Trap Crop Research Articles

The Effects of Some Different Cultural Techniques on the Transmission and Infectious Development of Pepper Yellow Leaf Curl Indonesia Virus on Red Chili

<p>An experiment is conducted to investigate the effects of cultural techniques on pepper yellow leaf curl disease caused by <em>Pepper yellow leaf curl Indonesia virus</em> (PepYLCIV). The investigation is conducted in the area where the disease has been endemic and <em>Bemisia tabaci</em> is abundant. Four cultural techniques are applied in separate lands and cannot interfere with each other. The methods applied are seed treatment, intercropping, trap cropping, and physical barrier. Seeds harvested from infected plants are used for seed treatment experiments, and local farmers use commercial sources for other experiments. The results confirmed that PepYLCIV was a seed-borne virus affected by hot water treatment at 65<sup>o</sup>C for 30 minutes. Turmeric crude extract could reduce the incidence and severity of the disease. The tomato is a better intercrop than eggplant, mung bean, and soybean in reducing disease incidence, but their effects on disease severity and yield reduction were not significantly different. Basil and marigolds were better barrier crops compared to cosmos and zinnia. A 125 cm high physical barrier using 50 mesh cheesecloth could reduce the disease incidence, but not the lower ones. Under different cultural techniques, PepYLCIV causes a 40.00–52.32% chili yield reduction.</p>

Intercropped Flemingia macrophylla successfully traps tea aphid (Toxoptera aurantia) and alters associated networks to enhance tea quality.

The tea aphid, Toxoptera aurantia is a destructive pest causing severe damage to the quality and yield of tea, Camellia sinensis. Relying on chemical insecticides to control this pest causes adverse ecological and economic consequences. Trap plants are an eco-friendly alternative strategy to mitigate pest damage on focal plants by attracting target insects and natural enemies. Yet, the utilization of trap plants in tea plantations remains limited. Besides, the effects of the trap plant on the tea aphid-ant-predator community and tea quality and yield are unknown. Intercropped Flemingia macrophylla successfully trapped tea aphids and enhanced the complexity of aphid-ant-predator networks over three consecutive years compared to monoculture management. Moreover, F. macrophylla significantly increased the abundance of natural predators by 3100% and species richness by 57%. The increasing predators suppressed the aphid population and hampered its spillover to neighbouring tea plants. Consequently, F. macrophylla improved tea quality by an 8% increase in soluble sugar and a 26% reduction in polyphenols to amino acids ratio. The study illustrated that F. macrophylla is a suitable trap crop for tea aphid control in tea plantations. This legume increases species nodes and strengthens multiple connections in aphid-associated communities through its cascade effects, improving tea quality. These findings shed light on the potential application of trap plants in tea plantations as an efficient integrated pest management (IPM) strategy. © 2023 Society of Chemical Industry.

Effects of cover crops on hatching of and root penetration by Heterodera glycines

Summary The use of non-host cover crops can be a viable strategy for managing soybean cyst nematode (SCN) Heterodera glycines. Cover crops may affect SCN biology and reduce populations by acting as trap crops that promote the hatching and/or penetration by second-stage juveniles (J2) without supporting their development. Two growth chamber experiments were conducted to assess ten cover crops for their impacts on SCN hatching and penetration into the roots. For each experiment, with four replications per treatment, crops were planted in naturally-infested soil in two separate sets to be harvested 15 and 30 days after planting (DAP). SCN susceptible soybean ‘Barnes’ and non-planted natural soil (fallow) were used as controls. Faba bean ‘Petite’, a non-host of SCN, induced the greatest hatching among the cover crops and was statistically similar to soybean. Winter rye ‘ND Dylan’ also induced significant hatching compared to fallow. Root staining revealed that the highest number of J2 penetrated the faba bean roots at 15 DAP, followed by soybean and winter rye. While J2 penetrated all tested crops, they completed their development to become adult females only in soybean and turnip. Soybean cyst nematode development to adult females did not occur in faba bean, and the number of SCN inside the faba bean roots 30 DAP was significantly lower than at 15 DAP and also lower than in soybean. These results suggest that the faba bean affects SCN biology and has the greatest potential to act as a trap crop for managing SCN.

