Oviposition preference not necessarily predicts offspring performance in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on vegetable crops

Given the new spread and potential damage of the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in Asia, it has become imperative to understand the development biology of this invasive species on selected vegetable crops in newer geographical regions. In this study, we investigated the ovipositional preference of FAW females on different host plants, under choice- and non-choice tests. In addition, using the age-stage, two-sex life table theory, we assessed the performance of immature FAW individuals fed and reared on selected vegetable crops to get information related to development time, survival, reproduction and longevity. Fall armyworm females had an oviposition preference on maize compared to other vegetable crops, including cabbage and soybean, and reluctance for tomato, which was confirmed during the choice and non-choice tests. In contrast to the oviposition preference, our results also suggest that despite low preference for cabbage, soybean, and tomato, these crops seemed to provide a high benefit for an appropriate offspring performance, exceeding in some cases the benefits from a maize-based diet. Information from this study was discussed in terms of FAW ecology and how female’s decision affects their reproductive fitness, and the survival and performance of its offspring.

Influence of Morphological Attributes of Cowpea Genotypes on Oviposition of Pulse Beetle (Callasobruchus maculatus F.)

Background: Cowpea is an excellent host for Callasobruchus maculatus (F.). These beetles cause havoc in stored cowpea. They have the habit of cementing their eggs to the surface of the host seeds. Hence, the present study was aimed to the find the influence of morphological characters of cowpea varieties/genotypes on oviposition of the pulse beetle. Methods: The ovipositional preference of C. maculatus on 14 cowpea varieties/genotypes was studied under the free choice condition and the data thus obtained were correlated with the morphological characters like seed shape, colour and texture. Result: Each variety/genotype had a significant effect on egg laying by C. maculatus. Significantly least oviposition was noticed in GC 3 (35.33 eggs), having a rough testa texture and greater number of eggs were found on GC 1612 (117.33 eggs) having smooth texture. The pulse beetle preferred smooth textured seeds for egg laying irrespective of its shape and colour. This was again confirmed by one of the genotypes GC 1702, which belongs to the Holstein group based on the eye pattern of the cowpea, in this genotype the pulse beetle preferred to lay eggs on the smooth brown portion surrounding the hilum than the wrinkled white portion.

Elucidating the Fitness of a Dead-End Trap Crop Strategy against the Tomato Fruitworm, Helicoverpa armigera

Solanum viarum has been proposed as a potential dead-end trap crop for the management of Helicoverpa armigera because of its unsuitability for larval growth and survival despite being overwhelmingly preferred for oviposition. This study delved into the different S. viarum accessions for ovipositional preference and non-suitability for larval growth and survival of H. armigera. Besides, foliage trichomes, acylsugars, and phenolic content of S. viarum plants were assessed and compared with tomato. Since there is no significant variation in the ovipositional preference and larval performance of H. armigera, our result revealed that all those evaluated accessions of S. viarum have the potential to be used as a dead-end trap crop for the management of H. armigera. However, significant variation among the S. viarum accessions in terms of H. armigera oviposition was also evident in a no-choice experiment. Because of high-density glandular trichomes, acylsugars, and phenolic content, S. viarum significantly impaired H. armigera larval growth and survival compared to the tomato. Hence, our study elucidated that the S. viarum plant fits with the criteria for dead-end trap crop, and has the potential as a dead-end trap crop for the H. armigera, which needs to be tested under large, open-field conditions.

Influence of Plant Physical and Anatomical Characteristics on the Ovipositional Preference of Orius sauteri (Hemiptera: Anthocoridae)

Natural enemies play an important role in managing insect pests. Orius sauteri (Poppius) (Hemiptera: Anthocoridae), a predator of many soft-body insects, is an important biological control agent in Asia. Understanding this predator’s egg-laying preferences and a habitat needs is important for its success in pest control. We investigated the plant acceptability and ovipositional preference of O. sauteri for coriander (Coriadrum sativum L., Apiales: Apiaceae), marigold (Tagetes erecta L., Asterales: Asteraceae), sweet alyssum (Lobularia maritima L., Brassicales: Brassicaceae), and alfalfa (Medicago sativa L., Fabales: Fabaceae), and focused on the effects of plant physical and anatomical characteristics on the ovipositional preference of O. sauteri. The results showed that O. sauteri can lay eggs on uninfested plants in the vegetative stage and their eggs hatched normally. Orius sauteri females prefer plants with high stomatal density, a large stomatal area, and fewer trichomes as oviposition hosts, and the depth of egg placement was determined by leaf thickness. Our studies suggested that O. sauteri females can select oviposition hosts and specific oviposition sites by assessing the structural qualities of plant surface. Coriander and marigold are potentially suitable host plants for O.sauteri. The results aid the selection of cover crops to enhance natural enemies in the fields.

