Drench Application Research Articles

Concentration and Timing of Ethephon Drench Applications Interact to Affect Growth and Flowering of Containerized Angelonia and Geranium

Ethephon drenches have been reported to effectively control growth of containerized bedding plants. However, previous researchers have indicated that the effects of ethephon drenches on growth and flowering may differ depending on the timing of applications. Our objectives were to quantify the effects of ethephon concentration, timing of substrate drench application, and their interaction on the growth, size, and flowering of two annual bedding plants. Angelonia (Angelonia angustifolia) and geranium (Pelargonium ×hortorum), seedlings were planted in 10.2-cm-diameter containers filled with a commercial, soilless growing substrate composed of (by vol.) 75% sphagnum peatmoss, and 25% perlite. Five, 10, 15, or 20 days after transplanting seedlings, 70-mL aliquots containing 0, 50, 100, or 200 mg·L−1 ethephon were applied as substrate drenches. Species varied in their growth and flowering responses to ethephon concentration, drench application timing, and their interaction. For angelonia, flowering was delayed most with early applications and high concentrations, and delay was diminished with later applications. Angelonia height was unaffected by late applications, though lateral growth was suppressed 20 days after transplant with 200 mg·L−1 ethephon. Flowering of geranium was only delayed when ethephon was applied 5 days after transplanting, whereas flowering, vegetative height, and shoot dry weight were affected more by earlier applications and higher concentrations. Width and root weight were only affected by ethephon concentration, with growth suppression increasing as concentrations increased. Ethephon is an effective growth regulator when applied as a substrate drench. However, the degree of activity and resulting impact on flowering, size, and growth is influenced by the interaction between ethephon concentrations and the timing of drench applications after transplanting.

Evaluation of botanical and chemical products for the control of foliar nematodes Aphelenchoides fragariae

Foliar nematodes Aphelenchoides spp. Pose a serious threat to floriculture by causing significant economic losses in home gardens, production nurseries and arboretums, and threatening precious germplasm collections of many ornamental plants. Control of foliar nematodes has become difficult due to the loss of nematicides following the implementation of the U.S. Food Quality Protection Act. Herein, we used a three-stage approach to evaluate 24 products for their potential to control foliar nematodes Aphelenchoides fragariae in hosta. We first performed a direct contact assay in well-plates where A. fragariae nematodes were exposed to the aqueous suspension of high (2-fold dilution) or low (20-fold dilution) concentration of the test products. The products causing 100% nematode mortality at the low concentration were then tested through a drench application for their effectiveness against foliar nematodes in soil, followed by a leaf-disc test to determine their efficacy against nematodes in leaves as a spray application. Of the 24 products, Ammonia, Clorox, grapefruit seed extract, KMnO4, NaDCC, Nemakill, Pylon and ZeroTol caused 100% nematode mortality in aqueous suspension at 20-fold dilution. Drench application of Ammonia, Clorox, KMnO4, NaDCC and ZeroTol reduced over 85% and over 75% A. fragariae population in soil 7 and 42 days after treatment, respectively. Spray application of ZeroTol could reduce over 70% A. fragariae population in leaf discs, whereas Ammonia, Clorox, KMnO4 and NaDCC caused about 50% reduction. Pylon (24% chlorfenapyr) and Nemakill (32% cinnamon oil, 8% clove oil, 15% thyme oil mixture) showed 100% mortality of A. fragariae in all three types of tests, and thus have great potential to serve as effective alternatives to manage foliar nematodes in floriculture.

RESPONSE OF TOMATO PLANTS TO SOME AGRICULTURAL AND CHEMICAL TREATMENTS ON FRUIT YIELD AND ITS QUALITY RELATION TO TUTA ABSOLUTA (MEYRICK) AND BEMISIATABACI (Genn.) INFESTATION

