Number Of Whiteflies Research Articles

Whitefly Detected: Light-Emitting-Diode Traps Enhance Monitoring of Trialeurodes vaporariorum in Greenhouse-Grown Tomato

Yellow sticky traps (YSTs) are common tools for monitoring the greenhouse whitefly (GWF), Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), which can cause significant yield reduction in different greenhouse crops such as cucumber and tomato. In recent years, sticky traps equipped with green light-emitting diodes (LEDs) have also been (successfully) tested for catching GWFs. However, no study has observed GWF population dynamics at low population densities using such LED traps for early pest detection in crop stands. Therefore, a greenhouse experiment was conducted aiming to investigate the correlation between GWF populations on tomato crops (Solanum lycopersicum L. (Solanaceae)) and the numbers caught on yellow sticky traps and green LED traps, respectively. A small number of whiteflies was released into two pest-free greenhouse cabins, and populations on plants and traps were monitored for the duration of two months. The results show that the GWFs caught on LED traps correlate significantly positive with the population density on the tomato crops. Such a correlation was not found for standard YSTs. Moreover, the results indicate the possibility of early pest detection using LED traps. The findings are discussed in the context of the whiteflies’ ecology and population dynamics in greenhouses.

Efficacy of Water Soaked Neem (Azadiarachta indica) Leaf Filtrate on Three Insect Pests on okra [Abelmoschus esculentus (L.) Moench] Plants

This study investigated the efficacy of neem leaf filtrate on three insect pests of okra in a garden at Winneba, Ghana. In this experiment the garden was demarcated into two equal halves where one half was used as the experimental area whereas the other half used as the control area. Filtrate of 500g of neem leaves soaked in 40 litres of pipe born water left for two weeks was used in spraying okra plants in the experimental area while five litres of ordinary water was used to spray the control area. Ten plants from each area were selected and labelled and the number of Aphis (Aphis gosspii), Thrips (Thrips spp.) and whiteflies (Bemisia tabaci) which are common okra insect pests in the area monitored on these plants. Means calculated were compared using t-test and two-way analysis of variance at 0.05 probability. Whiteflies (Bemisia tabaci) were the most abundant (48.53%) and the differences among the total numbers for the three insect pests were significant (P<0.05). There were significant differences among the means for the control and experimental groups (F =110.15, df =1, 36; P<0.05). The findings suggest that neem leaf filtrate was effective in reducing the population of the three insect pests on okra. Therefore, neem leaf filtrate may be useful alternative in controlling Aphis gosspii, Thrips spp. and whiteflies (Bemisia tabaci) on okra.

Spring Abundance, Migration Patterns and Damaging Period of Aleyrodes proletella in the Czech Republic

The cabbage whitefly has become an important pest on brassica vegetables in Central Europe. It does not destroy the affected plants, but the product becomes unmarketable, causing considerable economic losses. The pest is also difficult to control due to its way of life and because it develops resistance to some of the active components of insecticides. In organic farming systems, insecticides are strictly restricted, but neither predators nor whitefly parasitoids are able to keep the pest at a tolerable level. It is, therefore, necessary to become familiar with the whitefly’s life cycle and habits, including mass migration from winter hosts to vegetables. We inspected 44 rapeseed fields across the republic in the period 2014–2021 in order to find the connection between the presence of oilseed rape fields near vegetable growing areas (VGAs) and the abundance of the overwintering cabbage whiteflies. We also conducted regular weekly monitoring of whitefly occurrence in the main cultivation area of the Czech Republic (Polabí) with the aim of specifying critical data important for the successful control of this pest. We found that the cabbage whitefly incidences were many times higher in rapeseed fields close to VGAs compared to areas where the crops are not adjacent. The average number of whiteflies was 0.59 individuals per plant in VGA-1 (oilseed rape grown inside this area or up to 1 km far), 0.052 in VGA-2 (distance 3–10 km from vegetable fields) and 0.014 in VGA-3 (more than 20 km). In the extremely warm year 2016, the difference was up to sixty times. The first CW eggs laid on cruciferous vegetables were usually found around 20 May. The period of mass migration of CW adults to cruciferous vegetables was between 6 June and 2 August. At this time, vegetables are most vulnerable to damage. Successful control of the cabbage whitefly requires the use of fabric netting, combined with an insecticide as needed and trap plants as needed; the latter have to be destroyed before adult whiteflies hatch—typically in early July.

