Trap Crop Research Articles

Using trap crops to manage plant parasitic nematodes on vegetable crops

Using trap crops to manage plant parasitic nematodes on vegetable crops

Irrigated trap crops impact key hemipteran pests in organic pistachio orchard

Using sown groundcovers as trap crops to protect a cash crop is a traditional pest management tool. Pistachio is a major crop in California’s Central Valley, where high summer temperatures and little to no precipitation between May and November lead to summer dry-down of annual groundcover. Hemipteran pests that consist of ‘small bugs’ and ‘large bugs’ are a major contributor to nut damage, especially in organic production. In this 2-year field study, we tested the use of irrigated trap crop mixtures, sown between tree rows, to reduce those hemipteran pests’ abundance or damage. Biweekly beat samples of the tree canopy and sweep samples of the sown groundcovers in trap crop plots and resident weedy vegetation in control plots were taken over two consecutive growing seasons. Arthropod richness and abundance were highest in the groundcover and tree canopy in the trap crop plots. Small and large bug pest populations were higher and lower, respectively, in the tree canopy in trap crop plots, indicating a mixed response of these hemipterans to the presence of the trap crops. Additionally, natural enemy populations were more abundant in the tree canopy in trap crop plots than in control plots. There was no difference in nut damage between plots with and without the trap crop. These findings suggest that populations of hemipteran pests and beneficials can be manipulated successfully with irrigated trap crops, but future studies will need to focus on doing so in a way that decreases hemipteran pistachio damage.

Population dynamics of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) and its populations on different planting dates and host plant species

The greenhouse whitefly (GWF), Trialeurodes vaporariorum (Westwood), is a cosmopolitan pest of horticultural crops. The study purpose was to assess the GWF adult population dynamics on potato and its populations on different planting dates and different host plant species. A survey was conducted to determine the GWF population on potato and its associated abiotic factors from January to December 2019. Four crop species, common bean (Phaseolus vulgaris), tomato (Lycopersicon esculentum), potato (Solanum tuberosum), and chili (Capsicum annum) were planted in two field experiments with different planting dates (7 April and 10 July). The results showed that during high rainfall, the GWF densities were very low. However, as the rainfall declined, the population increased and reached its peak in August. Again, when the rain started in September, the population drastically dropped and continuously declined as the rainfall increased until the year-end. The rainfall rate negatively correlates with the GWF population, but there was no significant correlation between temperature and the insect population. Populations of GWF adult, egg, and nymph were significantly higher in planting date 2 than in planting date 1. On both planting dates, the GWF populations on common bean were significantly higher than those on the other host plants. Hence common bean is the potential to be used as a trap crop in potato or chili plantations. Further studies are necessary to develop efficient and effective ways of utilizing bean as a trap crop.

How to pit weeds against parasitic plants. A simulation study with Phelipanche ramosa in arable cropping systems

Branched broomrape (Phelipanche ramosa (L.) Pomel) is a parasitic plant, which causes severe yield losses in major crops worldwide. Due to its broad host range, including numerous non-parasitic weed species, the persistence of its seeds in the soil, and the poor efficiency of available management techniques, broomrape management is complex. In a previous paper, we developed a broomrape-dynamics model called PheraSys to support the design of management strategies combining multiple techniques aiming at long-term control of broomrape. Here, the objective is to use this simulation model to (1) check the consistency of simulations vs. literature data, (2) evaluate the potential of cropping systems to manage the combination of branched broomrape and weeds, (3) investigate whether weeds can biologically regulate parasitic plants in agroecosystems. Five contrasting cropping systems including different levers known to influence broomrape dynamics were simulated with different weather series. Four simulation series were run, with or without broomrape as well as with or without weeds, to discriminate the individual effects of weeds and broomrape on crop production as well as the effect of weeds on broomrape dynamics. Simulations with PheraSys showed that delayed sowing in combination with the use of trap and catch crops are promising for reducing broomrape infestation and yield losses in the long term. Tolerating a temporary and/or low-density weed flora in such cropping systems could improve broomrape management because spring/summer weeds could reduce broomrape seed bank by triggering broomrape germinations that would not reproduce. During cash-crop growth, weed contribution to broomrape infection would be negligible. However, these conclusions are only valid if broomrape-attaching weeds reproduce before broomrape has time to do so, which needs to be checked with field experiments for most weed species.

