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Palm Pests and Diseases

Palm Pests and Diseases

Palm is crucial in various ecosystems and human activities and is economically significant. However, its growth, vigor, and productivity are declining due to many biotic and abiotic stresses. Among these challenges, pests and diseases significantly threaten palm trees worldwide.

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Several pests have been reported to be serious pests in some regions, including Red Palm Weevil (RPW) in Middle Eastern countries, Black Headed Caterpillar (BHC) in South Asia and Southeast Asia, Coconut Rhinoceros Beetle and other beetles. Furthermore, Some diseases have been identified as serious to the palm crops, such as Lethal Yellowing Disease, Cadang Cadang, and Phytophthora Root Rot.

Introduction
This chapter provides basic information on major diseases and pests of the palm crop. It should serve as a brief reference and a source of information for extension specialists, date growers, and anyone interested in the date palm phytosanitary status.

We are developing an online workshop series to bring together key experts and stakeholders from across Asia [and the Pacific region] to share the latest research and activities to address coconut pests and diseases. The series will be a stand-alone series organized under the ASEAN FAW Action Plan online knowledge and communication hub, [in partnership ]with the Pacific Community (SPC), as well as other key stakeholders working on coconut pest and disease management in the region

Red Palm Weevil

The Red Palm Weevil (RPW), scientifically known as Rhynchophorus ferrugineus, is an invasive insect pest that poses a significant threat to date palms (Phoenix dactylifera) and various other palm species (Manne et al., 2023). Its detrimental impact is widespread in major date-producing areas worldwide, with a particular emphasis on the Middle East and North Africa.
Morphology: Adult Red Palm Weevils are notably large beetles with a total body length, including the rostrum, ranging from 35 to 40mm. These weevils possess an elongated and slender rostrum, often called as a "snout," which the female employs to penetrate palm tissue, creating access wounds for depositing eggs (Nisson, N et al., 2015). The coloration of Rhyncophorus ferrugineus exhibits significant variability, and historically, this has led to the misclassification of color-defined polymorphs (variants) as distinct species. The typical coloration in adult weevils is predominantly reddish-brown (RPW)
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The Life Cycle: The red palm weevil undergoes a complete metamorphosis that consists of Egg, larvae, Pupae, and Imago/adult. Larvae develop within the palm meristem's trunk and apical growth tissues; as they mature, they enlarge and penetrate deep within the upper trunk areas. Mature larvae construct a pupal chamber or cocoon made up of coarse palms. These cocoons are typically found within the damaged tissue of the palm. The male Red Palm Weevil can be differentiated from the female by soft reddish-brown hairs on the dorsal side of its elongated snout. Adult weevils depart from the palm tree upon reaching maturity for new food sources and suitable mates. They have a lifespan of up to four months. (Abdel-Banat&El-Shafie, 2023)
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Economic Damage:  The Early Red Palm Weevil infestations can be difficult to detect in large palms in the landscape unless access to the actively growing portions can be attained. Arborists and individuals working in palm canopies must be vigilant for signs of larval mines and frass (excrement) in leaf bases in the central growing point of the palm to detect signs of early infestation. Larval damage to leaf bases anywhere in the canopy revealed by routine trimming may also be a sign of young Red Palm Weevil larvae feeding. Dieback in the apical (newest, uppermost, or center) leaves in the canopy is a common symptom of larval damage to the meristem tissue and should be investigated for RPW. Frass accumulating at points of injury or the base of offshoots may also appear in infested trees (Nisson, N et al., 2015)
Red Palm Weevil Biocontrol and Management in Terengganu, Malaysia
RPW Control and Management Video series 
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Black Headed Caterpillar

The coconut black-headed caterpillar (BHC), scientifically known as Opisina arenosella Walker (Lepidoptera: Xyloryctidae), is a significant herbivore affecting palm trees traced back to South Asia. In recent decades, O. arenosella has expanded its presence to various Eastern and Southeast Asian countries. Through their feeding activities, the larvae of BHC can induce substantial defoliation and, in some cases, lead to the death of plants, causing direct losses in production (e.g., for coconut) and diminishing the visual appeal of both urban and rural landscapes (Lu et al, 2023)
Morphology: The eggs are oval in outline and possess irregular sculpturing. The larval is characterized by a greenish-brown caterpillar with a dark brown head, prothorax, and reddish mesothorax adorned with brown stripes on its body (Nasser & Abdurahiman, 2001). The insect transforms within a thin, silken cocoon around its body during the pupal phase. The adult moth, measuring 10-15 mm in length and exhibiting a greyish-white in color, presents distinct features between genders. The female moth is identified; the abdomen is stouter and pointed towards the tips. In contrast, the male moth is smaller than the female and displays fringed hairs in the hind wings along the apical and anal margins.
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The Life Cycle: The coconut black-headed caterpillar passes through four consecutive development stages: egg, larva, pupa, and adult. Mating usually occurs at night on the same day of emergence, and the eggs are laid on the following day in irregular groups. The fecundity varies from 59 to 252 eggs, with an average of 137 eggs. The capacity is influenced by climatic and other factors (Nasser & Abdurahiman, 2001). The larva instar 1 to 5 lost for 36 to 54 days. As the larvae enter the pre-pupal stages, their length is reduced, and they acquire a light yellow color. The pre-pupae spins a thick cocoon around its body and enters the pupal stage. The moth emerges in about 10 to 12 days. On the whole, the life cycle duration from the time the eggs are laid until the moth's emergence varies between 49 to 72 days. The adult life span varies from 5 to 13 days. 
Symptoms and Damage: The larvae of the black-headed caterpillar create feeding galleries covered in silk, where they feed on the leaf lamina of palm trees. This process reduces the photosynthetic area of the affected plants. Severe feeding damage has the potential to cause complete defoliation and the eventual death of entire palm trees. O. arenosella larvae feed on the old and new leaves alike, and equally attack buds and immature fruits (Lever, 1969; Manjunath, 1985)
The symptoms of black-headed caterpillar infestations:
  • Coconut trees of all ages are attacked
  • Dried-up patches on leaflets of the lower leaves, only three or four youngest leaves at the center of the grown remain green
  • Galleries of silk and frass are under the side of the leaflets.
  • In case of severe infestation, the whole plantations present a scorched appearance 
     

