Biomedical subjects

M S Mulla

Publications and source records attributed to M S Mulla.

At least 19 recordsLinked to original sources

PubMed1998

Ovicidal activity of neem products (azadirachtin) against Culex tarsalis and Culex quinquefasciatus (Diptera: Culicidae).

Bioactive compounds contained in the seed kernel and other parts of the neem tree (Azadirachta indica A. Juss) have been found to show insecticidal activities and other effects in many species of insects. These activities include antifeedancy, growth regulation, fecundity suppression, male sterility, oviposition repellency, changes in biological fitness such as loss of flying ability, immunodepression, enzyme inhibition, splitting of biological rhythms, and so forth. We investigated the ovicidal effects of various formulations of azadrirachtin (AZ) against the mosquitoes Culex tarsalis Coquillett and Culex quinquefasciatus Say. The formulations tested were wettable powder Azad WP10, emulsifiable concentrate Azad EC4.5, and technically pure AZ. The ovicidal activity of the test neem products was influenced by concentration of AZ, age of the egg rafts, and age of the neem preparations. Other factors such as formulation and mosquito species were also involved in the degree of ovicidal activity. When the egg rafts were deposited directly in fresh neem suspension and left there for 4 h before transfer to untreated water, 1 ppm of AZ produced almost 100% mortality in eggs. When egg rafts aged for 0, 4, 8, 12, and 24 h were exposed to 10 ppm neem suspensions for 36 h, the ovicidal activity was only attained in the egg rafts deposited directly (0 h old) in the neem suspension, not in those with ages of 4-24 h. On aging, depending on the formulations and mosquito species, the neem suspensions at 1 ppm completely lost ovicidal activity within 7-20 days. The egg rafts of Cx. quinquefasciatus were more susceptible to the test neem products than those of Cx. tarsalis. The formulated neem products were more persistent and effective than the technical AZ. The wettable powder (WP) formulation was slightly more persistent and effective than the emulsifiable concentrate (EC). The ovicidal activity of the neem products against mosquitoes from the current research clearly demonstrated the potential of neem products as possible ovicides against Culex mosquitoes.

Animals↗

PubMed1998

Field evaluation of controlled release pellet formulation of methoprene against chironomid midges in man-made lakes.

The duration of the efficacy of 4% methoprene pellets against emergence of chironomid midges, Chironomus stigmaterus Say, Goeldichironomus amazonicus (Fittkau) and Tanypus imperialis Sublette, in man-made lakes supplied with tertiary effluent water in Palm Desert, California, was dose dependent. For C. stigmaterus and T. imperialis, the rate of 4.5 kg/ha of the controlled release pellet formulation of 4% methoprene yielded > 90% control for 3 wk and 75% control in the 4th week, the rate of 3.4 kg/ha provided > 90% control for 2 wk, and the rate of 2.25 kg/ha provided control for 1 wk. Goeldichironomus amazonicus was under 90% control for 2 wk at the rate of 4.5 kg/ha and 1 wk at the rates of 3.4 kg/ha and 2.25 kg/ha.

Animals↗

PubMed1997

Biological fitness of Culex quinquefasciatus (Diptera:Culicidae) susceptible and resistant to Bacillus sphaericus.

Biological fitness of laboratory and field-collected strains of southern house mosquito, Culex quinquefasciatus Say, susceptible and resistant (37- and 31-fold upon selection) to the microbial agent, Bacillus sphaericus, were compared in the absence of B. sphaericus. The resistant strains showed significantly lower fecundity and fertility, but they had significantly higher survival rates than the susceptible strains. The preadult stages from females of resistant strains developed at slightly faster rates than those of the susceptible strains, which could result in a shorter generation time. However, lower fecundity was likely to lead to overall lower population growth rates than in the susceptible strains. Data provided evidence that the resistant strains exhibited fitness disadvantages in the absence of B. sphaericus. We suggest that once resistance to B. sphaericus is detected in the field, its use should be discontinued until the mosquito population becomes susceptible again because of the decline in number of resistant individuals. A strategy of resistance management by rotation of insecticides is discussed.

Animals↗

PubMed1997

Nutritional reserves, body weight, and starvation tolerance of autogenous and anautogenous strains of Culex tarsalis (Diptera:Culicidae).

