Drench Application Research Articles

Effect of spent mushroom compost tea on mycelial growth and yield of button mushroom (Agaricus bisporus)

Preliminary studies suggested that the use of compost tea made from spent mushroom substrate (SMS) may be regarded as a potential method for biologically controlling dry bubble disease in button mushroom. The aim of this study was to assess the effect of SMS compost tea on the host, the button mushroom, to ascertain whether the addition of these water extracts has a toxic effect on Agaricus bisporus mycelium growth and on mushroom yield. In vitro experiments showed that the addition of SMS compost tea to the culture medium inoculated with a mushroom spawn grain did not have an inhibitory effect on A. bisporus mycelial growth. The effect of compost teas on the quantitative production parameters of A. bisporus (yield, unitary weight, biological efficiency and earliness) was tested in a cropping trial, applying the compost teas to the casing in three different drench applications. Quantitative production parameters were not significantly affected by the compost tea treatments although there was a slight delay of 0.8-1.4 days in the harvest time of the first flush. These results suggest that compost teas have no fungitoxic effect on A. bisporus so that they can be considered a suitable biocontrol substance for the control of dry bubble disease.

Toward Fungicidal Management of Laurel Wilt of Avocado.

Laurel wilt threatens commercial and residential production of avocado (Persea americana) in Florida. Laurel wilt on redbay (P. borbonia) was controlled previously with macroinfusions (injections) of Alamo, an injectable formulation of propiconazole. To determine whether Alamo macroinfusion would be cost effective in commercial avocado production, economic analyses were conducted for various macroinfusion scenarios and a standardized production situation in southern Florida. Under prevailing conditions, macroinfusion was not cost effective. In the interest of identifying alternative means to manage the disease, other fungicides and application measures were evaluated. In all, 20 fungicides in 15 chemical groups and 10 fungicide groups were examined in vitro. In vitro inhibition of the radial growth of the pathogen Raffaelea lauricola was determined on fungicide-amended malt extract agar; demethylation inhibitors (DMIs; fenarimol, myclobutanil, propiconazole, prothioconazole, triadimenol, triadimefon, and triticonazole), quinone outside inhibitors (azoxystrobin, pyraclostrobin, and fluoxastrobin), and a quinone inside inhibitor (fluazinam) had the greatest impact on radial growth (the concentration at which growth was reduced by 50% was ≥0.1 μg ml-1). In greenhouse studies, the most inhibitory products in vitro, plus thiabendazole and two products that were not tested in vitro, flutriafol and a potassium salts mixture of phosphorus acid, were tested for disease suppression on artificially inoculated, potted 'Simmonds,' a susceptible avocado cultivar. In general, soil drench applications of the above DMIs and thiabendazole but not azoxystrobin, pyraclostrobin, fluazinam, or the phosphorus acid salt provided significant control of disease (P < 0.05). Topical branch or trunk applications of propiconazole, and triadimenol in 2% Pentrabark, a bark-penetrating surfactant, were also effective at lower rates than were used in drench applications. Comparable levels of disease suppression were achieved when propiconazole was applied at 11% of the rates that were used in soil drenches. Although topical fungicide applications in bark-penetrating surfactants would be a less expensive practice than macroinfusion, moving sufficient concentrations of propiconazole or other fungicides into host xylem will be difficult in trees that are larger than the potted plants that were tested in these trials. Ongoing work examines means by which this goal might be met on fruit-bearing trees in the field.

