Kamalia priapus (Schitlmeister, 1997)

Danh, Duong Ngoc, Yakovlev, Roman V., Tra, Tran Thi Le, Phuong, Tran Thi, Binh, Vu Duc, Nga, Nguyen Thi Thanh, Hung, Pham Tien, Hoa, Nguyen, Nhung, Nong Phuong, Truong, Pham Xuan & Chi, Nguyen Minh, 2024, Bark-feeding Kamalia priapus (Lepidoptera: Notodontidae) damaging Homalium ceylanicum trees in Vietnam, Ecologica Montenegrina 71, pp. 120-129 : 125-129

Kamalia priapus damage on Homalium ceylanicum trees in plantations and urban areas

Kamalia priapus larvae typically start to emerge around the end of September, identifiable by their small nests appearing on the trunks of H. ceylanicum trees. The larvae made their nests/cocoons by silk and bark mulch, and secured them to tree trunks ( Fig. 3 ). Their nests/cocoons are cleaned and expanded over time until they reach maximum size. Each larva generally occupies its own nest. However, in some cases, two larvae may cohabit in a single nest. Despite this shared environment, both larvae can complete their life cycle and successfully pupated, although the resulting pupae tend to be smaller than the other pupae. Pupa lasted from November 12 to December 3. Eclosion happened from November 24 to December 16 in the afternoon or evening with a 1:1 male-female ratio. Prior to pupation, caterpillar breaks a portion of the upper part of the cocoon to create a circular door, about 10 mm in diameter (as depicted in Figure 3e ), which serves as an exit for the emerging adult. After their emergence, the adults mate and lay eggs within 24–36 hours. Each female is capable of laying 50 to 70 eggs. The eggs were laid sporadically on the bark of the tree. These eggs then hatch after a period of 8–10 days, under average temperature conditions of 24 oC. This study, focusing on H. ceylanicum trees, has recorded that this pest causes damage to these threes once annually. It is suggested that during the remaining time, they may select other host plants for feeding.

The study revealed that the damage incidence (P%) of K. priapus in H. ceylanicum plantations across Quang Binh, Quang Tri, and Thua Thien Hue provinces ranged from 30.6 to 36.5%. The average damage index (DI) in these plantations was 1.01–1.33 ( Table 1). In urban areas within these provinces, the impact of K. priapus was found to be more severe than in plantations. The damage incidence in urban areas of these provinces was higher, with P% = 39.5–51.3%, and damage index was also greater, ranging from 1.50 to 1.68 ( Table 1). Notably, H. ceylanicum trees in Quang Tri province exhibited more severely damage from this pest compared to those in the two neighboring provinces.

Discussion

This study represents the first recorded instance of K. priapus causing damage to H. ceylanicum trees in Vietnam. This pest species has been reported in Cambodia, China, Laos, Myanmar, Thailand and Vietnam ( Sondhi et al. 2006; Schintlmeister 2008; Hideki and Masaru 2016; St Laurent et al. 2023). Additionally, the study has identified H. ceylanicum (family Salicaceae ) as a host plant of this pest. One publication also predicted that the potential host plants of K. priapus are species of the Salicaceae family ( St Laurent et al. 2023), but the host plant species have not been specified. In another study, K. priapus eggs were collected in Vietnam and have been successfully bred on the trunks of Populus and Salix trees in China ( Schintlmeister 2008).

There is no report of insect pests or diseases on H. ceylanicum trees for a long time. However, in recent years, bark-feeding K. priapus has been recorded as a pest that causing damage on H. ceylanicum , both in plantations and urban areas in the central Vietnam. The cause may be due to climate change, the decline of natural forest ecosystems and the increase of H. ceylanicum planting area. This tree species have been used in afforestation and urban planting on a significantly increased scale over the last 10 years ( Binh and Loi 2018; MARD 2021). Several studies have documented rapid population outbreaks of some insect pest species in Vietnam such as Batocera lineolata (Chevrolat, 1852) in Eucalyptus hybrid plantations ( Thu et al. 2021; Quang et al. 2022a), Neurozerra conferta (Walker, 1856) in Melaleuca plantations ( Chi et al. 2022b), and Bacchisa medioviolacea (Breuning, 1965) in Docynia indica plantations ( Quang et al. 2022b). In 2022, a new species, Endoclita vietnamensis ( Buchsbaum & Grehan, 2022) has been recorded as a serious pest in Eucalyptus and Acacia plantations, the damaged plantations were very close to natural forests ( Buchsbaum et al. 2022).

