Unsprayed Trees Research Articles

Influence of plant growth regulators on growth and formation of sylleptic shoots in one-year-old apple cv. Gala Mast

Aim: To examine the effectiveness of 6-benzyladenine (BA) alone or in combination with gibberellic acid (GA3) on sylleptic shoots formation on one-year-old apple cv. Gala Mast grafted on MM-106 rootstock. Methodology: During the second vegetative period, the actively growing apical portion of the nursery tree was sprayed with varying doses of BA and BA+GA3 (200, 300, 400, 500, 600, and 700 ppm) using a hand sprayer until run-off. Three spray treatments were performed at one week apart. The first spray was applied when the growth of the central leader reached 70-80 cm. Results: All plant growth regulators treatments significantly increased the number and length of sylleptic shoots, branching zone and per cent branched trees compared to control. The unsprayed trees had an average of 1.95 useful sylleptic per tree, 1.1 m total sylleptic shoot length, 10.24 cm branching zone and 35 per cent branched trees. Application of BA (700 ppm) resulted in four-fold increase in the number of sylleptic shoots (7.8), more than two-fold increase in total length of sylleptic shoots (2.44 m), and around four-fold increase in branching zone (38.96 cm). The 100 per cent branched trees were obtained with the application of BA (500, 600, 700 ppm) and BA+GA3 (600, 700 ppm) in both experimental years. Moreover, these treatments obtained 2.78 to 2.90 values of the trunk and mean sylleptic shoot diameter ratio. Interpretation: Application of BA alone or in combination with GA3 played an important role in overcoming apical dominance and therefore in the production of well-branched apple nursery tree. However, application of BA alone has a stronger positive effect on sylleptic shoot formation. More than 400 ppm BA appears to give a significant stimulation for the production of sylleptic shoots, with the highest beneficial effect reported with the application of 700 ppm BA. However, it is cost-effective to apply 3 sprays of 500 ppm BA for adequate growth and sylleptic shoot production. Key words: 6-benzyladenine, Gibberellic acid, Nursery tree, Plant growth regulators, Sylleptic shoot

Preharvest Foliar Application of Si–Ca-Based Biostimulant Affects Postharvest Quality and Shelf-Life of Clementine Mandarin (Citrus clementina Hort. Ex Tan)

Citriculture and the postharvest industry are in the quest for biostimulants that favour fruit quality and extend shelf-life. Recently, Si has emerged as a biostimulant and its impact on fruit quality and postharvest shelf-life needs to be elucidated. The experiment is conducted for two consecutive years (2019 and 2020) in a commercial citrus orchard. In the present study, a Si–Ca-based product (Gravital® Force SC, AGROLOGY SA, Sindos, Greece) is foliar sprayed upon clementine mandarin (Citrus clementina Hort. Ex Tan cv. SRA 63) trees from August to November, while unsprayed trees are kept as controls. At commercial maturity, both sprayed and unsprayed fruits are harvested and stored for thirty (30) days at 5 °C with 90–95% relative humidity. Afterwards, they are kept at shelf temperature (20 °C) for six (6) days (shelf-life). At different intervals [at harvest, after cold storage (30 d at 5 °C), at the third day of shelf-life (30 d at 5 °C plus 3 d at 20 °C) and sixth day of shelf-life (30 d at 5 °C plus 6 d at 20 °C)], fruits are sampled and analysed for their qualitative characteristics. According to the results, the preharvest foliar application of the Si–Ca-based product delayed fruit maturation, increased peel firmness, total soluble content, total acidity, ascorbic acid, total phenols and antioxidant capacity, and reduced fruit decay during shelf storage. Results suggest that the preharvest foliar spray of Si–Ca products is able to maintain the postharvest quality of mid-ripening mandarin fruit.

Effects of foliar zinc applications on some yield parameters and essential oil constituents of the mastic tree (Pistacia lentiscus var. chia Duham.)

