Small-plot Field Trials Research Articles

Reaction of wheat varieties to infection with barley yellow dwarf virus and prospects for resistance breeding

The reaction of winter and spring wheat to infection with barley yellow dwarf virus (BYDV-PAV) was evaluated in three-year small-plot field trials on 71 wheat varieties registered in the Czech Republic and at two locations for two years on 63 selected potential sources of resistance. Disease symptoms (VSS) were visually recorded using a 0–9 scale and the percent reduction of grain weight per spike (GWS-R) was measured on twenty plants per plot. The evaluation showed that among the registered varieties of winter and spring wheat no variety had a high resistance to BYDV (with VSS lower than 3.5). GWS-R ranged between 24% and 60%. Higher variability in VSS was detected for the registered varieties of spring wheat compared to winter wheat. Among the registered varieties of winter wheat, Saskia, Rialto, Meritto, Rexia, and Svitava, as well as the spring wheat Leguan, received the best long-term evaluations. The highest level of resistance was detected for the PSR 3628 line (a hybrid of wheat and couch-grass), but in connection with a low agronomic value. The WKL91-138 line of spring wheat and some varieties (lines) with the detected moderate level of resistance, in particular, could offer good prospects for use in breeding. The presence of the Bdv2 gene was expressed only in the reduction of virus content on the 11<sup>th</sup> day after inoculation. Nevertheless, genotypes carrying this gene were evaluated in field trials as susceptible or very susceptible to infection with the Czech PAV isolate. Similarly, the presence of the Bdv1 gene detected with the help of WMS130 marker was no assurance of an increased level of resistance to BYDV. Hybridological analyses of crosses with the WKL91-138 line showed a polygenic nature of inheritance. Thus, the marker-assisted selection does not obviously promise success without a focus on detecting a larger number of QTLs.

Paraffin Wax Emulsion for Increased Rainfastness of Insecticidal Bait to Control <I>Rhagoletis pomonella</I> (Diptera: Tephritidae)

In regions with a humid summer climate, the use of water-soluble bait to control apple maggot is often limited by rainfall. We studied increasing the rainfastness of GF-120 fruit fly bait by adding paraffin wax emulsion. First, we verified that adding 10% wax to a mixture containing 16.7% GF-120 did not reduce the mortality of female apple maggot compared with GF-120 without wax. In addition, we determined that fly mortality caused by GF-120 plus wax subjected to simulated rain was similar to that caused by GF-120 without wax not subjected to rain. Other assays showed that higher fly mortality resulted from increasing the proportion of wax from 10 to 15%, and lower mortality resulted from decreasing GF-120 from 16.7 to 10 or 5%. The availability of spinosad on or near droplets of a mixture consisting of 5, 10, or 15% GF-120 and 15% wax was determined before and after the droplets were subjected to three 15-min periods of simulated rain. We found an initial steep decline in dislodgeable spinosad and smaller decreases after subsequent periods of rain. In a small-plot field trial, fruit infestation by apple maggot in plots treated with a mixture consisting of 16.7% GF-120 and 19.2% wax was less than in plots treated with 16.7% GF-120 without wax but not less than in control plots. Overall, we found that adding paraffin wax emulsion to GF-120 increased rainfastness in laboratory bioassays, and specifically that it retained the active ingredient spinosad. However, our field data suggest that optimal rainfastness requires the development of mixtures with > 19.2% wax, which may preclude application using standard spray equipment.