With the increasing area of planted forests and climate change, pests and diseases were always a threat to the forestry ( Ayres and Lombardero 2000; Bosu et al. 2020; Thu et al. 2021). Dozens of pest and disease species have been recorded as dangerous pests and some species have broken out into epidemics in Vietnam ( Thu et al. 2021; Chi et al. 2022a; Chi et al. 2022b; Chi et al. 2023). Bark-feeding pests rarely cause tree death, but they seriously reduce the growth and quality of the trees ( Thu et al. 2021; Quang et al. 2022c). A typical example is bark-feeding Aetherastis grandisalba ( Heppner, 2021) which damages Cinnamomum cassia trees ( Heppner 2021), they weaken the host trees, causing the bark to dry out and lose most of the essential oils in the bark ( Quang et al. 2022c). The bark and stem of H. ceylanicum trees also have chemical components with valuable medicinal properties ( Liu et al. 2013; Acharya et al. 2018). Therefore, the damage of K. priapus not only affects the growth of the trees, leaving scars on the trunks, but can also affect the active ingredients in the bark. To clarify this issue, it is necessary to conduct studies on the chemical composition of H. ceylanicum for both damaged and healthy plants.

In this study, we tested manual control of K. priapus for several attacked H. ceylanicum plants. The method employed the use of small bamboo culms, with diameters ranging from 30 to 45 mm and lengths between 0.5 and 2.0 m, to break the nests and kill the larvae. The treatment was not only straightforward to implement but also highly effective. The treatment resulted in the immediate mortality of all larvae upon application. However, the treatment time was late, when the larvae were at 3 rd to 4 th instars, so reduction of damage symptoms caused by this pest on the trunk of the treated trees was not significant compared to untreated trees. Therefore, to effectively control the pest, it is essential to initiate treatment at the early stage, specially when the larvae have just nested on the trunk and have consumed only portion of the outer bark (not yet eaten all the bark, libe as well as the sapwood). Management of A. grandisalba in C. cassia plantations has also been recommended using manual methods through breaking the nest and killing the eggs, larvae, and pupae ( Binh et al. 2023).

In 2021, the Vietnamese government's strategy for forestry development set a target to reforest an area of about 4000–6000 hectares annually using native tree species ( Vietnam 2021). In which, H. ceylanicum has been selected as one of the main plant species for the reforestation in the central area of Vietnam ( MARD 2014). Future increases in H. ceylanicum plantations will likely provide abundant food sources and accelerate K. priapus population growth. While the manual treatment proved to be relatively simple and effective in controlling this pest, comprehensive research into pest’s life cycles, generational schedules, and population forecasts are essential for more effective management strategies. In this study, it was recorded that K. priapus caused damage to H. ceylanicum trees annualy. Specifically, in the years of 2022 and 2023, the infestations were noted from September to early December. Consequently, further research and monitoring efforts on this pest are necessary to identify their preferred host plants during the remaining periods of the year. Future research directions should focus on determining the biological and ecological characteristics, as well as developing effective management solutions for this pest.

Conclusion

In central Vietnam, Homalium ceylanicum trees in both plantations and urban areas have suffered considerable damage due to the bark-feeding Kamalia priapus . The infestation has significantly impacted the growth and overall quality of the trees.

Acknowledgments

This work was supported by the Ministry of Agricultural and Rural Development of Vietnam under decree number 3710/QĐ-BNN-KHCN dated 15/9/2017. The authors would like to thank the Forest Science Centre for North of Central Vietnam for collecting samples .

Conflict of interest. The authors declare no conflicts of interest.

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Figures

Figure 3. Symptoms of Kamalia priapus attack in Homalium ceylanicum trees: a. nests/cocoons on the stems; b. the cocoon was partially open with a prepupa inside; c. the pupal chamber was opened including the bark with a pupa inside; d, e. damage lesions on stems.