Adoretus sinicus
(Chinese rose beetle)

Adoretus sinicus is a polyphagous beetle, native to parts of eastern Asia, which has been introduced (probably via the plant trade) widely throughout much of Southeast Asia and many Pacific islands, and has the potential to spread further. It feeds on a broad range of plants and can cause severe damage to crops, ornamental plants and trees in places where it has been introduced. USDA-APHIS (United States Department of Agriculture Animal and Plant Health Inspection Service) included it on the Regulated Plant Pest List (USDA-APHIS, 2000).

According to Mau and Kessing (1991), Adoretus sinicus is originally from Japan and Taiwan, but as a result of introductions it has a widespread distribution throughout much of Southeast Asia and many Pacific Islands (Mau and Kessing, 1991). According to Pemberton (1964), citing Ohaus (1912), before its identification in Hawaii it was known from China, Java and Formosa [Taiwan]. It has also been reported from Kolhapur District, India (Bhawane et al., 2012), and from stored shipping containers in Queensland, Australia (Stanaway et al., 2001).

A. sinicus is of biosecurity concern (as are some other members of the genus) due to its broad host range, its ease of transport with cultivated plants in soil or roots, the severe damage it can cause, and its history of establishment in numerous regions (McQuate and Jameson, 2011b). Its presence in shipping containers in Australia (Stanaway et al., 2001) indicates another possible means of transport. Gregory et al. (2005), in a project at a port in New Jersey, identified it as a potential invader that might arrive in agricultural produce. It is considered to have moderate potential for invasive risk in the mainland USA (McQuate and Jameson, 2011b).

Maki (1916) reported A. sinicus as one of the injurious insects of the mulberry tree (Morus) in Taiwan.  In 1924, Pope (1925) found A. sinicus “(tenuimaculatus, Japanese beetle)” to be the only serious pest of grapes in Hawaii feeding on the foliage.

McQuate and Jameson (2011b) reviewed the plant hosts of adult A. sinicus.  They reported that the species feeds on over 250 species and approximately 56 families of plants according to Habeck (1964), or on over 500 plant species according to Hession et al. (1994). They state, citing Mau and Kessing (1991), Arita et al. (1993) and Zee et al. (2003), that “Host plants include many economically important (crop) plants such as broccoli (Brassica oleracea var. italica Plenck), cabbage (Brassica oleracea var. capitata L.), cacao (Theobroma cacao L.), Chinese broccoli (Brassica oleracea L. var. alboglabra), Chinese cabbage (Brassica rapa L. subsp. chinensis [L.] Hanelt [or Brassica chinensis]), chiso (Perilla frutescens [L.] Britton), corn (Zea mays L.), cotton (Gossypium barbadense L.), cucumber (Cucumis sativus L.), eggplant (Solanum melongena L.), ginger (Zingiber officinale Roscoe), grape (Vitis labrusca Bailey), green beans (Phaseolus vulgaris L.), jack fruit (Artocarpus heterophyllus Lam.), okra (Hibiscus esculentus L. [Abelmoschus esculentus]), peanuts (Arachis hypogaea L.), Oriental persimmon (Diospyros kaki Thunb.), raspberry (Rubus niveus Thunb.), roses (Rosa spp.), salak palm (Salacca zalacca Gaerther), soybean (Glycine max L.), star fruit (Averrhoa carambola L.), strawberry (Fragaria chiloensis [L.] Duch.), sweet potato (Ipomoea batatas [L.]), taro (Colocasia esculenta [L.] Schott) and tea (Camellia sinensis L.)”.

Genetics

Molecular tools are being developed to aid in the identification of adults and larvae of the Adoretini (McQuate and Jameson, 2011b).  DNA in larval-adult species associations within scarab beetle communities from Nepal has been examined.  Larval specimens were associated 86.1% and 92.7% of the time with 19 known adult species based on about 1600 base pairs of mitochondrial COX1 and RRNL, and 700 base pairs of nuclear 28S rRNA. Nine morphotypes in the sample were members of the genus Adoretus, but only two morphotypes could be identified to species (McQuate and Jameson, 2011b, citing Ahrens et al., 2007).

