typically move from senescing weed hosts to infest cotton (Reinhard 1926a, Almand 1974). Adults have been shown to leave weed hosts and migrate to adjacent cotton (Suh et al. 2004), or in some cases, have infested cotton 20 miles from the original weed host (Gaines and Ewing 1938).

Sucking insects, including the cotton fleahopper, have gained importance as pests of cotton in recent years. Reports attribute this elevated status to the adoption of transgenic cotton varieties, absence of traditional early-season insecticide sprays to control boll weevils (Anthonomus grandis grandis Boheman), and pest-specific insecticides for lepidopteran control (Armstrong and Camelo 2003, Layton et al. 2003). The aforementioned components have all been incorporated in the cotton-producing areas of the Southern Blacklands region of Central Texas. Furthermore, the Southern Blacklands region is in the advanced stages of boll weevil eradication efforts, and cotton fleahoppers could potentially become a post-eradication pest in Central Texas as well. Host plant data will be instrumental in determining sources of cotton fleahopper populations that subsequently infest cotton.

Historically, plant species in the Croton, Oenothera, Monarda, and Solanum genera have been identified as leading hosts for the cotton fleahopper during the overwintering, early-season, summer, and fall seasons, respectively. Previous reports defined the leading hosts for the fleahopper as members of the mentioned genera but the composition of plant species within these genera has varied among studies, likely because of differences in plant composition among geographical locations. Furthermore, some of these reports (Gaines and Ewing 1938, Fletcher 1940, Almand 1974, Idol and Slosser 2005) focused specifically on selected primary hosts with little regard for other hosts that may have contributed to the developing fleahopper populations. Reported hosts are further confounded by laboratory feeding (Gaylor and Sterling 1976a,b; Beerwinkle and Marshall 1999) and oviposition studies (Holtzer and Sterling 1980) or all-encompassing statements listing hosts without providing sampling data. For example, Brett (1946) and Hixson (1941) alluded to the breadth of cotton fleahopper host plants but failed to provide sampling data. Similarly, Eddy (1927) stated that "other succulent plants" were also hosts. Finally, Fletcher (1930) discussed cyclic changes in vegetation and their effects on the insect fauna in Central Texas. Because of this latter point, the prevalence of anecdotal records of host plants, and the absence of a current taxonomically accurate database of cotton fleahopper host plants, the objectives of this study were to identify temporally available weed species harboring cotton fleahoppers in the southern Blackland Prairies of Central Texas and provide a definitive and current listing of host plants associated with the cotton fleahopper.

Materials and Methods

Between 17 March 2003 and 17 March 2006, blooming herbaceous weeds, alfalfa (Medicago sativa C. Linnaeus), and soybeans [Glycine max (C. Linnaeus) E. Merrill] were sampled for cotton fleahoppers in Burleson and Robertson counties (Central Texas). As blooming weed species were identified along right-of-ways, turn-rows, and ditches, these species were subject to sampling. Gaylor (1975) previously concluded that plant species were more suitable hosts for cotton fleahoppers when flowering. Pneumatic air samplers and beat sheets were evaluated in preliminary studies on row crops, but these tools were not conducive to efficient sampling in weed hosts. Because of inconsistent plant densities and variable plant architectures in weed species, sweep nets (38.1 cm diameter) were used for sampling weed hosts. For similar reasons, the sweep net was used in previous host plant studies (Cleveland 1982, Anderson and Schuster 1983, Womack and Schuster 1987, Armstrong and Camelo 2003). Unlike some previous host plant studies that used variable sample sizes within each study (Cleveland 1982, Snodgrass et al. 1984, Fleischer and Gaylor 1987), a uniform protocol of three samples (50 sweeps/sample) for each sample site was implemented in this study. Because of this sampling protocol, plant species that were in bloom but not in sufficient quantity to support 150 sweeps were not sampled. Plants were sampled twice per week at 3- to 4-d intervals unless precluded by inclement weather. In some instances, multiple sites of the same plant species were sampled because of the overall abundance of these species.