An experiment was carried out to study the effect of some agricultural and chemical treatments on two serious insects i.e. leaf miner, Tuta asoluta (Meyrick), and the cotton whitefly Bemisia tabaci (Genn.) that infest tomato plants, as well as the influence on the growth, fruit yield and its quality were evaluated. The trail was carried out in a sandy soil at Amoun Agricultural Association, Eltal El Kabier, Ismailia Governorate, Egypt during two autumn seasons of 2013 and 2014. The experiment included 7 treatments as follows: covering tomato plants with agryl, white and green net as a row covering tunnels, dusting with Sulfur (repellent the insect) as the safety material for human and environmental comparing chemical pesticides i.e. Actara using it as foliar spraying or soil drench and untreated control. The results showed that the all treatments induced significant positive impact for all infest status which reduced the incidence of the two serious insects’ i.e. T. asoluta and B. tabaci on tomato plants than the control treatment during the first and second seasons. Data also showed that the all treatments were infested by tomato leaf miner (eggs and larvae stage) with low numbers of eggs under the tested conditions during the two seasons except of covering with Agryl, white net and green net which were free from any tomato leaf miner. In addition, soil treatment (soil drench) application was the most potent treatment in protecting tomato plants from the whitefly immature stages, but the lowest percentage of plants exhibiting virus symptoms (TYLCV) recorded by covering with white net treatment compared with untreated (control) during the two tested seasons. Concerning the effect of using some agricultural and the chemical treatments on horticultural characters of tomato plant, the obtained results indicated positive effect on the all studied parameter of tomato i.e. vegetative growth characters, physical and chemical fruit characters, flowering characteristics and yield components during the two seasons. The data showed that the rows covering with white net was the best potent treatment safety treatment for human healthy followed by foliar spraying with Actara 25% WG (Thiamethoxam) 20g./100 of water as chemical treatment on yield, which recorded (41.7 and 43.2), (30.32 and 32.13) tons per feddan during the first and second seasons respectively compared with other treatments. Moreover the covering with white net also recoded the first ranking in economic study which recoded the best value (34200 and 35700) Egyptian pound on total income without addition the cost of agriculture practices during the first and second seasons respectively. For that it can recommend by covering tomato plants with white net followed by covering with agryl especially at heavy infection seasons with the serious insects as T. asoluta and B. tabaci for producing high tomato yield with best quality, in addition safety human health and environment without using pesticide.

Enhancing mint and basil oil composition and antibacterial activity using seaweed extracts

The increasing cost of synthetic fertilizers and conventional agrochemicals calls for an urgent search for next generation of environmental-friendly competitive fertilizers and growth stimulants that enhance the essential oil content and composition of traditional global medicinal plants such as mint (Mentha×piperita L.“chocolate”) and sweet basil (Ocimum basilicum L. “purple ruffle”). The study aims to evaluate the morphological and physiological effects of seaweed extracts (Ascophyllum nodosum) doses and application methods on mint and basil plants essential oil composition and its respective antibacterial activities. The plants were subjected to two doses of foliar/drench weekly applications of A. nodosum extracts at 5 and 7mLL−1 for 12 weeks. A. nodosum extracts drench and foliar treatments increased leaf number and area, dry weights, and plant height of both plants. In mint and basil plants, there were increases in the essential oil content and enhanced composition following A. nodosum treatments. In mint plants, the drench application of 7mLL−1 SWE had the highest oil contents of l-menthone (32.4%) and l-menthol (32.6%) while basil treated plants showed the highest composition of chavicol methyl ether (38.7%), linalool (29.1%), and cineol (9.1%). Additionally decreasing of potentially toxic pulegone and methofuran in mint oil was noticed. A. nodosum treated plants showed higher antibacterial potential than control. In mint and basil plants, the highest antibacterial activity found was in the essential oil of mint plants drenched with 7mLL−1 SWE and the antibacterial activities of mint oils were higher than basil. The biostimulant effect of A. nodosum extract treatments was attributed to the macro- and micro-elements composition as well as the carbohydrate contents.

Biological services by Streptomyces lavendulae MTCC 706 to control invasion, development and reproduction of root-knot nematode (Meloidogyne incognita) infecting tomato cv Pusa Ruby

The drench application of S. lavendulae MTCC706 @ 2% v/w (SLT) resulted in less than 50% juvenile invasion of M. incognita J2s in tomato (cv. Pusa Ruby), delayed development of J4s, 50.7% reduction in root galling and 42.7% reduction in egg mass production, compared to control. The reproduction factor was 1.2 in SLT, compared to 2.4 in control in 45 days. SLT was compatible with the nematicide carbofuran, as increase in bioefficacy of SLT was observed with 60% reduction in root galling, 61.5% reduction in egg mass production, and a reproduction factor of 1.1 in the combined application with carbofuran @0.5 kg a.i/ha. Replanting of tomato in the pre-treated soil revealed a further reduction in root galling (81.3%), egg mass production (80.5%) and reproduction factor (0.6), indicating establishment of the actinomycete in the soil.

