Coccinellidae Research Articles

Prey species mediated slow and fast development in two aphidophagous ladybird beetles

Prey species mediated slow and fast development in two aphidophagous ladybird beetles

Rnai-based functional analysis of bursicon genes related to cuticle pigmentation in a ladybird beetle

In arthropods, the binding of a bursicon (encoded by burs and pburs) heterodimer or homodimer to a leucine-rich repeat-containing G protein coupled receptor LGR2 (encoded by rk) can activate many physiological processes, especially cuticle pigmentation during insect ecdysis. In the current paper, we intended to ascertain whether bursicon signaling mediates body coloration in the 28-spotted larger potato ladybird, Henosepilachna vigintioctomaculata, and if so, by which way bursicon signal governs the pigmentation. The high expression of Hvburs, Hvpburs and Hvrk occurred in the young larvae, pupae and adults, especially in the head and ventral nerve cord. RNA interference (RNAi) aided knockdown of Hvburs, Hvpburs or Hvrk in the prepupae caused similar phenotypic defects. The pigmentation of the resultant adults was affected, with significantly reduced dark areas on the sternums. Moreover, the accumulated mRNA levels of two sclerotin biosynthesis genes, aspartate 1-decarboxylase gene Hvadc and N-β-alanyldopamine synthase gene Hvebony, were significantly increased in the Hvburs, Hvpburs or Hvrk RNAi beetles. Furthermore, depletion of either Hvadc or Hvebony could completely rescue the impaired coloration on the sternums of Hvpburs RNAi adult. Our results supported that bursicon heterodimer-mediated signal regulate cuticle pigmentation. The bursicon signaling may tune the ratio of melanins (dark/black, brown) to sclerotins (light yellow, colorless) exerting its regulative role in the pigmentation of H. vigintioctomaculata sternums.

Identification of microRNA and their potential role in regulation diapause termination in seven spot ladybird beetle, Coccinella septempunctata

Diapause is an alternative development stage in seven spot ladybird beetle, Coccinella septempunctata. However, the regulatory mechanism governing the initiation, maintenance, and termination of diapause in the seven-spot ladybird have not been extensively studied. MicroRNAs (miRNAs), a type of non-coding RNA, might be involved in diapause regulation and related physiological processes. The objective of this study is to investigate the potential involvement of miRNAs in diapause termination in C. septempunctata. High-throughput sequencing was used to identify miRNAs associated with diapause termination in C. septempunctata. A total of 769 miRNAs were identified, potentially implicated in diapause termination, including 673 evolutionarily conserved miRNA and 96 putatively novel-miRNAs. Among these, two evolutionarily conserved miRNAs, aae-miR-305-5P and tca-miR-277-5P, exhibited differential abundance during diapause termination compared to diapause. aae-miR-305-5P was overexpressed in diapause termination ladybird beetle and may be responsible for silencing the expression of candidate genes in peroxisome pathway associated with diapause termination. Conversely, tca-miR-277-5P was under-expressed in diapause termination and may promote the expression of genes related to the longevity regulating pathway, thereby increase the lifetime, a characteristic feature of diapause termination. In addition, a putatively novel-miRNA (unconservative_c62764) was overexpressed in diapause termination ladybird beetle, potentially contributing to the decreased expression of genes related to Wnt signaling pathway during diapause termination. These findings highlighting the significant roles of microRNAs in pathway such as longevity regulation, perisome function, and Wnt signaling, which may regulate diapause termination in C. septempunctata. This study might help us to unveil the miRNA involvement in gene expression regulation of diapause termination in insects.

Diversity of Ladybird Beetles (Coleoptera: Coccinellidae) in Tenerife and La Gomera (Canary Islands): The Role of Size and Other Island Characteristics.