Vida útil e qualidade de frutos de tomateiros tratados com paclobutrazol

A aplicação de reguladores de crescimento pode influenciar todas as fases do desenvolvimento de uma planta, incluindo o florescimento, o desenvolvimento e a maturação de frutos e sementes. Assim, avaliaram-se as principais características físicas e químicas e a vida útil dos frutos de tomate obtidos de plantas tratadas com paclobutrazol - PBZ (0, 50 e 100 mg L-1), via rega de mudas, aos 15 dias após a semeadura. Os frutos foram analisados imediatamente após a colheita e aos cinco, 10, 15 e 20 dias de armazenamento, em condições ambientes. A eficiência dos tratamentos e a qualidade dos frutos foram determinadas por meio da perda de matéria fresca, firmeza da polpa, teores de sólidos solúveis (SS), acidez titulável (AT), vitamina C e relação SS/AT. Adotou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 3 x 5 (três concentrações de paclobutrazol x cinco períodos de armazenamento em temperatura ambiente). As aplicações de paclobutrazol em mudas de tomateiro, aos 15 dias após a semeadura, nas concentrações de 50 e 100 mg L-1, não alteraram a vida útil dos frutos do tomate longa vida AF 7631. O aumento das concentrações de PBZ resultou em menor perda de matéria fresca dos frutos e sua menor firmeza e acidez. Os teores de sólidos solúveis e de vitamina C e a relação SS/AT não se alteraram com o aumento das concentrações de PBZ. Os frutos, independentemente das concentrações de PBZ aplicadas às mudas, chegaram aos 20 dias de armazenamento (25 ± 2 ºC e 75 ± 5% UR) em condições para consumo, mesmo tendo perdido significativa quantidade de matéria fresca, acidez e firmeza.

Imazalil residue loading and green mould control in citrus packhouses

Imazalil (IMZ) is commonly applied in South African citrus packhouses for the control of green mould, caused by Penicillium digitatum, yet the disease still causes significant postharvest losses. The maximum residue limit (MRL) for IMZ on citrus fruit is 5 μg g −1, whereas 2–3 μg g −1 is a biologically effective residue level that should at least inhibit green mould sporulation. Standard compliance auditing of residue levels of citrus fruit, however, indicate that fruit from the majority of packhouses have residues of ≈1 μg g −1. Poor disease control from insufficient residue loading might further be compounded by the presence of IMZ-resistant isolates of P. digitatum in packhouses. This study was conducted to assess the current status of IMZ application in South African packhouses, to determine the adequate residue levels needed to control green mould and inhibit its sporulation using both IMZ sensitive and resistant isolates, to investigate IMZ application methods and resultant residue levels in commercial citrus packhouses, and to study optimisation of modes of IMZ application in citrus packhouses. Factors studied were IMZ concentration, application type (spray vs. dip and drench), exposure time, solution temperature and pH, as well as curative and protective control of P. digitatum. The packhouse survey showed that the majority of packhouses applied IMZ in a sulphate salt formulation through a fungicide dip tank, and loaded an IMZ residue of ≈1 μg g −1. In dip applications, IMZ had excellent curative and protective activity against Penicillium isolates sensitive to IMZ. However, curative control of IMZ resistant isolates was substantially reduced and protective control was lost, even at twice the recommended concentration, nor was sporulation inhibited. The use of sodium bicarbonate (2%) buffered imazalil sulphate solutions at pH ±8, compared with pH ±3 of the unbuffered solutions, markedly increased IMZ residue loading on Navel and Valencia oranges and improved curative and protective control of IMZ resistant isolates. Exposure time did not affect IMZ residue loading in IMZ sulphate solutions at pH 3, although the MRL was exceeded after 45 s exposure in pH 8 solutions. Imazalil applied through spray or drench application improved residue loading, but green mould control was less effective than after dip application.

Season-Long Insecticide Efficacy for Hemlock Woolly Adelgid,Adelges tsugae(Hemiptera: Adelgidae), Management in Nurseries

Nursery growers and extension personnel have to rely on efficacy data from forest and landscape systems to manage hemlock woolly adelgid in nurseries. Considerable differences in tree size and culture and application logistics could make such data unsuitable. We evaluated 12 different insecticide formulations for short and long-term control of hemlock woolly adelgid in container grown Eastern hemlocks, Tsuga canadensis. All products provided control of first generation hemlock woolly adelgids, though efficacy of foliar applications of neonicotinoids dinotefuran, imidacloprid (Marathon® II), and acetamiprid and foliar or drench applications of spirotetramat acted the most quickly. Foliar and soil applications of neonicotinoids and spirotetramat also prevented reinfestation of second generation crawlers. In contrast, second generation hemlock woolly adelgids successfully colonized trees treated with the contact insecticides, horticultural oil and bifenthrin. Systemic insecticides provided season-long control of hemlock woolly adelgid when applied to foliage, which is the preferred method of application of nursery growers.