Effect of Trap Cropping of Brassica juncea (Linn.) on the Management of Lipaphis erysimi (Kalt.) on B. oleracea var. capitata (Linn.)

During the rabi of 2022-23, Indian mustard cv. Laha 101 was used as a trap crop to manage the mustard aphid, Lipaphis erysimi (Kalt.) on cabbage cv. K-1. The results showed that trap cropping ratios significantly lowered aphid densities compared to the sole crop (cabbage). The lowest density of aphids (4.60 aphid/plant) was recorded in cabbage under the trap cropping ratio of 3:2. On the other hand, the peak infestation (19.05 aphid/plant) occurred on the mustard of the same trap cropping ratio (3:2) when compared with other trap cropping ratios on 7th SMW (February 11th). Even though the sole crop (cabbage) had the highest aphid density (28.13 aphid/plant), it yielded 49.23 t/ha and had a benefit cost ratio of 2.07 due to two sprays of insecticide (Malathion 50 EC), which was not done in the trap cropping ratios. Thus, the trap cropping ratio of 3:2 (2.31) had the best cost benefit ratio followed by the trap cropping ratio of 1:1 (2.19), which recorded produce of 42.61 t/ha and 41.29 t/ha respectively. Overall, the use of Indian mustard cv. Laha 101 has been shown to be effective as a trap crop in managing mustard aphid on cabbage cv. K-1 during the rabi season. By using the correct trap cropping ratio, farmers can maximize their produce while minimizing the use of insecticides, which can be beneficial both economically and environmentally.

Recent Advances in the Genetic and Biochemical Mechanisms of Rice Resistance to Brown Planthoppers (Nilaparvata lugens Stål)

Rice (Oryza sativa L.) is the staple food of more than half of Earth’s population. Brown planthopper (Nilaparvata lugens Stål, BPH) is a host-specific pest of rice responsible for inducing major losses in rice production. Utilizing host resistance to control N. lugens is considered to be the most cost-effective method. Therefore, the exploration of resistance genes and resistance mechanisms has become the focus of breeders’ attention. During the long-term co-evolution process, rice has evolved multiple mechanisms to defend against BPH infection, and BPHs have evolved various mechanisms to overcome the defenses of rice plants. More than 49 BPH-resistance genes/QTLs have been reported to date, and the responses of rice to BPH feeding activity involve various processes, including MAPK activation, plant hormone production, Ca2+ flux, etc. Several secretory proteins of BPHs have been identified and are involved in activating or suppressing a series of defense responses in rice. Here, we review some recent advances in our understanding of rice–BPH interactions. We also discuss research progress in controlling methods of brown planthoppers, including cultural management, trap cropping, and biological control. These studies contribute to the establishment of green integrated management systems for brown planthoppers.

Trait-based cropping of brassicaceous plants: Effects on ecosystem services and crop yield

Diversification of agroecosystems through mixed cropping can facilitate multiple ecosystem services that may improve yields. Intercrops may repel pests and nourish natural enemies while trap crops lure pests away from target crops. A small-scale agricultural field experiment was conducted in 2018 and 2020 in Finland to study how intercropping of brassicaceous plants and faba bean (Vicia faba) affects yield and quality of a target crop (white cabbage (Brassica oleracea var. capitata)), herbivory on the target crop, and effects of the insect communities linked to the observations. The study was conducted with five different plot arrangements in each year. Broccoli (Brassica oleracea var. italica) or turnip (Brassica rapa var. rapa) were located at the perimeters of 6 × 6 m plots as trap crops. They were planted either alone or with yellow rocket (Barbarea sp). Faba bean was planted as an intercrop in the most complex designs. Cabbage head fresh weight was greatest in the most complex plot type, which included cabbage, broccoli, yellow rocket and faba bean and the head weight was significantly greater than in the cabbage monocrop or the plots with a broccoli-only trap crop. Turnip was included in the experiment in 2020 and efficiently attracted flea beetles and pollen beetles. In 2020, the turnip trap crop alone and the most complicated designs with broccoli or turnip combined with yellow rocket and faba bean significantly reduced P. xylostella abundance in the middle of the plot. Possibilities to use trait-based cropping systems in white cabbage production are discussed.

