View Full Version : Impact of bamboo pests on the economy - by INBAR

Mark Meckes
4th December 2004, 03:37 AM
From INBAR website, see ...
THE IMPACT OF BAMBOO PESTS ON THE ECONOMY (http://www.inbar.int/publication/txt/tr13/IMPACT%20OF%20BAMBOO%20PESTS%20ON%20THE%20ECONOMY.htm)
"Insect pests are believed to cause considerable losses to bamboo in natural stands and plantations, and some of these are very obvious. However, owing to the absence of reliable quantitative data, very few assessments have been made on their economic impact.
Most defoliating insects remain low in population and hence, are generally considered pests of minor importance. But some of them show periodic fluctuations in population and epidemics can cause severe or even total defoliation of bamboo stands. Damage caused by leaf feeders reduces the surface area available for photosynthesis, affecting vigour, growth and survival of plants.
A large number of insects, which have highly modified piercing-sucking mouthparts, feed on the sap of leaves,cause injury from egg-laying; injecting toxic compounds into the plant; and transmitting diseases. The results are defoliation, wilting of young shoots and branches, and even death of the culm. During a heavy outbreak of the leaf mites Schizotetranychus spp. in central China in 1989, an average of 85.2 mites per leaf were recorded. The damage resulted in the reduction of new shoot production by 200 kg per hectare in the following year (Yu Huaxing and Shi Jimao 1991). Fei Xueqing et al. (1990) reported the metabolism disorder in Phyllostachys pubescens caused by the bamboo stink bug Hippotiscus dorsalis(Table 3). The aphid Oregama bambusae sucks the sap of growing shoots of bamboos (Singh and Shivaramakrishnan 1976). Heavy infestation * results in the withering of young shoots, which ultimately die.
Compared to defoliators and sap suckers, culm and shoot borers have less effect on the plant physiology. But these can greatly reduce culm and shoot yields and are considered to be of major economic importance. A single larva of a culm borer can destroy a culm. The attack of the borer Cyrtotrachelus spp. is positively correlated with the density of the culms. The hispine beetle Estigmena chinensis is another pest capable of culm destruction. The damage occurs in solid bamboos of smaller thickness and solid parts of thick-walled hollow bamboos. The attack is severe only during the first few months of the culm growth (Beeson 1941; Roonwal 1977). The attack by E. chinensis is also reported to cause bending of bamboos. Singh (1990), in a study on the status of pest problems in India, showed that at least 25% of the standing culms of Dendrocalamus strictus are damaged by stem-boring beetles.

The shoot borer is also regarded a major problem, causing widespread damage to bamboo culms in Bangladesh and Nepal. In Nepal, an estimated 10% of new shoots are damaged every year by shoot borers.

Galls, induced mainly by chalcid wasp species, are common sights on bamboo twigs. Galls cause abnormal growth and shedding of leaves on the affected twigs and thus,probably, affect photosynthesis. The impact of galls on the productivity of bamboo stands, however, remains to be evaluated.

Seed pests, which affect seed production, may have some impact on the establishment of new plantations. Mass build-up of the bug Udonga montana on natural bamboo stands is an occasional occurrence (Singh and Bhandari 1988; Mathew and Sudheendrakumar 1992). The bugs feed on developing bamboo seeds, thereby destroying the means for natural reproduction.

Bamboo under storage, either as culms or as finished products, is very susceptible to damage by insects. Occasionally, subterranean termites cause severe damage. However, the most important pest of bamboo under storage conditions is the ghoon borer or the powder-post beetles Dinoderus spp. Large quantities of culms are destroyed each year by borer insects, although the extent of loss has not yet been assessed. In the storage yards, stacks with immature culms become the starting point of attack and the bamboo is often converted to dust. About 40% of the bamboo stack may be lost within a period of 8-10 months because of ghoon borer (Thapa et al. 1992).

Studies conducted by Nair et al. (1983) showed that the beetle infestation in storage yards is highly unpredictable and the borer incidence is apparently not related to season, but to the quality of bamboo. Earlier, it had been reported that bamboo floated in rivers remain reasonably free of insect attacks.This is probably due to the leaching out of certain soluble substances, such as sugars, favoured as food by the insects.

Mathew and Nair (1990) have reported that finished products made* of reed or bamboo ----such as mats, baskets, curtains, etc. ----are also damaged by the powder-post beetle Dinoderus minutus, but no data is available on the extent of loss suffered.

Cryptotermes dudleyi, an introduced termite species with restricted distribution in some coastal areas of India and Bangladesh, has been reported to destroy bamboo structures in houses. The damage is often serious as the affected material is completely destroyed in a short period of time (Thakur 1988a).

It can be safely assumed that, regardless of their nature, the damage caused by pests to standing bamboos results in reduced productivity of the stands and diminished economic returns. Zhejiang Province in China offers a representative case. The Province has approximately 600 000 ha of bamboo, accounting for about one-sixth of the total area under bamboo in China. Bamboo industry in the Province, which provides more than one-fourth of bamboo timber and edible shoots produced in the country, plays a very important role in improving the living standards of the people.

The Province has some serious problems with insect pests, which strike almost every year. Most important pests are bamboo leaf rollers, puss moths, tussock moths, stink bugs, shoot-boring noctuids and bamboo shoot weevils. The lepidoptorian leaf feeders and the stink bug reach epidemic levels at intervals of 5-8 years, while the pests that affect the shoots remain at a stable population level. Yang Guorong (1991) investigated the impact of some major pests on the productivity of bamboo stands in China, indicating that the economic losses occur mainly from the death of bamboo plants, reduction in the diameter of new culms and lessened yield of edible shoots.
Bamboo shoot weevils and shoot-boring noctuids occur in about 80 000 ha of bamboo plantations in China, and cause the loss of about 285 000 and 8 990 tons of bamboo culms and edible shoots, respectively, every year. On an average, bamboo plantations loose about 10% of their potential turnover because of insect pest infestations.

The account given above indicates the threat some insect pests pose to the bamboo industry. It also indicates that assessments, if and when made, would undoubtedly show substantial economic losses owing to insect pests.