Short Communication: Incidence of insect pest on planted Shorea macrophylla at reforestation sites in Gunung Apeng National Park, Sarawak, Malaysia

Sidi MB, Wasli ME, Polly E, Jaffar ANNM, Kalu M, Sani H, Nahrawi H, Elias H, Omar D. 2021. Short Communication: Incidence of insect pest on planted Shorea macrophylla at reforestation sites in Gunung Apeng National Park, Sarawak, Malaysia. Biodiversitas 22: 5162-5168. Incidence of insect pest in Shorea macrophylla (de Vriese) P.S. Ashton had critical foliage damage in mono planting technique. The main objectives were to assess the foliage damage intensity of planted S. macrophylla by age stands and type of foliage damage. The insect pest attacks the foliage of S. macrophylla was determined. The study site was located at Gunung Apeng National Park (GANP), Sarawak, Malaysia, with planted S. macrophylla in enrichment planting at different years (planted in 2008, 2009, 2010, and 2011 for age stand 6, 5, 4, and 3, respectively). The results showed that the degree of foliage damage decreases with the age stand of S. macrophylla tree. Therefore, foliage damage was suspected to be caused by insect pests. Among the common foliage damages observed was "hole damage" caused by insect order Lepidoptera. Although foliage damage was significant, the severity of the damage will "heal" as the age stand increases. Further investigation on other possible causes of these pest attacks should be initiated to find solutions that may hasten the growth of planted S. macrophylla for forest restoration.

Silicon fertilisation affects morphological and immune defences of an insect pest and enhances plant compensatory growth

Herbivorous insects have evolved various anti-predator defences, including morphological, behavioural, and immune defences, which can make biocontrol of herbivorous pests challenging. Silicon (Si) accumulation in plants is a potent physical defence against mandibulate insects. However, it remains uncertain how Si affects the anti-predator defences of insect herbivores and plant defences following herbivory. We grew the model grass, Brachypodium distachyon, hydroponically with (+Si) or without (–Si) Si and investigated the plant-mediated effects of Si on the anti-predator defences of the cotton bollworm, Helicoverpa armigera, integrating morphological (i.e. integument resistance and thickness), behavioural, and immune defences. We also examined the effects of Si on plant compensatory growth and leaf trichome production. Larval growth, leaf consumption, and integument resistance were lower when feeding on +Si plants compared to when feeding on –Si plants. Larval integument thickness, defensive behaviours, haemocyte density, and lysozyme-like activity in the haemolymph were unaffected by Si. Larvae fed on +Si plants had higher haemolymph phenoloxidase (PO) and total-PO activities than larvae fed on –Si plants, although this did not enhance the melanisation response of larvae. Furthermore, Si supplies increased plant compensation for herbivory and constitutive trichome production, whereas herbivory induced trichome production only on –Si plants. We provide the first evidence for plant-mediated effects of Si on anti-predator defences of an insect herbivore. We suggest that the lower integument resistance of larvae when feeding on Si-supplemented plants could contribute to their vulnerability to natural enemies and that high PO activity may impose fitness costs (e.g. delayed development).

Optimising Vine Weevil, Otiorhynchus sulcatus F. (Coleoptera: Curculionidae), Monitoring Tool Design

Vine weevil, Otiorhynchus sulcatus F. (Coleoptera: Curculionidae), is an economically important insect pest of horticultural crops. To identify an effective and reliable monitoring system for adult vine weevil, this study investigated the influence of colour, height and entrance position on the efficacy of a model monitoring tool using modified paper cups as refuges. Vine weevil preferences were determined by the number of individuals recorded within a refuge. When provided with a binary choice between black or white refuges, vine weevil adults showed a preference for black refuges. Vine weevils provided with a range of coloured refuges (blue, green, red and yellow) in addition to black and white refuges showed a preference for black and blue over the other colours and white refuges in group choice experiments. Refuge height and entrance position also influenced vine weevil behaviour with individuals exhibiting a preference for taller refuges and those with entrance openings around the refuge base. These results provide insights into refuge selection by adult vine weevils, which can be exploited to improve monitoring tool design. The importance of developing an effective monitoring tool for vine weevil adults as part of an integrated pest management programme is discussed.