Potential roles of selected forage grasses in management of fall armyworm (Spodoptera frugiperda) through companion cropping.

Production of maize, Zea mays L. (Poaceae), in sub‐Saharan Africa is threatened by a new invasive pest, fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). To mitigate this threat, push–pull companion cropping, a system originally developed for management of lepidopteran stemborers, may be used to control FAW. The original system involved trap crops that functioned as a ‘pull’ component to attract moths away from the main crop. How grass species can be used as trap crops in a push–pull system to control FAW is a question that remains to be answered, because maize is already a highly preferred host plant. Therefore, we tested oviposition preference of FAW female moths in no‐choice and two‐choice experiments and larval performance on six selected grasses (Poaceae) to assess their roles as trap crop ‘pull’ plants in the system. In no‐choice tests, numbers of eggs deposited on Brachiaria brizantha (Hochst. ex A. Rich.) R. Webster cv. ‘Piata’, cv. ‘Mulato II’, and cv. ‘Xaraes’, and Napier grass (Pennisetum purpureum K. Schumach) cv. ‘South Africa’ were not statistically different from those deposited on maize. In two‐choice tests between grasses and maize, there were no significant differences in number of eggs laid when the plants were of the same size. However, in two‐choice tests with maize plants half of the size of the grasses, significantly more eggs were laid on B. brizantha cv. Xaraes and P. purpureum cv. South Africa than on maize, suggesting that crop phenology could make a difference. Numbers of larvae arrested on grass leaf cuts were considerably lower than those on maize leaf cuts after 48 h. In two‐choice tests with maize, molasses grass (Melinis minutiflora P. Beauv.) was the only grass that was significantly preferred to maize for larval settlement after 24 h. After 48 h in the two‐choice test, it was the only grass that retained larvae, although the larval count was significantly lower than on maize. Our data show that none of the grasses tested were strongly preferred to maize, but the results indicate plants attractive to FAW adults and larvae that could be utilized in a multiple trap crop approach to target various stages of the pest. Furthermore, results indicate the importance of planting these companion plants earlier than maize.

Coastal and Marine Pollution in Bangladesh: Pathways, Hotspots and Adaptation Strategies

Marine and coastal pollution is a global issue for human health and biodiversity. We have investigated pollution sources, flow patterns, hotspots, challenges, and adaptation policies in Bangladesh. Industries, ship breaking yards, sewage, tourism, and transboundary depositions are the main sources of pollutions. The Ganges, Padma, Jamuna, Brahmaputra and Meghna carry wastes to the Bay of Bengal. Pollution hotspots are Dhaka, Gazipur, Narshingdi, Narayanganj, Chittagong, Khulna, Mongla port and Sylhet city. Textile and dyeing industries discharge 12.7–13.5 million m3 waste waters annually and pollute 20% of fresh water. Ship breaking yards dump about 22.5 tons polychlorinated biphenyls in a year. More than 50% of the marine oil pollution comes from urban activities. Plastic wastes at 3000 t day-1 and tourism are also contributing to the coastal pollution. Effluent releasing standards are not maintained, and thus higher concentrations of heavy metals are found with marine fishes. Use of heavy metal tolerant crops (rice: BRRI dhan47, potato: Cardinal, mustard: Brassica napus, flower: Marigold, vegetables: Cucumber, fibre: Kenaf, and so on), trap cropping, deep placement of fertilizers, integrated rice-fish-duck culture, etc can be adopted in polluted areas. There are laws for environmental issues, but coordination and financial capabilities does not warrant its effectiveness. Necessary steps are to be taken to improve infrastructure to ensure sanitation and benign discharge of industrial effluents. Systematic study on sources, fate and extent of current effluents dumping in water ways need to be assessed for wellbeing of aquatic life and human health.

