Knowledge Level on Bagworm in Oil Palm and its Control Using Integrated Pest Management (IPM) Practices Among Independent Oil Palm Smallholders in Johor

Bagworm (Psychidae) and nettle caterpillars (Limacodidae) are among the major insect pests of oil palm in Malaysia. Bagworm from the species Metisa plana is the most destructive insect pests compared to nettle caterpillar in oil palm plantations. Outbreaks of bagworms were frequently occurred in various areas own by independent oil palm smallholders in Johor. At present, no scientific study has been conducted to indicate the level of knowledge among the independent oil palm smallholders on bagworm and its control, especially using the Integrated Pest Management (IPM) practices. Therefore, this study was conducted to determine knowledge level on bagworm and its control using IPM among 313 independent smallholders in three infestation areas in Johor, which are Mukim Chaah Bahru, Mukim Chaah, Mukim Paloh and Mukim Chamek. Data were collected by interview guided with a questionnaire consisting 23 questions regarding bagworm and its IPM practices. Most of the respondents are more than 51 years (61.1%), with 77.7% males and 22.3% females. They are mostly having primary (47.1%) and secondary (47.5%) school qualifications. This study found that most of the respondents have a basic understanding of bagworm in oil palm and its control measures using IPM practices, but their knowledge is still at a low level. Correlation analysis showed a significant relationship between the level of knowledge on bagworm and its control methods with race, education level and field management experience among the respondents. Therefore, more focus should be given by extension agents to enhance smallholder knowledge on bagworm management, especially in the potential and affected areas in Johor.

Identification of Novel Toxin Genes from the Stinging Nettle Caterpillar Parasa lepida (Cramer, 1799): Insights into the Evolution of Lepidoptera Toxins

Many animal species can produce venom for defense, predation, and competition. The venom usually contains diverse peptide and protein toxins, including neurotoxins, proteolytic enzymes, protease inhibitors, and allergens. Some drugs for cancer, neurological disorders, and analgesics were developed based on animal toxin structures and functions. Several caterpillar species possess venoms that cause varying effects on humans both locally and systemically. However, toxins from only a few species have been investigated, limiting the full understanding of the Lepidoptera toxin diversity and evolution. We used the RNA-seq technique to identify toxin genes from the stinging nettle caterpillar, Parasa lepida (Cramer, 1799). We constructed a transcriptome from caterpillar urticating hairs and reported 34,968 unique transcripts. Using our toxin gene annotation pipeline, we identified 168 candidate toxin genes, including protease inhibitors, proteolytic enzymes, and allergens. The 21 P. lepida novel Knottin-like peptides, which do not show sequence similarity to any known peptide, have predicted 3D structures similar to tarantula, scorpion, and cone snail neurotoxins. We highlighted the importance of convergent evolution in the Lepidoptera toxin evolution and the possible mechanisms. This study opens a new path to understanding the hidden diversity of Lepidoptera toxins, which could be a fruitful source for developing new drugs.

Insecticidal Activity of Bacillus thuringiensis Strains on the Nettle Caterpillar, Euprosterna elaeasa (Lepidoptera: Limacodidae)

In the present work, we evaluated the insecticidal activity of Bacillus thuringiensis (Bt) strains on Euprosterna elaeasa as an alternative for the organophosphate insecticide use in oil palm plantations in the Americas. The toxic effects of four Bt-strains (HD-1 var. kurstaki, SA-12 var. kurstaki, ABTS-1857 var. aizawai, and GC-91 var. aizawai) were evaluated against E. elaeasa caterpillars for toxicity, survival, anti-feeding, and mortality in field-controlled conditions. The Bt-strains, ABTS-1857 var. aizawai (LC50 = 0.84 mg mL−1), GC-91 var. aizawai (LC50 = 1.13 mg mL−1), and HD-1 var. kurstaki (LC50 = 1.25 mg mL−1), were the most toxic to E. elaeasa. The caterpillar survival was 99% without exposure to Bt-strains, and decreased to 52–23% in insects treated with the LC50 and 10–1% in insects exposed to LC90 after 48 h. Furthermore, Bt-strains decreased significantly the consumption of oil palm leaves of E. elaeasa 3 h after exposure. Mortality of E. elaeasa caterpillars caused by Bt-strains had similar lethal effects in the laboratory and in field conditions. Our data suggest that Bt-strains have insecticidal activity against E. elaeasa and, therefore, have potential applications in oil palm pest management schemes.

Evaluation of the effectiveness of insecticide trunk injections for control ofLatoia lepida(Cramer) in the sweet olive treeOsmanthus fragrans

The screening of suitable insecticides is a key factor in successfully applying trunk injection technology to ornamental plants. In this study, six chemical pesticides were selected and injected into the trunks ofOsmanthus fragransto control the nettle caterpillar,Latoia lepida(Lepidoptera: Limacodidae), using a no-pressure injection system. The absorption rate of the insecticides, the leaf loss due to insect damage, and the mortality and frass amount ofL. lepidalarvae were evaluated after 77 and 429 days. The results showed that 4% imidacloprid + carbosulfan and 21% abamectin + imidacloprid + omethoate had the fastest conductivity and were completely absorbed into the trunkswithin14 days; however, the efficiencies of these insecticides in controllingL. lepidawere extremely low. Additionally, the treatment 10% emamectin benzoate + clothianidin and 2.5% emamectin benzoate was almost completely absorbed within 30 days and exhibited a longer duration of insecticide efficiency (>80% mortality) in the upper and lower leaves of the canopy. Treatment with these insecticides also resulted in significantly lower leaf loss and frass amounts. We conclude that emamectin benzoate and emamectin benzoate + clothianidin have a rapid uptake intoO. fragrans, and are effective as insecticides over long durations. Hence, they may be a suitable control option forL. lepidainO. fragransplants.