Begomovirus Transmission to Tomato Plants Is Not Hampered by Plant Defenses Induced by Dicyphus hesperus Knight.

Plants can respond to insect infestation and virus infection by inducing plant defenses, generally mediated by phytohormones. Moreover, plant defenses alter host quality for insect vectors with consequences for the spread of viruses. In agricultural settings, other organisms commonly interact with plants, thereby inducing plant defenses that could affect plant-virus-vector interactions. For example, plant defenses induced by omnivorous insects can modulate insect behavior. This study focused on tomato yellow leaf curl virus (TYLCV), a plant virus of the family Geminiviridae and genus Begomovirus. It is transmitted in a persistent circulative manner by the whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), posing a global threat to tomato production. Mirids (Hemiptera: Miridae) are effective biological control agents of B. tabaci, but there is a possibility that their omnivorous nature could also interfere with the process of virus transmission. To test this hypothesis, this study first addressed to what extent the mirid bug Dicyphus hesperus Knight induces plant defenses in tomato. Subsequently, the impact of this plant-omnivore interaction on the transmission of TYLCV was evaluated. Controlled cage experiments were performed in a greenhouse setting to evaluate the impact of mirids on virus transmission and vector acquisition by B. tabaci. While we observed a reduced number of whiteflies settling on plants exposed to D. hesperus, the plant defenses induced by the mirid bug did not affect TYLCV transmission and accumulation. Additionally, whiteflies were able to acquire comparable amounts of TYLCV on mirid-exposed plants and control plants. Overall, the induction of plant defenses by D. hesperus did not influence TYLCV transmission by whiteflies on tomato.

Studies on the transmission of Squash Leaf Curl China Virus causing yellow mosaic and leaf curl disease in pumpkin

Viruses pose a significant threat to pumpkin cultivation, leading to substantial yield losses and reduced fruit quality. Understanding the transmission dynamics and disease progression of Squash Leaf Curl China Virus (SLCCV), a major virus affecting pumpkin, will contribute to developing effective management strategies for this crop. Our study aimed to develop an efficient mechanical inoculation method for SLCCV in pumpkin and investigate whitefly transmission. Mechanical inoculation was assessed using different buffers (I, II, and III) for preparing the viral inoculum. Buffer III, consisting of phosphate buffer, β-mercaptoethanol, and Na2SO3, showed the highest severity of symptoms and incidence of infection in the susceptible pumpkin variety Pusa Vishwas. The summer season was the most favourable for virus transmission, and plant parts such as expanded leaves, middle leaves, and stems exhibited higher infectivity than other parts. A minimum of two whiteflies per plant successfully transmitted the virus to pumpkin plants, resulting in yellow mosaic symptoms and stunted growth. The transmission efficiency increased with an increase in number of whiteflies per plant. A minimum acquisition access feeding period (AAP) of 10 min. and an inoculation access feeding period (IAP) of 24 h were optimal for whitefly-mediated transmission of SLCCV. These findings highlight the importance of vector control strategies, such as insecticides and physical barriers to prevent whitefly-mediated transmission of SLCCV in pumpkin. This is the first report of sap transmission of SLCCV in pumpkin, emphasizing the importance of developing and implementing comprehensive control strategies that address all possible routes of infection.