This paper provides new data on the ladybird beetles (Coccinellidae) from two islands in the Canary archipelago: Tenerife, the largest island, and La Gomera, the second smallest. As they clearly differ in size but are similar in location and geological age, they are a suitable model for testing the species-area relationship. Our study shows that, in line with this main assumption of the theory of island biogeography, clearly more species occur on a large island (Tenerife) than on a small one (La Gomera). The field surveys documented the occurrence of 35 ladybird species on Tenerife (including 5 not previously reported from this island) and of 20 species on La Gomera (2 species new to the island). Coelopterus sp. collected on Tenerife (a single female that could not be identified to species) is the first record of this genus for the whole Canary Islands. Taking our data and previously published records into account, 47 species of Coccinellidae are known to occur on Tenerife and 26 species on La Gomera. Tenerife has by far the richest ladybird fauna of all the Canary Islands (the next in line, Gran Canaria, has 41 recorded species), but it also has the highest number of non-native ladybird species. All of the ten non-native species recorded in the Canary Islands are found on Tenerife, and for most of them, Tenerife was the island of their first appearance in the archipelago. This island, much more distant from the mainland than the other relatively large islands (Fuerteventura, Lanzarote), appears to be the main recipient of ladybirds immigrating to the Canary Islands. Tenerife can play this role probably because of its great habitat diversity and altitude variation, as well as intensive tourism and trade-related transport.

Yellow Sticky Cards Reduce the Numbers of Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) Following Augmentative Releases against the Fruit Borers Carposina sasakii (Lepidoptera: Carposinidae) and Grapholita molesta (Lepidoptera: Tortricidae) in a Pear Orchard.

Integrated pest management relies upon mutual compatibility among pest control tactics. The fruit-boring moths Carposina sasakii and Grapholita molesta can be devastating pests of pome and stone fruit production. Trichogramma dendrolimi parasitizes the eggs of these pests, preventing their eclosion, but its efficacy can be reduced by other pest control tactics. We tested T. dendrolimi attraction to five colors, and moth attraction to six colors, in laboratory choice tests, and thereafter deployed yellow sticky cards in tandem with releases of T. dendrolimi in field trials in a pear orchard. Yellow sticky cards deployed at high density trapped T. dendrolimi and reduced their numbers post-release. They also trapped adult G. molesta, which appeared to compensate for reduced egg parasitism on this species, but not on C. sasakii, which had higher abundance in plots with yellow sticky cards. The cards also captured adult lacewings, likely reducing their numbers in the field, but did not capture large numbers of lady beetles. The results suggest that yellow sticky cards can be used at high density to control aphids, psyllids and leafhoppers in early spring (March and April) when natural enemies are in low numbers, then removed in May so as not to interfere with augmentative releases of T. dendrolimi that must be timed to coincide with peak flights of fruit-boring moths. This strategy should enhance the compatibility of yellow sticky cards with egg parasitoid releases.

Effect of Micronutrients on Incidence, Damage Severity of Sucking Insect Pests of Sunflower and its Impact on Yield and other Arthropods

