Reduction In Larval Population Research Articles

Synergistic interaction between Beauveria bassiana- and Bacillus thuringiensis tenebrionis-based biopesticides applied against field populations of Colorado potato beetle larvae

Commercial biopesticides based on the fungal pathogen Beauveria bassiana strain GHA and the bacterial pathogen Bacillus thuringiensis tenebrionis were applied alone and in combination (tank mixed) against larval populations of the Colorado potato beetle, Leptinotarsa decemlineata, in small plots of potatoes over three field seasons. Interactions between the two products were evaluated in terms of pest-control efficacy. B. bassiana (formulated as Mycotrol) was applied at low and medium label rates of 1.25 and 2.5 × 10 13 conidia/ha, and B. thuringienis (formulated as Novodor) was applied at low and high label rates of 40.3 and 120.8 × 10 6 Leptinotarsa units/ha. Two weekly applications of the bacterial pesticide alone provided 50–85% control of beetle larvae within 14 days after the initial application, while applications of the mycopesticide alone produced no greater than 25% control. Maximum control, in nearly all tests, was produced by the combination of the two products. The combined treatments produced a statistically significant 6–35% greater reduction in larval populations than would have been predicted had the two biopesticides acted independently. This low-level synergistic interaction was observed during all field seasons and resulted from combinations at all rates, including, in one of two tests, the low rates of each product. These results indicate that B. thuringiensis and B. bassiana have strong potential for integrated biologically based management of Colorado potato beetle.

Preliminary attempt at biological control of coconut leaf eating caterpillar, Opisina arenosella Walker using two Trichogramma species

A preliminary attempt was made for biological control of coconut leaf eating caterpillar, Opisina arenosella Walker, by releasing two Trichogramma species viz. T. chilonis Ishii and T. embryophagum Hartig @ 1,000 to 4,000 parasitised eggs per palm in Bangalore, India. The mean percent reduction in larval population by 75.6, 60.0, 33.3 and 50.0% in T. chilonis and 88.8%, 175.0, 66.7 and 75.0% in T. embryophagum was recorded in treated palms during 1st, 2nd, 3rd and 4th generation of the pest compared to untreated control. There was non- significant difference between various release rates irrespective of the species, indicating that lower release rate of 1,000 parasitised eggs/palm as adequate. On sentinel egg cards, parasitism was low 2.0 - 5.0%, 0.0 - 2.0% and 0.0% in T. chilonis, and T. embryophagum released palms and untreated control palms, respectively. The field trial gave an indication that Trichogramma could be a potential parasitoid against O. arenosella and it is suggested that the parasitoids could be released and tested on a large scale in endemic areas to authenticate efficacy.

EXPOSING LARVAE OF THE SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE) TO SUBLETHAL DOSES OF BACILLUS THURINGIENSIS SUBSP. KURSTAKI DOES NOT AFFECT SURVIVAL DURING THE PUPAL STAGE

A process-oriented model was recently developed to simulate the efficacy of spray products containing Bacillus thuringiensis Berliner subsp. kurstaki (Bacillaceae) against the spruce budworm, Choristoneura fumiferana Clemens (Cooke and Régnière 1996). The model accurately predicted foliage protection and larval population reduction during validation spray trials (Régnière and Cooke 1998; Cooke and Régnière 1999). The impact of treatment on budworm generation survival was generally well mimicked by the model except for a consistent overestimation of survival at the end of immature development in the treated plots. Régnière and Cooke (1998) speculated that residual mortality due to treatment may be occurring during the pupal stage. Carry-over of B. thuringiensis from larvae to pupae has been documented for spruce budworm (Klein and Lewis 1966) and several other Lepidoptera (Legner and Oatman 1962; Angus 1965). Although we recently investigated the response of spruce budworm larvae to ingestion of sublethal doses of B. thuringiensis (Pedersen et al. 1997), effects on pupal survival or adult emergence were not examined. In this note, we report the results of an experiment designed to assess such effects.

