Fitness costs of laboratory-selected imidacloprid resistance in the brown planthopper, Nilaparvata lugens Stål

Imidacloprid has been used as a key insecticide to control the brown planthopper, Nilaparvata lugens Stål, for several years, but no obvious resistance has been identified in field populations as yet. To evaluate the risk, a field population was collected and selected with imidacloprid in the laboratory. After 37‐generation selection a strain with 250‐fold resistance had been successfully achieved. Fitness analysis by constructing life tables demonstrated that resistant hoppers had obvious disadvantages in their reproduction. The fitness of highly resistant hoppers had decreased dramatically (0.169 and 0.104) to only one‐fifth to one‐tenth of that of the susceptible strain. Hence it was concluded that the brown planthopper had the potential to develop high resistance to imidacloprid but that the lower fitness of resistant hoppers could result in a quick recovery of sensitivity when the population did not come into contact with imidacloprid. This means that a reasonable resistance management programme with less imidacloprid use may efficiently delay or even stop resistance development. Copyright © 2006 Society of Chemical Industry     

Development of a monoclonal antibody to detect predation of the brown planthopper Nilaparvata lugens (Stål)

A monoclonal antibody (McAb), 4B8, was developed to whole homogenates of the brown planthopper, Nilaparvata lugens (Stål), using hybridoma technology. It reacted with all the stages of BPH but did not cross-react with other insects and predator species tested with an indirect enzyme-linked immunosorbent assay (ELISA). Immunodiffusion revealed it to belong to the IgG₃ subclass. The ascites developed with 4B8?cell lines had high absorbance values until it was diluted over 6.5536?×?10⁷ times tested by indirect ELISA. It could recognize the BPH proteins after one female was ingested by Pardosa pseudoannulata for about 2.13 days at 25°C. The results of extended antigen detection period and the high specificity of the antibody indicated that 4B8 could be used to study interactions between planthoppers and their predators in the field. Application of the McAb to assess relative importance of four major spider species in subtropical rice ecosystem showed that P. pseudoannulata was more important than Ummeliata insecticeps, and those were more important than Tetragnatha sp. and Coleosoma octomaculatum.     

Susceptibility to neonicotinoids and risk of resistance development in the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

BACKGROUND: In recent years, outbreaks of the brown planthopper, Nilaparvata lugens (Stål), have occurred more frequently in China. The objective of this study was to determine the susceptibility of N. lugens to neonicotinoids and other insecticides in major rice production areas in China. RESULTS: Results indicated that substantial variations in the susceptibility to different insecticides existed in N. lugens. Field populations had developed variable resistance levels to neonicotinoids, with a high resistance level to imidacloprid (RR: 135.3–301.3‐fold), a medium resistance level to imidaclothiz (RR: 35–41.2‐fold), a low resistance level to thiamethoxam (up to 9.9‐fold) and no resistance to dinotefuran, nitenpyram and thiacloprid (RR < 3‐fold). Further examinations indicated that a field population had developed medium resistance level to fipronil (up to 10.5‐fold), and some field populations had evolved a low resistance level to buprofezin. In addition, N. lugens had been able to develop 1424‐fold resistance to imidacloprid in the laboratory after the insect was selected with imidacloprid for 26 generations. CONCLUSION: Long‐term use of imidacloprid in a wide range of rice‐growing areas might be associated with high levels of resistance in N. lugens. Therefore, insecticide resistance management strategies must be developed to prevent further increase in resistance. Copyright © 2008 Society of Chemical Industry     

Effects of herbicides on rice resistance and on multiplication and feeding of brown planthopper (BPH), Nilaparvata lugens (StÅl) (Homoptera: Delphacidae)

Two-way effects of herbicide on rice resistance and multiplication and feeding of the rice brown planthopper (BPH), Nilaparvata lugens (Stål) were studied. Four of 11 herbicides tested, butachlor, metolachlor, oxadiazon and bentazone, had significantly stimulating effects on multiplication and feeding of BPH. Multiplication times (N ₁/N ₀) of BPH on the rice treated with the four herbicides were 674, 367, 322 and 311, respectively, while that of N. lugens on the untreated plants was 159. The results of measurements of honeydew production by BPH indicated that the feeding rates of the brown planthoppers increased when the insects fed on the plants treated with bentazone, quinclorac, oxadiazon and quinclorac. Survival rates of N. lugens first to third-instars rose on the rice plants treated with butachlor, bentazone, but that of the fourth and fifth instars were not affected. Furthermore, all of those herbicides tested led to a decline of rice resistance, i.e. the injury scales of the treated plants were larger than that of the control under the same pest stress. Based on their effects on rice resistance and on BPH, the herbicides tested can be divided into two categories, one affecting rice resistance and BPH multiplication, the other affecting rice resistance only.     

Herbicide resistant Phalaris minor in India—history of evolution,present status and its management

Phytoparasitica - The introduction and large scale cultivation of wheat cultivars which are semi-dwarf and high yielding in the north-western Indo-Gangetic Plains (IGPs) of India has led to the...     