Japanese Maple Scale Activity and Management in Field Nursery Production

Japanese maple scale, Lopholeucaspis japonica Cockerell (Hemiptera: Diaspididae), is an armored scale found on the bark of many woody nursery and landscape plants. Scale crawler and male flight activity was monitored in middle Tennessee in fields of cherry (Prunus serrulata Lindl. ‘Kwanzan’) for two seasons. Two generations of crawlers were observed, with a large peak of activity in late May and a second, less pronounced peak in August. Male flights occurred twice a year, in April and July. Spray and drench applications of insecticides were trialed in 2014 and 2015. Dormant oil applications reduced overwintering scale populations by 76%. Drench applications of imidacloprid in 2014 suppressed scale populations by 58% by four months following application and the following summer those same trees had no observable scale infestation. Summer trunk applications of pyriproxyfen were effective at managing scale crawlers while horticultural oil alone had no measurable effect. When scale populations were high at the outset of spring 2014, a dinotefuran drench application was ineffective after 90 days. Dinotefuran gave greater control in 2015 when scale populations were low prior to application. Based on these results, a multiple component program for field management of Japanese maple scale is recommended.

FLOWER QUALITY CHARACTERS RESPONSE OF GRAFTED AND NON-GRAFTED CAPE JASMINE (GARDENIA JASMINOIDES ELLIS) TO FOLIAR IRON SPRAY AND PACLOBUTRAZOL TREATMENTS

Two pot experiments of grafted cape jasmine (Gardenia jasminoides on G. thunbergia rootstock) and non-grafted cape jasmine were carried out in lath house, Horticulture Dept., Agriculture College, Tikrit University at the agricultural season of 2013. The effect of foliar iron spray and paclobutrazol treatments on flower quality characters of these plants was investigated. Foliar iron spray (Fe2SO4 6%) at the rate of 1 ml.L-1 was applied every 15 and 30 days. The paclobutrazol treatment was added as drench application on three levels (0, 10 and 20 mg.L-1). Factorial experiment within Randomized Complete Block Design was used. The results showed that superior iron spraying treatment affected the flower number, weight and diameter. Foliar spray every 30 days gave the highest flower number (8.68) of grafted plant and (0.88) of non-grafted plant. Adding paclobutrazol at the level of 10 mg.L-1 resulted insignificant increase in flower weight of non-grafted plant (3.079). The interaction treatment between foliar iron spray every 30 days and pacloburazol level (20 mg.L-1) gave the highest volatile oil content (0.68 µg.g-1).

Thiamethoxam and imidacloprid drench applications on sweet orange nursery trees disrupt the feeding and settling behaviour of Diaphorina citri (Hemiptera: Liviidae).

Chemical control is the method most used for management of Diaphorina citri, the vector of the phloem-limited bacteria associated with citrus huanglongbing (HLB) disease. The objectives of this study were to determine the influence of soil-drench applications of neonicotinoids (thiamethoxam and imidacloprid) on the probing behaviour of D. citri on citrus nursery trees, using the electrical penetration graph (EPG) technique, and to measure the D. citri settling behaviour after probing on citrus nursery trees that had received these neonicotinoid treatments. The drench applications of neonicotinoids on citrus nursery trees disrupt D. citri probing, mainly for EPG variables related to phloem sap ingestion, with a significant reduction (≈90%) in the duration of this activity compared with untreated plants in all assessment periods (15, 35 and 90 days after application). Moreover, both insecticides have a repellent effect on D. citri, resulting in significant dispersal of psyllids from treated plants. This study clearly demonstrates the interference of soil-applied neonicotinoids on the feeding and settling behaviour of D. citri on citrus nursery trees, mainly during the phloem ingestion phase. These findings reinforce the recommendation of drench application of neonicotinoids before planting nursery trees as a useful strategy for HLB management. © 2015 Society of Chemical Industry.

