Naeem Abbas

Cross‐resistance, the stability of acetamiprid resistance and its effect on the biological parameters of cotton mealybug, Phenacoccus solenopsis (Homoptera: Pseudococcidae), in Pakistan

BACKGROUND Acetamiprid is a neonicotinoid insecticide that is effective against both soil and plant insects, including insects of the orders Lepidoptera, Coleoptera, Homoptera and Thysanoptera. In order to estimate the effects associated with insecticide exposure and devise better pest management tactics, a field population of Phenacoccus solenopsis was exposed to acetamiprid in the laboratory. Subsequently, cross-resistance and the effects of acetamiprid on the biological parameters of P. solenopsis were investigated. RESULTS Following five rounds of selection with acetamiprid, P. solenopsis developed a 315-fold greater resistance to this chemical compared with an unexposed control population. The selected population also demonstrated very high to moderate cross-resistance to other tested insecticides. Furthermore, acetamiprid resistance remained unstable when the acetamiprid-selected population was not exposed for a further five generations. The acetamiprid-selected population had a relative fitness of 0.22, with significantly lower survival rate, pupal weight, fecundity, percentage hatching, net reproductive rate, intrinsic rate of natural increase, biotic potential and mean relative growth rate, with prolonged male and female nymphal duration, developmental time from egg to female adult and male and female longevity compared with the control population. CONCLUSION P. solenopsis biological parameters are greatly affected by acetamiprid, and it is of significant cost for the insects to counter these effects. This study will be a valuable source of information for further understanding of acetamiprid resistance and for assisting the development of resistance management programmes.

Effect of emamectin benzoate on life history traits and relative fitness of Spodoptera litura (Lepidoptera: Noctuidae)

Emamectin benzoate, a semisynthetic bioinsecticide, has been used frequently for the management of lepidopteran pests of cotton worldwide. To assess the resistance risk and design strategy for resistance management, life history traits were established for emamectin benzoate-resistant, unselected and susceptible S. litura strains based on the laboratory observations. Bioassay results showed that the emamectin benzoate-selected strain developed a resistance ratio of 911-fold compared with that of the susceptible strain. The emamectin-selected strain had a relative fitness of 0.37 and lower prepupal and pupal weights, prolonged larval duration and development time, lower fecundity and hatchability compared with the susceptible strain. Mean population growth rates, such as intrinsic rate of population increase and biotic potential, were lower for the emamectin-selected strain compared with the susceptible strain. Development of resistance can cost considerable fitness for the emamectin-selected strain. The present study provided useful information for determining potential management strategies to overcome development of resistance.

Genetics and realized heritability of resistance to imidacloprid in a poultry population of house fly, Musca domestica L. (Diptera: Muscidae) from Pakistan.

Imidacloprid, a post-synaptic, nicotinic insecticide, has been commonly used for the management of different pests including Musca domestica worldwide. Many pests have developed resistance to this insecticide. A 16-fold imidacloprid-resistant population of M. domestica infesting poultry was selected using imidacloprid for 13 continuous generations to study the inheritance and realized heritability of resistance. Toxicological bioassay at G14 showed that the imidacloprid-selected population developed 106-fold resistance when compared to the susceptible population. Reciprocal crosses of susceptible and resistant populations showed an autosomal trait of resistance to imidacloprid in M. domestica. There was incompletely recessive resistance in F1 (Imida-SEL ♂ × Susceptible ♀) and F1(†) (Imida-SEL ♀ × Susceptible ♂) having dominance value 0.53 and 0.31, respectively. Monogenic model of inheritance showed that imidacloprid resistance was controlled by multiple factors. The realized heritability value was 0.09 in the imidacloprid-selected population of M. domestica. It was concluded that imidacloprid resistance in M. domestica was autosomally inherited, incompletely recessive and polygenic. These findings should be helpful for better and more successful management of M. domestica.

Mechanism, stability and fitness cost of resistance to pyriproxyfen in the house fly, Musca domestica L. (Diptera: Muscidae)

Pyriproxyfen, a bio-rational insecticide, used worldwide for the management of many insect pests including the house fly, Musca domestica. To devise a retrospective resistance management strategy, biological parameters of pyriproxyfen resistant (Pyri-SEL), unselected (UNSEL), Cross1 and Cross2M. domestica strains were studied in the laboratory. Additionally, the stability and mechanism of resistance was also investigated. After 30 generations of pyriproxyfen selection, a field-collected strain developed 206-fold resistance compared with susceptible strain. Synergists such as piperonyl butoxide and S,S,S-tributylphosphorotrithioate did not alter the LC50 values, suggesting another cause of target site resistance to pyriproxyfen in the Pyri-SEL strain. The resistance to all tested insecticides was unstable in Pyri-SEL strain. The relative fitness of 0.51 with lower fecundity, hatchability, lower number of next generation larvae, reduced mean population growth rate and net reproductive rate were observed in the Pyri-SEL strain compared with the UNSEL strain. The cost of fitness associated with pyriproxyfen resistance was evident in Pyri-SEL strain. The present study provides useful information for making pro-active resistance management strategies to delay resistance development.