Materials sampled by sweep nets were placed in 3.79-liter Ziploc bags, returned to the laboratory, and placed in a freezer to facilitate processing of samples. Adults and nymphs of cotton fleahoppers were counted. Adults were placed under a dissecting scope, and the ventral side was examined for the presence of ovipositor or male genitalia. Voucher specimens of wild host plant species were collected and sent to the S.M. Tracy Herbarium at Texas A&M University, College Station, TX, for identification and cataloging.

To determine the presence of cotton fleahoppers in associated temporal host plant species, sampling continued throughout the year beginning on 17 March 2003. Temporal occurrence of plant species was categorized into early season (17 March-31 May), mid-season (1 June-14 August), late season (15 August-30 November), and overwintering (1 December-16 March). These categories coincided with local farming and production practices. Host plants were presumed to be and defined as those species where cotton fleahopper adults and/or nymphs were present. Because nymphs do not have wings to move from host to host, weed species yielding nymphs were considered likely reproductive hosts. In total, 76 sites of weed species and six sites of cultivated species (Glycine max and Medicago sativa) were sampled during the 3-yr study. Although some weed species were only sampled 1 yr because of the variable yearly occurrence or abundance, these data were included to show the range of plant utilization by cotton fleahoppers in the region.

Because of taxonomic revisions of previously reported plants and their respective authorities, the compendium of cotton fleahopper host plants presented here was formulated from a literature review beginning with Howard (1898) through 2008. Refereed journal articles, proceedings, Federal and State Agency bulletins, and theses and dissertations with specific reference to cotton fleahopper and host plant associations were reviewed. Sterling and Dean (1977) were consulted for earlier reports of host plant associations. The botanical nomenclature presented follows that of Jones et al. (1997). Some previous reports only provided common names of host plants. Where this occurred, the host plants were assigned to genera only (e.g., ragweed = Ambrosia spp.; horsemint = Monarda spp.) for inclusion in this report. Where host species occurred outside of Texas, online searches were conducted using http://plants.usda.gov/index.html to locate current taxonomic designations.

The PROC MEANS statement (SAS Institute 2004) and the SUM and BY options were used to generate descriptive statistics of the number of cotton fleahopper adults and nymphs in temporal host plants sampled during this study. Similarly, the mean proportions of adults that were female were determined using the MEAN and BY options of the PROC MEANS statement.

Results and Discussion

Cotton fleahopper adults and nymphs were collected from various host plants during each sampling year. Of the 36 plant species sampled in this study (Table 1), the following eight weed species were previously unreported hosts: Amaranthus hybridus C. Linnaeus; Amaranthus retroflexus C. Linnaeus; Bradburia pilosa (T. Nuttall); Melilotus indicus (C. Linnaeus) C. Allioni; Rudbeckia amplexicaulis M. H. Vahl; Ruellia nudiflora (G. Engelmann ex A. Gray) I. Urban; Verbena neomexicana (A. Gray) J. K. Small variety hirtella L. Perry; and Verbesina encelioides (A. Cavanilles) G. Bentham and J. Hooker ex A. Gray. Of the 23 previously reported hosts sampled during this study, all but three species (Capsella bursa-pastoris (C. Linnaeus) F. Medikus; Helianthus annuus C. Linnaeus; and Lamium amplexicaule C. Linnaeus) yielded cotton fleahoppers. In addition to these latter three species, five more species sampled in our study were nonhosts.

Table 1.

Summary of plant species sampled for cotton fleahoppers during 2003–2006 in Central Texas and plant host status

 

Common names based on designation by Hatch et al. (1990).

 

–, cotton fleahoppers were not encountered.

The seasonal occurrence of cotton fleahopper adults and nymphs in Central Texas plants are shown in Tables 2 and 3, respectively. In all years, Oenothera speciosa T. Nuttall was the leading host for adults during the early season (Table 2). Ratibida columnifera (T. Nuttall) E. Wooton and P. Standley was the second leading host in the 2 yr that this weed was sampled. The third leading host for adults was Solanum elaeagnifolium A. Cavanilles during 2003 but Rudbeckia amplexicaulis M. H.Vahl replaced Solanum elaeagnifolium in this position during 2004 and 2005. S. elaeagnifolium did not occur during the early season in these latter years. The leading early-season host for nymphs during 2003 and 2004 was R. columnifera; R. amplexicaulis was the leading host during 2005 (Table 3). Second and third leading hosts varied yearly during the study but included S. elaeagnifolium, Oenothera speciosa, Conyza canadensis (C. Linnaeus) A. Cronquist variety canadensis, and Medicago sativa.