Mastic tree (Pistacia lentiscus var. chia Duham.) is an important medicinal aromatic plant which is being cultivated without any regular fertilization generally. Foliar Zn applications have great importance for many commercial plant species because of their important role in metabolic activities. In this study, the effects of foliar ZnSO4 sprayings (0, 0.2, 0.4, 0.8%) applied at 50% and 100% leafing stages, on some yield parameters and essential oil composition of mastic tree were assessed. A field experiment was carried out for two consecutive years at Ege University, Turkey. Mastic resin yield was more than doubled with 0.8% Zn particularly in the second year. The highest leaf Zn content was measured as 187.8 mg l−1 with 0.8% zinc spraying while it was 35.4 mg l−1 in unsprayed trees at 100% leafing in the first year. Leaf essential oil and α-tocopherol contents were not significantly influenced by different Zn levels and leafing stages in both years. As for the major essential oil constituents, β-myrcene (62.4%), germacrene-D (14.3%), α-terpinenyl acetate (5.52%), t-caryophyllene (2.1%) and α-pinene (1.4%) were determined. Zinc sprayings increased the β-myrcene, germacrene-D and α-pinene contents particularly at 100% leafing in the first year. In mastic tree two consecutive applications of Zn seems to be necessary for reaching to desirable leaf Zn contents. Application of 0.8% Zn or more would be proper to increase the contents of most parameters assessed.

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Supplemental foliar applied mixture of amino acids and seaweed extract improved vegetative growth, yield and quality of citrus fruit

Poor tree nutrient management significantly reduce productivity and quality of citrus fruit. Hence in three separate experiments, exogenous supplemental application of 0.5 mL L−1 ‘Primo’ (Ascophylum nodosum seaweed extract + amino acid and) + 0.01% ‘Tween 20′) was sprayed on citrus cvs. ‘Kinnow’, ‘Feutrell's Early’ mandarins and ‘Blood Red’ orange trees. Trees were sprayed at full bloom (T2), fruit setting (T3), full bloom + fruit setting (T4), or full bloom + fruit setting + premature (T5) stages at a same concentration. Unsprayed trees of each cvs. were kept as control (T1). In contrast to untreated control trees, the application of 0.05% Primo at full bloom + fruit setting stage caused significant increase in leaf N (28%), K (36%), Mn (24.4%), Zn (15.8%), tree height (28.5%), fruit weight tree−1 (42.6%), fruits tree−1 (28.6%), marketable fruit (9%), fruit size (11.5%), SSC (16%), SSC:TA ratio (26.8%), reducing sugars (37.5%), ascorbic acid (21.8%) and total phenolic contents (42%) in ‘Kinnow’ mandarins. Likewise, sprayed trees of ‘Feutrell's Early’ in T4 exhibits higher leaf N (27%), Fe (11.9%), Zn (26.4%), fruit weight tree−1 (28.5%), fruits tree−1 (40%), marketable fruit (12.7%), fruit size (15.9%), juice weight percentage (17.6%), taste (23%), SSC (15.7%) and total sugars (42%). Whereas, in case of ‘Blood Red’ oranges, same treatment (T4) resulted in highest level of leaf N (50%), Fe (15%), tree height (37%), leaf size (38.8%), fruit weight tree−1 (42%), number of fruits tree−1 (45%), marketable fruit (8%), juice weight percentage (15.6%), SSC (19%), SSC:TA ratio (43.8%), reducing sugars (45%) and total phenolic contents (28%) than control. In addition, reduction in fruit drop, peel thickness and TA were also observed in treated trees of all cvs. as compared to untreated control. In conclusion, supplemental application of 0.5 mL L−1 ‘Primo’ at full bloom + fruit setting stages improved vegetative growth, productivity and quality of ‘Kinnow’, ‘Feutrell's Early’ and ‘Blood Red’ fruits.

Six-spotted mite and its predators on sprayed and unsprayed ‘Hass’ avocado trees

ABSTRACT Six-spotted mite, Eotetranychus sexmaculatus (Riley), is an introduced pest of ‘Hass’ avocados in New Zealand. Avocado orchards were surveyed for six-spotted mite and its natural enemies during 2016–18. Mean counts of six-spotted mite differed when compared by year. For each year, the effect of not spraying or spraying according to an integrated pest management programme (AvoGreen®) was not consistent for most location and season combinations. When year was ignored and all locations considered together, the leaves of unsprayed trees had fewer six-spotted mites than those of sprayed trees during autumn/winter. The phenology of mites and their predators in relation to leaf abscission was also determined on unsprayed potted trees during 2018–20 at two sites. Defoliation occurred in October and November each year but the association with densities of six-spotted mites was not consistent. Four species of phytoseiid mite predators were identified on orchards and potted trees with the most common species being Amblyseius herbicolus. The coccinellid mite predators Stethorus bifidus and S. histrio occurred on potted trees. The evidence that predators were able to control six-spotted mite populations was somewhat equivocal. Trials comparing sprayed and unsprayed trees under the same nutrient management and during multiple seasons would be useful.

