A field study was conducted to evaluate the efficacy of two most virulent native isolates of inse... more A field study was conducted to evaluate the efficacy of two most virulent native isolates of insect pathogenic fungi (Metarhizium anisopliae and Beauveria bassiana) and compared with four commercial biopesticides against Chickpea pod borer (Helicoverpa armigera Hubner) at Chitwan, Nepal. The number of H. armigera lavae observed in plots treated with M. anisopliae and B. bassiana were significantly lesser than the control plots during vegetative, flowering and pod setting stage of chickpea. Similarly, the chickpea yield was significantly higher in the plots treated with M. anisopliae and B. bassiana than control, however lesser than NPV and Bt treated plots. Based on this study, the native isolates have potential to be a biocontrol agent against the H. armigera in Nepal.
The red imported fire ant, Solenopsis invicta, is an invasive species that has been introduced in... more The red imported fire ant, Solenopsis invicta, is an invasive species that has been introduced into the United States and more recently into several countries in the Asian-Pacific region. The foraging dynamics of this pest ant is important in understanding its interactions with native ant species and in devising the most effective toxic bait control methods. In this study the effect of worker density, size of the foraging area, the number of food lures, duration of experiments, and the effect of the queen on foraging activity were investigated under laboratory conditions. The results showed that of the four ant densities investigated (very small, small, medium and high) the medium ant density most consistently had more workers at the food lures than the other ant density situations. The percentage of worker ants at the food lures was negatively correlated with an increase in foraging territory size for all four worker ant densities. Significantly fewer foragers were observed in the foraging areas when a queen was present, then when the queen was absent. In addition, when number of food lures was increased from 1 to 12, the mean number of workers found at the lures was significantly higher when four food lures were present. Furthermore, the number of worker ants observed on the food lures increased for the first 2.5 h and then decreased with time. The study suggests that observations of foraging activity could be restricted to 2.5 h. These data lay the ground work for further studies in optimizing the effectiveness of fire ant bait toxicants.
The preference of red imported fire ants, Solenopsis invicta, for microencapsulated (MC) pyriprox... more The preference of red imported fire ants, Solenopsis invicta, for microencapsulated (MC) pyriproxifen based corn grit baits (P-bait) was conducted in laboratory and field conditions. A positive correlation between the microencapsulation rate and water tolerance ability of P-bait was observed. A 20% increment of water tolerance ability of P-baits was observed when P-baits were microencapsulated with 5% poly-ε-caprolactone. The microencapsulated and wet P-baits were less preferred than normal P-baits by the fire ants either in laboratory or field conditions. Based upon these results, poly-ε-caprolactone coated fire ant baits cannot be considered as perfect fire ant baits.
A new water-resistant fire ant bait (T-bait; cypermethrin 0.128%) consisting of dried distillers ... more A new water-resistant fire ant bait (T-bait; cypermethrin 0.128%) consisting of dried distillers grains with solubles (DDGS) as a carrier was developed and evaluated against a standard commercial bait (Advion; indoxacarb 0.045%) under both laboratory and field conditions. When applying the normal T-bait or Advion in the laboratory, 100% of Solenopsis invicta Buren worker ants were killed within 4 days. However, when the T-bait and Advion were wetted, 70.6 and 39.7% of the ants were killed respectively. Under field conditions, dry T-bait and dry Advion had almost the same efficacy against ant colonies. However, when T-bait and Advion came in contact with water, the former's ability to kill S. invicta colonies in the field was only marginally reduced, while Advion lost virtually all of its activity. In addition, DDGS was also shown to be compatible with a number of other insecticides, such as d-allethrin, permethrin and pyrethrin. Based on its properties of remaining attractive to the fire ants when wetted, combined with its ant-killing abilities both in the laboratory and in the field, T-bait is an efficient fire ant bait, especially under moist conditions.