Assessment of Trap Crops for Management of Thrips, T. tabaci in Tomato

The prospect of four trap crops viz., marigold, okra, sunflower and brinjal were evaluated for their efficiency against thrips, T. tabaci at SASRD, Medziphema, Nagaland University. The study was conducted in Split Plot Design with four treatments having three replications. Tomato was grown on two different planting geometries i.e. 90 x 70 cm (P1) and 60 x 60 cm (P2) and the treatments used as trap crops were indicated as marigold (T1), okra (T2), brinjal (T3) and sunflower (T4), while confining a ratio of main crop to trap crop at 4: 1.The trap crops were transplanted first following the pattern of sequential trap- cropping. Thrips infestations were recorded from the early vegetative stage of tomato and decline in population as the crop matured. All trap crops in the present study showed good performance in the management of T. tabaci. The planting geometry, P2 with okra as a trap crop was observed to be reasonably effective in curbing thrips population in the study period.

Volatiles of the trap crop sunflowers: Effects on the behaviour of adult female Conogethes punctiferalis moths

AbstractSunflowers (Helianthus annuus) are potential trap crops to attract the yellow peach moth (Conogethes punctiferalis) in orchards but the volatile compounds released from sunflowers and their effects on C. punctiferalis behaviour are not clear. Here we used solid phase micro‐extraction to collect volatiles released from flower disks of sunflowers, identified them by gas chromatography–mass spectrometry, and examined the attractiveness of some of the compounds to mated female adult C. punctiferalis moths in Y‐tube olfactometer choice tests. We detected nine volatile compounds (α‐Pinene, β‐Phellandrene, Camphene, β‐Pinene, 3‐Carene, D‐Limonene, Eucalyptol, γ‐Terpinen, and Valencene) with consistently large peak areas for α‐Pinene and β‐Phellandrene. Among tested volatiles, both α‐Pinene and β‐Phellandrene were attractive to C. punctiferalis in olfactometer tests but this was only significant for higher concentrations of β‐Phellandrene. This suggests that β‐Phellandrene may promote C. punctiferalis oviposition on sunflower disks. This study provides insights into volatile chemical mediated responses of insect herbivores to trap crops.

Immigration of Lygus spp. (Hemiptera: Miridae) and predaceous natural enemies to trap-cropped organic strawberry.

Lygus spp. are polyphagous pests that overwinter in weedy vegetation. In the spring on the central coast of California, Lygus spp. emigrate from weeds into strawberry fields. Subsequent feeding on strawberry flowers causes fruit deformation that precludes sale on the fresh market. Use of alfalfa (Medicago sativa L.) (Fabales: Fabaceae) as a trap crop has been hypothesized to prevent Lygus spp. colonization in strawberries. We examined the movement of Lygus spp. and associated predators from weeds to strawberry fields with alfalfa trap crops using a protein mark-capture technique. Insects and spiders were collected from weeds, strawberry, and alfalfa 1 day, 2 days, and ~2 wk after an albumin protein mark was applied to weeds bordering strawberry fields. For marked Lygus spp. that emigrated from weeds, the majority (79%) of adults were recovered from alfalfa trap crops; however, all nymphs immigrated to strawberry. Most protein-marked predators immigrated to strawberry, rather than trap crops, resulting in a marked predator-to-Lygus spp. ratio of 5:1. Trap cropping effectively reduced the colonization of Lygus adults in strawberry. Converting weedy areas to native perennial plantings could further mitigate the risk of pest migration, while simultaneously conserving beneficial insects.

