Cereals and legumes serve as major food to humankind (Deshpande et al., 1991; Lizumi et al., 2014). However, their productivity is severely limited by variety of insect pests (Glen, 2000). Though the application of pesticides has been a popular method to manage insect pests, indirect harm associated with pesticide use on environment and economy has become a measure issue (Pimentel et al., 1992). Recently, significant interest has been generated in environmentally friendly pest control technology that utilizes the responses of insects to visual or olfactory cues(Antignus, 2000; Ben-Yakir et al., 2013). Visual cues are used by the insects to discriminate a suitable host from a non-host (Prokopy & Owens, 1978; Prokopy et al., 1983; Henneman & Papaj, 1999). Several studies have reported use of different colors, shapes, and lights to attract insect pests and have suggested using the cues in insect traps for better result (Prokopy & Ownes, 1978; Vernon & Gillespie, 1990; Mainali & Lim, 2009; Lim & Mainali, 2010).
Traps differ as per the purpose for the trapping, targeted insects and the habitats; traps are used for general survey of insect diversity detection of new invasions of insect pests, delimitation of area of infestation, and for monitoring population levels of established pests (Epsky et al., 2008). Traps are generally deployed either to mass trap the insect pests or to monitor their population. Among the variety of traps, artificial lights traps have been in use since long to trap insects for different purposes (Muirhead-Thompson, 1991). Responses to light are influenced by light intensity and wavelength, and color to that of ambient light (Shimoda & Honda, 2013). Many insects exhibit positive phototaxis which can be used to trap pests, but the effective wavelengths and intensities vary among species (Kinoshita & Arikawa, 2000; Yang et al., 2003).
Recently, use of solar powered light traps is commercially used to trap insect pests of several crops. Solar powered light traps are effective alternative to conventional electric light traps and are advantageous economically and environmentally. In order to amplify the effect of solar powered light traps on catch of insect pests, we aim to evaluate response of major insect pests to different light colors with wavelengths ranging from 350-680 nm installed in solar traps in fields where cereal and leguminous crops were grown.
MATERIALS AND METHODS
Study fields
Three large fields located at National Institute of Crop Science, Rural Development Administration, Miryang, Korea were used for the study. Cereal crops such as sorghum, millet, proso millet and legumes such as soybean and azuki bean were grown in the size 25ha of fields .
Color lamps in the solar light trap
Seven solar light traps (DC 12V, 5W lamp, Eco Solatec Cor., Jinju, Korea) each having different lights: white, red (680 ± 20nm), yellow (600 ± 20nm), green (525 ± 25nm), blue (400 ± 10 nm), black light blue (365 ± 10 nm) or a convertible light (365 to 680 nm) were deployed to each field randomly. The traps were installed 20m apart from each other and were replicated thrice. Lighting was scheduled from 8:00pm to 6:00am from August 1st to October 10th in 2011.
Target insect pests and sampling
Several insect pest species of economic importance belonging to different insect orders and families were targeted and evaluated for their response to solar light traps with different light colors (Table 1). Insect pests captured by each trap were collected in fine meshed bags at every 10 days interval and were brought into the laboratory for identification and count. Data on lepidopterans have been presented species-wise, however, number of bug complex, plant hopper, leaf hoppers, weevils and beetles are presented and analyzed as a group.
Statistical analysis
Mean number of insect pests caught by the solar traps with different color lights on each sampling day were analyzed by repeated measures ANOVA using the GLM procedure (SAS Institute, 2000). Post-hoc comparisons were conducted using Tukey’s test.
RESULTS
Lepidopterans
Color of the light showed significant effect on the capture of S. litura (df = 6, 14, F = 301.36, P < 0.0001), S. exigua (df = 6, 14, F = 173.11, P < 0.0001), and H. assulta (df = 6, 14, F = 64.21, P < 0.0001). Similarly, time had significant effect on the number of S. litura (df = 8, 112, F = 87.4, P < 0.0001), S. exigua (df = 8, 112, F = 150.74, P < 0.0001) and H. assulta (df = 8, 112, F = 142.48, P < 0.0001) captured; interaction between time and light color too had significant effect on catch of S. litura (df = 48, 112, F = 69.56, P < 0.0001), S. exigua (df = 48, 112, F = 122.11, P < 0.0001) and H. assulta (df = 8, 112, F = 74.55, P < 0.0001). While all other light colors had negligible catch of the lepidopterans, black light blue color caught significant number of the moths in all the sampling dates. As observed in black light blue light colored trap, peak population of S. litura (183 ± 27.4 SD), S. exigua (81.66 ± 10.02 SD) and H. assulta (101.33 ± 16.92 SD) were recorded on August 30, August 10 and August 10, respectively (Fig. 1).
Hemipterans
Both light color (df = 6, 14, F = 34.72, P < 0.0001) and time (df = 8, 112, F = 30.67, P < 0.0001) had significant effect on the capture of hemipterans. Also, there was a significant interaction of time and treatment (df = 48, 112, F = 3.96, P < 0.0001). Highest number of the hemipterans were caught by black light blue light trap followed by blue and white lights traps. Black light blue light trap caught maximum number of the bugs on September 9 (19±5.57 SD) (Fig. 2).