Plant Growth, Fruit Yield, and Tomato Leaf Curl Disease of High Tunnel Organic Tomato Affected by Shade Net and Plastic Mulch Color

There is an increasing interest in producing organic tomatoes (Solanum lycopersicum) in high tunnels (HTs) in the southeast United States. HTs are unheated, passively cooled structures that allow tomato growers to harvest high-quality fruit out of season. However, excessive temperatures inside HTs may negatively impact tomato plant growth and fruit yield. Shade nets have been reported to reduce temperatures inside the HTs. Plastic mulch color has also significantly influenced plant growth and yield under high-temperature conditions. This study aimed to determine the effects of shade net color and plastic mulch color on plant growth, fruit yield, and incidence of tomato yellow leaf curl disease (TYLC) in ‘Red Snapper’ tomato grown in HTs under elevated temperatures (summer-fall) in southern Georgia, USA. Organic ‘Red Snapper’ tomato seedlings were transplanted in HTs in 2019 (Season 1) and 2020 (Season 2). The design was a split-plot randomized block where the main plots were externally mounted shade nets (black, silver, and unshaded; 30% shade factor), and the subplots were plastic mulches (black and white). Compared with black mulch, white mulch improved plant height and stem diameter but did not influence fruit yields. Shade nets reduced HT air temperature and root zone temperature (RZT) but did not affect plant height and stem diameter. The diminished photosynthetic photon flux density (PPFD) under the shade nets reduced marketable fruit yield. Thus, shade nets are not recommended once heat challenges do not limit HT tomato production in Georgia (after about mid-October). Shade nets and plastic mulch inconsistently affected TYLC incidence, severity, and area under the disease progress curve (AUDPC). Additional fruit yield reductions occurred due to TYLC because the incidence was 100% 6 weeks after transplanting. Preliminary insect data showed that shade net treatments had similar sweetpotato whitefly (Bemisia tabaci) numbers. The high TYLC incidence indicates that ‘Red Snapper’ may not be suitable for fall HT tomato production in the southeast United States. More research on shading and heat stress management in HT organic tomato production is necessary.

Gradual Emergence of East African cassava mosaic Cameroon virus in Cassava Farms in Côte d’Ivoire

Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are endemic threats to cassava production, causing significant yield losses. They are caused respectively by begomoviruses and ipomoviruses that are transmitted by whiteflies and infected cuttings. This study aimed to monitor and characterize viruses responsible for these diseases in order to fill existing gaps in understanding their epidemiology in Côte d’Ivoire. Field surveys were conducted in 2016, 2017, and 2020, and no CBSD symptoms were observed. However, an increase in CMD incidence was noted from 45.95% in 2016 to 51.37% in 2020, while CMD severity remained moderate over the years with a mean value of 2.29. The number of whiteflies was relatively low and decreased over the years. Molecular diagnostics carried out on cassava leaf samples allowed the detection of East African cassava mosaic Cameroon virus (EACMCMV) that occurs in single as well as in mixed infection with African cassava mosaic virus (ACMV). Single EACMCMV infection, which was detected only in three agroecological zones of eastern Côte d’Ivoire in 2016, spread throughout the country in 2017 and became more widespread in 2020 with a preponderance in central and southern zones, whereas ACMV and EACMCMV coinfection has spread to the entire zones. Phylogenetic analysis of the viral isolates showed that they are closely related to those from Burkina Faso, Ghana, and Nigeria. This changing population of cassava virus species constitutes a serious threat to cassava cultivation. Understanding the evolutionary dynamics of these viruses could help in adopting better disease management strategies to control the disease.

Quality and physiological evaluation of tomato subjected to different supplemental lighting systems

Light is a crucial mediator in plants of growth and development, secondary metabolism, and signaling of potentially beneficial phytochemicals. The present study investigated three indoor supplemental light treatments, HPS, LED, and LED+IR, applied during tomato cultivation, in which non-destructive and destructive analyses were performed at two time points to record the physiological responses and effects of these artificial lights on the growth and quality of the produce. An infrared thermometer and thermal cameras were used throughout the experiment to record temperature changes under each growing condition. LED+IR supplemented light showed a decrease in photosynthetic pigments, such as chlorophyll a, b, and carotenoids but induced an increased number of flowers, heavier tomato fruits, enhanced anthocyanins, phenolic index, lipid peroxidation, titratable acidity, and reduced nitrate accumulation. Moreover, higher generated temperatures under LED+IR helped tomato plants to reduce white fly infestation, but suppressed plant height. HPS light performed better than both LED and LED+IR in terms of total sugar accumulation, total carotenoids, water content, plant height, and leaf lipid peroxidation at harvest. Lycopene, ß-carotene, brix index were remarkable under HPS lighting but under the same conditions the number of whiteflies, however, was the highest in HPS among all the tested light treatments. In terms of fruit color analysis, maximum redness (a*), reduced hue angle, and chroma were observed under LED+IR while LED lighting in brightness (L*), and HPS in yellowness (b*) were prominent. However, LED in particular was insufficiently effective in acquiring any possible physiological and qualitative characteristics of tomato plants and fruits for the observed time span of the experiment. Hence, LED+IR has been shown to boost the accumulation of bioactive chemicals, improve fruit quality, promote more rapid and early flowering in tomato plants, and can serve as an efficient replacement for traditional indoor illumination.