Table 2.

Temporal mean no. of cotton fleahopper adults per 50-sweep sample (per sweep; n) collected in identified plants of Central Texas, where n represents no. of 50-sweep samples

 

–, plant species not sampled because of insufficient plant stand or completely absent.

Table 3.

Temporal mean no. of cotton fleahopper nymphs per 50-sweep sample (per sweep; n) collected in identified plants of Central Texas, where n represents no. of 50-sweep samples

 

–, plant species not sampled because of insufficient plant stand or completely absent.

In all years, cotton fleahopper adults were first collected during late March or early April. The identified leading early-season hosts observed in this study agree with previous reports. However, our early-season observations indicated that during 2003 adults were present in other species before O. speciosa, a previously reported preferred host. Esquivel (2005) initially reported the presence of cotton fleahoppers in R. rugosum (C. Linnaeus) C. Allioni. Fleahopper adults were collected in Chaerophyllum tainturieri W. J. Hooker variety tainturieri, Medicago polymorpha C. Linnaeus, Medicago sativa C. Linnaeus, Melilotus indicus (C. Linnaeus) C. Allioni, Rapistrum rugosum, and Trifolium incarnatum C. Linnaeus on 14 April during the 2003 early season. Furthermore, the highest numbers of adults were collected from R. rugosum on this date. Nymphs were not encountered. During 2004, adults were first collected in O. speciosa on 5 April followed by R. rugosum, T. incarnatum, and Xanthium strumarium C. Linnaeus on 8 April. Similarly, during 2005, adults were first collected in O. speciosa on 7 April followed by R. rugosum and M. polymorpha on 11 April.

During the mid-season, S. elaeagnifolium was consistently among the weed hosts yielding the highest average number of cotton fleahopper adults and nymphs (Tables 2 and 3), indicating that this was also a reproductive host in all sampling years. Other leading hosts for adults during this period were Verbena neomexicana (A. Gray) J. K. Small variety hirtella, and Amaranthus hybridus C. Linnaeus during 2003, Croton capitatus A. Michaux and Ratibida columnifera during 2004, and Monarda citriodora V. de Cervantes ex M. Lagasca y Segura and M. sativa during 2005. These same species were also leading hosts for nymphs (Table 3) during the mid-season; presumably, the available adults were reproducing on these hosts. M. citriodora was again confirmed as a preferred host indicated by the high capture numbers, including nymphs recovered.

Croton capitatus continued to harbor adults and nymphs into the late-season period (Tables 2 and 3) during 2003 and 2004. Numerically, this weed species harbored the most adults and nymphs during 2 sampling yr. During 2003, Solidago sp. and V. neomexicana were the other two leading species harboring nymphs (Ambrosia trifida C. Linnaeus and Solidago harbored adults). In addition to A. trifida, Amaranthus hybridus C. Linnaeus harbored adults during the 2004 late-season period. However, only A. trifida harbored cotton fleahopper nymphs. Parthenium hysterophorus C. Linnaeus and S. elaeagnifolium were the two leading hosts for adults and nymphs during the 2005 late-season period. Typically, as the year progressed, fewer and fewer hosts were available for sampling. Indeed, only one additional host (i.e., M. sativa) yielded cotton fleahoppers during the late season in 2005.

The overwintering status of the cotton fleahopper has been well documented (Reinhard 1926a, Eddy 1927, Gaines 1933, Gaines and Ewing 1938), and it is accepted that this insect overwinters in the egg stage, primarily in C. capitatus. Thus, cotton fleahoppers were not collected during the overwintering period in the conduct of this study, despite our sampling efforts throughout the year. Nonetheless, our insect collections in C. capitatus during the late-season period indicate that this weed species is indeed a preferred host at this time period.

