Host plants of the tarnished plant bug (Heteroptera: Miridae) in Central Texas

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has taken on added importance as a pest of cotton in the Cotton Belt after successful eradication efforts for the boll weevil (Anthonomus grandis grandis Boheman). Because the Southern Blacklands region of Central Texas is in advanced stages of boll weevil eradication, blooming weeds and selected row crops were sampled during a 3-yr study to determine lygus species composition and associated temporal host plants. L. lineolaris was the sole lygus species in the region. Thirteen previously unreported host plants were identified for L. lineolaris, of which 69% supported reproduction. Rapistrum rugosum L. Allioni and Ratibida columnifera (Nuttall) Wooton and Standley were primary weed hosts during the early season (17 March to 31 May). Conyza canadensis L. Cronquist variety canadensis and Ambrosia trifida L. were primary weed hosts during the midseason (1 June to 14 August) and late-season (15 August to 30 November), respectively. Sisymbrium irio L. and Lamium amplexicaule L. sustained L. lineolaris populations during the overwintering period (1 December to 16 March). The proportion of females and numbers of nymphs found in R. rugosum, C. canadensis, A. trifida, and S. irio suggests these weeds supported reproductive adults during the early, mid-, and late season and overwintering period, respectively. Medicago sativa L. was the leading crop host for L. lineolaris; Glycine max L. Merrill did not yield L. lineolaris. Few L. lineolaris were collected in Gossypium hirsutum L. These results provide a more comprehensive assessment of host plants contributing to L. lineolaris populations in central Texas.     

Oviposition and development of the tarnished plant bug (Heteroptera: Miridae) on field maize

Reduced insecticide use in cotton, Gossypium hirsutum L., as a consequence of the Boll Weevil Eradication Program and the broad adoption of Bt cotton, have helped make the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), a consistent pest of cotton each year in the mid-south. Maize, Zea mays L., has been implicated as having a role in the season-long dynamics of tarnished plant bug infestations in cotton. To date, no published information exists describing the quality of maize as a host for tarnished plant bug. No-choice field studies indicated that adult tarnished plant bug females oviposited into maize leaves, tassels, and ears. Laboratory studies showed that first-instar tarnished plant bugs could successfully develop to the adult stage when fed maize silks at the R1 growth stage, tassels before (VT) and during (R1) pollen shed, and milk stage (R3) kernels from the tip and base of the ear. The proportion of nymphs surviving to the adult stage on these tissues was often similar to that of broccoli, Brassica oleracea L. Nymphs did not develop to adults when fed V5 or R1 maize leaves. However, survival of first instars to the adult stage was improved when nymphs fed on tassels with pollen for 6 d and then moved to silks or leaves. Another field study showed that tarnished plant bugs reproduced in maize mainly during the tassel (VE and VT) and the R1-R3 ear growth stages, and a single new generation was produced in maize during these stages. The highest population recorded during the study (24 June 2005) consisted mostly of nymphs and was estimated to be 29,600/ha (12,000/acre). These studies showed that maize is a suitable host for tarnished plant bug reproduction and development, and its production plays a significant role in the population dynamics of the tarnished plant bug in the mid-south.     

Size-dependent feeding and reproduction by boll weevil (Coleoptera: Curculionidae)

The considerable variation in adult size of the boll weevil, Anthonomus grandis grandis Boheman, has been well documented, but the influences of adult size on reproductive rate are not known. We examined the relationship between the size of boll weevils and their feeding and oviposition. Weevils weighed to the nearest milligram were grouped into five categories based on pupal weight: < or =5, 6-10, 11-15, 16-20, and >20 mg. Numbers of lifetime punctures produced in flower buds (squares) of cotton, Gossypium hirsutum L., by both sexes of adults tended to increase with pupal weight. Boll weevil females with pupal weights >10 mg produced progeny with significantly higher survival to adulthood and also produced a higher percentage of female progeny than those with pupal weights < or =10 mg. The population growth indices for females having pupal weights >10 mg averaged 1.8-fold higher than those of females weighing < or =10 mg. Survivorship of adults of both sexes also tended to increase with pupal weight. The percentage of females laying eggs on any given day averaged 2.1 times higher when their pupal weights were >10 mg than when their pupal weights were < or =10 mg. Although small size negatively affected female reproductive potential, even extremely small females produced some viable offspring. However, the penalties of small adult size, in terms of longevity and reproductive potential, suggest that cultural practices that result in the production of small adults may be used to impact weevil populations.     