The nutritional reserves and body weight of autogenous and anautogenous strains of Culex tarsalis Coquillett were determined for 4th instars, pupae, females, and males. Starvation tolerance and survivorship of adult females and males also were studied. The autogenous individuals contained significantly greater amounts of total lipids (except the total lipids in 4th instars), total carbohydrates, glycogen, and total proteins, which resulted in a heavier mean body weight of autogenous than anautogenous mosquitoes (except the fresh weight in pupae). Results of the body fluid coefficient determination were inconclusive. Nutritional reserves in the immature stages, especially the pupal stage, were significantly greater (except the total proteins in 4th instars and female adults) than those in the adult stage. There were no significant differences in median longevity between autogenous and anautogenous females, and between autogenous and anautogenous males, provided with distilled water alone after emergence. The median longevity of females and males was significantly different in both autogenous and anautogenous strains. Our findings strongly indicate a relationship between autogenous reproduction and differences in nutritional reserves of autogenous and anautogenous strains.

Animals↗

PubMed1997

Quantitative determination of free amino acids in the hemolymph of autogenous and anautogenous strains of Culex tarsalis (Diptera: Culicidae).

Autogenous and anautogenous strains were selected from the egg rafts of Culex tarsalis Coquillett collected from Coachella Valley, California. In autogenous (21-25 generations) and anautogenous (0-4 generations) strains used for hemolymph free amino acid analysis, the autogenous oviposition rates were 73.6-83.6% and 2.7-3.9%, the proportions of females undergoing autogenous ovarian development 120 h postemergence were 75.6 and 8.9%, respectively. To study the presence and quantities of free amino acids and explore their relationship to autogenous ovarian development, the 6 legs of females from both autogenous and anautogenous strains were removed at the coxo-femoral joints, and hemolymph was collected by centrifuging the bodies of 50-100 females. Proteins in the hemolymph were precipitated with 10% sulphosalicylic acid. On days 1, 4, 7, and 10 postemergence, a total of 17 free amino acids was found in females from the autogenous strain, and a total of 16 was found in females from the anautogenous strain in which asparagine (Asn) was absent. Comparisons of free amino acid concentrations between these 2 strains indicated that there were significant differences in total free amino acids and 13 individual free amino acids except Glu, Gln, Pro, and Met on day 1, total free amino acids and 14 individual free amino acids except Gln, Pro, and on day 4, and total free amino acids and 12 individual free amino acids except Asp, Glu, Gln, Pro, and Met on day 7 postemergence. There were no significant differences in the concentrations of individual and total free amino acids on day 10 postemergence. Female age affected free amino acid content in the autogenous strain, where total free amino acids and 14 individual free amino acid content in the autogenous strain, where total free amino acids and 14 individual free amino acids increased from day 1, peaked on day 4, declined on day 7, and declined further on day 10 postemergence. In the anautogenous strain, only total free amino acids and Ser, Gly, Ala, and Leu exhibited age-dependent changes in concentration, and the magnitude of changes in concentration was less than that in autogenous strain. Conclusively, autogenous ovarian development was the major reason for the changes in hemolymph free amino acid concentration postemergence. The current and previous findings indicate that the free amino acids, Arg, Gly, Ile, Leu, Lys, Phe, Ser, Thr, and Val putatively may be essential for vitellogenesis in mosquitoes.

Amino Acids↗

PubMed1997

Organic enrichment of breeding sources for sustained productivity of mosquitoes (Diptera: Culicidae).

Alfalfa pellets and chicken lay mash were used to obtain polluted water for continuous and sustained oviposition by Culex mosquitoes. Water in fiberglass tubs enriched with 0.1 and 0.25 percent (w/v) of either material received heavy oviposition by gravid mosquitoes. The higher level of enrichment resulted in greater oviposition than lower concentrations which in turn received significantly more oviposition than the controls with no enrichment. Oviposition continued in the enriched tubs for more than 43 days where Culex quinquefasciatus and Culex stigmatosoma constituted a major proportion of the eggs laid while Culex tarsalis, as expected, oviposited at much lower rates than the other two species. Supplemental enrichment of mosquito breeding sources with organic material can thus provide uniform and sustained availability of some mosquito larvae for the evaluation of persistent control agents and other related studies.