Increased fitness and realized heritability in emamectin benzoate-resistant Chrysoperla carnea (Neuroptera: Chrysopidae)

The common green lacewing Chrysoperla carnea is a key biological control agent employed in integrated pest management (IPM) programs for managing various insect pests. A field collected population of C. carnea was selected for emamectin benzoate resistance in the laboratory and fitness costs and realized heritability were investigated. After five generations of selection with emamectin benzoate, C. carnea developed a 318-fold resistance to the insecticide. The resistant population had a relative fitness of 1.49, with substantially higher emergence rate of healthy adults, fecundity and hatchability and shorter larval duration, pupal duration, and development time compared to the susceptible population. Mean population growth rates; such as the intrinsic rate of natural population increase and biotic potential were higher for the emamectin benzoate selected population compared to the susceptible population. The realized heritability (h2) value of emamectin benzoate resistance was 0.34 in emamectin benzoate selected population of C. carnea. Chrysoperla species which show resistance to insecticides makes them compatible with those IPM systems where emamectin benzoate is employed.

Resistance of Dusky Cotton Bug, Oxycarenus hyalinipennis Costa (Lygaidae: Hemiptera), to Conventional and Novel Chemistry Insecticides

Abstract The dusky cotton bug, Oxycarenus hyalinipennis Costa (Lygaidae: Hemiptera), is polyphagous in nature and has become one of the severe sucking pests of cotton in Pakistan. O. hyalinipennis has the potential to develop resistance to a number of insecticides, and as a result, O. hyalinipennis outbreaks occur. There is no previous study from Pakistan regarding O. hyalinipennis resistance to insecticides. Therefore, the aim of this study was to assess the resistance of different field populations of O. hyalinipennis to conventional (bifenthrin, deltamethrin, lambda-cyhalothrin, profenofos, triazophos) and novel chemistry (emamectin benzoate, spinosad, chlorfenapyr, imidacloprid, and nitenpyram) insecticides. Five populations of O. hyalinipennis, collected from Multan, Khanewal, Muzaffargarh, Lodhran, and Bahawalpur, were tested for resistance to selected insecticides by the leaf dip method. For three pyrethroids, the resistance ratios were in the range of 14- to 30-fold for bifenthrin, 2.14- to 8.41-fold for deltamethrin, and 9.12- to 16-fold for lambda-cyhalothrin, compared with the laboratory susceptible strain (Lab-PK). For two organophosphates, the range of resistance ratios was 12- to 14-fold for profenofos and 9.04- to 15-fold for triazophos. For five novel chemistry insecticides, the range of resistance ratios was 4.68- to 9.83-fold for emamectin benzoate, 6.38- to 17-fold for spinosad, 16- to 46-fold for chlorfenapyr, 11-to 22-fold for imidacloprid, and 1.32- to 11-fold for nitenpyram. Regular assessment of resistance to insecticides and integrated management plans like judicious use of insecticides and rotation of insecticides along with different modes of action are required to delay resistance development in O. hyalinipennis.

Resistance to Conventional and New Insecticides in House Flies (Diptera: Muscidae) From Poultry Facilities in Punjab, Pakistan

ABSTRACT House flies, Musca domestica L., are pests of poultry facilities and have the ability to develop resistance against different insecticides. This study was conducted to assess the resistance status of house flies to pyrethroid, organophosphate, and novel chemistry insecticides from poultry facilities in Punjab, Pakistan. Five adult house fly populations were studied for their resistance status to selected conventional and novel chemistry insecticides. For four pyrethroids, the range of resistance ratios was 14–55-fold for Cypermethrin, 11–45-fold for bifenthrin, 0.84–4.06-fold for deltamethrin, and 4.42–24-fold for lambda-cyhalothrin when compared with a susceptible population. Very low levels of resistance were found to deltamethrin compared with the other pyrethroids. For the three organophosphate insecticides, the range of resistance ratios was 1.70–16-fold for profenofos, 7.50–60-fold for chlorpyrifos, and 4.37–53-fold for triazophos. Very low levels of resistance were found to profenofos compared with the other insecticides. For five novel chemistry insecticides, the range of resistance ratios was 1.20–16.00-fold for fipronil, 3.73–7.16-fold for spinosad, 3.06–23-fold for indoxacarb, 0.96–5.88-fold for abamectin, and 0.56–3.07-fold for emamectin benzoate. Rotation of insecticides with different modes of action showing no or very low resistance may prevent insecticide resistance in house flies. Regular insecticide resistance monitoring and integrated management plans on poultry farms are required to prevent resistance development, field control failures, and environmental pollution.