Life table simulations of a univoltine codling moth, Cydia pomonella, population 1. Biological control with Mastrus ridens

ABSTRACT The potential for the newly established ichneumonid Mastrus ridens (Horstmann) to provide biological control of codling moth, Cydia pomonella (L.), was simulated by incorporating different rates of parasitism into previously published life tables for a univoltine codling moth population on unsprayed apple trees in Nelson, New Zealand. Simulations over eight years were conducted using high and low initial codling moth densities, as occur respectively on neglected apple trees and commercially managed orchards. Life table simulations without M. ridens served as control treatments for comparison with simulations that included various rates of parasitism by each of the estimated three annual generations of the parasitoid. Based on the percentage parasitism recorded in New Zealand and the international literature, M. ridens is projected by the models to provide a valuable reduction of codling moth populations on neglected host trees in Nelson and thereby reduce the numbers of immigrant adult moths invading commercial apple orchards. In contrast, the codling moth is maintained at such extremely low densities within commercial apple orchards growing fruit for export that M. ridens is projected to make only a small contribution to parasitism within the orchard. These simulation results confirm the validity of the rationale for the introduction of M. ridens to New Zealand, which aimed to reduce the numbers of immigrant codling moths arriving in orchards from highly infested and neglected host trees in the wider environment.

Evaluation of Two Predictive Models for Forecasting Olive Leaf Spot in Northern Greece.

Olive leaf spot (Venturia oleaginea) is a very important disease in olive trees worldwide. The introduction of predictive models for forecasting the appearance of a disease can lead to improved disease management. One of the aims of this study was to investigate the effect of temperature and leaf wetness on conidial germination of local isolates of V. oleaginea. The results showed that a temperature range of 5 to 25 °C was appropriate for conidial germination, with 20 °C being the optimum. It was also found that at least 12 h of leaf wetness was required to start the germination of V. oleaginea conidia at the optimum temperature. The second aim of this study was to validate the above generic model and a polynomial model for forecasting olive leaf spot disease under the field conditions of Potidea Chalkidiki, Northern Greece. The results showed that both models correctly predicted infection periods. However, there were differences in the severity of the infection, as demonstrated by the goodness-of-fit for the data collected on leaves of olive trees in 2016, 2017 and 2018. Specifically, the generic model predicted lower severity, which fits well with the incidence of the disease symptoms on unsprayed trees. In contrast, the polynomial model predicted high severity levels of infection, but these did not fit well with the incidence of disease symptoms.

Temperature and incubation period affect Septoria pistaciarum conidium germination: disease forecasting and validation

Septoria leaf spot is an important disease of pistachio trees in Greece. This study aimed to determine effects of temperature and the incubation period on germination of conidia of Septoria pistaciarum, and to evaluate a generic model to forecast pistachio leaf spot under the field conditions of Aegina Island, Greece. The optimum temperature for conidium germination was 23°C, and germination was inhibited at 35 and 4°C. At constant temperature of 23°C, conidia commenced germination after 9 h. The predictive model indexed disease risk close to 100 at 10 May at two locations (Rachi Moschona and Vigla) in 2017, and first leaf spot symptoms were observed on 17 May. Moderate to high disease severity (>25% leaves infected) were observed in unsprayed trees at the end of May. In 2018, the model indexed risk close to 100 on 9 May at Rachi Moschona, and first symptoms were observed on 18 May. Moderate to high disease severity (>25% leaves infected) were observed in unsprayed trees on 25th of May. This study has shown that the forecasting model can be used in Aegina Island, Greece, to predict the severity of Septoria leaf spot of pistachio.