Frequency and Severity of Western Bean Cutworm (Lepidoptera: Noctuidae) Ear Damage in Transgenic Corn Hybrids Expressing Different <I>Bacillus thuringiensis</I> Cry Toxins

The frequency and severity of corn ear damage caused by western bean cutworm, Striacosta albicosta (Smith), were measured on transgenic corn, Zea mays L., hybrids expressing two different insecticidal Bacillus thuringiensis (Bt) (Berliner) Cry toxins (Bt) selected to protect against damage caused by larval European corn borer, Ostrinia nubilalis (Hübner). A field cage experiment deliberately infested with western bean cutworm egg masses resulted in less damage in the hybrid expressing the Cry1F protein and supported fewer western bean cutworm larvae than its non-Bt isoline. Corn hybrids expressing Cry1F, grown in small plot field experiments at three locations over two separate years and exposed to natural western bean cutworm infestations suffered less damage than non-Bt or Bt-hybrids expressing a Cry1Ab protein. Later maturing hybrids suffered more damage than shorter-season hybrids. Finally, corn ears observed in strip trials for several years in diverse agronomic conditions in farmer-cooperator fields corroborated the in-plant protection conferred by corn hybrids expressing the Cry1F protein in small plot field trials.

Control of Arbovirus Vector <I>Verrallina funerea</I> (Diptera: Culicidae) in Southeast Queensland, Australia

In Australia, the brackish water mosquito Verrallina funerea (Theobald) (Diptera: Culicidae) is a serious pest and vector of Ross River and Barmah Forest viruses in coastal areas in the northeast of the continent. We report on the first extensive evaluation of the efficacy of various pesticides against this species, including laboratory dose-response assays and small plot field trials. In the laboratory, Ve. funerea was susceptible to temephos (Abate 100E) (lethal concentration, 95% endpoint [LC95] of 1.651 ppb), Bacillus thuringiensis subsp. israelensis de Barjac (Bti) (VectoBac 12AS) (LC95 of 0.033 ppm), s-methoprene (ProLink Liquid Larvicide [PLL]) (emergence inhibition, 95% endpoint [EI95] of 2.647 ppb), and technical grade pyriproxyfen (EI95 of 0.227 ppb). In contrast, Ve.funerea was highly refractory to Bacillus sphaericus Neide (VectoLex WG) (LC95 of >855.3 ppm). The survival of adults exposed as larvae to sublethal doses of s-methoprene was reduced for those doses greater than the EI50, although sex ratios were unaffected. Field trials demonstrated that Ve. funerea was susceptible to Bti (VectoBac G at 7 kg/ha) and s-methoprene (ProLink ProSand at 4 kg/ha), with these products giving >99 and >98% control, respectively. We also observed a significant increase in immature mortality in s-methoprene-treated pools, suggesting that s-methoprene field trials based solely on emergence inhibition of pupae may underestimate the efficacy of this insecticide.

Surface Seals Reduce 1,3‐Dichloropropene and Chloropicrin Emissions in Field Tests

Reducing emissions is essential for minimizing the impact of soil fumigation on the environment. Water application to the soil surface (or water seal) has been demonstrated to reduce 1,3-dichloropropene (1,3-D) emissions in soil column tests. This study determined the effectiveness of water application to reduce emissions of 1,3-D and chloropicrin (CP) in comparison to other surface seals under field conditions. In a small-plot field trial on a Hanford sandy loam soil (coarse-loamy, mixed, superactive, nonacid, thermic Typic Xerorthents) in the San Joaquin Valley, CA. Telone C35 (61% 1,3-D and 35% CP) was shank-applied at a depth of 46 cm at a rate of 610 kg ha-1. Soil surface seal treatments included control (no tarp and no water application), standard high density polyethylene (HDPE) tarp over dry and pre-irrigated soil, virtually impermeable film (VIF) tarp, initial water application by sprinklers immediately following fumigation, and intermittent water applications after fumigation. The atmospheric emissions and gas-phase distribution of fumigants in soil profile were monitored for 9 d. Among the surface seals, VIF and HDPE tarp over dry soil resulted in the lowest and the highest total emission losses, respectively. Intermittent water applications reduced 1,3-D and CP emissions significantly more than HDPE tarp alone. The initial water application also reduced emission peak and delayed emission time. Pre-irrigated soil plus HDPE tarp reduced fumigant emissions similarly as the intermittent water applications and also yielded the highest surface soil temperature, which may improve overall soil pest control.