Ovipositional Behaviour of Two Fruit Flies, Ceratitis capitata and Anastrepha fraterculus, in Seven Fruit Hosts in the Laboratory

Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) are the most commonly found fruit fly species in fruit crops in Brazil. Both polyphagous species show similar host ranges, but specific knowledge regarding the ovipositional preference of either species is scarce. The present study aims to evaluate, in the laboratory, ovipositional behaviours in seven fruit host submitted to infestation by A. fraterculus and C. capitata. Except for C. capitata in Tahiti acid lime, the number of punctures containing eggs exceeded the number of punctures without eggs. The highest values for eggs per puncture were obtained in Fuyu persimmon, for which averages of 4.06 and 50.09 eggs per puncture were deposited by A. fraterculus and C. capitata, respectively. For A. fraterculus, the infestation ranking, based on the number of eggs per puncture from high to low, was Fuyu persimmon > papaya > Tahiti acid lime > carambola > coffee > guava > sweet orange. For C. capitata, the infestation ranking was Fuyu persimmon > carambola > papaya > guava > sweet orange > coffee > Tahiti acid lime. All punctures made to carambola and papaya contained eggs. Sweet orange exhibited the maximum number of punctures of A. fraterculus without egg deposition. The first day of medfly oviposition in Fuyu persimmon resulted in approximately three-fold more eggs per puncture than the second, third, and fourth days.

Ovipositional preference of potato tuber moth and its damage to different genotypes of potato in free choice condition

Potato tuber moth is a serious pests of potato which cause qualitative as well as quantitative loss on tubers at stores. Major control mechanism is to use chemical pesticide but this pose great hazard risk to the growers and consumers. Therefore this study evaluated tubers of ten potato genotypes viz. CIP 394600.52, CIP 393371.164, Khumal Ujjawal, PRP 296667.2, CIP 393385.39, CIP 395112.32, PRP 226567.2, PRP 0165667.6, CIP 393371.159, and Khumal Upahar against potato tuber moths for their ovipositional preferences and damage potential with nine replication in the laboratory. Number of deposited eggs for four days at eye and outside the tubers on skin, number of tunnel and tunnel length was measured. Least percentage of egg laid eye was least in genotype CIP 394600.52, CIP 393371.164 and variety Khumal Ujjawal respectively. The least number of total eggs laid on eyes was on genotype CIP 394600.52 9 (2.33±1.00) followed by variety Khumal Ujjwal. Although genotype CIP 393385.39 and Khumal Ujjwal was among the most preferred (6.00±2.45) genotype for oviposition, average number of tunnels and average total tunnel length remained very low. Factors such as physical, nutritional, chemical or genetical which may be involved inducing resistance mechanism thus should also be studied and verified.

Oviposition and Development of Anopheles coluzzii coetzee and Wilkerson in Salt Water

Anopheles coluzzii is an important vector of malaria in sub-Saharan Africa particularly of the most dangerous malaria parasite. It completes its life cycle in water and a change in physicochemical properties particularly that of salinity of water may affect egg laying and perhaps the development of eggs to maturity. Studies have shown that climate change may alter the transmission of many vector-borne diseases in different parts of the world and global warming will also raise sea levels which will lead to an increase in saline and brackish water body in coastal areas. This study investigated the salinity tolerance level of An. coluzzii. It involved creation of artificial environments of different salinity gradients using rainwater and sea water and the subsequent exposure of the media to An. coluzzii for laying of eggs and development of larvae to adult. Anopheles coluzzii showed ovipositional preference for less saline media as there was significant negative correlation between number of eggs laid and salinity of oviposition media. Effect of salinity was evident in egg development and larval survival, as no egg hatched in >30% sea water, all L3 larvae died in >40% seawater, and the maximum seawater concentration for L4 survival was 30%. An LC50 of 17.51% (95% CI: 9.31–24.56)% and 23.4% (95% CI: 16.76–22.30)% were calculated for L3 and L4 larvae respectively. Adults emerging from fresh and low saline water of 10% seawater had greater energy reserve than those emerging from 20% and 30% seawater. Increasing salinity did not affect wing length of the emerging adult. Despite the increased stress on larval development, some individuals survived and went on to emerge as adults in conditions that seem to be representative of brackish water. This may imply that an increase in brackish water sites caused by rising sea levels might create more suitable breeding sites for this species.