Flower pests of cashew, their seasonal incidence, damage and natural enemies

Different insect species attack cashew flowers during different phenological stages of the inflorescences from 511 to 619 of Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale of cashew phenology. A total of 67 species were documented during the investigation between 2016 and 2020. Among all pest groups, Lepidopterans were dominant comprising 32 species followed by Hemipterans with 22 species. The pests newly reported on cashew flowers include Perixera sp., Bombotelia jocosatrix, Gyrtona sp., Gatesclarkeana sp., Ascotis selenaria, Tinolius sp. besides two Cicadellids and two Lygaeid bugs. Damage symptoms, seasonal incidence and natural enemies were also documented for different pests. None of the weather factors had significant relationship with tea mosquito bug (TMB), B. jocosatrix and Lamida moncusalis. Though rainfall had no significant relationship with any of the pest population, number of rainy days had significant negative relationship with apple and nut borer (ANB) (-0.35), beetles (-0.35), thrips (-0.39) and mirids (-0.34). Parasitism by Trathala flavorbitalis on ANB was 15–30%, and by Apanteles sp. on Archips sp. was 20–25%. Reduction in nut set up to 47.06% has been recorded due to inflorescence pests in unsprayed trees compared to sprayed ones under mild infestation of TMB.

Kaolin-based particle film sprays reduce the incidence of pests, diseases and storage disorders and improve postharvest quality of ‘Delicious’ apples

Several pests and diseases infest apple during production, potentially causing heavy losses. Numerous pesticides are used to control pests and diseases, sprays of which contaminate the environment and result in pesticide residues. Among Good Agricultural Practices (GAPs), particle film technology (PFT) is promising for organic fruit production. Now some kaolin-based PFs such as Surround WP®, EclipseT, Anti-stress-500®, Parasol® have been developed which are available worldwide for commercial use. In India, preliminary research work was conducted for observing the effect of one kaolin-based PF (Surround WP®) on ‘Delicious’ apple. Five sprays of Surround WP® (3%) were applied to 20-randomly selected ‘Delicious’ apple trees each year during 2015–16 and 2016–17. The sprays were applied, starting on June 15 every year at fortnightly intervals and 20 unsprayed trees served as controls. Surround WP® reduced the incidence of San Jose scale (by ~ 64%), apple scab (by ~ 87%) and powdery mildew (by ~78%) significantly but increased the incidence of woolly apple aphid (by ~ 23%) compared to the control. Surround WP®- treated apples developed a better red color (Hunter ‘a’ value = 53.42 ± 0.42), increased anthocyanin content and improved appearance score. Surround WP® - treated apples were 35.4% firmer and contained a 49.9% higher Ca content compared to untreated fruit. Surround WP® treatment also showed significant improvement in soluble solids (increased by 10.5%) and ascorbic acid content (increased by 10.8%) with significant reduction in storage disorders such as bitter pit (reduced by 90.8%), brown core (reduced by 73.3%) and water core (reduced by 88.4%). Based on this study, Surround WP® can be recommended for organic production of ‘Delicious’ apples in Himachal Pradesh, India.

Application of alkylresorcinols in an organic apple orchard for protection against storage diseases

Each year, fungal storage diseases destroy large amounts of apple, especially in organic orchards. In the present study, antifungal activity of a rye bran-based remedy with 5-n-alkylresorcinols (ARs) was investigated. In 2014 and 2015, ‘Amorosa’ apple trees in an organic orchard were sprayed with a 0.025% AR emulsion pre-harvest, once or twice at different points in time. In addition, emulsions with different AR concentrations were applied postharvest on fruit inoculated with three different fungi (in vivo) and on fungal mycelium and conidia (in vitro). Fruits from trees sprayed in August and/or September had significantly less fungal decay in comparison with fruits from unsprayed trees, both at harvest and after storage in regular air and in controlled atmosphere condition (CA). Effects on fruit quality were small and inconsistent whereas yield was significantly reduced, especially after early-season applications (June, July). Yield was, however, similarly reduced when a reference emulsion without ARs was applied suggesting that this effect was not brought about by the ARs. The in vivo and in vitro experiments showed that anti-fun-gal activity increased with higher AR concentrations. Further experiments with late-season applications and higher AR concentrations should be undertaken. (Less)

Pre-harvest spray application of prohexadione-calcium and paclobutrazol improves rind colour and regulates fruit quality in M7 Navel oranges

