Early Fruit Drop Research Articles

The Incidence of Root-Knot Nematodes Meloidogyne arenaria, M. incognita, and M. javanica on Vegetables and Weeds in Montenegro.

Root-knot nematodes (Meloidogyne spp.) are common pathogens that parasitize vegetables and other crops and cause significant yield reductions worldwide. In the early spring of 2006, severe plant stunting, chlorosis, and extensive root galling were observed on cucumber plants grown in a greenhouse on Zeta plain, Zetska ravnica, Montenegro. In the summer and autumn of 2006, infected roots of different crops were collected from greenhouses and vegetable production fields of Zeta plain, which represents the largest area of Montenegro's vegetable production. Several vegetable crops were found to be infected with root-knot nematodes, including tomato (Lycopersicon esculentum Mill.), squash (Cucurbita pepo L.), cucumber (Cucumis sativus L.), pepper (Capsicum annuum L.), and lettuce (Lactuca sativa L.). Symptoms on these crops included root-galling, leaf chlorosis, and stunting. Heavily infected tomato plants growing in two greenhouses also displayed early flower and fruit drop. Nematode species were determined based on characterization of (i) female perineal patterns, (ii) male and second-stage juvenile morphology (2,3), and (iii) esterase and malate dehydrogenase phenotypes (PhastSystem; Amersham Biosciences, Piscataway, NJ) from young egg-laying females (1). The most prevalent species was M. incognita, which was isolated from the roots of tomatoes, peppers, cucumbers, and lettuce from nine locations. Meloidogyne arenaria was detected at three locations from the roots of tomatoes grown in a greenhouse and the weeds Convolvulus arvensis L. and Solanum nigrum L., which were growing in open fields in separate locations. M. javanica was found on tomato and squash in the same field where M. arenaria was also found on S. nigrum. M. javanica was isolated from tomato and squash. In this study, we found high incidence of Meloidogyne spp. in intensive vegetable production areas of Montenegro. The implementation of an effective integrated pest management program is essential for future use of infested areas. To our knowledge, this is the first report of M. arenaria, M. incognita, and M. javanica from Montenegro.

Produção da laranjeira-de-umbigo 'Monte Parnaso' com incisão anelar de ramos e uso de reguladores vegetais

A laranjeira-de-umbigo 'Monte Parnaso' (Citrus sinensis [L.] Osbeck) tem produtividade inferior a 10 kg de frutos/planta, em função de baixa fixação e/ou retenção de frutos. Com o propósito de solucionar esse problema, no ano agrícola de 2001-2002, plantas com 11 anos de idade, enxertadas sobre Poncirus trifoliata (L.) Raf., em Butiá, Rio Grande do Sul, foram submetidas aos seguintes tratamentos: 1) Testemunha: sem anelagem e sem reguladores vegetais; 2) Incisão anelar da casca dos ramos principais, 10 dias após a queda das pétalas (02-10-2001); 3) Incisão anelar da casca dos ramos no final da queda natural de frutos (08-11-2001); 4) Pulverização com 5 mg.L-1 de ácido giberélico (AG3), 10 dias após a queda das pétalas (02-10-2001); 5) Pulverização com 15 mg.L-1 de ácido 2,4 diclorofenoxiacético (2,4-D), no final da queda natural dos frutos (08-11-2001); 6) Pulverização com 50 mg.L-1 de ácido diclorofenoxipropiônico (2,4-DP), no final da queda natural dos frutos (08-11-2001); 7) Pulverização com 10 mg.L-1 de AG3 + 15 mg.L-1 de 2,4-D, em maio (14-05-2001 e 11-05-2002); 8) Tratamentos 2 + 3, e 9) Tratamentos 2 + 3 + 7. O delineamento experimental adotado foi em blocos ao acaso, com 5 repetições, usando 3 plantas úteis por parcela. A pulverização com 5 mg.L-1 de AG3, 10 dias após a queda das pétalas, aumenta a produção, mas diminui a massa média dos frutos em relação a outros tratamentos que aumentam a produção, e a pulverização no final da queda natural com 15 mg.L-1 de 2,4-D diminui o teor de suco dos frutos. Para aumentar a produção de frutos, basta adotar-se um dos seguintes procedimentos: em novembro, após a queda natural dos frutos, fazer a incisão anelar da casca dos ramos, ou pulverizar as plantas com 15 mg.L-1 de 2,4-D, ou pulverizar as plantas com 50 mg.L-1 de 2,4-DP; ou em maio, pulverizar as plantas com 10 mg.L-1 de AG3 + 15 mg.L-1 de 2,4-D.

Cultural Practices that Impact Stone Fruit Quality

Quality of stone fruit is defined by fruit size, color, firmness, flavor, shape, general appearance, adhesion and size of the stone and fruit surface characteristics (e.g. fuzz, abrasions, pest damage). Cultural practices, such as pruning, nutrition, irrigation, growth regulator usage and pesticide applications can influence these quality characteristics to a greater or lesser extent. Adequate potassium nutrition can improve soluble solids and fruit size in plums. Excess nitrogen fertilization can soften peaches. Well-timed calcium sprays are thought to improve the firmness of sweet cherries, as are applications of gibberellin. Ethylene synthesis inhibitor usage can alter the timing of ripening, reduce early fruit drop and improve storage. Irrigation scheduling is a tool that can be used to regulate final fruit size and firmness, as well as time of maturation. Selective pruning is used to structure a tree's architecture for improved light penetration to improve fruit size and color. These and other production practices will be discussed in relation to how they affect fruit quality in stone fruit.