Efficacy of Insecticides Against Root Mealybugs inPisonia brunoniana, 2012: Table 1

This study was conducted at the University of Hawaii at Manoa, Waiakea Agricultural Research Center near Hilo, HI, under greenhouse conditions to determine the efficacy of several insecticides against root mealybugs infesting Pisonia brunoniana planted in cinder media in 2-inch pots. Drench or foliar applications of seven insecticides were compared to an untreated check (eight treatments). Treatments were assigned to experimental units in a RCB design with seven replicates: single drench applications of Orthene TTO 97 (acephate), A16901B (cyantraniliprole thiamethoxam), Safari 20SG (dinotefuran), or Kontos (spirotetramat); two drenches 14 days apart of MBI 203 …

Gaseous 3-pentanol primes plant immunity against a bacterial speck pathogen, Pseudomonas syringae pv. tomato via salicylic acid and jasmonic acid-dependent signaling pathways in Arabidopsis.

3-Pentanol is an active organic compound produced by plants and is a component of emitted insect sex pheromones. A previous study reported that drench application of 3-pentanol elicited plant immunity against microbial pathogens and an insect pest in crop plants. Here, we evaluated whether 3-pentanol and the derivatives 1-pentanol and 2-pentanol induced plant systemic resistance using the in vitro I-plate system. Exposure of Arabidopsis seedlings to 10 μM and 100 nM 3-pentanol evaporate elicited an immune response to Pseudomonas syringae pv. tomato DC3000. We performed quantitative real-time PCR to investigate the 3-pentanol-mediated Arabidopsis immune responses by determining Pathogenesis-Related (PR) gene expression levels associated with defense signaling through salicylic acid (SA), jasmonic acid (JA), and ethylene signaling pathways. The results show that exposure to 3-pentanol and subsequent pathogen challenge upregulated PDF1.2 and PR1 expression. Selected Arabidopsis mutants confirmed that the 3-pentanol-mediated immune response involved SA and JA signaling pathways and the NPR1 gene. Taken together, this study indicates that gaseous 3-pentanol triggers induced resistance in Arabidopsis by priming SA and JA signaling pathways. To our knowledge, this is the first report that a volatile compound of an insect sex pheromone triggers plant systemic resistance against a bacterial pathogen.

Paclobutrazol or uniconazole effects on ethylene sensitivity of potted ornamental plants and plugs

Effects of paclobutrazol on postharvest ethylene sensitivity of potted cuphea (Cuphea hyssopifolia Kunth) and petunia (Petunia×hybrida Vilm.) plants, and uniconazole on portulaca (Portulaca oleracea L.) plugs were evaluated. Paclobutrazol was applied as a drench at 0, 1, 2, or 4mgL−1 per 12.5cm pot for cuphea, or 0, 2, 4, or 8mgL−1 per 15.2cm pot for petunia, while uniconazole was applied at 0, 2.0, 4.0, or 8.0mgL−1 with a volume of 0.21Lm−2 as a foliar spray for portulaca plugs. With an increase in paclobutrazol dose or uniconazole concentration, plant growth [plant height and diameter (potted plants only), shoot fresh weight, or dry weight] was controlled for all species tested. While use of paclobutrazol or uniconazole controlled excessive plant growth of all three species, the plant growth retardants had no effect on postharvest ethylene sensitivity as most flowers abscised from all plants exposed to exogenous ethylene. However, both paclobutrazol and uniconazole reduced postharvest flower abscission of plants not treated with exogenous ethylene. During simulated shipping and marketing, paclobutrazol and uniconazole maintained darker foliage and controlled height. Drench applications of 2–4mgL−1 paclobutrazol for cuphea and 4–8mgL−1 for petunia potted plants and spray applications of 4–8mgL−1 uniconazole for portulaca plugs produced compact, high quality plants while also extending postharvest longevity and quality.

Effectiveness of Cyantraniliprole for Managing Bemisia tabaci (Hemiptera: Aleyrodidae) and Interfering with Transmission of Tomato Yellow Leaf Curl Virus on Tomato.

