A long-term survey of Indian meal moths in a dry goods warehouse using monitoring traps with pheromone lures.
The Indian meal moth, Plodia interpunctella (Hubner), is widely considered to be one of the most economically important stored dry food pests. (2) This species is tolerant to a wide range of temperature. Indian meal moths live everywhere in the world, except in the Arctic and Antarctic regions. In temperate regions, it can easily survive over years in food manufacturing plants or warehouses, especially when there are no efficient pest management plans. Larvae or eggs stay dormant during cold months (below 13[degrees]C) and begin development when the temperature rises. (3,4) Female moths lay eggs when the temperature is between 13[degrees]C and 35[degrees]C. (5) In Korea, it was determined that Indian meal moths can produce 5 to 6 generations per year in dry vegetable storage areas. (6) Also, the species uses an extremely wide range of dry products as the food source. Larvae eat almost every type of stored products of both animal and plant origins, with a preference for oil seeds and pet foods. (7) Female moths prefer oil products for their oviposition sites, so the newly hatched larvae can easily find food sources. (8) They are also facultative scavengers as they feed on dead cadavers of their species and other small terrestrial arthropods. (5) Indian meal moths often disperse to the outside and stay on lawns around the buildings, although the food source outside facilities is unknown. (9) Furthermore, they have developed resistance to common pesticides. (7)
Changes in the numbers of Indian meal moths were monitored using glue-board traps with pheromone lures in a US military commissary distribution center in the Republic of Korea (ROK), from July 2007 to February 2010. The survey was conducted to discover the pattern of spatial and seasonal aggregations of Indian meal moths in the warehouse and to evaluate pest controls and warehouse management.
MATERIAL AND METHODS
The Warehouse, Cleaning Practice, and Pest Control
The warehouse is a central distribution center, located in the US Army Garrison Yongsan, ROK. As the facility receives, stores, and distributes food and other products into many US military installations in the ROK, successful pest management is critical to prevent the spread of infested commodities to other commissaries, retail outlets, and warehouses. The warehouse encloses 79,897 [m.sup.2], and the interior height is 6.1 m. Half of the building was constructed in 1962, and the other half added in 1988. The warehouse receives an average of 25 containers per week.
The cleaning schedule in 2007 was monthly floor mopping and weekly sweeping. It increased to weekly floor mopping and daily sweeping in 2008 and 2009, as numerous moths were captured on pheromone traps in 2007. Phosphate pesticides were applied as an immediate remedy when active growths of Indian meal moths were detected in August 2007 (space fogging), June 30, 2008 (residual spraying), and June 13, 2009 (residual spraying). Pest control dates were determined by trapping data, and types of pesticides and treatment methods were advised by the garrison Department of Public Works.
The glue-board type of pheromone trap with attractant for Indian meal moths, 4 related moths (almond moth (Cadra cautella (Walker)), raisin moth (C. figulilella (Gregson)), Mediterranean flour moth (Ephestia kuehniella Zeller), tobacco moth (E. elutella (Hubner))), and the cigarette beetle (Lasioderma serricorne (Fabricius)) was used (IMM+4 and CB lures, STORGARD Traps; Trece Inc, Adair, Oklahoma). Pheromone lures were replaced every 60 days in accordance with the manufacturer's specifications.
Traps were placed on the floor underneath pallet rack frames, as stored product pests tend to move close to surfaces such as floors, walls, or ceilings to find resting areas. (10,11) The traps were placed in storage areas for vulnerable food products such as raisins, corn meal, grain, snacks, cereals, and pet food. (12)
The trapping period began on July 25, 2007, and ended on February 2, 2010. The number of traps and intervals of monitoring varied as the program progressed. Seventeen traps were installed in July 2007, and 13 traps were added near cereal and pet food storage areas in August 2007 (Figure 1). These traps were replaced with 19 traps on August 14, 2007 (after a pest control treatment in the warehouse) (Figure 2). The monitoring interval was as short as 2 days in the beginning (July to September 2007), and extended to 5 to 10 days from October to December 2007. Twenty traps were used from April 23 to December 8, 2008 (Figure 3). For the final phase, 14 traps were placed on April 28, 2009 and removed on February 2, 2010 (Figure 4). Monitoring intervals were extended in 2008 and 2009, as the numbers of collected samples were smaller than in 2007. They were checked every 7 to 10 days during warmer months (April to October) and every 20 to 30 days during cold months (November to February).
Raw data of the numbers of Indian meal moths collected on each date cannot represent the changes of pest population sizes, as they were measured with different numbers of traps and monitoring intervals. Therefore, trap captures were converted to monthly and daily average trap captures. Monthly average trap capture or the number of Indian meal moths collected per trap during a month was calculated using the following formula:
total Indian meal moths collected during a month/ number of traps
Daily average trap capture or the numbers of Indian meal moths collected per day per trap was calculated using the formula:
total Indian meal moths collected between 2 monitoring dates/ number of traps
The data in the following discussion are stated as mean [+ or -] standard error.
