Forecasting the emergence of the adult orange wheat blossom midge,Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae) in Belgium

Agronomists often underestimate the damage inflicted by the orange wheat blossom midge, Sitodiplosis mosellana (Géhin), a wheat (Triticum aestivum L.) pest. The main risk arises when the emergence of the adult midges coincides with wheat ear emergence. The emergence of adult midges was monitored in Belgium over four years and analysed against climate data, establishing the significance of specific rainfall events as triggers for the final phase of development prior to emergence. This discovery, combined with experience from previous models, was incorporated into a new forecasting model, described in this paper. The new model consists of three separate phases. The first phase comprised a temperature accumulation of 250 degree-days (DD) above 3 °C, starting from 1 January. Once this initial condition is satisfied, the second phase starts, and it lasts until the occurrence of a double signal consisting of a rise in the mean daily temperature up to 13 °C, followed by rainfall. This rainfall event triggers an accumulation phase of 160 DD above 7 °C. Once this last condition is met, the adults emerge.     

Temporal progress and control of tomato spotted wilt virus in flue-cured tobacco

Tomato spotted wilt virus causes tomato spotted wilt (TSW), a disease that results in economic losses on several crops including tobacco in the southeastern United States. The effect of imidacloprid (IMD) applied as a pre-transplant soil drench alone, in combination with acibenzolar-S-methyl (ASM), or followed by a foliar application of ASM immediately after transplanting on TSW incidence and severity on tobacco was quantified in studies conducted in North Carolina from 2006 to 2008. Pre-transplant IMD application in combination with ASM provided the greatest reduction in TSW incidence and severity; however other treatments provided economically efficacious controls when TSW incidence was <30% in a field. From these results, TSW incidence was classified as Low (<10%), Moderate (11-20%), High (21-30%), or Very High (>30%), classes corresponding to different control recommendations, and subsequently used for modeling temporal TSW progress in a field. The temporal progress of TSW was modeled with data collected from 23 tobacco fields in North Carolina from 2006 to 2008. Cumulative degree-days (DD) and the average class of TSW incidence observed in a field for 5 seasons before the one that data were collected were significant variables (P < 0.05) for explaining the temporal progress of TSW incidence. DD based on four temperature thresholds (10.5, 18.0, 20.0, and 26.0 °C) were investigated, resulting in four models. Models were validated with data collected in 2009 and the model in which DD were calculated based on the threshold of 10.5 °C had a higher predictability (R² = 0.70) than the other three models. The 26 °C DD model had the poorest predictability (R² = 0.33). These models are currently being validated in North Carolina and the other flue-cured production states of the southeast United States as a tool for implementing disease control recommendations.     

Efficacy of aluminum phosphide tablets to control Richardson’s ground squirrel (Spermophilus richardsonii) populations in southern Saskatchewan, Canada

The objective of this study was to assess, using a capture-recapture program, the effectiveness of aluminum phosphide tablets for control of Richardson’s ground squirrels (Spermophilus richardsonii) in southern Saskatchewan grasslands, from April to July 2007-2009. Aluminum phosphide tablets were tested in study plots in moist or dry soil conditions, where burrow openings had either been marked with a flag (to ensure that all openings would be found and treated) before treatment or left unmarked. In five study plots with moist soil conditions and flagged burrow openings, the mean control level was 80.9 (SD = 6.3) %. In two study plots with dry soil conditions and flagged burrow openings, and one study with moist soil conditions and unflagged burrow openings, control levels were < 60%. It is recommended that aluminum phosphide tablets be used to control Richardson’s ground squirrels in relatively small areas (i.e., < 5 ha) with moist soil conditions and flagged burrow openings, or in specific sites where there are still high concentrations of ground squirrels after an initial treatment with poison food baits.     

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat (Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.     