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

Simple SummaryThe tomato fruitworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), is a destructive polyphagous insect pest of tomatoes and its control largely depends on chemical pesticides. However, indiscriminate use of chemical pesticides has resulted in the development of resistance and posed serious environmental problems. Alternatively, in search of environmentally friendly pest management techniques, the use of trap crops has recently gained more attention. In this study, we compared different accessions of S. viarum to investigate which of them have the highest potential as a dead-end trap crop for H. armigera. Results from the laboratory experiment showed a significant variation among the S. viarum accessions in terms of H. armigera oviposition, and exhibited a higher level of resistance against H. armigera larvae compared to the tomato plants. Under the semi-field condition, trap cropping of S. viarum significantly reduces the total egg-laying of H. armigera on tomato. This study provides important information about the abilities of S. viarum plants to influence the life parameter of H. armigera and highlighted the possibilities to use S. viarum as a dead-end trap crop for the management of H. armigera. However, the efficacy of S. viarum needs to be tested under large, open-field conditions. 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.

Phytoene desaturase-silenced citrus as a trap crop with multiple cues to attract Diaphorina citri, the vector of Huanglongbing

Huanglongbing (HLB) is one of the most destructive diseases in citrus worldwide. Unfortunately, HLB has no cure and management relies on insecticides to reduce populations of the vector, Diaphorina citri Kuwayama (Hemiptera: Liviidae). We propose an attract-and-kill strategy using a trap crop as an alternative to vector control to reduce transmission of the pathogen, ‘Candidatus Liberibacter asiaticus’. We evaluated vector response to phytoene desaturase-silenced citrus trees using virus-induced gene silencing technology. Citrus tristeza virus (CTV) was used to produce a phytoene desaturase-silenced citrus (CTV-tPDS) that expresses visual, olfactory, and gustatory cues to attract D. citri. We found that D. citri were more attracted to CTV-tPDS plants with noticeably better fecundity and overall population fitness than on control plants. Moreover, rearing D. citri on CTV-tPDS plants significantly increased their survival probability compared with those reared on control plants. CTV-tPDS plants possessed reduced content of both carotenoid and chlorophyll pigments resulting in a consistent photobleached phenotype on citrus leaves which provided a sufficient close-range visual attractant to stimulate D. citri landing. Additionally, CTV-tPDS plants exhibited an enriched profile of volatile organic compounds (VOCs), which offered adequate olfactory cues to attract psyllid from long-range. Finally, CTV-tPDS plants exhibited an enriched metabolite content of phloem sap and leaves which offered appropriate gustatory cues that influenced probing/feeding behavior. We believe that introducing CTV-tPDS plants (as a trap crop) to D. citri-infested orchards will attract and congregate psyllids to facilitate their removal from the target crop with insecticides or by other means. This new strategy could be deployed relatively quickly and economically to HLB-impacted citrus industries. Moreover, it is an eco-friendly strategy because it should partially reduce the input of chemical insecticides ameliorating the indirect cost of HLB infection.

Powdery mildew (Erysiphe cruciferarum) evaluation on oilseed rape and alternative cruciferous oilseed crops in the northern Baltic region in unusually warm growing seasons

ABSTRACT The pathogen Erysiphe cruciferarum is an increasingly serious threat to cruciferous oilseed crops worldwide. In the present study, the severity of powdery mildew was evaluated on spring oilseed rape (Brassica napus) and five alternative oilseed crop species (B. juncea, B. nigra, Sinapis alba, Raphanus sativus, Eruca sativa). The main aim of the study was to identify plant species that are less susceptible to powdery mildew for possible application as cover crop, in trap cropping or seed production. Powdery mildew assessments were conducted in two growing seasons that were characterised by unusually warm and dry conditions for northern temperate climatic conditions. In both growing seasons, a heavy powdery mildew infection (over 80%) was recorded on B. napus and B. nigra plants, indicating that E. cruciferarum is an important pathogen for oilseed crops in northern Baltics. However, three other cruciferous species S. alba, E. sativa and R. sativus showed full resistance to powdery mildew, and thus, even under strong powdery mildew pressure, they can be cultivated without pesticide application in northern Baltic conditions. We suggest that in changing climatic conditions powdery mildew is expected to become a more serious problem in cruciferous oilseed crops in northern Europe, especially under intensive short-rotation farming practices.