Green leaf hopper
Both light color (df = 6, 14, F = 2145.88, P < 0.0001) and time (df = 8, 112, F = 1583.94, P < 0.0001) had significant effect on the capture of Nephotettix cincticeps. A significant interaction of time and treatment was found (df = 48, 112, F = 920.68, P < 0.0001). Similar to other insect species, trap catches of N. cincticeps was highest in the traps with black light blue color. Black light blue light trap captured maximum number N. cincticeps on September 9 (2831±138.90 SD) (Fig. 3).
Plant hoppers
Both light color (df = 6, 14, F = 62.44, P < 0.0001) and time (df = 8, 112, F = 115.31, P < 0.0001) had significant effect on the capture of hemipterans. Also, there was a significant interaction of time and treatment (df = 48, 112, F = 30.12, P < 0.0001). However, unlike other insect species the plant hoppers response to the lights was different. Black blue light had higher number of catches in August, blue caught higher number of the hoppers on September 9, and green and convertible lights had higher catches on September 19 (Fig. 4).
Coleopteraans
Weevils
In case of weevils, both light color (df = 6, 14, F = 55.36, P < 0.0001) and time (df = 8, 112, F = 87.26, P < 0.0001) had significant effect on their capture. Also, there was a significant interaction of time and treatment (df = 48, 112, F = 13.46, P < 0.0001). Black light blue light trap had highest captures followed by the traps with convertible lights (Fig. 5).
Beetles
Both light color (df = 6, 14, F = 35350.4, P < 0.0001) and time (df = 8, 112, F = 2283.55, P < 0.0001) had significant effect on their capture. Also, there was a significant interaction of time and treatment (df = 48, 112, F = 2239.95, P < 0.0001). Black light blue light trap had the highest captures throughout the whole sampling period (Fig. 6).
DISCUSSION
Attraction of insect pests to some of the visual and olfactory cues has been widely incorporated in integrated pest management (IPM) programs, however, insects respond to multiple sensory cues (Ota´lora-Luna & Dickens, 2011). Rather than use of color pigmented surface to attract insect pests, recently, studies on colored light traps and LEDs (Light emitting diodes) have been emphasized (McQuate, 2014). Light traps data aids in sampling populations of pest species, studies of population dynamics, community ecology, and flight behavior (Zalucki, 1991; Hanski & Woiwod, 1993; Yela & Herrera 1993; Gregg et al., 1994; Luttrell et al., 1994). However, enhanced capacity of light traps may serve as a mass trapping tool as well. Results from this study showed that black light blue light trap significantly amount several of insect species of Lepidoptera, Hemiptera except plant hoppers, and Coleoptera. Previous studies have reported that light sources those that emit relatively large amounts of UV radiation having strongest attraction (Aoki & Kuramitsu, 2007; Cowan & Gries, 2009; Matsumoto, 1998). Insects possess conserved visual pigments with maximal spectral absorption between 350 and 550 nm (Briscoe & Chittka, 2001). Insect species are attracted to near UV and UV wavelengths (Kirkpatrick et al., 1970; Cohnstaedt et al., 2008). Black light blue light as in study herein had wavelength lower than 400nm, thus, had highest capture of most of the insect species occurring in cereals and legumes.
Hemipteran showed differential response than other species. While hemipterans, though mostly attracted to black blue light, showed response to wider range of wavelengths, plant hoppers showed varied response to different colors and hence their choice was inconclusive. Such discrepancy was observed probably because those insect species were more active at day time.
All the insect species studied in this experiment showed certain pattern of occurrence. Lepidopterans showed peak population in August; hemipterans significant population occurred until first week of October; green leaf hopper population peaked in September; weevils peaked in August and disappeared after September; beetles population slowly increased up to September and disappeared. The occurrences may be related to crop stage, type and environmental factors. Nevertheless, black light blue light trap seems to be efficient in monitoring various insect species at a time.
Most insect species in this study have been tested for their attraction to semiochemicals. Sex pheromones and aggregation pheromones of these species were used to monitor their population. Then, combination of olfaction with individual color light traps were used to catch the insects of cereal and legeme pests. McQuate (2014) reported enhanced trap effectiveness by combining olfactory and night-visible visual cues against Cylas formicarius (F.).
In conclusion, most of the cereal and legume insect pests are significantly attracted by black light blue light and this particular light color can be used in light traps for monitoring as well as mass trapping of the insect species.
적 요
백색, 적색(680±20nm), 황색(600 ± 20 nm), 녹색(525 ± 25 nm), 청색(400 ± 10 nm), 흑색(365 ± 10 nm) 및 변환(다양한 파장) 램프를 가지는 솔라트랩을 잡곡 및 두류포장에서 설치하여 나 비목, 노린재목 및 딱정벌레목의 주요 해충에 대한 유인효과 를 잡곡 및 두류포장에 설치하여 10일 간격으로 조사하여 평 가하였다. 채집된 충수는 조사시기와 램프의 색깔에 따라 크 게 영향을 받았으며, 조사시기와 램프의 색깔의 상호작용 효 과도 있었다. 암청색램프에서 매미충류를 제외하고 가장 많은 해충이 유인되었다. 따라서 암청색램프는 해충의 대량포획뿐 만아니라 예찰을 위해 효과적으로 사용될 수 있다. 솔라트랩 의 암청색램프와 페로몬의 조합은 잡곡 및 두류 해충의 포획 효과를 증진시킬 수 있어 종합관리를 위한 유망한 수단으로 사용될 수 있을 것으로 여겨진다.
