Drench Treatment Research Articles

Evaluation of Systemic Insecticides for Potato Leafhopper Control in Field-Grown Red Maple

Abstract Systemic insecticides and application methods were evaluated in two trials that began in 2005 and 2006 for control of potato leafhopper (Empoasca fabae [Harris]) on four red maple (Acer rubrum L.) cultivars and rated annually through 2007. Treatments evaluated in this study included surface drenches of imidacloprid plus cyfluthrin (Discus) or imidacloprid plus bifenthrin (Allectus SC), clothianidin (Arena 50WDG), dinotefuran (Safari 20SG), or thiamethoxam (Flagship 25WG); soil inserted treatments of imidacloprid formulated as an experimental tablet or as an experimental gel; or a plant root dip of Discus + Terra-Sorb hydrogel. In the 2005 trial, a one-time drench of Discus or two imidacloprid tablets significantly reduced leafhopper damage to red maple for a 3-year period. In the 2006 trial, a one-time drench of Allectus, Discus, Arena, Flagship, and Safari significantly reduced leafhopper damage for 2 years. In most cases, the Discus drench and root dip treatments were initially more effective than the imidacloprid tablets or the gel treatment. However, in general, the efficacy of imidacloprid tablet or gel treatments increased in subsequent years. Two imidacloprid tablets were more effective than one. Likewise, higher imidacloprid drench rates were more effective than lower rates. Most insecticide treatments significantly increased red maple trunk diameter, although this effect varied with cultivar and time. Allectus and Discus drench treatments significantly increased the branch and internode length of ‘Franksred’ maple in the 2005 trial. Results of this study indicate long-term potato leafhopper control with systemic insecticides and enhanced growth in red maple.

Community Response of Insects Associated with Eastern Hemlock to Imidacloprid and Horticultural Oil Treatments

The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive species reducing the populations of eastern hemlock, Tsuga canadensis L. Carrière, throughout the eastern United States. Systemic imidacloprid and horticultural oil are the primary chemicals used to control infestations of this invasive pest; however, the impact of these two chemicals on nontarget canopy insects is unknown. This study was initiated in November 2005 to assess the effects of (1) imidacloprid soil drench, (2) imidacloprid soil injection, (3) imidacloprid tree injections, and (4) horticultural oil applications on multiple levels of organization (composition, overall specimen abundance and species richness, guild specimen abundance and species richness, and individual species) within the phytophagous and transient canopy insect community. Community composition differed significantly among treatments based on analysis of similarity. Mean species richness and specimen abundance were significantly reduced by one or more treatments. Soil drench applications significantly reduced species richness for the detritivore and phytophaga guilds. Furthermore, specimen abundance for species in the detritivore, fungivore, phytophaga, scavenger, and transient phytophaga guilds was significantly lower in the soil drench treatment. This trend was consistent in all insect guilds examined, with the exception of the hematophaga guild that was not significantly lower than for species on the control trees. Of the 293 species documented to be associated with eastern hemlocks, 33 species were found to be directly effected by one or more of the chemical treatments.

Drench Treatments for Management of Larval Japanese Beetle (Coleoptera: Scarabaeidae) in Field-Grown Balled and Burlapped Nursery Plants

Insecticide drenches were applied to postharvest field-grown nursery plants harvested as 60-cm-diameter balled and burlapped (B&B) root balls for controlling third instars of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Bifenthrin, chlorpyrifos, lambda-cyhalothrin, and thiamethoxam were drench-applied in fall and spring tests at volumes of runoff (1×; ≈2.57 liters per drench per root ball) or twice runoff (2×). Tests also examined consecutive drenches (two, four, or six) and B&B rotation between drenches. Fall-applied drenches did not meet the Domestic Japanese Beetle Harmonization Plan (DJHP) standards of ≤1 grub and ranged from 0 to 90% control. However, most fall-applied drenches significantly reduced grub numbers relative to the untreated root balls. Spring-applied drenches were more effective than fall drenches: chlorpyrifos treatments gave 94–100% control, whereas other spring-applied treatments were less consistent, including thiamethoxam (83–100% control) and bifenthrin (61–100% control). Lambda-cyhalothrin was not effective. A higher drench volume (2×) did not significantly improve treatment efficacy; however, grub numbers decreased as the number of drenches increased for fall-applied chlorpyrifos and thiamethoxam and spring-applied bifenthrin. Rotation of root balls significantly reduced grub numbers compared with nonrotated treatments for fall-applied chlorpyrifos (six drenches) and bifenthrin (two or six drenches), but these treatments did not meet DJHP standards. The study indicates chlorpyrifos, bifenthrin, and thiamethoxam drenches can control Japanese beetle in the spring and may provide a new postharvest option to certify B&B plants for Japanese beetle.

