Dealing With Pests and Diseases Affecting Your Bamboo Plant
More than 800 insect species have been recorded to feed on bamboos in the whole world, and most of them are in Asia (Wang et al. 1998). In China, at least 683 species, belonging to ten orders, 75 families, and 363 genera, were reported to attack bamboos (Table 6.1). About 180 insect pests associated with bamboo are discovered, and 80 pests are recorded on bamboos in Japan. As well, not more than ten species that injure bamboos are noted in South Korea, Thailand, and Nepal (Stapleton 1985; Kim and Lee 1986; Choldumrongkul 1994). The high number of bamboo insect pests in Asia may be attributed to the high diversity of bamboo. Forty-four genera (60 % of the world’s total number) of bamboo occur throughout tropical, subtropical, and temperate Asia. This enormous diversity of bamboo species in an area is likely to support an equally diverse Insecta. The lower number of bamboo insects described from non-Asian regions may also be attributed to limited surveying.
Bamboos are subject to injury by various kinds of herbivorous insects. The damages of most insects are not serious and have little effect on the growth of bamboo, though they are feeding on bamboo. About 100 of them can have a serious negative impact on the growth of bamboo. And no more than 100 of them can cause considerable economic losses and even cause quantities of bamboo stands to die when they break out in large areas. Bamboo insect pests can be differentiated as bamboo shoot and culm borers, defoliators, branch and culm pests, bamboo seed pests, and postharvest pests according to the injury period and damage parts of bamboo.
More than 100 insects, including bamboo shoot weevils (Coleoptera: Curculionidae), bamboo shoot wireworms (Coleoptera: Elateridae), shoot-boring noctuids (Lepidoptera: Noctuidae), and shoot flies (Diptera: Anthomyiidae and Tephritidae), are presented to damage bamboo shoot and live culms. Recently, wireworms, shoot weevils, and noctuids occur extensively and have caused eco-nomically severe losses of bamboo production in Asia.
Bamboo Shoot Insects
Bamboo Shoot Wireworms
Wireworms, the common name for soil-dwelling larvae of click beetles (Coleop-tera: Elateridae), occur extensively and have caused economically severe losses of bamboo production in South China in recent years. Larvae injure underground buds and root systems of bamboos, resulting in germination failure, ratooning failure, and losses in stand (Xu and Wang 2004; Zhou et al. 2008; Shu et al. 2012; Fig. 6.1). Figure 6.2 shows that the damage area and density of bamboo shoot wireworms increase rapidly in 8 years and the area where bamboo shoot wireworms are found in 2012 is over ten times than that in 2005. Moreover, the density of wireworm per shoot increases six times
Eight bamboo shoot-boring noctuids (Lepidoptera: Noctuidae) distributed in China, Japan, and India have been reported to feed on various Phyllostachys species (Xu and Wang 2004; Yoshimatsu et al. 2005; Choudhury and Ahktar 2007). Among them, Kumasia kumaso, Apamea apameoides, Oligia vulgaris, and Apamea repetita conjuncta are the most important, which can cause up to 90 % death of new shoots in China (Fig. 6.3; Huang et al. 2009). It is common to find several of these species occurring together in bamboo shoots. The damage is caused by larvae, which bore inside new shoots and cause the death or damage of shoots in most cases. Thus, damaged shoots and culms will have several feeding holes and tunnels.
Bamboo Shoot Weevils
There are about 18 weevil species (Coleoptera: Curculionidae) distributed in China, Bangladesh, Japan, India, Myanmar, Brazil, and Sri Lanka attacking bamboo shoots (Wang et al. 1998; Choudhury and Ahktar 2007). Five species, Cyrtotrachelus buqueti, Cyrtotrachelus longimanus, Otidognathus davidis, Otidognathus sp., and Otidognathus rubriceps, are reported to cause serious damage to bamboos (Fig. 6.5). Both adults and larvae of these weevils feed on shoots, although larvae, which bore holes in bamboo shoots, are responsible for most of the damage. The damage caused by weevils usually results in the death of young shoots or deform and stunt growth of new culms with very closely formed nodes at the feeding site (Fig. 6.6). The larger species, such as Cyrtotrachelus buqueti and C. longimanus, are the most common and destructive on sympodial bamboos, and the small species, for example, Otidognathus davidis, Otidognathus. sp., and O. rubriceps, are found on monopodial bamboos.
Bamboo Leaf DeFloaiters
More than 400 insects are found to eat bamboo leaves, and about 39 species including locusts, leaf rollers, puss moths, tussock moths, and sawflies are reported to cause a huge economic loss in China (Zhang et al. 2002; Xu and Wang 2004).
