Seasonal Abundance and Spatial Pattern of Distribution of Liriomyza trifolii (Diptera: Agromyzidae) and Its Parasitoid on Bean and Squash in South Florida

American serpentine leafminer, Liriomyza trifolii, is a polyphagous insect pest that feeds on a wide range of vegetable and ornamental plants around the world. To develop an effective IPM program, information on the seasonal field distribution and population dynamics of leafminer and its parasitoids is very important. Therefore, seasonal abundances and spatial distributions of, L. trifolii on snap bean and squash were studied during four crop growing periods between 2013 to 2015 in Homestead, Florida. The mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on snap bean were highest at 2 weeks after planting during all four growing periods. Whereas, the mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on squash were highest at 3 weeks after planting during all four growing periods. L. trifolii distributions tended to be aggregated on snap bean at 2 weeks after planting during most of growing periods but had uniform distributions on squash at 2 weeks after planting during most of growing periods. Similar results were seen on the distribution of leafminer parasitoids on both bean and squash.

Spodoptera littoralis genome mining brings insights on the dynamic of expansion of gustatory receptors in polyphagous noctuidae

The bitter taste, triggered via gustatory receptors, serves as an important natural defense against the ingestion of poisonous foods in animals, and the diversity of food diet is usually linked to an increase in the number of gustatory receptor genes. This has been especially observed in polyphagous insect species, such as noctuid species from the Spodoptera genus. However, the dynamic and physical mechanisms leading to these gene expansions and the evolutionary pressures behind them remain elusive. Among major drivers of genome dynamics are the transposable elements but, surprisingly, their potential role in insect gustatory receptors expansion has not been considered yet. In this work, we hypothesized that transposable elements and possibly positive selection would be involved in the active dynamic of gustatory receptor evolution in Spodoptera spp. We first sequenced de novo the full 465Mb genome of S. littoralis, and manually annotated all chemosensory genes, including a large repertoire of 373 gustatory receptor genes (including 19 pseudogenes). We also improved the completeness of S. frugiperda and S. litura gustatory receptor repertoires. Then, we annotated transposable elements and revealed that a particular category of class I retrotransposons, the SINE transposons, was significantly enriched in the vicinity of gustatory receptor gene clusters, suggesting a transposon-mediated mechanism for the formation of these clusters. Selection pressure analyses indicated that positive selection within the gustatory receptor gene family is cryptic, only 7 receptors being identified as positively selected. Altogether, our data provide a new good quality Spodoptera genome, pinpoint interesting gustatory receptor candidates for further functional studies and bring valuable genomic information on the mechanisms of gustatory receptor expansions in polyphagous insect species.

Effect of INM Practices on the Leaves Parameters of Terminalia tomentosa Food Plant of Antheraea mylitta Drury

Background: Terminalia tomentosa is a primary food plant of Antheraea mylitta Drury a polyphagous insect of Saturniidae family which is exploited commercially for the production of silk. Good quality of silk production depend on the nutrient of leaf. So, to optimize the nutrient of leaf integrated nutrient management practices has been used to increase soil fertility and to supply plant nutrient at an optimum. Methods: In order to evaluate the effect of INM practices on the leaves parameters of Terminalia tomentosa food plant of Antheraea mylitta Drury. An experiment based on randomised complete block design with 21 treatments and three replication was conducted at Central Tasar Research and Training Institute, Nagri, Ranchi in the year 2019-20. Result: Results revealed that the application of INM treatments are significant on various leaf parameters. Highest single leaf length and breadth mean was observed in T19 (23.29 cm; 11.96 cm) was applied with 75% RDF through fertilizer+25% through vermicompost+ Azotobacter + PSB, weight of single leaf was found to be highest in T13 (5.19 g). The number of leaf was recorded highest in T19 (1892). The fresh leave yield ranged from 1617.317-5208.224 g with average mean of 4085.72 g, T19 (5032.1 g) recorded the highest fresh leaf yield. The dry matter content was found highest in T19 (340.56 g). The moisture content was recorded higher in T4 (71%) followed by T15 (69%).

Bioactivity of Neem Seed Oil mixed with Pyroligneous Acid from Rice Husks against Spodoptera litura

Biopesticides are environmentally friendly solutions used for pest control management. This is a feature of Neem (Azadirachta indica) seed oil and tar, which provides a synergistic effect on the bioactivity of pyroligneous acid, and both are known to have bioactive compounds. Therefore, the purpose of this study was to evaluate the effect of neem seed oil and tar on pyroligneous acid from rice husks in conventional emulsion form, and their efficacy on the polyphagous insect Spodoptera litura. Neem seed oil was added at concentrations of 10, 20, 30, and 40%, while the concentration of tar was 0.5, 1.0, and 2.0%. The conventional emulsion formed was then characterized using a digital microscope. The addition of neem seed oil and tar were able to increase the antifeedant activity of pyroligneous acid by 63.6 % while both neem oil and tar by 72.6 %. The 2.0% tar formulation (N4PT2) showed the highest antifeedant activity against S.litura (97.9 %) and had the smallest droplets size ranges (2.90 - 24.16 µm). The addition of tar tends to reduce the droplet size of neem oil and increase antifeedant activity.