An experiment was conducted in a field on 23074/N latitude and 90035/E longitude at the central farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh from November 2021 to April 2022. The experiment of eight treatments as follows: T1 = Urea @ 210 gm/plot + TSP @ 84gm/plot + MoP @ 98gm/plot [recommended doses (RD) of Urea, TSP and MoP] +Boron @ 7.0 gm/ Plot+ ZnSo4 @ 8.4 gm/ Plot ;T2 = RD of Urea, TSP and MoP +Spraying 0.2% Borax @ 2gm/ L of water; T3= RD of Urea, TSP and MoP +Spraying 0.2% ZnSo4 @ 2gm/ L of water; T4= RD of Urea, TSP and MoP +Spraying 0.5% Borax @ 5gm/ L of water; T5 RD of Urea, TSP and MoP +Spraying 0.2% Borax + 0.2% ZnSo4 @ 2gm/ L of water; T6 = Urea @ 210 gm/plot+ TSP @ 180 gm/plot+ MoP @ 150gm/plot + Spraying 0.5% ZnSo4 @ 5gm/ L of water; T7 = Urea @ 210 gm/plot+ TSP @ 180gm/plot+ MoP @ 150gm/plot+ MgSo4 @ 12 gm/ Plot and T 8= control. The experiment was laid out in a Randomized Complete Block Design (RCBD) with 8 treatments and 3 replications. The overall result indicates that the combination of different micronutrients decreased the incidence of sucking insect pests of sunflower and increased the abundance of beneficial arthropods compared to T8 treatment. In T1 treatment, the lowest leaf infestation percentage caused by aphid 17.49 and 19.50 %; Jassid 14.19 and 14.89 % and White fly 26.18 and 30.83 % at the vegetative and reproductive stages respectively. The highest number of beneficial arthropods per plot of lady bird beetle both adults and grubs ((3.63 and 5.53 respectively); honey bee (22.36), ant (3.55), spider (1.42) was also recorded in T1 treatment. The highest yield contributing characters of sunflower, the highest of head/ capitulam diameter (9.75cm), height of plant per plot (179.73 cm), leaf width (14.24 cm), leaf length (21.05 cm), area of leaves per plant (62.29 cm) and number of leaf per plant (21.93), number of total head per plot (29.83), number of seed per head (725.56), weight of single seed (1.03 mg), and weight of seed per head (54.96 gm) of sunflower were observed in T1 treatment which was statistically different from among all other treatments. The highest sunflower yield (1.92 kg /plot) and oil content (0.93 liter/2kg and 46.5%) were also observed from T1 treatment. Among the different micronutrient treatment combinations, different micronutrients using in T1 treatment were more effective for the reducing the incidence of sucking insect pests on sunflower. In the term of effect of micronutrients, T1= Recommended doses of Urea, TSP and MoP + Boron @ 7.0 gm/ Plot+ ZnSo4 @ 8.4 gm/ Plot; was an eco-friendly pest management practice for sunflower by which one can significantly reduce pest infestation without use of any chemical insecticides.

Behavioral response of zigzag ladybird beetle Cheilomenes sexmaculata to the HIPVs induced by cotton aphid, Aphis gossypii

Behavioral response of zigzag ladybird beetle Cheilomenes sexmaculata to the HIPVs induced by cotton aphid, Aphis gossypii

Heterospecific mating interference in ladybird beetles: age dependent patterns and consequences

Heterospecific mating interference in ladybird beetles: age dependent patterns and consequences

The Effects of Natural Insecticides on the Green Peach Aphid Myzus persicae (Sulzer) and Its Natural Enemies Propylea quatuordecimpunctata (L.) and Aphidius colemani Viereck.

Botanical insecticides and soaps are frequently proposed as environmentally safer alternatives to synthetic insecticides. However, the efficacy and selectivity of these products are often only partially supported by empirical evidence. Here, we tested the effectiveness of five botanical insecticides, belonging to different categories, on the green peach aphid Myzus persicae (Sulzer) and their selectivity towards two natural enemies, the ladybird beetle Propylea quatuordecimpunctata (L.) and the parasitoid Aphidius colemani (Dalman). White thyme essential oil (EO), sweet orange EO, crude garlic extract and Marseille soap were tested and compared with a pyrethrin-based commercial product. Both direct spray assays and residual contact assays on treated cabbage leaf disks were carried out. The tested products had low efficacy against aphids when compared to pyrethrins but were in general less detrimental to ladybird beetle larvae, meaning that if applied against other pests, they have a lower chance of harming this agent of aphid biocontrol. Some of the products (soap, orange EO) did, however, show direct exposure toxicity toward ladybird larvae, and thyme EO had extensive phytotoxic effects on cabbage leaves, possibly indirectly leading to higher mortality in ladybird adults. These results underline the necessity for case-by-case evaluations of botanical insecticides.