Reproductive Biology

Temperature and substrate quality determine the rate of development from egg to adult.  In the laboratory this takes approximately 15 weeks (Habeck, 1964), while in the field it can be completed in 6-7 weeks (Mau and Kessing, 1991).

Mating begins 30 minutes after sunset (Tsutsumi et al., 1993). Egg clutch size averages 54 eggs. The eggs are laid in the soil within 1.25 to 2.5 cm (Mau and Kessing, 1991) or 4 cm (Habeck, 1964) of the surface. Temperatures of 24.0° C and 28.6° C yield periods of egg development of 12-16 days and 7-13 days, respectively (Habeck, 1964).

A. sinicus has three larval instars.  The first instar lasts 19.6-22.8 days, the second instar lasts 14.5-16.8 days, and the third instar lasts 34.3-44.4 days (Habeck, 1964); according to Mau and Kessing (1991), the larval stage lasts 3-4 weeks in total. Larvae live in rich soil, leaf litter, decaying vegetation, or compost (Mau and Kessing, 1991).

The pupal stage lasts 11-17 days, an average of 14 days (Habeck, 1964).

Longevity

In the laboratory, field-collected adults live 8 weeks (Habeck, 1964).

Activity Patterns

Adult A. sinicus are nocturnal.  During daylight hours they hide under leaves or tree bark or in the soil; they emerge at dusk to feed (Williams, 1931). Thirty minutes after sunset, peak mating and feeding activity occur (Tsutsumi et al., 1993). McQuate (2013), studying A. sinicus activity patterns in the light of the recent demonstration that illumination of plants at dusk has the potential to discourage feeding by adults, found that initiation of beetle colonization of plants occurred on average more than 21 minutes after sunset. Attraction to light at night seems to be considerably less in Adoretus spp. than in other scarab beetle species (G.T. McQuate, Pacific Basin Agricultural Research Center, Hilo, Hawaii, USA, personal communication, 2013).

Nutrition

Larvae live in rich soil, leaf litter, decaying vegetation, or compost (Mau and Kessing, 1991), and feed on humus and detritus rather than living plant tissue according to Williams (1931); on the other hand Bhawane et al. (2012) say that they feed on seedlings.

Adults feed on plant foliage of a wide range of species at night, beginning at dusk (Ebesu, 2003).  They create a lace-like appearance by eating between leaf veins.  In severe cases most leaves are “skeletonized” (Mau and Kessing, 1991).

Smith et al. (2009) state that “within Hawaii, A. sinicus feeds on over 500 plant species including major crops such as taro, corn and beans ([Arita-]Tsutsumi et al., 1994). As adults, A. sinicus beetles are nocturnal feeders and are attracted to ethylene gas released by damaged leaves (Arita et al., 1988; Mau and Kessing, 2002 [1991])”.

Adults prefer leaves and plant species that are high in non-structural carbohydrates (Arita et al., 1993).  They prefer leaves that have been chewed (Pemberton, 1959). High carbohydrate content in snap bean leaves stimulates A. sinicus feeding (Furutani et al., 1993). In paired comparisons between the cultivars Hawaiian Wonder and Green Crop, and Kentucky Wonder and Blue Lake Bush 274 grown in the same environmental conditions, the cultivar of each pair with the greatest carbohydrate concentration was fed on the most.

Tsutsumi et al. (1993) showed that A. sinicus prefers recently matured leaves in the uppermost part of the plant, whereas A. versutus prefers younger leaves in the lower part.

