Trunk injection: An alternative technique for pesticide delivery in apples

Field studies, laboratory bioassays, and residue profile analysis were used to determine the seasonal effectiveness of trunk injected pesticides against key apple disease and insect pests. Insecticides formulated for trunk injection, imidacloprid (Ima-jet™), rynaxypyr (XCL-r8™), and emamectin benzoate (TREE-age™) were injected into semi-dwarf Empire apple trees Malus domestica (Borkhausen) and evaluated for a wide range of insect pests. The fungicide compounds, propiconazole (Alamo^®), phosphites (Phospho-jet), and penthiopyrad (Fontelis™), were injected into semi-dwarf MacIntosh (RedMax) apple trees M.domestica (Borkhausen) for control of apple scab fungus, Venturia inaequalis (Cooke). After the original single injection, imidacloprid was highly effective in controlling piercing and sucking pests such as the potato leafhopper, Empoasca fabae (Harris), and aphids (Aphididae), and emamectin benzoate was highly effective in controlling the oblique banded leaf roller, Choristoneura rosaceana (Harris), and potato leafhopper, E. fabae (Harris), and rynaxypyr was highly effective in controlling Oriental fruit moth, Grapholita molesta (Busck), and leafrollers all for two growing seasons. The residue profiles for insecticides showed that vascular delivery was predominantly to foliage, with fruit residues far below the EPA maximum residue limits (MRLs), and low to no residues detected in apple flower parts. Phosphites provided significant levels of apple scab control over two seasons for the single injection after the foliage recovered from the phytotoxicity damage in the first season. Propiconazole and penthiopyrad showed limited effectiveness for the control of apple scab. The residue profiles for fungicides showed phosphites to be delivered primarily to foliage, but inconsistent foliar residue levels for the other two compounds suggests possible incompatibilities may be responsible for poor product performance. These incompatibilities may include molecular or chemical properties. For example, on the molecular level such as the molecular size too large to fit through vascular tissue and chemical properties such as the viscosity of the compound resulting in poor translocation or pH.     

Effects of combined application of potassium phosphite and fungicide on stem and sheath disease control,yield, and quality of rice

Phosphite has been shown to suppress some diseases in different plant species but disease control in rice has not been investigated. In 2012/13 and 2013/14 potassium phosphite was sprayed at 1775 g ha⁻¹ and 3550 g ha⁻¹ in field plots of rice in Uruguay to determine if phosphite alone or in combination with label rates of a mixed strobilurin and triazole fungicide could be used to effectively control stem rot and aggregate sheath spot in irrigated rice. Six treatments consisting of different combinations of potassium phosphite alone or with a fungicide and an unsprayed control were assayed in one application at late-boot to early-heading. Phosphite alone in single and double rate slightly reduced severity and incidence of stem rot and produced a small yield increase over the unsprayed control. Fungicide at a 50% label rate with phosphite reduced stem rot severity and incidence to a similar level as the fungicide alone applied at the label rate. Disease severity was reduced by approximately 25% and incidence by 17–20% when compared with untreated control. Yield increase was 5% for both treatments over the unsprayed control. Fungicide combined with phosphite at single and double rates reduced stem rot severity by 40–45% and incidence by 34–38% when compared with untreated control, with yield increased by 10% over the unsprayed control and 5% over plots treated with a fungicide. These results indicate that a single application of potassium phosphite combined with fungicide can be used efficiently to manage of rice stem diseases.     

Economic returns from fungicide application to control husk spot of macadamia in Australia is influenced by spray efficiency,rates and costs of application