Population genomics and demographic modeling enhance our understanding of trophic level interactions in biological control

In this paper, we focus on the application of population genomics, including next-generation sequencing and demographic modeling, to enhance the understanding of historical and contemporary trophic level interactions that are a fundamental basis of biological control. We outline how the integration of ecological approaches with population genomics and demographic modeling can provide additional insights into existing trophic interactions and how natural enemies, their parasitoids, and pest species evolve through these interactions, potentially affecting future levels of biological control. We briefly review and summarize our recent population genomic studies of predatory ladybird beetles and discuss how our results provide guidelines for the use of population genomics techniques and population demographic modeling to enhance our understanding of trophic level interactions. Our intent is to demonstrate as a proof of concept, how these methods can supplement currently used techniques and add a complementary genomic aspect to ecological understandings of trophic level interactions, including estimates of effective population sizes of natural enemies and pest species, examination of correlations between these effective population sizes, and evolutionary changes in natural enemies and pest species which may influence levels of biological control. This in combination with experiments and simulations provide a well-rounded framework for using population genomics to inform multi-tier trophic level interactions.

Consumption of nectar-like sugar solutions promotes longevity and fecundity in the ladybird beetles Harmonia axyridis and Hippodamia convergens

Consumption of nectar-like sugar solutions promotes longevity and fecundity in the ladybird beetles Harmonia axyridis and Hippodamia convergens

PhyloAln: A Convenient Reference-Based Tool to Align Sequences and High-Throughput Reads for Phylogeny and Evolution in the Omic Era.

The current trend in phylogenetic and evolutionary analyses predominantly relies on omic data. However, prior to core analyses, traditional methods typically involve intricate and time-consuming procedures, including assembly from high-throughput reads, decontamination, gene prediction, homology search, orthology assignment, multiple sequence alignment, and matrix trimming. Such processes significantly impede the efficiency of research when dealing with extensive data sets. In this study, we develop PhyloAln, a convenient reference-based tool capable of directly aligning high-throughput reads or complete sequences with existing alignments as a reference for phylogenetic and evolutionary analyses. Through testing with simulated data sets of species spanning the tree of life, PhyloAln demonstrates consistently robust performance compared with other reference-based tools across different data types, sequencing technologies, coverages, and species, with percent completeness and identity at least 50 percentage points higher in the alignments. Additionally, we validate the efficacy of PhyloAln in removing a minimum of 90% foreign and 70% cross-contamination issues, which are prevalent in sequencing data but often overlooked by other tools. Moreover, we showcase the broad applicability of PhyloAln by generating alignments (completeness mostly larger than 80%, identity larger than 90%) and reconstructing robust phylogenies using real data sets of transcriptomes of ladybird beetles, plastid genes of peppers, or ultraconserved elements of turtles. With these advantages, PhyloAln is expected to facilitate phylogenetic and evolutionary analyses in the omic era. The tool is accessible at https://github.com/huangyh45/PhyloAln.

Tank-Mix Adjuvants Enhance Pesticide Efficacy by Improving Physicochemical Properties and Spraying Characteristics for Application to Cotton with Unmanned Aerial Vehicles.