Drench Treatments for Management of Larval Japanese Beetle (Coleoptera: Scarabaeidae) in Field-Grown Balled and Burlapped Nursery Plants

Insecticide drenches were applied to postharvest field-grown nursery plants harvested as 60-cm-diameter balled and burlapped (B&B) root balls for controlling third instars of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Bifenthrin, chlorpyrifos, lambda-cyhalothrin, and thiamethoxam were drench-applied in fall and spring tests at volumes of runoff (1X; approximately equal 2.57 liters per drench per root ball) or twice runoff (2X). Tests also examined consecutive drenches (two, four, or six) and B&B rotation between drenches. Fall-applied drenches did not meet the Domestic Japanese Beetle Harmonization Plan (DJHP) standards of < or =1 grub and ranged from 0 to 90% control. However, most fall-applied drenches significantly reduced grub numbers relative to the untreated root balls. Spring-applied drenches were more effective than fall drenches: chlorpyrifos treatments gave 94-100% control, whereas other spring-applied treatments were less consistent, including thiamethoxam (83-100% control) and bifenthrin (61-100% control). Lambda-cyhalothrin was not effective. A higher drench volume (2X) did not significantly improve treatment efficacy; however, grub numbers decreased as the number of drenches increased for fall-applied chlorpyrifos and thiamethoxam and spring-applied bifenthrin. Rotation of root balls significantly reduced grub numbers compared with nonrotated treatments for fall-applied chlorpyrifos (six drenches) and bifenthrin (two or six drenches), but these treatments did not meet DJHP standards. The study indicates chlorpyrifos, bifenthrin, and thiamethoxam drenches can control Japanese beetle in the spring and may provide a new postharvest option to certify B&B plants for Japanese beetle.

Biological control of Phytophthora blight of pepper by antagonistic rhizobacteria selected from a sequential screening procedure

This study was conducted to select antagonistic rhizobacteria against Phytophthora capsici using a sequential screening procedure and to evaluate control efficacy of drench or root-dip treatments with the selected strains against Phytophthora blight of pepper in the field. Out of 439 bacterial strains, 16 potentially antagonistic strains were screened through radicle and seedling assays and in planta trials, and five candidate strains, CCR04, CCR80, GSE09, ISE13, and ISE14, were selected for field tests. In 2005 and 2006 tests, the control efficacy of the five strains was examined against Phytophthora blight of pepper plants drenched with the bacterial suspension in artificial pathogen inoculation. Three strains, CCR04, CCR80, and ISE14, consistently reduced the disease in both tests. As another form of application, the control efficacy of root-dip treatment was examined on pepper plants just prior to transplanting in the field with natural inoculation in 2006 and 2007. In these tests, four strains, CCR04, CCR80, GSE09, and ISE14, showed consistently good control efficacy against P. capsici, and strains CCR80 and ISE14 increased pepper fruit yield. The strain-treated roots had less infection rates by P. capsici compared with control roots regardless of drench or root-dip treatments. In addition, the strains did not affect the populations of bacteria and fungi in the rhizosphere soil. Therefore, the antagonistic strains selected from the screening procedure provided significant protection against P. capsici through pepper root colonization. These strains could be applied by either drench or root-dip treatment as alternatives to agricultural chemicals to control Phytophthora blight of pepper.