Fungicides are commonly applied as prophylactic sprays, with the expectation of increased yield and kernel quality, to control husk spot of macadamia in Australia. However, economic benefits from fungicide applications to control husk spot have rarely been quantified. We investigated the effectiveness, efficiency and economic returns of fungicide spray applications for husk spot control using three different spray application volumes and two dose rates of tank mixtures of carbendazim and cupric hydroxide under commercial macadamia orchard conditions. Husk spot incidence and severity were significantly (P < 0.001) different among the treatments and between the two years. In both years, the rate of fruit abscission was highest in the untreated control followed by low spray application volumes, but reduced with increasing spray volume. The quality and value of nut-in-shell increased when nut abscission was delayed. Poor quality and low nut-in-shell value of $2.85 kg⁻¹ in 2010 and $2.12 kg⁻¹ in 2011 were obtained in the untreated control trees that abscised early in the harvest period compared with the average nut-in-shell value of $2.95 kg⁻¹ in 2010 and $2.46 kg⁻¹ in 2011 in the fungicide treated trees. Gross margins for each fungicide treatment schedule compared to the untreated control averaged over both years showed positive contributions of 20%, 10% and 6% for the high, moderate and low dilute rate volume applications, respectively. Our data further indicates that dilute rate applications at higher volume may be more beneficial and cost-effective than concentrate rate applications in husk spot control programs. Overall, harvest yield increased by 11%–33% when husk spot was controlled using fungicide sprays compared to no fungicide spray applications. The benefit-cost ratios revealed highly significant benefits for the implementation of husk spot management programs.     

Effect of watered-in demethylation-inhibitor fungicide and paclobutrazol applications on foliar disease severity and turfgrass quality of creeping bentgrass putting greens

Preventive, watered-in applications of DMI fungicides provide control of several soilborne turfgrass diseases on golf putting greens. The objectives of this two-year field study were to determine the impact of these applications on foliar diseases, and evaluate the impact of application timing of paclobutrazol, a plant growth regulator, on disease severity and turfgrass quality. Triadimefon (1.58 kg a.i. ha⁻¹), tebuconazole (0.82 kg a.i. ha⁻¹), metconazole (0.43 kg a.i. ha⁻¹), and triticonazole (0.64 kg a.i. ha⁻¹), were applied twice in late April and May and immediately watered in to the soil profile with 5 mm of post application irrigation. Paclobutrazol (0.28 kg a.i. ha⁻¹) was applied alone, in a tank-mix with the fungicide application, 7 days or 14 days after the fungicide application. Overall dollar spot severity, assessed as area under the disease progress curve (AUDPC), was significantly lower in fungicide treated plots than non-treated plots in both trial years. The date of threshold symptom observation (≥5 infection centers per plot), however, was not different between fungicide treated and non-treated plots in 2011. Triadimefon treated plots had lower AUDPC values than other fungicide treatments. Brown patch severity was not significantly different among treatments. Paclobutrazol applied alone did not reduce dollar spot or brown patch severity, however, paclobutrazol + fungicide treatments resulted in lower dollar spot severity than plots treated with fungicide alone. Short-lived phytotoxicity (bronze discoloration) was observed in plots treated with triadimefon or paclobutrazol + fungicide. Spring preventive fungicide applications targeted at soilborne disease control also provided residual control of dollar spot in this study.     

Fungicide and cultivar effects on the development and temporal progress of wheat blast under field conditions

The epidemiology of wheat blast, caused by the Triticum pathotype of Pyricularia oryzae, is poorly understood, making it very difficult to manage. We reported on the individual and combined effect of host resistance and fungicide application for managing wheat blast disease on spikes. Two field experiments (Exp. 1 and Exp. 2) were conducted in a region of Brazil where blast is not known to be endemic to evaluate its development as influenced by fungicide and host resistance. Plots of wheat cultivars BR-18 (partially resistant) and Guamirim (susceptible) were either treated with the fungicide epoxiconazole + pyraclostrobin or left non-treated, and then inoculated with a spore suspension of P. oryzae at mid-anthesis. Spike blast incidence and severity, quantified at regular intervals after inoculation, increased over time, and fungicide and cultivar had statistically significant effects (P < 0.005) on both measures of disease and their temporal rates of progress. Relative to Guamirim-non-treated, BR-18-non-treated (resistance alone) led to 44 and 64% control of final incidence and severity, respectively, in Exp. 1, and 3 and 49% control, respectively, in Exp. 2. Guamirim-treated (fungicide alone) led to 65% control of incidence and 77% control of severity in Exp. 1, and 64% control of incidence and 95% control of severity in Exp. 2. For both incidence and severity, fungicide and resistance alone also reduced the temporal rate of progress relative to the susceptible non-treated. However, the greatest overall efficacy was observed when resistance and fungicide were combined, with over 70 and 90% control of final incidence and severity, respectively, and over 75% reduction in the temporal rate of spike blast progress. Based on percent control, the integrated effect of resistance and fungicide was additive for incidence, severity, and their temporal rates of progress, demonstrating the value of combining the two strategies to manage spike blast.     