Boll weevil (Coleoptera: Curculionidae) bait sticks: toxicity and malathion content

Assays of malathion content and toxicity to boll weevil, Anthonomus grandis grandis Bohemian, were conducted on boll weevil bait sticks, now marketed as Boll Weevil Attract and Control Tubes (BWACTs; Plato Industries, Houston, TX). In general, the longer BWACTs were in the field, the lower the mortality of weevils that were exposed to them. Bioassays of weevil mortality correlated with hexane washes of BWACT surfaces showed highly variable mortality when surface malathion fell below approximately 20 ng per 1 microl of hexane, but consistently high mortality (> or = 90%) when surface malathion was above 30 ng per 1 microl of hexane. A linear equation was calculated to predict mortality as a function of malathion on a BWACT surface. Although mortality was related to surface amounts of malathion, it was unrelated to the total amount of malathion present in BWACTs. Similarly, surface malathion was unrelated to the total amount present in BWACTs. As with mortality, amount of surface malathion declined with time, but total malathion did not decline with time. Boll weevils placed on fresh BWACTs tended to accumulate more malathion and died in greater numbers as time spent on fresh tubes increased, but not as time spent on tubes aged in the field (for 5 mo total) increased. Weevils that landed on tubes after a short flight died in approximately the same numbers as those that were placed on tubes using proper methodology. The amount of malathion expected to cause 90% mortality of boll weevils subjected to proper methodology was 47% higher than for a less stringent methodology (34.3 versus 23.4 ng), which demonstrates the importance of strictly adhering to proper methodology; nevertheless, chemical assay of malathion on the BWACT surface proved to be a more consistent measure of BWACT toxicity than bioassay, and it should replace the bioassay.     

Early-season colonization patterns of the boll weevil (Coleoptera: Curculionidae) in Central Texas cotton

It is commonly believed that colonization of early-season cotton, Gossypium hirsutum L., by overwintered boll weevils, Anthonomus grandis grandis Boheman, is concentrated on field margins. However, supporting experimental evidence is not available. In 1999 and 2000, we examined colonization patterns of overwintered boll weevils in Central Texas cotton on the bases of adult collections by a pneumatic sampler and hand collections of abscised infested squares. Samples were taken from sites arranged in a grid that extended inward >70 m from the field margin. Adults were collected from shortly after seedling emergence until the flowering stage, and infested squares were collected during the one-third grown square stage. Despite numerical trends, the numbers of adult weevils collected were not significantly different between years or sexes, or among plant phenological stages. Field-to-field variation among collections was considerable and likely prevented detection of differences among these factors. Spatial patterns represented by adult weevil and infested square collections were examined by logistic regressions fitted to the respective probabilities of weevil detection at each designated sample site. Although we observed trends for slightly decreased probability of weevil detection with increased distance from the field margin, these trends were too weak to be demonstrated statistically. Our results indicate the boll weevil does not consistently exhibit a strong edge-oriented colonization pattern, and that management tactics that are predicated on these patterns, such as border sprays, should be used with caution.     

Traumatic insemination in the plant bug genus Coridromius Signoret (Heteroptera: Miridae)

In traumatic insemination, males pierce females with hypodermic genitalia and ejaculate into the body cavity rather than into the genital tract. This has resulted in the evolution of female counter-adaptations in the form of paragenitalia to reduce the direct physical costs of mating. While rare in the animal kingdom, traumatic insemination is oddly prevalent in the true bug infraorder Cimicomorpha (Heteroptera), where it occurs in six families and is thought to have arisen twice. Here, we report the discovery of traumatic insemination and elaborate paragenital development in the plant bug genus Coridromius (Miridae), representing a third, independent emergence of traumatic insemination in this infraorder.     

Common subtropical and tropical nonpollen food sources of the boll weevil (Coleoptera: Curculionidae)

It is known that substantial boll weevil, Anthonomus grandis grandis Boheman, individuals can survive mild subtropical winters in some habitats, such as citrus orchards. Our study shows that endocarp of the fruit from prickly pear cactus, Opuntia engelmannii Salm-Dyck ex. Engel.; orange, Citrus sinensis L. Osbeck.; and grapefruit, Citrus paradisi Macfad., can sustain newly emerged adult boll weevils for >5 mo, which is the duration of the cotton-free season in the subtropical Lower Rio Grande Valley of Texas and other cotton-growing areas in the Western Hemisphere. Cotton, Gossypium hirsutum L., and the boll weevil occur in the same areas with one or all three plant species (or other citrus and Opuntia species that might also nourish boll weevils) from south Texas to Argentina. Although adult boll weevils did not produce eggs when fed exclusively on the endocarps of prickly pear, orange, or grapefruit, these plants make it possible for boll weevils to survive from one cotton growing season to the next, which could pose challenges to eradication efforts.     