Alternative Agents for Control of European Corn Borer and Corn Flea Beetle on Sweet Corn

ABSTRACT Small plot field trials were conducted in 2002 and 2003 to compare European corn borer (ECB) (Ostrinia nubilalisHübner) control using currently recommended insecticides, carbofuran (FURADAN® 480F) and lambda-cyhalothrin (MATADOR® 120EC), with spinosad (SUCCESS® 480SC) and Bt-sweet corn (ATTRIBUTE®). In both years, foliar applications of spinosad, lambda-cyhalothrin or carbofuran, or Bt-sweet corn significantly reduced the number of ECB stalk tunnels, percent damaged plants and number of damaged kernels, tunnels and larvae on ears at harvest compared to the untreated control. More marketable ears were harvested from plots treated with the insecticides and Bt-sweet corn treatments than from untreated controls. Small plot field trials also were conducted to investigate the efficacy against corn flea beetle (CFB) (Chaetocnema pulicaria Melsheimer) of the seed treatment insecticides, imidacloprid (GAUCHO® 480FS) and clothianidin (PONCHO® 600F). Imidacloprid was evaluated in both 2002 and 2003, clothianidin in 2003 only. Seed treatment with either insecticide significantly reduced numbers of CFB feeding damage marks compared to untreated controls. Clothianidin provided more effective control of CFB than imidacloprid. Overall, the results demonstrated that spinosad or Bt-sweet corn provided ECB control comparable to carbofuran and lambda-cyhalothrin, while imidacloprid or clothianidin seed treatments reduced sweet corn seedling injury from CFB.

The effect of non-toxic endophytes in tall fescue on two major insect pests

In a choice trial in a glasshouse, infection of tall fescue with the endophyte AR542 significantly reduced feeding by adult Argentine stem weevil (ASW) in the cultivar J esup but not in Advance in comparison with the same cultivars without endophyte. Paddocks of Quantum infected with AR542 that were sampled on two Northland farms consistently had fewer tillers damaged by Argentine stem weevil than equivalent paddocks of endophyte-free (Nil) tall fescue. In comparison to Nil plants, AR542 in Jesup and Advance had significantly fewer plants and tillers damaged by adult black beetle in a glasshouse choice trial. Fewer tillers were also damaged by adult black beetle in Advance tall fescue infected with AR501 and AR502 than in Nil Advance in a small plot field trial at Kerikeri. In a similar trial at Ruakura, the occurrence of adult black beetle and signs of larval damage were high in endophyte-free plots and considerably reduced in endophyte-infected plots. It is concluded that the nontoxic endophytes will lessen damage by black beetle and ASW in a range of tall fescue cultivars and that this is likely to contribute to increases in productivity and persistence of this forage grass. Keywords: Argentine stem weevil, black beetle, AR542 endophyte, Neotyphodium, tall fescue

Factors influencing the effectiveness of an attracticide formulation against the Oriental fruit moth, Grapholita molesta

AbstractAn attracticide formulation, LastCall™OFM, was tested against the Oriental fruit moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae) in replicated small plot field trials in apple, Malus domestica (Borkhausen), orchards in South‐eastern Pennsylvania, USA. Attracticide treatments were applied using a calibrated hand pump, and treated plots were compared to similar untreated plots. Male moth activity was monitored using virgin female‐baited traps, and the potential for reduction in mating activity was assessed using sentinel virgin females. A comparison of application rates showed that 1500 droplets per ha of the attracticide formulation was as effective as 3000 droplets per ha, and both application rates reduced captures in synthetic pheromone‐baited traps for prolonged periods. Droplets placed either at high or low positions within the canopy significantly reduced trap capture and mating with sentinel females. In addition, the only sentinel females that mated in the treated plots were located in the untreated portion of the tree canopy. Mate finding behaviour was equally disrupted by formulations with and without insecticide. Therefore, under the test conditions, the mechanism by which the attracticide formulation worked was by disruption of male orientation, and not by the removal of males due to insecticide poisoning. Two field cage experiments tested the impact of population density on the competitiveness of the attracticide formulation compared to virgin females. A significant proportion of males were captured in female‐baited traps at the highest female‐to‐droplet ratio tested. Equal proportions of males were captured in attracticide‐baited traps at male moth densities of 10, 20, 40, and 80 males per cage. These results clarify some of the factors influencing the effectiveness and possible mechanisms of an attracticide management tactic against the Oriental fruit moth.