Development of a formulation of Trichoderma asperellum to control black rot disease on pineapple caused by (Thielaviopsis paradoxa)

A local isolate of Trichoderma asperellum was tested for its antagonistic activity against Thielaviopsis paradoxa (telemorph = Ceratocyctis paradoxa). The highest antagonistic activity was achieved when the concentration of T. asperellum conidia was 1 × 10⁷ conidia/mL. The highest biomass and number of colony forming unit/mL of the T. asperellum peaked at 144 h after incubation in yeast waste residue medium. The minimum inhibition concentration value of the formulation was observed as 1% on growth of Th. paradoxa incubated at 28 ± 2 °C for 10 d. In the soil fungicide-screening test, the effect of concentrations 100-1600 μg/mL on mycelia growth was not significant (P < 0.05). Complete mycelial growth inhibition occurred at concentration above 52,600 μg/mL. Results of the fruit application tests clearly showed that all treated fruits were free of disease at the end of the incubation period. No significant differences (P > 0.05) in pH, total soluble solids and titratable acidity were observed between fruits treated with formulation of T. asperellum and the control formulation treated pineapples.     

Pheromone-mediated mating disruption in the millet stem borer, Coniesta ignefusalis (Lepidoptera: Pyralidae)

The millet stem borer, Coniesta ignefusalis Hampson (Lepidoptera: Pyralidae), is a major pest of pearl millet in the Sahelian region of Africa. The female sex pheromone has been identified and synthesised, and previous research had shown that the synthetic pheromone could cause high levels of reproductive communication disruption in small plots when released at rates of 640 mg/ha/day, using PVC resin formulation renewed every seven days to maintain efficiency. In the present research, in experiments in farmers’ fields in Niger, 86.8% (SE = 2.6%) communication disruption was achieved when polyethylene vials loaded with 0.5 mg pheromone at 400 dispensers/ha were used and replaced every 21 days. Polyethylene vials loaded with 80 mg pheromone gave uniform, zero-order release at approximately 0.05 mg/day at 27 °C. Experiments carried out on replicated 0.5 ha plots in farmers’ fields in Niger using a single application of these dispensers at 400 dispensers/ha resulted in at least 99% suppression of pheromone trap catches of male C. ignefusalis moths in treated plots relative to numbers in untreated plots for up to 3 months. However, sampling the central portions of these plots before and after harvest showed no significant differences in infestation, damage or yield loss between plots treated with pheromone and untreated plots. This may have been because of small plot size and the immigration of mated female moths into the treated plots which negated any reduction of mating of females within the treated plots. Comparisons of numbers of male C. ignefusalis moths in traps baited with the standard 0.5 mg monitoring lures and those baited with the 80 mg disruption dispensers showed catches in the latter were only 10-20% of those in the former; indicating high level communication disruptions in traps with high dose dispensers. Implications of using insect synthetic pheromones in the development of integrated management of C. ignefusalis in pearl millet cropping systems in the Sahel are discussed.     

Quantification of the cardinal temperatures and thermal time requirement of opium poppy (Papaver somniferum L.) seeds to germinate using non-linear regression models

The response of plant development rate (including germination rate) to temperature might be described as a non-linear function. We compared 3 non-linear regression models (Dent-like, segmented and beta) to describe the germination rate-temperature relationships of opium poppy (Papaver somniferum L.) over 6 constant temperatures to find cardinal temperatures and thermal time required to reach different germination percentiles. Two replicated experiments were performed with the same temperatures. An iterative optimization method was used to calibrate the models and different statistical indices (mean absolute error, coefficient of determination (R²), intercept and slope of the regression equation of predicted vs. observed germination rate) were applied to compare their performance. The segmented was found to be the best model to predict germination rate (R² = 0.92, MAE = 0.0011 and CV of 1.4-3.6%). Estimated cardinal temperatures were similar for different germination percentiles (P < 0.05). Base on the model outputs, the base, the optimum and the maximum temperatures for germination were estimated as 3.02, 27.36 and 36.31 °C. The thermal time required to reach 50 and 95% germination was 57.27 and 87.55 degree-days, respectively. Model predictions of the time required for seed germination agreed reasonably well with the observed times (MAE = 0.56 day, R² = 0.887). All model parameters may be readily used in crop simulation models.     