Survival of boll weevil （Coleoptera： Curculionidae） adults after feeding on pollens from various sources

The survival of overwintering boll weevil, Anthonomus grandis grandis （Boheman）, adults on non-cotton hosts in the Lower Rio Grande Valley （LRGV） of Texas was examined from 2001 to 2006. The success of the Boll Weevil Eradication Program, which was reintroduced into the LRGV in 2005, depends on controlling overwintering boll weevil populations. Laboratory studies were conducted using boll weevil adults that were captured in pheromone traps from September through March. The number of adults captured per trap declined significantly in the field from fall to the beginning of spring （3.5-7.0-fold）. The proportion of trapped males and females did not differ significantly. The mean weight of boll weevil adults captured in September was 13.3 mg, while those of captured adults from November to February were significantly lower and ranged from 6.7 to 7.8 mg. Our results show that boll weevil adults can feed on different plant pollens. The highest longevity occurred when adults were fed almond pollen or mixed pollens （72.6 days and 69.2 days, respectively） and the lowest when they fed on citrus pollen or a non-food source （9.7 days or 7.4 days, respectively）. The highest adult survival occurred on almond and mixed pollens [88.0%-97. 6% after 1st feeding period （10 days）, 78.0%-90.8% after 3rd feeding period （10 days）, 55. 0%-83.6% after 5th feeding period （10 days）, and 15.2%-32.4% after lOth feeding period （10 days）]. The lowest adult survival occurred on citrus pollen [52.0%-56.0% after 1st feeding period （10 days）, 13.3% after 3rd and 5th feeding periods （10 days）, and 0 after 6th feeding period （10 days）]. Pollen feeding is not a behavior restricted to adult boll weevils of a specific sex or physiological state. Understanding how boll weevil adults survive in the absence of cotton is important to ensure ultimate success of eradicating this pest in the subtropics.     

Effects of kaolin-based particle film application on boll weevil (Coleoptera: Curculionidae) injury to cotton

This study examined a non-insecticidal tactic for suppressing boll weevil, Anthonomus grandis grandis Boheman, damage to cotton, Gossypium hirsutum L. In cage assays, kaolin, a reflective white mineral, applied to excised cotton squares or to the cotton foliage, initially resulted in lower levels of boll weevil injury to squares than nontreated squares. Boll weevil oviposition and feeding on kaolin-treated squares and squares on kaolin-treated cotton plants increased when nontreated squares and cotton plants were in short supply. A laboratory assay and field trials suggested that boll weevils distinguished between cotton plots based on color differences caused by kaolin and this appeared to influence levels of damage to squares. Random sampling in small plots indicated that oviposition damage to squares in plots treated with kaolin was reduced (P < 0.05) compared with nontreated controls, except when rain washed the kaolin off the foliage. Lint yield differences were not detected between the small plots, but the kaolin-treated small plots yielded as much as 2.36 times more cotton lint than a large but unreplicated adjacent nontreated control plot, and up to 1.39 times more than another large but unreplicated adjacent plot sprayed twice with preemptive applications of azinphosmethyl when cotton squares were first developing (pinhead stage). Potentially important avenues for future research on boll weevil injury suppression using kaolin are discussed.     

Impact of reflective mulch on yield of strawberry plants and incidence of damage by tarnished plant bug (Heteroptera: Miridae).

The current study investigated the impact of reflective mulch on yield of strawberry plants and incidence of damage by tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), for three strawberry cultivars: 'Honeoye', 'Earliglow', and two sibling Dayneutrals ('Tribute' and 'Tristar', herein considered as one cultivar). Of all cultivars tested, Honeoye was the most productive and least susceptible to tarnished plant bug. For Earliglow and Honeoye, reflective mulch enhanced productivity of strawberry plants and suppressed density of nymphs per flower cluster and proportion of damaged fruits, but did not significantly impact numbers of nymphs or damaged fruits per hectare, Results with Dayneutrals were not consistently significant. Both in the presence or absence of reflective mulch, proportion of damaged fruits increased with increasing density of nymphs per flower cluster and with decreasing number of fruits harvested per row section, suggesting that planting productive strawberry cultivars or maintaining cultural practices that promote high yield may provide an effective line of defense against tarnished plant bug. These results also suggest that reflective mulch may suppress incidence of damage by tarnished plant bug both directly, by reducing number of nymphs per flower cluster, and indirectly, by enhancing productivity of strawberry plants. Economic analyses evaluating costs and benefits of using reflective mulch, as well as studies investigating mechanisms that underlie the impact of reflective mulch on yield and incidence of damage by tarnished plant bug, are still needed before reflective mulch can be implemented as a management strategy in commercial strawberry fields.     