Efficiency of thiamethoxam for coffee leaf-miner control. I - Influence of the mode of application

The coffee leaf-miner Leucoptera coffeella (Guerin-Meneville, 1842) (Lepidoptera: Lyonetiidae) is the most important insect pest of coffee ( Coffea arabica L.) in Brazil, where reductions in the production can reach 70 %. Its control using granular formulations of systemic insecticides, which are soil-applied in the rainy season, has shown to be erratic over the last years, attributed to the irregular distribution of rainfall. As water-dispersible granules (WG) formulations of insecticides can be applied in different forms and are less dependent on the soil moisture, this work was carried out to assess the influence of the mode of application of thiamethoxam WG for the control of coffee leaf-miner in the cerrado region of Minas Gerais State. The experiment consisted of eight treatments and four replicates, in a randomized blocks statistical design. The treatments were: thiamethoxam 250 WG (applied as drench at the plant base, drench in soil furrows and drip irrigation), imidacloprid 700 WG (drench at the plant base and as drip irrigation), thiamethoxam 10 GR and aldicarb 150 GR (in soil furrows), and control. Application was performed in February, with monthly evaluations on pest control until July. Drench treatments at plant base as well as drip irrigation with thiamethoxam 250 WG provided high control efficiency for about 130 days. The thiamethoxam concentrations in the leaves from these treatments were higher than in leaves from other treatments with other modes of application of the insecticide.

Management of gastrointestinal nematode parasites on sheep farms in New Zealand

AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand. METHODS: An interview-based cross-sectional study of grazing management and anthelmintic useage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand. RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased. CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.

Selective and on-demand drenching of lambs: Impact on parasite populations and performance of lambs

AIM: To determine whether drenching regimes for lambs by which a proportion (10%) of the heaviest animals was selectively left untreated, or animals are only drenched ‘on demand’ when faecal nematode egg counts (FEC) exceeded a threshold level, would result in measurable increases in parasite larval challenge in the autumn and/or decreases in the performance of lambs. METHODS: A replicated study compared three drenching strategies in which mobs of lambs (n=360 in total) received either: a five-drench preventive programme, administered to all animals (Treatment 1); a five-drench preventive programme, but the 10% heaviest animals left untreated each time (Treatment 2); or drench treatments administered only when FEC exceeded 500 eggs per gram of faeces (epg) (Treatment 3). After the five-drench programme, animals in Treatments 1 and 2 were treated according to FEC as for Treatment 3. A triple-combination drench containing ivermectin, oxfendazole and levamisole, administered orally, was used for all treatments. There were nine farmlets, allowing three replicates of each treatment, in a completely randomised design. Parasite infestations on pasture were measured in autumn by pasture plucks, and worm burdens were monitored in tracer lambs, while the performance of lambs was assessed by liveweight gains, fleece weights, and body condition and dag scores. RESULTS: Increased numbers of Haemonchus contortus and Trichostrongylus colubriformis larvae on pasture were found in the autumn on farmlets treating selectively or on-demand (Treatments 2 and 3). No differences were detected in other parasite species. Mean liveweight gains did not differ between treatments but some differences were detected between drenched and undrenched lambs in Treatment 2. Mean body condition and mean dag scores of lambs in Treatment 3 tended to be lower and higher, respectively, than those of lambs in Treatment 1; Treatment 2 was generally intermediate. CONCLUSIONS: Drenching strategies for lambs designed to slow the development of anthelmintic resistance, by increasing the pool of susceptible worms available to dilute resistant survivors after treatment, resulted in increased numbers of H. contortus and T. colubriformis but not other species of parasite on pasture. The increased parasite challenge to lambs in the autumn was associated with small production losses, which may be acceptable to farmers wishing to implement such strategies. It is clear that further work is required on the interaction between management practices and the population dynamics of parasites, especially with regard to creating pools of susceptible genotypes to slow the development of drench resistance.

Effect of Fungicides and Storage Conditions on Postharvest Development of Citrus Black Spot and Survival of Guignardia citricarpa in Fruit Tissues.

