Dinoderus minutus
(bamboo borer)

D. minutus has a worldwide distribution. It is native to Asia and has been reported in Israel, West Africa, South Africa, North America, Central America, South America, Germany and other European countries. It occurs in almost all the South Asia countries. In China, it can be detected in many cities, except a few cities in the north (Singh, 1974; Sandhu, 1975; Singh and Bhandhari, 1988; Xu Tiansen et al., 1993; Chang Yuzhen and Xue, 1994; Zhang Shimei and Zhao Yongxiang, 1996).

D. minutus is an important borer that attacks felled culms and bamboo timber products. It also damages rice, cassava and sugarcane, and occasionally dried stored products. In China and most south Asian countries, the main host plants are Bambusa bambos, Bambusa breviflora, Bambusa polymorpha, Bambusa textilis, Bambusa vulgaris, Bambusa pervariabilis, Dendrocalamus giganteus, Dendrocalamus hamiltonii, Dendrocalamus strictus, Phyllostachys pubescens [Phyllostachys edulis], Phyllostachys heterocycla, and Phyllostachys heteroclada (Wu et al., 1986; Mathew and Nair, 1990; Koehler, 2003). Moreover, D. minutus is also detected in the wood of some Pinus spp. (Gong Xiuze, 2003.). It can also feed on dry cassava (Mathew and Nair, 1984).

The biology and ecology of D. minutus have been studied by a few entomologists worldwide (Van Dine, 1909; Whitney, 1927; Fullaway, 1930; Zimmerman, 1941; Krauss, 1945; Plank, 1948; Wu et al., 1986). The large amount of information relates to China and South Asia, the main areas of distribution of D. minutus. The life cycle has also been described by Beeson and Bhatia (1937).

D. minutus is polyvoltine. The life cycle is almost uniform irrespective of distribution. There are three generations in China and three to four in South Asia, per year, but the generations are heavily overlapped. In Changsha, Hunan Province, China, there are three generations per year and four to five generations in Guangzhou, China. The adults and larvae can be found at any given time of the year and overwintering is not distinct, although they are less active in cold winters. The first peak of adult emergence is in February, the second is in June, and the third is in October (Van Dine, 1909; Whitney, 1927; Zimmerman, 1941; Liu Jingying, 1956; Liu Yuan and Xu, 1982; Tan Zhongyi, 1984; Wu et al., 1986).

The females begin to deposit eggs individually, in tunnels mined by the adults in mid-April, and oviposition can last 4 months. The peak time for oviposition is in May and June. Temperature and humidity affect ovipositon. A female can lay approximately 20 eggs. The eggs hatch in 5 to 8 days. The larvae bore longitudinally in the culm, which can make a tunnel approximately 15 to 20 mm long and take about 40 days to develop. Pupation occurs in cocoons made at the terminal end of the larval tunnels. After approximately 4 days, the newly developed adult beetles may fly away or may explore other parts of the same bamboo. Some beetle holes are left on the bamboo and a great quantity of tunnels may be present at high densities of D. minutus (Singh, 1974; Sandhu, 1975; Tan Zhongyi, 1984; Wu Jianfen et al., 1986; Singh and Bhandhari, 1988).

Starch, soluble carbohydrates and proteins are nutritionally essential to D. minutus. The incidence of borer attacks has a strong correlation to the richness of nutrients in felled culms, and vary significantly with bamboo species, growing sites, timing and culm age at felling, and the method of transportation and storage. According to Xiao (1992), Bambusa textilis, Bambusa pervariabilis, Phyllostachys heterocycla and Phyllostachys heteroclada are more prone to attack by D. minutus than Pleioblastus amarus and Pseudosasa amabilis. The beetle shows a strong preference for newly-felled culms of some species, whereas others, such as P. amabilis and Pleioblastus spp., are hardly ever attacked. Culms from level sites are more susceptible to attack than those felled from sloping sites. Bamboos growing on plateau are more seriously damaged than those growing in mountains, and those felled in spring and summer are more readily attacked than those felled in autumn and winter. Moreover, culms felled at a young age are more seriously damaged than those grown for 3 to 4 years. In general, culms felled at a young age and growing season, and those growing on shaded, wet sites are more susceptible to attack by D. minutus. Borgemeister et al. (1999) surmised that plant volatiles play an important role in the host-finding and damage behaviour of Dinoderus spp.

D. minutus has a strong ability for starvation tolerance. The adults have a strong ability for pesticide resistance and have no phototactic reaction toward light (Li Yanwen et al., 1996).

Outbreaks of D. minutus in large distribution areas have never been reported. There are records from factories or farms, which store bamboo in Asia (Singh, 1990; Chen Zhilin, 2000; Tan Sujin et al., 2000). The factors responsible for its outbreak are still unclear, so no monitoring system is built at present.

