Stored-Product
Journal of Economic Entomology, 111(3), 2018, 1476–1480 doi: 10.1093/jee/toy104 Advance Access Publication Date: 10 April 2018 Research Article
Evaluation of Light Attraction for the Stored-Product Psocids, Liposcelis entomophila, Liposcelis paeta, and Liposcelis brunnea John Diaz-Montano,1,2,5 James F. Campbell,1 Thomas W. Phillips,3 and James E. Throne4 1 Stored Product Insect and Engineering Research Unit, USDA, Agricultural Research Service, Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, KS 66502, 2Current address: Corporación Colombiana de Investigación Agropecuaria (Corpoica), C.I. La Selva, Km. 7 Vía Rionegro-Las Palmas, Rionegro, Antioquia, Colombia, 3Department of Entomology, Kansas State University, 123 West Waters Hall, Manhattan, KS 66506, 4USDA, Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, 9611 South Riverbend Avenue, Parlier, CA 93648, and 5Corresponding author, e-mail:
[email protected]
Subject Editor: John Trumble Received 6 February 2018; Editorial decision 25 March 2018
Abstract Psocids have become global pests of stored commodities as they can cause considerable economic losses. These insects are difficult to control because they have developed resistance to many chemical insecticides.Therefore, it is crucial to investigate alternative integrated pest management (IPM) approaches, such as the use of light attraction for monitoring and/or controlling psocids. Light attraction has been studied for Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) but not for other psocid species. In this study, we investigated the response of adults of three psocid species (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman, and Liposcelis brunnea Motschulsky, to six wavelengths of light from light-emitting diode (LED) in paired-choice pitfall tests. L. entomophila females and males were not attracted to any of the wavelengths tested. L. paeta females responded positively to two ultraviolet (UV) wavelengths (351 and 400 nm) and to green light (527 nm), while males did not respond to any light. L. brunnea females and males responded positively to all six wavelengths evaluated. Most of the LEDs that elicited positive responses to L. paeta females and L. brunnea females and males were also preferred when these lights were presented against brewer’s yeast, a food attractant highly preferred by several psocid species. Females of L. paeta and L. brunnea were attracted to white light when compared with a blank, but females of L. entomophila were not attracted to white light compared to a blank.
Resumen (Spanish) Los psocidos se han convertido en plagas a nivel mundial de productos almacenados, causando pérdidas económicas significativas. Estos insectos son difíciles de controlar ya que han desarrollado resistencia a insecticidas químicos. Por lo tanto, es importante investigar estrategias alternativas de manejo integrado de plagas (MIP), como el uso de luces atrayentes para monitorear y/o controlar psocidos. La atracción a diferentes luces ha sido estudiada para Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) pero no en otras especies de psocidos. En este estudio, se investigó la respuesta de adultos de tres especies de psocidos (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman, y Liposcelis brunnea Motschulsky, a seis longitudes de onda de diodos emisores de luz (LED) por medio de experimentos de libre selección. Hembras y machos de L. entomophila no fueron atraídos a ninguna de las longitudes de onda de luz evaluadas. Hembras de L. paeta respondieron positivamente a dos longitudes de onda de luz ultravioleta (UV) (351 and 400 nm) y a luz verde (527 nm), mientras que los machos no respondieron a ninguna luz. Hembras y machos de L. brunnea respondieron positivamente a todas las longitudes de onda evaluadas. La mayoría de luces que atrajeron hembras de L. paeta, y hembras y machos de L. brunnea, también fueron preferidas en pruebas de libre escogencia, cuando se les ofreció levadura de cerveza (un atrayente alimenticio altamente preferido por varias especies de psocidos). Las hembras de L. paeta y L. brunnea fueron más atraídas a la luz blanca que al control (sin luz), mientras que las hembras de L. entomophila no respondieron a esta luz. Key words: stored product, monitoring, light preference, behavior, psocids © The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail:
[email protected].