Olfactory Response of Plutella xylostella (Lepidoptera: Yponomeutidae) Adults to Refugia Plant

Selection of refugia plants is an important step when engineering the agroecological system. The refugia plants can be repellent or attractant to insect pests and in many species the role of each plant can be studied using the olfactory responses of the insect to volatile chemical cues emitted by the plant. The objective of this study was to determine the olfactory response of Plutella xylostella (Lepidoptera: Yponomeutidae) adults to several refugia plant candidates. Y-tube olfactometer tests were used to determine responses of P. xylostella to candidate plant species including: Ageratum conyzoides, Galinsoga parviflora, Synedrella nodiflora, Sphagneticola trilobata, Brassica rapa, Rorippa indica, Arachis pintoi, Ocimum basilicum, Apium graveolens, and Portulaca oleracea. Olfactory choice tests were conducted to compare preferences of insect. The results showed that R. indica, G. parviflora, and S. trilobata flowers attracted P. xylostella. R. indica and B. rapa leaves had high attractiveness for P. xylostella adults. At the same time, the A. graveolens, A. conyzoides, and O. basilicum leaves showed potential repellency. The conclusions of this study are R. indica and B. rapa have potential for use as trap crops, while A. graveolens, O. basilicum, and A. conyzoides have potential as repellent plants. Further study is necessary to test the olfactory response of P. xylostella’s natural enemies to these refugia plants.

ECOLOGICAL/CULTURAL MEASURES OF WEED MANAGEMENT FOR SUSTAINABLE AGRICULTURE

The weed is a plant that grows where it is undesired or in its place. Weeds are unwanted plants that are not known to be economically important. Weeds are plants that are unwanted in a given situation and may be dangerous, harmful or economically detrimental. Weeds have serious problems when it comes to agricultural production. It is estimated that weeds generally cause a 25% loss of agricultural production in the least developed countries, a 10% loss in the least developed countries and a 5% loss in most developed countries. Weeds loses are depend upon location, crop and types of soil. The study found that potential yield losses were significant for soybeans (50-76%) and peanuts (45-71%). Largest variability in potential yield losses were observed among locations in case of direct seeded rice (15-66%) & maize (18-65%). In similar cases weeds are reduced 66% yield of Chilly and the loss of N through weeds is about 150 kg per ha. Weeds losses alone in 10 major crops of India viz transplanted rice (13.8%), wheat (18.6%), direct-seeded rice (21.4%), mustard (21.4%), sesame (23.7%), sorghum (25.1%), maize (25.3%), Pearlmillet (27.6%), Greengram (30.8%), soybean (31.4%) and groundnut (35.8%). Weed control practices are extremely important to Indian agricultural production. Many more tools and practices are adopted for crop protection q like crop species, crop variety/cultivars, sowing of crop (time, rate of sowing, row spacing and method), crop rotation, trap and catch crops, cropping practice, irrigation time & method are suitable practices under cultural/ecological measures of weed management. Cropping practices are also known as environmentally responsible weed management practices. Environmentally sound weed management methods are chemical-free and weed management tools-free.