Larval Survival and Movement of Bluegrass Webworm in Mixed Stands of Endophytic Perennial Ryegrass and Kentucky Bluegrass

Studies examined bluegrass webworm, Parapediasia teterrella (Zincken), larval pop- ulation density and movement in relation to the proportion of perennial ryegrass, Lolium perenne L., plants infected with the fungal endophyte Neotyphodium lolii Glenn, Bacon, Price & Hanlon (PR1), in mixed stands with Kentucky bluegrass, Poa pratensis L.) (KB), and the impact of endophyte infection on feeding preference, growth, and survival of P. teterrella larvae was evaluated. Inchoicetests, P.teterrella larvaedidnotdiscriminatebetweenKBandPR2,butbothwerepreferred over PR1. Larval survival and pupal mass did not differ between KB and PR2, but were significantly reduced on PR1. There was a negative linear relationship between larval population density and the proportion of PR1 in mixed stands with KB until that proportion reached 0.40, after which further reductions in larval populations were not significant. The percentage of larvae surviving in pots after 30 d was independent of initial larval density. Larval movement, as measured by emigration from pots in the greenhouse, increased as the proportion of PR1 increased but was never .50% of the larval population. Through increasing larval movement and mortality, mixed turfgrass stands containing as little as 40% PR1 should prove useful as a pest management tool for P. teterrella.

EFFICACY OF AERIAL APPLICATIONS OF BACILLUS THURINGIENSIS BERLINER AND TEBUFENOZIDE AGAINST THE EASTERN HEMLOCK LOOPER (LEPIDOPTERA: GEOMETRIDAE)

AbstractThe formulated product of the insect-molting hormone analog, tebufenozide (MIMIC 240LV), and two aqueous formulations of Bacillus thuringiensis subsp. kurstaki, ABG6387 and ABG6414, were aerially applied over prethinned commercial stands of balsam fir infested with the eastern hemlock looper. MIMIC® was applied once at the rate of 65.1 g active ingredient (ai) in 1.86 L/ha and twice at the rate of 33.4–35.4 g ai in 1.91–2.02 L/ha. The formulations of B. thuringiensis were applied twice at rates of 19.3–24.1 billion International Units (BIU) in 1.54–1.93 L/ha for ABG6387 and 33.2–36.0 BIU in 1.67–1.80 L/ha for ABG6414.Nine of the 10 plots treated with the single application of MIMIC showed reductions resulting from treatment, ranging from 3 to 93% within 9–11 days and 8 to 100% after 3 weeks. Plots treated twice with the lower dosage of MIMIC generally had larval population reductions of over 50% within 9–11 days of treatment and over 60% 3 weeks after treatment. For both treatments with MIMIC, plots with poor efficacy were clearly associated with low foliar deposition of the active ingredient. Overall, the results suggest that deposits of tebufenozide of less than 1.5 μg/g foliage do not give acceptable control of hemlock looper. Pupal population reductions resulting from treatment ranged from 8 to 99% for plots treated with the single application and 76 to 100% for plots treated twice at the half-dosage. Ground assessments of defoliation occurring after treatment ranged from 10 to 51% (year-old foliage) and 0 to 16% (current-year foliage) for the plots treated once, and 1 to 33% (year-old foliage) and 0 to 8% (current-year foliage) for the plots treated twice at the half-dosage. Thirty-five to 65% of year-old foliage and 15–39% of current-year foliage was defoliated in untreated check plots.Reductions resulting from treatment by ABG6387 ranged from 27 to 91% 10 days after the first application, from 73 to 99% 8 days after the second application, and from 90 to 100% for pupae. Plots treated with ABG6414 had larval population reductions from 76 to 93% 10 days after the first application and from 98 to 100% 7 days after the second application. No pupae were recovered in the plots treated with ABG6414. Defoliation assessed from ground level was less than 5% in the plots treated with ABG6387 and ABG6414 compared with defoliation of 10–29% of year-old foliage and 8–12% defoliation of current-year foliage in the check plots.