Animals↗

PubMed1997

Selection-dependent trends of autogeny and blood feeding in an autogenous strain of Culex tarsalis (Diptera:Culicidae).

During successive en masse selection of autogeny in Culex tarsalis from parental to 20th generation, the autogenous oviposition capacity changed as follows: mean number of egg rafts/female and mean number of eggs/female increased significantly, from 0.11 to 0.56 and from 6.2 to 20.2, respectively; the mean size of the egg rafts decreased significantly, from 56.2 to 36 eggs/raft; autogeny rates increased significantly, from 18.6 to 65.2%; mean number of autogenous follicles/female decreased significantly, from 57.4 to 34; the hatching rate of autogenous egg rafts reduced significantly, from 88.3 to 75.4%; and the feeding rates of the females on a blood meal source during the 7th day postemergence increased significantly, from 62.8 to 71.1%. The autogeny rate determined by ovarian dissection was higher than that indicated by actual oviposition. As the age of females increased during the observed 10-day oviposition period, the mean number of egg rafts/female, the mean number of eggs/female, and the mean number of eggs/raft decreased successively, and scattered "light color" egg rafts became more common. Successive en masse selection enhanced autogeny and strengthened the bloodfeeding tendency in this facultative autogenous species.

Animals↗

PubMed1997

Field trials with Bacillus sphaericus formulations against polluted water mosquitoes in a suburban area of Bangkok, Thailand.

Two newly developed Bacillus sphaericus larvicidal formulations, VectoLex CG (corncob granules) and VectoLex WDG (water dispersible granules), were tested against Culex quinquefasciatus larvae in 4 highly polluted breeding sites in Thailand. VectoLex CG, applied at rates of 0.5-2 g/m2, gave satisfactory to complete control of late-instar larvae and pupae for up to 4 wk after treatment. The VectoLex WDG, which had higher potency and was applied at rates of 0.1-0.5 g/m2, gave satisfactory control for 1-4 wk after treatment. Among the factors influencing longevity of control were dosage of a given formulation, precipitation, and flooding of the treated sites; the latter had the greatest impact. Presence of larvivorous fish did not seem to influence larval populations because there were heavy populations of mosquito larvae present in the test sites in the presence of moderate numbers of fish before the application of B. sphaericus treatments.

Animals↗

PubMed1997

Physiological aspects of autogeny in Culex tarsalis (Diptera: Culicidae): influences of sugar-feeding, mating, body weight, and wing length.

Sugar feeding and mating promoted the expression of autogeny in Culex tarsalis. In sugar-fed cohorts fed 5, 10, and 20% sucrose solution, the mean number of egg rafts/female, mean number of eggs/raft, mean number of eggs/female, mean number of autogenous follicles/female, and the autogeny rate were all significantly greater than those in sugar-deprived cohorts. There were no significant differences in these parameters among the sugar-fed groups of 5, 10, and 20%. Similarly, magnitudes of the parameters mentioned above in female-male cohorts were significantly higher than those in female-alone cohorts. There was no difference in the hatching rate of the autogenous egg rafts in the cohorts fed on different sucrose solutions and the female-male cohorts, while it was 0 in male-deprived cohorts. There were positive correlations between mean emergence weight and mean number of autogenous eggs/female (r2 = 0.69), mean emergence weight and mean number of autogenous follicles/female (r2 = 0.75), mean wing length and mean number of autogenous eggs/female (r2 = 0.64), and mean wing length and mean number of autogenous follicles/female (r2 = 0.63). The regression analysis of the data indicated that females with emergence weights < 1.92 mg could not oviposit autogenously, and those with emergence weights < 1.89 mg could not develop the ovaries autogenously. Females with wing lengths < 2.89 mm could not oviposit autogenously and those with the wing length of < 2.83 mm could not develop the ovaries autogenously. The coefficient of correlation between emergence weight and autogenous follicles/female was greater than that between emerging weight and autogenous eggs/female. The coefficients of correlation between emergence weight and autogeny were greater than that between wing length and autogeny. Therefore, autogenous follicles/female is a more accurate parameter to describe autogeny expression level than autogenous eggs/female because oviposition is affected by other factors, and emergence weight is a more important factor determining autogeny expression than wing length.