The effect of a fungicide application on the yield and quality of barley grain and malt

In small-plot field trials conducted in 2000–2002 we studied the effect of fungicides on the yield and selected technological parameters of grain of malt barley and on malt. For the treatment we used Cerelux (active ingredients: fenpropimorph, flusilazole), Amistar (azoxystrobin) and Caramba (metconazole) applied in two stages of stand development (DC 47 and 55). Compared to the untreated control plants the yield grains ranged between 6.9 and 16.5% after the application of fungicides. The application of fungicides increased the proportion of full grains and had a favourable effect on the chemical composition of grain. After the treatment with azoxystrobin the content of N-substances decreased from 11.43 to 11.07% as compared to the controls. The highest starch content of grain was observed after the application of the active ingredient metconazole; the average content ranged between 64.44 and 64.62%. Compared to the controls the highest relative yield of malt starch (124.2–125.2%) was achieved after the application of azoxystrobin or a combination of azoxystrobin and metconazole in the DC 47 stage. The highest average attainable degree of fermentation was 78.57% and was discovered in the untreated control.

Effects of imidacloprid on transmission of tomato spotted wilt tospovirus to pepper, tomato and tobacco by Frankliniella fusca Hinds (Thysanoptera: Thripidae)

Rates of transmission of tomato spotted wilt tospovirus (TSWV) by tobacco thrips, Frankliniella fusca Hinds, to imidacloprid-treated and untreated tomato, pepper and tobacco were measured in greenhouse and small-plot field trials. The incidence of TSWV was reduced in greenhouse assays with all 3 crops receiving a soil application of imidacloprid at a rate of 9.9 g [AI]/1000 plants. Levels of TSWV were also reduced in small-plot field trials of tomato and pepper plants receiving transplant applications of imidacloprid at the same rate. No F. fusca were recovered from imidacloprid-treated tobacco (9.9 g [AI]/1000 plants) 24 days following an initial infestation. In the greenhouse, F. fusca populations reached higher levels on healthy than TSWV-infected tobacco. Applications of soil-applied imidacloprid reduced the number and duration of probing/feeding bouts by F. fusca on pepper and mustard ( Brassica rapa L.). Reduced probing and feeding by viruliferous thrips on imidacloprid-treated plants may contribute to less TSWV incidence as observed in the field and greenhouse experiments.

Using Collembola to assess the risks of applying metal-rich sewage sludge to agricultural land in western Scotland

The recent United Kingdom ban on the disposal of sewage sludge at sea has led to the prediction that land application of sludge will become more widespread. The positive aspect of recycling nutrients may, however, be offset by the risk of contamination by heavy metals that are frequently present in sludge. The environmental impact of applying metal-rich sewage sludge to agricultural land was, therefore, assessed using Collembola. A combination of pitfall trapping and suction sampling was used to monitor epigeal/hemiedaphic Collembola on a small plot field trial in the west of Scotland. Four sludge treatments were investigated: cadmium-rich sludge, zinc-rich sludge, uncontaminated sludge and a no-sludge control. It was found that the abundance of Lepidocyrtus cyaneus Tullberg and Isotoma viridis Bourlet was significantly lower in plots receiving cadmium-rich sludge than those receiving uncontaminated sludge. Isotoma anglicana Lubbock was not influenced by the presence of metals in sludge and Isotomurus palustris (Müller) was actually favoured by the application of metal-rich sludge. Other aspects of collembolan ecology, and the efficiency of the two sampling methods, are also discussed.

