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Interference of Boll Trapping by Spiders (Araneida) and an Evaluation of Trap Modification to Reduce Unwanted Arthropods1

J. Scott Armstrong2 and David B. Richman3

USDA-ARS, Beneficial Research Unit, 2413 East Highway 83, Weslaco, Texas 78596 USA

J. Entomol. Sci. 42(3): 392-398 (July 2007)

Key Words trap design, grandis grandis,

Boll weevil, Anthonomus grandis grandis Boheman, eradication is nearing comple­ tion throughout the U.S. as all cotton-producing regions are in active or posteradica­ tion maintenance, with most of the active eradication occurring in Texas. The success of eradication is almost entirely based on boll weevil traps baited with grandlure and a weekly trap capture threshold of 1 weevil per trap per week used in active eradi­ cation zones (Dickerson et al. 2001, Cotton Foundation, Memphis, TN, 627 p.). The Texas Boll Weevil Eradication Foundation uses a standard 10 mg grandlure dis­ penser (Scentry Biologicals, Billings, MT) and an impregnated kill-strip of 10% (wtwt) dichlorovos DDVP ([2,2,-dichlorovinyl dimethyl phosphate]; Heron Environmental, Emigsville, PA) to kill boll in the trap and prevent their escape (Suh et al. 2003, J. Econ. Entomol. 96: 348-351). Even when a DDVP kill-strip is used in a boll weevil trap in South Texas, a significant impedance to trapping efficiency can be the predation of boll weevils by and spiders that enter the capture area of the trap. Spiders have been implicated as a significant factor in interfering with trapping effi­ ciency by preying on boll weevils or, more importantly, by webbing the entrance of the trap making it impossible for weevils to enter the capture container (Armstrong and Richman 2006, Proc. Beltwide Cotton Conf.). From 1024 boll weevil trap inspections made in the Valley in 2004 and 2005, a total of 239 (23%) were affected by webbing or predation from spiders or other , even when a DDVP kill­ strip was used in the trap (Armstrong et al. 2006, J. Econ. Entomol. 99: 323-330). A diverse group of spiders inhabiting the ground, cotton plants, and even boll weevil traps has been documented in Central Texas by Dean et al. (1982, J. Arachnol. 10: 251-260) and in the New cotton landscape (Bundy and Smith 2005, Proc.

1Received 21 August 2006; accepted for publication 21 January 2007. 2Address inquiries (e-mail: [email protected]). 3New Mexico State University, Department of Entomology, Plant Pathoiogy and Weed Science, Las Cruces, NM 88003 USA.

392 ARMSTRONG AND RICHMAN: Spider Species in Boll Weevil Traps 393

Beltwide Cotton Conf.). There is no doubt that spiders play an invaluable role in the predation of cotton pests (Pfannenstiel 2004, Proc. Beltwide Cotton Conf.); however, the influence of spiders on preying or webbing the entrance hole to boll weevil traps has not been investigated. As boll weevil eradication progresses through South Texas, a boll weevil trap that is efficient in capturing low densities of weevils will be important in the successful completion of the eradication program. In addition, the most efficient trap available also will aid in detecting and preventing low numbers of weevils from reentering cotton production areas that are deemed functionally eradicated. The objective of this study was 2-fold. One, we wanted to determine the taxa that inhabit and interfere with boll weevil traps. Two, we evaluated a trap that was modified by adding a funnel treated with a sticky adhesive on the support poll in reducing arthropod interference in boll weevil trapping. A Texas Boll Weevil Eradication Foundation (TBWEF) trap (Technical Precision Plastics, Mebane, NC) was supported by a 1 m x 1.5 cm diam conduit pole and baited with a standard 10 mg grandlure (Scentry Biologicals, Billings, MT). Other traps were

A B

Boll weevil Trap

.-- Support Pole

.-- Inverted Funnel

Iii

Fig. 1. A typical boll weevil trap and support poll (A) versus a modified trap (B) with I a funnel placed 0.3-m from ground level, and the inside of the funnel treated with sticky adhesive to prevent unwanted arthropods from climbing and en­ II, tering the trap.