Seasonal changes in pyrethroid resistance in tarnished plant bug (Heteroptera: Miridae) populations during a three-year period in the delta area of Arkansas, Louisiana, and Mississippi

Tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were collected from weeds at 71 locations in the delta of Arkansas, Louisiana, and Mississippi and tested with a discriminating dose bioassay for pyrethroid resistance in the spring (April-May) and again at the same locations in the fall (September-October) in 1995-1997. Percentage of mortality in the discriminating dose bioassay declined significantly (pyrethroid-resistance increased) from spring to fall by an average 18.7, 21.3, and 21.7% in Arkansas, Louisiana, and Mississippi, respectively. Pyrethroid resistance declined significantly by 26.3% from the fall of 1995 to the spring of 1996 in Mississippi, but did not significantly decline in Arkansas (4.1%) and Louisiana (13.2%). Significant decreases in resistance occurred in all 3 states from the fall of 1996 to the spring of 1997 (17.1, 38.3, and 29.8% in Arkansas, Louisiana, and Mississippi, respectively). Plant bugs from 2 locations (Indianola, MS, and Wainwright, LA) had multiple insecticide resistance to a carbamate, 2 pyrethroid, and 4 organophosphorus insecticides. However, resistance to the organophosphate acephate in plant bugs from both locations was not significant. Possible causes for the significant increases and declines in resistance from season to season are discussed.     

Characterization of microsatellite loci in the western tarnished plant bug,Lygus hesperus Knight (Hemiptera: Miridae)

A microsatellite‐enriched partial genomic DNA library of Lygus hesperus was generated and screened by sequencing. Ten polymorphic microsatellite marker loci were characterized by genotyping 92 insect samples. The observed number of alleles ranged from three to seven with an average of 4.5 (SE ± 0.45), while the effective number of alleles ranged from 1.21 to 3.02 with an average of 2.14 (SE ± 0.20). Significant deviations from Hardy–Weinberg expectations were detected at three loci. Significant linkage disequilibrium was also detected between the loci LhMS2‐54 and LhMS3‐32. Seven of the L. hesperus markers could be transferred to Lygus lineolaris.     

Evaluation of puncture types as indicators of boll weevil (Coleoptera: Curculionidae) oviposition in cotton squares

Reproductive boll weevil populations are typically identified by the presence of a frass seal and protuberance at the oviposition site in cotton squares. However, despite the occurrence of other oviposition puncture seal types and their use in previous fecundity studies, the relationship of these respective puncture seal types and oviposition has not been clearly examined. In this study, newly eclosed females (相似文献   

Specialized receptor neurons for pheromones and host plant odors in the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae)

Antennal olfactory receptor neurons in the boll weevil, Anthonomusgrandis, were investigated through single neuron recordings.Receptor neurons for both pheromone components and host plantodors were associated with type I sensilla within the sensoryband regions. Nine types of receptor neurons were identified,based on their responsiveness to the four aggregation pheromonecomponents and selected host plant odors. Three receptor neurontypes responded to either compound I, II or IV of the aggregationpheromone. Dose—response curves were similar for eachof these receptor neuron types, which differed only in theirkey compound. In each instance, I neurons responded primarilyto (+)-I, the optical isomer produced by the boll weevil whichwas found to be active in field tests. Receptor neurons forII also responded to a lesser degree to III, its aldehydic analog,at the same stimulus load. Six additional receptor neuron typesresponded to selected host plant odors: ß-caryophyllene,trans-2-hexen-l-o1 and other six carbon alcohols and aldehydes,trans-ß-ocimene, benzaldehyde, linalool, and B-bisabolol.These neurons were as responsive as, or in some cases more responsiveat the same stimulus load as receptor neurons for pheromonecomponents. Receptor neurons responsive to six-carbon alcoholsand aldehydes were generally most responsive to trans-2-hexen-l-ol.Receptor neurons for other plant odors responded principallyto only one compound among the odorants tested. However, responsesof these neurons were not uniform, suggesting possible specializationfor other unidentified key odorants. Comparisons were also madebetween single neuron and electroantennogram responses. Theresults indicate that the boll weevil, a narrowly oligaphagousinsect, detects its host plant at some distance, and utilizesinformation about a wide range of chemical structures in itsolfactory-mediated behavior.     