Efficacy and environmental fate of alphacypermethrin applied to rice fields for the control of chironomid midge larvae (Diptera: Chironomidae)

Chironomid midge larvae are the most important pests affecting the establishment of aerially sown rice crops in New South Wales (NSW). The pyrethroid insecticide alphacypermethrin was evaluated for the control of chironomid midge larvae in small plot field trials at Yanco Agricultural Institute during the 1997–1998 and 1998–1999 rice seasons. Treatments were applied at sowing (6 days after flooding) in both trials. In the 1997–1998 trial, alphacypermethrin applied as an emulsifiable concentrate formulation at 10, 20, and 30 g active ha −1 provided between 54 and 73% control of target Chironominae in the first 19 days after application (DAA), whilst a chlorpyrifos standard treatment (75 g active ha −1) also provided 73% control. Populations of Chironominae were very low during the 1997–1998 season (estimated control density 14 DAA approximately 485 larvae m −2), and control was not reflected in improved plant establishment. In the 1998–1999 season target Chironominae, predominantly Chironomus tepperi Skuse, were far more abundant (estimated control density 14 DAA approximately 13 100 larvae m −2). Alphacypermethrin provided >99% control of Chironominae for 19 DAA at all rates evaluated (6, 10 and 20 g active ha −1), whilst the chlorpyrifos standard (75 g active ha −1) gave 97% control over the same period. Plant establishment 30 DAA averaged 23 plants m −2 in the control bays, from 169 to 188 plants m −2 in the alphacypermethrin bays, and 204 plants m −2 in the bays containing the chlorpyrifos standard. Differences in plant establishment between the alphacypermethrin and chlorpyrifos treatments were not significant ( P>0.05). Results indicate that alphacypermethrin applied at between 6 and 10 g active ha −1 will be equal or superior to chlorpyrifos (75 g active ha −1) for the control of chironomid larvae during rice crop establishment. Concentrations of alphacypermethrin in the water column and sediment were monitored during each trial. Concentrations in water for the 20 g active ha −1 rate ranged from 0.23 to 0.41 μg l −1 1 DAA down to 0.008 μg l −1 at 18 DAA, whilst at the 6 g active ha −1 rate alphacypermethrin concentrations declined to below the detection limit (0.001 μg l −1) at 18 DAA. Surface sediments (top 2 cm) still contained measurable concentrations of alphacypermethrin at 25 DAA (e.g. 29 μg kg −1 for 20 g active ha −1 rate, 1997–1998 trial). No alphacypermethrin residues were detected in plant samples taken 42 days after treatment, or in grain or forage samples at harvest (1997–1998 trial, detection limit 20 μg kg −1).

Potential of a Dried Rice/Mycelium Formulation of Entomopathogenic Fungi to Suppress Subterranean Pests in Small Fruits

The potential of a dried rice/mycelium formulation of three species of entomopathogenic fungi ( Metarhizium anisopliae, Beauveria bassiana and Paecilomyces farinosus ) was assessed according to five criteria: storage life, field efficacy against two subterranean pests of cranberry, persistence and efficacy against first-instar black vine weevil larvae in potted strawberry and field persistence in a cranberry bog. The number of conidia sporulated from the formulation did not decline between 4 and 20 days. In small plot field trials, the numbers of black vine weevil, Otiorhynchus sulcatus (F.), were significantly lower in plots treated with 1000 gm - 2 of formulated M. anisopliae than in untreated plots. In similar trials, the numbers of adult cranberry girdler, Chrysoteuchia topiaria (Zeller), inside emergence cages were significantly lower on plots treated with the formulated M. anisopliae than on untreated plots. The formulation suppressed first-instar black vine weevil larvae in potted strawberry regardless of the species of entomopathogenic fungus or the post-inoculation interval. M. anisopliae was periodically isolated for up to 637 days from plots in cranberry bogs treated with the formulation. In general, the dried rice/mycelium formulation may be a useful fungal mycopesticide for the management of subterranean pests of small fruits, especially if applied at high rates to areas of serious pest infestation.