Citrus black spot (CBS) is caused by Guignardia citricarpa, which incites lesions on citrus fruit and can induce fruit drop. Quiescent infections occur during the spring and summer, and symptoms appear at fruit maturity or after harvest. Thus, fruit from citrus areas affected by CBS represent a risk for introduction of this pathogen into new areas. The effects of preventive field fungicide programs, postharvest fungicide drenches, packinghouse fungicide applications, and storage temperatures on postharvest symptom development and viability of G. citricarpa in lesions were evaluated in five experiments on Murcott tangor, Valencia oranges, and lemons. Preventive field treatments and fruit storage at 8°C consistently reduced postharvest CBS development, whereas a postharvest fungicide drench or packinghouse treatment with fungicides had no effect on postharvest symptom development. In a separate experiment, postharvest appearance of symptoms was related to the percentage of fruit with symptoms at harvest. The preventive field fungicide program also consistently reduced the percentage of isolation of G. citricarpa from affected fruit, whereas storage temperature and packinghouse fungicide treatment gave variable results. The viability of the fungus declined with storage time of fruit after harvest, but G. citricarpa could still be readily isolated regardless of treatment. In another experiment, the viability of the fungus in detached fruit or peel was minimally affected by temperature or moisture during storage. The frequency of successful isolation declined with time, but G. citricarpa was still recovered frequently from symptomatic tissue at later times. The most effective means to reduce postharvest development of symptoms is through preventive application of fungicides during the fruit growing season and storage of harvested fruit at cold temperatures. None of the measures evaluated substantially reduced viability of G. citricarpa, and the pathogen would likely be introduced on symptomatic fruit from citrus areas with CBS.

Interactions of Paecilomyces lilacinus strain 251 with the mycorrhizal fungus Glomus intraradices: Implications for Meloidogyne incognita control on tomato

The interactions of Paecilomyces lilacinus strain 251 with the arbuscular mycorrhizal fungus Glomus intraradices and their significance for the control of Meloidogyne incognita on tomato were investigated in greenhouse experiments. Application of P. lilacinus had no effect on the frequency and intensity of tomato root colonization by G. intraradices. Likewise, the decline of the nematophagous fungus densities after single application in soil was not affected by the presence of the mycorrhizal fungus. Single application of P. lilacinus, as pre-planting soil treatment, resulted in significant reduction of nematode damage. In contrast, mycorrhizal inoculation did not provide sufficient biocontrol. Combined application of the two agents did not enhance root protection compared to single treatments. Double treatment of mycorrhized seedlings with P. lilacinus, as seedling drench and pre-planting soil treatment, 4 and 1 week before transplanting, respectively, resulted in the highest reduction of the nematode damage. These results indicate the potential of the commercial P. lilacinus strain 251 and mycorrhiza for integration in nematode control strategies.

Incidence of Thrips and Tomato Spotted Wilt &lt;I&gt;Tospovirus&lt;/I&gt; in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations

The relative impacts of early season thrips exclusion (cages) and thrips suppression (pesticides) on tomato spotted wilt (family Bunyaviridae, genus Tospovirus, TSW) Tospovirus infection in flue-cured tobacco, Nicotiana tobaccum L., were examined in field trials in 2001-2004. There were fewer TSW symptomatic plants when plants were covered by exclusion cages for 6 wk than when they were uncaged or caged for 2 or 4 wk after transplanting. Plant height, leaves per plant, and total leaf weight per plant were lower in TSW symptomatic plants compared with nonsymptomatic plants for the uncaged plus 2- and 4-wk caged duration treatments but not different when caged 6 wk. Weekly acephate (Orthene) foliar sprays for 2 or 4 wk after transplanting reduced thrips populations for up to 5 wk after transplanting, whereas the 6-wk sprays had lower thrips populations for up to 8 wk. TSW was lower in both the 4- and 6-wk acephate treatments than in the untreated. A tray drench application of imidacloprid (Admire) reduced thrips populations in early season plus lowered the percentage of TSW compared with no tray drench treatment. The tobacco thrips, Frankliniella fusca (Hinds), was the predominate thrips species on tobacco foliage, and 1.9-4.9% tested positive for nonstructural TSW protein. The imidacloprid tray drench treatment and 6-wk acephate foliar sprays had lower densities of the tobacco-adapted form of Myzus persicae (Sulzer). Suppressing early season thrips populations with foliar acephate or imidacloprid tray drench are management option that can effectively reduce the incidence of TSW in flue-cured tobacco plus suppress aphids.