The native isolates of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, wer... more The native isolates of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, were evaluated against the third instar larvae of the chickpea pod borer, Helicoverpa armigera, for mortality, infection rate and LT 50 under laboratory conditions in Nepal. Out of four isolates of M. anisopliae and two isolates of B. bassiana evaluated, M. anisopliae M1 and B. bassiana B3, were the most virulent ones of all isolates evaluated, with a concentration at 10 7 conidia/ml. The M1 and B3 isolates had the highest mortality rates and required the shortest time to kill the larvae of H. armigera. After treatment with M1 and B1 isolates for 10 days, the larval mortality exceeded 85%. These data lay the ground work for further studies in optimizing the effectiveness of indigenous virulent isolates, M. anisopliae M1 and B. bassiana B3 against H. armigera in Nepal.
This study was designed to understand the effects of the interspeciÞc competition between red imp... more This study was designed to understand the effects of the interspeciÞc competition between red imported Þre ant, Solenopsis invicta Buren and two native ant species, Pheidole fervens Smith and Monomorium chinense Santschi, by conducting colony interference and individual confrontation tests under laboratory conditions. The colony interference test showed that both native ant species, owing to their numerical advantage, killed the Solenopsis invicta virus-1 (SINV-1)Ðinfected or healthy queens of S. invicta. SigniÞcantly less time was required for M. chinense to kill all SINV-1Ðinfected S. invicta compared with the time required to kill the healthy S. invicta. Compared with healthy S. invicta, SINV-1Ðinfected S. invicta spent a longer time eliminating the P. fervens colonies. In confrontation tests, M. chinense killed a signiÞcantly higher number of infected S. invicta minors than they did healthy minors, but the number of S. invicta majors (either infected or healthy) killed was substantially less. This study found that the viral infection weakened the competitive ability of S. invicta and made them prone to be eliminated by M. chinense but not by P. fervens.
Host searching behavior of Ganaspidium utilis (Beardsley) (Hymenoptera: Eucoilidae) was observed ... more Host searching behavior of Ganaspidium utilis (Beardsley) (Hymenoptera: Eucoilidae) was observed when G. utilis females searched and oviposited on the late 2 nd or early 3 rd instar of Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) larvae in the laboratory. It was observed that G. utilis females used mines made by their hosts as trails to search for their hosts. A G. utilis female was able to discriminate whether or not mines had previously been searched. It was observed that G. utilis females followed a series of fixed action patterns comprised of walking to find a host, holding the antennae upward when a host was accepted, ovipositor probing to determine the suitability of the host and ovipositor penetrating as culmination of the host searching behavior.
The abundance and diversity of scarabaeid beetles was examined at five different farming areas in... more The abundance and diversity of scarabaeid beetles was examined at five different farming areas in Nepal. Light traps were used to monitor the beetles for 12 months. A total of 4708 scarabaeid beetles of 29 genera and 77 species were trapped during the one year duration of this study. The five most common scarabaeid species in the study areas were Adoretus coronatus Burmeister, Maladera thomsoni (Brenske), Anomola bilobata Arrow, Holotrichia nigricollis Brenske and Anomola dimidiata (Hope). They accounted for 58.81% of all individuals collected. An inventory of scarabaeid beetles associated with the five different farming areas in Nepal was developed. This data creates a base for further studies of beetles and for the developement of conservation and management strategies in Nepal.
Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were isolated from soils and... more Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were isolated from soils and white grubs cadavers from farmlands in Nepal. In the mortality studies, 8 isolates infected more than 80% of the grubs, another 65 isolates infected more than 50% of the grubs and the rest of the isolates had a low level of pathogenicity with 10 7 conidia/mL concentration. Five isolates were highly pathogenic against third instar larvae of Maladera affinis. The isolate, M. anisopliae M1 was the most virulent strain of all the evaluated isolates. LT 50 of the tested isolates varied between 2-9 weeks. Isolates M1 and M6 had the highest mortality rates and required the shortest time to kill the white grub larvae. Assessment with fungus inocula with conidiospores and blastospores against three different instars of white grubs showed that a significantly larger numbers of second instar larvae were infected with the fungi than first and third instars. A comparison of indigenous and commercial isolates of M. anisopliae and B. bassiana with third instar larvae of Anomala dimidiata, Adoretus lasiopygus and Phyllognathus dionysius demonstrated that native isolates were more virulent to the above three white grubs species tested than the exotic fungi. Based on this study, the indigenous virulent isolates have the potential to be biocontrol agents against white grubs in Nepal.