Influence of time of introduction and proportion on the efficacy of grain amaranth trap crop against Aulacophora foveicollis and Epilachna chrysomelina on cucumber (Cucumis sativus L.)

A field experiment was conducted in the early and late planting seasons, 2019 to evaluate the effectiveness of grain amaranth (Amaranthus cruentus L.) planted at different timing and proportion as a trap crop for reducing insect pest densities on cucumber. Amaranth was established into cucumber plots two weeks before cucumber (2WBC), same day (SD) with cucumber or two weeks after cucumber (2WAC) in 100:0, 100:25, 100:50, 100:75 and 100:100 cucumber-amaranth proportions. Amaranth planted 2WBC or SD trapped significantly higher numbers of Aulacophora foveicollis and Epilachna chrysomelina compared to 2WAC, corresponding to lower infestations and damage on cucumber, with the highest fruit yield at SD cucumber. While leaf damage was reduced by 68–74% at 100:100, yield increase of 66–69% was obtained at 100:50 relative to sole cucumber plots. Hence, planting grain amaranth SD with cucumber at 100:50 cucumber-amaranth proportion has a great prospect against insect pests of cucumber in a trap–cropping strategy.

Screening candidate plant species as trap and catch crops for the control of broomrape (Phelipanche mutelii) in rapeseed (Brassica napus)

Broomrapes (Orobanche and Phelipanche species) are parasitic weeds that infect crops. To evaluate crops that can reduce broomrape damage as a trap or catch crop, two experiments were conducted for three years (2018–2020) under greenhouse conditions. The results showed that the tested crops were classified into three groups. The first group was non-hosts of P. mutelii, including cotton, garlic, flax, and cowpea. The second group of crops acted as catch crops and was parasitized by P.mutelii, including faba bean, annual red clover, mung bean, and hairy vetch. Among the catch crops, hairy vetch had the highest percentage of P. mutelii reduction in shoot numbers and dry biomass by 81% and 85%, respectively. Also, the highest percentage increase in shoot and root dry biomass was achieved by 70% and 79% in rapeseed-hairy vetch rotation. The third group was berseem clover which acted as a trap crop and stimulated.P. mutelii seed germination without supporting parasitism. If berseem clover is sown as a trap crop in rotation with rapeseed infested by P. mutelii, it can reduce shoot numbers and dry biomass of broomrape by 70% and increase the dry biomass of aerial parts and roots of rapeseed by 62% and 60%, respectively.

Allium leafminer (Diptera: Agromyzidae) host preference: implications for developing a trap cropping strategy.

Allium leafminer (Phytomyza gymnostoma Loew) is an emerging invasive pest of Allium crops and has been threatening Allium crop production in the eastern United States since its introduction in 2015. Phytomyza gymnostoma can cause substantial economic loss in leek crops when late instars tunnel into the lower portion of the plant, which often renders the crop unmarketable. With limited management tools that are cost-effective and practical, especially for leeks produced in organic systems, we examined the attractiveness of other Allium crop species that might be considered in a trap cropping strategy. In 2021 and 2022, controlled environment choice tests and field trials were conducted to evaluate host preference of P. gymnostoma among Allium crop species including chives, scallion, an onion and scallion hybrid, and leek. We also assessed preference of P. gymnostoma for scallions that varied in size/age. Results from field trials indicated that only chives had more oviposition marks, cumulative numbers of eggs, and a higher density of P. gymnostoma larvae and pupae than leeks. Larger/older scallions had more oviposition marks and higher P. gymnostoma densities than smaller ones in controlled environment choice tests, but this size/age preference was not evident in field trials. Based on our findings, chives could be considered as a potential trap crop for minimizing P. gymnostoma damage in leek crops.