Cyantraniliprole is the second xylem-systemic active ingredient in the new anthranilic diamide class. Greenhouse (2006), growth chamber (2007), and field studies (2009-2010) were conducted to determine the efficacy of cyantraniliprole for managing Bemisia tabaci (Gennadius) biotype B and in interfering with transmission of tomato yellow leaf curl virus (TYLCV) by this whitefly. Cyantraniliprole applied as soil treatments (200 SC) or foliar sprays (100 OD) provided excellent adult whitefly control, TYLCV suppression, and reduced oviposition and nymph survival, comparable to current standards. The positive results observed in these greenhouse experiments with a high level of insect pressure (10× the field threshold of one adult per plant) and disease pressure (five adults per plant, with a high level of confidence that TYLCV virulent adults were used), indicate a great potential for cyantraniliprole to be used in a whitefly management program. Field evaluations of soil drench treatments confirmed the suppression of TYLCV transmission demonstrated in the greenhouse studies. Field studies in 2009 and 2010 showed that cyantraniliprole (200 SC) provided TYLCV suppression for 2 wk after a drench application, when using a susceptible (2009) or imidacloprid-tolerant (2010) whitefly population. Cyantraniliprole was demonstrated to be a promising tool for management of TYLCV in tomato production, which is very difficult and expensive, and which has limited options. The integration of cyantraniliprole into a resistance management program will help to ensure the continued sustainability of this and current insecticides used for the management of insect vectors, including whiteflies and the TYLCV they spreads.

EFFECT OF DRENCHING COPTIS CHINENSIS FRANCH EXTRACT ON SOFT ROT OF ZANTEDESCHIA 'BLACK MAGIC'

Calla lily (Zantedeschia sp.) is an important cut flower, pot plant or garden ornamental. However, bacterial soft rot (Pectobacterium carotovorum subsp. carotovorum) adversely affects the commercial viability of this crop. We conducted two field experiments to determine the effect of drench application of a formulated Coptis chinensis extract product on soft rot of Zantedeschia ‘Black Magic’. Three application rates of C. chinensis extract (0.625, 1.25 and 2.5 L/ha) were compared with copper hydroxide at 2 kg/ha, streptomycin at 100 ppm and water as control treatments in a randomized complete block design experiment with 3 replications. Pre-germinated tubers of Zantedeschia were planted on 1 m2 plots at a spacing of 20A—20 cm and drenched four times with the treatments at 14 days interval from either planting or at full foliage stage. Drenching of C. chinensis extract from planting significantly reduced soft rot incidence while drenching the extract at full foliage stage had no significant effect on incidence of the disease. Application of C. chinensis extract significantly suppressed the severity of soft rot with the highest rate (2.5 L/ha) consistently recording a lower percent disease index (PDI). Our results demonstrate the potential of C. chinensis extract to suppress soft rot of Zantedeschia.

Effects of Pinching, Number of Cuttings per Pot, and Plant Growth Regulators on Height Control of Purple Firespike

Purple firespike (Odontonema callistachyum), native to Central America, has potential for use as a new flowering potted plant. The effects of number of pinches (zero, one, or two) and number of cuttings (one, two, or three) per 6-inch pot were evaluated on the control of plant height. Plant height was suppressed as the pinch number increased. The greatest reduction was recorded with one cutting per pot and two pinches. The maximum number of branches per pot was recorded with two pinches and three cuttings per pot. In a second experiment, plant growth regulators (PGR) were also tested for efficacy of height control; 2 weeks after pinching, foliar sprays of paclobutrazol, flurprimidol, daminozide, chlormequat, and a tank-mix of daminozide + chlormequat or media drenches of paclobutrazol, uniconazole, or flurprimidol were applied. Plant height, leaf area, and leaf dry weight were recorded at 3, 6, and 9 weeks after PGR application. Maximum height control was obtained with uniconazole drench at 8 ppm, resulting in plants 22 cm tall, 61% shorter than the untreated control (56 cm); however, it resulted in severe leaf distortion. Plant height was 56% and 46% shorter than the control using drenches of paclobutrazol at 30 ppm and flurprimidol at 15 ppm, respectively. Daminozide spray at 2000 ppm and tank-mix of daminozide + chlormequat at 4500/1500 ppm suppressed stem elongation by 20.3% and 19%, respectively. Plants treated with paclobutrazol drench at 30 ppm reduced leaf area and leaf dry weight compared with other PGRs. Chlormequat spray at tested concentrations was ineffective for controlling firespike plant growth. The most attractive potted plants were produced using a drench application of paclobutrazol at 10 or 15 ppm.