Effectiveness of AG3 phosphonate formulation in suppressing phytophthora blight in cucumber and bell pepper plants under growth room conditions

Phytophthora blight or crown or root rot (Phytophthora capsici Leonian) is an important disease of a wide range of plant species including peppers, tomatoes, cucumbers and other cucurbits in Canada and worldwide. We have previously demonstrated the effectiveness of a new liquid formulation of AG3 phosphonate (Calirus 150, Bromine Compounds Ltd., Beer Sheva, Israel) in suppressing pythium damping-off of cucumbers and clubroot of bok choy and cabbage. In this study, the effectiveness of AG3 phosphonate formulation to suppress phytophthora damping-off and root rot of cucumber (Cucumis sativus L.) seedlings or phytophthora blight of bell pepper (Capsicum annuum L.) plants was determined in a peat-based mix or sandy-loam soil artificially infested with soil inoculum of P. capsici under growth room conditions. In an infested peat-based mix, AG3 phosphonate preplanting amendment or postplanting drench treatments (0.05%, 0.1% and 0.2% a.i.) and a 10-min seed-soak treatment (10.45% a.i.) significantly increased the percentage of healthy cucumber seedlings and reduced damping-off and root rot severity. The seed-soak and 0.2% treatments were the most effective treatments that consistently suppressed damping-off and root rot of cucumber even in a peat-based mix infested with high inoculum levels of P. capsici. Disease severity on cucumber plants was also significantly less in the AG3 phosphonate treatments. The single drench applications of AG3 phosphonate (0.05%, 0.1% and 0.2% a.i.) significantly reduced the incidence and severity of phytophthora blight of bell pepper plants in an infested peat-based mix or a sandy-loam soil compared with the control plants receiving no treatment. The best control of phytophthora blight of bell pepper was achieved with the higher rate (0.2% a.i.) in both peat-based mix and soil with 90% of the plants remaining healthy compared with none in the control. The disease protection increased with increasing concentrations of AG3 phosphonate in both bell peppers and cucumbers without any phytotoxicity.

Benzyladenine and Gibberellic Acid Application Prevents Abscisic Acid-induced Leaf Chlorosis in Pansy and Viola

Drought stress during the shipping and retailing of floriculture crops can reduce postproduction shelf life and marketability. The plant hormone abscisic acid (ABA) mediates drought stress responses by closing stomata and reducing water loss. Applications of exogenous s-ABA effectively reduce water loss and allow a variety of species to survive temporary periods of drought stress. Unfortunately, s-ABA application can also lead to leaf chlorosis, which reduces the overall quality of economically important bedding plant species, including Viola ×wittrockiana (pansy). The goal of this research was to determine how to prevent s-ABA-induced leaf chlorosis in pansy and a closely related species, Viola cornuta (viola). All concentrations of both spray (250 or 500 mg·L−1) and drench (125 or 250 mg·L−1) s-ABA applications induced leaf yellowing. Young plants at the plug stage and 11-cm finished plants with one to two open flowers were further evaluated to determine if the developmental stage of the plants influenced s-ABA effectiveness or the development of negative side effects. Both plugs and finished pansies and violas developed leaf chlorosis after s-ABA applications, but symptoms were generally more severe in finished plants. The individual application of benzyladenine (BA), gibberellic acid (GA4+7), or the ethylene perception inhibitor, 1-methylcyclopropene, before s-ABA application had no effect on the development of s-ABA-induced leaf chlorosis. However, applications of 5 or 10 mg·L−1 BA and GA4+7 as a mixture (BA + GA4+7) before a drench or spray application of s-ABA prevented leaf chlorosis. The application of s-ABA and BA + GA4+7 would allow floriculture crops to tolerate temporary periods of drought stress without any loss of postproduction quality.

