Weevil Larvae Research Articles

Sago palm weevil larvae: larval ontogeny and nutritional value assessed from enzymatic activity and in vitro digestibility

Abstract Sago palm weevil larvae (SPWL, Rhynchophorus vulneratus) have potential for use as food and feed. This study aimed to investigate their development, digestive enzyme activity, nutrient values, and digestible protein using an in vitro digestibility technique. Bioassays for SPWL at 21, 28, 35, 42, 49, and 56 days after hatching (DAH) were conducted in a completely randomized design (CRD). Analysis of variance (ANOVA) was performed, and means were compared at using Bonferroni (Dunn) t-tests and orthogonal polynomial contrasts. Trypsin activity significantly increased at 35 DAH (, quadratic effect ), with peak chymotrypsin activity at 28 DAH (). Lipase activity showed both linear and quadratic increases (), and cellulase activity also increased significantly (, linear and quadratic terms ). Meanwhile, the A:T ratio increased significantly (, quadratic effect ) with age-related rises in these digestive enzyme activities. The highest crude protein content in SPWL was observed at 42 DAH (), with peak carbohydrate at 28 DAH (). Phenylalanine and histidine levels increased linearly (), while lysine and total essential amino acids peaked at 42 DAH (, linear and quadratic terms ). Levels of linoleic acid, total polyunsaturated fatty acids, and the n-6:n-3 ratio peaked at 49 DAH (). In vitro protein digestibility assays were performed using enzymes extracted from quails, broilers, Thai native chickens, and ducks. Significant increases in digestibility were attributed to SPWL protein content and age, particularly beyond 42 DAH (, linear and quadratic terms ), except with duck enzymes. In conclusion, these findings suggest that SPWL cultivation, particularly between 42 and 56 DAH, provides a potential alternative protein source with substantial nutritional benefits for poultry feed. The promise of SPWL to contribute to more sustainable and efficient poultry feeding practices is evident, and further in vivo studies are warranted to validate these results.

From organic waste to renewable energy: response surface methodology approach for optimized biodiesel production from palm weevil larvae (Rhynchophorus ferrugineus)

AbstractThis study aimed to improve the production of biodiesel from white palm larvae (WPL) and to evaluate its potential as a feedstock. The larvae were grown using kitchen and palm waste for 21 days, and the crude oil was then extracted. The extracted oil was analyzed for its physicochemical properties and fatty acid composition. The analysis found that the feedstock oil contained a high quantity of monounsaturated fatty acids, indicating its suitability for biodiesel production. To optimize the production process, response surface methodology (RSM) was employed. A central composite design was used to study four operating conditions: temperature, methanol‐to‐oil mole ratio, esterification time, and catalyst loading for esterification, as well as transesterification time and catalyst concentration. The best conditions for esterification were a methanol‐to‐oil ratio of 18:1, a temperature of 70 °C, 120 min of reaction time, and a 4% H2SO4 catalyst. For transesterification, the optimal conditions were a methanol‐to‐oil ratio of 10:1, a temperature of 65 °C, 90 min of reaction time, and a 2% KOH catalyst concentration. The experimental data fit well with models, with significant P‐values and high R2 values. The biodiesel produced under the optimized conditions met the fuel quality standards set by Brazilian, European, and American standards. In conclusion, this study successfully optimized the biodiesel production process from white palm larvae and confirmed its suitability as a feedstock. The feedstock oil had properties that were suitable for biodiesel production, and the optimized conditions resulted in biodiesel that met fuel‐quality standards.

'The Garlic Gambit': an alternative strategy for controlling vine weevil (Otiorhynchus sulcatus F.; Coleoptera: Curculionidae).