Effect of pre-harvest calcium chloride applications on fruit calcium level and post-harvest anthracnose disease of papaya

Anthracnose disease of papaya, caused by Colletotrichum gloeosporioides Penz, can cause extensive postharvest losses. The goal of this research was to use pre-harvest calcium applications to reduce anthracnose disease. Six pre-harvest foliar calcium sprays were applied biweekly to papaya trees in experimental orchards at Universiti Putra Malaysia. Additional in vitro and in vivo tests were carried out to test the effect of calcium on fruit calcium content, spore germination, mycelial growth and disease severity. Calcium chloride at 1%, 1.5% and 2.0% concentrations significantly decreased spore germination. Calcium content of papaya fruit was significantly increased by calcium sprays at a concentration of 2.0% in 2012 and 2013. In vivo studies showed that increasing calcium content in fruit by calcium sprays at 1.5 and 2.0% concentrations significantly reduced anthracnose incidence of fruits during five weeks storage at 12 ± 2 °C, and delayed initiation of disease symptoms by four weeks.     

Assessment of the antimicrobial activity of Lentinula edodes against Xanthomonas campestris pv. vesicatoria

Bacterial spot of tomato (Solanum lycopersicum) caused by Xanthomonas campestris pv. vesicatoria (Xcv) is a devastating disease of tomato world-wide. In the southeastern United States, high summer temperatures and humidity are ideal conditions for this disease, resulting in defoliation, fruit spotting and a significant reduction in fruit yield. Current organic production practices restrict the use of synthetic chemicals for disease control; hence, there is a need for the development of new and effective biopesticides to mitigate plant diseases. Among several biological agents with potential for disease control, Lentinula edodes (shiitake mushroom) has been shown to have antibacterial properties. A controlled-environment study was therefore conducted to validate L. edodes mycelia culture filtrate (Le_mcf) foliar application to control bacterial spot of tomato using the cultivar Agriset 761. Lentinula edodes mycelia culture filtrate foliar spray significantly suppressed bacterial spot incidence in tomato foliage in vitro but was not effective in vivo. The phytotoxicity symptoms in Le_mcf-treated tomato foliage were attributed to the presence of 422.78 μg of oxalic acid per milliliter of Le_mcf (quantified by high-pressure liquid chromatography). Plant height and flowering were normal in Le_mcf-treated plants. Additionally, Le_mcf seed treatment did not adversely impact tomato germination but significantly enhanced the germination of marginal tomato seeds subjected to biotic stress (Xcv). Our results suggest that after eliminating oxalic acid from Le_mcf, the product may be a potential biopesticide for managing bacterial spot of tomato. Future greenhouse or field experiments should be conducted after eliminating oxalic acid from L. edodes culture filtrates.     

Managing White Mold of Potatoes in a Rainfed Environment

The goal of this research was to evaluate the management techniques of cultivar selection, fungicide application number, fungicide spray timing, and nitrogen rate management. Cultivars of Superior, Shepody, and Russet Burbank were observed to differ in disease severity and yield. White mold was observed to be a yield limiting factor for Superior with r² values of 0.65 and 0.66 for the relationship between white mold severity and total and marketable yield, respectively. In contrast, Russet Burbank and Shepody had only 2 % to 4 % of yield variation explained by white mold severity. Superior showed significant yield responses to two boscalid applications as opposed to one or zero, and was the only cultivar to show a response to fungicide application number. Analysis of fungicide application timing showed discrepancies between responses of severity (quadratic effect) and yields (linear effect). Lowest severity was modeled to be at applications made at peak flowering, while highest yields were modeled to be at applications made prior to. Nitrogen rates were observed to affect white mold incidence whereby disease counts were elevated at nitrogen application rates below 134 kg/ha as compared to application rates in excess of 134 kg/ha.     