Limitations of Trichogramma nubilale (Hymenoptera: Trichogrammatidae) as an Inundative Biological Control of Ostrinia nubilalis (Lepidoptera: Crambidae)

Previous work indicated that Trichogramma nubilale Ertle & Davis could potentially be used as an inundative biological control of Ostrinia nubilalis in sweet corn, Zea mays L., in Minnesota. We expand on these observations to evaluate some of the factors that might limit the utility of T. nubilale in sweet corn and report on releases in green snap bean, Phaseolus vulgaris L. We conducted 3 releases in sweet corn and 2 releases in beans at LeSueur, MN, from 1990 to 1992. Between 11.8 and 60.0 females per square meter of plant surface were released. Two-day egg parasitism varied between 2 and 60% in corn and 15 and 60% in beans. A meta-analysis of these results and several published experimental releases indicated that the major limitation in using T. nubilale is high variability in the relation between release rates and egg mass parasitism rates. This analysis also indicated that the relation between egg mass parasitism and larval population reduction was very strong, and that there was no evidence of density-dependent larval mortality. Thus, future work should focus on elucidating the factors causing variability in parasitism rates to improve the reliability of T. nubilale.

Persistence and Efficacy of Four Nuclear Polyhedrosis Viruses for Corn Earworm (Lepidoptera: Noctuidae) on Heading Grain Sorghum

The persistence and efficacy of Helicoverpa zea nuclear polyhedrosis virus (HzNPV) on heading grain sorghum was compared with three multiply-enveloped NPV's from other hosts to which the corn earworm, Helicoverpa zea (Boddie), is susceptible. Bioassay of NPV by feeding florets from sprayed heads to second instar corn earworm showed only low levels of virus remaining on heads in all of the treatments four days after application. The initial activity and persistence of a commercial preparation of H. zea NPV were greater than four unformulated virus preparations including unformulated HzNPV at rates of 3, 6, and 15 × 1011 polyhedral inclusion bodies (PIB) per ml (P < 0.05). Initial activity and persistence were similar for unformulated preparations of HzNPV, Heliothis armigera (HaNPV), and Autographa californica (AcNPV). Activity and persistence of Anticarsia gemmatalis (AgNPV) were significantly less than for the other viruses (P < 0.05). In a small plot test on heading grain sorghum in which viruses were applied at 1.5, 3, and 6 × 1011 PIB/ha, mortality of collected corn earworm larvae and larval population reduction were greater in the HzNPV treatments than in the three multiply-enveloped virus treatments. HaNPV and AcNPV preparations were more effective than AgNPV. All virus preparations required one wk or longer to significantly reduce larval populations at all rates (P < 0.05).

EFFICACY OF OIL-BASED FORMULATIONS OF BACILLUS THURINGIENSIS BERLINER VAR. KURSTAKI AGAINST THE HEMLOCK LOOPER, LAMBDINA FISCELLARIA FISCELLARIA (GUEN.) (LEPIDOPTERA: GEOMETRIDAE)

AbstractOil-based formulations of Bacillus thuringiensis Berliner var. kurstaki, Dipel 132, Dipel 176, and Dipel 264, were aerially applied at rates of 1.18–2.36 L/ha over five 30-ha plots in a balsam fir, Abies balsamea (L.) Mill., forest in efficacy tests against the eastern hemlock looper, Lambdina fiscellaria fiscellaria (Guen.), in Newfoundland. Double applications of 30 Billion International Units (BIU) per hectare of each formulation and single applications of 40 BIU per hectare of Dipel 176 and Dipel 264 were tested. Larval population reductions of more than 95% and no defoliation of old or new foliage were observed in the plots receiving double applications and in the plot treated with a single application of Dipel 264. Larval numbers were reduced by 85% and defoliation was 4% in the plot treated once with Dipel 176.These treatments were applied against low to moderate larval populations, and their success was attributed to excellent spray coverage and early application when 50% or more of the larvae were still in their first instar.