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Journal of Economic Entomology, 2018, Vol. 111, No. 3 Psocids have become important pests of stored grain and grain-based commodities worldwide (Mills et al. 1992, Leong and Ho 1994, Rees 1994, Turner 1994, Phillips and Throne 2010, Throne 2010). Psocids can cause contamination of food commodities (Turner 1994, Athanassiou et al. 2010) and can also significantly reduce the weight and quality of stored grain (McFarlane 1982, Rees and Walker 1990, Kučerová 2002, Gautam et al. 2013). Control is difficult because chemical insecticides used to control other insect pests of stored products are not always effective for control of psocids (Athanassiou et al. 2009). Given the increasing issues with psocids as stored-product pests, it is critical to develop effective integrated pest management (IPM) strategies for their management. A critical part of IPM programs is to have a monitoring program, but monitoring tools for psocids are limited. Psocid species that infest stored products have been shown to respond to volatiles from foods and to different environmental conditions such as temperature, moisture, and light. Opit et al. (2009) studied the population distribution of two psocid species (Psocoptera: Liposcelididae), Liposcelis decolor (Pearman) and Liposcelis entomophila (Enderlein), in steel bins (27 metric tons) of wheat, and they found that populations were more abundant at the center of the bin during the fall and winter suggesting that psocids move toward higher temperatures and grain moistures. Throne and Flinn (2013), using a 60-cm-diameter circular arena, studied the distribution of L. bostrychophila Badonnel, L. entomophila, and Liposcelis paeta Pearman in wheat at different temperature gradients, and they observed that psocids in general move toward the warmest grain in the arena. Using the same circular arena, DiazMontano et al. (2014a) found higher numbers of L. bostrychophila, L. entomophila, and Liposcelis brunnea Motschulsky in the regions with higher grain moisture content. The response of different psocid species [L. bostrychophila, L. brunnea, Liposcelis corrodens (Heymons), L. decolor, L. entomophila, L. paeta, and Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae)] to volatile chemical cues, including food materials, oils, and commercially available kairomones, was studied using a twochoice pitfall trap. Brewer’s yeast, wheat germ, and wheat germ oil elicited the strongest response for the seven psocid species evaluated (Diaz-Montano et al. 2014b, 2015). The response of L. bostrychophila to specific wavelengths of light was studied by Diaz-Montano et al. (2016) using a paired-choice pitfall arena, and psocids responded strongly to wavelengths in the ultraviolet (UV) spectrum. When light was presented against brewer’s yeast, the only wavelength that attracted more psocids than the yeast was the 351 nm UV. Here, we evaluate if UV light, especially 351 nm UV, has the same strong attraction effect for three psocid species not yet studied: L. entomophila, L. paeta, and L. brunnea. We also investigated other wavelengths of light longer than the UV lights to determine if they may trigger stronger responses for these three psocid species.
Materials and Methods Insect Cultures Colonies of the psocid species, L. entomophila, L. paeta, and L. brunnea (voucher specimens No. 182, 207, and 203, respectively, preserved in the Kansas State University Museum of Entomological and Prairie Arthropod Research), are maintained at the U.S. Department of Agriculture, Center for Grain and Animal Health Research in Manhattan, KS. Psocids are reared on a diet of 95% cracked hard red winter wheat (Titricum aestivum L. ‘Santa Fe’), 2% wheat germ (Natural Raw Wheat Germ, Bob’s Red Mill Natural Foods Inc.,
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1477 Milwaukie, OR), 2% brewer’s yeast (MP Biomedicals, Solon, OH), and 1% crisped rice cereal (Rice Krispies, Kellogg’s Company, Battle Creek, MI) at 30°C, 65% RH, and a photoperiod of 16:8 L:D h. In previous studies with adults of several psocid species and different ages (0- to 7-d-old adults, 21- to 28-d-old adults, and mixed-age adults between 0 and 90 d), there were not substantial differences in the behavioral responses regarding of their age (Diaz-Montano et al. 2014b, 2015). For this study, mixed-age adults taken from 3- to 6-moold cultures of L. entomophila, L. paeta, and L. brunnea were used.