Spray volume and fungicide rates for citrus black spot control based on tree canopy volume

The control of citrus black spot (CBS) caused by Phyllosticta citricarpa relies mainly on fungicide sprays. Generally, high and non-standardized spray volumes are adopted and the sprays are based on litre per tree or per hectare. However, the tree canopy volume may vary with age, density and variety, and this is expected to impact on the spray volume and fungicide rates needed for disease control. This study evaluated the efficacy of different fungicide spray volumes and rates for CBS control based on the tree-row-volume (TRV) concept. Two field trials were carried out during three seasons in São Paulo state, Brazil. Trials were set up in commercial orchards of late-maturing ‘Valencia’ sweet orange grown for juice production. In field trial 1, the volumes tested were 125 (standard), 100 (internal runoff point), 75 (intermediate) and 50 (half the internal runoff point) mL of spray mixture/m³ of the tree canopy. In field trial 2, 100 and 50 mL/m³ were evaluated. The fungicide rates ranged from 40 to 110 mg of metallic copper/m³ and from 1.9 to 4.7 mg of pyraclostrobin/m³. Untreated control trees (UTC) were kept unsprayed. CBS incidence and severity, premature fruit drop, yield, fungicide deposition and spray coverage were evaluated. All spray volumes tested reduced CBS incidence and severity on fruit at 75–95% and resulted in 1.6–3.0-fold higher yields than the UTC. However, a slight trend of more CBS symptoms and fruit drop, and lower yield was observed for trees treated with 50 mL/m³ compared to those treated with higher volumes. Spray volume change, from 125 to 75 mL/m³, irrespective of fungicide rate correction, led to a 40% reduction of CBS spray costs and water usage and increased the financial return of the control by up to 35%. TRV-based sprays may contribute to sustainable citrus production by reducing costs and environment impacts while maintaining efficient CBS control.     

Potassium phosphite for control of downy mildew of soybean

Downy mildew of soybean, caused by Peronospora manshurica, is widely spread throughout Brazil. The objective of this study was to evaluate the use of potassium phosphite to control this disease. Field experiments were conducted during the growing season of 2006/2007 and 2007/2008 in the state of Parana in southern Brazil. The experimental design consisted of completely randomized blocks in a factorial arrangement (4 × 2) with four replications. Four rates of potassium phosphite (0, 375, 750 and 1500 g P₂O₅ + K₂O ha⁻¹) were applied at two growth stages, V6 (fifth trifoliolate leaf) and R2 (full flowering), followed by one or two applications of pyraclostrobin and epoxiconazole (66.5 + 25 g a.i. ha⁻¹) at R3 (pod development) or R2 and R5.1 (10% of pod filling), mainly for the control of Asian soybean rust (Phakopsora pachyrhizi) and powdery mildew (Microsphaera diffusa). Field experiments were conducted to quantify the severity of downy mildew on leaves, nutrient content in leaf tissue (N, P and K), leaf area index (LAI), yield and seed weight. The maximum severity of downy mildew was observed at a growth stage of R5.3 (50% of pods were ripe), with 14% and 46% of the leaf area affected in 2006/2007 and 2007/2008, respectively. Also it was detected some effect of phosphite on Asian rust control but it was mostly in the trial of 2007/08 when the epidemic was very low (9.7-21.8% of severity). There was a linear reduction in the severity of downy mildew and a significant improvement in the LAI with an increase in the rate of phosphite applied. During the 2006/2007 growing season, a significant yield improvement was observed due to the application of the highest rate of phosphite. Two fungicide applications following phosphite application significantly improved the control of Asian soybean rust and powdery mildew, yield and seed weight when compared to a single fungicide application.     

Economics of foliar fungicides for hard red winter wheat in the USA southern Great Plains

Grain yields of winter wheat (Triticum aestivum L.) in the southern Great Plains are often reduced by the presence of foliar diseases. This study was conducted to determine whether the application of foliar fungicides is an economically optimal management strategy. The effects of fungicide treatment on commercially available hard red winter wheat varieties with differing levels of genetic resistance (i.e., resistant, intermediate, and susceptible) to foliar diseases were investigated at two locations, Apache and Lahoma, OK, USA, for the harvest years 2005–2012. Two fungicides were rotated between the two locations and applied at approximately Feekes growth stage 9–10.5. When averaged across years, plots to which fungicide was applied generated greater average net returns than plots that did not receive fungicide for susceptible varieties at Apache, and for resistant, intermediate, and susceptible varieties at Lahoma. However, foliar fungicide application was not economical in every year at either location suggesting fungicide use should be reassessed each year given that profitability depends on year specific yield potential, prices, and foliar disease conditions. At both locations high disease incidence occurred in all but one site-year when the average March through May relative humidity exceeded 65%. Additional research would be required to determine the relationship between weather, including relative humidity, and disease incidence, and to develop an economic threshold for treatment decision aid.     

