Spider mite control and resistance management: does a genome help?

The complete genome of the two‐spotted spider mite, Tetranychus urticae, has been reported. This is the first sequenced genome of a highly polyphagous and resistant agricultural pest. The question as to what the genome offers the community working on spider mite control is addressed. Copyright © 2012 Society of Chemical Industry     

Are herbicides a once in a century method of weed control?

The efficacy of any pesticide is an exhaustible resource that can be depleted over time. For decades, the dominant paradigm – that weed mobility is low relative to insect pests and pathogens, that there is an ample stream of new weed control technologies in the commercial pipeline, and that technology suppliers have sufficient economic incentives and market power to delay resistance – supported a laissez faire approach to herbicide resistance management. Earlier market data bolstered the belief that private incentives and voluntary actions were sufficient to manage resistance. Yet, there has been a steady growth in resistant weeds, while no new commercial herbicide modes of action (MOAs) have been discovered in 30 years. Industry has introduced new herbicide tolerant crops to increase the applicability of older MOAs. Yet, many weed species are already resistant to these compounds. Recent trends suggest a paradigm shift whereby herbicide resistance may impose greater costs to farmers, the environment, and taxpayers than earlier believed. In developed countries, herbicides have been the dominant method of weed control for half a century. Over the next half‐century, will widespread resistance to multiple MOAs render herbicides obsolete for many major cropping systems? We suggest it would be prudent to consider the implications of such a low‐probability, but high‐cost development. © 2017 Society of Chemical Industry     

Bt-transgenic crops: just another pretty insecticide or a chance for a new start in resistance management?

Transgenic insect-resistant crops carrying genes from Bacillus thuringiensis were grown commercially for the first time in 1996 amid considerable public controversy about resistance management. Several resistance management strategies have been proposed for Bt-transgenic crops. The most promising with currently available technology is the use of refuges of non-transgenic crops, augmented where possible with high toxin expression in the plant and avoiding mosaics of different toxins and pesticides. One problem is that the refuge sizes that are seen as commercially and practically acceptable are generally too small to provide a comfortable margin for the delay of resistance. A promising long-term strategy for delaying resistance, and one which is more forgiving on refuge size, is the pyramiding of two or more insecticidal genes in the same plant. The critical limiting factor to resistance management for transgenic crops will be implementation, which will require cooperation among companies. ©1997 SCI     

Fungal-based bioherbicides for weed control: a myth or a reality?

The use of bioherbicides containing fungal active ingredients or natural fungal molecules is one of the possible solutions to reduce the use of chemical products. This paper focuses on studies of bioherbicides, including both living fungi and natural fungal molecules, published in the last 45 years, and their associated weed targets; current problems in the development of bioherbicides are also discussed. Bibliometric methods based on the Web of Science database were used to analyse relevant articles published between 1973 and 2018. Overall analysis suggested that interest in bioherbicides extends over the preceding thirty years, when many potential microorganisms and natural fungal molecules were proposed. Furthermore, analysis of about 229 articles indicated an encouraging exploitable potential, although there is a real gap between the number of experimental studies and the small number of products currently on the market. A dozen fungal-based bioherbicides are on the market in the United States and Canada, while countries, such as China and South Africa, have one, and none is available in Europe. The active ingredients in these bioherbicides are living fungi, but no fungal molecule-based product is thus far on the market. Reasons for this gap include production hurdles, formulation process, ecological fitness, duration of herbicidal effects, and costly and time-consuming registration procedures. However, it is clear that analysis of fungus–plant interactions provides a promising source of bioherbicides that may be applied to appropriate cropping systems for environment-friendly, sustainable weed control.     

Endophytic fungi in the invasive weed Impatiens glandulifera: a barrier to classical biological control?