Efficacy of Different Neonicotinoids and Bio Pesticides on Okra Against Bemisia Tabaci

The current study was investigated at the Agricultural Research Institute Tarnab, Peshawar during 2020 in a Randomized Complete Block Design (RCBD) with three replications. The study aimed was determining the efficacy of different neonicotinoids insecticides and bio- pesticides against Bemisia tabaci on okra crop. Results revealed that significantly maximum number of whitefly (Bemisia tabaci) population reduction was recorded in imidacloprid (7.55plant-1) treated plot followed by acetamiprid (8.88plant-1) and bio-pesticides (11.99 plant-1) while minimum population reduction was recorded in clothianidin (14.66 plant-1) treated plot over checked plot after 1st application while similar observation was recorded after the 2nd application. In terms of CB ratio, highest CB ratio was recorded by imidacloprid treated plot followed by bio pesticide, acetamiprid and clothianidin while lowest CB ratio was recorded by acetamiprid. Similarly, the research work concluded that overall best performed by imidacloprid after 1st and 2nd application while minimum control was observed by clothianidin treated plot over the control treatment. 
 

Acylsugar tomato lines suppress whiteflies and Amblyseius swirskii establishment

AbstractPlant defense traits such as trichomes along with biocontrol agents may provide alternatives to insecticide use in tomatoes, Solanum lycopersicum L. (Solanaceae). However, plant‐herbivore‐natural enemy interactions are not always complementary. In a series of greenhouse and field experiments, we explored whether augmented defense traits (i.e., production of acylsugars) in tomato plants could reduce sweet potato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), populations and aid the establishment of the predatory mite Amblyseius swirskii Athias‐Henriot (Acari: Phytoseiidae). In the field experiment, commercial tomato cultivars and acylsugar‐producing tomato lines received no predatory mites or mites released via three methods: dusting on top, dusting on bottom, or slow‐release sachets. In the first greenhouse experiment, predatory mites were released onto the commercial and acylsugar‐producing tomato plants via sachets. In the second greenhouse experiment using a similar design, we augmented the mite diet with an alternative non‐prey resource (i.e., cattail pollen). Our results indicated that acylsugar‐producing tomato plants supported significantly fewer whiteflies than the commercial lines in all experiments. However, in the field, despite lower whitefly numbers, Tomato yellow leaf curl virus (TYLCV) (Geminiviridae, Begomovirus) was detected at higher frequencies in acylsugar‐producing lines. Few mites were recovered from all commercial and acylsugar‐producing lines in the field or greenhouse experiments suggesting A. swirskii does not establish well on tomatoes, and acylsugar lines successfully decreased whitefly populations but not a viral disease transmitted even at low whitefly abundance.

Flight activity of invasive Rugose Spiralling Whitefly (Aleurodicus rugioperculatus Martin) and Bondars Nesting Whitefly (Paraleyrodes bondari Perrachi) in coconut orchards

Monitoring and knowing flight activities in whiteflies are key information for applying any management strategies. The adult Rugose Spiralling Whitefly (RSW) flight activity was most intense in the morning after dawn (0600 to 0700 ) when 13.5 numbers were captured in the yellow sticky sheets placed in the Southeast, while there was a minor peak of adult RSW in the evening. The Bondars Nesting Whitefly (BNW) was notably different in both directions; the maximum number of whiteflies was captured in the traps placed in the Southeast between 0600 and 0700 (69 adults), while very few whiteflies were captured in the Northwest. The Bondars Nesting Whitefly flight was quite comparatively low in both directions during the dusk and sunset hours.