Failure of metalaxyl to eradicate late blight on potatoes (cv. Green Mountain)

Eradication of potato late blight with metalaxyl was examined in field studies from 1980 to 1983. In 1980 disease outbreak and subsequent progression were late and moderate. In 1981 and 1983, they were early and moderate to severe, while in 1982 the disease became established later in the season but developed rapidly and resulted in moderate to severe damage to foliage. There were no significant differences in foliar disease severity among metalaxyl treatments. While treated plots generally showed significantly less foliar damage throughout the season than untreated plots, except in 1983, the reduction in foliar damage in September was only 30–50% in 1980, 10–20% in 1981, 20–30% in 1982, and less than 10% in 1983. Sporulation of the pathogen occurred readily on infected leaves of both treated and untreated plants. There were no significant differences in yield, but application of metalaxyl to foliage significantly reduced the incidence of late blight tuber rot.     

Effect of foliar treatments to durum wheat on flag leaf senescence, grain yield, quality and deoxynivalenol contamination in North Italy

Since the production of durum wheat in the drier areas of the Mediterranean Basin is characterized by high variability in terms of yield and grain quality, there is also considerable interest in developing durum wheat in the northern regions, where the pedo-climatic conditions can offer the possibility of obtaining grain yields with higher technological quality and stability. However, the climatic conditions in the northern regions make durum wheat more prone to fungal foliar disease, particularly to Septoria Tritici Blotch (Septoria tritici Rob.) and to Fusarium Head Blight (Fusarium graminearum Petch and Fusarium culmorum Sacc.), with the consequent occurrence of DON in grains.Field experiments have been conducted over two growing seasons at four sites in North West Italy to evaluate the effect of fungicides and foliar nitrogen fertilizer application on durum wheat yield and grain quality. Five combinations of foliar application were compared at each site and each year (untreated control, azole fungicide application at heading, strobilurin fungicide at the stem elongation stage and/or at heading, the addition of a foliar N fertilizer to a fungicide programme). The following parameters were analysed: Septoria Tritici Blotch (STB) severity, flag leaf greenness using a chlorophyll meter, grain yield, test weight, grain protein content, ash content, vitreousness, Fusarium Head Blight (FHB) incidence and severity and deoxynivalenol (DON) contamination. The collected data underline that the cultivation of durum wheat at the climatic conditions of North Italy is actually risky and needs a direct control of fungal disease, which would be able to reduce the development of both foliar and head attacks. The double treatment, with a strobilurin application during the stem elongation stage and azole at heading, results to be an essential practice and showed advantages in terms of the delay of flag leaf senescence (+27%), STB control (+31), FHB control (+11%), yield (+32%) and DON contamination (−45%), compared to the untreated control. Other foliar treatments at heading, such as strobilurin or foliar N fertilizer applications, do not seem to provide any further advantage, for either grain yield or quality. No significant effect of fungicide or foliar N fertilizer application was recorded on the protein or ash concentration or vitreousness.     

A comparative evaluation of post-infection efficacy of mefenoxam and potassium phosphite with protectant efficacy of azoxystrobin and potassium phosphite for controlling leather rot of strawberry caused by Phytophthora cactorum

Leather rot, caused by Phytophthora cactorum, is one of the most important fruit-rotting diseases of strawberry worldwide. Efficacy of mefenoxam and potassium phosphite against leather rot, when applied in a post-infection fungicide program, made in response to rain events was evaluated over 3 years of testing. Post-infection treatments of potassium phosphite and mefenoxam were compared with calendar-based treatments of azoxystrobin or potassium phosphite sprayed weekly, starting at late bloom (fruit set). In order to obtain high-risk conditions for infection (splash dispersal of the pathogen and subsequent infection periods), plots were flooded until standing water was observed between the rows. Post-infection applications were made within 36 h after the initiation of a flooding event. Leather rot incidence in the untreated controls ranged from 15 to 66% over the 3 years. All fungicide treatments had significantly (P < 0.001) less leather rot incidence than in the untreated control. There were no significant differences in leather rot incidence between the different fungicide treatments. Percent control (the percentage reduction in incidence relative to the check) was as high as 100% with all fungicide treatments. Mefenoxam and potassium phosphite post-infection (after flooding) provided control equal to that obtained with a calendar-based spray program, but with from 1 to 3 fewer fungicide applications.     

