scholarly journals Resistance Development to Diflubenzuron and Bacillus Thuringiensis Subsp. Israelensis of Culex Pipiens f. Pipiens and Culex Pipiens f. Molestus (Diptera: Culicidae) and its Effects on Their Winter Survival

2020 ◽  
Author(s):  
Charalampos Ioannou ◽  
Christos Hadjichristodoulou ◽  
Maria A. Kyritsi ◽  
Nikos T. Papadopoulos
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Pipiens ◽  
Survival Rates ◽  
Larval Survival ◽  
Winter Survival ◽  
World Health ◽  
Winter Period ◽  
Fitness Costs ◽  
Resistance Development ◽  
High Dependency

Abstract Background: The Culex pipiens mosquito consists of two forms named pipiens and molestus that exhibit substantial differences in their biology including overwintering behavior. Diflubenzuron (DFB) and Bacillus thuringiensis subsp. israelensis (Bti) are among the most widely used larvicides for controlling Cx. pipiens populations. The high dependency on these two larvicides, pose major concerns for resistance development. The evolution and stability of resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions such as the winter period. The aim of the present study was to explore the resistance development of pipiens and molestus forms to both larvicides and its potential fitness costs on their winter survival.Methods: Colonies of both forms of Cx. pipiens were established from the same area. Following the World Health Organization protocols (WHO), the efficacy of both larvicides was determined for each mosquito population. Then, larvae from each form were selected for three successive generations by applying fixed doses corresponding to IE80 (IE: Inhibition of adult Emergence) and LC80 (LC: Lethal Concentration) for DFB and Bti respectively. At the end of this process, the resistance levels and the winter survival of the selected populations relative to controls (colonies that received no selection) were determined.Results: Contrary to Bti, selection with DFB induced different levels of resistance between the two forms of Cx. pipiens. The selected populations of Cx. pipiens f. molestus to both larvicides exhibited a high fitness cost in terms of reduced winter larval survival rates relative to control. Moreover, the obtained adults of the Bti selected population experienced significantly shorter lifespan compared to control and DFB selected population. On the other hand, selection with both DFB and Bti had no apparent effects on Cx. pipiens f. pipiens female winter survival rates relative to control. Furthermore, the reproductive parameters and the longevity of the overwintered females were similar between the selected populations and the control. Conclusions: Our findings are expected to contribute on the better understanding of the resistance development and evolution of the two forms of Cx. pipiens to DFB and Bti allowing the adoption of appropriate resistance management strategies.

Short Term Selection to Diflubenzuron and Bacillus Thuringiensis Subsp. Israelensis Differentially Affects the Winter Survival of Culex Pipiens F. Pipiens and Culex Pipiens F. Molestus (Diptera: Culicidae)

2020 ◽  
Author(s):  
Charalampos S Ioannou ◽  
Christos Hadjichristodoulou ◽  
Maria A Kyritsi ◽  
Nikos T Papadopoulos
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Pipiens ◽  
Survival Rates ◽  
Fitness Cost ◽  
Winter Survival ◽  
Winter Period ◽  
Short Term ◽  
Term Selection ◽  
High Fitness ◽  
High Dependency

Abstract BackgroundThe Culex pipiens mosquito consists of two forms named pipiens and molestus that exhibit substantial differences in their biology including overwintering behavior. Diflubenzuron (DFB) and Bacillus thuringiensis subsp. israelensis (Bti) are among the most widely used larvicides for controlling Cx. pipiens populations. The high dependency on these two larvicides, pose major concerns for resistance development. The evolution and stability of tolerance/resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions such as the winter period. This study aimed to investigate how short term selection of pipiens and molestus forms to both larvicides affect their susceptibility and their overwintering success.MethodsColonies of both forms of Cx. pipiens were established from the same area. Following standard protocols, the efficacy of both larvicides was determined for each mosquito population. Then, larvae from each form, were selected for three successive generations by applying fixed doses corresponding to IE80 (Inhibition of adult Emergence) and LC80 (Lethal Concentration) for DFB and Bti, respectively. At the end of this process, the susceptibility levels and the winter survival of the selected populations relative to controls (colonies that received no selection) were determined.ResultsContrary to Bti, selection with DFB induced different susceptibility levels between the two forms of Cx. pipiens. The selected populations of Cx. pipiens f. molestus to both larvicides exhibited a high fitness cost in terms of reduced winter larval survival rates relative to control. Moreover, the obtained adults of the Bti selected population experienced significantly shorter lifespan compared to control and DFB selected population. On the other hand, selection with both DFB and Bti had no apparent effects on Cx. pipiens f. pipiens female winter survival rates relative to control. Furthermore, the reproductive parameters and the longevity of the overwintered females were similar between the selected populations and the control. ConclusionsOur findings reveal that sort term selection to DFB and Bti induces a high fitness cost on the winter survival of Cx. pipiens f. molestus but not of pipiens form, suggesting potential differences on the persistence of tolerant individuals from year to year between the two forms.