UTILIZATION OF COMBINING BIOTIC AND ABIOTIC TREATMENTS TO CONTROL BACTERIAL ANGULAR LEAF SPOT DISEASE OF CUCUMBER

Bacterial angular leaf spot disease caused by Pseudomonas syringae pv. lachrymans is an important foliage disease of cucumber, under protected cultivation system. The present work was planned to control the disease using bio-agents and abiotic agents alone or combining, under greenhouse and commercial plastic house conditions. Data obtained indicated that application of bio- and abiotic agents decreased severity of bacterial angular leaf spot disease of cucumber, compared with the control. Fluorescent Pseudomonads (Pseudomonas aeruginosa, P. fluorescens and P. putida isolates) were more effectiveness than isolate of Bacillus subtilis to reduce the disease severity, when they were applied as soil drench treatment. Application of abiotic agents as foliar treatment was more effective than as seed treatment to decrease the disease severity. Isolates of P. fluorescens or P. putida as bio-agents and salicylic acid or ethephone as abiotic agents were the most effective against the disease. Disease severity was significantly reduced by increasing rates of abiotic agents. However, interaction between bio-agents (P. fluorescens or P. putida isolates) as soil treatment and abiotic agents (salicylic acid or ethephone) as foliar treatment greatly decreased severity of bacterial angular leaf spot disease of cucumber, under greenhouse and commercial plastic house condition, compared with the control. Combination between P fluorescens isolate as soil treatment and salicylic acid as foliar treatment were the most effective against the disease

Watsonias as container plants: using paclobutrazol for flowering and height control

South African watsonias were evaluated for their potential as flowering pot plants, following chemical dwarfing. Corms were treated with paclobutrazol as a 5mg, 10mg or 20mg active ingredient (a.i.) per pot post-emergent soil drench, or vacuum-infiltrated pre-planting with 0.5mg, 1mg or 2mg a.i. per corm. Both treatments significantly reduced perpendicular leaf height, although infiltration of all but the most under-developed corms caused inflorescence abortion. Flowering plants shorter than 36cm were considered to be attractive, commercially viable pot plants — provided that flowering percentage, flower number and the onset of flowering were not adversely affected by treatment and that flowers were displayed clear of the foliage. The highest concentration of paclobutrazol applied as a drench resulted in obscured inflorescences, indicating an enhanced dwarfing effect on the inflorescence rather than leaf heights. Marketable dwarfs were obtained following a single drench treatment of 10mg a.i. per pot or after a single infiltration episode with 1mg a.i. per corm, allowing the successful adaptation of watsonias to container cultivation.

(54) Response of Betulanigra `BNMTF' to Foliar and Drench Applications of Nickel

Mouse ear disorder on container-grown river birch (Betulanigra L.) is a national problem caused by a deficiency of nickel. Symptomatic plants have leaves which are small, wrinkled, darker green, cupped, and have necrotic margins. Research showed that mouse ear could be cured by applications of nickel sulfate (Ruter, 2004). Further research was needed to determine optimal rates of application for sprays and drenches and to determine if phytotoxicity occurs at high rates. A study was initiated at a nursery in South Georgia on 25 June 2003, using river birch in their second growing season in #15 containers. Plants were selected for uniformity of mouse ear disorder. Treatments included a control, urea (0.24 g·L-1) + surfactant (1.0 mL·L-1), 250, 500, 750, and 1000 mg·L-1 nickel sulfate sprays, and substrate drenches applied at 150 and 300 mg of Ni/pot. After 30 days, all plants treated with nickel sulfate had 100% normal growth, except the 150 mg of Ni/pot drench, which had 79% of the canopy showing normal growth. No phytotoxicity was noted. Plants receiving foliar sprays had a 66% to 72% increase in leaf area, a 64% to 68% increase in leaf dry mass, a 31% to 44% increase in stem length, and a 9% to 17% increase in specific leaf area compared to nontreated plants. Drench treatments increased leaf area up to 62%, leaf dry mass to 55% and stem length up to 29% over control plants. Nickel in the foliage of nontreated plants was 2.3 mg·kg-1. For the spray treatments, foliar Ni ranged from 5.5 mg·kg-1 for the 250 mg·L-1 treatment to 9.3 mg·kg-1 for the 1000 mg·L-1 treatment. Though plants at the high rate of drench treatment resumed normal growth, foliar Ni levels were not different from control plants. In general, if plants were treated with Ni, then foliar B, Fe, and Zn decreased.