Tank-mix adjuvants have been used to reduce spray drift and facilitate the efficacy of pesticides applied with unmanned aerial vehicles (UAVs). However, the effects of specific adjuvants on pesticide characteristics and the mechanism of action remain unclear. Herein, we analyzed the effects of three different types of tank-mix adjuvants (plant oil; mineral oil; and mixture of alcohol and ester) on the surface tension (ST), contact angle, wetting, permeation, evaporation, spray performance, and aphid-control effects of two types of pesticides. The mineral oil adjuvant Weichi (WCH) was highly effective in reducing the pesticide solution ST, improving the wetting and penetration ability, increasing droplet size, and promoting droplet deposition. The mixed alcohol and ester adjuvant Quanrun (QR) showed excellent wetting and antievaporation properties and promoted droplet deposition. A plant oil adjuvant (Beidatong) moderately improved wetting and penetration ability and reduced droplet drift. Field tests showed that the control efficiencies (CEs) of two pesticides were increased after the addition of adjuvants, even with 20% reductions in pesticide application. When the UAV was operated at 1.5 m, the CEs of two pesticides were increased from 65.39 and 66.63% to 73.11-76.52% and 77.91-88.31%, respectively. When operated at 2.5 m, the CEs were increased from 51.24 and 68.60% to 65.06-75.70% and 77.57-92.59%, respectively. Especially, the CEs of pesticides with WCH and QR increased obviously. Importantly, neither WCH nor QR inhibited hatching of the critical insect natural enemy ladybird beetle at concentrations used in the field. This study provides a framework for assessment of tank-mix adjuvants in aerial sprays and directly demonstrates the value of specific adjuvants in improving pesticide bioavailability and minimizing associated environmental pollution.

Seasonal Incidence of Major Insect Pest of Chickpea and their Natural Enemies in Vindhaya Region of Madhya Pradesh

Field experiment carried out at the Entomology Instructional Farm, JNKVV-College of Agriculture Rewa, MP during rabi season 2018-19 revealed that incidence of the chickpea pod borer Helicoverpa armigera. Population range of pod borer during different weather weeks varied between 0.30 and 1.89 larvae/mrl (April 2nd week and March 2nd week respectively). Peak larval population of Helicoverpa armigera was recorded in 2nd week of March (11 standard weeks). A weak negative correlation was observed with the maximum relative humidity and minimum relative humidity correlation, -0.172 and -0.595 respectively and a non significant positive correlation with maximum temperature, minimum temperature and rainfall. The respective r was found to be 0.306, 0.391 and 0.269. In district Rewa, MP, India the insect-pests of chickpea and their natural enemies during rabi the total seven species was recorded in Chickpea in which six pests minor in nature and one major pest Chickpea pod borer (Helicoverpa armigera). Termite (Odontotermes obesus Ram.), White grub (Holotrichia consanguinea Bl.), Black aphid (Aphis craccivora Koch), Grasshopper (Chrotogonus trachypterus Blan.), Semilooper (Autographa nigrisigna L.), Cut worm (Agrotis ipsilon Huf.) are minor in nature. Seven natural enemies found during field investigation i.e. lady bird beetle (Chilomenes sexmaculata Fab.), lady bird beetle (Coccinella septempunctata L.), Praying mantis (Mantis religiosa), Dragon fly (Crocothemis servilia Drury), Campoletis parasitoid (Campoletis chlorideae Uch.), Indian mynah (Acridotheris tristis L.), King crow (Dicrurus macrocerus Vie.) in chickpea observed in low to medium population on the crop and to help in reduction of pest population.

Study of Population Dynamics of Syrphid Fly (Order- Diptera, Family- Syrphidae) in ITM University Gwalior, India

An intriguing ecological interaction can exist between aphids and Syrphid flies, particularly in the setting of millet crops. Aphids (Order Hemiptera: Family Aphididae) are a problem variety of crops, including all types of millets. Syrphid flies (Order Diptera: Family Syrphidae) naturally prey on aphids when they are in their larval stage. Syrphid fly larvae are referred to as "aphid lions" or "hoverfly larvae." Aphids are the main source of food for these larvae, and they manage the aphid population in millet crops. Therefore, Syrphids are used as natural enemies and biological control agents and syrphid flies are advantageous insects in agriculture. The present study was conducted in the month of August 2021 to March 2022 (summer and winter season) to find out the population dynamic of syrphid flies in agricultural farms and the campus of ITM University. The target crops like maize, sorghum, pearl millets, okra, mustard crop, cabbage cauliflower, marigold and brinjal were tagged and marked and Syrphid fly larvae and pupa were counted four times in a month. The larvae and pupa were also collected and kept for adult emergence. The maximum number of larvae were collected from the Turari campus and were as a minimum found in CRC 2. The other predator like lady bird beetles were also observed but their population was very minor. The population of syrphid flies and larvae depends on the climatic conditions and the availability of foods and their prey.