A field study was conducted to evaluate the efficacy of two most virulent native isolates of inse... more A field study was conducted to evaluate the efficacy of two most virulent native isolates of insect pathogenic fungi (Metarhizium anisopliae and Beauveria bassiana) and compared with four commercial biopesticides against Chickpea pod borer (Helicoverpa armigera Hubner) at Chitwan, Nepal. The number of H. armigera lavae observed in plots treated with M. anisopliae and B. bassiana were significantly lesser than the control plots during vegetative, flowering and pod setting stage of chickpea. Similarly, the chickpea yield was significantly higher in the plots treated with M. anisopliae and B. bassiana than control, however lesser than NPV and Bt treated plots. Based on this study, the native isolates have potential to be a biocontrol agent against the H. armigera in Nepal.
The red imported fire ant, Solenopsis invicta, is an invasive species that has been introduced in... more The red imported fire ant, Solenopsis invicta, is an invasive species that has been introduced into the United States and more recently into several countries in the Asian-Pacific region. The foraging dynamics of this pest ant is important in understanding its interactions with native ant species and in devising the most effective toxic bait control methods. In this study the effect of worker density, size of the foraging area, the number of food lures, duration of experiments, and the effect of the queen on foraging activity were investigated under laboratory conditions. The results showed that of the four ant densities investigated (very small, small, medium and high) the medium ant density most consistently had more workers at the food lures than the other ant density situations. The percentage of worker ants at the food lures was negatively correlated with an increase in foraging territory size for all four worker ant densities. Significantly fewer foragers were observed in the foraging areas when a queen was present, then when the queen was absent. In addition, when number of food lures was increased from 1 to 12, the mean number of workers found at the lures was significantly higher when four food lures were present. Furthermore, the number of worker ants observed on the food lures increased for the first 2.5 h and then decreased with time. The study suggests that observations of foraging activity could be restricted to 2.5 h. These data lay the ground work for further studies in optimizing the effectiveness of fire ant bait toxicants.
The preference of red imported fire ants, Solenopsis invicta, for microencapsulated (MC) pyriprox... more The preference of red imported fire ants, Solenopsis invicta, for microencapsulated (MC) pyriproxifen based corn grit baits (P-bait) was conducted in laboratory and field conditions. A positive correlation between the microencapsulation rate and water tolerance ability of P-bait was observed. A 20% increment of water tolerance ability of P-baits was observed when P-baits were microencapsulated with 5% poly-ε-caprolactone. The microencapsulated and wet P-baits were less preferred than normal P-baits by the fire ants either in laboratory or field conditions. Based upon these results, poly-ε-caprolactone coated fire ant baits cannot be considered as perfect fire ant baits.
A new water-resistant fire ant bait (T-bait; cypermethrin 0.128%) consisting of dried distillers ... more A new water-resistant fire ant bait (T-bait; cypermethrin 0.128%) consisting of dried distillers grains with solubles (DDGS) as a carrier was developed and evaluated against a standard commercial bait (Advion; indoxacarb 0.045%) under both laboratory and field conditions. When applying the normal T-bait or Advion in the laboratory, 100% of Solenopsis invicta Buren worker ants were killed within 4 days. However, when the T-bait and Advion were wetted, 70.6 and 39.7% of the ants were killed respectively. Under field conditions, dry T-bait and dry Advion had almost the same efficacy against ant colonies. However, when T-bait and Advion came in contact with water, the former's ability to kill S. invicta colonies in the field was only marginally reduced, while Advion lost virtually all of its activity. In addition, DDGS was also shown to be compatible with a number of other insecticides, such as d-allethrin, permethrin and pyrethrin. Based on its properties of remaining attractive to the fire ants when wetted, combined with its ant-killing abilities both in the laboratory and in the field, T-bait is an efficient fire ant bait, especially under moist conditions.