The rust fungus, Puccinia komarovii var. glanduliferae, has been introduced into the UK for biological control of the invasive weed, Impatiens glandulifera (Himalayan balsam). However, establishment of the pathogen has differed across the country, which may be partly explained by variation in plant genotype. The aim of this study was to examine whether there is a further layer of phenotypic resistance, provided by indigenous foliar endophytic fungi. Culturable endophytes were isolated from a number of different balsam populations, and the commonest species were inoculated into ‘clean’ balsam plants, to test their interactions with the rust. We found that endophyte communities within balsam are low in diversity and become more dissimilar with increasing distance between populations. Three endophytes (Colletotrichum acutatum, Alternaria alternata and Cladosporium oxysporum) were common and appeared to be antagonistic to the rust, reducing pustule number and mitigating the effect of the pathogen on plant biomass. I. glandulifera thus partially conforms to the endophyte-enemy release hypothesis, in that as an introduced species, it has an impoverished endophyte complement, acquired from the local environment. However, these endophytes represent a potential barrier to effective biological control and future weed control strategies need to find strains of rust that can overcome plant genetic resistance and the overlaying phenotypic resistance, conferred by endophytes. Future classical biological control programmes of weeds must therefore take into account the fungal bodyguards that invasive species may acquire in their introduced ranges.     

Assessment of resistance risk in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) to chlorantraniliprole

BACKGROUND: Beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a major pest of numerous cultivated crops. Chlorantraniliprole, the first commercialised ryanodine receptor insecticide from the anthranilic diamide class, has exceptional insecticidal activity on a range of lepidopteran pests. The aim of this study was to assess the resistance of S. exigua to chlorantraniliprole in the laboratory. RESULTS: A field‐collected population of S. exigua was selected after repeated exposure to chlorantraniliprole to determine the risk of resistance evolution. After 22 generations of selection, there was a 12.0‐fold increase in LC₅₀. The realised heritability (h²) of resistance was estimated as 0.1082 by using threshold trait analysis. The projected rate of resistance evolution indicated that, if h² = 0.1082 and 70% of the population was killed at each generation, then a tenfold increase in LC₅₀ would be expected in 21.7 generations for chlorantraniliprole. CONCLUSION: These results show that the risk of resistance development to chlorantraniliprole exists in S. exigua after continuous application. Copyright © 2011 Society of Chemical Industry     

Note: Corythauma ayyari (Drake) (Hemiptera: Heteroptera: Tingidae)—a new pest of ornamentals in Israel

We herewith report for the first time the discovery in Israel of the invasive species Corythauma ayyari (Drake), a member of the lace-bug family, Tingidae (Hemiptera).     

Insecticide resistance management and integrated mite management in orchards: can they coexist?

At the core of an integrated pest management program for Pennsylvanian apple orchards is an integrated mite management program that is based on a natural enemy, the coccinellid Stethorus punctum punctum (LeConte). The program relies upon the principles of ecological selectivity (e.g. chemical selection, timing, dose and method of application) for the organophosphate and carbamate insecticides. During the last 20 years the tufted apple bud moth (TABM), Platynota idaeusalis (Walker), a direct pest of apple, has developed resistance to these two chemical classes. In an effort to address this growing resistance problem, an intensive research program was initiated in 1986 on how to manage insecticide resistance in TABM while preserving the integrity of the integrated mite management program. One aspect of this research program is the investigation of biochemical and genetic approaches to resistance, including an analysis of detoxification mechanisms, effects of host plant allelochemistry on resistance and detoxification enzyme activities, reversion, gene flow and the isolation and characterization of a gene for glutathione transferase from TABM. Management approaches that have been developed and successfully implemented include pheromone mating disruption, parasitoids, ground-cover management including insecticides, Bacillus thuringiensis Berl. products and insect growth regulators. Resistance management options for TABM are presented. ©1997 SCI     

The Asian planthopper Ricania speculum (Walker) (Homoptera: Ricaniidae) on several crops in Italy: a potential threat to the EPPO region?

In August 2014, twenty adults of Ricania speculum (Walker) (Homoptera: Ricaniidae) were collected on plants of Citrus spp. in La Spezia province (Liguria, Italy). This planthopper, which is native to parts of China and other Asian countries, is highly polyphagous and a pest of several crops such as citrus, cotton, coffee, oil palm and tea. As a newly introduced pest in Europe, R. speculum needs to be monitored for its potential spread, especially in Southern European countries and for the damage it may cause to agriculture in the region.     