Rheological and textural properties of tef [Eragrostis tef (Zucc.) Trotter] grain flour gels

Interest in tef [Eragrostis tef (Zucc.)Trotter] grain in food applications has increased in recent years because of its nutritional merits and the absence of gluten. With the objective of evaluating the suitability of tef for making gel type food products, gel viscoelastic properties of three varieties of tef (one brown and two white) at different concentrations (6, 8, 10, 12 & 14% w/w) were evaluated at 25 °C and 90 °C. The texture and color evolution for 16% (w/w) gels were evaluated. Proximate compositions of the flours were quantified. Rice, refined and whole wheat flours were analyzed as reference. The minimum flour concentration required for gel formation from the three tef varieties was 6–8%, similar to wheat flour. All tef flour suspensions pre-heated to 95 °C led to gels with a solid-like behavior (G′ > G″), both at 25 °C and 90 °C, with higher consistency than wheat gels at the same concentration. The dependence of viscoelastic moduli with concentration fulfilled the power law. The Avrami model was successfully fitted to the textural evolution of tef gels. Important differences were observed among tef and rice and wheat flours, probably contributed by their differences in protein, starch, lipid and fiber constituents. Gelling properties characterized suggest that tef flours would be suitable ingredients in gel food formulations.     

Stand establishment and early field vigour variation in a tropicalised shrunken-2 maize population

Low field emergence and early field vigour are major problems in shrunken-2 maize (sh-2). The genetic variability for stand-ability and early field vigour in a shrunken-2 maize population previously improved for adaptability to a tropical environment was investigated using a Design I mating system in which 40 randomly sampled males were crossed to four randomly sampled plants that served as females. Plants of the 160 crosses, representing full- and half-sib relationships, were evaluated in four sets, each composed of 40 crosses derived from 10 males during two growing seasons. Experimental design was randomized complete block with three replications. Difference in Emergence Index (EI) was not significant between the two seasons. Emergence Percentage (E%), Emergence Rate Index (ERI), and early field vigour traits viz. vigour score and seedling height determined at 28 days after planting (DAP) were, however, significantly (P < 0.05–P < 0.01) better in the first growing season. For all traits, the ‘female/male’ item was significant (P < 0.01) while ‘male’ was mostly non-significant. ‘Season × female/male’ interaction was significant for stand establishment traits but not for early field vigour traits. Averaged over all traits, dominance variance was 8.2 times higher than additive variance. Genetic variation for stand establishment and early field vigour in the tropicalised shrunken-2 maize population would be best exploited through the development of inbred lines, hybrids and synthetics. Broad-sense heritability was 53.0% for E%, 36.0% for EI, 33.0% for ERI, 71.5% for vigour score and 90.0% for seedling height. One hundred-seed weight ranged between 82.0 and 182.0 mg but correlation coefficients between seed weight on one hand, and E%, EI, ERI, vigour score and plant height on the other hand, were low (mostly <0.30) and, in general, non-significant. Emergence percentage had the highest average genotypic correlation value with the other traits studied (Mean Absolute Value = 0.71 in the first season and 0.45 in the second season). Emergence percentage, determined 10 days after planting, thus has potential for use as a selection index for stand establishment and early field vigour.     