EPIDEMIOLOGY AND CONTROL OF SOME DISEASES AFFECTING PROTEACEAE CROPS IN CHILE

Since the introduction of Proteaceae crops in Chile, there have been at least seven diseases described caused by fungi (Phytophthora, Fusarium, Alternaria, Botrytis, and Cladosporium) and bacteria (Pseudomonas and Xanthomonas). Additionally, some wood-associated pathogens such as Botryosphaeria, Phoma and Phomopsis have also been described. Due to important losses associated with these diseases, both chemical and biological control alternatives were evaluated for some of the above pathogens. Field and greenhouse experiments were conducted over different seasons. Trichoderma harzianum as a drench application resulted in an effective preventive control of Fusarium, with incidence and severity levels similar to the fungicide Benomyl. On the other hand, epidemiological studies indicated that the pathogen inoculum remained both in the soil and in weeds (Daucus carota and Rumex acetosella). According to field experiments, Trichoderma virens appears to be a good control alternative for Cladosporium and Alternaria. Trichoderma parceanamosum sprayed over the plants proved to be the most effective control treatment for Botrytis cinerea. Finally, cupric fungicides and Bacillus subtilis isolates did not provide an effective control against Pseudomonas in field conditions. New experiments should be conducted to obtain more conclusive results.

Effect of Silicon-Based Fertilizer Applications on the Reproduction and Development of the Citrus Mealybug (Hemiptera: Pseudococcidae) Feeding on Green Coleus

Mealybugs are major insect pests of greenhouses, interiorscapes, and conservatories because they feed on a wide-range of horticultural crops. Furthermore, mealybugs are difficult to regulate with insecticides due to the presence of a nearly impervious protective waxy covering, which means that alternative management strategies are required. As such, this study, involving two replicated experiments, was designed to determine the value of applying silicon-based fertilizers, as potassium silicate, to coleus, Solenstemon scutellarioides (L.) Codd, plants as a way to prevent outbreaks of the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae). The first experiment evaluated the effects of different application methods (foliar and drench), at 50 ppm silicon, using the commercially-available product, ProTek 0-0-3 The Silicon Solution. The second experiment entailed applying the silicon-based fertilizer as a drench to the growing medium at different rates (0, 100, 400, 800, and 1,600 ppm silicon). We determined the effects of the silicon-based fertilizer treatments on citrus mealybug life history parameters including number of eggs laid by the adult female, body size, and developmental time from first instar to ovipositing adult female. Furthermore, we used a plant alkaline fusion technique to assess the concentration (milligrams per kilogram or ppm) of silicon in the coleus plant tissues at variable time intervals (days). In general, this technique involved dry-ashing plant tissue in a muffle furnace, followed by alkaline fusion and then colormetric analysis. The silicon-based fertilizer application treatments, in both experiments, did not negatively affect any of the citrus mealybug life history parameters measured. In the first experiment, citrus mealybug female egg load ranged from 199.5 (drench application) to 219.4 (combination spray and drench application), and developmental time (days) from first instar crawler to ovipositing female ranged from 34.2 (combination spray and drench application) to 35.7 (drench application). For the second experiment, citrus mealybug female egg load ranged from 223.1 (1,600 ppm silicon) to 249.2 (800 ppm silicon). Developmental time from first-instar crawler to ovipositing female ranged from 35.0 (400 ppm silicon) to 36.6 (800 ppm silicon). Our results indicate that coleus is a silicon "rejector," and as such, applications of silicon-based fertilizers may not benefit dicot plants such as coleus as much as monocot plants in regards to avoiding insect pest outbreaks because dicots tend not to accumulate sufficient quantities of silicon.

Drench Application of Cyclanilide Promotes Shoot Development in Containerized Woody Landscape Species during Nursery Production