Repellency Mechanism of Natural Guar Gum-Based Film Incorporated with Citral against Brown Planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Using of plant essential oil that coevolved as a defense mechanism against agriculture insects is an alternative means of controlling many insect pests. In order to repel brown planthoppers (BPHs), the most notorious rice insect pest, a new film based on guar gum incorporated with citral (GC film) was formulated, which was effective while being environmentally friendly. In this paper, the effect and mechanism of GC film repellency against BPHs were determined. Repellent activity test and olfactory reaction analysis showed that GC film had repellency effect against BPHs, with repellency of 60.00% and 73.93%, respectively. The result of olfactory reaction indicated that GC film repellency against BPHs relied on smell. EPG analysis showed the proportion and mean duration of np waveform were significantly higher than in CK and increased following the treatment concentration, which indicated that GC film affected the recognition of BPHs to rice. Further analysis by RNA sequencing analysis showed a total of 679 genes were significantly upregulated and 284 genes were significantly downregulated in the BPHs fed on the rice sprayed with GC film compared to control. Odorant-binding protein (OBP) gene 797 and gustatory receptor gene (GR)/odorant receptor (OR) gene 13110 showed a significant decrease in differential expression and significant increase in differential expression, respectively. There were 0.66 and 2.55 differential expression multiples between treated BPHs and control, respectively. According to the results described above, we reasoned that GC film repellency against BPHs due to smell, by release of citral, caused the recognition difficulties for BPHs to rice, and OBP gene 797 and GR/OR gene 13110 appeared to be the crucial candidate genes for GC film repellency against BPHs. The present study depicted a clear and consistent repellency effect for GC film against BPHs and preliminarily clarified the mechanism of GC film as a repellent against BPHs, which might offer an alternative approach for control of BPHs in the near future. Our results could also help in the development and improvement of GC films.

An Open-Source Low-Cost Imaging System Plug-In for Pheromone Traps Aiding Remote Insect Pest Population Monitoring in Fruit Crops

This note describes the development of a plug-in imaging system for pheromone delta traps used in pest population monitoring. The plug-in comprises an RGB imaging sensor integrated with a microcontroller unit and associated hardware for optimized power usage and data capture. The plug-in can be attached to the top of a modified delta trap to realize periodic image capture of the trap liner (17.8 cm × 17.8 cm). As configured, the captured images are stored on a microSD card with ~0.01 cm2 pixel−1 spatial resolution. The plug-in hardware is configured to conserve power, as it enters in sleep mode during idle operation. Twenty traps with plug-in units were constructed and evaluated in the 2020 field season for codling moth (Cydia pomonella) population monitoring in a research study. The units reliably captured images at daily interval over the course of two weeks with a 350 mAh DC power source. The captured images provided the temporal population dynamics of codling moths, which would otherwise be achieved through daily manual trap monitoring. The system’s build cost is about $33 per unit, and it has potential for scaling to commercial applications through Internet of Things-enabled technologies integration.

Effectiveness of Cordyceps sp. and Beauveria Bassiana Against Large Cabbage-heart Caterpillar, Crocidolomia Pavonana Fabricius (Lepidoptera: Crambidae)