Animals↗

PubMed1996

Effect of tadpole shrimp, Triops longicaudatus, (Notostraca: Triopsidae), on the efficacy of the microbial control agent Bacillus thuringiensis var. israelensis in experimental microcosms.

Laboratory bioassays using Culex quinquefasciatus larvae evaluated the effect of tadpole shrimp on the persistence of Bacillus thuringiensis var. israelensis (B.t.i.) in water collected from the surface of field microcosms. Time elapsed since B.t.i. treatment, as well as presence or absence of soil and tadpole shrimp, affected B.t.i. persistence at the water surface in 15- and 30-cm total depths. The presence of tadpole shrimp slowed the natural decline in B.t.i. effectiveness over time, but this effect was depressed when soil was present. Tadpole shrimp foraged throughout the water column and stirred up the substrate, keeping more particles in suspension at the surface than in microcosms with no shrimp, in microcosms with water depths of 15 and 30 cm.

Animals↗

PubMed1996

Diel patterns of oviposition and influence of agitated water surface in Chironomus anonymus (Diptera:Chironomidae).

A series of experiments was carried out in a 0.5-ha lake at Portola Country Club, Palm Desert, CA, to study the oviposition habits of Chironomus anonymus. Egg masses were collected by floatable polypropylene ropes attached to the 1.5-m-long stakes placed in the lake. In the diel experiment, ropes were changed every 2 h to determine the preferred oviposit on periods of C. anonymus. The peak of oviposition was between 1900 and 2100 h. For the interruption of oviposition experiment, ropes were placed in the still and agitated portions of the lake for 24 h. A significantly higher number of egg masses, according to applied t-test, was collected from the ropes placed in the still portion of the lake.

Animals↗

PubMed1996

Cross-resistance to Bacillus sphaericus strains in Culex quinquefasciatus.

Laboratory and field-collected strains of Culex quinquefasciatus that were selected with Bacillus sphaericus strain 2362 in the laboratory for about 100 generations and attained 37- and 31-fold resistance, respectively, did not show marked cross-resistance to Bacillus thuringiensis spp. israelensis; only 2-3-fold tolerance was noted. However, they showed significant levels of cross-resistance to strains 1593 (6-22-fold) and 2297 (4-12-fold) of B. sphaericus. Possible mechanisms and management implications are discussed.

Animals↗

PubMed1996

Optimal conditions for rearing the tadpole shrimp, Triops longicaudatus (Notostraca:Triopsidae), a biological control agent against mosquitoes.

Tadpole shrimp (TPS) were reared at 15, 20, 25, and 30 degrees C in the laboratory. Size of TPS was temperature and age dependent with more rapid development at warmer temperatures. Survivorship was inversely related to rearing temperature. Mean age at death was 24.2, 19.2, 14.3, and 11.8 days at 15, 20, 25, and 30 degrees C, respectively. Rearing temperature (excluding 15 degrees C) did not affect lifetime fecundity, but larger TPS laid more eggs than smaller ones. Tadpole shrimp began ovipositing earlier at higher temperatures, and at a smaller size than their counterparts in lower temperatures. Mean age at reproductive maturity was 18.8, 13.1, and 10.2 days and mean carapace length was 10.8, 11.0, and 10.3 at 20, 25, and 30 degrees C, respectively. Embryogenesis required a minimum of 3 days for completion. Hatching rates during the first hydration decreased with increasing egg batch number produced by individuals, ranging from a mean of 74% for the first batch to 31% for the 5th batch. Cumulative hatching rates of eggs after 2 hydrations were consistent across temperatures and egg batches (79 +/- 2%).

Animals↗

PubMed1995

Effects of organic enrichment on temporal distribution and abundance of culicine egg rafts.