Management methods for marmorated stink bug (Halyomorpha halys [Stål, 1855], Hemiptera, Pentatomidae)

The brown marmorated stink bug (Halyomorpha halys (Stål, 1855); [Hemiptera, Pentatomidae]) is an invasive, alien and polyphagous insect species native to East Asia. It was introduced to the United States in the mid-1990s and to Europe in 2004. Today it is present in most European countries. In new environments, it adapts quickly and reproduces successfully, developing at least one complete generation per year. With the growth of populations, it is becoming a disturbing factor in the urban areas and recently one of the most dangerous pests in agricultural production. It was first discovered in Slovenia in 2017 in Šempeter near Gorica. In less than two years, it spread to the entire territory od Slovenia and began to cause damage to agricultural production. In a review paper, we have collected research by foreign and domestic researchers related to the study of different ways of controlling the brown marmorated stink bug. The article presents chemical methods of control, the use of insecticide nets, the use of attractants and repellents, trap crops, as well as methods of biotic protection using predators and parasitoids.

A Mechanistic Approach To Assessing the Potential for Cover Crops To Serve as Trap Crops for the Soybean Cyst Nematode

The effects of cover crops on the biology of the soybean cyst nematode (SCN; Heterodera glycines) are not well established. It is possible that cover crops may reduce SCN population densities by acting as trap crops. Cover crops with potential to serve as trap crops may stimulate hatching and/or attract hatched SCN juveniles and also may be penetrated by large numbers of nematodes that cannot feed. Experiments were conducted to determine whether root exudates (REs) and soil leachates (SLs) from various cover crop plants affected SCN hatching and chemotaxis and if there were significant differences in SCN juvenile root penetration among different cover crop plant types. In 14-day-long hatching experiments, there was greater SCN hatching in crimson clover (Trifolium incarnatum) REs and SLs than in REs and SLs from all other cover crop treatments in the experiments. No other cover crop REs and SLs significantly affected hatching. In chemotaxis experiments, SCN juveniles were attracted to REs and SLs from annual ryegrass (Lolium multiflorum) and cereal rye (Secale cereale) after 24 h. In greenhouse experiments, significantly more SCN juveniles penetrated the roots of single cultivars of crimson clover, mustard (Brassica juncea), and rapeseed (B. napus) than 11 other cover crop species/cultivars evaluated in the experiment over the course of 20 days. Few SCN juveniles penetrated the roots of annual ryegrass and cereal rye. The results suggest that crimson clover, grown as a cover crop, has the most potential to act as a trap crop for SCN. Cover crop plants may affect SCN biology in ways other than the mechanisms investigated in these experiments.

Trap Cropping Harlequin Bug: Distance of Separation Influences Female Movement and Oviposition.

To evaluate perimeter trap crops for management of harlequin bug, Murgantia histrionica (Hahn), we undertook greenhouse and field experiments with mustard greens as trap crop for a collard cash crop. We confirmed that harlequin bugs prefer to immigrate to and reside on mustard. Females, however, in greenhouse cage experiments, 'commuted' to collards to lay their eggs. In separate spring and fall field plantings, using replicated 12 m by 12 m collard plots in 1-ha fields, we tested mustard planted as an adjacent perimeter trap crop, or a perimeter trap crop separated by 2 unplanted rows (2.3 m), or with no trap crop. Adults accumulated on the spring mustard crop but overall numbers remained low, with all collards sustaining <1% leaves damaged. In the fall, the separation of 2.3 m reduced oviposition on collards fourfold, and feeding damage approximately 2.5-fold, compared to collards with an adjacent trap crop. Fall control plots with no border trap crop showed even lower foliar damage; likely result of preferential immigration of harlequin bugs to mustard at the field scale, resulting in fewer bugs near the control treatment plots. Thus, the spatial arrangement of the mustard trap crop, and its separation from the cash crop, influences pest abundance and damage. A separated mustard border can reduce bug movement including female commuting and egg-laying, thus better protecting the collard cash crop. Future research should address reduction in area of trap crops, deployment of semiochemicals, and possible changes in timing, to promote trap cropping that is practical for grower implementation.