Sex ratio data indicated that the proportion of females in the identified hosts ranged from 0.13 (A. hybridus) to 1.0 [B. pilosa (T. Nuttall)] during 2003 (Table 4). During 2004, the range for proportion of females was from 0 [Chamaecrista fasciculata (A. Michaux) E. Greene] to 0.69 (Gaura coccinea T. Nuttall ex Pursh). M. polymorpha exhibited the highest proportion of females (0.83) during 2005, whereas females were not encountered in R. rugosum. For the previously reported preferred hosts in the Oenothera, Monarda, Solanum, and Croton genera, the proportion of females were relatively high with the exception of O. speciosa during 2005. Sex ratio and ovipositional preference is affected by the species and maturity of the host plant (Gaylor 1975, Holtzer and Sterling 1980), and our findings concur with Holtzer and Sterling (1980).

Table 4.

Overall mean proportions of cotton fleahopper adults that were female collected from identified plants in Central Texas from 17 Mar. 2003 through 17 Mar. 2006, where n represents the no. of 50-sweep samples yielding female adults

 

–, plant species not sampled.

To clarify the status of plant species sampled during this study, a review of the available literature from 1898 through 2008 is presented in Table 5. Table 5 reflects reports identifying plant species sampled in field conditions as well as those from laboratory reports evaluating the effects of uncultivated host plants on cotton fleahopper behavior and biology. Plant species sampled for this study were incorporated in Table 5, providing a current listing of host plants related to the cotton fleahopper. In total, 169 species of plants distributed among 35 families have been identified as hosts for the cotton fleahopper. The leading plant families with predominant hosts were the Asteraceae (39 identified species), Lamiaceae (17 identified species), and Onagraceae (14 identified species). Some previous reports only reported common names. Where this occurred, this report assigned the common names to genera in Table 5, but these assignments are not included in the number of identified species reported. Twenty-seven plant taxa were assigned to genera only.

Table 5.

Compendium of reported host plants for the cotton fleahopper in the United States, 1898–2008

a

Designation of “Not provided” = host plants only listed; “No sampling data” = observations were made but no sampling data provided.

 

Studies reporting the indicating taxonomical synonym. AR, Arkansas; AZ, Arizona; IL, Illinois; LA, Louisiana; MS, Mississippi; NE, Nebraska; OK, Oklahoma; SC, South Carolina; TX, Texas.

The composition of plant species sampled in this study included the commonly accepted preferred hosts (primroses, nightshades, horsemints, and crotons) and other available weed species. Eight previously unreported host plants for the cotton fleahopper were identified in the Southern Blacklands region of Central Texas. Our results further indicated that some of these new hosts may harbor cotton fleahopper adults before previously reported preferred hosts are available. Furthermore, temporal captures of cotton fleahoppers indicated multiple previously unreported hosts. In some instances, these hosts were leading weed species harboring fleahoppers during respective sampling periods. The identification of these eight hosts supplements the compendium of previously identified plant species influencing the development of cotton fleahopper populations (Table 5).

Of particular interest for future cotton fleahopper host plant studies is the proposed revision to the cotton fleahopper nomenclature (Wheeler 2001). The proposed revision involves changing the specific epithet from seriatus to seriata resulting in Pseudatomoscelis seriata as a more correct identification for the cotton fleahopper. This proposed change should be monitored to ensure accurate identification of insect-host plant associations for the cotton fleahopper.

Findings presented here and the compendium of host plants for the cotton fleahoppers provide a current and taxonomically correct listing of host plants associated with the cotton fleahopper. These associations may be exploited to provide an alternative for managing this insect before the fleahopper infests cotton or begins late-season oviposition. Indeed, areawide management of weed hosts has been proposed as a tool for early-season control of insect populations (Thomas and Owen 1937; Fleischer and Gaylor 1987). The variability of seasonal hosts, identification of eight previously unreported weed hosts, and logistics (viz. weed densities, weed distribution, and ongoing boll weevil eradication efforts) encountered in our study region suggested that weed suppression as a management tool in Central Texas would require further study.

G. D. Jones (Research Biologist, USDA-ARS, Areawide Pest Management Research Unit) provided clarifications for the botanical nomenclature, and her efforts are greatly appreciated.

Author notes

This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation by the USDA for its use.