Evaluation of soil applied systemic acquired resistance inducers integrated with copper bactericide sprays for control of citrus canker on bearing grapefruit trees

Soil application of systemic neonicotinoid insecticides and the commercial systemic acquired resistance (SAR) inducer, acibenzolar-S-methyl (ASM), provides season-long control of foliar infection by Xanthomonas citri subsp. citri, the causal agent of citrus canker. Reduction in leaf disease incidence with ASM is comparable to protection with 21-day interval foliar sprays of copper hydroxide (CH). Soil applications of ASM alone, rotated with the neonicotinoids imidacloprid (IMID), thiamethoxam (THIA), and clothianidin (CLOTH), or combined with foliar sprays of CH were compared for canker disease control on fruit of 5- to 7-year-old bearing ‘Ruby Red’ grapefruit trees in Southeast Florida. All treatments significantly reduced the incidence of canker lesions on fruit compared to the untreated check. Soil drenches of ASM and season-long rotations with IMID, THIA, and CLOTH were as effective for suppressing fruit canker as season-long foliar sprays with CH. SAR inducers combined with CH sprays provided optimum control of fruit canker when initiated before the onset of the susceptible foliar flush in the spring. Additional control of canker with soil-applied SAR inducers may enable reduction in the frequency of copper sprays and reduce disease loss from copper resistant Xcc strains where they are prevalent.     

多肽在凯特芒果上的应用效果

以9龄生凯特芒果树为试材,施用不同浓度(常规施肥+多肽500倍液、常规施肥+多肽1 000倍液、常规施肥+多肽1 500倍液、常规施肥+1 000倍多肽叶喷施、常规施肥+清水对照)的多肽,研究其对芒果吸收部分矿质营养和品质的影响.结果表明:多肽能促进芒果果实吸收N、P、K素营养和改善果实品质.施用多肽500倍液,果实中N、P、K素营养含量分别比对照高12.1%、34.7%、17.2%,可滴定酸降低44.3%,可溶性总糖提高24.6%,抗坏血酸提高59.5%.     

Control of apple diseases and pests with low spray volumes and reduced chemical rates

Fungicides applied in volumes of either 100, 200 or 800 l/ha controlled apple scab in large-scale field experiments from 1982 to 1985. Either Sonax C, a formulated mixture of etaconazole and captan applied at 1 kg/ha (one-third the recommended rate), or fenarimol at 112 ml/ha (one-quarter the recommended rate), controlled scab when applied in 100 or 200 l/ha respectively. Scab was controlled with either eight protectant or at least five eradicant applications of Sonax C at either 3 or 1 kg/ha in 200 1 of water per hectare. In all years, weather conditions favoured the development of scab. In unsprayed trees the incidence of scabbed fruit ranged from 60% in cv. Granny Smith to 26% in cv. Jonathan. In sprayed trees fruit infection rarely exceeded 1%. The control of powdery mildew was unsatisfactory with Sonax C applied at 1 kg in 100 l/ha. Better control was achieved by either increasing the spray volume or the rate of fungicide per hectare. Two-spotted and European mites were controlled with propargite at the recommended rate of 5·5 kg/ha at either 200 or 800 l/ha. Codling moth was controlled with 160 ml/ha of azinphos-methyl (one-quarter the recommended rate) applied in 800 l/ha.     