I: I 394 J. Entomol. Sci. Vol. 42, NO.3 (2007)

~ 60 • TBEF+ Funnel ....c.:l !ISl TBEF Trap A 50 ~ fI) 140 30 :g >- 20 :ii: ~ :> 10 s::: ~ o

4 c. ....e B

o

c

1 March 7 March 14 March 21 March

Fig. 2. Mean (SE±) number of spiders (A), boll weevils (B), and obstructed traps from weekly inspections of boll of standard and modified boll weevil traps, operated near San Benito, Cameron County TX, March 2004. ARMSTRONG AND RICHMAN: Spider Species in Boll Weevil Traps 395

Table 1. Spider taxa collected from boll weevil traps February 23 to March 21, 2004, near San Benito, Cameron County, TX !;I

Adult Adult Total Obstruction Taxa 00 '?'? Immature spiders frequency'

Anyphaenidae 25 6.2 Hibana futilis (Banks) 7 4 13 24 6.2 Hibana sp. 1 Araneidae 146 41.2 Araneid 19 20 5.0 Araneid undetermined 2 2 Araneus sp. 2 2 Eustala anastera (Walckenaer) 6 3 9 Eustala bifida f. O. P.-Cambridge 1 1 Eustala brevispina Gertsch & Davis 1 Eustala sp. 1 1 Larinia directa (Hentz) 6 2 4 12 Metazygia sp. 3 3 Metazygia wittfeldae McCook 12 4 5 21 Metazygia zilloides (Banks) 13 12 11 36 7.5 Metepeira minima Gertsch 1 1 Neoscona arabesca (Walckenaer) 12 15 4 31 26.0 Larinia sp. 2 4 Scoloderus sp. 2 2 Undetermined Family Clubionoid 1 Gnaphosidae 1 Micaria sp. 1 Linyphiidae 5 Ceraticellus sp. 1 Eperigone sp. 4 4 Lycosidae 26 7.5 Pardosa delicatula Gertsch & Davis 6 8 Allocosa cf. floridana (Chamberlin) 1 1 Pardosa sp. 14 15 Pirata sp. 2 2 Miturgidae 6 Cheiracanthium inclusum (Hentz) 3 2 6 J. Entomol. Sci. Vol. 42, No.3 (2007) 396

Table 1. Continued. Adult Adult Total Obstruction Taxa 00 'i''i' Immature spiders frequency'

oxyopidae Hamataliwa unica Brady Philodromidae 11 Tibel/us sp. 11 11 Pholcidae Pholcid Pisauridae Dolomedes sp. 1 Salticidae 36 6.3 Habronattus sp. 2 2 Marpiss pikei (Peckham & Peckham) 1 Maevia poultoni (Peckham & Peckham) 2 Messua Iimbata (Banks) 2 3 Pelegrina galathea (Walckenaer) 2 2 5 Pelegrina sp. 1 Phidippus audax (Hentz) 12 12 Thiodina sp. 3 3 Salticid sp. 6 6 Zygobal/us sexpunctatus (Hentz) 1 Tetragnathidae Tetragnatha pal/escens Cambridge Tetragnatha sp. 10 12 Theridiidae 1 Undetermined 1 Thomisidae 12 Misumenops californicus (Banks) 1 1 Misumenops sp. 2 7 9 Misumenops dubius (Keyserling) 1 Synema viridens (Banks) 1 Males/Females/lmmatures/ Total spiders 92 46 149 287

