Lekhnath Kafle

Toxicity and Repellency of Compounds From Clove (Syzygium aromaticum) to Red Imported Fire Ants Solenopsis invicta (Hymenoptera: Formicidae)

ABSTRACT The toxicity and repellency of the bioactive chemicals of clove (Syzygium aromaticum) powder, eugenol, eugenol acetate, and beta-caryophyllene were evaluated against workers of the red imported fire ant, Solenopsis invicta Buren. Clove powder applied at 3 and 12 mg/cm2 provided 100% ant mortality within 6 h, and repelled 99% within 3 h. Eugenol was the fastest acting compound against red imported fire ant compared with eugenol acetate, beta-caryophyllene, and clove oil. The LT50 values inclined exponentially with the increase in the application rate of the chemical compounds tested. However, repellency did not increase with the increase in the application rate of the chemical compounds tested, but did with the increase in exposure time. Eugenol, eugenol acetate, as well as beta-caryophyllene and clove oil may provide another tool for red imported fire ant integrated pest management, particularly in situations where conventional insecticides are inappropriate.

A new fire ant (Hymenoptera: Formicidae) bait base carrier for moist conditions

BACKGROUND 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. RESULTS 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 formers 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. CONCLUSION 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.

Efficacy of Beauveria bassiana against the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae), in Taiwan

BACKGROUND Combining biological control and chemical control could be used for controlling red imported fire ant (RIFA), Solenopsis invicta, more effectively. Beauveria bassiana F256, a local strain from Taiwan, was evaluated for its efficacy in the control of S. invicta under both laboratory and field conditions. RESULTS The efficacies of different doses of B. bassiana (Bb) using direct application and bait formulation methods were compared. The number of RIFA workers killed by the direct application of Bb or by bait were significantly higher than those of the control, with different rates of efficacy under laboratory conditions. Under field conditions, the direct application of Bb into RIFA mounds was more efficient in inactivating the mounds than the bait application. CONCLUSION It was shown that B. bassiana is able to control S. invicta under both laboratory and field conditions and can be used as a biocontrol agent against RIFA in Taiwan.

Virulence of Metarhizium anisopliae and Beauveria bassiana against Common White Grubs in Nepal

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 107 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. LT50 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.

Interspecific Competition between Solenopsis invicta and Two Native Ant Species, Pheidole fervens and Monomorium chinense

ABSTRACT This study was designed to understand the effects of the interspecific competition between red imported fire 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)-infected or healthy queens of S. invicta. Significantly less time was required for M. chinense to kill all SINV-1-infected S. invicta compared with the time required to kill the healthy S. invicta. Compared with healthy S. invicta, SINV-1-infected S. invicta spent a longer time eliminating the P. fervens colonies. In confrontation tests, M. chinense killed a significantly 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.

Effect of Surfaces on the Foraging Efficiency of Solenopsis invicta (Hymenoptera: Formicidae)

The effects of different surfaces on the foraging efficiency of Solenopsis invicta workers were observed. The results indicated that the foragers of S. invicta were more efficient when they foraged on hard and smooth plastic surfaces than on soil surfaces. Similarly, foragers of S. invicta were less efficient when they encountered obstacles such as gravel or grass. The foraging activities of the S. invicta workers were considerably less on grass than on gravel, and fire ant workers from wild colonies were more efficient than workers from one-year-old laboratory colonies.

Determining the most effective concentration of cypermethrin and the appropriate carrier particle size for fire ant (Hymenoptera: Formicidae) bait.

BACKGROUND The purpose of this study was to determine the most effective particle size of DDGS (distillers dried grains with solubles) as fire ant bait carrier, as well as the most effective concentration of cypermethrin as a toxicant against the red imported fire ant (RIFA) Solenopsis invicta Buren under laboratory conditions. RESULTS The DDGS particle size did not affect the fire ants preference for the bait, but it did affect the mass of DDGS being carried back to the nest. The size of the DDGS particles and the mass of DDGS being carried back to the nest were positively correlated. The most efficient particle size of DDGS was 0.8-2 mm. The concentration of cypermethrin has a specific range for killing fire ants in an efficient manner. Neither a very low nor a very high concentration of cypermethrin was able to kill fire ants efficiently. The most effective concentration of cypermethrin was 0.13% in DDGS when mixed with 15% shrimp shell powders and 11% soybean oil. CONCLUSION Based on its ability to kill fire ants when mixed with cypermethrin, as well as the advantage of having a larger area coverage when sprayed in the field, DDGS as the carrier and cypermethrin as the toxicant can be considered to be an efficient way to prepare fire ant bait for controlling fire ants in infested areas.

A new baited trap for monitoring Solenopsis invicta (Formicidae: Hymenoptera) in Taiwan

This study investigated the efficacy of the newly designed hotdog-baited trap (B-trap) to detect red imported fire ants (RIFA), Solenopsis invicta Buren, under field conditions in Taiwan. Among the seven different food lures examined using RIFA, hotdogs were the most preferred by the ants, followed by shrimp crackers and potato chips. Hotdogs were therefore used in the B-trap, and a comparison was made with the traditional pitfall trap (A-trap) to determine their efficacy in trapping RIFA. Field data revealed that the B-trap was more efficient than the A-trap based on its ability to trap more RIFA under field conditions and its ease of use. Thus, it was concluded that the B-trap is an efficient trap for long-term RIFA monitoring in Taiwan.

Abundance and Diversity of Scarabaeid Beetles (Coleoptera: Scarabaeidae) in Different Farming Areas in Nepal

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.

Efficacy of Natural Products Against Callosobruchus chinensis (Coleoptera: Bruchidae) in Nepal

ABSTRACT This study was conducted to determine the efficacy of local natural products against the beetle, Callosobruchus chinensis L. (Coleoptera: Bruchidae), in stored chickpea Cicer arietinum L. (Fabaceae) in Chitwan, Nepal. Five natural products and one synthetic pesticide (Malathion) and two storage regimes (aluminum sheet bin vs. jute bags with plastic lining) were tested for their effect on stored pulse with respect to damage by C. chinensis. The five natural products included Xanthoylum armatum DC (Rutaceae) fruit powder, Acorus calamus L. (Araceae) rhizome powder, Cinnamom camphora L. (Lauraceae) balls, oil of Sesamum indicum L. (Pedaliaceae), and leaf powder of Azadirachta indica A. Juss. (Meliaceae). Treatments of stored pulses with natural products or with Malathion all caused significantly higher mortality of C. chinensis at 15 d after treatment (DAT) than stored pulses receiving no treatments. The balls of C. camphora, rhizome powder of A. calamus and sesame oil outperformed all other treatments, including the Malathion at 45 and 75 DAT and resulted in significantly reduced damage or deterioration of stored pulses compared with other treatments. Storage regimes performed similarly, although the jute bags did protect seed integrity for some treatments. Our results indicate that incorporating these natural products into stored pulses can protect the seeds from C. chinensis for up to two generations, something that Malathion cannot do. These products are readily available to most farmers in the region and their use will lead to 1) reduction of losses to significant stored product pests, and 2) a reduction of contamination of foodstuffs and the environment by synthetic pesticides like Malathion.