Plant protection products derived from plant material are proposed to be a sustainable alternative to conventional synthetic chemical pesticides. This study determines the efficacy of a commercially available bioinsecticide based on garlic (Allium sativum L.; Asparagales: Amaryllidaceae) extract against vine weevil (Otiorhynchus sulcatus F.; Coleoptera: Curculionidae) eggs and larvae in contact, fumigation and a combination of contact and fumigation bioassays under laboratory conditions. Results showed that garlic significantly reduced egg hatch rate compared to the control group when applied as a fumigant. Similarly, the egg hatch rate was reduced compared to the control group when garlic was applied as combined contact and fumigant applications. No effect was observed when the garlic product was applied as a contact application. The bioinsecticide significantly reduced larval survival when either contact or fumigant applications were used. A combined contact and fumigant effect was shown also when vine weevil eggs were exposed to the bioinsecticide for 30 days in plastic containers containing growing media. The number of larvae recovered after this period was significantly reduced compared to the control group. This study demonstrates the potential of garlic-based bioinsecticides, such as Pitcher GR, for vine weevil control. Further studies are, however, needed to determine the efficacy of such bioinsecticides under field conditions and investigate how these products can be most effectively used as a part of a wider vine weevil integrated pest management program.

RNAi-mediated pest control targeting the Troponin I (wupA) gene in sweet potato weevil, Cylas formicarius.

The sweet potato weevil (Cylas formicarius) is a critical pest producing enormous global losses in sweet potato crops. Traditional pest management approaches for sweet potato weevil, primarily using chemical pesticides, causes pollution, food safety issues, and harming natural enemies. While RNA interference (RNAi) is a promising environmentally friendly approach to pest control, its efficacy in controlling the sweet potato weevil has not been extensively studied. In this study, we selected a potential target for controlling C. formicarius, the Troponin I gene (wupA), which is essential for musculature composition and crucial for fundamental life activities. We determined that wupA is abundantly expressed throughout all developmental stages of the sweet potato weevil. We evaluated the efficiency of double-stranded RNAs in silencing the wupA gene via microinjection and oral feeding of sweet potato weevil larvae at different ages. Our findings demonstrate that both approaches significantly reduced the expression of wupA and produced high mortality. Moreover, the 1st instar larvae administered dswupA exhibited significant growth inhibition. We assessed the toxicity of dswupA on the no-target insect silkworm and assessed its safety. Our study indicates that wupA knockdown can inhibit the growth and development of C. formicarius and offer a potential target gene for environmentally friendly control.

Fatty Acid Profile and Thermal Behavior of Fat-Rich Edible Insect Oils Compared to Commonly Consumed Animal and Plant Oils.

This study compared the physicochemical properties of edible insect oils from silkworm (Bombyx mori) pupa (SP), sago palm weevil (Rhynchophorus ferrugineus) larva (PW), and bamboo caterpillar (Omphisa fuscidentalis; BC) to oils from chicken skin (CK), beef back fat (BF), pork back fat (PF), salmon belly (SB), sea bass belly (BB), coconut (C), and peanut (P). The fatty acid profiles and thermal behaviors (crystallization and melting) of the extracted oils were evaluated. PW and BC oils had more saturated fatty acids (SFAs) than CK, PF, SB, BB, and P oils. SP oil had equivalent SFA content to CK and BB oils. Insect oils exhibited similar monounsaturated fatty acid concentrations in all samples, except C oils. PW and BC oils exhibited a higher content of palmitoleic acid than the other oils. SP oils contained polyunsaturated fatty acids similar to those in SB and BB oils, which were higher than those in PW, BC, CK, BF, and PF oils. SP oil also exhibited the highest concentration of α-linolenic acid (C18:3 n-3). Arachidonic acid (0.01-0.02 g/100 g) in all insect oils was lower level compared to CK, BF, PF, SB, and BB oils. SP oil (0.03 g/100 g) exhibited a slightly higher level of eicosapentaenoic acid compared to PW (0.01 g/100 g) and BC (0.01 g/100 g) oils. The insect oils were liquid at ambient temperature, solid below -15°C, and required less energy (△Hm-max) for melting than other samples. This study indicated that insects, particularly SP, could serve as an alternative source of fat to meet its growing demand.