Field Efficacy of the NRD-12 Strain of Bacillus thuringiensis Against Gypsy Moth (Lepidoptera: Lymantriidae)

Single and double aerial application treatments at 30 billion international units (BIU)/ha of an aqueous formulation (SAN 415 SC 32LV) of the NRD-12 strain of Bacillus Thuringiensis Berliner were evaluated against a moderately dense population of gypsy moth, Lymantria dispar L. Egg mass densities before spray averaged 5,055 egg masses per ha; egg mass density after spray increased to over 19,500 egg masses per ha in the control woodlots but decreased to 2,600 and 4,500 egg masses per ha in the single and double application treatments, respectively. These values were significantly less than the controls but not significantly different from each other. These decreases in egg mass densities represented population reduction estimates of 87% and 77%, which were correlated with the larval population reductions estimated by relative larval densities (83% and 79%) and with the estimated initial larval densities (85% and 72%) of the populations before (1986) and after treatments (1987) with NRD-12. No significant defoliation occurred in the woodlots treated with NRD-12, but control woodlots suffered a significant (33%) defoliation. Larval development in the treated woodlots was delayed significantly compared with the controls. This resulted in an observed but not statistically significant increase in the parasitization rate by Cotesia melanoscelus (Ratzeburg). Fecundity (number of eggs per mass) of the surviving females in the treated woodlots was not adversely affected, nor was the percentage of hatch of their progeny different from that of the previous generation.

Experimental aerial application of Matacil flowable insecticide to control spruce budworm (Lepidoptera: Tortricidae)

Matacil® (aminocarb)_180F flowable insecticide mixed in both water and insectide diluent ID585 and Matacil 1 · 8D oil-soluble concentrate (OSC) mixed in ID585 were sprayed aerially at 70 g a.i./1 · 51 of spray mix/ha in two applications to control spruce budworm, Choristoneura fumiferana (Clem.). The spray droplet density on Kromekote cards, the spray volume recovered on glass slides, larval population reductions and host tree defoliation were compared. The data indicate that Matacil 180F was as effective in controlling budworm populations and protecting the foliage of host trees as Matacil 1 · 8D and that the aqueous mix was as efficacious as the ID585 mix.

Reduction in Fruit-Fly (Tephritidae, Dacinae) Populations in Their Endemic Rain-Forest Habitat by Frugivorous Vertebrates

The reduction in larval populations of Dacus cacuminatus (Hering) and D. halfordiae (Tryon) by frugivorous vertebrates feeding on their major host fruits was studied in an endemic rainforest habitat in south-east Queensland. Throughout the spring and summer season, 66% of Solanum mauritianum Scop. fruit (D. cacuminatus host) was eaten by Macropygia phasianella (Temminck), the brown pigeon; this increased to 77% during the fruit fly's breeding season (November-January). The peak feeding time of the birds, the breeding season of the flies, and the peak fruiting season of the plants all coincided. Parasitism of D. cacuminatus by Hymenoptera, Biosteres kraussi (Fullaway) and B. oophilus (Fullaway), never exceeded 16-17%. Rodents consumed larvae in 78% of fallen fruit of Planchonella australis (R. Br.) Pierre (D. halfordiae host). It is proposed that frugivorous predators are the major natural enemies of larvae of tropical Tephritidae in their endemic habitat.

Efficacy of the Neodiprion sertifer (Hymenoptera: Diprionidae) Nucleopolyhedrosis Virus (Baculovirus) Product, Neochek-S

Neodiprion sertifer (Geoffroy) larval populations were treated with high and low doses of a nucleopolyhedrosis virus (NPV) product, Neochek-S. Larval population reduction due to Neochek-S was well over 90% in all sprayed plots 28 days after application, whereas overall protection of Pinus resinosa (Ait.) foliage was 94.0 � 1.6%. The difference between doses was insignificant with respect to population reduction or foliage protection. A dose rate of 2.5 x 109 polyhedral inclusion bodies of N. sertifer NPV/ha, by ground application, provided acceptable control in a plantation infested with moderate to dense populations of the insect.

Evaluation of Larvadex, a new IGR for the control of pestiferous flies on poultry ranches.

