Population dynamics of whitefly, Bemisia tabaci (Gennadius), as influenced by weather conditions infesting Bt cotton hybrid

To quantify the effect of different sowing environments and weather conditions on incidence of whitefly on cotton, experiments were conducted at PAU Regional Research Station, Bathinda during kharif 2014-2017) with Bt cotton hybrids 'NCS-855 BGII' at normal and late sowing. The mean incidence of whitefly was ranged from 0.0–39.5, 11.2–124.0, 0.2–26.4 and 0.7–15.5 adults/leaf during 2014, 2015, 2016 and 2017, respectively. The maximum adult population of whitefly was recorded in month of August almost in all the years, having its peak between 31–34 standard meteorological weeks (SMW). Among years, whitefly population was negatively correlated with rainfall, morning and evening relative humidity, while positively correlated with maximum temperature (except 2014) and minimum temperature (except 2014 and 2017). Moreover, bright sunshine showed positive correlation with whitefly population. In respect of pooled data, whitefly population showed negative correlation for minimum and maximum temperature and rainfall, while, positive correlation with morning and evening relative humidity and bright sunshine hours. Overall, crop sown at normal date was less affected by infestation of whitefly than late sown crop. So, this information would be helpful in developing efficient pest management strategies on cotton crop in order to get good harvest.

Role of Aleyrodidae Entomophages in agrobiocenosis in type content and management in Uzbekistan

This article identified the entomophagous species that are constantly feeding on alfalfa, and identified 27 species of entomophagous predominant species belonging to 7 families of entomophagous species of alfalfa pests. It was observed that these are the families Neuroptera, Aphelinidae, Syrphidae, Coccinellidae, Anthocoridae, Nabidae and, Miridae. According to the ratio of entomophages, the most populous families were identified as goldflies (Shrysopidae), khan beetles (Coccinellidae), and wild caterpillars (Miridae). Their populations formed diversity. Studies have been conducted on the use of parasite encarcation parasites in the management of whitefly population. It has been used in a variety of consumption norms against leachate in open and closed conditions. Encarsia (Encarsia partinopea Masi) was used to control the amount of whitefly (Trialeurodes vaporariorum) in greenhouse conditions. In the greenhouse conditions, 87.9% biological efficiency was achieved on day 28 after the application of encarcation in a 1:10 ratio in cucumber crops, and by the end of the season, parasitic entomophages were effectively controlling the amount of whiteflies. After 24 days of application in a 1:10 ratio in cucumbers planted in the open, the biological efficiency reached 83.5%. At 30 days after application, 86.5% biological efficacy was maintained.

Evaluation of whitefly population and weather effect of cassava mosaic incidence on commonly grown cassava in Benue State, Nigeria

Vector population and weather are critical in virus disease incidence and could be strategic for its management in agriculture. To investigate the influence of whitefly population and weather on Cassava Mosaic Disease (CMD) in cassava, TMS 419 and TME 30572, commonly grown in the state were planted. The varieties were laid out in Randomized Complete Block Design in four replicates and left to natural infection by CMD viruses. At two weeks after planting and fortnightly, whitefly population counts were taken, CMD incidence was estimated and severity scored on 5- point scale. Daily temperature, humidity, wind speed and wind direction were obtained as secondary data. Data were analysed using ANOVA at p=0.05. Whitefly population (18/plant) was significant (P≤0.05) in the first 30 days at 26.9-27.1oC, 42% humidity, 10 Km/hr wind speed and when the wind direction was in the East or North-East. The vector population then declined until the end of experiment. Cassava mosaic incidence changed with whitefly population, humidity and wind speed. Disease incidence in cassava plots was low (3.6%). TME30572 maintained lower disease incidence (3.0%) and severity (2.0) during the study. R2 indicated that 27, 42 and 57% of whitefly population could be explained by temperature, humidity and wind speed, respectively while 4% of the disease incidence could be explained by the whitefly population. The number of CMD infected plants peaked (4%) when population of whitefly was 18/plant, above which the disease reduced at 0.0017 rate per unit change in the vector population. Mosaic disease incidence in cassava plots was influenced by vector population as conditioned by the weather. Keywords: Bemisia tabaci, Cassava, Cassava Mosaic Disease, Nigeria, Weather, Whitefly vector

Whitefly Abundance on Rooted Poinsettia Cuttings and Finished Poinsettias

In this study, we surveyed the initial whitefly (Aleyrodidae) populations on rooted poinsettia (Euphorbia pulcherrima) cuttings at two commercial greenhouse facilities in both 2017 and 2018 to determine the initial whitefly population at the beginning of poinsettia production and surveyed finished poinsettias at multiple retailers in Tyler, TX, over 2 years to determine whitefly densities considered acceptable by retailers. The initial whitefly population (mean ± se) for all poinsettias was 0.02 ± 0.02 (2017) and 0.33 ± 0.13 (2018) nymphs per plant for grower facility A and 0.05 ± 0.05 (2017) and 0.02 ± 0.01 (2018) nymphs per plant for grower facility B. Of the total 2417 rooted poinsettia cuttings inspected at both locations over 2 years, 29 cuttings had whitefly nymphs (1.2%), 18 had pupae (0.7%), and 23 had exuviae (1.0%). On finished poinsettias sampled at retailers, 4.38 to 40.38 immatures (nymphs + pupae) per plant were found within 60 seconds for any given retailer over the 2 years. We found poinsettias with as many as 220 immatures and 32 adults on a single plant at retailers. This study is the first to quantify densities of whiteflies at retail stores over multiple years.