Abstract Sweet orange (Citrus sinensis L. Osbeck) cv. ‘M7’ Navel exhibits poor flavedo colour at harvest in Western Australia. Gibberellins are known to retard fruit colour development in citrus fruit, therefore the efficacy of different concentrations and timings of spray applications of two inhibitors of gibberellin biosynthesis such as prohexadione calcium (Pro-Ca) and paclobutrazol (PBZ) on flavedo colour development and fruit quality was investigated. The effects of an aqueous solution containing different concentration of Pro-Ca (200, 400, 600, 800, 1200, 1600 or 2000 mg L−1), and PBZ (100, 250, 500, 1000, 1500 and 2000 mg L−1) sprayed at 6 or 3 weeks before anticipated harvest (WBAH) on flavedo colour development particularly from yellow to deep orange and on the fruit quality were investigated during 2015 and 2016. Unsprayed trees were kept as control. The spray application of Pro-Ca (800 mg L−1) resulted in decreased hue angle (h°) (57.5), and increased citrus colour index (CCI) (10.2) and, total carotenoid levels (38.3 mg kg−1) in the flavedo during 2015. Furthermore, Pro-Ca (600 or 800 mg L−1) showed enhanced levels of total carotenoids (39.2 and 38.3 mg kg−1) respectively, during 2015. In 2016, a single spray application Pro-Ca (1200 mg L−1) at 3 WBAH exhibited reduced h° (56.6) and increased CCI (10.7), and levels of total carotenoids (36.8 mg kg−1) as compared to the control. Additionally, a single spray application of Pro-Ca (800, 1200 or 1600 mg L−1) was able to increase total carotenoids in the flavedo (32.7, 36.8 or 33.1 mg kg−1) respectively. In 2016, Pro-Ca (800 mg L−1) exhibited increased SSC (13.0%) and reduced TA (1.08%) in the fruit juice. A single spray application of PBZ (1000 mg L−1) at 6 WBAH significantly reduced h° (56.7) and increased CCI (10.6) and levels of total carotenoids in the flavedo (42.6 mg kg−1). However, a single spray application of PBZ (1500 mg L−1) at 3 WBAH showed lower h° (55.4) and enhanced CCI (11.2) and level of total carotenoids (47.1 mg kg−1) in the flavedo during 2016. In conclusion, pre-harvest spray application of Pro-Ca (800 and 1200 mg L−1) applied at 6 and 3 WBAH respectively enhanced fruit colour. A single pre-harvest spray application of PBZ (1000 and 1500 mg L−1) applied at 6 and 3 WBAH respectively improved fruit colour in early maturing ‘M7’ Navel.

Effect of plant growth regulators on leaf area, chlorophyll content, carotenoids, stomatal count and yield of cashew (Anacardium occidentale L.) var. Bhaskara

<p>An experiment was conducted to study the effect of exogenous application of growth regulators at three important growth stages<br />(flushing, flowering and fruiting) on leaf area, chlorophyll content, carotenoids, stomatal count and yield of cashew var. Bhaskara.<br />Irrespective of growth stages, foliar application of GA3 @ 50 ppm and ethrel @ 50 ppm was found to be superior in all the<br />parameters and on par with each other compared to other growth regulators. Out of nine treatments of different growth regulators;<br />the highest leaf area was recorded in trees sprayed with GA3 @ 50 ppm and ethrel @ 50 ppm. At flushing stage, spraying with GA3<br />@ 50 ppm resulted in highest stomatal number (21.9) and carotenoids (0.41) whereas unsprayed (control) trees recorded least<br />stomatal number (11.6) and carotenoids (0.19). Thus, leaf area, chlorophyll content, carotenoids and stomatal count increased in<br />trees sprayed with growth regulators than unsprayed trees. Spraying of ethrel @ 50 ppm recorded highest nut yield<br />(14.3 kg tree-1) followed by NAA @ 25 ppm + GA3 50 ppm (12.9 kg tree-1). This study demonstrated the potential of ethrel as well<br />as GA3 in improving various biochemical parameters viz., chlorophyll ‘a’, chlorophyll ‘b’, carotenoids and leaf area in cashew<br />which are important determinants in increasing nut production.</p>

Anthracnose Caused by Colletotrichum horii on Sweet Persimmon in Korea: Dissemination of Conidia and Disease Development

