First report on the enzymatic and immune response of Metarhizium majus bag formulated conidia against Spodoptera frugiperda: An ecofriendly microbial insecticide

Entomopathogenic fungi from microbial sources are a powerful tool for combating insecticide resistance in insect pests. The purpose of the current study was to isolate, identify, and evaluate bag-formulated entomopathogenic fungal conidial virulence against insect pests. We further investigated the enzymatic responses induced by the entomopathogenic fungi as well as the effect on a non-target species. Entomopathogenic fungi were isolated from the Palamalai Hills, India, using the insect bait method, and the Metarhizium majus (MK418990.1) entomopathogen was identified using biotechnological techniques (genomic DNA isolation and 18S rDNA amplification). Bag-formulated fungal conidial efficacy (2.5 × 103, 2.5 × 104, 2.5 × 105, 2.5 × 106, and 2.5 × 107 conidia/ml) was evaluated against third instar larvae of Spodoptera frugiperda at 3, 6, 9, and 12 days of treatment, and acid and alkaline phosphatases, catalase, and superoxide dismutase enzymatic responses were evaluated at 3 days post-treatment. After 12 days of treatment, non-target assays on the earthworm Eudrilus eugeniae were performed using an artificial soil assay. Results of the bag formulated fungal conidial treatment showed that S. frugiperda had high susceptibility rates at higher concentrations (2.5 × 107 conidia/ml) of M. majus. Lower concentration of 2.5 × 103 conidia/ml caused 68.6% mortality, while 2.5 × 107 conidia/ml caused 100% mortality at 9 days post treatment. Investigation into enzymatic responses revealed that at 3 days post M. majus conidia exposure (2.5 × 103 conidia/ml), insect enzyme levels had significantly changed, with acid and alkaline phosphatases, and catalase enzymes significantly reduced and superoxide dismutase enzymes significantly raised relative to the control. After 12 days of treatment, no sublethal effects of M. majus conidia were observed on E. eugeniae, with no observed damage to gut tissues including lumen and epithelial cells, the nucleus, setae, coelom, mitochondria, and muscles. This study offers support for the use of fungal conidia in the target-specific control of insect pests

Population dynamics of Aphis craccivora (Koch) and its natural enemies on bean crop in relation to weather parameters in Vadodara, Gujarat, India

The studies on the population dynamics of Aphis craccivora (Koch) were conducted during 2008- 2011. This pest is a serious pest in the agricultural fields of Vadodara, India. The results showed that the aphid population was higher in the month of September to January on bean crop. The maximum population of Aphis craccivora (Koch) was seen in the month of January to March. The correlation of the aphid population was done with abiotic and biotic factors. The aphid population was showing positive correlation with high temperature and the population of predators and other associated insect was showing negative correlation with minimum temperature, relative humidity and rainfall. Hence the information contained in this paper lead to the identification of the proper integrated pest management (IPM) practises for Aphis craccivora (Koch) management

Repellence property of traditional plant leaf extracts against Aphis gossypii Glover and Phenacoccus solenopsis Tinsley

Aphid, Aphis gossypii Glover (Hemiptera: Aphididae) and mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) are major polyphagous pests in Vadodara agricultural fields. To control these sap sucking insect pests; farmers are using broad spectrum insecticides which are toxic to non target insects. Therefore, the objective of this study is to control these pests by using biorational control methods. Hence, laboratory assays were carried out to evaluate the repellent property of leaf extracts of three indigenous native botanicals namely; Azadirachta indica A. Juss; Eucalyptus globules L. and Ocimum basilicum L. against aphids and mealybugs. The methanol extract of leaf was isolated by using soxhlet method. The leaf extracts were applied against aphids and mealybugs at dose levels of 1, 2, 4, 8 and 10%. Observations were made at 12 and 24 h. After 24 h of release of aphids and mealybugs, the highest repellency was recorded in A. indica leaf extract which gives 99.0 and 97.0% followed by E. globules leaf extract giving 96.0 and 93.0%. While minimum repulsion was seen in O. basilicum leaf extract 91.0 and 88.0%, respectively. As the dose increases, the repellent effect also increased irrespective of the plant extracts. The use of such plant extracts can control the population of serious pests like aphids and mealybugs in an environmental friendly way. Key words: Aphid, mealybug, biorational control, botanicals, Azadirachta indica, Eucalyptus globules, Ocimum basilicum

Recent advances and challenges in implementing IPM programmes in the entomological context of Indian agriculture