Investigation of secondary metabolites in bean cultivars and their impact on the nutritional performance of Spodoptera littoralis (Lep.: Noctuidae)

Spodoptera littoralis (Boisd) is globally recognized as a destructive polyphagous insect pest of various crops in the world. It is commonly managed by chemical pesticides, which can cause deleterious effects such as environmental pollution, toxicity to non-target organisms and the emergence of secondary pests. Hence, investigations into alternative pest control strategies such as the use of resistant host plant cultivar against S. littoralis is important. This study aimed to explore the nutritional performance of S. littoralis larvae in dependence on total anthocyanin, flavonoid, and phenol levels across 11 bean cultivars (Phaseolus and Vigna spp.) under laboratory conditions. The results revealed that the Mashhad cultivar accumulated the highest amount of total phenols (13.59 mg ml−1), whereas Yaghout and Arabi cultivars posed the lowest total phenols contents (1.80 and 1.90 mg ml−1, respectively). Across larval instars (third to sixth), the highest consumption index and relative consumption rate were recorded on the Mashhad cultivar. The lowest values of efficiency of conversion of ingested food and the efficiency of conversion of digested food of total larval instars were detected in the larvae which were reared on the Mashhad cultivar. Likewise, the lowest value of the index of plant quality (IPQ) was obtained in the Mashhad cultivar; however, IPQ was figured out at the highest level in the Arabi cultivar. Our findings show that the differential accumulation of secondary metabolites would change the nutritional quality of plants for S. littoralis. Based on the findings, the Mashhad cultivar may serve as a candidate for either integrated pest management or breeding programs aiming at controlling this pest.

Exploring integrated pest management strategies in the control of the fall armyworm in smallholder organic agriculture farms in Africa

The invasion of the fall armyworm was first reported in Africa in the year 2016. It has since then spread to over 40 countries across Africa, Asia and Australia. Being a polyphagous insect, the potential devastation effects of fall armyworm are enormous, especially among smallholder farmers. Currently, most farmers rely on the use of synthetic pesticides for the control of this pest. Organic agriculture however usually has very limited synthetic products approved for the control of pests. Organic production system therefore often depends on ecological processes, biodiversity and cycles adapted to local conditions for the management of pest. This paper reviews the availablemanagement methods applicable to the control of fall armyworm that can be adopted in an organic agriculture setting. Agroecological methods such as the push-pull technology, crop rotation and other methods including the use of resistant varieties, pheromone traps and biocontrol agents form an important control building block. Integrating these methods in a manner that is acceptable for organic certification will need further research, but it is certainly the way to go in combating the menace of the fall armyworm in organic agricultureand were reviewed in this paper.

RNA interference-mediated tolerance to whitefly (Bemisia tabaci) in genetically engineered tomato

Whitefly (Bemisia tabaci) is a polyphagous insect that causes huge damage in several horticultural crops, including tomato, by sucking nutrients from the phloem and transmitting viruses. Whiteflies are particularly difficult to manage and the use of chemicals remains the common practice, which causes the development of insecticidal resistance. Thus, there is considerable interest in the introduction of whitefly resistance by classical and molecular breeding. Here, we explored the concept of using an RNA interference construct to silence a v-ATPase gene in whiteflies interacting with transgenic tomato plants that express siRNA molecules corresponding to a fragment from the B. tabaci vATPase. PCR analyses revealed the presence of both ΔATPase and nptII transgenes in all transgenic lines. siRNA expressing lines were challenged against whitefly and revealed a mortality rate of 57.1% in transgenic line 4.4.1, while in the control the mortality was 7.6%. Mortality of 2nd instar nymphs was higher on the transgenic plants and the development of 3rd instar nymphs was slightly longer than on the control plants. Although the attraction of insects was not significantly different between treatments, the number of eggs laid by the insects on the transgenic plants was significantly lower, compared to the controls. RT-qPCR revealed a decreased expression level of endogenous v-ATPase gene in whiteflies feeding on transgenic plants. No unexpected effect was observed on the non-target insects Myzus persicae or Tuta absoluta. Results presented here may form the foundation for the generation of elite tomato varieties resistant to whitefly, a devastating insect pest.

Olfactory Proteins and Their Expression Profiles in the Eucalyptus Pest Endoclita signifier Larvae

Endoclita signifier Walker (Lepidoptera: Hepialidae), a polyphagous insect, has become a new wood-boring pest in Eucalyptus plantations in southern China since 2007, which represents a typical example of native insect adaptation to an exotic host. After the third instar, larvae move from soil to standing trees and damage the plants with a wormhole. Although females disperse to lay eggs, larvae can accurately find eucalyptus in a mingled forest of eight species, which leads us to hypothesize that the larval olfactory system contributes to its host selection. Herein, we investigated the transcriptomes of the head and tegument of E. signifer larvae and explored the expression profiles of olfactory proteins. We identified 15 odorant-binding proteins (OBPs), including seven general OBPs (GOPBs), six chemosensory proteins (CSPs), two odorant receptors (ORs), one gustatory receptor (GR), 14 ionotropic receptors (IRs), and one sensory neuron membrane protein (SNMP). Expression profiles indicated that all olfactory proteins, except for EsigCSP1, were expressed in the head, and most were also detected in non-olfactory tissues, especially thorax tegument. Furthermore, EsigOBP2, EsigOBP8, EsigGOBP1, EsigGOBP2, EsigGOBP5, EsigCSP3, EsigCSP5, and EsigOR1 were expressed most strongly in the head; moreover, EsigCSP3 expressed abundantly in the head. EsigGR1 exhibited the highest expression among all tissues. Besides phylogenetic analysis shows that EsigGOBP7 probably is the pheromone-binding protein (PBP) of E. signifier. This study provides the molecular basis for future study of chemosensation in E. signifier larvae. EsigCSP3 and EsigGR1, which have unique expression patterns, might be factors that govern the host choice of larvae and worth further exploration.