There are a few predators reported to attack D. minutus. Teretrius nigrescens (Rees, 1991), Denops albofasciata (Borgemeister et al., 1999; Gerstmeier et al., 1999) and Tillus notatus are known to prey on the eggs, larvae, pupae and adults (some species just prey on the eggs) in the boring tunnels. A clerid preys on the borer in the tunnels (Liu Yuan and Xu, 1982; Tan Zhongyi, 1984; Wu et al., 1986).

See Chatterjee and Misra (1974) for information on the parasitism of D. minutus.

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.

There are several options for the control of D. minutus, such as phytosanitary methods, biological control, physical methods and chemical control. Selecting the best option depends on a number of factors, such as the severity of infestation, the location of infestation, potential for reinfestation, and cost of treatment (Plank, 1950; Xu Tiansen, 1983; Kumar et al., 1985; Liu Yuan and Xu, 1985; Yang Guarong, 1991; Li Yanwen et al., 1996; Xu Changtang, 2003).

Phytosanitary Measures

D. minutus is a phytosanitary pest in many countries because it can be easily transported between countries in the international trade of bamboo wood and products. Therefore in many open ports, D. minutus is a dangerous pest that should be treated seriously and warrants careful inspections. All imported wood, containers and products are treated by government pest control operators using fumigation and heating, for example, if some symptoms of defoliation are detected (Xu Changtang, 2003).

Biological Control

There are a few predators reported that can be used to control D. minutus (Rees, 1991; Borgemeister et al., 1999). A clerid preys on the borer in boring tunnels (Liu Yuan and Xu, 1982; Tan Zhongyi, 1984; Wu et al., 1986). Spathius bisignatus [Platyspathius dinoderi] and Spathius vulnificus parasitize the eggs of D. minutus. Tillus notatus preys on the larvae, pupae and adults. These natural enemies cannot be relied upon as an effective control method, although they can cause high mortality of the borers. To date (2004), no literature concerning successful examples of biological control methods for the control of D. minutus is available.

Physical Control

After felling, the physical or chemical treatment of culms can significantly improve their resistance to borers as well as to fungi. The traditional and simplest method is to immerse felled culms in water. This method may only be effective in preventing damage from bostrychid beetles. It is also only suitable for those bamboos with a low starch content. This method takes a long time and culms treated in this way tend to blacken (Xu Tiansen, 1983). The heating of culms using fire, boiling water or exposure to direct sunlight in hot summers, can kill borers of D. minutus including the eggs, larvae, pupae and adults. Some advanced microwave and infrared techniques have recently been developed for killing the borers in bamboo culms (Yao Kang et al., 1986).

Chemical Control

Chemical treatment using various insecticides and preservatives has been the most widely used method in controlling post-harvest pests of bamboos, including D. minutus (Xin Jieliu, 1958). Various preservatives have been recommended and used in different countries: 5% water solution of copper-chrome-arsenic composition (CCA); 5-6% water solution of copper-potassium dichromate-borax (CCB); 5-6% water solution of boric acid-borax-sodium pentachlorophenate in 0.8:1:1 or 1:1:5 ratios (BBP); 2-3% water solution of borax: boric acid in a 5:1 ratio; and 10% or 20-25% water solution of copper sulphate. These are mostly applied by soaking under normal temperatures, cold or heated conditions, or under high pressure (Singh and Tewari 1979, 1980, 1981; Nair et al., 1983; Xu Tiansen, 1983; Kumar et al., 1985; Liu Yuan and Xu, 1985; Zhou Fanchun, 1985; Thapa et al., 1992).

Soaking in an aqueous solution of 2% boric acid, 0.5% pentachlorophenate and 5% alcohol can treat bamboo rind and similar semi-finished products. Sulthoni (1990) reported treating dried bamboo splits by immersing them in diesel oil as a simple and cheap method of bamboo preservation. Varma et al. (1988) tested the effectiveness of several commercial formulations of insecticides against D. minutus, and concluded that BHC and the two pyrethroids cypermethrin and permethrin, were effective. Mori and Hideo (1979) reported that the two low-toxicity organophosphorus insecticides prothiophos and phoxim, were more effective than organochlorine ones for the preservation of bamboo materials against fungi and boring pests. Treating culm splits by immersing them in 0.2% phoxim for 3 minutes can result in total mortality of D. minutus in the culm in 2 to 3 days, and can protect the treated split from attack for over 1 year (Zhou Huiming, 1987). Affected bamboo material can also be treated by fumigating in closed chambers or storehouses with sulphuryl fluoride at a rate of 30 to 50 g/m³ of timber for 24 hours (Li Yanwen et al., 1996; Chen Zhilin et al., 1999, 2000).