Sunflower Metabolites Involved in Resistance Mechanisms against Broomrape

Several strategies have been proposed to control parasitic plants and these include biological control, the use of herbicides, and suicidal germination or trap crops. In the case of sunflower, the most effective solution is genetic resistance. Nevertheless, the use of resistant cultivars is followed by the appearance of new and more virulent races of the parasite that overcome the existing sources of resistance. For this reason, it is necessary to increase our knowledge of the mechanisms involved in the resistant varieties. In this study, the presence of compounds involved in pre-attachment resistance mechanisms in sunflower varieties was analyzed. The production of stimulators of the germination of parasitic plant seeds and the concentration of the haustorial elongation inhibitor, scopoletin, were measured in exudates of resistant and susceptible sunflower varieties. It was found that dehydrocostuslactone and orobanchyl acetate are not involved in the resistance of the sunflower varieties studied. The results demonstrate that costunolide, heliolactone, and scopoletin are related to sunflower resistance. The sunflower varieties studied do not use all available options to fight parasitic plants. This could be one of the reasons that sunflower resistance is rapidly overcome by broomrape.

Polyphagous caterpillars of Spodoptera litura switch from a trap crop to the main crop, improve fitness, and shorten generation time

Trap crops are used for pulling the pest load from the main crops toward themselves. Here, we report a switching by a polyphagous pest, Spodoptera litura, from trap crop castor to main crop eggplant during its mid-larval development. In the eggplant–castor mixed field, adults oviposit exclusively on castor. However, 3rd and 4th instar castor-grown larvae migrate to eggplants. Host choice assays for adults and larvae conducted in the controlled environment and the nutritional indices of castor and eggplant-feeding larvae revealed that the natural enemies did not influence the host switch. The host switch was rather associated with larvae’s enhanced digestion and metabolism. It shortened the development time and increased the eclosion success on eggplant. Mother-selected castor is suitable for the early instars and eggplant is for the later instars, indicating that the host switching was not because of the mother’s erroneous host choice but has evolved as an advantageous behavior. S. litura’s ability to switch hosts in the same ontogenic phase and reduce the generation time can contribute to an additional generation within a cropping season and endanger the critical growth stage of fruiting. Our findings support the ‘mother knows the best’ concept and annex that the larvae can also possess the ability to know the best. Such ability in different ontogenic stages can be fundamental to the exceptional adaptability of species like S. litura.

Host plant penetration, development and life cycle of a Heterodera schachtii population from the Western Cape province, South Africa

Heterodera schachtii (Tylenchida: Heteroderidae), also called the sugar beet cyst nematode, are of economic importance worldwide. Oilseed rape (Brassica napus L.), which is a crop of global importance, suffers yield loss when it is infected with H. schachtii. The first report of the occurrence of H. schachtii in South Africa was made in 1968 on the Greater Cape Flats of the Western Cape province of South Africa, showing the widespread occurrence and the high nematode numbers on cabbage, cauliflower, beetroot and Brussels sprouts. The penetration, development and life cycle of a local H. schachtii population on seven vegetables (beetroot, broccoli, Brussels sprout, cabbage, cauliflower, lettuce and turnip) and three weeds (black nightshade, purslane and shepherd’s purse) commonly grown, or found, in the Greater Cape Flats region of the Western Cape, South Africa, and two candidate trap crops (white mustard and oilseed radish) were examined under laboratory conditions. All the vegetables and weeds were found to be good hosts of H. schachtii, with the exception of lettuce, which was found to be a non-host. Oilseed radish and white mustard allowed penetration and some nematode development, but no, or little, cyst formation. Female bodies filled with eggs were observed from 31 to 34 days after inoculation onwards on all the vegetables and weeds, except for on beetroot, on which female bodies filled with eggs were observed a few days later. The results from this study are important, especially in terms of the adaptation of vegetable crop rotation cycles that are practised on the Cape Flats, so as to prevent the build-up of H. schachtii populations in agricultural settings.