Mayweed chamomile (Anthemis cotula L.) biology and management—A review of an emerging global invader

The globally invasive weed, mayweed chamomile (Anthemis cotula L.) is an annual, bushy, ill-scented herb, originating in Eurasia. It is aggressively weedy in croplands, field-side ditches, wet areas and along roadsides, especially in slightly acidic, nitrogen-rich, clay-loam soils. In addition to interfering with crop growth, the weed causes dermatitis and eye irritation in humans, skin rashes and sour mouth in domesticated mammals, and off-flavours in cow's milk through forage contamination. Although A. cotula may be managed effectively with some broadleaf herbicides in cereal crops, it is much more difficult to manage in broadleaved crops and cover crops. In some regions, aggressive use of relatively few herbicides has selected for acetolactate synthase herbicide resistance in A. cotula. Therefore, A. cotula poses serious ecological and economic challenges in many regions. Despite this threat, the details of A. cotula biology and ecology in the context of environmental change remain relatively unknown. For example, the reason for the invasiveness of A. cotula remains uncertain, but is presumed to be due to abundant seed production, allelochemicals, mycorrhizal associations, minimal herbivory in invaded ranges, ability to attract generalist pollinators through an extended flowering period and adaptive capacity in a wide range of soil types and conditions. In this paper, we comprehensively review the literature and ongoing work on A. cotula and provide a research agenda to improve understanding and management of this species.     

False codling moth,Thaumatotibia leucotreta (Meyrick) a new threat to horticulture industry: Stakeholders’ perspectives on the status,impact and management in Kenya

Journal of Plant Diseases and Protection - False codling moth (FCM) has emerged as a major constraint to the production of horticultural crops in Kenya and is currently the leading cause of...     

Insecticide resistance management of Bemisia tabaci (Hemiptera: Aleyrodidae) in Australian cotton – pyriproxyfen,spirotetramat and buprofezin

BACKGROUND

Bemisia tabaci is a globally significant agricultural pest including in Australia, where it exhibits resistance to numerous insecticides. With a recent label change, buprofezin (group 16), is now used for whitefly management in Australia. This study investigated resistance to pyriproxyfen (group 7C), spirotetramat (group 23) and buprofezin using bioassays and available molecular markers.

RESULTS

Bioassay and selection testing of B. tabaci populations detected resistance to pyriproxyfen with resistance ratios ranging from 4.1 to 56. Resistance to spirotetramat was detected using bioassay, selection testing and sequencing techniques. In populations collected from cotton, the A2083V mutation was detected in three populations of 85 tested, at frequencies ≤4.1%, whereas in limited surveillance of populations from an intensive horticultural region the frequency was ≥75.8%. The baseline susceptibility of B. tabaci to buprofezin was determined from populations tested from 2019 to 2020, in which LC₅₀ values ranged from 0.61 to 10.75 mg L⁻¹. From the bioassay data, a discriminating dose of 200 mg L⁻¹ was developed. Recent surveillance of 16 populations detected no evidence of resistance with 100% mortality recorded at doses ≤32 mg L⁻¹. A cross-resistance study found no conclusive evidence of resistance to buprofezin in populations with high resistance to pyriproxyfen or spirotetramat.

CONCLUSIONS

In Australian cotton, B. tabaci pest management is challenged by ongoing resistance to pyriproxyfen, while resistance to spirotetramat is an emerging issue. The addition of buprofezin provides a new mode-of-action for whitefly pest management, which will strengthen the existing insecticide resistance management strategy. © 2023 Commonwealth of Australia. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Weed or not a weed? Density,perceptions and management of Chromolaena odorata (Asteraceae) in West Africa: Voices from Ghana

The status (weed or beneficial shrub) of Chromolaena odorata in West Africa has been a major subject of debate since its introduction in the 1930s. Its negative impacts on agriculture and biodiversity are clear. However, indigenous people have harnessed several benefits of the plant, making management strategies less straightforward. Using indigenous voices in Ghana, the current perceptions of C. odorata in West Africa were assessed. Here, 90 respondents in three regions of Ghana were interviewed, using questionnaires, on aspects relating to the abundance, perceptions and management of C. odorata in their communities. Overall, results showed that the density of C. odorata had declined. The majority of the respondents considered C. odorata as a fallow shrub, a medicinal plant or both. However, impacts on crop production and injuries incurred during physical control were also highlighted. The local uses of the plant in Ghana included treating fevers and injuries, and as a fallow shrub for soil nutrient replenishment. Although most of the respondents classified C. odorata as a useful shrub in Ghana, they also highlighted the use of local farming tools such as cutlasses for the slash of the plant. The use of herbicides for the control of C. odorata was rare and not applied specifically for C. odorata. In conclusion, local awareness programmes on the deleterious impacts of C. odorata on ecosystem functioning and livelihoods are required for its effective management in West Africa.     

A model system for plant-virus interaction—infectivity and seed transmission of <Emphasis Type="Italic">Cherry leaf roll virus</Emphasis> (CLRV) in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

The wide natural incidence of Cherry leaf roll virus (CLRV) in deciduous forest trees and nurseries in northern Europe is believed to have occurred, apart from occasional mechanical spread and transmission through grafting, mainly by seed transmission. The mode of the vertical transmission and its role in the epidemiology of the virus has not been investigated, basically due to the inconvenient host-pathogen combinations studied to date. With the aim of obtaining an appropriate system for identification of viral genes and products participating in infection processes and seed transmission of CLRV, we performed infection and seed transmissibility tests with CLRV in Arabidopsis thaliana plants. Two phylogenetically and serologically different CLRV isolates were tested. Both of them were found able to infect A. thaliana plants, exhibited clear symptoms of the infection and spread systemically in the plants. Infection of the seeds and of a remarkable number of seedlings generated from infected seeds was possible for two consecutive generations. These results, for first time, report seed transmission of CLRV in the model plant A. thaliana and allow the assumption to be made of embryo invasion during seed transmission. Furthermore, first indications are given that genetically diverse CLRV isolates exhibit different abilities for vertical transmission in A. thaliana. The CLRV-A. thaliana model system is suitable for investigating viral invasion of developing plant organs and meristematic tissue, a prerequisite for successful virus dissemination via vertical transmission through seed.