Temperature-dependent development of Ascotis selenaria (Lepidoptera: Geometridae) and its stage emergence models with field validation

Temperature-dependent development of Ascotis selenaria (Denis et Schiffermüller) was studied in the laboratory. Time to egg eclosion decreased with increasing temperature and ranged from 17.4 d at 16 °C to 5.0 d at 30 and 32 °C. Total development times of larvae decreased from 54.7 d at 16 °C to 17.3 d at 32 °C. The development time of pupae ranged from 29.7 days at 16 °C to 10.2 days at 30 and 32 °C. Eggs, larvae and pupae did not develop successfully to the next stage at 12 and 35 °C. The estimated lower temperature thresholds were 10.4, 9.3, and 9.8 °C for eggs, larvae, and pupae, respectively. Thermal constants of egg, larvae, and pupae were 88.5, 370.4, and 188.7 DD, respectively. Stage emergence models for eggs, larvae, and pupae of A. selenaria were constructed by using the development rate model (Lactin 2 function) and development distribution model (three-parameter Weibull function), which simulate the proportion of individuals shifted from one stage to the next. Pearson's correlation coefficients between actual observations in the field and model outputs were statistically significant with 0.99, 0.68 to 0.87 and 0.96 to 0.98 for egg, larval and pupal stage emergence model, respectively. The egg stage emergence model could be used to facilitate spraying time as it successfully predicted the first instar larval population. Predictability of the pupal stage emergence model was greatly improved when the physiological age of overwintering pupae was assumed to be in various state. The stage emergence models developed here should be useful to construct an A. selenaria population model.     

Life history of Closterotomus (Calocoris) trivialis (Costa) (Heteroptera: Miridae) in olive and citrus orchards in Crete

The population density of Closterotomus trivialis (Costa) and its damage potential were studied in citrus and olive orchards of Crete. C. trivialis was found to be most abundant in wild radish Raphanus raphanistrum L., annual mercury Mercurialis annua L., Urtica sp. and upright pellitory Parietaria officinalis L. compared to mallow Malva sylvestris L., prickly goldenfleece Uropermum picroides (L.), sowthistle Sonchus oleraceus L., citrus or olive trees. Its damage potential on the setting of olive fruit was investigated at the early inflorescence stage. When 1, 5 or 10 adults of C. trivialis were enclosed with stems at the 55th and 57th phenological growth stages, the number of fruits was significantly reduced compared to controls.The developmental biology of individuals of C. trivialis was studied on R. raphanistrum at seven constant temperatures 15, 20, 25, 30, 32.5, 35 and 37 °C, under laboratory conditions. No nymphs survived above 35 °C. The highest nymph to adult survival (89.6%) was found at 20 °C and the lowest (40.6%) at 32.5 °C. Mean developmental time as well as adult longevity decreased with increasing temperature. The developmental time from 1st nymphal instar to adult ranged from at least 9.0 at 32.5 °C to 27.8 days at 15 °C. The adults lived from 2.9 days at 32.5 °C to 45.3 days at 15 °C. It required 212.7 degree-days to complete development above a minimum threshold of 7.72 °C as estimated by linear regression and 8 °C as estimated by nonlinear model. The importance of these findings in the management of this species through the prediction of its seasonal appearance is discussed.     

Effect of short heat shocks applied during grain development on wheat (Triticum aestivum L.) grain proteome

In the field, developing cereal grains are often exposed to short periods of very high temperature (>35 °C) that may dramatically affect grain yield and flour quality. Here we report on the effect of 4 h of heat shock (HS) at 38 °C applied on four consecutive days during the linear phase of storage compound accumulation on grain proteome of the winter bread wheat. At maturity the average single grain dry mass and the total quantity of nitrogen per grain were 25% and 16%, respectively lower for the HS treatment than for the control, resulting in a higher (+1.6% dm) grain protein concentration in HS grains. Individual albumin–globulin, gliadin and glutenin protein fractions from grains collected just before the HS and 1, 8, and 26 (ripeness maturity) days after the HS were quantified then analysed by 2-dimensional electrophoresis followed by MALDI-TOF and MS/MS identification. The quantity per grain of 10 gliadins and 3 low molecular weight glutenin subunit proteins were significantly affected by HS. Thirty-eight HS responsive albumin and globulin proteins were identified, including several enzymes involved in carbohydrate, redox, and lipid metabolisms. One protein was transitorily induced in response to HS. Detailed discussion of the expression of these proteins is presented.     