Influence of cotton fruit stages as food sources on boll weevil (Coleoptera: Curculionidae) fecundity and oviposition

Boll weevil, Anthonomus grandis grandis Boheman (Coloeoptera: Curculionidae), populations in the Lower Rio Grande Valley of Texas increase strongly during the squaring stage, and preemptive insecticide sprays at the pinhead square stage were designed to capitalize on that association. Laboratory assays showed that cotton plant volatiles, or leaves as a food source, do not elicit egg production in wild weevils. Boll weevils fed on large (5.5-8-mm diameter) squares for 7 d resulted in > or = 3.8-fold more gravid females that developed 4.8-fold more chorionated eggs per female than weevils fed on match-head-sized squares, or postbloom, young (5-10-d-old), or old (3-5-wk-old) bolls. When presented with a choice, nongravid females preferred to feed on young and old bolls 4.7- and 8.4-fold more, respectively, than on large squares. In the field, large squares had 7.8- and 25-fold more feeding punctures than match-head-sized squares and bolls, respectively. Oviposition increased > or = 2.7-fold when females fed on large squares compared with match-head-sized squares and bolls. Greater feeding on large squares during squaring and the associated greater fecundity explain rapid weevil population buildups shortly after large squares become well established.     

Molecular cloning of trypsin-like cDNAs and comparison of proteinase activities in the salivary glands and gut of the tarnished plant bug Lygus lineolaris (Heteroptera: Miridae)

Using specific proteinase inhibitors, we demonstrated that serine proteinases in the tarnished plant bug, Lygus lineolaris, are major proteinases in both salivary glands and gut tissues. Gut proteinases were less sensitive to inhibition than proteinases from the salivary glands. Up to 80% azocaseinase and 90% of BApNAse activities in the salivary glands were inhibited by aprotinin, benzamidine, and PMSF, whereas only 46% azocaseinase and 60% BApNAse activities in the gut were suppressed by benzamidine, leupeptin, and TLCK. The pH optima for azocaseinase activity in salivary glands ranged from 6.2 to 10.6, whereas the pH optima for gut proteinases was acidic for general and alkaline for tryptic proteinases. Zymogram analysis demonstrated that approximately 26-kDa proteinases from salivary glands were active against both gelatin and casein substrates. Three trypsin-like cDNAs, LlSgP2-4, and one trypsin-like cDNA, L1GtP1, were cloned from salivary glands and gut, respectively. Putative trypsin precursors from all cloned cDNAs contained a signal peptide, activation peptide, and conserved N-termini (IVGG). Other structural features included His, Asp, and Ser residues for the catalytic amino acid triad of serine proteinase active sites, residues for the binding pocket, and four pairs of cysteine residues for disulfide bridges. Deduced trypsin-like proteins from LlSgP2, LlSgP3, and LlGtP1 cDNAs shared 98-99% sequence identity with a previously reported trypsin-like precursor, whereas the trypsin-like protein of LlSgP4 shared only 44% sequence identity with all other trypsin-like proteins, indicating multi-trypsin forms are present in L. lineolaris.     

Comparison of direct and indirect sampling methods for tarnished plant bug (Hemiptera: Miridae) in flowering cotton

A complex of hemipterans, especially the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become a major target of insecticides in flowering cotton, Gossypium hirsutum L., in the mid-southern United States. Sampling protocols for this complex during this period of cotton development are poorly established, resulting in uncertainty about when infestations warrant treatment. Nine direct and indirect sampling methods were evaluated for bias, precision, and efficiency in cotton throughout the Mid-South during 2005 and 2006. The tarnished plant bug represented 94% of the bug complex in both years. Sweep-net and black drop-cloth methods were more efficient than other direct sampling methods, but they were biased toward adults and nymphs, respectively. Sampling dirty blooms was the most efficient indirect sampling method. The sweep-net, whole-plant, and dirty-bloom methods were more accurate than the other sampling methods evaluated based on correlations with other sampling methods. Variability attributed to the person collecting the sample was significant for all sampling methods, but least significant for the dirty-square method. Further research is needed to establish thresholds based on sweep-net, drop-cloth, dirty-square, and dirty-bloom sampling methods as these methods provide the best combinations of accuracy and efficiency for sampling tarnished plant bugs in cotton.