Role of Barrier and Intercrops in the Management of Mungbean Yellow Mosaic Virus (MYMV) Disease in Jharkhand, India

Field trials were carried out during 2018-2019 and 2019-2020 autumn seasons to study the role of barrier and intercrops against whitefly - borne Mungbean yellow mosaic virus (MYMV) disease. In the treatment (T2) two rows of Maize sown after 15 rows of Mungbean, the lowest mean population of whitefly 7.03 per plant was recorded which was followed by 7.42 whitefly per plant in the treatment (T4) with two rows of Sorghum after 15 rows of Mungbean. In barrier crops, the lowest disease incidence of 28.94% was recorded in the treatment (T2), two rows of maize after 15 rows of Mungbean. The mean seed yield recorded was 6.75 q/ha. The treatment (T2), two rows of Maize after 15 rows of Mungbean was recorded to be effective in the management of MYMV disease. The lowest mean whitefly population of 4.71 per plant was recorded in the above treatment, Mungbean sown with Maize in 4:2 ratio. Mungbean sown with Maize in 4:2 ratio was recorded to be efficacious in the management of MYMV disease. The results indicated that the barrier crop of maize interfered with the movement of vector whiteflies.

Optimum Time for Harvesting Cassava Tubers to Reduce Losses Due to Cassava Brown Streak Disease in Northeastern DRC

The present study aimed to determine the appropriate time to harvest cassava tuberous root which minimize the losses due to cassava brown streak disease (CBSD) in the region of Yangambi, DRC. To achieve the aim of the study, 38 cassava cultivars were evaluated in Yangambi INERA’s Research Center for CBSD in the roots at harvest time between 9 and 13 months after planting (MAP). All the 38 cultivars tested showed CBSD root necrosis symptoms. Foliar symptoms occurred on 37.6% of the evaluated cultivars while CBSD root necrosis varied significantly among cultivars (7.0% to 82.5%) depending on susceptibility and the age of plant. This indicates the differential response of the cultivars to CBSD infection. Whitefly population density decreased with age of cassava, it was of 3 whiteflies per plant (9 MAP) to 1 (10 MAP). We noticed that in older plants, whitefly population decreased from 1 at 11 MAP to none at 13 MAP. Although, some cultivars did not show CBSD symptoms up to 12 MAP, they were not necessarily less attractive to whitefly. Negative relationship (r = -0.08 and r = -0.25) has been found between whitefly number and foliar symptom severity or between whitefly and tuber necrosis severity. Beyond 12 MAP, CBSD necrosis (severity score 4) was present in the tubers of 3 cultivars (EUR/2011/0148, Yafelamonene and Ybi/2011/258). Our study shows that in order to mitigate the losses due to CBSD necrosis, the optimum harvesting time for cassava tubers in Yangambi is 9 MAP.

Direct and Indirect Effect of Myzus Persicae Infestation on Buildup of Whitefly (Bemisia tabaci) in Tomato Crop under Laboratory Conditions

The tomato crop is affected by a number of pests in the world as well as in China and Pakistan. The whitefly (Bemisia tabaci) is considered a very serious and damaging pest of tomato crop along with many other vegetables and field crops. Population buildup of whitefly is affected by many factors, including biotic and a biotic. One of the factors affecting the whitefly population in the tomato crop is green peach aphid (Myzus persicae) infestation before the whitefly attack. This project designed to note the direct and indirect effect of Myzus persicae infestation on the population setup of whitefly in tomato crops. The results revealed that whitefly prefers tomato plants without having aphids on them (choice) and can be settled on the tomato plants also when there are aphids present (no choice). The period after aphid infestation have a negative effect on the whitefly population, and the density of aphids/leaf has also influenced the whitefly population.

An Ecological Assessment of Isaria fumosorosea Applications Compared to a Neonicotinoid Treatment for Regulating Invasive Ficus Whitefly

A pilot study was conducted on a weeping fig, Ficus benjamina shrub hedge in a Florida urban landscape to determine the efficacy of a fungal biopesticide, PFR-97™ which contains blastospores of Isaria fumosorosea, and a neonicotinoid treatment (Admire Pro™) applied against the invasive ficus whitefly pest, Singhiella simplex (Singh). Post treatment, an ecological assessment of the study was conducted by observing the impact of the fungal biopesticide and neonicotinoid treatment on natural enemies, e.g., predators, parasitoids and enzootic fungal pathogens occurring in the whitefly-infested hedge. Both treatments provided a significant reduction in the whitefly population compared to control and were compatible with the natural enemies present. Various natural enemies including fungal entomopathogens were identified associated with the whitefly population infesting the weeping fig hedge. The parasitoids, Encarsia protransvena Viggiani and Amitus bennetti Viggiani & Evans combined parasitized a similar mean number of whitefly nymphs in both treatments and control; however, the number parasitized decreased over time. Natural enzootic fungi isolated from the ficus whitefly nymphs were I. fumosorosea, Purpureocillium lilacinum and Lecanicillium, Aspergillus and Fusarium species. Results from this pilot study suggest there is much potential for using repeated applications of the fungal biopesticide, PFR-97™ as a foliar spray compared to a neonicitionid as a soil drench for managing S. simplex on Ficus species for ≥28 days.