Management of sucking pests of capsicum by using botanicals under protected condition

Botanical insecticides are derived from plants and their derivatives. In recent years, there has been a significantgrowth in the use of botanical products for the management of insect pests, which has raised their recognition and marketshare in the global insecticide market. The field efficacy studies revealed that neem oil (3%) was more effective in controllingsucking pests of capsicum viz., Thrips parvispinus (Karny), Polyphagotarsonemus latus (Banks), Aphis gossypii (Glover)and Bemisia tabaci (Gennadius) under protected cultivation. Based on overall observations, minimum thrips and aphidpopulation was recorded in neem oil (3%). The next best treatments in the decreasing order of efficacy were NSKE,pongamia oil and garlic oil. Similarly, neem oil was also found effective and recorded significantly lower number of yellowmites and whiteflies followed by NSKE, garlic oil and pongamia oil. Our results suggested that neem-based products havehigher efficacy, diverse mode of actions such as repellent, anti-feedant, oviposition deterrent and moulting inhibitors as astand-alone management tool for sucking pests and would require integration with other management practices.

Population Dynamics of Insect Pests and Beneficials on Different Snap Bean Cultivars

Snap bean is an important crop in the United States. Insecticides are commonly used against pests on snap bean, but many pests have developed resistance to the insecticides and beneficials are threatened by the insecticides. Therefore, host plant resistance is a sustainable alternative. Population dynamics of insect pests and beneficials were assessed on 24 snap bean cultivars every week for six weeks. The lowest number of sweetpotato whitefly (Bemisia tabaci) eggs was observed on cultivar 'Jade', and the fewest nymphs were found on cultivars 'Gold Mine', 'Golden Rod', 'Long Tendergreen', and 'Royal Burgundy'. The numbers of potato leafhopper (Empoasca fabae) and tarnished plant bug (Lygus lineolaris) adults were the lowest on cultivars 'Greencrop' and 'PV-857'. The highest numbers of adults were found in Week 1 (25 days following plant emergence) for B. tabaci and Mexican bean beetle (Epilachna varivestis); Week 3 for cucumber beetle, kudzu bug (Megacopta cribraria), and E. fabae; Weeks 3 and 4 for thrips; Week 4 for L. lineolaris; and Weeks 5 and 6 for bees. Temperature and relative humidity correlated with B. tabaci, E. varivestis, bee, and predator ladybird beetle populations. These results provide valuable information on the integrated pest management of snap beans.

Succession and population dynamics of major insect pest of tomato in relation to weather parameters in Jabalpur region

The study was carried out at Vegetable Research Farm, Maharajpur, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur during Rabi season 2020-21. The tomato crop in Jabalpur has been found to be affected by whitefly (Bemisia tabaci), fruit borer (Helicoverpa armigera) and leaf miner (Liriomyza trifolii). The whitefly infestation began in the first SMW (vegetative stage) until the crop was harvested. While percent leaf infection of the leaf miner was documented in the 3rd SMW (vegetative stage). The per cent fruit damage of the fruit borer was reported in the 6th SMW (Fruiting stage) and persisted till the harvest of the crop. Relationship between the population of whiteflies and the weather factors showed that the number of white flies and the maximum temperature had a significant positive connection (r=0.560). The percent leaf infested by the leaf miner and maximum temperature had a substantial positive connection (r= 0.571). Percent leaf infestation was shown to have a substantial negative connection with morning relative humidity (r=-0.520) and evening relative humidity (r= -0.693). A significant positive correlation was observed between per cent fruit damage and temperature (maximum temperature (r=0.797) and minimum temperature (r=0.699)). A significant negative correlation was observed between per cent fruit damage of fruit borer with morning relative humidity (r= -0.560) and evening relative humidity (r= -0.697).

Rickettsia Infection Benefits Its Whitefly Hosts by Manipulating Their Nutrition and Defense.