Experimental Bioassay The responses of L. entomophila, L. paeta, and L. brunnea females and males to light-emitting diodes (LED) lights were evaluated using the same protocol as in Diaz-Montano et al. (2016). Paired-choice experiments were performed in an arena consisting of a polystyrene Petri dish (14 cm diam. × 1.4 cm height) with two holes (5.0 mm) on juxtaposing sides on the wall of the dish. Through these holes, the LED lights entered the arena via an acrylic tube (1.7 cm long. 5.0 and 3.0 mm outer and inner diameter, respectively) inserted into the wall of Petri dish; and to a hole (5.0 mm diam.) on the upper part of an acrylic vial (2.5 cm diam. × 5.4 cm height). The LED light was inserted to an opposite hole (5.0 mm diam.) in the acrylic vial. The walls outside the vials were blocked with black adhesive tape to prevent light escaping. To avoid psocids leaving the arena and keeping them inside the vials, the inner walls of the Petri dish and the vials were coated with polytetrafluoroethylene (60 wt. % in H2O, Sigma-Aldrich Co., St. Louis, MO). Psocids in the dish responding to a stimulus would enter one of the tubes at the side wall and then fall into the vial. The LEDs were connected through a potentiometer (RV4NAYSD152A, Honeywell International Inc., Morristown, NJ) and powered by a 6 Volt rechargeable battery (SP6-20, SigmasTek, New York, NY). Three experiments (Light vs Blank, Light vs Brewer’s yeast, and Clear White LED vs Blank) were performed using acrylic vials with different treatments, including six LEDs with different wavelengths, blank vials as control, or vials with brewer’s yeast. Brewer’s yeast (1 g) provoked strong responses for several psocid species (DiazMontano et al. 2014b, 2015) and was evaluated in this study. In total, six LEDs were tested: UV 351 nm (L5-1-U5TH15-1, LED Supply, Randolph, VT), UV 380 nm (RL5-UV0230-380, Super Bright LEDs Inc., St. Louis, MO), UV 400 nm (RL5-UV0430-400, Super Bright LEDs Inc.), blue 470 nm (RL5-B2430, Super Bright LEDs Inc.), green 527 nm (RL5-G7032, Super Bright LEDs Inc.), and red 660 nm (RL5-R1330, Super Bright LEDs Inc.). The white light is a spectrum of visible lights with wavelengths ranging from 380 to 750 nm; therefore, the response of L. entomophila, L. paeta, and L. brunnea females to clear white LED (IL151, Microtivity, Hong Kong) was assessed. In total, 15 psocid adults were placed in a Petri dish (3.5 cm diam.) and starved for 24 h. After this period of time, the dish was turned over at the center of the arena. After 10 min, the dish was removed, then psocids can move naturally in the arena. Four hours later, the psocids staying in the arena and the psocids inside the acrylic vials were counted. The experiments were performed under dark conditions in a walk-in environmental chamber (25°C. 65% RH).
Experimental Design and Analysis The experiments with the different treatments (LEDs and/or Brewer’s yeast) were set up in a randomized complete block design with 10 replications. Four replicates of the treatments were set up for a 4 h period at a time until all 10 replications were completed for all the species.
Journal of Economic Entomology, 2018, Vol. 111, No. 3
1478 Table 1. Number (mean ± SE) out of 15 individuals of L. entomophila mixed-age adult females and males that in a paired-choice test selected the treatment vial when given a choice between a specific wavelength LED light and a blank control
Table 2. Number (mean ± SE) out of 15 individuals of L. paeta mixed-age adult females and males that in a paired-choice test selected the treatment vial when given a choice between a specific wavelength LED light and a blank control
LED light
LED light
Females UV—400 nm Blue—470 nm UV—380 nm UV—351 nm Green—527 nm Red—660 nm Males UV—351 nm Blue—470 nm Green—527 nm UV—380 nm UV—400 nm Red—660 nm
Vial 1 (light)
Vial 2 (blank)
6.4 ± 0.6aA 6.4 ± 0.7aA 6.2 ± 0.5aA 5.3 ± 0.6aA 4.6 ± 0.5aB 4.1 ± 0.5aB
6.6 ± 0.7aA 6.3 ± 0.7aA 6.0 ± 0.5aA 7.1 ± 0.8aA 8.1 ± 0.5aA 8.2 ± 0.3aA
5.4 ± 0.6aA 5.0 ± 0.6aA 5.0 ± 0.5aA 5.0 ± 0.4aA 4.3 ± 0.5aA 4.1 ± 0.3aB
6.9 ± 0.4aA 4.1 ± 0.5bA 6.9 ± 0.6aA 4.9 ± 0.5bA 5.6 ± 0.5abA 7.4 ± 0.4aA
Average of 10 replicates. Means followed by different lowercase letters within a column or different uppercase letters within a row are significantly different (P