Crocidolomia pavonana Fabr. (Lepidoptera: Crambidae) is a major pest on various cabbage crops in Indonesia. Various insecticides have been used to control this insect pest including several entomopathogenic fungi, and this cabbage caterpillar has become resistant to various insecticides. In order to develop insecticides from entomopathogenic fungi, species or varieties from natural area such as forest are needed. A bioassays of Cordyceps sp. and Beauveria bassiana has been carried out in the laboratory. Inoculum of Cordyceps sp. obtained from the Dipterocarpaceae forest in South Kalimantan, Indonesia recovered from dead ants by the mycelium of Cordyceps sp. Four concentration of Cordyceps sp. and Beauveria bassiana inoculum and tween80 as a control were tested against 3rd instar larvae of C. pavonana with five replications. Field efficacy trial was carried out in a screen house (8 x 12 M2) using Chinese cabbage plants (Brassica juncea) aged 28 days after sowing, with a spacing of 0.4 M between rows. Three formulation of Cordyceps sp. and tween80 as a control were used with 6 replications. The result of the bioassays in the laboratory showed that Cordyceps sp. with concentration of 1 x 107 conidia mL-1 was able to give 100% mortality od C. pavonana larvae, while B. bassiana with the same concentration caused morality of C. pavonana larvae of 98.33%, although statistically not significantly different. The results of probit analysis also showed that LC90 Cordyceps sp. against cabbage caterpillar larvae was 1.57 x 106 conidia mL-1, while B. bassiana required a concentration of 2.6 x 106 conidia mL-1 to reach the LC90 value. The results of filed trial showed that the formulation of Cordyceps sp. 1 x 107 conidia mL-1 using palm oil cooking oil was able to give an average mortality of 86.7%, and significantly higher (P<0.05) than the other treatment. The results of this study indicate that the inoculum of Cordyceps sp. from Dipterocarpaceae forest is very promising to be developed as an insecticide to control C. pavonana in cabbage

An Analysis of the Possible Migration Routes of Oedaleus decorus asiaticus Bey-Bienko (Orthoptera: Acrididae) from Mongolia to China

Oedaleus decorus asiaticus (Bey-Bienko) is a destructive pest in grasslands and adjacent farmland in northern China, Mongolia, and other countries in Asia. It has been supposed that this insect pest can migrate a long distance and then induce huge damages, however, the migration mechanism is still unrevealed. The current study uses insect light trap data from Yanqing (Beijing), together with regional meteorological data to determine how air flow contributes to the long-distance migration of O. decorus asiaticus. Our results indicate that sinking airflow is the main factor leading to the insects’ forced landing, and the prevailing northwest wind was associated with O. decorus asiaticus taking off in the northwest and moving southward with the airflow from July to September. Meanwhile, the insects have a strong migratory ability, flying along the airflow for several nights. Thus, when the airflow from the northwest met the northward-moving warm current from the southwest, a large number of insects were dropped due to sinking airflow, resulting in a large outbreak. Our simulations suggest that the source of the grasshoppers involved in these outbreaks during early 2000s in northern China probably is in Mongolia, and all evidence indicates that there are two important immigrant routes for O. decorus asiaticus migration from Mongolia to Beijing. These findings improves our understanding of the factors guiding O. decorus asiaticus migration, providing valuable information to reduce outbreaks in China that have origins from outside the country.

Binding Properties of Odorant-Binding Protein 4 of Tirathaba rufivena to Areca catechu Volatiles

Odorant-binding proteins (OBPs) play a key role in the olfactory system and are essential for mating and oviposition host selection. Tirathaba rufivena, a serious lepidopterous insect pest of the palm area in recent years, has threatened cultivations of Areca catechu in Hainan. Female-biased odorant-binding protein 4 of T. rufivena (TrufOBP4) expression was hypothesized to participate in the process of oviposition host recognition and localization. In this study, we cloned and analyzed the cDNA sequence of TrufOBP4. The predicted mature protein TrufOBP4 is a small, soluble, secretory protein and belongs to a classic OBP subfamily. Fluorescence binding assay results showed that TrufOBP4 had high binding abilities with the host plant volatiles, octyl methoxycinnamate, dibutyl phthalate, myristic acid and palmitic acid. These four components tend to dock in the same binding pocket based on the molecular docking result. The interactions and contributions of key amino acid residues were also characterized. This research provides evidence that TrufOBP4 might participate in the chemoreception of volatile compounds from inflorescences of A. catechu and can contribute to the integrated management of T. rufivena.