Assessing the toxicity of six insecticides on larvae of red palm weevil under laboratory condition

ObjectiveThe red palm weevil (RPW), is one of the most threatening pests of date palm trees worldwide, causing significant economic losses annually for date palm growers, both globally and in the Middle East, including Saudi Arabia. The primary objective of this research was to assess the insecticide market in Saudi Arabia, test various insecticides claimed to be effective against RPW, and evaluate their efficacy in laboratory settings. This evaluation aims to inform further trials under field conditions. MethodsSix insecticides, including imidacloprid, thiamethoxam, fipronil, emamectin benzoate, deltamethrin, and fenitrothion, were tested to assess their toxicity against red palm weevil 8th instar larvae by diet incorporation under laboratory conditions. The insecticides were applied according to the manufacturer’s recommendations with dosages of 1000 µl, 0.20 µl, 7.5 µl, 0.25 µl, 0.25 µl, and 0.5 µl for imidacloprid, thiamethoxam, fipronil, emamectin benzoate, deltamethrin, and fenitrothion, respectively. ResultsThe results revealed that all tested insecticides exhibited 100 % mortality against 8th instar RPW larvae, with the exception of deltamethrin. However, the time required to achieve this mortality varied. Fenitrothion caused 100 % mortality after 72 h, while thiamethoxam, imidacloprid, and fipronil caused 100 % mortality after 96 h. Emamectin benzoate and deltamethrin resulted in 100 % and 93 % mortality, respectively, after 10 days. The variability in mortality rates may be attributed to differences in their active ingredients, which show varying levels of lethality. In conclusion, all tested insecticides showed effectiveness against RPW larvae and represent viable options for controlling this pest in date palm orchards in Saudi Arabia.

Long-term suppression of turfgrass insect pests with native persistent entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) can control several important turfgrass insect pests including white grubs, weevils, cutworms, and sod webworms. But most of the research has focused on inundative releases in a biopesticide strategy using EPN strains that may have lost some of their ability to persist effectively over years of lab maintenance and / or selection for virulence and efficient mass-production. Our study examined the potential of fresh field isolate mixes of endemic EPNs to provide multi-year suppression of turfgrass insect pests. In early June 2020, we applied isolate mixes from golf courses of the EPNs Steinernema carpocapsae, Heterorhabditis bacteriophora, and their combination to plots straddling fairway and rough on two golf courses in central New Jersey, USA. Populations of EPNs and insect pests were sampled on the fairway and rough side of the plots from just before EPN application until October 2022. EPN populations increased initially in plots treated with the respective species. Steinernema carpocapsae densities stayed high for most of the experiment. Heterorhabditis bacteriophora densities decreased after 6 months and stabilized at lower levels. Several insect pests were reduced across the entire experimental period. In the fairway, the combination treatment reduced annual bluegrass weevil larvae (59 % reduction) and adults (74 %); S. carpocapsae reduced only adults (42 %). White grubs were reduced by H. bacteriophora (67 %) and the combination (63 %). Black turfgrass ataenius adults were reduced in all EPN treatments (43–62 %) in rough and fairway. Sod webworm larvae were reduced by S. carpocapsae in the fairway (75 %) and the rough (100 %) and by H. bacteriophora in the rough (75 %). Cutworm larvae were reduced in the fairway by S. carpocapsae (88 %) and the combination (75 %). Overall, our observations suggest that inoculative applications of fresh field isolate mixes of endemic EPNs may be a feasible approach to long-term suppression of insect pests in turfgrass but may require periodic reapplications.

Overview of the African palm weevil (Rhynchophorus phoenicis) as food and feed – A critical review

Overview of the African palm weevil (Rhynchophorus phoenicis) as food and feed – A critical review

The effect of local habitat and spatial connectivity on urban seed predation.