Mechanism and molecular markers associated with rust resistance in a chickpea interspecific cross (Cicer arietinum × Cicer reticulatum)

A gene that controls resistance to chickpea rust (Uromyces ciceris-arietini) has been identified in a recombinant inbred line (RIL) population derived from an interspecific cross between Cicer arietinum (ILC72) × Cicer reticulatum (Cr5-10), susceptible and resistant to rust, respectively. Both parental lines and all RILs displayed a compatible interaction but differed in the level of infection measured as Disease Severity (DS) and Area Under the Disease Progress Curve (AUDPC). Histological studies of the seedlings of resistant parental Cr5-10 line revealed a reduction in spore germination, appressorium formation, number of haustoria per colony and colony size, with little host cell necrosis, fitting the definition of partial resistance. A Quantitative Trait Locus (QTL) explaining 31% of the total phenotypic variation for DS in seedlings and 81% of the AUDPC in adult plants in the field was located on linkage group 7 of the chickpea genetic map. The AUDPC displayed a bimodal distribution with high frequency of susceptible lines and both the AUDPC and markers showed the same distorted segregation. Consequently, it was hypothesised that a single dominant gene (proposed as Uca1/uca1) controlled resistance to rust in adult plants. This allowed us to locate the gene on the genetic linkage map. Two Sequence Tagged Microsatellite Sites (STMS) markers, TA18 and TA180 (3.9 cM apart) were identified that flank the resistance gene. These findings could be the starting point for a Marker-Assisted Selection (MAS) programme for rust resistance in chickpea.     

Long-term selection for resistance to transgenic cotton expressing Bacillus thuringiensis toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hübner) were conducted using a leaf-feeding method with 42 selection episodes over 45 generations. The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F12) of selection. The survival rate of F12 neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R19 line were ca 34 and 72%, respectively, compared with ca 0 and 40% for a non-selected sister strain (NYCS), but lower than or similar to that of F12 feeding on leaves of non-Bt cotton, Sumian 12 (ca 87 or 76%). Resistance to B thuringiensis HD-1 Dipel in neonates (F12) was ca 6-fold. After 42 generations of selection, the strain developed a very high level of resistance to Cry1Ac protoxin, 210 g kg(-1) MVPII wettable powder and 200 g litre(-1) MVPII liquid formulation, the resistance ratios being 1680-, 1780- and ca 1200-fold, respectively, compared with a laboratory susceptible strain (HZS). When compared with the non-selected NYCS, the resistance ratios to the above toxins were ca 540-, 580- and 510-fold, respectively, but to Dipel only ca 16-fold. The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.     

Is acetyl/butyrylcholine specificity a marker for insecticide‐resistance mutations in insect acetylcholinesterase?

Substrate specificity has been widely studied in vertebrate cholinesterases and it has been shown that two phenylalanines in the acyl pocket of acetylcholinesterase govern the acceptance of the acetyl/butyryl moiety of the choline esters. As an insecticide‐resistance mutation has been evidenced in the acyl pocket of Drosophila melanogaster and Musca domestica acetylcholinesterase we investigated the possibility of linking changes in acetyl/butyrylthiocholine specificity with mutations in insect acetylcholinesterase. We thus analyzed the effect of 28 mutations in Drosophila enzyme on acetyl/butyrylthiocholine, N‐methyl/N‐propyl‐carbamates and ethyl/methyl‐paraoxon preference. It appeared that the highest changes on acetyl/butyrylthiocholine and N‐propyl/N‐methyl‐carbamates preference were due to mutations in the acyl pocket. Nevertheless, other insecticide‐resistance mutations, not located in the acyl pocket, also modified these substrate preferences. Moreover, the effect of mutations in the acyl pocket was hidden when some other insecticide‐resistance mutations were combined in the enzyme. Consequently, acetyl/butyrylthiocholine preference alteration cannot be used as a marker to localize a mutation in the insect AChE. © 2000 Society of Chemical Industry     

Pyrethroid resistance in Finnish pollen beetle (Meligethes aeneus) populations – is it around the corner?