Endosymbionts play an essential role in the biology, physiology and immunity of insects. Many insects, including the whitefly Bemisia tabaci, are infected with the facultative endosymbiont Rickettsia. However, the mutualism between Rickettsia and its whitefly host remains unclear. This study investigated the biological and physiological benefits of Rickettsia infection to B. tabaci. Results revealed that infection of Rickettsia increased the fertility, the survival rate from nymph to adult and the number of female whiteflies. In addition, this facilitation caused a significant reduction in nymphal developmental duration but did not affect percentage rate of egg hatching. Rickettsia infected B. tabaci had significantly higher glycogen, soluble sugar and trehalose contents than Rickettsia negative B. tabaci individuals. Rickettsia also improved the immunity of its whitefly hosts. Rickettsia infested B. tabaci had lower mortality rates and higher semi-lethal concentrations (LC50) when exposed to the fungus Akanthomyces attenuatus and the insecticides imidacloprid and spirotetramat. The percentage of parasitism by Encarsia formosa was also reduced by Rickettsia infection. Overall, Rickettsia infection benefits B. tabaci by improving the nutritional composition of its host, and also protects B. tabaci by enhancing its resistance towards insecticides (imidacloprid and spirotetramat), entomopathogenic fungi (A. attenuatus) and its main parasitoid (E. formosa); all of which could significantly impact on current management strategies.

Management of whitefly, Bemisia tabaci (Gennadius) in bushy Lac host, Flemingia semialata at Thrissur, Kerala

Flemingia semialata is an established host plant of lac insects and is widely grown to promote lac cultivation in India. One of the most destructive pests that can cause significant yield loss in many crops is a sap sucking whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), which is also found to infest the Flemingia sp. They cause vast damage to the host plants during feeding by reducing the rate of photosynthesis through the excretion of honeydew and by transmitting a large number of plant pathogenic viruses. Although there are several methods to control whitefly infestation, the commonly adopted practice is the application of chemical pesticides, owing to their efficiency in whitefly control. This study focused to test the effectiveness of two chemical: Thiamethoxam 25% WG (Actara®) and Phosmet 70 % WP (Imidan®) and an organic pesticide: Neem Oil, in whitefly control on F. semialata. The experimental design consisted of two different concentrations of each pesticide i.e., Phosmet 0.5 ml/L, 1ml/L, Thiamethoxam 0.25g/L, 0.5 g/L, Neem oil 1ml/L, 2ml/L applied on 21 test plants in sets of three and also on three regions of the test plants i.e, upper, middle and lower. The number of whiteflies was counted after 6, 12 and 24 hours of pesticide application. The results revealed that, among all the treatments, Thiamethoxam 0.5mg/L was found to be the most effective with highest percentage of reduction over control in the number of whiteflies in all the time intervals. The leaves in the middle and lower regions of the test plants showed relatively higher loads of whiteflies than those in the upper region throughout the experiment. Although, Neem oil is an environment friendly natural pesticide, Thiamethoxan has negligible volatilization properties and high degradation rates in the soil and therefore could be successfully and safely applied on the lac insect host plants during the pre-inoculation stages to lessen the whitefly attack.

Trunk injection as an alternative approach to insecticide spraying: an experience with cashew trees

Endotherapy is a tactic for phytosanitary products application to trees and palm. The goal of this study was to verify the efficiency of trunk injections in cashew trees to control of whitefly (Aleurodicus cocois) (Curtis, 1846) (Hemiptera: Aleyrodidae). To test this technology were used 17 cashew trees with one trunk or more. The injections were applied in just one trunk in plants with two or more trunks. Two doses of acephate were tested. For each centimeter of trunk diameter were applied 5.4 g or 0.25 g of active ingredient. Immediately before the application of the insecticide and at 1, 6, 9 and 16 months later, 12 mature leaves per plant were collected in the median part of the cashew canopy to count the number of adult whiteflies. There was no significant difference in the number of A. cocois over the months after the insecticide trunk injection in plants with a single trunk. Injections with acephate in cashew tree trunk are effective on whitefly control.