Webinar Series 2024

The online workshop series will bring together key experts and stakeholders from across Asia [and the Pacific region] to share the latest research and activities to address coconut pests and diseases. The series will be a stand-alone series organised under the ASEAN FAW Action Plan online knowledge and communication hub, [in partnership ]with the Pacific Community (SPC), as well as other key stakeholders working on coconut pest and disease management in the region. [Additionally, it will seek to act as a primer for the upcoming Pacific Conference on Coconut Pests and Diseases Action to be held from 2-5 July 2024, Solomon Islands, to help catalyse and fast-track discussions at the Conference on potential future activities as well as identify opportunities for coordination with potential collaborators across Southeast Asia]. This series [and the conference] are an opportunity for stakeholders in ASEAN and Pacific countries to learn from the work of their Pacific colleagues and vice versa
Session 1
Potential main topic:
  • Introduction to coconut pests and diseases and management
  • Introduction to major initiatives and consortiums
  • Introduction to general toolkits, e.g. CPDT
  • Introduction to Phytosanitary work
Proposed date: March
Session 2
Potential main topic:
Coconut rhinoceros beetle + Coconut Black Headed Caterpillar + Red Palm Weevil + other weevils (e.g. Asiatic Palm Weevil (APW), Black Palm Weevil), Red palm mite

Proposed date: April
Session 3
Potential main topic:
​Diseases – Lethal Yellowing Disease, Cadang Cadang, Phytophthora Root Rot

Proposed date: May
Theme/Notes:
  • A short introduction to biology on each key pest.Monitoring efforts (+spread)
  • Management Strategies, including biocontrol.
  • Trade and Quarantine issues
  • Toolkits, Genomics & Diagnostics

 

Each session must have at least 1 ASEAN-based [and 1 Pacific-based speaker].


References:
Abdel-Banat, B. M. A., & El-Shafie, H. A. F. (2023). Management of the Red Palm Weevil in Date Palm Plantations in Al-Ahsa Oasis of Saudi Arabia. Plant Health Cases, phcs20230001.

Lever, R. J. A. W. (1969). Pests of the coconut palm (No. 7). Food & Agriculture Org. 

Lu, H., Lyu, B., Tang, J., Wu, Q., Wyckhuys, K. A., Le, K. H., ... & Zhang, Q. (2023). Ecology, invasion history and biodiversity-driven management of the coconut black-headed caterpillar Opisina arenosella in Asia. Frontiers in Plant Science, 14, 1116221. 

Manee, M. M., Alqahtani, F. H., Al-Shomrani, B. M., El-Shafie, H. A., & Dias, G. B. (2023). Omics in the Red Palm Weevil Rhynchophorus ferrugineus (Olivier)(Coleoptera: Curculionidae): A Bridge to the Pest. Insects, 14(3), 255.

Manjunath, T. M. (1985). Coconut black-headed caterpillar on banana and coconut. FAO Plant Prot Bull, 33(2), 71-72

Nisson, N. at el., 2015. Invasive species: The red palm weevil. accessed from https://cisr.ucr.edu/invasive-species/red-palm-weevil 

Nasser, M., & Abdurahiman, U. C. (2001). Biological control of the coconut caterpillar Opisina arenosella (Lepidoptera: Xylorictidae): Achievements and prospects. Biocontrol Potential and its Exploitation in Sustainable Agriculture: Volume 2: Insect Pests, 285-305. 
 

Further Resources

This review paper, systematically covers taxonomy, bio-ecology, invasion history, and current management of O. arenosella throughout Asia

This study revealed the potential and prospect of biological control, such as various species of predators, natural enemies, bacteria, fungi, and virus of the coconut caterpillar Opisina arenosella

This paper revealed the potential species of trichogrammatid egg parasitoid by analyzing from Eleven species of trichogrammatids to determine the most favorable candidate for field testing against the coconut leaf-eating caterpillar O. arenosella

This document is prepared by the RPW Expert Team with the support of FAO, to serve as a base for the discussion at the Scientific Consultation and High-Level Meeting on Red Palm Weevil Management,

This paper studied the effectiveness of two strains of M. anisopliae, one indigenous (Met-Gra4) and one foreign (Met-TH), against RPW adults in laboratory bioassays at different humidity levels

External Links

 

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