Environmental Requirements

Temperature and substrate quality determine the rate of development from egg to adult.  In the laboratory this takes approximately 15 weeks (Habeck, 1964), while in the field it can be completed in 6-7 weeks (Mau and Kessing, 1991).  Further research is needed to determine the habitat requirements of A. sinicus as they relate to IPM measures, in order to be able to implement more effective control programs. Soil moisture is an environmental requirement for egg development.  The optimal combination of air temperature and relative humidity for each of the life stadia is not known.  Ehehorn (1915) stated that in the summer of 1914 A. tenuimaculatus, the Japanese rose beetle, had been very abundant in the absence of a fungus that kept it in check -- the severe dry weather prevented the growth of the fungus.  This species was later correctly classified as A. sinicus (Muir, 1920).

In Hawaii, several species of natural enemies of A. sinicus were introduced as biological control agents against this or other species, without significantly controlling A. sinicus (Mau and Kessing, 1991; Pemberton, 1964). Campsomeris marginella modesta Smith (Hymenoptera: Scoliidae) and Tiphia segregata Crawford (Hymenoptera: Tiphiidae) were introduced from the Philippines into Hawaii to control A. sinicus and another invasive Rutelinae scarab beetle Anomala orientalis [Blitopertha orientalis] (Muir, 1917, 1919), and 'materially checked' A. sinicus without controlling it fully (Pemberton, 1954).  Tiphia lucida Crawford in Adoretus from the Philippines also failed to control A. sinicus in Hawaii (Pemberton, 1964).  Other natural enemies include frogs and toads, and the fungi Beauveria bassiana and green muscardine fungus (Metarhizium anisopliae) (Fang et al., 1985), and also the tachinid Ocromeigenia ormioides, a scoliid (Tiphia sp.) and a carabid predator, which were introduced to Hawaii from Formosa (now Taiwan) in 1925-6 (Fullaway, 1927).

Adults of species in the genus Adoretus are similar externally; in particular A. sinicus is sometimes confused with A. tenuimaculatus (McQuate and Jameson, 2011b).

McQuate and Jameson (2011b) compared the two species stating, “In males of A. tenuimaculatus, the fifth protarsomere is slightly thickened and armed with an internomedial tooth, whereas in females the fifth protarsomere is gracile and only slightly developed internomedially. This character was not useful, however, in separating males and females of A. sinicus.”

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

The utilization of pesticides, parasitoids, entomopathogens and attractant pheromones has been ineffective in Hawaii (Beardsley, 1993).

Cultural Control and Sanitary Measures

Turning the soil of planted fields might destroy eggs and larvae.

Physical/Mechanical Control

Night-time illumination can be used as a means of reducing A. sinicus population size and defoliation of host plants (McQuate and Jameson, 2011a; Shimabukuro and Tsutsumi, 2008). Use of lighting to discourage colonization and associated defoliation should be initiated at sunset (McQuate, 2013). Other methods proposed for control include tilling soil (both active and dormant beetles are concentrated in the surface soil), nursery irrigation (Fang et al., 1985), and collecting adult beetles by hand at night and putting them in a soapy water solution (G.T. McQuate, Pacific Basin Agricultural Research Center, Hilo, Hawaii, USA, personal communication, 2013).

Movement Control

The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) possess the authority to carry out the mission of protecting American agriculture from plant pests.  The Plant Protection Act of 2000 (PPA) provides the authority to prohibit or restrict imports, exports, or biological control agents, and means of conveyance.  The US Customs and Border Protection (CBP) and PPQ are the regulatory agencies provided with the authority to take regulatory action and enforce restrictions and prohibitions under the Code of Federal Regulations (CFRs). Legislation lists A. sinicus as a pest of concern, and restricts and prohibits the movement of fresh fruits, vegetables, cactus, cut flowers, mango seed, and rice straw from Hawaii to the continental United States, Guam, Puerto Rico, or the U.S. Virgin Islands, and of fresh fruits and vegetables, cotton and cotton covers, sugarcane, cereals, cut flowers, and packing materials from Guam to the United States, Puerto Rico, and the U.S. Virgin Islands (USDA-APHIS-PPQ, 2012).