Adapting to changing methodology in a long‐term experiment

AbstractLong‐term experiments are critical for understanding ecological processes, but their management comes with unique challenges. As time passes, projects may encounter unavoidable changes due to external factors, like availability of materials, affecting aspects of their research methodology. At the Kellogg Biological Station Long‐Term Ecological Research Site, one of the many National Science Foundation‐funded long‐term research stations, a three‐decade project recently experienced a supply‐chain‐induced change in insect sampling methodology in their lady beetle observation study. Since 1989, lady beetles (Coleoptera: Coccinellidae) have been sampled weekly over the growing season using yellow sticky cards. In 2021, the original sticky traps were discontinued by the manufacturer and replaced with a similar, but not identical trap. We conducted a 3‐year study while the new traps were phased in to examine how the trap change would impact the observed biodiversity patterns at the site. We examined community metrics and individual taxa captures to examine within‐year and between‐year differences in performance between the card types. Overall, we noted several small but statistically detectable differences in capture patterns between the two trap types. After accounting for other sources of variation, we observed a difference in Shannon diversity of insects captured on the two card types, but not richness or abundance, for the overall insect community. Yet, these differences were dwarfed by the magnitude of difference observed between years within card types. For individual taxa, similar patterns held: between trap differences could be detected statistically, but the number of differences in capture rate between trap types was less than the number of differences observed for the same trap, between years. Thus, we conclude that while subtle changes in methodology could impact data produced in long‐term experiments; in this case, the magnitude of this change is smaller than other factors such as time and plant treatment. However, if sustained changes in the capture rates of focal taxa are observed, future data users may use our observations to specifically quantify and correct for these shifting patterns related to the protocol change.

Insights from different reproductive gene knockdowns via RNA interference in the lady beetle Eriopis connexa: Establishing a new model for molecular studies on natural enemies.

Insect pest control can be achieved by the application of RNA interference (RNAi), a key molecular tool in functional genomics. Whereas most RNAi research has focused on insect pests, few studies have been performed on natural enemies. Validating the efficacy of RNAi in natural enemies is crucial for assessing its safety and enabling molecular research on these organisms. Here, we assessed the efficacy of RNAi in the ladybird beetle Eriopis connexa Germar (Coleoptera: Coccinellidae), focusing on genes related to reproduction, such as vitellogenin (Vg) and its receptor (VgR). In the transcriptome of E. connexa, we found one VgR (EcVgR) and two Vg genes (EcVg1 and EcVg2). These genes have been validated by in silico analyses of functional domains and evolutionary relationships. Five-day-old females were injected with 500 ng/µL of a specific double-stranded RNA (dsRNA) (dsEcVg1, dsEcVg2, or dsEcVgR) for RNAi tests, while nonspecific dsRNA (dsGFP or dsAgCE8.1) was used as a control. Interestingly, dsEcVg2 was able to knockdown both Vg genes, while dsEcVg1 could silence only EcVg1. Additionally, the viability of the eggs was significantly reduced when both Vg genes were knocked down at the same time (after treatment with dsEcVg2 or "dsEcVg1+dsEcVg2"). Ultimately, malformed, nonviable eggs were produced when EcVgR was silenced. Interestingly, no dsRNA treatment had an impact on the quantity of eggs laid. Therefore, the feasibility of RNAi in E. connexa has been confirmed, suggesting that this coccinellid is an excellent Neotropical model for molecular research on natural enemies and for studying RNAi nontarget effects.