Integration of augmentative biocontrol with synthetic pesticides and other control methods for IPM – Challenges and prospects*

The importance of augmentative biological control and chemical control, and the need and scope for integrating these, rather than dismissing them as incompatible, so as to create a win-win situation for both are highlighted. Besides the judicious use of chemicals and periodical releases of parasitoids/predators, other options such as insect-resistant transgenic crops, host plant resistance, botanical insecticides, sex pheromones, trap crops, pest resistance management, new product development, regulatory measures, etc., should also be exploited, as appropriate to a given situation, so as to develop an Integrated Pest Management (IPM) package. The practicality of such an IPM is explained, citing Bt cotton as an example. It is reiterated that IPM is the most prudent approach for sustainable crop production and protection with the major emphasis being laid on biological control and other eco-friendly methods as indicated by the latest global trend.

Effect of short-term growth of mung bean and its incorporation with nitrogen fertiliser on the density of the root-knot nematode, Meloidogyne incognita, in soil

Summary Soybean is attacked by multiple plant-parasitic nematodes and the major ones are soybean cyst nematode (SCN) and root-knot nematodes. Our previous study reported that 2 weeks growth of mung bean and its soil incorporation markedly reduced SCN density in soil via hatching stimulation by mung bean residue. This study aimed: i) to evaluate whether incorporation of mung bean in combination with N fertiliser decreased the density of Meloidogyne incognita, which attacks both soybean and mung bean; and ii) to determine the direct effect of ammonium solutions on M. incognita J2 and hatching. The results showed that after the growth period of mung bean for 2 weeks and 4 weeks of its incorporation, the density of M. incognita was significantly reduced by 54 and 72% in the mung bean treatment with and without N fertiliser (140 mg N (kg soil)−1), respectively, compared with the control. Soil urease activity was significantly higher in the mung bean with N fertiliser than in the control. Meloidogyne incognita second-stage juveniles were less mobile in NH4Cl solutions with 100-250 mg N l−1 than in 0 mg N l−1. Moreover, NH4Cl solutions with 140 mg N l−1 and 250 mg N l−1 significantly inhibited the hatching of M. incognita. This study demonstrated that 2 weeks growth of mung bean may be a potential trap crop for M. incognita and N metabolism might be involved to a certain extent in the suppression of M. incognita.

Discovery of strigol synthase from cotton (Gossypium hirsutum): The enzyme behind the first identified germination stimulant for Striga

Societal Impact StatementParasitic witchweeds (Striga species) pose a serious threat to food security in Africa, attacking cereal grains and legumes. Chemicals released from the host roots that initiate the life cycle of Striga are known as germination stimulants, predominantly strigolactones (SLs). Strigol, the first identified SL, was isolated from the root exudates of cotton (Gossypium hirsutum), a false host of Striga, over 50 years ago. The identification of strigol synthase in cotton establishes the complete biosynthesis pathway of this emblematic SL. This discovery has the potential to advance our understanding of SL‐mediated rhizosphere interactions and enhance cotton's effectiveness as a trap crop.

Economic Analysis of Integrated Striga Management for Striga control as Influenced by Trap Crops and Inorganic Fertilizer Application in Sorghum [Sorghum bicolor (L.) Moench] at Fedis District, Eastern Ethiopia

Strigais problematic weed causing difficulty in cultivation of sorghum in areas of eastern hararghe where low and erratic rainfall is prevalent and soils are characterized by poor fertility. Knowing these different options of management has been tried however; its cost benefit has never been studied. Therefore, to assess its economic analysis and effect of integrated Striga management on Striga incidence, a field experiment was conducted during the cropping season of 2015 on heavily Striga-infested field in Fedis District, Boko site to determine the effect of trap crops (cowpea, soybean, desmodium, control) and N fertilizer rates (0, 46, 92 and 138 kg N ha-1) on management of Striga incidence and its economic analysis. The experiment was laid out in a factorial arrangement in a randomized complete block design (RCBD) with three replications. Trap crops were uprooted at maximum above ground fresh biomass. The results indicated significant (P<0.05) main effects of trap crop on emergence of Striga where the lowest (26%) Striga emergence of about was recorded over the control with use of cowpea.Striga count at harvest of sorghum was significantly (P< 0.05) affected by the interaction effect of trap crop and N fertilizer where 46 kg N ha-1 and use of cowpea as trap crop reduced the number of Striga seed bank by about 52.3% over the control treatment. The partial budget analysis also showed that the highest(47998.8 Birr ha-1) net benefit was obtained with the use of cowpea as a trap crop and 46kgN ha-1 application. Thus, the use of cowpea as trap crop and 46 kg N ha-1was found to be promising both agronomical and economically