Impact of a cultivar mixture on scab,powdery mildew and rosy aphid in an organic apple orchard

The impact of a cultivar mixture within the rows including the cvs Melrouge (low susceptibility to scab) and Pitchounette (Rvi6 resistant) was assessed during 2008–2009 in an organic apple orchard located in Rhône Valley (Drôme, France), on three important pests and diseases: scab, powdery mildew and rosy apple aphid. In this area, the resistance of Rvi6 gene was effective since the orchard plantation in 2004. The impact of the cultivar mixture was assessed per se, but also associated with sanitation practices to decrease the primary inoculum of scab and mildew, and compared to disease development on pure stands of Melrouge. The cultivar mixture showed a good efficiency to decrease the scab incidence on leaves and fruits; a significant effect on scab severity was observed in 2009 for the cultivar mixture plus sanitation practices. Our data confirmed the different susceptibility levels of the two cultivars for powdery mildew. Against powdery mildew, a favourable effect of cultivar mixture, at the condition it is associated with sanitation, was observed in case of a moderate level of the disease (2008). For rosy apple aphid, a favourable effect of cultivar mixture was observed on Melrouge in 2008 when Pitchounette has a good resistance level. In the context of organic production, the impact of the cultivar mixture seemed favourable for the control of the three pests and diseases.     

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Potato late blight caused by the oomycete Phytophthora infestans is a devastating disease of potato worldwide. Most of the potato cultivars grown in conventional agriculture are susceptible, or at best moderately resistant, and require frequent applications of fungicides to avoid heavy yield losses.In field trials spanning four years, we have investigated the effect of potassium phosphite, an inorganic salt on potato late blight. Potassium phosphite is known to induce defence responses in potato and to also have direct toxic effects on oomycetes, which in turn counteract late blight and tuber blight development. However, the use of this salt is not yet implemented and approved in European potato cultivation. We compared the effect of phosphite alone with fungicides currently used in Swedish potato cultivation. We also investigated the combined use of potassium phosphite and reduced doses of fungicides. Table potato cultivars and starch potato cultivars with different levels of resistance were used.We found that potassium phosphite in combination with reduced doses of fungicides results in the same level of protection as treatments with the recommended full dose of fungicides. These combined treatments reduce the need of traditional fungicides and may also decrease the selection pressure for fungicide resistance development in the pathogen. In relatively resistant starch potato cultivars using phosphite alone gave sufficient protection against late blight. Furthermore, in starch potato a combination of phosphite and fungicides at two-week intervals provided similar protection to weekly applications of fungicide at the recommended dose. Foliar treatment with phosphite also gave protection against tuber blight at similar levels to that of the best-performing fungicide. Our data suggests that potassium phosphite could be used in potato cultivation in temperate regions such as in Sweden, at least in combinations with reduced rates of fungicides. The implementation of the use of phosphite in practical potato crop protection as part of an IPM strategy is discussed. Doses, intervals and combinations could be adjusted to the level of cultivar resistance.     

Spray deposition assessment and benchmarks for control of Alternaria brown spot on mandarin leaves with copper oxychloride

Inadequate disease control on citrus foliage and fruit is often attributed to insufficient fungicide spray deposition on target surfaces. This study describes a novel spray deposition assessment protocol and determines deposition benchmarks indicative of the biological effectiveness for better interpretation of spray deposition results. Suitability of a yellow fluorescent pigment as tracer for copper oxychloride deposition was demonstrated through its similar particle concentration and size. Spray deposition assessment of spray targets, which were sprayed with a mixture that included the fluorescent pigment, involved photomacrography of whole leaf or fruit surfaces, followed by digital image analyses. This protocol proved to be very accurate in determining the quantity and quality of deposition. To determine deposition benchmarks, detached young ‘Nova’ mandarin leaves were sprayed with copper oxychloride and fluorescent pigment at different concentrations (0.1–2 times the recommended concentration) and spray deposition assessed. Subsequently, leaves were spray inoculated with a spore suspension of Alternaria alternata [causal agent of Alternaria brown spot (ABS) of mandarins], moist-incubated for c. 48 h and symptom expression rated. A very good linear relationship was found between fungicide concentration, leaf area covered by fluorescent pigment particles (%FPC) (r = 0.879) and Cu residue analysis (r = 0.992). A von Bertalanffy growth curve best fitted the relation between ABS control and deposition quantity (%FPC) data (91% of the percentage variance accounted for) with a good correlation between observed and predicted values (r = 0.825). Benchmarks for 50% and 75% disease control were calculated as 2.07 %FPC and 4.14 %FPC, respectively. These corresponded with Cu residue levels of 59.4 and 91.0 mg kg⁻¹, respectively. These FPC benchmarks can be used to evaluate spray technology research, specifically for control of ABS and similar citrus fruit and foliar diseases.