During the last centuries, the area covered by urban landscapes is increasing all over the world. Urbanization can change local habitats and decrease connectivity among these habitats, with important consequences for species interactions. While several studies have found a major imprint of urbanization on plant-insect interactions, the effects of urbanization on seed predation remain largely unexplored. We investigated the relative impact of sunlight exposure, leaf litter, and spatial connectivity on predation by moth and weevil larvae on acorns of the pedunculate oak across an urban landscape during 2018 and 2020. We also examined whether infestations by moths and weevils were independent of each other. While seed predation varied strongly among trees, seed predation was not related to differences in sunlight exposure, leaf litter, or spatial connectivity. Seed predation by moths and weevils was negatively correlated at the level of individual acorns in 2018, but positively correlated at the acorn and the tree level in 2020. Our study sets the baseline expectation that urban seed predators are unaffected by differences in sunlight exposure, leaf litter, and spatial connectivity. Overall, our findings suggest that the impact of local and spatial factors on insects within an urban context may depend on the species guild. Understanding the impact of local and spatial factors on biodiversity, food web structure, and ecosystem functioning can provide valuable insights for urban planning and management strategies aimed at promoting urban insect diversity.

Evaluation of palm weevil larvae meal (Rhynchophorus phoenicis) as an alternative protein source for pre-pregnancy juvenile tilapia (Oreochromis niloticus) (LINNE, 1758) strain "Brazil" in aquaria

Evaluation of palm weevil larvae meal (Rhynchophorus phoenicis) as an alternative protein source for pre-pregnancy juvenile tilapia (Oreochromis niloticus) (LINNE, 1758) strain "Brazil" in aquaria

Production of Polyhydroxyalkanoates by Bacteria Isolated from the Gut of the Larvae of African Palm Weevil (Rhynchophorus phoenicis)

The indispensability of plastics in everyday life has made the search for environmentally sustainable alternatives to these nonbiodegradable polymers more earnest. Polyhydroxyalkanoates (PHAs) are a class of biodegradable, biocompatible plastics comprising of polyesters of R-hydroxyalkanoic acids. They are accumulated intracellularly as polymeric granules upon cultivating several gram-positive and gram-negative bacteria in nutrient-limiting conditions. Hence, the objective of this paper is to investigate the production of polyhydroxyalkanoates by bacteria isolated from the gut of the larvae of African Palm Weevil (Rhynchophorus phoenicis) using agricultural-waste substrates. Two bacteria isolated from the gut of polystyrene-fed R. phoenicis larvae were utilized for the production of PHA using brewery waste, bean hull, cassava peel and palm pith, as substrates. The bacteria were identified as Lysinibacillus macriodes and Pantoea dispersa. Isolate P. dispersa accumulated PHAs ranging from 0.89- 1.44 g/L from agricultural waste and 4.24 g/L from glucose, equivalent to 30.8%-46.7% and 71.9% yields respectively. L. macrolides, accumulated PHAs ranging from 1.11-1.50 g/L from agricultural waste and 3.89 g/L from glucose equivalent to 40.4%-48.1% and 69.2% yields respectively. The isolates can be desirable candidates for PHAs production under optimized conditions.

On-farm harvest timing effects on alfalfa weevil across the Intermountain West region of the United States.

Alfalfa (Medicago sativa L.) is an economically important commodity in the Intermountain Western United States. A major concern for alfalfa producers in this region is the alfalfa weevil (Hypera postica Gyllenhal). Insecticide resistance development coupled with regulatory changes in pesticide use has resulted in renewed interest by producers in non-chemical control methods such as cultural control. One such cultural control method is early harvest, which consists of producers timing their harvests early in the season to decrease alfalfa weevil damage. This method is thought to be effective by exposing weevil larvae to adverse conditions before significant damage occurs. Still, early harvest can be difficult to employ because recommendations are often vague. To better understand how early harvest impacts both alfalfa weevils and their natural enemies and how producers are using this method across the Intermountain Western United States, we conducted a study in alfalfa production fields in Colorado, Montana, and Wyoming over three growing seasons. We determined that the timing of the initial alfalfa harvest spanned more than 1 month across fields, and alfalfa plant stage at harvest ranged from late vegetative to early bloom. Harvest was more impactful on reducing alfalfa weevil densities the earlier it was implemented. Removing windrows in a timely manner is likely useful to further decrease alfalfa weevil densities. Harvest timing was not associated with parasitism rates of alfalfa weevil, but higher parasitism rates were associated with lower post-harvest alfalfa weevil densities. This work has increased our understanding of early harvest in an on-farm setting and to improve recommendations for producers across the Intermountain Western United States.