In order to detect aggregations of moths, total number of samples collected on each trap were calculated. Also, the data was tested with one-way analysis of variance (ANOVA) using Excel version 2007 (Microsoft Inc, Redmond, WA). The null hypothesis: the trappings were random without being influenced by trap locations. The alternate hypothesis: the trappings were influenced by trap locations.
The traps collected Indian meal moths as well as cigarette beetles and other crawling pests. * Data for cigarette beetles and other arthropods are excluded in this study as they were collected much less frequently.
RESULTS AND COMMENT
Occurrence and Abundance
Indian meal moths were detected in the warehouse from April to November during each year's survey periods, with a tendency of increase toward summer and decrease toward winter (Figures 5, 6, 7). This result is consistent with previous studies for the Indian meal moth life cycle in the ROK. (4,13)
As shown in the Table, monthly average trap captures reached their peaks from June to September. In 2009, a peak was detected at the end of October, when numerous individuals were collected for a short period after replacement of pheromone attractants. As illustrated in Figure 7, the number of collected specimens dropped abruptly afterwards.
Daily average trap captures peaked during August and September 2007 (Figure 5), September 2008 (Figure 6), June and November 2009 (Figure 7). After September, the collections decreased, possibly due to reduced temperature, daylight, and humidity. (7)
The results allowed the prediction of efficient pest control periods in the warehouse. Pesticide applications should be performed from May to June, immediately after active growths are detected in the warehouse. Control by chemicals in July or August should be carefully planned, as they are not likely to kill many larvae that are probably growing inside stored products. Pest control after September is unnecessary and a waste of resources, because the population naturally decreases.
Vulnerable Sites in the Warehouse
As shown in Figures 8, 9, and 10, numbers of trapped specimens were more aggregated in storage areas for pet foods, cereals, crackers, candy bars, and rice. Such items are typically preferred by Indian meal moths as food and oviposition sites. (7,8) Storage for cereals and pet foods are located by the partition wall, which provides shelter to Indian meal moths. (11)
Based on one-way ANOVA test, aggregations were significant in 2007 and 2008, at 95% confidence interval: F=4.32, df=15, P =1.73E-07 for 2007; F=2.94, df=19, P=3.1E-05 for 2008. However, it was insignificant in 2009: F =1.68, df=12, P=.08.
Evaluation of Pest Control Treatments
Changes of trapped Indian meal moths before and after a pest control application were negligible in 2007 (Figure 5), however, they were evident in 2008 and 2009 (Figures 6 and 7). In 2007, daily mean captures continued to increase until September, despite a space fogging with residual pesticide that was applied in August. In 2008, population growths diminished immediately after the pest control treatment in June, but were sporadically active from July through November. In 2009, populations were retarded after the control in June, and there were only a few low peaks afterwards.
The findings discussed above suggest that pest control probably cannot be effective when population growths are vigorous. In 2007, when the daily average trap capture was over 4, the number of moths collected by traps stayed at same level (Figure 5). However, pest controls at the early stage of pest development resulted in reduced pest populations. In 2008 and 2009, when pest control treatments were planned, daily trap capture was approximately 1.50 (consistent with the threshold indicated in Armed Forces Pest Management Board Technical Guide 27 (14)), detected moth numbers decreased after pest control treatments (Figures 6, 7).
Reduction of Pest Populations
In general, detected numbers of Indian meal moths fell over the years of the survey. The average number of Indian meal moths collected per day per trap during the total surveyed period was highest in 2007 (1.64 [+ or -] 0.11). They were reduced by nearly one-half in 2008 (0.71 [+ or -] 0.05) and in 2009 (0.72 [+ or -] 0.09) as shown in the Table. Daily average trap captures often exceeded 4.0 in 2007, but barely reached 2.0 in 2008 and 2009 (Figures 5, 6, 7). The glue board traps used to monitor female moths also actively attracted males. As a result, males collected were not available as mates.
Data on the trapped Indian meal moths were an effective educational tool. Presentation of the data resulted in improvements in warehouse management while the survey was underway. The warehouse cleaning schedule was enhanced in 2008. The loading docks, which are often open during operating hours, were equipped with screens as physical barriers to prevent entrance of pests from the outside.
Fans were operated near the vulnerable commodities during summer months, which possibly lowered temperature, distracted movements of the moths, and dispersed commodity odors. (10)
The following benefits of long-term monitoring were realized:
* More efficient pest control was available with reduced amounts of use, as trappings demonstrated aggregated sites and seasons.
* Monitoring traps raised awareness among employees, which resulted in positive changes in warehouse management.
* Trapping combined with enhanced warehouse management and efficient pest control reduced the risk of Indian meal moths in the warehouse.