The native isolates of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, wer... more The native isolates of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, were evaluated against the third instar larvae of the chickpea pod borer, Helicoverpa armigera, for mortality, infection rate and LT 50 under laboratory conditions in Nepal. Out of four isolates of M. anisopliae and two isolates of B. bassiana evaluated, M. anisopliae M1 and B. bassiana B3, were the most virulent ones of all isolates evaluated, with a concentration at 10 7 conidia/ml. The M1 and B3 isolates had the highest mortality rates and required the shortest time to kill the larvae of H. armigera. After treatment with M1 and B1 isolates for 10 days, the larval mortality exceeded 85%. These data lay the ground work for further studies in optimizing the effectiveness of indigenous virulent isolates, M. anisopliae M1 and B. bassiana B3 against H. armigera in Nepal.
This study was designed to understand the effects of the interspeciÞc competition between red imp... more This study was designed to understand the effects of the interspeciÞc competition between red imported Þre ant, Solenopsis invicta Buren and two native ant species, Pheidole fervens Smith and Monomorium chinense Santschi, by conducting colony interference and individual confrontation tests under laboratory conditions. The colony interference test showed that both native ant species, owing to their numerical advantage, killed the Solenopsis invicta virus-1 (SINV-1)Ðinfected or healthy queens of S. invicta. SigniÞcantly less time was required for M. chinense to kill all SINV-1Ðinfected S. invicta compared with the time required to kill the healthy S. invicta. Compared with healthy S. invicta, SINV-1Ðinfected S. invicta spent a longer time eliminating the P. fervens colonies. In confrontation tests, M. chinense killed a signiÞcantly higher number of infected S. invicta minors than they did healthy minors, but the number of S. invicta majors (either infected or healthy) killed was substantially less. This study found that the viral infection weakened the competitive ability of S. invicta and made them prone to be eliminated by M. chinense but not by P. fervens.
Host searching behavior of Ganaspidium utilis (Beardsley) (Hymenoptera: Eucoilidae) was observed ... more Host searching behavior of Ganaspidium utilis (Beardsley) (Hymenoptera: Eucoilidae) was observed when G. utilis females searched and oviposited on the late 2 nd or early 3 rd instar of Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) larvae in the laboratory. It was observed that G. utilis females used mines made by their hosts as trails to search for their hosts. A G. utilis female was able to discriminate whether or not mines had previously been searched. It was observed that G. utilis females followed a series of fixed action patterns comprised of walking to find a host, holding the antennae upward when a host was accepted, ovipositor probing to determine the suitability of the host and ovipositor penetrating as culmination of the host searching behavior.
The abundance and diversity of scarabaeid beetles was examined at five different farming areas in... more The abundance and diversity of scarabaeid beetles was examined at five different farming areas in Nepal. Light traps were used to monitor the beetles for 12 months. A total of 4708 scarabaeid beetles of 29 genera and 77 species were trapped during the one year duration of this study. The five most common scarabaeid species in the study areas were Adoretus coronatus Burmeister, Maladera thomsoni (Brenske), Anomola bilobata Arrow, Holotrichia nigricollis Brenske and Anomola dimidiata (Hope). They accounted for 58.81% of all individuals collected. An inventory of scarabaeid beetles associated with the five different farming areas in Nepal was developed. This data creates a base for further studies of beetles and for the developement of conservation and management strategies in Nepal.
Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were isolated from soils and... more Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were isolated from soils and white grubs cadavers from farmlands in Nepal. In the mortality studies, 8 isolates infected more than 80% of the grubs, another 65 isolates infected more than 50% of the grubs and the rest of the isolates had a low level of pathogenicity with 10 7 conidia/mL concentration. Five isolates were highly pathogenic against third instar larvae of Maladera affinis. The isolate, M. anisopliae M1 was the most virulent strain of all the evaluated isolates. LT 50 of the tested isolates varied between 2-9 weeks. Isolates M1 and M6 had the highest mortality rates and required the shortest time to kill the white grub larvae. Assessment with fungus inocula with conidiospores and blastospores against three different instars of white grubs showed that a significantly larger numbers of second instar larvae were infected with the fungi than first and third instars. A comparison of indigenous and commercial isolates of M. anisopliae and B. bassiana with third instar larvae of Anomala dimidiata, Adoretus lasiopygus and Phyllognathus dionysius demonstrated that native isolates were more virulent to the above three white grubs species tested than the exotic fungi. Based on this study, the indigenous virulent isolates have the potential to be biocontrol agents against white grubs in Nepal.
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