Biological Control

The green muscardine fungus, Metarhizium anisopliae has been observed to destroy grubs and adults particularly during the wet season (Williams, 1931; Koebele, 1897). M. anisopliae var. majus (Metschnikov) Sorokin [Metarhizium majus] and Beauveria brongniartii (Saccardo) Petch are entomopathogenic fungi that have been tested on larvae of A. sinicus (Koebele, 1897; Williams, 1931; Tsutsumi et al., 1993; Jackson and Klein, 2006). Fang et al. (1985) reported the use of B. bassiana and M. anisopliae.

Entomopathogenic nematodes belonging to the families Steinernematidae and Heterorhabditidae could potentially be utilized to control A. sinicus larvae and adults, and thus minimize chemical control with pesticides (McQuate and Jameson, 2011b).  Hara et al. (1989) tested the nematodes Steinernema carpocapsae (Weiser) and Heterorhabditis sp. MB7 (Maui isolate) on adults and found them to be ineffective.  Tests on larvae also found these nematodes to be ineffective (Tsutsumi et al., 1993).

In Hawaii, several insect natural enemies of A. sinicus were introduced as biological control agents against this or other species, without significantly controlling A. sinicus (Mau and Kessing, 1991; Pemberton, 1964). Campsomeris marginella modesta Smith (Hymenoptera: Scoliidae) and Tiphia segregata Crawford (Hymenoptera: Tiphiidae) were introduced from the Philippines into Hawaii to control A. sinicus and another invasive Rutelinae scarab beetle, Anomala orientalis [Blitopertha orientalis] (Muir, 1917, 1919), and 'materially checked' A. sinicus without controlling it fully (Pemberton, 1954). Tiphia lucida Crawford in Adoretus from the Philippines also failed to control A. sinicus in Hawaii (Pemberton, 1964).  The tachinid Ocromeigenia ormioides, a scoliid (Tiphia sp.) and a carabid predator were also introduced to Hawaii from Formosa (now Taiwan) in 1925-6 (Fullaway, 1927).

Gilmartin (2005) argues that parasitoids should not be used for biological control in Hawaii because of the potential severe effects on non-target species and the risk of introducing exotic parasitoids.

Chemical Control

Suppression of A. sinicus has relied on broad-spectrum organophosphate insecticides (e.g. carbaryl) that often have a negative impact on non-target or beneficial insects (Arita-Tsutsumi et al., 1994; Tsutsumi et al., 1993). An azadirachtin-based antifeedant pesticide and imidicloprid-based systemic pesticides have been tested and found to help in the control of A. sinicus (Arita-Tsutsumi et al., 1995).  Fang et al. (1985) reported chemical control using trichlorfon or cyanthoate.

Gilmartin (2005) argues that broad-spectrum insecticides should not be used for pest control in Hawaii because of the potential severe effects on non-target species.

Repellents and Attractants

Although leaf volatiles have been identified as scarab attractants they are not known as lures because of their volatility.  This makes their application difficult (Leal, 1998).

Hession et al. (1994) proposed the probable existence of a pheromone sex attractant in A. sinicus, which could be used to disrupt mating behaviour.  Synthetic attractants have been developed for A. tessulatus in Australia (Donaldson et al., 1986).

Host Resistance

Lin (1981) carried out field studies in Hawaii in 1976-78 on the resistance of various types of bean crops to arthropod pests. The cowpea (Vigna unguiculata) variety IVU-37 was highly resistant to adults of A. sinicus.  There was a significant negative correlation between leaf toughness and percentage damage by the beetle. Mung-bean (Vigna radiata) varieties that exhibited moderate resistance to other arthropods (Ophiomyia phaseoli and Liriomyza sp.) had relatively high levels of pubescence and antifeedant and low levels of attractant, and the resistance mechanism was thought to be antixenosis.

Monitoring and Surveillance

A. sinicus appears under the category “General Insects” Code 10004 in Appendix E (revised 7/29/2010) of the Aerial Survey Geographic Information System (GIS) Handbook of the USDA Forest Service (USDA Forest Service, 2010), although it has the potential to cause severe damage to plant species including trees.