Feeding Toxicity of Insecticides against Red Palm Weevil, Rhynchophorus Ferrugineus, (Coleoptera: Dryophthoridae) in a Controlled Environment

Rhynchophorus ferrugineus (Olivier, 1790), often known as the Asian palm weevil or red palm weevil (RPW) (Coleoptera: Curculionidae), had long been considered disruptive to many palm trees (Arecaceae), especially date palms. Observing adults of RPW inside the trunk of palm trees was challenging. Date palm trees provided shelter from bad weather for the larvae that lived and fed within. Finding the red palm weevils required dissecting the palm. Damage could occur to almost every commercially planted date palm variety in the nation, including Aseel, Hillawi, Karbalain, Mozawati, Kechen, and Dhaki. All year round, adult red palm weevils could be found inside palm trees, although they were most active in the summer. The primary method of managing RPW was the frequent use of synthetic pesticides, which were used both preventatively and therapeutically in an effort to lessen RPW damage and spread. In the present study, the soft stem dip method was used to evaluate the toxicity of three different insecticides (clothianidin, trichlorphon (systemic), and fipronil). The results showed that LC50 values with 95% CI (µg/ml) after 72 hours were recorded as 4.096 µg/ml in the case of clothianidin + trichlorfon, representing the highest toxicity. Trichlorphon against 3rd instar larvae of the red palm weevil was more toxic compared to clothianidin and fipronil. The study, therefore, suggested that these insecticides need to be properly included in IPM plans to combat this pest. To test and enhance the efficacy of such pesticides in field settings, more work was necessary.

Rearing of Rhynchophorus phoenicis Fabricius (Coleoptera: Dryophtoridae) last instar larvae on three artificial substrates in Kisangani, Democratic Republic of the Congo

Insects have been a particularly popular resource for human and animal nutrition since the turn of the century, owing mostly to population increase and the ever-increasing need for animal protein. A five (5) months experimental study was carried out at the Yangambi Laboratory of Applied and Functional Entomology in Kisangani to explore a variety of artificial substrates for the mass production of African palm weevil (Rhynchophorus phoenicis) larvae. The larvae were reared in plastic boxes with three types of substrate: T1, based on ripe plantains; T2, based on brewery flour; and T3, based on Makololo flour, which was used as the energy component and made up 60% of the substrate. Palm oilcake and soybean, which accounted for 40% of the substrate, supplied protein. Each treatment was divided into two (2) groups (A and B), this subdivision being based on the presence or absence of soybean meal. 0.8 kg of substrate for each box was given ad libitum every two weeks (14 days). The adults used were captured after trapping in the forest. Broodstocks were randomly assigned to 42 groups (boxes), randomly assigned to six (6) feeding treatments, using a completely randomised design (CRD) with seven (7) replicates. After feeding trial, the results showed that the number and weight of last instar larvae differed between treatments. From the various treatments, an average of 398 last instar larvae LIV, rearing for 32 to 37 days and weighing between 1.56 and 2.22 g were collected. The substrate based on ripe plantain (T1A) produced the highest average number of larvae compared to others (p<0.05), while the substrate based on brew (T2B) produced LIV with higher average weights (p<0.05).

Entomophagy — An evaluation of quality and acceptability of Raphia palm weevil larvae (<i>Rhynchophorus phoenicis</i>) as influenced by thermal processing methods

In this study, the quality and acceptability factor of Raphia palm weevil larvae (Rhynchophorus phoenicis) as influenced by different thermal processing methods were investigated. Raphia palm weevil larvae (n=1000) were randomly distributed into four groups of 250 larvae per group according to a treatment, namely: T1 = boiling (100 °C), T2 = roasting (120 °C) T3 = frying (160 °C) and T4 = oven-drying (180 °C). All treatments lasted 20 minutes. Analyses were carried out to determine the physical, chemical, vitamin and mineral composition, and microbial load. In addition, sensory characteristics were evaluated. Weevil larvae processed by the boiling method had the highest cooking yield (97.59%), water holding capacity (21.78%) and the lowest cooking loss (2.41%). The protein and fat content was higher in weevil larvae processed by frying (37.63% and 17.70%, respectively), while moisture was lowest (18.68%) in oven-dried larvae. The calcium, magnesium and phosphorus content was higher in oven-dried larvae, while there were no significant differences in iron, manganese, zinc and vitamins in the processed larvae irrespective of the methods. Boiled larvae had a higher microbial load, while fried and oven-dried larvae had the lowest microbial load. Fried larvae elicited highest sensory characteristics except tenderness, which was higher in boiled larvae, but fried larvae had higher overall acceptability than those processed by other methods. Therefore, it has been shown that the frying method is an appropriate method of processing Raphia palm weevil larvae for enhanced quality and acceptability.