Efficacy of Soil Insecticides Against Sucking Pests of Potato

Field experiments were conducted at three locations for two seasons, 2018 to 2020 to evaluate the efficacy of soil insecticides against sucking pests of potato. Lowest cumulative mean number of whiteflies was observed with fipronil 0.3G @ 25 kg/ ha, and it was on par with its dose of 20 kg/ ha, cartap hydrochloride 4G @ 20 and @ 25 kg/ ha; overall reduction in whiteflies over control ranged between 56.70 and 59.04% at Jalandhar; 53.17 to 60.89% at Modipuram, and 57.33 to 62.40% at Gwalior. Similar trends were noted for aphids, leaf hoppers and thrips. Based on tuber yield and benefit cost ratio, cartap hydrochloride 4G @ 20 kg/ ha (2.62) and fipronil 0.3G @ 20 kg/ ha (2.47) were found to be the most effective against the sucking pests of potato. Hence, both these can be recommended in potato in place of phorate 10G.

Risk factors associated with cassava brown streak disease dissemination through seed pathways in Eastern D.R. Congo.

Vegetatively propagated crops are particularly prone to disease dissemination through their seed systems. Strict phytosanitary measures are important to limit the impact of diseases as illustrated by the potato seed system in Europe. Cassava brown streak disease (CBSD) is a devastating disease caused by two viral species collectively named cassava brown streak viruses (CBSVs). CBSD can cause substantial root yield losses of up to 100% in the worst affected areas and is easily transmitted through stem cuttings. In Eastern and Central Africa, the epidemiology of CBSVs in the local socio-economical context of production remains poorly known while a better understanding would be an asset to properly manage the disease. This lack of information explains partially the limited efficiency of current regulatory schemes in increasing the availability of quality seed to smallholders and mitigating the spread of pests and diseases. This study surveyed the epidemiology of CBSVs in Uvira territory, Eastern D.R. Congo, and its drivers using a multivariate approach combining farmer’s interview, field observation, sampling and molecular detection of CBSVs. Investigation on the epidemiology of CBSD revealed that three clusters in the study area could be identified using five most significant factors: (i) symptoms incidence, (ii) number of whiteflies, (iii) types of foliar symptoms, (iv) cutting’s pathways and (v) plant age. Among the three clusters identified, one proved to be potentially interesting for seed multiplication activities since the disease pressure was the lowest. Through risk assessment, we also identified several key socio-economic determinants on disease epidemy: (i) factors related to farmer’s knowledge and awareness (knowledge of cassava pests and diseases, knowledge of management practices, support from extension services and management strategies applied), (ii) factors related to the geographical location of farmer’s fields (proximity to borders, proximity to town, distance to acquire cuttings), as well as (iii) the pathways used to acquire cuttings.

Effects of photo-selective netting in Summer Beefsteak Tomato (Solanum lycopersicum L.) cultivation on the environmental conditions under nets as well as growth and yield

Located in a subtropical zone, Taiwan has intense summer sunlight that affects beefsteak tomato cultivation. In this study, beefsteak tomatoes were grown net-house under photo-selective netting of different colors to investigate netting performance. A significantly higher photosynthetic photon flux density (PPFD) was observed under the 24-mesh white (W24) and 24-mesh pink (H24) netting. A difference between the four net-house was only observed for wavelengths of 500–599nm. In 32-mesh blue (B32), the red to blue (R/B) and red to far-red (R/FR) ratios were significantly lower across canopies. The photosynthetic capacity of photosystem II of leaves in W24 was the lowest among the four treatments. In all four, fruit growth was relatively low under the impact of high temperatures, with the lowest single fruit weight and the smallest number of fruits per plant observed in W24. In H24 and 24-mesh pink (HH24), the yield per plant was significantly higher. Significantly fewer whiteflies were observed in the netting houses in H24, HH24, and B32 than in W24. However, the netting still failed to prevent high temperatures at noon. In H24 and HH24, the amount of light retained in the canopies was greater, the photosynthesis capacity was unchanged, the fruit yield was greater and the number of whiteflies in the netting houses was significantly lower. Therefore, pink netting is recommended for beefsteak tomato cultivation.