Perennial legumes for the high rainfall zone of eastern Australia. 2. Persistence and potential adaptation zones

Cultivars and accessions of a range of perennial legumes were evaluated in small plot field trials at 4 on-farm locations on the Northern Tablelands of New South Wales. Variable establishment from seed resulted in good stands at 2 sites, and moderate to poor stands at the other 2 sites. In spite of this, trends in behaviour of individual species were apparent even where stands were very poor. This was exemplified by the gradual improvement in frequency of Trifolium medium at the most montane site. Trifolium ambiguum and Coronilla varia were most persistent across all sites. Good stands of Lotus corniculatus, L. pedunculatus, T. pratense and Medicago sativa thinned out within several years with M. sativa most persistent. Astragalus cicer thinned out rapidly on the relatively acidic soils but maintained a good stand at 1 site on a deep, free-draining granite. From these results and known climatic responses, simple logical rules were constructed to predict potential legume adaptation zones for eastern Australia. The zones of adaptation for the range of species are compared with a nominal zone for T. repens to identify areas where legume persistence might be improved with additional species.

Field Evaluation of Ovicidal Efficacy of Microencapsulated Profenofos, 1991

Abstract A small-plot field trial was conducted at Texas A&M University Plantation, College Station, TX, to compare the efficacy of microencapsulated profenofos 4 CS with an EC formulation and flowable formulation of thiodicarb against TBW and CBW eggs on cotton. Cotton was planted 3 May in 1.016 m rows, and plant density averaged 114,806 plants per ha. Plants were 91.4 cm tall and contained avg 5 squares per plant when they were treated. Plots of 2, 25 m long rows per treatment were arranged in a completely randomized block design with 3 replications. Treatments were applied with a CO2-compressed gas backpack sprayer calibrated to deliver 157.1 liters/ha through two 8002 VS nozzles per row at 207 kPa. Windspeed was less than 8 km/h. A pretreatment sample of approximately 100 eggs was obtained for determination of species composition. Treatments were applied 5 Jul, eggs were collected 6 (1 DAT) and 8 (3 DAT) Jul, and were reared on artificial diet in a growth chamber maintained at 21.1°C and 80% RH. Eggs were not separated into brown and white color in order to obtain at least 25 eggs per treatment during each collection date.

Field evaluation of barley (Hordeum vulgare L.) genotypes derived from tissue culture

Somaclonal variation has been observed in plants derived via tissue culture in a number of crops, but evaluation has been on a small scale. This study was conducted to evaluate 72 tissue culture-derived barley (Hordeum vulgare L.) genotypes for somaclonal variation in replicated small-plot field trials. Twenty putative somaclones from the cultivar Abee, 20 from Deuce, 15 from Duke and 17 from Heartland were evaluated at three Saskatchewan locations during 1989. Little variation was observed between regenerants and their respective parent cultivars for days to head, height, yield and yield components. When variation did occur it was generally of negative value, i.e., later heading date; lower test weight, 1000-kernel weight, percent plumpness and yield. Of the four groups, those from Deuce and Duke exhibited the most variation. A 5-d difference in heading date was observed for one Duke derivative and 18 of the 20 Deuce derivatives were shorter than the Deuce control. From this study, it was concluded that somaclonal variation would be of no benefit in a plant-breeding program.Key words: Barley, field evaluation, tissue culture, Hordeum vulgare L.