Fitness cost and realized heritability of resistance to spinosad in Chrysoperla carnea (Neuroptera: Chrysopidae).

The common green lacewing Chrysoperla carnea is a key biological control agent employed in integrated pest management (IPM) programs for managing various insect pests. Spinosad is used for the management of pests in ornamental plants, fruit trees, vegetable and field crops all over the world, including Pakistan. A field-collected population of C. carnea was selected with spinosad and fitness costs and realized heritability were investigated. After selection for five generations, C. carnea developed 12.65- and 73.37-fold resistance to spinosad compared to the field and UNSEL populations. The resistant population had a relative fitness of 1.47, with substantially higher emergence rate of healthy adults, fecundity and hatchability and shorter larval duration, pupal duration, and development time as compared to a susceptible laboratory population. Mean relative growth rate of larvae, intrinsic rate of natural population increase and biotic potential was higher for the spinosad-selected population compared to the susceptible laboratory population. Chrysoperla species are known to show resistance to insecticides which makes the predator compatible with most IPM systems. The realized heritability (h 2) value of spinosad resistance was 0.37 in spinosad-selected population of C. carnea.

Inheritance mode, cross-resistance and realized heritability of pyriproxyfen resistance in a field strain of Musca domestica L. (Diptera: Muscidae).

Pyriproxyfen is a growth regulator used for the control of different insect pests, including Musca domestica. To assess the risk of resistance and to develop a strategy for resistance management, a field strain of M. domestica was exposed to pyriproxyfen in the laboratory for 30 generations. The inheritance mode, realized heritability of pyriproxyfen resistance and cross-resistance to other insecticides were assessed. Prior to the selection process, the field strain exhibited a resistance ratio (RR) of 25.7, 7.31, 7.67, and 27-fold for pyriproxyfen, methoxyfenozide, cyromazine and lufenuron, respectively, when compared to the pyriproxyfen susceptible strain (Pyri-Sus). After continuous selection with pyriproxyfen, the pyriproxyfen-resistant strain (Pyri-Res) became 206-fold more resistant than the Pyri-Sus strain. The overlapping confidence limits of LC50 values of F1 (Pyri-Res ♂×Pyri-Sus ♀) and F1(†) (Pyri-Res ♀×Pyri-Sus ♂) suggested an autosomal and completely dominant mode of resistance to pyriproxyfen. Monogenic test of inheritance showed that resistance to pyriproxyfen was governed by multiple genes. The Pyri-Res strain showed very low cross resistance to methoxyfenozide, cyromazine, and lufenuron. The estimated realized heritability was 0.02, 0.05, 0.03 and 0.04 for pyriproxyfen, methoxyfenozide, cyromazine, and lufenuron, respectively. It was concluded that pyriproxyfen resistance in M. domestica was autosomally inherited, completely dominant and polygenic. These results would be helpful for the design of an improved control strategy against M. domestica.

Stability of Field-Selected Resistance to Conventional and Newer Chemistry Insecticides in the House Fly, Musca domestica L. (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), is a pest of livestock and has the ability to develop resistance to different insecticides. We assessed the fluctuations in seasonal stability of house fly resistance to insecticides from poultry facility populations in Pakistan. House fly populations were collected from poultry facilities located at Khanewal, Punjab, Pakistan in three seasons (July, November, and March) to investigate the fluctuations in their resistance to conventional (organophosphate, pyrethroid) and novel chemistry (spinosyn, oxadiazine, neonicotinoid) insecticides. Laboratory bioassays were performed using the feeding method of mixing insecticide concentrations with 20% sugar solutions, and cotton pads dipped in insecticide solutions were provided to tested adult flies. Bioassay results showed that all house fly populations had varying degrees of susceptibility to tested insecticides. Comparisons between populations at different seasons showed a significant fluctuation in susceptibility to organophosphate, pyrethroid, spinosyn, oxadiazine, and neonicotinoid insecticides. Highest resistant levels were found for organophosphate when compared with other tested insecticides. The resistance to conventional insecticides decreased significantly in March compared with July and November, while resistance to oxadiazine and avermectins decreased significantly in November. However, resistance to spinosad and imidacloprid remained stable throughout the seasons. All conventional and novel chemistry insecticides were significantly correlated with each other in all tested seasons except nitenpyram/lambda-cyhalothrin and nitenpyram/imidacloprid. Our data suggests that the variation in house fly resistance among seasons could be due to fitness costs or to the cessation of selection pressure in the off-season. These results have significant implications for the use of insecticides in house fly management.