(94) Efficacy of Application Methods and Concentration of Plant Growth Retardants on Growth of Chrysanthemum (Dendranthem ×grandiflorum `Cheasepeake')

Efficacy of application methods and concentration of plant growth retardants on growth of chrysanthemum (Dendranthema ×grandiflorum cv. Cheasepeake) was tested. B-9 or cycocel (CCC) as a growth retardant was applied as drench or subapplication with nutrient solution. In the case of B-9 drench treatments, as B-9 concentrations increased, numbers of flowers and flower buds increased except in the 1500-ppm treatment. Increasing concentration of CCC also resulted in reduction of flower numbers, total plant height, total leaf area, branch number, and fresh weight. Reduction ratio of total plant height in 2000 ppm showed about 56.9% being compared to that of the 100-ppm drench treatment. B-9 or CCC, combined with nutrient solution, was also supplied from the C-channel subirrigation system. The B-9 subapplication treatment showed no significance among these concentrations, but flower numbers, total plant height, average plant height, and leaf numbers decreased as concentrations of CCC increased. B-9 or CCC with the same concentration was drenched after 2 weeks of the first experiment to compare planting time efficacy. Measured data increased until B-9 increased up to 2500 ppm and severe growth retardation resulted from the 5000-ppm treatment. Through this growth retardant application study, the combination of drenching concentration and period of plant growth regulators (PGRs) may result in effective growth retardation and reduction of application concentrations for pot plant production.

GROWING METHODS AND CHEMICAL DRENCHES CONTROL CALLA SOFT ROT

Bacterial soft rot, caused by Erwinia carotovora subsp. carotovora, is the most important disease affecting callas grown in New Zealand. The aim of this experiment was to determine the effects of chemical drench treatments on the incidence and severity of soft rot in callas grown in soil and in sawdust. There were four drench treatments: (1) no drench; (2) one drench application immediately after planting; (3) drench applied after planting, then at 28-day intervals; (4) drench after planting, then at 28-day intervals from the first visible occurrence of soft rot plot. The soil drench was an aqueous solution of 0.05% Kocide ® (350 g/kg copper), 0.05% Terrazole ® (350 g/kg etridiazole), and 0.15% Terrachlor ® (750 g/kg quintozene). Five litres of drench solution per plot was applied to the soil around the base of each plant. More calla plants died when grown in soil than in sawdust for each drench treatment. For both growing media, drenching plants at 28-day intervals resulted in the lowest numbers of dead plants during crop growth and rots in lifted tubers.

Impact of Early-Season Thrips Management on Reducing the Risks of Spotted Wilt Virus and Suppressing Aphid Populations in Flue-Cured Tobacco

The influence of tray drench (TD) treatments, with and without foliar applications of the plant activator acibenzolar-S-methyl (Actigard), was examined in replicated field plots in 2000–2002. TD treatments of Actigard, imidacloprid (Admire), and these two products combined had little effect on seasonal mean thrips populations; however, thrips densities were lower in the Admire-treated plots at 4 and 5 wk after transplanting. Actigard and Admire TD treatments significantly reduced the seasonal incidence of tomato spotted wilt virus (TSWV) symptomatic plants in 2 yr in the study. The combination of both products was better in reducing TSWV than Actigard alone. Three early-season foliar sprays of Actigard had no effect on thrips population densities, but they did reduce TSWV incidence. The tobacco thrips, Frankliniella fusca (Hinds), comprised 92–95% of the thrips complex each year. Other thrips collected on tobacco foliage at very low densities included Haplothrips spp., Chirothrips spp., Limothrips cerealium (Haliday), other Frankliniella spp. and other unidentified species. Using nonstructural TSWV protein enzyme-linked immunosorbent assay, 1.5–2.3% of the F. fusca tested positive for nonstructural TSWV protein. Cured yields were higher in the TD treatments and the Actigard foliar treatments in the years with high TSWV in the untreated plots. The TD treatments and foliar Actigard had little impact on plant height or grade index; however, TD treatments with Admire had low tobacco aphid, Myzus nicotianae Blackman, populations through 10 wk after transplanting. The early-season Actigard and Admire treatment options are management decisions that can effectively reduce the risks of TSWV incidence in flue-cured tobacco.