AbstractAnthracnose disease caused by Colletotrichum horii (C. gloeosporioides), results in considerable economic damage to sweet persimmon in southern Korea yearly. This study deals with the life cycle of the pathogen in terms of seasonal fluctuations of spore dispersal and the development of disease based on field surveys, spore potential and fungal isolation. Anthracnose disease was observed first on twigs in the last week of May and reached an incidence of 1.2%. Subsequently, the disease increased rapidly and reached an incidence of 86% by the end of July. Infection of fruits started in mid‐June (2.8%) and increased gradually to 64.4% by the end of July. In severely infected orchards, 46.2% of diseased fruits were dropped. The pathogen began releasing conidia in the first week of May and continued until the end of September. The maximum release of spores was observed in mid‐July. To determine the optimal use of chemicals for control of anthracnose, the following spray programme was evaluated. Spraying two or three times resulted in 89.4 and 93% control, respectively, whereas spraying more than four times led to 100% control. In comparison, the disease rate of unsprayed trees was 89.8%. To control anthracnose effectively, it is recommended to take steps to eliminate inoculum sources in sweet persimmon orchards before spraying chemicals.

Unexpected diversity during community succession in the apple flower microbiome.

ABSTRACTDespite its importance to the host, the flower microbiome is poorly understood. We report a culture-independent, community-level assessment of apple flower microbial diversity and dynamics. We collected flowers from six apple trees at five time points, starting before flowers opened and ending at petal fall. We applied streptomycin to half of the trees when flowers opened. Assessment of microbial diversity using tag pyrosequencing of 16S rRNA genes revealed that the apple flower communities were rich and diverse and dominated by members of TM7 and Deinococcus-Thermus, phyla about which relatively little is known. From thousands of taxa, we identified six successional groups with coherent dynamics whose abundances peaked at different times before and after bud opening. We designated the groups Pioneer, Early, Mid, Late, Climax, and Generalist communities. The successional pattern was attributed to a set of prevalent taxa that were persistent and gradually changing in abundance. These taxa had significant associations with other community members, as demonstrated with a cooccurrence network based on local similarity analysis. We also detected a set of less-abundant, transient taxa that contributed to general tree-to-tree variability but not to the successional pattern. Communities on trees sprayed with streptomycin had slightly lower phylogenetic diversity than those on unsprayed trees but did not differ in structure or succession. Our results suggest that changes in apple flower microbial community structure are predictable over the life of the flower, providing a basis for ecological understanding and disease management.

Factors influencing flower bud formation on the pear tree cultivar 'Doyenne du Comice'. I. Shoot growth and flower bud differentiation on trees sprayed with chlormequat and unsprayed ones

The growth of trees sprayed in spring with chlormequat is weaker, and their elongation growth ends 2 - 3 weeks earlier than that of unsprayed trees. Trees with growth inhibited by chlormequat set flower buds on the spurs and in the subapical part of long shoots. The course of flower bud differentiation starts in the second half of July and is similar to that in the apple tree.

Management of Powdery Mildew on Flowering Dogwood with Soybean Oil

Abstract Soybean oil formulations developed in our laboratory were evaluated for control of powdery mildew on flowering dogwood Cornus florida. In a preliminary trial in a field nursery, two formulations, TNsoy1 and TNsoy2 [0, 1 or 2% (v/v)], were applied to field-grown flowering dogwood at 2 wk intervals from June 10 until August 19. Soy oil-treated trees had less powdery mildew, higher net photosynthetic rate and growth rate than unsprayed trees, without apparent phytotoxicity. Leaves sprayed with Banner MAXX had less powdery mildew and higher photosynthetic rates than oil treated leaves. These same treatments applied the next year under more frequent rain showers did not provide satisfactory control. Newer soybean oil formulations using natural or food grade emulsifiers, were compared to three commercial botanical oil formulations and to SunSpray Ultra Fine Oil in greenhouse trials. All oil formulations provided some protective and eradicative control of powdery mildew. Photosynthesis of oil treated leaves was usually depressed, compared to controls, for several days but recovered. In greenhouse trials where the oil was not washed off by rain or irrigation, the oil residue was visible on leaves, reduced powdery mildew severity, and depressed photosynthesis for several weeks. In a second greenhouse trial, soybean oil formulations provided greater control if applied after rather than before initial inoculation.