Variation in substrate nutritional composition and its effects on the growth, development, and nutrient composition of Rhynchophorus phoenicis Fabricius (Coleoptera: Curculionidae)

Abstract Consumption of African Palm Weevil larvae is a potential solution to the escalating need for protein in Ghana. Currently, insect farmers rely heavily on agricultural by-products, for their production. However, the changes in nutritional content of these substrates over the duration of the larval stage is not well understood as its decline could have a negative effect on the larval development. The palm weevil larvae were reared on eleven (11) substrates and the changes in the nutrient content of the substrates over time during the larval rearing duration, and their effect on larval survival, larval duration and larval weight were assessed. The substrates tested included cocoyam cake, spoilt onion, banana corm, spoilt garden eggs, coconut coir, cocoa pod, raphia palm, elephant ear corm, sliced false yam, sugarcane and palm yolk. The substrate samples were collected weekly from the first to the fourth week and analysed for crude fat, crude protein, ash and carbohydrate contents. The nutritional content of all the substrates did not differ in the first week. However, crude protein, crude fat and carbohydrate significantly differed in the second, third, and fourth weeks. Larval survival, larval duration and weight of larvae were significantly affected by the changes in the nutrient content of the substrates in the second, third and fourth weeks. The results showed that elephant ear corm, sliced false yam and palm yolk have necessary nutritional requirements to sustain the larvae during development.

Estimation of predation rate and handling time of boll weevil larvae by Marava arachidis (Dermaptera: Labiidae) using different mathematical methods.

Anthonomus grandis grandis (Coleoptera: Curculionidae) is a pest with a large potential for destruction in cotton crops, causing damage to the cotton reproductive structures. The earwig Marava arachidis (Dermaptera: Labiidae), is an important reference as a predator in several crops and being easy to rear in the laboratory. To analyze the potential biocontrol of M. arachidis of A. grandis grandis larvae, a study of predatory capacity was conducted using a functional response model. A. grandis grandis larvae were exposed to the predator at densities 1, 2, 4, 6, and 8 larvae (= prey/predator / Petri dish), with 30 replications at each density. Contact between the predator and the prey occurred for 24 hours; after this period, the level of predation of M. arachidis was assessed based on the proportion of preyed larvae. The linear logistic regression coefficient was used with a beta-binomial generalized linear model to determine the functional response. The negative signal of the linear coefficient and the goodness-of-fit tests revealed a quadratic or type II functional response, with the number of prey varying from 1.00 larva (density of 1 larva/predator) to 6.50 larvae (density of 8 larvae/predator). Therefore, the results of the present study demonstrate a high predatory capacity of M. arachidis on A. grandis grandis larvae.

Some Physiological Parameters of African Catfish, Clarias gariepinus (Burchell, 1822) Juveniles fed Composite Insect Meal and Phyto-Additives in Cage Culture System