Interaction of Predatory Ladybird Beetle, Micraspis discolor with Nilaparvata lugens throughout Paddy Growing Seasons

Coccinellidae is a high-interest family that has performed well and is widely distributed. It is valuable in economic service because it acts as an agricultural biological control agent. The Micraspis discolor (Syn=Verania) (Coleoptera: Coccinellidae) is a successful omnivorous predator in rice ecosystem and functions well as a general biological control for maintaining the population of brown planthopper (BPH) (Nilaparvata lugens), the major rice pest worldwide. Studies of natural enemies’ abundance are necessary to increase the practical use of biological control in agriculture. This study investigated the abundance correlation of M. discolor (prey) and rice pest N. lugens (prey) from two different geographical areas of rice fields in west and south Peninsular Malaysia. The cyclone lightrap and sweep net method succeeded in collecting 185 individuals of M. discolor and N. lugens. The study indicated that M. discolor, and the N. lugens collected from Selangor were more numerous than Johor in the ripening phase than in the reproductive and vegetative phases. M. discolor can be found in all stages of rice growth. There are positive correlations between M. discolor and N. lugens in both localities throughout the rice growing season. The positive correlation highlighted that the number of pests has increased parallel to the number of predators and vice versa. The use of M. discolor as a predator is essential in agriculture, along with the treatment of a healthy ecosystem landscape of diverse vegetation combinations, which helps to reduce the use of pesticides.

Crowding as a possible stress factor in food choice of aphidophagous ladybird beetle, Propylea dissecta (Mulsant)

Crowding induces behavioural and lasting morphological and chromatic changes in insects. This study examined how larval rearing density of Propylea dissecta (Mulsant, 1850) affected food choice and development duration, hypothesising that larvae under stress will opt for lower quality food as larval density increases. Larvae were reared at various densities under three crowding treatments: direct physical, indirect physical, and chemical tracks. In each treatment, larvae experienced crowding at densities of 0, 2, 4, 6, 8, 10, and 12 individuals per arena. Fourth stage larvae were provided with food choice of aphids, heterospecific eggs, and conspecific eggs. Significant effect of crowding on total development duration, first consumption time, and first food consumption was observed. Decrease in development duration at densities of 4 and 6 and increase in development duration at low and high densities were observed in direct physical crowding. Indirect physical and chemical crowding yield the shortest development duration at densities of 8, 10, and 12, when compared to low and moderate crowding. First encounter time increased with increasing chemical tracks concentration, while first consumption time decreases with crowding across all groups. First consumed food was also significantly influenced by crowding, suggesting a negative impact on larval food choice. Our results indicate that crowding among larvae leads to a longer development duration and show less selectivity in their food choices.

Seasonal incidence of major sucking pests of Bt cotton and their natural enemies with relation to weather parameters

Study on population dynamics of major sucking pests infesting Bt cotton showed that aphid, jassid, whitefly and thrips initiated from 28th SMW (2nd week of July), 28th SMW (2nd week of July), 29th SMW (3rd week of July) and 27th SMW (1st week of July), respectively. Peak infestation of aphid (21.20 aphid per 3 leaves) observed during 1st week of December (49th SMW). Jassid population observed highest in 40th SMW (14th WAS) with 9.88 jassid per 3 leaves, while the maximum whitefly population was observed during 43rd with 11.84 whitefly per 3 leaves. Population of thrips reached its peak during 34th SMW (8th WAS) with 15.32 thrips per 3 leaves. The peak population of lady bird beetles (4.52 grubs and adults per plant) was recorded during 43rd SMW (17th WAS) and the peak population of spider was recorded during 34th SMW (8th WAS) i.e. 1.36 spider per plant. Among the different abiotic environmental factors, jassid and whitefly had significant positive correlation with maximum temperature. Significant positive correlation was showed by thrips with minimum temperature. Morning relative humidity and evening relative humidity showed non-significant negative correlation with all sucking pest except thrips. Rainfall had non-significant positive correlation with jassid, whitefly and thrips. Bright sunshine had non-significant positive correlation with all sucking pests except thrips.