Feathering of ‘Doyenné du Comice’ pear in the nursery using repeat sprays of benzyladenine and gibberellins

This work sets out to examine the effectiveness of a number of cytokinins or products with cytokinin-like activity, with and without additional sprays of gibberellins or leaf plucking, on the production of feathers (sylleptic shoots) on trees of the European pear cultivar ‘Comice’ in a fruit tree nursery. It covers the results from three successive years experimentation. In year 1, unsprayed trees of ‘Comice’/quince C (QC) had an average of 1.6 useful feathers per tree. Three applications of 1000–2000 mg L −1 benzyladenine (BA) followed by three applications of 400 mg L −1 GA 4+7 resulted in over a fourfold increase in the number of feathers and a fivefold increase in the total length of feathers. Thidiazuron (TDZ) applications of 30–40 mg L −1 followed by three applications of 400 mg L −1 GA 4+7 also resulted in an increase in feathering but were not as effective as BA sprays. Both spray treatments resulted in more spines on the trees. In year 2, feathering of ‘Taylor's Gold Comice’/QC was enhanced by three BA sprays at 1500 mg L −1, followed by three sprays of GA 4+7 at 400 mg L −1. Leaf plucking tended to improve feathering in the absence of GA 4+7. BA sprays were more effective than sprays of TDZ at the concentrations used (30 and 60 mg L −1). Sprays of GA 4+7 without the use of cytokinins also stimulated feathering. Thorniness was linked with the use of GA 4+7, not the cytokinins. In year 3, feathering of ‘Comice’/QC was enhanced by combinations of BA and GA (GA 3 or GA 4+7) sprays (four sprays of each applied sequentially) and these resulted in large, well-feathered trees. Thorniness was associated with the use of gibberellins rather than cytokinins. Thorniness was not reduced by the use of GA 3 over the use of GA 4+7; in fact it was made worse. However, GA 3 was more effective at inducing feathering than GA 4+7, so a similar thorniness score and feathering could be achieved by using 200 mg L −1 GA 3 as achieved with 400 mg L −1 GA 4+7. GA 3 is additionally a cheaper product. Sprays of GA without the use of BA also stimulated feathering, although the height of these feathers in the tree were too high for commercial use because these sprays of GA were applied four weeks later than the BA sprays. Therefore, GA sprays applied earlier in the tree development may be sufficient to feather ‘Comice’ in the absence of BA.

Comparative Efficacy and Economic Viability of Trichoderma Strains as Bio-Control Agents for the Control of Phytophthora Pod Rot of Cocoa in Nigeria

The comparative efficacy and economic viability of Trichoderma species as bio-control agents against Phytophthora megakarya which has been hitherto elusive was determined by field application/evaluation, bean yield and accruable revenue evaluation. The trials followed randomized complete block design (RCBD) with 3 field constituting blocks, 24 treatments with 3 trees per treatment per replicate. The treatments were three fungicides, five bio-agents, fifteen combinations of fungicides and bio- agents while the control consists of unsprayed trees. Data were collected on total pod produced (TP), total number of disease pods (DP) and total number of fermentable pods per tree per treatment (FP) while revenue accrued (RA) and revenue-cost-ratio were also determined accordingly. All the bio-agents significantly reduced the percentage pod-rot on the field. The highest mean pod-rot incidence (16.91) among the treated was significantly lower than the control (30.14). This was observed on BA (NIG-T287) sprayed plots. Funguran 0H + NIG-T289 produced the highest (757) number of pods while the least pod production (312) was observed with Copper Sulphate + NIGT289 (F3BC) treated plots. The highest revenue-cost-ratio (69.45) was obtained from Copper Sulphate treated plots, while the least revenue-costratio (2.85) was obtained from Ridomil Gold + NIG-T288 treated plots. NIGT293 performed better than other bio-agents and most of other treatments when applied sole resulting to 45.90 comparative efficacy and economic viability. These bio-agents were successfully combined with fungicides thereby reducing the frequency of fungicide application from four to one with significant pod-rot reduction on the field, comparatively high yield and more profit (high revenue-cost-ratio).Keywords: Bio-control agents, comparative efficacy, economic viability,revenue-cost-ratio.