*3.2.2.2 Canker disease of* E. pellita

Symptoms of canker disease of *E. pellita* varied in each region where it was detected. Canker found in 13- to 11-year-olds (**Figure 7a**–**e**) in Kuching was found some at the base of the stem and others slightly higher up the stem (**Figure 7b**). The cankered stem characteristics are swollen and misshapen and the bark fissured with traces of drying blackish gummosis, but all trees were still alive without any sign of dying. The canker found in 2-year-old PSP trees stand in Bintulu showed characteristic of the whole bark cracking with stems blackened and leaves yellowing and wilting with mortality recorded. Based on the different symptoms observed in PSPs assessed, there were possibilities that more than 1 pathogen caused this disease. A small portion of the bark of one tree in 2-year-old stand in Bintulu region was collected for

*New and Emerging Disease Threats to Forest Plantations in Sarawak Borneo, Malaysia DOI: http://dx.doi.org/10.5772/intechopen.107027*

#### **Figure 6.**

*Root rot disease of* Eucalyptus pellita*; (a) 6-month-old tree with burned like foliar and blackish stem; (b) mycelium on under the bark of the basal stem; (c) Ganoderma root rot fruiting body; (d) red-coloured leathery rhizomorphs with blackish exudates on* E. pellita *root; (e) rotting and fibrous root system.*

examination in the laboratory. We managed to identify the pathogen as Botryosphaeriaceae based on the conidia and the culture characteristic grown on MEA as guided (**Figure 8**) [10, 11].

Based on silviculture regimes were not recorded by the management of the plantation. It was observed weeding was not incorporated into the silviculture regime.

#### *3.2.2.3* Ralstonia solanacearum—*bacterial wilt of Eucalyptus*

The symptoms started with foliar exhibiting chlorotic, yellowish to reddish and gradually spreading to the branches started to wilt and trees will succumb to mortality. The inner stem exhibits vascular discolouration of blackish to brownish and bacterial ooze from the wood when observed using a hand lens (**Figure 9**). The

#### **Figure 7.**

*Canker disease symptoms of* Eucalyptus pellita*; (a–e) stem cankers on 11-year-old* E. pellita *(a) double' canker at basal and middle stem on 11-year-old; (b) close-up showed cracked and fissured bark on 11-year-old; (c) wood under bark seems to be healthy on 11-year-old; (d) canker developed from injury because of self-pruning and on 11-year-old (e) upper stem canker with swollen bark on 11-year-old; (f) huge canker swelling on 2-year-old* E. pellita *at Bintulu region.*

infected trees were chopped and burned. The possible pathogen would be *R. solanacearum* Smith based on disease symptom described [12, 13].

*3.2.3 Disease of* Falcataria molluccana

*3.2.3.1* Uromycladium falcatarium—*gall rust of* F. molluccana

The disease was observed to cause severe damages and mortality to young trees of *F. mollucana,* especially in the Miri region. The disease causes severe damage to all

*New and Emerging Disease Threats to Forest Plantations in Sarawak Borneo, Malaysia DOI: http://dx.doi.org/10.5772/intechopen.107027*

#### **Figure 8.**

*Botryosphaeriaceae pathogen of canker disease of* Eucalyptus pellita*. (a) Culture morphology on MEA; (b) conidia of* Botryosphaeria.

#### **Figure 9.**

*Bacterial wilt sign and symptoms in* Eucalyptus pellita*. (a) Wilting and drying branches symptom on 1-year-old eucalyptus; (b) colour changes turning blackish-brown on eucalyptus 1-year -old stem further symptoms (c) bacterial exudates (ooze) on wood.*

developmental stages of the plant, from seedlings in the nursery to mature trees in the field. Early symptom of infected trees observed was rigid, crooked bending stems, branches or shoot and greenish to reddish necrotic lesion (**Figure 10b**). The symptoms then developed to the development of large chocolate-brown, irregularly shaped, broccoli-like or whip-like galls on the stem and branches (**Figure 10c**).

#### **Figure 10.**

*Gall rust of* F. mollucana*. (a) Whole crown dieback and tree died in 2-year -old tree stands at Miri region; (b; c) the shape of gall in the twig; (d) spores with ridged longitudinal striations typical of* Uromycladium falcatarium *pathogen.*

The disease pathogen was identified as *U. falcatarium* based on the symptoms observed in this study as well as referred [14].