Abstract Cyclanilide (CYC), a plant growth regulator with cytokinin-like properties, was applied as a substrate drench to containerized woody ornamentals to determine its effects on plant growth. At 70 days after treatment (DAT) in 2005, drench applications of 50 to 1,000 ppm CYC had increased shoot development 7 to 74% for ‘Alabama Beauty’ sasanqua camellia (Camellia sasanqua ‘Alabama Beauty’), 63 to 205% for small anisetree (Illicium parviflorum), 21 to 74% for ‘Snow White’ Indian hawthorn (Rhaphiolepis indica ‘Snow White’), and 266 to 626% for ‘Sky Pencil’ holly (Ilex crenata ‘Sky Pencil’), when compared to control plants. Shoot counts the following spring, 270 DAT, increased from 16 to 101% for sasanqua camellia, 42 to 158% for small anisetree, 121 to 241% for Indian hawthorn, and 33 to 167% for ‘Firepower’ nandina, when compared to control plants. At 30 DAT foliar injury to sasanqua camellia, Indian hawthorn, and small anisetree increased with CYC concentration, and application of 500 or 1,000 ppm CYC resulted in severe injury or death of small anisetree and ‘Snow White’ Indian hawthorn. At 75 DAT in 2006, drench application of 25 to 100 ppm CYC had increased shoot counts of Eleanor Taber™ Indian hawthorn from 100 to 218%, when compared to controls, and quality ratings were highest at 130 DAT in plants drenched with 50 ppm CYC, although foliar injury ratings increased with CYC concentration at 75 and 130 DAT. At 60 DAT in 2007, application of 10 to 40 ppm CYC had increased shoot counts for ‘Snow White’ Indian hawthorn and ‘Sky Pencil’ holly 100 to 182% and 22 to 78%, respectively, and 96 to 171% and 30 to 63%, respectively at 90 to 110 DAT. In both species, quality ratings at 160 DAT increased with increasing CYC concentration. Single CYC drench applications were more persistent than previously reported single spray applications, effective at lower concentrations, and promoted shoot production in a species not responsive to single or multiple spray applications (Nandina domestica).

Economic management of anthelmintic resistance: model and application*

The increasing prevalence of anthelmintic (drench) resistance in gastrointestinal parasite populations is decreasing the profitability of the Australian sheep industry. Refugia management can delay its development by not exposing a proportion of the worm population to chemical control. A dynamic‐optimisation model is used to assess the economic value of refugia for management of the worm species Teladorsagia circumcincta and macrocyclic lactone drenches in an application to Western Australian sheep flocks. A low rate of refugia (2 per cent) is most profitable under standard circumstances because it slows the development of resistance, but also reduces the proportion of the flock not exposed to chemical control. Frequent drench application should remain the primary method of control. However, its efficacy should be preserved through refugia management, rather than greatly reducing treatment frequency.

Distribution in plant, substrate and leachate of paclobutrazol following application to containerized Nerium oleander L. seedlings

Paclobutrazol (PBZ) is a retardant often used in potted ornamental plants to control their growth and compactness. The distribution in plant, substrate and leachate of PBZ applied to containerized oleander seedlings were studied after a single liquid drench application to the substrate surface (20 mg a.i. per plant) in a nursery dedicated to pot production in SE Spain. PBZ significantly reduced all growth parameters, providing more compact plants of good commercial value and confirming its ability to reduce the vertical growth of native oleander in the nursery. The level of PBZ residues in leaves was higher at the end of pot cultivation (156 days post PBZ application) than at the first sampling time (30 days after PBZ application), whereas the level in stems decreased for the same period of time. PBZ residues in roots remained constant during the experimental period. The high level of PBZ residues detected in the substrate 30 days after application had decreased significantly (by 67%) by the end of the experiment. A greater leaching fraction was detected for PBZ-treated seedlings and so a greater amount of PBZ was leached into the nursery soil with the irrigation water at the end of the experiment. This greater amount of PBZ leached into the soil represents an important way of contamination in the nursery and a substantial risk to the environment.

Desenvolvimento de equipamento motorizado para aplicação líquida de produtos fitossanitários na cultura do café

O trabalho teve como objetivo desenvolver um protótipo aplicador de líquidos na superfície do solo para cafezais localizados em regiões de topografia acidentada ou cultivados em sistema de plantio adensado. O protótipo do aplicador construído é um trator de rabiças acionado por um motor de dois tempos a gasolina, de 2,61 kW (3,5 cv), com duas rodas motrizes com bitola de 0,60 m e uma terceira roda direcional, equipado com sistema de pulverização dotado de depósito de 40 L, bomba centrífuga, filtros de linha, regulador de pressão, manômetro, mangueiras, válvulas e suporte de bicos. Para avaliar a eficiência do protótipo, foram instalados dois experimentos de campo em São Sebastião do Paraíso - MG (2003 e 2004), onde foram aplicados inseticidas sistêmicos para o controle da cigarra. Os métodos de aplicação avaliados foram: aplicação em faixa, filete, "drench" contínuo e "drench" intermitente. O protótipo aplicador de líquidos à superfície do solo atendeu aos objetivos propostos, visto que conseguiu realizar o controle químico de cigarras com destaque para a aplicação em "drench" contínuo. O protótipo, se equipado para aplicar simultaneamente nos dois lados da planta, apresentará capacidade de campo operacional semelhante à do equipamento tratorizado.