Flurprimidol Performance on Ornamental Species in Relation to Trimming Time and Method of Application

The plant growth regulator flurprimidol (Cutless G) is registered for use on ornamental plants to reduce internode elongation and reduce trimming frequency. It has been hypothesized that timing of the trimming event can be related to the efficacy of the flurprimidol treatment. Granular flurprimidol was applied to well-established plants at a standard rate of 22.5 g/a.i. (15 lbs product)/1000 ft2 on 23 Apr. 2012 and 1 May 2013.Two common Florida landscaping species, Viburnum odoratissimum and V. suspensum, were selected to be trimmed at different times to investigate flurprimidol efficacy by measuring plant regrowth, biomass, and visual appearance. The five trimming treatments occurred at 7 days before (flurprimidol) application (DBA), 0 DBA, 7 days after application (DAA), 14 DAA, and 21 DAA. No significant differences were observed in trimming times for flurprimidol-treated V. odoratissimum or V. suspensum. V. odoratissimum shoot regrowth was significantly reduced in flurprimidol-treated plants compared with the untreated control (UTC). The insufficient growth regulation observed in both Viburnum species is likely the result of species tolerance. Two flurprimidol application methods, granular and drench, were evaluated against an UTC on two landscaping species, Elaeagnus pungens and Loropetalum chinense. This experiment was to determine if a granular or drench application would influence the performance of flurprimidol. Shoot growth of E. pungens was reduced 4.3% and 13.9% by the granular and drench applications, respectively, but was not significantly different from one another or the UTC. The granular application reduced biomass (25.1%) but was not significantly different from the drench (16.9%). L. chinense shoot regrowth was decreased 39.5% and 38.2% by the granular and drench treatments, respectively. Plant biomass was significantly reduced in both treatments compared with the UTC (17.0% by granular and 13.9% by drench), but the biomass and visual assessments between the application methods were not significantly different. Species sensitivity was found to have a substantial influence on the efficacy of a flurprimidol application.

Induced resistance against the Asian citrus psyllid, Diaphorina citri, by β-aminobutyric acid in citrus

β-Aminobutyric acid (BABA) is known to induce resistance to microbial pathogens, nematodes and insects in several host plant/pest systems. The present study was undertaken to determine whether a similar effect of BABA occurred against the Asian citrus psyllid, Diaphorina citri Kuwayama, in citrus. A 25 mM drench application of BABA significantly reduced the number of eggs/plant as compared with a water control, whereas 200 and 100 mM applications of BABA reduced the numbers of nymphs/plant and adults/plants, respectively. A 5 mM foliar application of BABA significantly reduced the number of adults but not eggs or nymphs when compared with a water control treatment. In addition, leaf-dip bioassays using various concentrations (25–500 mM) of BABA indicated no direct toxic effect on 2nd and 5th instar nymphs or adult D. citri. BABA-treated plants were characterized by significantly lower levels of iron, magnesium, phosphorus, sodium, sulfur and zinc as compared with control plants. The expression level of the PR-2 gene (β-1,3-glucanase) in BABA-treated plants that were also damaged by D. citri adult feeding was significantly higher than in plants exposed to BABA, D. citri feeding alone or control plants. Our results indicate the potential for using BABA as a systemic acquired resistance management tool for D. citri.

Bell Pepper Seedling Phytotoxicity Due to Abscisic Acid Drench Applications

Bell pepper transplant height control is essential to produce a strong plant capable of surviving the transplant process. Transplant producers are interested in environmental, physical, and chemical methods to control plant height in the greenhouse. One emerging technology for transplant height control on bell pepper is the use abscisic acid (ABA); however, at high doses some phytotoxicity has been observed. Greenhouse experiments were conducted to determine the degree of phytotoxicity induced by an exogenous drench application of abscisic acid on ‘Aristotle’ bell pepper (Capsicum annuum L.), seedlings. Abscisic acid concentrations (1,000, 5,000, 10,000, 25,000, and 50,000 mg·L−1) were applied over a 1- to 5-week period beginning at the cotyledon stage, in addition to an untreated control. Plant survival for the control and the 1,000 mg·L−1 (baseline treatments) was significantly greater compared to a single application or multiple applications of greater concentrations. The results indicated that applying higher concentrations of ABA (5,000 mg·L−1 or more) using multiple lower concentration applications provided lower hazard ratios and increased longevity compared to a single higher concentration application. The ABA delivered as a drench at the cotyledon stage at concentrations of 5,000 mg·L−1 or below can control transplant height with no visible phytotoxicity.