Effect of temperature on the developmental time,survival of immatures and adult longevity of Aganaspis daci (Hymenoptera: Figitidae), a natural enemy of Ceratitis capitata (Diptera: Tephritidae)

Longevity, developmental time and offspring survival of parasitoid wasps are decisive in their effective performance as biocontrol agents. Optimum temperature range determines parasitoid survival, development and reproduction. Thus, controlling this abiotic factor is a key to the success of pest management programs. Adult longevity, developmental time from egg to adult and survival of immatures of Aganaspis daci were assessed in the laboratory under different constant temperatures; adult longevity without hosts, but with the provision of water and honey, and developmental time and survival of immatures from host pupae, whose larvae had been exposed to parasitoids. Results showed that longevity depended on temperature decreasing in the range 15–20 °C (36 – 25 days), but was lower in the range 25–35 °C (10 – 7 days). Regarding developmental time from egg to adult and survival of immatures, our results showed that 20 and 25 °C are the most suitable temperatures. At 15 and 30 °C mortality of the immature stages was very high (>90%) or developmental time to adult was very slow (>3 months). Immatures did not survive at 35 °C. We found no significant differences in developmental time to adult or survival of immatures between 20 and 25 °C. The sex ratio of parasitoid progeny was female biased at 25 °C; the proportion of females increased at all cases with temperature. The t_o and K for total development were 8.5 °C and 500 DD, respectively. Our findings provide some guidance for future inundative or inoculative field releases of this parasitoid for the management of Ceratitis capitata in Spain.     

Use of tomato crop residues into soil for control of bacterial wilt caused by Ralstonia solanacearum

Tomato debris can be used as the soil amendment to reduce agricultural residue accumulation problems and increase soil fertility. However, pathogens present in the debris may form a risk for subsequent crops. In this study, tomato growth substrate was amended with tomato debris artificially inoculated with Ralstonia solanacearum and the effect of heat treatments on the survival of the pathogen was measured. Experiments were carried out in the laboratory and in greenhouses, using peat moss and sand mix in pots as substrates. Pots were enclosed in plastic bags or left open. Then 0, 5, 10 and 15 g of tomato debris were applied to 500 g growing medium, with four replicates per treatment. Treatments at 45 °C lowered tomato wilt indices in tomato cv. Money-Maker and that the pathogen was not eradicated after pot treatments at 25 °C. R. solanacearum remained pathogenic on the assayed growing media after a six-week treatment at 25 °C, but was eradicated after treatments at 45 °C. The lower infectivity of infected debris tomato plants when buried with high doses of organic matter and at temperatures above 45 °C suggests that adverse effects on the soil inoculum would be exerted through increased soil temperatures. This study demonstrates that tomato crop residues, usually considered waste material, could be used as soil amendments to reduce their effect as a source of contamination as they offer additional advantages.     

In vitro starch digestibility and pasting properties of germinated brown rice after hydrothermal treatments

Germinated brown rice (GBR) recently has received renewed attention due to its enhanced nutritional value. Pasting properties and in vitro starch digestibility of GBR were examined before and after hydrothermal treatments. Steeping in water (30 °C, 24 h) raised the moisture content and germination percentage of brown rice. Pasting viscosity was substantially decreased but gelatinization temperatures and enthalpy were decreased only marginally by germination (30 °C, 48 h). However, annealing (50 °C, 24 h) and heat-moisture treatment (100 °C, 1 h at 30% moisture) after germination resulted in increased pasting viscosity and gelatinization temperatures. The hydrothermal treatments, however, induced browning reactions to darken the flour of GBR. The digestibility of starch in brown rice was increased by germination. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in the cooked brown rice were 47.3%, 40.8%, and 11.9%, respectively, but changed to 57.7%, 39.1%, and 3.2%, respectively upon germination. The hydrothermal treatments, however, decreased the digestibility of starch in GBR. The heat-moisture treatment decreased the RDS content in GBR near to that of native brown rice. The digestibility and physical properties of brown rice can be controlled by germination and hydrothermal treatments.     