scholarly journals Short-Term Selection to Diflubenzuron and Bacillus thuringiensis Var. Israelensis Differentially Affects the Winter Survival of Culex pipiens f. Pipiens and Culex pipiens f. Molestus (Diptera: Culicidae)

Insects ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 527
Author(s):  
Charalampos S. Ioannou ◽  
Christos Hadjichristodoulou ◽  
Maria A. Kyritsi ◽  
Nikos T. Papadopoulos
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Pipiens ◽  
Mosquito Control ◽  
Survival Rates ◽  
Winter Survival ◽  
Winter Period ◽  
Short Term ◽  
Term Selection ◽  
High Dependency ◽  
Successive Generations

The Culex pipiens (Diptera: Culicidae) mosquito is of high medical importance as it is considered the prime vector of West Nile virus. In Europe, this species consists of two forms, named pipiens and molestus, that exhibit substantial differences in their overwintering biology. Diflubenzuron (DFB) and Bacillus thuringiensis var. israelensis (Bti) are two of the most used larvicides in mosquito control, including that of Culex pipiens. The high dependency on these two larvicides poses major concerns for resistance development. The evolution and stability of resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions, such as the winter period. This study investigated how short-term selection of pipiens and molestus forms to both larvicides affect their overwintering success. Larvae from each form were subjected to the same selective pressure (80% mortality) for three successive generations with DFB and Bti. At the end of this process, the winter survival between the selected populations and the controls (colonies without selection) was determined for each form. Selection to both larvicides significantly reduced the winter survival rates of molestus but not of pipiens form, indicating potential differences in the persistence of the selected individuals from year to year between the two forms.

Survival Rates of Tobacco Budworm (Lepidoptera: Noctuidae) Larvae Exposed to Transgenic Cottons Expressing Insecticidal Protein of Bacillus thuringiensis Berliner

2000 ◽  
Vol 35 (2) ◽  
pp. 105-117 ◽  
Author(s):  
C. D. Parker ◽  
V. J. Mascarenhas ◽  
R. G. Luttrell ◽  
K. Knighten
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Heliothis Virescens ◽  
Survival Rates ◽  
Larval Survival ◽  
Tobacco Budworm ◽  
Bt Cotton ◽  
Plant Structure ◽  
Lepidoptera Noctuidae ◽  
Insecticidal Plants

The insecticidal activity of transgenic cottons expressing endotoxin protein of Bacillus thuringiensis Berliner (Bt cotton) was quantified by measuring survival of tobacco budworm, Heliothis virescens (F.), larvae caged on different plant structures for varying lengths of exposure. Percentages of larvae surviving were measured on Bt cottons expressing Cry1Ab and CrylAc protein. Plant structure (terminal, leaf, square or boll) did not affect larval survival, and survival did not differ significantly between CrylAb and CrylAc cottons. Larvae exposed to Bt cotton for only 24 h had higher initial survival than larvae exposed for 48, 72 and 96 h. Larvae first exposed to Bt cotton at 4 d of age had higher survival than those first exposed as neonate or 2-d-old larvae. Survivorship of neonate and 4-d-old larvae exposed to CrylAc cotton was significantly reduced with only 48 h of exposure to the insecticidal plants. Seven-day-old larvae exhibited no significant reduction in survivorship with exposure to CrylAc cotton for 48 h.

scholarly journals Host plant and population determine the fitness costs of resistance to Bacillus thuringiensis