Integrated pest management (IPM) programmes are based on using multiple methods to maintain nuisance insects below tolerant levels in crop fields. Recent advances in IPM in developed countries have incorporated biological pesticides, microbial products, semiochemicals, and beneficial insects, but few of such programmes have been successfully implemented in developing countries, such as India. Semiochemicals play critical roles as signals in various interspecific and intraspecific interactions between insects and plants, and among interacting insects, plants, and microbes. In India IPM programmes have included mechanical, chemical, cultural, and biological management strategies. However, among these methods, biological management has its own limitations. Indian IPM scientists mostly work on individual crops, assessing damage severity by specific nuisance arthropods and the efficacy of particular management measure. However, very few government institutions or commercial companies are engaged in developing and commercializing either biological pesticides or semiochemicals. Government institutions mostly focus on research on pheromones of the pestiferous Lepidoptera and Coleoptera. Developing IPM programmes requires a clear understanding of crop-plant development, biology and population dynamics of the nuisance organisms, and the chemical and molecular interactions between the two. It also necessarily requires local knowledge of available, prevalent management tactics. Moreover, the IPM programmes have not been widely adopted in developing countries due to lack of proper knowledge and training farmers in efficient IPM practices, the need for more of human labour, and the complexity of IPM practices, all of which impede on the effective implementation of IPM programmes. In this article, we recapture the historical development of IPM efforts in India and ask whether this concept remains suitable to the present-day challenges in crop production. In this review, more specifically, those factors identified as obstacles to the more widespread adoption of IPM and ways of overcoming such barriers are discussed

Attraction of Myzus persicae (Hemiptera: Aphididae) to volatiles emitted from the Entomopathogenic Fungus Beauveria bassiana

Beauveria bassiana (Balsamo) Vuillemin infects a wide variety of insects, including the green peach aphid, Myzus persicae (Sulzer). Volatiles emitted from B. bassiana can act as semiochemical attractants or repellents, with most responses reported to date resulting in insects avoiding B. bassiana. Since insects can detect ‘enemy-specific volatile compounds’, we hypothesized the preference behavior of M. persicae would be influenced by volatile emissions from B. bassiana. We conducted Petri dish and Y-tube olfactometer bioassays to characterize the preference of M. persicae to B. bassiana strain GHA. During Petri dish bioassays, more apterous and alate M. persicae were recorded in the vicinity of agar colonized by B. bassiana compared to agar, or Fusarium proliferatum (Matsushima) Nirenberg and Ambrosiella grosmanniae Mayers, McNew, & Harrington as representatives of nonentomopathogenic fungi. Petri dish bioassays also determined that apterous and alate M. persicae preferred filter paper saturated with 1 × 107, 1 × 106, and 1 × 105B. bassiana conidia/ml compared to Tween 80. Y-tube bioassays documented that more apterous and alate M. persicae oriented upwind to volatiles from B. bassiana mycelia compared to agar. Apterous and alate Myzus persicae were also preferentially attracted to 1 × 107 and 1 × 106B. bassiana conidia/ml compared to Tween-80 during Y-tube bioassays. These results complement a previous finding that the mosquito Anopheles stephensi (Diptera: Culicidae) Liston is attracted to volatiles from B. bassiana. Future studies aimed at characterizing the olfactory mechanism leading to the attraction of M. persicae to B. bassiana could aid in optimizing lure-and-kill strategies

Electrophysiological and Behavioral Responses of an Ambrosia Beetle to Volatiles of its Nutritional Fungal Symbiont

Ambrosia beetles (Coleoptera: Scolytinae) cultivate their fungal symbiont within host substrates as the sole source of nutrition on which the larvae and adults must feed. To investigate a possible role for semiochemicals in this interaction, we characterized electrophysiological and behavioral responses of Xylosandrus germanus to volatiles associated with its fungal symbiont Ambrosiella grosmanniae. During still-air walking bioassays, X. germanus exhibited an arrestment response to volatiles of A. grosmanniae, but not antagonistic fungi Beauveria bassiana, Metarhizium brunneum, Trichoderma harzianum, the plant pathogen Fusarium proliferatum, or malt extract agar. Solid phase microextraction-gas chromatography-mass spectrometry identified 2-ethyl-1-hexanol, 2-phenylethanol, methyl benzoate and 3-methyl-1-butanol in emissions from A. grosmanniae; the latter two compounds were also detected in emissions from B. bassiana. Concentration-responses using electroantennography documented weak depolarizations to A. grosmanniae fungal volatiles, unlike the comparatively strong response to ethanol. When tested singly in walking bioassays, volatiles identified from A. grosmanniae elicited relatively weak arrestment responses, unlike the responses to ethanol. Xylosandrus germanus also exhibited weak or no long-range attraction to the fungal volatiles when tested singly during field trials in 2016–2018. None of the fungal volatiles enhanced attraction of X. germanus to ethanol when tested singly; in contrast, 2-phenylethanol and 3-methyl-1-butanol consistently reduced attraction to ethanol. Volatiles emitted by A. grosmanniae may represent short-range olfactory cues that could aid in distinguishing their nutritional fungal symbiont from other fungi, but these compounds are not likely to be useful as long-range attractants for improving detection or mass trapping tactics