Impact of Early-Season Thrips Management on Reducing the Risks of Spotted Wilt Virus and Suppressing Aphid Populations in Flue-Cured Tobacco

The influence of tray drench (TD) treatments, with and without foliar applications of the plant activator acibenzolar-S-methyl (Actigard), was examined in replicated field plots in 2000--2002. TD treatments of Actigard, imidacloprid (Admire), and these two products combined had little effect on seasonal mean thrips populations; however, thrips densities were lower in the Admire-treated plots at 4 and 5 wk after transplanting. Actigard and Admire TD treatments significantly reduced the seasonal incidence of tomato spotted wilt virus (TSWV) symptomatic plants in 2 yr in the study. The combination of both products was better in reducing TSWV than Actigard alone. Three early-season foliar sprays of Actigard had no effect on thrips population densities, but they did reduce TSWV incidence. The tobacco thrips, Frankliniella fusca (Hinds), comprised 92-95% of the thrips complex each year. Other thrips collected on tobacco foliage at very low densities included Haplothrips spp., Chirothrips spp., Limothrips cerealium (Haliday), other Frankliniella spp. and other unidentified species. Using nonstructural TSWV protein enzyme-linked immunosorbent assay, 1.5-2.3% of the F. fusca tested positive for nonstructural TSWV protein. Cured yields were higher in the TD treatments and the Actigard foliar treatments in the years with high TSWV in the untreated plots. The TD treatments and foliar Actigard had little impact on plant height or grade index; however, TD treatments with Admire had low tobacco aphid, Myzus nicotianae Blackman, populations through 10 wk after transplanting. The early-season Actigard and Admire treatment options are management decisions that can effectively reduce the risks of TSWV incidence in flue-cured tobacco.

Hot Water Drench Treatments for the Control of Radopholus similis in Rhapis and Fishtail Palms

Exporters of potted nursery stock face strict quarantine regulations against the burrowing nematode, Radopholus similis. Currently, there are no treatments approved by quarantine authorities to disinfest plants of R. similis. Interceptions of the nematode lead to significant economic loss and curtailment of trade, therefore hot-water drench treatments were investigated for quarantine utility. Drenches with 50 °C water were applied for 10 to 16 minutes to two economically important palm species, rhapis (Rhapis excelsa) and fishtail (Caryota mitis). Plants were inoculated with 5,000 mixed life stages of R. similis and allowed to establish for 14 weeks before drench treatments. In rhapis, a moderately good host to R. similis, a 16-minute hot water drench had high efficacy, achieving 99.6% mortality. In fishtail, a poor host, all treatments longer than 10 minutes at 50 °C eliminated R. similis from the plants. Probit regression estimates of the LT99, were 16.9 and 10.3 minutes respectively. However χ2 goodness-of-fit tests were significant (χ2 = 21.136, df = 3, p &lt; 0.0001) for rhapis. Since most observed values were between the 95% fiducial limits, this suggests that the large χ2 value was caused by variability in response or insufficient repetitions rather than an inappropriate model. A χ2 statistic could not be computed for fishtail because poor host status led to variances that were nearly equal to zero. The high efficacy of hot water drenches for the control of R. similis is approaching the Probit 9 standard of 99.9968% mortality required for approval as a quarantine treatment.

Fall Subsurface Insecticide Treatments Control European Chafer Grubs Damaging Field-Grown Nursery Crops

Abstract Third instar European chafer (EC), Rhizotrogus majalis (Razoumowsky), were found to be killing field-grown Rhododendrons ‘P.J.M.’ and Eastern hemlocks in two commercial nurseries in northeastern Ohio. Apparently, 1 or 2 grubs per plant were sufficient to severely damage young plants (rhododendrons). Subsurface applications of Dursban TNP were tested as rescue treatments against the grubs in these fields. Three novel single-point subsurface applicators were tested for delivery of Dursban in the rhododendron trial. A subsurface treatment of Dursban TNP was compared to surface applied drench treatments of Dursban TNP and Dylox 80 T &amp; O in the hemlock trial. We found that EC grubs killed young plants of both species by removing most of the fibrous roots and/or girdling the stems. The subsurface treatments of Dursban TNP, significantly reduced (95%) the number of EC grubs compared to untreated hemlocks and rhododendrons when treatments were applied early or late fall, respectively. There were no differences in suppression of grubs among the applicators in the rhododendron trial.