The triazine-type insect growth regulator Larvadex, or CGA-72662 ( N -cyclopropy]-1,3,5-triazine-2,4,6-triamine), was evaluated against domestic flies breeding in poultry manure. A 5% soluble concentrate formulation was diluted with water and sprayed onto manure surfaces, at rates of 0.4 and 0.8 g of AI per m2. The lowe dosage yielded excellent control of Musca domestica (L.) larvae for a period of 4 weeks. It significantly inhibited emergence of adult flies from pupae resulting from larvae in treated plots for 9 weeks. Control of larvae of Fannia femoralis (Stein) found at low population densities was obtained for a period of 6 weeks, and the inhibition of adult emergence was suppressed significantly for about 5 weeks. When populations of Fannia were heavy, significant reduction in larval populations in the treated plots lasted for about 33 days, whereas significant inhibition of emergence was noted for only 13 days. This suggests that the efficacy of this material is possibly short lived when heavy density of F. femoralis exists. At the higher rate (0.8 g/m2) applied twice, larvae of muscoid flies other than Fannia , and consisting primarily of M. domestica , were controlled for about 9 weeks, whereas inhibition of adult emergence was significantly reduced for 69 days after the second treatment. F. femoralis larvae were suppressed for about 4 weeks, whereas inhibition of emergence continued for about 9 weeks. Larvadex provides control of larvae, but also shows delayed activity during transformation from larvae to pupae and pupae to adult. This IGR offers a practical option for the control of manure-breeding flies in poultry operations.

Effectiveness of Selected Insecticides and Insecticide Combinations Against the Bollworm, Tobacco Budworm, and Beet Armyworm on Cotton12

Field tests were conducted to evaluate the performance of selected insecticide treatments against the beet armyworm, Spodoptera exigua (Hubner), and the bollworm complex, Heliothis zea (Boddie) and H. virescens (F.), on cotton. Fenvalarate, profenofos, sulprofos, acephate, and methomyl were effective against S. exigua ; toxaphene plus methyl parathion was ineffective. Treatments and rates (kg AI/ha) producing a significant yield increase over the treated standard, toxaphene + methyl parathion (2.24-4.48+ 1.12-2.24), were profenofos (0.84), fenvalarate (0.11), and permethrin (0.22). A highly significant correlation existed between degree of Heliothis spp. control and yield, but no correlation existed between beet armyworm control and yield. The following treatments and rates (kg AI/ha) provided significant Heliothis spp. control (larval population reduction) compared to the treated standard: fenvalarate (0.11 and 0.22), permethrin (0.22), fenvalarate + amitraz (0.06+0.21), fenvalarate + methomyl (0.06+0.25), sulprofos + amitraz (0.84+0.28), American Cyanamid AC 222705 (0.06−0.11), Dow Dowco 417 (0.11), and Ciba-Geigy CGA 74055 (0.11).

Field Evaluations of Acephate and Dimilin™ Against the Douglas-fir Tussock Moth12

Efficacy of acephate at 1.0 and 0.5 lb AI/2 gal/acre against Orgyia pseudotsugata (McDunnough) was compared to DDT at 0.75 lb AI/gal/acre on replicated 20 acre plots in 1974. Acephate at 1.0 lb AI/gal/acre and Dimilin™{ [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl) urea] at 0.25 lb AI/gal/acre were evaluated on replicated 150-acre plots in 1975. In both experiments, all treatments caused significant reductions in larval populations. In 1974, the 1.0 lb acephate treatment resulted in populapation reductions which were comparable to the DDT treatment; however, the larval knockdown was faster for DDT. Both acephate and Dimilin provided excellent population control and foliage protection in 1975.

Control of Archips semiferanus on Quercus, spp. with Two Chemical Insecticides12

Trichlorfon (Dylox®, 1.5-oi]) when applied at 1.12 kg AI/ha caused significant reductions in larval populations of an oak leaf roller Archips semiferanus (Walker) on Quercus spp. Results indicate that trichlorfon is as effective in reducing populations as the presently registered material carbaryl (Sevin®, 4.oil), when applied at the same rate. Larval reductions with both chemical treatments were very rapid with greater than 95% of the total knockdown occurring within 4 days of application. Sampling of live larvae indicated similar reductions in populations over this period.