The locust is one of the most important pest insect groups that affect bamboo. About 40 bamboo locusts have been reported to feed on bamboo leaves in Asian countries. They are classified into a number of genera, of which Hieroglyphus are the most common. Both adults and nymphs feed on bamboo leaves and outbreaks usually cause complete defoliation of bamboo stands (Fig. 6.7). Heavy and repeated defoliation will result in the death of bamboo plants (Anonymous 1960, 1979). In recent years, the damage area by the yellow-spined bamboo locusts, Ceracris kiangsu, increases quickly.
Leaf rollers (Lepidoptera: Pyralidae) belong to the most important groups of leaf feeders on bamboo. More than ten species of bamboo leaf rollers have been reported as attacking various bamboos in Asia (Wang et al. 1998). Among them, four species, Algedonia coclesalis, Crocidophora evenoralis, Demoboty pervulgalis, and Circobotys aurealis, are the most important. Several species often occur together. The damage is caused by larvae, which tie leaves together as leaf cases and feed on the upper tissues of the leaves (Fig. 6.8). Outer leaves of the rolled leaf cases often wither and eventually fall off. Outbreaks are often reported in China, India, Japan, and Korea causing serious defoliation that results in reduced vigor and even the death of culms. Damage is found to be more severe in plantations than in natural stands and individual plantings. Moreover, environment of forest, especially temperature, rainfall, and soil moisture are the key factors that impact the population of bamboo leaf rollers.
Bamboo Branch and Culm Pests
More than 300 species distributed in China, India, and Japan are reported to feed on bamboo branches and culms, and most of them are sapsucking insect pests (Fang and Wang 2000; Xu and Wang 2004). The most important species include stink bugs (Hemiptera: Pentatomidae), coreid bugs (Hemiptera: Coreidae), froghoppers (Homoptera: Cercopidae), aphids (Homoptera: Aphididae), pit scale insects (Homoptera: Asterolecaniidae), and gall-making chalcids (Hymenoptera: Eurytomidae and Ceraphronidae). In many cases, both adults and nymphs of these insects, which have highly modified piercing-sucking mouthparts, feed on the sap of leaves, injure by egg laying, inject toxic compounds into the plant, and transmit diseases. The results are defoliation, wilting of young shoots and branches, and even death of the culm (Fig. 6.9). A heavy outbreak of suckers also can cause huge economic losses.
Post-Harvest Bamboo Pests
Bamboo under storage, either as culms or as finished products, is very susceptible to damage by insects. More than 50 insect pests have been reported to attack felled culms and products made of bamboo timber (Garcia 2005). They include shot-hole borers (Coleoptera: Bostrichidae), powder-post borers (Lyctidae), long-horned beetles (Coleoptera: Cerambycidae), and termites. However, the most important species are mainly from the families of Cerambycidae, Bostrichidae, and Lyctidae. The adults and larvae cause direct damage by boring and continuously feeding inside the culm. This attack may result in severe damage or complete destruction of raw materials or finished bamboo products. In storage yards, stacks with immature culms become the starting point of attack, and the bamboo is often converted to dust.
A total of 440 fungi, three bacteria, two viruses, one phytoplasma, and one bacteria-like organism have been reported as associated with these diseases and disorders (Zhou et al. 2010). In China, a list of bamboo diseases was published including 208 species including 183 species of fungi, 1 bacteria, 2 fastidious prokaryotes, 1 virus, 3 nematodes, and 18 mites (Xu et al. 2006a, b, 2007). In India, a total of 36 species of pathogenic fungus have been reported. Only a few among these diseases are recognized as potentially serious ones, affecting the bamboo industry as well as the rural economy as a whole. Potentially serious diseases of bamboos in Asia include culm blight caused by Sarocladium oryzae in the village groves in Bangladesh and in the coastal areas of Orissa state, India; rot of emerging and growing culms of industrially important bamboo species in India caused by Fusar-ium spp.; witches’ broom incited by Balansia spp. in different species of bamboos in Japan, China, and Taiwan and in reed bamboos in India; little leaf of Dendrocalamus strictus caused by phytoplasma (MLO) in the dry tracts of southern India; culm mosaic caused by bamboo mosaic virus (BaMV) in Taiwan; culm rust caused by Stereostratum corticioides; and top blight of Phyllostachys spp. caused by Ceratosphaeria phyllostachydis in China.
Controlling Bamboo Diseases and Pests
Various control methods including cultural control, biological control, physical control, and chemical control against bamboo pests and diseases have been reported in bamboo plantation area, but the application of chemical pesticides is the most predominant measure used very often. Besides polluting the environment, the excessive use of broad-spectrum insecticide also killed the natural enemies which result in resistance and resurgence of pests. Therefore, IPM program for bamboo is required.