* Obstruction frequency was calculated by dividing the number of times a spider family or specie was caught in a boll weevil trap impaired by spider webbing of the entrance hole by 80, the number of trap inspections made during the study. Only those with a frequency >5% are presented. ARMSTRONG AND RICHMAN: Spider Species in Boll Weevil Traps 397 modified by inserting the support pole through a 2-L funnel, leaving a distance of 0.3 m from the ground surface to the funnel (Fig. 1). The inside of the funnel was sprayed with Tangle-Trap® (Tangle Foot, Grand Rapids, MI), an aerosol-formulated adhesive. This modification was made to reduce or prevent arthropods from climbing the sup­ port pole and interfering with the boll weevil trap captures. Ten paired replicates of the 2 trap types (20 total traps) were spaced 50 m apart and 100 m from the next pair on the Russell Plantation near San Benito, TX, and operated from 23 February to 22 March 2004. The trapping was established along brush-lined drainage canals ori­ ented to the east and west. The trapping site is typical for south Texas cotton pro­ duction, with brush and cover along the channel canals enhancing boll weevil trap captures (Armstrong et al. 2006). Traps were inspected weekly and contents were emptied into 20-ml vials using a funnel that screwed onto the vials. Each trap was examined for spider webbing that blocked the entrance of the boll weevil trap. The collected weevils and any other arthropods on the inside of the trap catch-container were transported to the laboratory, counted, and determined to be dead or alive. Weekly collections of all weevils and other arthropods were made for 4 consecu­ tive wks as described for insects and arthropods. However, all arthropods collected on or under the traps (Le., outside the catch container) were collected by placing the entire trap in a 2-L sealable plastic bag where all arthropods, including spiders, could be caught and placed in 70% ETOH and shipped to New Mexico State Univ., De­ partment of Entomology, Plant Pathology and Weed Science (DBR) for identification. Boll weevils and spiders captured from standard and modified traps were analyzed using the PROC MIXED statement of SAS (2001, Cary, NC), where treatment (trap type), week of capture, and block (2 paired traps = 1 block) were the fixed effects. LSMEANS were compared by week of capture using the pdiff-all statement (ex = 0.05) (SAS 2001). The proportions of traps with the entrance to the trap blocked by spider webbing were compared with traps that were not obstructed using the Student­ Newman-Keuls test (ex = 0.05; SAS 2001). Because spiders were the dominant ar­ thropods found associated with boll weevil traps, the adults were identified and sexed, immatures were identified to the lowest taxonomic level as possible, and all data tabulated. The frequency of a spider family or species that was associated with obstructing the entrance hole of a boll weevil trap was calculated by dividing the number of times the spider was caught in a webbed trap by the number of trap inspections (80) made during the trapping study. Capture of boll weevils was consistent for both trap types resulting in no significant difference (F =0.21; df =1, 78; P =0.654) for the 4 consecutive wks of trapping (Fig. 2A). However, the mean number of weevils caught in obstructed traps (n = 33 ob­ structed, 5< = 13.5 ± 3.9) after 4 weekly intervals of operation was significantly lower (F =9.3; df =1,76; P =0.003) than those caught in nonobstructed traps (n =47,5< = 23.8 ± 6.9). The mean number of spiders captured on a weekly basis was numerically higher in standard boll weevil traps when compared with the modified trap; however, there was no significant difference (F = 0.47; df = 1, 18; P = 0.501), and spider numbers averaged over 2 for the first 3 wks and dropped to < 2 for the final wk (Fig. 2B). The mean numbers of traps obstructed by spider webbing at the end of weekly capture interval did not differ by trap type (Fig. 2C) and, in fact, demonstrated similar trends. This pattern is reflected in the third week of capture when both trap types decrease in the number of obstructions to <50% of the other 3 wks of capture. Arthropods other than spiders collected from the traps included 2 earwigs (Der- 398 J. Entomol. Sci. Vol. 42, NO.3 (2007) maptera), 4 ants (Hymenoptera: Formicidae), 3 cockroaches (Orthoptera: Blattelli­ dae), and 5 long-horned (Coleoptera: Cerambycidae), all of which made up <5% of the total arthropods collected over the 4 wks of trapping. The capture of the insects from these families is apparently incidental, with little impact on the numbers of boll weevils captured. A great diversity of spiders was collected from both modified and nonmodified boll weevil traps (Table 1) including 14 known families and 46 genera. The most fre­ quently collected family was Araneidae, with a total of 146 individuals, or 51 % of the total number of all spiders collected. The araneids were also most highly associated with obstruction of the entrance hole of the trap with Neoscona arabesca (Walcken­ aer) being the most frequent species obstructing the entrance hole of the trap (Table 1). Family Salticidae was the next most frequently represented group of spiders found in traps with 36 individuals or 13% of the total individuals collected from the traps. Placing a sticky trap at the base of the support pole for boll weevil traps had no effect on preventing arthropods, especially spiders, from inhabiting boll weevil traps. We are convinced that arthropods, spiders in particular, may access the boll weevil trap by routes other than by climbing the support pole from ground level (i.e., spinning silk lines). The significance of the spider webbing and the reduction of trapping efficiency should be considered as the boll weevil is being eradicated from South Texas. The most efficient trap and lure available should be adopted and used to eradicate and to monitor eradicated zones from reinfestation of the boll weevil.

Acknowledgments

The authors thank O. Zamora and V. Cardoza for assistance on this study. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.