Control of brown rot of stone fruits by brief heated water immersion treatments

The effectiveness of brief (30 or 60 s) immersion in water at 24, 50, 55, 60, 65, or 70 °C was evaluated for the control of brown rot, caused by Monilinia fructicola, on California-grown peaches, nectarines, and plums. Inoculated fruits were treated and either stored at 20 °C for 5 days or at 0 °C and 95% RH for 30 days followed by 5 days at 20 °C to simulate commercial marketing conditions. Immersion in water at 55 °C for 60 s or at 60 °C for 30 or 60 s significantly reduced both decay incidence and severity among the remaining wounds that developed the disease. Water temperatures of 65 °C or higher were phytotoxic and caused moderate to severe surface injuries. Immersion in water at 60 °C for 60 s was effective for plums and it reduced the incidence of brown rot from more than 80% among control fruit to less than 2%. In nectarines, this treatment reduced decay incidence from 100 to less than 5% on fruit stored at 20 °C and from 73 to 28% on cold-stored fruit. Therefore, brief immersion in heated water can be an effective approach to manage postharvest brown rot of stone fruits, especially for the organic fruit industry.     

Effect of biocontrol agent Bacillus amyloliquefaciens and 1-methyl cyclopropene on the control of postharvest diseases and maintenance of fruit quality

Efficacy of biocontrol agent Bacillus amyloliquefaciens PPCB004 was evaluated on the control of anthracnose and phomopsis rot in ‘Solo’ papaya pre-treated with 1-methyl cyclopropene (100 μl) (1-MCP) during storage. This treatment was compared to the untreated control, commercial treatment (washing in chlorinated water), stand alone 1-MCP and PPCB004 treatment. Although fruit pre-treated with 1-MCP delayed the ripening (100% yellow) after cold storage by 9-10 d, it showed higher incidence and severity of anthracnose and phomopsis rot than the fruit subjected to commercial treatment. Application of PPCB004 after 1-MCP pre-treatment (1-MCP + PPCB004) reduced the anthracnose and phomopsis incidence and severity after cold storage (10 °C, 85% RH for 14 d) and ripening at 25 °C. The 1-MCP + PPCB004 treatment helped to retain the fruit firmness, overall quality and uniform yellow skin (100%) and flesh colour after ripening. The PPCB004 was effectively recovered from stand alone PPCB004 and 1-MCP + PPCB004 treated fruit after cold storage and ripening. The PPCB004 population showed an increase by 1 log units after ripening in 1-MCP + PPCB004 treated fruit. After ripening the recovery of PPCB004 population was higher (0.7 log units) in 1-MCP + PPCB004. The total recovery of fungal population on the fruit surface after ripening was lower in 1-MCP + PPCB004 and stand alone PPCB004 treated fruit. It can be concluded that application of B. amyloliquefaciens PPCB004 with 1-MCP pre-treated papaya (at 25-30% skin yellow stage) can significantly reduce disease incidence associated with 1-MCP treatment. This treatment has the potential for commercial application in the ‘organic’ papaya industry.     

Timing and efficacy of insecticides for control of mussel scale, Lepidosaphes ulmi, on apple using predictive models