Spring Applications of Insecticides for Control of Alfalfa Weevil in Alabama

Of 37 insecticidal spray formulations tested for effectiveness against the alfalfa weevil, Hypera postica (Gyllenhal), a satisfactory reduction in larval population resulted from application of the following insecticides (rates in pounds per acre in parentheses): malathion (1), methoxychlor (2), endrin (0.5), heptachlor (0.5), dieldrin (0.5), benzene hexachloride (0.5), Bayer 39007 ( o -isopropoxyphenyl methylcarbamate) (2), or AC-43064 (cyclic ethylene(diethoxyphosphinothioyl) dithioimidocarbonate) (2). Eight dust formulations were tested and a satisfactory reduction in larval population resulted from the application of either heptachlor (0.5) or parathion (0.4).

The ecology of immature phases of trichostrongyle nematodes

Observations on the larvae of sheep trichostrongyles on hill pastures showed:1. A reduction in larval populations occurred when the ‘moving-flock’ type management was used. The large proportion of eggs passed in faeces is deposited on a part of the pasture where little or no grazing occurs.2. Local concentrations of larvae occurred on the grazed portions of a pasture when grazing was uneven. Thus, the apparent low rate of stocking on hill pastures does not give a true picture of the potential dangers of parasitic disease. Estimates of pasture contamination by Taylor's method of sampling were deceptively low.3. The number of larvae on grass blades was lowest when the grass was wet with dew. Sampling of pastures between 12 noon and 5 p.m g.m.t. gave maximal and most constant estimates.4. There was an increase in the number of larvae on a pasture during the warmer months of the year. While low temperatures prevent or delay hatching, the increase in population was not entirely due to the increased rate of development when temperature was high. The increase in numbers was partly due to an increase in the number of adult worms in the sheep hosts.5. Removal of sheep for 3 weeks reduced the number of larvae on a pasture. This reduction was not apparent, however, until after the first 12 days. After 3 weeks the pasture population was reduced by 55 %, while after 4 weeks (i.e. 7 days after the return of the sheep) the reduction was 90%. Two weeks later there was a small increase in the larval population, but this was again reduced with the onset of colder conditions.

The Control of the Carrot Fly (Psila rosae, Fab.) (Diptera) with DDT.

(1) The proprietary emulsion “Guesapon ”, containing 5 per cent. DDT, gave an unsatisfactory control of carrot fly damage on a plot scale.(2) Treatment of the carrot foliage with this emulsion was more effective than treatment of the soil.(3) A I per cent. emulsion of DDT applied to carrot foliage in the field gave 100 per cent. mortality of carrot flies in the laboratory for 26 days after treatment and showed marked toxicity after a further 38 days.(4) The DDT spray deposits were very, resistant to treatment with water and remained active after death of the foliage. They were also very toxic and lasting on potato foliage.(5) Deposits given by ½ per cent. and I per cent. DDT emulsion were similar in toxicity and persistence. The ½ per cent. is, however, slower in action.(6) From a treated surface the carrot fly is able to acquire a lethal dose of DDT in a very short time, probably by absorption through the feet.(7) Emulsions containing ½ per cent. and I per cent. DDT applied to carrot foliage under cages in the field both gave 95 per cent. kill of carrot flies for a month after application. The treatments also gave a high kill of other insects.(8) Soil samples showed that the larval population and the damage was much lower in the treated than in untreated cages.(9) In a field trial 2⅓ acres of carrots were treated with ½ per cent. DDT emulsion at about 50 gals. an acre.(10) Sweeping showed a rapid decline in abundance of flies after treatment and high mortalities were observed. These features did not occur on neighbouring untreated carrots.(11) These effects lasted for some 21 days after treatment and a marked reduction of larval population and damage resulted.