Chemical control of Cylindrocladium and Rhizoctonia root rots in blueberry propagation

Cylindrocladium and Rhizoctonia root rots, caused by Cylindrocladium parasiticum and binucleate Rhizoctonia spp., respectively, are common soilborne diseases observed during blueberry propagation in Georgia, USA. Six trials with artificially inoculated propagation medium were completed in a shade-house to determine the efficacy of select fungicides to control these diseases. For Cylindrocladium root rot, two trials with single-drench fungicide applications were made at the time the cuttings (southern highbush blueberry cultivar Rebel) were stuck. In two additional trials, a second drench application was added two weeks later. In all trials, fludioxonil (Medallion) significantly reduced lesion incidence and lesion length. Neither triflumizole (Terraguard) nor thiophanate-methyl (Cleary's 3336) consistently reduced lesion incidence with one application, indicating that a single application of these materials was not sufficient for disease suppression. The second fungicide application improved disease control for all fungicides. However, fludioxonil always performed statistically better than thiophanate-methyl and numerically better than triflumizole as indicated by lesion incidence, lesion length and girdling incidence. For Rhizoctonia root rot, two trials were completed, each with two fungicide applications (when cuttings were stuck and 2 weeks later). Fludioxonil and azoxystrobin (Heritage) significantly reduced lesion incidence and lesion length in both trials. Flutolanil (Prostar) reduced lesion incidence in both trials and also reduced lesion length in the second trial. Pending labeling for this use pattern, fludioxonil, which has provided good control of both diseases in our trials, may form the basis of a fungicide rotation program to supplement sanitation practices for managing Cylindrocladium and Rhizoctonia root rots in blueberry propagation.

Compatibility of Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) with imidacloprid to manage clementine nursery pests

Biological control is not common in citrus nurseries where chemical control is prevalent. The systemic neonicotinoid imidacloprid applied as a drench is effective against three out of four key pests of young clementine plants in Spain – aphids, whiteflies, and scales. However, mites, the fourth key pest, are not control by imidacloprid and could be regulated by introduction of the predatory Phytoseiid mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor). The aim of this study was to evaluate the effects of imidacloprid applied as a drench on the demographic parameters of these two predatory mites and the compatibility of P. persimilis releases with imidacloprid to control key pest populations in young clementine plants under field conditions. The results showed that some demographic parameters of P. persimilis were affected by imidacloprid. However, their combined effect on its intrinsic rate of increase was neutral. In contrast, imidacloprid negatively affected the demographic parameters of N. californicus. Field results proved that young clementine plants could be satisfactorily protected against key pests with releases of P. persimilis combined with drench applications of imidacloprid. The combination of imidacloprid with P. persimilis releases was highly effective for management of the key pests of young clementine plants in the nursery.

Thiamethoxam in the cultivation of hop – does it pose a threat to honey bees?

One serious problem in the growing of hop is the feeding damage caused by different soil insects (e.g. Curculionidae, Alticinae) during springtime. In 2010 the grower of hop in the Hallertau, the largest hop growing area in Europe, tested a new agent, thiamethoxam (Actara), that belongs to the group of neonicotinoids. The application process in hop is a drench application with 200 ml solution (50 g a. i. / ha) around the growing plant. To find out if there is any exposure of the bees to this agent, various investigations were undertaken. 24 Beehives were set up in groups of 8 at three different places with different distances to the hop fields. From April to July, twice a week homing bees were caught at the hive entrance in the early morning and were deep frozen. Dead bees were collected from dead bee traps three times weekly and also the population development and the honey production were measured. In the hop garden the occurrence of guttation of the hop was observed in regular intervals. Guttation of the grass and the plants in between hop rows was collected. Additionally, further samples of the soil, plants and puddles were taken. From the intercepted bees the honey sac was dissected and prepared for further examinations. Also the pollen loads were analysed for residues. The used agent and the known metabolite clothianidin were detectable (LOQ 0,001 mg/kg) neither in the pollen loads from single bees (n=26), nor in the honey sacs (n=2000), nor in bee bread samples (n=9) nor in harvested honey (n=9). The population development and the honey production were similar to the control group. Results of the dead bee traps showed no noticeable effects on the colonies. References