The timing and pattern of mussel scale (Lepidosaphes ulmi (L.)) crawler emergence was monitored in relation to air and bark-surface temperatures using sticky band traps around branches in apple orchards in Kent, UK in three successive years, 2007-2009. The emergence and migration of the crawlers lasted for over 4 weeks at a high level, much longer than had been previously reported. In all three years, there were clearly two peaks of emergence of the crawlers, possibly because there is a diapausing and non-diapausing form of the insect. A temperature sum model developed in the 1990s in The Netherlands using air temperatures predicted the peak emergence of crawlers to within 5-16 days; however, the model was less accurate when tree bark temperatures for the north or south of the tree were used. We have developed two models to predict the emergence of the crawlers by revising the original Dutch model. The observed emergence period (5-95%) was longer than the predicted in all three years but the two revised models performed better than the original Dutch model.In two experiments, in 2007 and 2008, the efficacy of a wide range of insecticide products at different timings during crawler emergence was evaluated. Of the 7 products compared as single or two sprays (spray volume 500 l ha⁻¹) at different emergence timings, or with the addition of adjuvants or as winter treatments, thiacloprid 480 g/l SC (375 ml ha⁻¹) and acetamiprid 20% w/w SP (375 g ha⁻¹) gave the best and similar control, reducing the percentage of fruits infested by 94%. Two sprays of fenoxycarb 25% w/w WG (600 g ha⁻¹) gave the poorest control (28%). Two sprays of spirodiclofen 240 g/l SC (600 g ha⁻¹), chlorpyrifos 75% w/w WG (960 g ha⁻¹) or flonicamid 50% w/w WG (140 g ha⁻¹) gave intermediate results, reducing the percentage infestation by 72% on average. Adjuvants gave no additional value to the treatments when applied in admixture and winter applications of mineral oil (spray volume 1000 l ha⁻¹), alone or in admixture with chlorpyrifos or thiacloprid were not effective at controlling mussel scale the following growing season.Overall, acetamiprid and thiacloprid were the most efficacious insecticides and this study indicates that sprays are best applied in the latter part of the migration (after 50% emergence) with an interval between sprays of at least two weeks to span the long emergence period of the pest.     

The Effect of Day to Night Temperature Variation on Leaf Development in Wheat

Summary

The rate of leaf development in wheat is related to time and temperature in units of degree-days (DD) leaf^?1 (phyllochron). Experiments were conducted in controlled environment chambers to study the effect of day to night variation in temperature on leaf development in two wheat cultivars, Penawawa and Stephens. Plants were grown at constant 20°C, and in eight day/night temperature ranges as wide as 8/32°C to 32/8°C, all with a mean temperature of 20°C. The leaf number on the main stems was counted (in Haun units) every other day, from the emergence of the 2nd leaf until the emergence of the 5th leaf. Leaf phyllochron values were derived from the inverse of the slopes of the linear regression of leaf number on DD. Phyllochron values ranged from 99 to 153 DD leaf^?1. The phyllochron values were greater when higher temperatures were imposed at night under extreme day to night temperature treatment.     

Response of spring planted barley (Hordeum vulgare L.), oats (Avena sativa L.) and wheat (Triticum aestivum L.) to mesotrione

There is little information on the response of spring planted barley (Hordeum vulgare L.), oats (Avena sativa L.) and wheat (Triticum aestivum L.) to mesotrione under Ontario environmental conditions. Four field studies were conducted in Ontario, Canada over a two-year period (2008 and 2009) to evaluate the sensitivity of spring planted cereals (barley, oats, and wheat) to pre-emergence (PRE) and post-emergence (POST) applications of mesotrione at 50, 100, and 150 g ai ha⁻¹. Mesotrione applied PRE caused minimal visible injury at 3, 7, 14 and 28 days after emergence (DAE) and had no adverse effect on plant height or yield of barley, oats and wheat. Mesotrione applied POST caused as much 11% injury and reduced plant height as much as 6% in spring planted cereals. Injury was higher in wheat compared to barley or oats. Mesotrione applied POST had no adverse effect on the yield of barley or oats but decreased the yield of wheat as much as 14%. Based on this study, mesotrione applied PRE at 50, 100 or 150 g ai ha⁻¹ can be safely used in spring planted barley, oats, and wheat. Mesotrione applied POST at the proposed dose of 50, 100 or 150 g ai ha⁻¹ can also be safely used in spring planted barley and oats. However, mesotrione applied POST results in unacceptable injury in spring planted wheat.