2006 ◽  
Vol 3 (1) ◽  
pp. 83-86 ◽  
Author(s):  
Ben Raymond ◽  
Ali H Sayyed ◽  
Denis J Wright
Keyword(s):  
Bacillus Thuringiensis ◽  
Host Plant ◽  
Environmental Quality ◽  
Species Interactions ◽  
Diamondback Moth ◽  
Larval Survival ◽  
Plant Quality ◽  
Relative Fitness ◽  
Fitness Costs ◽  
Fitness Parameters

Novel adaptations often cause pleiotropic reductions in fitness. Under optimal conditions individual organisms may be able to compensate for, or reduce, these fitness costs. Declining environmental quality may therefore lead to larger costs. We investigated whether reduced plant quality would increase the fitness costs associated with resistance to Bacillus thuringiensis in two populations of the diamondback moth Plutella xylostella . We also measured the rate of decline in resistance on two host-plant ( Brassica ) species for one insect population (Karak). Population×plant species interactions determined the fitness costs in this study. Poor plant quality increased the fitness costs in terms of development time for both populations. However, fitness costs seen in larval survival did not always increase as plant quality declined. Both the fitness and the stability experiment indicated that fitness costs were higher on the most suitable plant for one population. Theoretically, if the fitness cost of a mutation interacts additively with environmental factors, the relative fitness of resistant insects will decrease with environmental quality. However, multiplicative costs do not necessarily increase with declining quality and may be harder to detect when fitness parameters are more subject to variation in poorer environments.

Influence of Planting Stock Clove Size, Nitrogen Rate, and Planting Method on Elephant Garlic Production

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 517f-518
Author(s):  
Jeanine M. Davis
Keyword(s):  
Survival Rates ◽  
Ground Level ◽  
Winter Survival ◽  
Nitrogen Rate ◽  
Planting Stock ◽  
Mild Winter ◽  
Allium Ampeloprasum ◽  
Planting Methods ◽  
Planting Method ◽  
Nitrogen Rates

To produce large elephant garlic (Allium ampeloprasum L.) bulbs in the southeastern United States, stock cloves must be planted in the fall. During extremely cold winters, however, winter survival rates can be very low. A 2-year study was undertaken to examine practices to increase winter survival rates. Two clove sizes (≤20 g or >20 g), three nitrogen rates (112, 224, and 336 kg/ha), and three planting methods (flat, mulched, and hilled) were tested in a RCB design with four replications. For all planting methods, cloves were set in a shallow trench and covered with soil to ground level. This was also the flat treatment. For the mulched treatment, 7 cm of straw was spread on top. For the hilled treatment, soil was mounded 10 to 15 cm high over the ground level. Cloves were planted in early October and harvested in mid-June. Use of large planting stock cloves increased winter survival rates during the harsh winter, but had no effect during the mild winter. Both years, winter survival was reduced with the flat treatment. Yields of marketable bulbs were 4 to 5 times higher when >20 g cloves were planted than when ≤20 g cloves were used. Nitrogen rate and planting method had no effect on yields. The >20 g cloves also produced larger bulbs than the smaller cloves. Of the three planting methods, the flat treatment produced the smallest bulbs. Bulbs were much larger following the mild winter than the harsh winter.

Factors Affecting Winter Survival of Johnsongrass (Sorghum halepense) Rhizomes

1991 ◽  
Vol 5 (1) ◽  
pp. 108-110 ◽  
Author(s):  
Robert G. Hartzler ◽  
Art Gover ◽  
Joanne Stellingwerf
Keyword(s):  
Survival Rates ◽  
Winter Survival ◽  
Sorghum Halepense ◽  
Factors Affecting ◽  
Rhizome Biomass ◽  
Depth Of Burial

There were no differences in johnsongrass rhizome winter survival at central and southeastern locations in Pennsylvania in 1988 or 1989. At a 6-cm depth of burial, survival rates of 5 and 25% were found for rhizome segments 7.5 and 15.0 cm in length, respectively. Survival rates for rhizomes buried 25 cm averaged 86%, with no difference in survival between rhizome lengths. The majority of rhizome biomass produced by the biotype used in these studies was found at soil depths allowing a high percentage of survival.

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