The pollen beetle Meligethes aeneus F. is the most important pest of rapeseed [ Brassica rapa subsp. oleifera (DC.) Metzg.] in Finland. After over 20 years of intensive rapeseed growing and annual spraying with pyrethroids, the probability of resistance development may be high. Population samples of the pollen beetle from four different regions representing a range of Finnish rapeseed growing practices were collected, and tested for pyrethroid resistance. Region 1 had a history of intensive rapeseed growing for about 30 years, in region 4 no rapeseed had ever been grown (reference region), and regions 2 and 3 represented differing intermediates in growing intensity (proportion of growing area allocated to rapeseed) and growing history. A standard dip test with lambda-cyhalothrin was used in a dilution series with ten different concentrations. Some of the dipped beetles were also weighed. Insecticide susceptibility in the populations collected from region one differed significantly from the others: 60% of those populations survived the standard dose. There was no difference in the median weight of surviving and dead individuals in the most resistant population, while in the most susceptible population the size of individual beetles significantly affected the probability of death by the insecticide treatment.     

Inheritance of resistance to Bacillus thuringiensis Cry1Ac toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from India

BACKGROUND: The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most serious insect pests of cotton. It has developed resistance to almost all groups of chemical insecticides because of their intensive use. The failure of insecticides to control H. armigera has been a strong incentive for the adoption of transgenic cotton (Bt cotton). However, the value of Bt could be diminished by widespread resistance development to Bt toxins in insect populations. Therefore, understanding the genetic basis of resistance is essential for developing and implementing strategies to delay and monitor resistance. RESULTS: A resistant strain designated as BM‐R was obtained from the cross of adults from Bathinda () and Muktsar (), Punjab, India, which showed the highest survival (60.68%) and LC₅₀ value (1.396 µg mL^?1 diet). Similarly, a laboratory‐maintained strain from Hoshiarpur, Punjab, showed maximum susceptibility to Cry1Ac toxin with the lowest LC₅₀ value (0.087 µg mL^?1), and was designated as HP‐S. The genetic purity of both strains was confirmed by RAPD profile analysis at each generation, and genetic similarity reached more than 90% after the third generation. Continuous maintenance of the resistant BM‐R strain on Cry1Ac resulted in an increase in LC₅₀ from 0.531 µg mL^?1 in F₀ to 4.28 µg mL^?1 in F₁₄ and 7.493 µg mL^?1 in F₁₉, while the LC₅₀ values for HP‐S larvae on diet without Cry1Ac increased to 0.106 and 0.104 µg mL^?1, which lay within the fiducial limits of the baseline LC₅₀ value. The mode of inheritance of resistance was elucidated through bioassay response of resistant, susceptible heterozygotes and backcross progeny to Cry1Ac incorporated in semi‐synthetic diet. CONCLUSION: Based on dominance, degree of dominance and backcross values, resistance was inferred to be polygenic, autosomal and inherited as a recessive trait. Copyright © 2011 Society of Chemical Industry     

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     

The efficacy of Vespex® wasp bait to control Vespula species (Hymenoptera: Vespidae) in New Zealand

ABSTRACT

Transitioning from trials to pest control tool, the efficacy of controlling wasps Vespula vulgaris and V. germanica using Vespex® wasp bait was tested in 2015. Vespex® is a protein-based bait matrix with 0.1% fipronil. Five sites ranging <300 to >2000 ha and over 5500 ha in total had bait stations placed 300 × 50 m apart and received one application of Vespex®. Wasp nest traffic rates declined 93% in four days at one site, and over 97% after 20–38 days at all other sites. Measured honeydew availability also improved post wasp control. Further demonstrating feasibility, five different agencies worked closely with government leading many programme aspects. Vespex® was made more widely available in New Zealand towards the end of 2015. Web page information showed ～30% of all territorial authorities nationally are engaging in pest wasp problems. This signals a future potential in the way that pest wasps might be managed in a community context for social, economic and biodiversity conservation objectives.     

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.