Oviposition Preference of Bactrocera dorsalis Hendel (Diptera: Tephritidae) on Different Fruit in Snake Fruit Orchard

The oriental fruit fly Bactocera dorsalis (Hendel) is an important pest of snake fruit (Salacca zalacca) in Sleman District. Due to the high level of damage by the fruit flies, it is necessary to do. The aim of this research was to find out suitable fruit traps, by testing the oviposition preferences of the fruit flies in the orchard to lay eggs on several types of fruit. The research was done in snake fruit orchard located at Sleman Yogyakarta and owned by farmers, while the Lab works were done at the Laboratory of Entomology, Department of Plant Protection, Faculty of Agriculture, Universitas Gadjah Mada. All researches were done between April-June 2019. Guava (Psidium guajava), watery rose apples (Syzygium aqueum), starfruit (Averrhoa carambolae), and snake fruit (Salacca zalacca) were used as trap crops. Each fruit, with the same maturity level, was hung 1.5 m above the ground for 4 days with 12 days total trapping at intervals of 3 times. After the test, each fruit was taken and the insects in it were reared in the laboratory. The number of pupae and flies that emerged from each fruit was counted and compared. The results showed that in the orchard 1 as well as 2, of guava fruit produced the highest number of (151 pupae) followed by salak (94 pupae), star fruit (83 pupae), and water guava (2 pupae). The finding of seeds shows that guava fruit is the most suitable host for the fruit flies to be used in the trapping, followed by star fruit and watery guava.

Ovipositional responses of Spodoptera frugiperda on host plants provide a basis for using Bt-transgenic maize as trap crop in China

Spodoptera frugiperda, the pest fall armyworm (FAW), is widespread in more than 100 countries. To date, planting insect-resistant transgenic crops is one of the main control methods in its native countries. In this study we evaluated Bt-transgenic maize (Bt maize) and non-transgenic (conventional) maize and six other host plants in greenhouse pot experiments and field trials for oviposition preference by the Chinese populations of FAW. In laboratory trials, female moths preferred to oviposit on maize with no significant preference between conventional and Bt maize. However, after conventional and transgenic maize were exposed to FAW larvae and damaged, oviposition was significantly higher on transgenic maize than on the conventional one. Field trials showed that for plants less damaged at an early stage (seedling stage), oviposition of FAW on transgenic and conventional maize was significantly higher than that on wheat, sorghum, foxtail millet, peanut and soybean while showing no significant difference between transgenic or conventional maize. FAW adults mainly laid eggs on Bt maize, while the larval density and leaf damage rating or percentage of damaged plants were significantly lower than on conventional maize. Larval density and its damage on conventional maize were significantly higher than that on Bt maize and the other five hosts. Thus, maize is a highly preferred and suitable host for S. frugiperda feeding and ovipositing, and Bt maize can be used as trap crop to protect other crops.

The role of Desmodium intortum, Brachiaria sp. and Phaseolus vulgaris in the management of fall armyworm Spodoptera frugiperda (J. E. Smith) in maize cropping systems in Africa

BACKGROUNDThe fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is a serious pest of maize. Farming systems such as push‐pull or maize‐legume intercropping have been reported to reduce FAW infestations significantly. However, the exact mechanisms involved in FAW management have not been practically elucidated. We therefore assessed larval host preference, feeding and survival rate when exposed to four host plants commonly used in push‐pull and legume intercropping. We also compared adult moths' oviposition preference between maize and other grasses used as trap crops in push‐pull.RESULTSThe larval orientation and settlement study showed that maize was the most preferred host plant followed by bean, desmodium and Brachiaria brizantha cv Mulato II. The larval arrest and dispersal experiment showed that mean number of larvae was significantly higher on maize than on Desmodium or B. brizantha cv Mulato II. However, no significant differences were found between maize and bean after 24 h. Maize was the most consumed plant, followed by bean, desmodium and finally brachiaria. The mean percentage of survival to the pupation stage was significantly higher on maize. The study on FAW oviposition preference showed no significant differences in egg deposited between maize and other grasses. However, B. brizantha cv Xaraes, which received more eggs than maize, could be a promising alternative to B. brizantha cv Mulato II for the control of FAW.CONCLUSIONThe study provides a better understanding of the mechanisms involved in the control of fall armyworm under the push‐pull and maize legume intercropping. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.