Management of the Spread of Tomato spotted wilt virus in Tobacco Crops with Insecticides Based on Estimates of Thrips Infestation and Virus Incidence.

Tomato spotted wilt virus (TSWV) causes serious losses in the tobacco-producing areas of northern Greece. Following a destructive epidemic of TSWV in the prefecture of Kilkis in 2003, a coordinated disease management scheme was developed in collaboration with the local tobacco farmers' associations on 1,000 ha in 2004 and 500 ha in 2005 of tobacco crops of the cv. Virginia. Insecticides first were evaluated for efficiency to control Thrips tabaci, the only TSWV vector present in tobacco crops in Greece. Field data on T. tabaci infestation, population fluctuation, and TSWV incidence were used to coordinate insecticide applications. T. tabaci overwinters in the soil covered by wild flora close to infested fields. The first adults of each season were recorded on blue sticky traps in week 13 and viruliferous individuals were found on weeds close to the tobacco fields in week 16 of both years. Tobacco seedlings were protected against thrips by a preventive drench application of carbofuran to soil in seedling beds, followed by two methomyl and one malathion foliage applications. To achieve an effective decrease of primary inoculum in the fields, malathion was applied to weeds on the field borders before transplanting the tobacco seedlings. In the tobacco crops, carbofuran was applied directly after transplanting. Early transplanted (week 19 to 20) seedlings were sprayed with methomyl. Subsequently, two rounds of foliar applications were started in week 23, consisting of cypermethrin, followed by malathion and methomyl, followed by one or two malathion sprays. At transplanting (week 19 to 23 or 22 in 2004 or 2005, respectively), 340 ± 160 (mean + standard deviation, n = 4 weeks) and 230 ± 130 (n = 3) T. tabaci individuals per trap were recorded in 2004 and 2005, respectively, and 52% of the thrips trapped in the neighboring flora in 2004 were TSWV infected. Afterwards, T. tabaci populations did not increase significantly until harvest (up to 350 individuals were counted per trap). In a control field of an oriental tobacco cultivar in which no insecticides were applied, up to 5,000 and 3,300 thrips were found per trap in 2004 and 2005, respectively. The final incidence of tobacco plants with TSWV infection fluctuated from 10 to 20% in the Virginia tobacco crops whereas, in the control crop, it was 60 and 85% in 2004 and 2005, respectively. This study showed that a well-coordinated collective plan based on data on infection pressure by TSWV and the vector population fluctuation during the growing season can represent an effective way of combating epidemics in tobacco.

Effects of a novel microsporidium on the black vine weevil, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae)

A newly discovered microsporidium infecting the black vine weevil, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae), provisionally placed in the genus Canningia, was studied to determine its impact on O. sulcatus. O. sulcatus populations from several locations were sampled and evaluated for microsporidiosis. A very low prevalence of the disease was observed in all locations surveyed (<3.0%). Laboratory studies were conducted by orally exposing both larvae and adults of O. sulcatus to varying concentrations of Canningia sp . spores. Larval bioassays at a variety of dosages (0, 10, etc.) were performed to evaluate pathogen infectivity, larval survival and growth. Adult bioassays (dosages: 0, 10, etc.) were performed to evaluate longevity, fecundity and mechanisms of vertical pathogen transmission. Larvae and adults were infected in all spore treatments. Larval growth was significantly reduced at dosages above 10 spores/larva. Adults infected at all dosages experienced high levels of mortality and fecundity was reduced to zero. Greenhouse trials were performed to determine if larvae feeding in soil acquired infections when spores were topically applied as a drench application (0, 10 5, 10 6, 10 7 spores/pot). Established larvae feeding on plant roots in pots developed infections when exposed to drench treatments of 10 6 and 10 7 spores/pot after 14–21 days. Canningia sp. is an acute pathogen of O. sulcatus infective to both larvae and adults. Topically applied spores also infected larvae feeding on roots in soilless potting media, suggesting the possibility of using this pathogen in a microbial control program.