Trap crop selection and economic threshold based ecological management of Spilosoma obliqua Walker (Lepidoptera, Arctiidae) for sesame

The stage-specific life table and nutritional ecology of a Spilarctia obliqua (Walker) along with respective economic thresholds (ETs) on four different crops such as sesame (Sesamum indicum), castor (Ricinus communis), jute (Corchorus capsularis) and sunflower (Helianthus annuus) were studied during 2020-2022. The feeding and population dynamics of S. obliqua were significantly affected by the hosts in terms of host suitability or susceptibility (sunflower>jute>castor>sesame). The ET of S. obliqua on sesame (40.59±2.12 pests m-2 area) was significantly (F3,8=4.72, P=0.031) higher than the other crops (sunflower<jute<castor). Subsequently, the three most suitable hosts (sunflower> jute>castor) were tested in a multi trap cropping system for sesame as main crop in a specific pattern depending on respective susceptibility. Data from the model trap cropping (without pesticide) supported minimum infestation of S. obliqua and other pests along with more predators on sesame with higher benefit cost ratio (BCR) and more (11.82%) carbon sequestration (CS) in same area relative to monoculture (with pesticide) of sesame. It supports pesticide free high production and better CS than sole culture of sesame for climate smart agriculture.

Bioecology and Management of Major Insect Pests of Rice in West Bengal

West Bengal is considered a large producer state of rice in India with an output of nearly 55.48% of total crop production of Bengal. In West Bengal, rice has grown in three different cropping seasons such as Aus (autumn rice), Aman (winter rice) and Boro (summer rice), contributing about 20.69% to the total net State Domestic Product (SDP). Rice production in West Bengal hampered by many biotic stresses mostly by stem borers [Scirphophaga incertulas (Walker, 1863), Sesamia inference (Walker, 1856), Chilo polychrysus (Meyrick, 1932), Chilo suppressalis(Meyrick, 1863)] leaf folder [Cnaphalocrocis medinalis (Guenee, 1854)], plant hoppers [Nilaparvata lugens(Stal, 1854), Sogatella furcifera (Horvath, 1899)], leaf hoppers [Nephotettix virescens (Distant, 1908), Nephotettix nigropictus (Stal, 1870)], rice hispa [Dicladispa armigera (Olivier, 1808)], rice bugs [Leptocorisa acuta (Thunberg, 1783), Leptocorisa oratorius (Fabricius, 1794), Brevennia rehi (Lindinger, 1943)], gall midge [Orseolia oryzae (Wood-Mason, 1889)], etc. Demographic parameter has shown that rice pests are greatly affecting rice host either caused directly by creating dead heart (DH), hopperburn, onion leaf, silver shoot during different stages of harvesting or by indirectly transmitting grassy stunt virus (RGSV), rice ragged stunt virus (RRSV), rice tungro viruses (RTV), rice tungro bacilliform virus (RTBV) etc. resulting 9.5% production loss. For minimize the infestation farmers use different rice varieties which provide resistance effect in pest population. For controlling rice pest population farmers mostly use chemical insecticide [e.g. fipronil, acephate, fipronil, monocrotophos] which exhibit good results against rice pests. Beside those other techniques including using biological and biochemical pesticides [neem oil, karanj oil, mahua oil, conidial suspension of M. anisopliae], pheromones [(Z)-11-hexadecinal, (Z)-9-hexadecenal], allomones [5: 1 mixture of 2-(E)-octenyl acetate and octanol 3-octenal], cultutal methods [synchronized planting, using of trap crop etc.] are effective for controlling rice pests. The population ecology based sustainable management of such pest species will support E 3 strategy [Ecosystem service-based ecological engineering for ecological pest management (ESS-EE-EPM)] of pest management for successful cultivation of rice in the near future.