The status of A. sinicus as an invasive defoliator species should be given more attention in order to determine its ecological role and benefits as a biotic regulating factor in its wide geographic range.  It should be monitored in the long term to better understand the environmental factors that trigger its outbreaks and thus allow managers to put preventative measures into effect ahead of an invasion.

The impact on biodiversity is a broad aspect that should receive more consideration in order to learn how the species alters ecosystems’ nutrient cycles, food and nest supplies, and species composition (both animal and plant).

Another important aspect is the determination of an index of invasiveness based on the similarity of the native habitat of the species to habitats abroad that could potentially be invaded.  International cooperative agreements should be sought between Asian countries and Pacific and Western Hemisphere countries to establish comparative research studies on the habitat requirements of A. sinicus.

Invasiveness concerns make improved taxonomic knowledge of the Adoretus group essential. Additional research in systematics (e.g., molecular phylogenetics and DNA sequencing of an individual species to identify it and tag a taxonomic name to a morphological character) is needed within the genus Adoretus given that it is a group that includes many economically important species.  This novel approach would yield the knowledge for the identification of field samples without the need to analyze DNA from them.  Justified by the scarce workforce of taxonomists in this group, larval and adult identification of A. sinicus and its taxonomic relatives should be broadened (ML Jameson, Department of Biological Sciences, Wichita State University, Wichita, Kansas, USA, personal communication, 2013).

The non-destructive method of sex determination in A. sinicus reported by McQuate and Jameson (2011b) will be instrumental in research aimed at developing improved integrated pest management systems, sex-dependent detection, and monitoring and control methods that make use of pheromones, mating, or reproductive parameters. These tools are of critical importance for managing existing populations as well as future invasions.

Although research in pursuit of an effective attractant has been elusive, there is still a need to discover or develop an attractant to be used in combination with light.  Evidence on the response to light by A. sinicus is conflicting because data has shown attraction and repulsion to light; further research is needed to solve this conflict (GT McQuate, USDA-ARS, U.S. Pacific Basin Agricultural Research Center, Hilo, Hawaii, USA, personal communication, 2013).

Ecological research that is needed includes: 1) climatologic data to correlate A. sinicus abundance to moisture and temperature (e.g. to estimate survival rate in drier soil); 2) biotic (e.g. plant host resistance to the insect) and abiotic (e.g. microclimatic) factors affecting its life cycle, 3) better quantification of the relationship between light intensity and feeding; 4) dispersal pathways other than commerce of potted ornamentals (e.g. wind and oceanic currents); 5) further research on the potential role of natural enemies for different life stages; 6) factors (e.g., predation, drought) limiting population dynamics and insect impact (e.g. the effects of A. sinicus on crop productivity and plant species diversity at the community and ecosystem levels); 7) treatment options and potential effects on target and non-target organisms; 8) the effectiveness of IPM in different geoclimatic regions; and 9) the development of a rapid detection and response protocol including potential control strategies (e.g. biological, microbial and cultural)  to stem an invasion at its onset.

Further research should include the development of Global Information System (GIS) high-resolution satellite imagery to monitor changes in the vegetation due to scarab beetle feeding as an early detection technique.

The way a population is affected after total defoliation of plant hosts by adult beetles should be investigated to learn about the dynamics between invasions.  The dispersal and flight range of the newly hatched individuals facing a lack of vegetation to devour would be interesting to observe.  In addition, destruction of habitat during harvest could force displaced insects to invade new regions. Both facts could point to the next area to be invaded by this pest.

USA: University of Hawaii-Hilo, University of Hawaii at Hilo, 200 W. Kawili St, Hilo, HI 96720-4091, http://www.hilo.hawaii.edu

USA: USDA-ARS Pacific Basin Agricultural Research Center (USDA ARS PBARC), 64 Nowelo St., Hilo, Hawaii 96720, http://www.ars.usda.gov/main/site_main.htm?modecode=53-20-03-00

09/04/2013: Original text by

Alberto García-Moll, consultant, Puerto Rico