Optimizing Efficacy of New Postharvest Fungicides and Evaluation of Sanitizing Agents for Managing Citrus Green Mold.

Three new fungicides, azoxystrobin, fludioxonil, and pyrimethanil, that belong to different chemical classes are highly effective in managing citrus green mold and are being registered for postharvest use in the United States. Recirculating in-line drenches provided a significantly improved efficacy compared with standard low-volume spray applications. To prevent pathogen contamination of drench solutions, two oxidizing disinfectants, sodium hypochlorite and hydrogen peroxide/peroxyacetic acid (HPPA) solutions, were evaluated. Inhibition of conidial germination of Penicillium digitatum was dependent on the pH of the solution and the exposure time for each sanitizing agent. Chlorine (50 mg/liter) and HPPA (2,700 mg/liter) effectively inhibited germination in 40- and 240-s exposures, respectively, at pH 7. All fungicides tested were compatible and effective with HPPA, whereas fludioxonil, azoxystrobin, and thiabendazole, but not imazalil and pyrimethanil, were compatible with chlorine. In laboratory studies, sodium bicarbonate (SBC, 3%) significantly increased the efficacy of the three fungicides (250 mg/liter) and had no adverse effect on their stability in aqueous solutions. Fludioxonil (300 mg/liter)-SBC mixtures were still highly effective when applied 24 h after fruit inoculation. In experimental packingline studies, SBC or SBC-chlorine improved the efficacy of fludioxonil, whereas azoxystrobin was effective with and without these additives. Heating of drench solutions of fludioxonil (300 mg/liter) to 50°C did not improve decay control. In conclusion, in-line recirculating drench applications and fungicide-sanitizer-SBC mixtures significantly increased fungicide efficacy and provide an integrated approach for optimizing fungicide efficacy. These strategies also should minimize the selection for resistant isolates of the pathogen.

Evaluation of Chemical Agents for the Control of Phytophthora ramorum and Other Species of Phytophthora on Nursery Crops

Phytophthora diseases occur frequently in nurseries, and the recent incidence of ramorum blight, caused by P. ramorum, on nursery crops has underscored the need for improved management strategies against all Phytophthora diseases. We evaluated several chemicals that target Oomycete pathogens, inoculating detached rhododendron or lilac leaves removed from plants previously treated with various chemicals, or chemically-treated leaves on intact plants. Results indicated that Subdue MAXX (drench or foliar application) was the most effective chemical in suppressing infections caused by all species of Phytophthora tested (P. ramorum, P. citricola, P. citrophthora, and P. nicotianae) except P. citrophthora; with P. ramorum, it was active for at least 6 weeks after spray application. More chemicals were effective when sporangial rather than mycelial plug inoculum of P. ramorum was used, including Aliette, Ranman, Stature DM, and Fenamidone. All chemicals tested were fungistatic, not fungicidal. These tests indicate that several materials inhibit infection by Phytophthora species, and that the detached leaf test is effective in evaluating efficacy of chemical agents for the suppression of Phytophthora pathogens from nurseries. Accepted for publication 10 November 2007. Published 11 February 2008.

Management of Phytophthora Crown Rot in Pumpkin and Zucchini Seedlings with Phosphonates.

Experiments were conducted in the greenhouse to determine the efficacy of two phosphonate-containing fungicides (FNX-100 and FNX-2500) against Phytophthora crown rot of pumpkin. The experiments were designed to determine the effects of crop cultivar, application method (soil drench versus foliar spray), and phosphonate concentration on the level of effectiveness of a crown rot management strategy using phosphonates. Pumpkin cultivar, treatment (type of fungicide product), phosphonate concentration, and application method significantly influenced the level of Phytophthora crown rot control. Between the two fungicides, only FNX-100 suppressed Phytophthora crown rot in pumpkin. For cv. Phantom, the highest level of control was achieved with the drench application of 3.0% FNX-100 whereas, for cv. Spooktacular, all three concentrations of FNX-100 (1.0, 2.0, and 3.0%, vol/vol) applied as a soil drench suppressed or significantly reduced the severity of crown rot. Additional experiments using zucchini as test plants demonstrated that, at the concentrations tested, FNX-100 was more efficacious than FNX-2500 in controlling Phytophthora crown rot and that zucchini cultivar or FNX-100 concentration did not significantly influence crown rot control with phosphonates. In this study, FNX-100, which is not currently labeled for use in vegetables, provided satisfactory disease control in both pumpkin and zucchini whereas FNX-2500, a foliar fungicide comprised of the phosphate/phosphonates and copper, manganese, and zinc, did not significantly affect disease severity. This study, albeit limited in scope, showed that cultivar selection may play an important role in the successful management of Phytophthora crown rot on cucurbits with phosphonates, information which may be useful in designing additional tests and developing management strategies for pumpkin and zucchini that are grown in the field.