Control of Globodera pallida Using Brassica juncea Seed Meal Extract and the Trap Crop Solanum sisymbriifolium.

Globodera pallida, the pale cyst nematode, is a regulated potato pest which is economically detrimental. Restrictions on use of the soil fumigant methyl bromide, and lack of resistant russet type varieties for US markets have led to investigations of alternative strategies to control this pest. The efficacy of Brassica juncea seed meal extract (SME) (0, 0.14, 0.28, 0.56, 1.12, and 2.24 t/ha) was studied, either alone or in combination with the trap crop Solanum sisymbriifolium under greenhouse and field conditions. The impact of the application of SME pre- or post-planting of S. sisymbriifolium was also determined. Solanum sisymbriifolium only induced hatch of G. pallida and significantly fewer (up to 57 and 55% in pre- and post-plant experiments, respectively) encysted eggs remained at termination of the experiment compared to the untreated control. However, when SME was applied pre-plant, the encysted eggs remained unchanged which may indicate that SME inhibited egg hatch in the presence of S. sisymbriifolium. When applied individually, S. sisymbriifolium in all experiments, or SME at all rates tested in greenhouse and 0.56 t/ha or higher rates of SME in the field significantly reduced the viability, hatch, and reproduction of G. pallida. Combined treatment with S. sisymbriifolium and SME at lower rates, 0.14 t/ha for pre-plant or 0.56 t/ha or less for the greenhouse post-plant experiment further reduced G. pallida egg hatch than each strategy alone. In the field, a combination of S. sisymbriifolium and SME at 1.12 t/ha or less reduced G. pallida more effectively than SME alone. SME alone applied at higher rates of 0.56 and 1.12 t/ha in pre-plant greenhouse trials, whether combined with S. sisymbriifolium, eliminated G. pallida reproduction. Under field conditions, SME applied at a rate of 1.12 t/ha highly reduced G. pallida reproduction compared to the untreated control by 97% and 61% in 2019 and 2020, respectively. Furthermore, reproduction of G. pallida was eliminated when SME was combined with S. sisymbriifolium. Our results indicated that a combination of SME and S. sisymbriifolium reduces the amount of SME needed to control G. pallida and further decreases the potential reserve of the viable population remaining after individual treatment with each strategy.

Effect of Cowpea Trap Crop on the Control of [Aphis gossypii (Glover)] in Zimbabwean Cotton

Cotton aphids are major cotton pests causing significant yield losses of more than 65% in Zimbabwe. Field experiments to investigate the effectiveness of cowpea as a trap crop in reducing aphid pressure on cotton were conducted over three seasons 2010/11 to 2013/14 at Cotton Research Institute (CRI) in Kadoma, and Umguza in Matebeleland North, in Zimbabwe. Incidence of aphid predators on sole cotton, cotton intercropped with cowpea trap crop and the trap crop itself were also assessed. The measurements were aphid scores, aphid predator counts in both sole cotton, intercropped cotton and cowpea trap crop. Seed cotton yield was measured. Aphid scores and predator counts were subjected to Analysis of Variance (ANOVA) using GenStat 14th Edition software. The square root transformation [x + 3/8] was used for scores or counts not normally distributed. At CRI Cowpea trap crop significantly controlled aphids in intercropped cotton better than chemical control using Acetamiprid 20 SP (P< 0.05). Coccinellid grubs (ladybird beetle larval) populations were highest in cowpea trap crop. At Umguza poor germination of cowpea resulted in highest Coccinellid adults (ladybird beetle adults) in intercropped cotton. Yield of intercropped cotton was comparable to yield from plots where Acetamiprid 20SP was used as a standard practice. Farmers can adopt this technology of aphid control in cotton using commercial cowpea variety CBC 3 as cotton aphid trap crop.