A 70 days experiment was conducted to examine the effect of fishmeal substitution with defatted African palm weevil larvae supplemented with phyto-additives on the growth performance and nutrient utilization of Clarias gariepinus juveniles. Seven diets were formulated containing 45% crude protein: control diet was formulated using fishmeal as the principal protein source, three individual diets were prepared using 17% each of fish meal and defatted African palm weevil larvae supplemented with Telfairia occidentalis, Corchorus olitorious and Cymbopogon citratus as phyto-additives. Another three individual diets were prepared using 17% each of fish meal and defatted African palm weevil larvae supplemented with a mixture of Telfaria occidentalis and Corchorus olitorious, Telfairia occidentalis and Cymbopogon citratus, and Corchorus olitorious and Cymbopogon citratus as phyto-additives making it a total of seven diets. A total of 450 juveniles of African catfish (Clarias gariepinus) was used for the experiment and distributed into 21 baskets embedded in a pond each containing 20(7.50±0.00-7.53±0.00 g/fish) fish. At the end of the feeding trial, the mean weight gain was significantly different (P>0.05) across the fish fed experimental diets. The fish fed with African palm weevil and Telfairia occidentalis as phyto-additives recorded the highest mean weight gain(95.66±25.64) percentage weight gain(91.77±2.14) compared to the other groups. The nutrient utilization indices such as feed conversion ratio, feed efficiency ratio were found to be better in fish fed African palm weevil compared with the CONTROL group. A significantly higher whole-body protein was recorded in fish fed African palm weevil and phyto-additives. From this study, it was concluded that processed African palm weevil larvae with phyto-additives especially Telfairia occidentalis can effectively replace fishmeal in the diet of Clarias gariepinus juveniles.

Identification and biocontrol potential evaluation of a naturally occurring Metarhizium pingshaense isolate infecting tea weevil Myllocerinus aurolineatus Voss (Coleoptera: Curculionidae)

BackgroundTea weevil, Myllocerinus aurolineatus Voss (Coleoptera: Curculionidae), is an important insect pest in Chinese tea plantations. The primary method for controlling tea weevils involves the use chemical pesticides. Hence, there is an urgent need for environmentally friendly control strategies. To screen for potential pathogenic strains useful for the biocontrol of tea weevils, a naturally occurring Metarhizium pingshaense strain was isolated from a field-collected infected tea weevil larva for the first time in China.ResultsMorphological features and molecular characteristics revealed the isolate was an M. pingshaense strain, herein referred to as Ma0628. At 22 °C (tea weevil pupation temperature), the inoculation with M. pingshaense Ma0628 resulted in a corrected cumulative late instar larval mortality rate exceeding 76% at 11 days after the inoculation with the 1 × 108 conidia/ml spore suspension using the immersion or soil-mixing method. Accordingly, the median lethal concentrations were 4.49 × 103 and 3.76 × 102 conidia/ml for the immersion and soil-mixing inoculation methods, respectively. Furthermore, the corrected cumulative adult mortality rate reached 83.33% at 14 days after the inoculation with the 1 × 108 conidia/ml spore suspension.ConclusionThe study results indicate that M. pingshaense strain Ma0628 is an entomopathogenic fungus pathogenic to tea weevil larvae and adults, suggesting it may be a potentially useful biocontrol agent for preventing M. aurolineatus infestations.

Balancing the Growth Performance and Nutritional Value of Edible Farm-Raised Sago Palm Weevil (Rhynchophorus ferregineus) Larvae by Feeding Various Plant Supplemented-Sago Palm Trunk Diets.

Herein, the effect of supplementing ground sago palm trunk (GSPT) with varying concentrations of plant-based ingredients (PIs), including rice bran (RB), soybean meal (SM), and perilla seed (PS), on the nutritional profile of sago palm weevil larvae (SPWL) was investigated. Increased PS intake induced an increase in α-linolenic acid level and a reduction in the n-6/n-3 ratio in SPWL (p < 0.05). The presence of fatty acids in SPWL was determined predominantly by the fatty acid profile in the feed. The activities of Δ5 + Δ6 desaturases and thioesterase were not different among SPWL fed different diets (p < 0.05); however, PI intake resulted in low suppression of fads2 gene expression. RB, SM, and PS at the appropriate concentrations of 17.5%, 8.8%, and 7.0% in GSPT (F3 diet), respectively, boosted both protein quantity and quality of SPWL, as indicated by higher levels of essential amino acids, particularly lysine, than the FAO protein reference. Therefore, incorporating PIs into a regular diet is a viable method for enhancing the nutritional value and sustainability of farm-raised SPWL as a potential alternative source of high-quality lipid and protein.