Comparison of Standard (Granular and Drench) and Novel (Tablet, Stick Soak, and Root Dip) Imidacloprid Treatments for Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) Management on Hybrid Poplar

Standard soil application methods (granular and drench) were compared with novel methods (tablet, stick soak, and root dip) for efficacy and duration in hybrid poplar (Populus spp.) against adult and larval cottonwood leaf beetle, Chrysomela scripta F. (Coleoptera: Chrysomelidae). Beetle feeding can kill saplings and significantly damage trees by reducing tree height, diameter, and biomass. Tablets offer lower risk to applicators and beneficial insects, because insecticides do not need to be measured and sprayed. In field- and container-grown plants, standard granular and drench application methods had similar efficacy and duration compared with tablets. In field-grown plants, adult and larval survivorship was reduced for 12 mo with the two highest rates of tablet (0.25 x and 0.5 x) treatments, and in container-grown plants, with all rates of tablet (0.25 x, 0.5 x, and 1 x ) treatments that were used. Two other novel application methods, stick soak and root dip, offer new methods for protecting vulnerable transplants in nursery propagation. In container-grown plants, adult survivorship was reduced for 8 mo and larval survivorship for 12 mo for all rates of stick soak (0.5 x, 1 x, and 2 x) and all rates of root dip (1 x, 2 x, and 4 x) treatments. Literature searches revealed little data on the efficacy and duration of soil-applied imidacloprid for trees, even though it is the primary insecticide used for defoliators and some borers in landscape and in nurseries for field and container production.

Efficacy of Metarhizium anisopliae as a Curative Application for Black Vine Weevil (Otiorhynchus sulcatus) Infesting Container-Grown Nursery Crops

Abstract The black vine weevil (BVW), Otiorhynchus sulcatus (F.) is a serious pest of nursery crops. The fungus, Metarhizium anisopliae (F52), is registered by the U.S. Environmental Protection Agency for BVW control. The objectives of this study were to determine the efficacy of a curative drench application of M. anisopliae for controlling BVW larval infestations in container-grown nursery plants and the effect of temperature on the rate of fungal growth and speed of kill. Trials evaluating the efficacy of M. anisopliae as a curative application were performed in the spring of 2004 and 2005 as well as the fall of 2006. Laboratory studies were performed to quantify the impact of temperature (10, 15, 20, 24 and 28C) on fungal growth and speed of kill. Metarhizium anisopliae applied in the greenhouse and outdoors in 2004 were 92 and 30% effective, respectively. Fungal applications to container-grown plant material maintained outdoors in the spring of 2005 were nearly 100% effective 28 days after application. Fall applications in 2006 provided statistically significant reductions in the number of live BVW larve per pot, but were not as effective as spring applications in 2005. The mean media temperature of containers maintained outdoors in the fall of 2006 dropped considerably (10–12C) over the course of the experiment and were likely the cause for the reduced efficacy. Laboratory experiments demonstrated that temperatures below 20C (68F) significantly slowed fungal growth and the speed at which M. anisopliae infected BVW larvae. In the field, drench applications of M. anisopliae were very effective at eliminating BVW larvae in container-grown nursery plants when media temperatures were adequate (&amp;gt; 15C (59F)). The use of M. anisopliae as a curative drench application has similar temperature-dependent limitations as the use of entomopathogenic nematodes for BVW control. Therefore, applications should occur as early in the fall as possible once egg laying has ended or in late spring just prior to pupation when media temperatures would be most conducive to fungal infection.