Cultural control is the basis of IPM program for bamboo, and the aims of cultural control are to kill insects directly, create favorable environment for the natural enemies, and improve the insect-resistant ability of bamboos. These cultural con-trols include management of the culm population, such as removing or reducing the culm age population most favored by the pest or by adjusting the culm density to modify the grove’s environment to make it unfavorable for the most prevalent pest. Another method used is to turn over the soil within and around the grove during fall and winter to expose buried pupae to the cold and bird predation. For example, removing weed in Pseudosasa amabilis forest decreases 20 % of the damage rate of shoot-boring noctuids (Huang et al. 2003).
Physical control is a method of getting rid of insects by removing, attacking, or setting up barriers that will prevent further destruction of bamboos. These methods are designed according to common or specific behaviors of target insects. A large number of lepidopterous pests of bamboo have strong phototaxis action toward black light. Light trapping is very effective at controlling moth pest species during their adult stage. Mass trapping in this manner has proven to be effective and successful in control leaf rollers, tussock moths, and bamboo cicadas in China (Zheng et al. 1992; Xu et al. 2001; Liang et al. 2004). Figure 6.11 shows the black fluorescent light used in bamboo forest.
Some bamboo insects are attracted to a particular food and odor, and bait trapping, either through the use of baited traps or poisoned bait, is used to control some bamboo pests. The bamboo shoot fly is baited with fresh bamboo shoot pieces treated with insecticides. The yellow-spined bamboo locust (Ceracris kiangsu) adults are known to visit and feed on human urine, so poison baits with blend of human urine and insecticides were applied in fields to suppress its population. And 507 Ceracris kiangsu adults killed daily per bait containing 30-day-incubated urine with bisultap (Fig. 6.12, Shu et al. 2013).
Physical barriers are effective at controlling insects that need to crawl up the culm to get to their feeding/egg laying sites on the plant. Typically these barriers are a sticky band applied around the base of the culms. It is most effective and successful to set sticky or adhesive barriers around the basal part of culms in early April in the control of the stink bug, Hippotiscus dorsalis, in China.
And it is useful to package shoot with plastic bag to prevent the bamboo shoot weevils laying eggs and feeding on the top of Phyllostachys heterocycla cv. pubescens shoot (Fig. 6.14, Cai et al. 2008).
Of course, the old standby handpicking is useful for controlling the larger, slower-moving bamboo pests in small groves and on specimen plants. The damage caused by bamboo shoot weevils can be significantly reduced by removing adults through handpicking before egg laying. Some insects, which feed in groups at basal portion of culms or shoots or leaves of lower branches, such as aphids and stink bugs, can also be physically removed.
Almost all insect pests are attacked or infested by a number of other living organisms which are their natural enemies. The natural enemies often include parasitoids, predators, pathogens, bacteria, and virus. In natural bamboo stands with high biodiversity, natural enemies play an important role in regulating insect pest populations. More than 50 species of natural enemies are reported to be helpful in the control of bamboo insects (Xu et al. 2003). It is an important strategy for the conservation of natural enemies to create environment conditions favorable to natural enemies, such as retaining the surrounding vegetations and reducing the use of broad-spectrum pesticides. Moreover, Metarhizium anisopliae has been used to kill bamboo shoot wireworms in China. In 30 days, a conidia concentration gradient of 107 conidias/g soil can cause 100 % mortality of bamboo shoot wireworms (Wang et al. 2010, Fig. 6.15). Beauveria bassiana and Bacillus thuringiensis are used widely to control bamboo leaf defoliators, such as tussock moths, puss moths, and leaf rollers, in China (Li 2006; Sun et al. 2007; Wu 2009).
Chemical control is highly effective, easy to use, and low in cost, and a large number of pesticides are available. Pesticides can be applied to standing bamboo plants by dusting, spraying, injecting, and smoking. Systemic pesticides are effec-tive against most insect pests including leaf feeders, sapsuckers (including those with waxy coverings), shoot borers, and gall makers, but can’t be used during the shoot harvesting season. One of the methods used for applying systemic pesticides is culm cavity injection, which is effective and safe to the environment and natural enemies (Zhen et al. 1999; Sun et al. 2005). And many botanical pesticides (rotenone, matrine, nicotine, azadirachtin) and biochemical pesticide (avermectin) have been applied to control bamboo pests. Sex pheromone is very effective and a safe method to control the insect population by mass trapping, to disrupt mating and to prevent further egg laying. And now mass trapping of sex pheromone has been applied to bamboo shoot noctuids in China. Figure 6.16 shows that about 70 moth adults are trapped by the mixture of Z11-16: Ac with Z11-16, OH per trap (Shu et al. unpublished data).