Insecticide Evaluation for Wireworm Control in Sugarcane, 1989

Abstract Insecticides were evaluated for control of wireworms in sugarcane using small plot field trials at the LSU St. Gabriel Experiment Station in Iberville Parish, LA. A randomized complete block design was used with 6 replications, each plot with 3 rows spaced 6 ft apart by 72.6 ft in length (0.03 acre). Applications were made on 28 Sep, 1988 using 1 qt "shaker" jars with holes in the lids. Sugarcane growth and stand counts in each plot were determined on 28 Nov 1988-and 23 Aug 1989. Soil samples were taken and analyzed for nematode infestation levels on 10 Jul 1989. A height measurement (from soil surface to whorl) consisting of 12 random stalks from each plot was made on 21 Jul. SC borer injury was additionally determined on 19 Oct by comparing percent bored internodes in treated and untreated plots following examination of 12 stalks/plot for external signs of SCB entrance and exit holes. The weight of 10 stalks of the 12 evaluated for SCB injury was recorded and evaluations of Brix and polarity made.

Impact of Cropping History and Insecticides on Cutworm and Chinch Bug Infestations in Corn, 1989

Abstract Two small-plot field trials were conducted on a commercial corn field located near Wharton, TX. Trial 1 was conducted on a portion of the field which was planted to corn in 1988, whereas Trial 2 was conducted on a portion of the field which was left fallow and weed-infested in 1988; the 2 trials were separated by only 40 rows of corn. Methods and materials were identical for both studies, except for the addition of Force as a treatment in Trial 1. Insecticides and an untreated check were compared in 2-row by 500-ft plots of corn planted 13 Mar on 38-in rows. Treatments were replicated 4 times in a randomized complete block design. At planting time, each insecticide (except Force) was applied into the open seed furrow. Force was applied in a 6-in band over a partially open seed furrow (i.e., each row-bander was located between the seed-drop and press wheel). Insecticides were applied with a John Deere Max-Emerge planter equipped with Kinze applicator boxes. Texture of soil at the test location was medium, and soil moisture at planting time was excellent. One inch of rain fell at the test location during the first 3 wk after planting time. Insecticide efficacy was evaluated by (1) inspecting 20 randomly chosen plants in each plot for damage caused by cutworms and (2) inspecting 20 randomly chosen plants in each plot for numbers of adult chinch bugs. Plant-stand was estimated for each treatment by counting numbers of plants (cutworm-damaged plus non-damaged plants) per 13.75 row-ft at 2 sites in each plot.

Efficacy of Bacillus sphaericus 2362 against larvae of Anopheles gambiae under laboratory and field conditions in West Africa.

A flowable concentrate of Bacillus sphaericus (Neide) strain 2362 was applied against Anopheles gambiae Giles s.l. mosquito larve in small plot field trials in Bobo-Dioulasso area. Burkina-Faso. Third and fourth instar larvae were controlled for 10-15 days with a dosage of 10 g/m2, 3-10 days with 1 or 0.1 mg/m2, and 2 days with 0.01 g/m2. Complete elimination of larval populations required 1 x 10(2) to 2 x 10(3) viable spores/ml in the larval feeding zone. After treatment, the total numbers of viable spores decreased in the ponds, due to ingestion of spores by non-target as well as target organisms and/or loss of viability of some spores by sunlight. This formulation was less effective against An. gambiae than against Culex quinquefasciatus Say larvae, both in laboratory bioassays and under field conditions.

Efficiency of insecticides for greasy cutworm control

Abstract In small plot field trials for insecticidal control of artificial infestations of greasy cutworm (Agrotis ipsilon Hufnagel) in seedling maize, deltamethrin, permethrin, alphamethrin, fenvalerate, and flucythrinate sprayed at recommended rates, prevented plant damage more effectively than endosulfan, chlorpyrifos, and diazinon. All of the above pyrethroid insecticides adequately controlled cutworm infestations at recommended rates of application. The analysis required a generalisation of logit analysis in which both control survival of plants and the treatment effect depend on design factors.