I thank William Sames (Armed Forces Pest Management Board), Terry Klein (65th Medical Brigade), Kenneth McPherson (US Environmental Protection Agency), Mack Fudge and Jason Pike (US Army Public Health Command (UASPHC)), Julio Montero (1st Medical Brigade), and Sangho Lee (US Army Medical Research Institute of Chemical Defense) and for their technical assistance in providing critical reviews of this manuscript
I thank Marivic Brown, Brian Kim, and Laura Ray (UASPHC); Nicole Chevalier (Army Medical Department Center & School); Lester Leanna, Tracy Brown, and Thomas Honadel (106th Medical Detachment); David Engelskirchen (DoD Veterinary Service); and Abida Shoyeb (Defense Commissary Agency) for their advice and support for this program. I thank DoD Veterinary Service food inspectors Dong Shin, Kattie Dwyer, Han Pan, and Saudinetra Paynewood for their invaluable help as they conducted monitoring, maintained traps, and communicated with warehouse managers.
I also thank John C. Kirk and Ralph E. Buckner (Defense Commissary Agency), Enrique G. Blanco (Department of Public Works, Yongsan), and Yi Songchu and Kim Chonil (US Army Installation Management CommandKorea) for their support of the suvey effort.
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(2.) Phillips TW, Berberet RC, Cuperus GW. Post harvest integrated pest management. In: Francis FJ, ed. Encyclopedia of Food Science and Technology. 2nd ed. New York, NY: Wiley; 2000; 2690-2701. Available at: storedproducts.okstate.edu/Publications/ EFST061899WP.doc. Accessed January 16, 2013.
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(9.) Campbell JF, Mullen MA. Distribution and dispersal behavior of Trogoderma variabile and Plodia interpunctella outside a food processing plant. J Econ Entomol. 2004; 97:1455-1464.
(10.) Silhacek D, Murphy C, Arbogast RT. Behavior and movements of Indian meal moths during commodity infestation. J Stored Prod Res. 2003; 39:171-184.
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(12.) MIL-STD-904C: Department of Defense Standard Practice-Detection, Identification, and Prevention of Pest Infestation of Subsistence. Washington, DC: US Dept of Defense; July 15, 2010:5.
(13.) Na JH, Ryoo MI. Effects of temperature on the life history of Indian meal moth (Lepidoptera: Pyralidae) on Brown rice [In Korean with English abstract]. Korean Journal of Applied Entomology. 1998; 37:143-149.
(14.) Armed Forces Pest Management Board Technical Guide 27. Stored-Product Pest Monitoring Methods. Washington, DC: Armed Forces Pest Management Board; 2005. Available at: http://www.afpmb. org/sites/default/files/pubs/techguides/tg27.pdf. Accessed January 9, 2013.
* Most common: centipedes (Chilipoda spp) and roll bugs (Armadillididae spp). However, at most one or 2 crawling pests per trap were captured in a year. In total, less than 15 crawling pests captured in all the warehouse traps in any year of the survey.
Choe Hyon Chong, PhD
Dr Choe is an entomologist with the 106th Medical Detachment (Veterinary Service Support), US Forces Korea.
Number of Indian meal moths captured by month. Occurrences that disturbed the collection process are explained in footnotes. Year Month Surveyed Days: Period Total Trap Capture (No. (Average Collection Traps) Per Trap Per Day, Mean [+ or -] SE) 2007 Jul 15a: 25 Jul-10 Aug 817 Aug 15b: 14-31 Aug 652 Sep 28a: 5-28 Sep 1,003 Oct 22: 1-22 Oct 353 Nov 34: 23 Oct-26 Nov 98 Dec 22a: 5-27 Dec 0 Total 136 2,923 (1.64 [+ or -] 0.11) 2008 Apr 10a: 20-30 Apr 7 May 28: 1-28 May 218 Jun 26b: 29 May-24 Jun 293 Jul 25: 5-30 Jul 534 Aug 27: 1 -27 Aug 521 Sep 30: 28 Aug-26 Sep 896 Oct 14a,d: 27 Sep-10 Oct 194 Nov 35: 22 Oct-27 Nov 896 Dec 9a: 1-9 Dec 14 Total 204 3,573 (0.71 [+ or -] 0.05) 2009 May 30a: 28 Apr-28 May 368 Jun 9b: 29 May-17 Jun 252 Jul 20: 8 Jul-28 Jul 267 Aug, Sep 56c: 29 Jul-30 Sep 573 Oct 20d: 9-20 Oct 243 Nov 40c: 21 Oct-10 Dec 20 Dec, Jan, Feb 53c: 11 Dec-2 Feb 2 Total 228 1,393 (0.72 [+ or -] 0.09) Notes: (a.) Placement and/or replacement of traps (b.) Pest control treatment (c.) Lack of manpower (d.) Shortage of traps
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|Author:||Chong, Choe Hyon|
|Publication:||U.S. Army Medical Department Journal|
|Date:||Apr 1, 2013|
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