The effect of organic enrichment of the larval habitat on mosquito oviposition was determined in 2 replicated field experiments. In the first study, Culex stigmatosoma and Culex quinque-fasciatus oviposition (as measured by the number of early instar larvae) reached a maximum peak soon after flooding and then declined to a substantially lower equilibrium level. A group of ponds that later received supplemental organic matter had a significant increase in oviposition soon after the additional organic matter was added. In the second experiment, a similar ovipositional pattern was noted by the sampling of egg rafts along transects and determining larval abundance by the dipping technique. In the second experiment a mixture of Culex stigmatosoma and Culex tarsalis larvae was collected.

Animals↗

PubMed1995

The future of insect growth regulators in vector control.

Insect growth regulators (IGRs) are diverse groups of chemical compounds that are highly active against larvae of mosquitoes and other insects. The IGRs in general have a good margin of safety to most nontarget biota including invertebrates, fish, birds, and other wildlife. They are also relatively safe to man and domestic animals. The IGR compounds do not induce quick mortality in the preimaginal stages treated. Mortality occurs many days later after treatment. This is indeed a desirable feature of a control agent because larvae of mosquitoes and other vectors are an important source of food for fish and wildlife. On account of these advantages of IGRs and the high level of activity against target species, it is likely that IGRs will play an important role in vector control programs in the future.

Animals↗

PubMed1995

Oviposition responses of Culex tarsalis and Culex quinquefasciatus to aged Bermuda grass infusions.

Fermented infusions of organic matter are commonly used as baits in traps for gravid female mosquitoes. However, infusions are dynamic, and their effects on mosquito oviposition as their chemical and microbial constituents change over time are not well documented. Bermuda grass infusion fermented for periods of 0-63 days was stimulatory to gravid Culex quinquefasciatus. In contrast, only 5-25-day-old infusion was stimulatory to Culex tarsalis. Standard-aged infusion (7 days old) was as effective or better than infusion of any other age for Cx. tarsalis, whereas Cx. quinquefasciatus exhibited a distinct preference for 2-4-wk-old infusion. The results are discussed in terms of mosquito species' oviposition site preferences and in terms of mosquito surveillance programs.

Animals↗

PubMed1995

Mode of existence and seasonality of midge larvae (Diptera: Chironomidae) in man-made lakes in the Coachella Valley, southern California.

Over the past 2 decades, numerous man-made ponds and lakes constructed in country clubs and on golf courses in the Coachella Valley have become ideal habitats for various chironomid species. Large numbers of adult midges emerging from these water bodies pose nuisance and economic problems. During 1992 and 1993 we initiated comprehensive studies on the nature and scope of the nuisance midge problem in the valley. We sampled on a biweekly basis 2 lakes supplied with well water, 2 supplied with tertiary effluent water, and one supplied with a mixture of these 2 sources, to determine the midge larval fauna and the mode of existence, seasonal abundance, and population trends of these midges. Climbers, clingers, portable sand tube builders, and tube builders on plants predominated in well-water habitats with submerged vegetation and detritus bottoms. Tube builders and burrowers predominated in the tertiary water, which characteristically had a detritus bottom, devoid of vegetation. Habitats holding a mixture of the 2 water types with sandy bottoms supported midge larvae known to be sprawlers.

Animals↗

PubMed1994

Protein hydrolysates and associated bacterial contaminants as oviposition attractants for the mosquito Culex quinquefasciatus.

Six protein or protein hydrolysate solutions were tested for activity as attractants for ovipositing Culex quinquefasciatus mosquitoes in the laboratory. Four of these solutions (egg albumin, lactalbumin hydrolysate, casein hydrolysate and yeast hydrolysate) were attractive to ovipositing females at varying concentrations, when compared to distilled water controls. Soy hydrolysate was repellent at 1%, but not significantly attractive or repellent at lower concentrations. 'Nulure', a tephritid fly bait containing protein hydrolysate, also had no significant effect on oviposition behaviour. Gravid females mostly oviposited within the first 4 h of the scotophase, regardless of the presence or absence of an oviposition attractant. Lactalbumin hydrolysate 1% solution, with or without 0.1% neomycin antibiotic, was attractive to Cx quinquefasciatus. This effect was reduced by the presence of neomycin which, alone, had no effect on oviposition. Hence both lactalbumin hydrolysate and bacterial contaminants were shown to be attractive to gravid Cx quinquefasciatus.

Animals↗