Fruit and spur leaf growth and quality as influenced by low irradiance levels in pear

The effects of shading on spur leaf and fruit growth and quality of Pyrus communis L. cv. `Bartlett' were evaluated in the High Valley region of Argentina. The trees were trained to palmette leader and fruit load was low. Treatments were application of shade using a 80% saran shade cloth, applied at two stages of fruit development: 2 October–3 December 1996 (14 days after full bloom (DAFB) to 76 DAFB, Stage I) and 3 December 1996–23 January 1997 (76–128 DAFB, Stage II). Meteorological data were continuously monitored. Shading during Stage I decreased area per spur leaf, specific leaf mass and fruit diameter by 16.70%, 20.88% and 10.80%, respectively, at 76 DAFB. There was no significant treatment effect on final fruit size, although shaded fruits tended to be smaller. Microscopic examinations showed contrasting anatomical features in leaves that were exposed to different light regimes. Induction of early fruit drop by cloth-covering individual branches during Stage I was also demonstrated here. Shading during Stage II yielded significantly ( P≤0.05) smaller fruits as compared to control and light reduction did not affect fruit firmness and soluble solids concentration. It was concluded that early shading reduced spur vigor and fruit load, whereas late shading diminished fruit size. These results suggest some goals of pruning and training for optimizing yield, by efficiently converting captured sunlight into fruit.

Immunogold localization of trans-zeatin riboside in embryo and endosperm during early fruit drop of Malus domestica

The specificity of a monoclonal antibody IgG1, raised against trans-zeatin riboside-keyhole limpet hemocyanin conjugate, was investigated by means of inhibition experiments with soluble competing antigens. A competitive enzyme immunoassay was set up, with immobilized antigen. The analysis of the cross reaction profile enabled a study of the specificity of the antigen-antibody interaction. The antibody was able to distinguish the trans form of zeatin riboside from the cis form (cross reaction index = 1 %); cross reactions with ribose, adenine, adenosine and other related heterologous antigens were not detectable over the range of concetration tested. The recognition centres for the antibody seem to be the purine ring and the R substituent, especially in its hydroxymethyl group. Employment of this monoclonal antibody to localize cytokinins in control and shedding affected fruits of Malus domestica Borkh. evidenced high content of trans-zeatin riboside in developing seeds, differences in its content in embryo and endosperm, and a strong reduction of its content in the tissues of drop fruits. This decrease may be an important component responsible for early fruit abscission.

Early fruit drop in tree crops with special reference to rubber (Hevea brasiliensis) — A review

Early fruit drop in tree crops with special reference to rubber (Hevea brasiliensis) — A review

Early fruit drop in tree crops with special reference to rubber (Hevea brasiliensis) ‐ A review

AbstractThe present article surveys the possible reasons for early fruit drop in tree crops with special reference to rubber. They are environmental, physiological, embryological or pathogenic. Abortion of pistillate flowers and fruit occurs generally in three distinct periods: due to under developed flowers, failure of pollination and embryo abortion due to embryological and physiological factors. Fruit set can be increased by hand pollination, use of growth hormones or by the application of fertilizers. The failure of seed production results in the loss of numerous potentially good cross combinations thus limiting the progress of genetic improvement of the species. Moreover seeds are the rich sources of genetic variability.

Control of Dacus oleae, a major pest of olives

Dacus oleae (Gmelin) is a major pest of the olive tree Olea europea causing early fruit drop, ‘sting’ damage to table olives and substantial decreases in the quantity and quality of oil. This review describes the control strategies being developed and in current use—biological, trapping methods, sterile insect release, chemical insecticides, growth regulators and integrated control. Present problems and the implications of the controlling regimes on the disturbance of the agroecosystem are presented. Emphasis is given to newer methods which should be characterized by their specificity and effectivity.

リンゴの早期落果に関与する気象要因の解析と栽培管理

The early fruit drop of ‘Starking Delicious’, ‘Mutsu’, ‘Redgold’ etc. occurred largely in the north of Akita prefecture in 1978. We tried to clarify the effects of weather conditions on the early fruit drop by investigating the weather conditions in 1978, and analyzing statistically the relationship between those in 1979-1985 and the rate of early fruit drop.In 1978, early fruit drop occurred from the 36th day after full bloom. From the 31st day after full bloom the maximum and minimum temperatures were much higher, from the 27th day to the 38th day after full bloom the duration of sunshine was less and the precipitation was more than the mean value of the previous 10 years.The rate of early fruit drop in 1979-1985 was closely correlated with the weather conditions around the 30th day after full bloom; the multiple regression equation which expresses the rate of early fruit drop was obtained using the minimum temperature, the duration of sunshine and the precipitation from the 28th day to the 34th day after full bloom. From these results, it was shown that the early fruit drop was induced by a higher minimum temperature and less sunshine.We also investigated the effects of tree vigor and pruning on the early fruit drop. To estimate the vigor of each tree, elongation of the terminal shoot was measured regularly and the mineral constituents of leaves were analyzed. The rate of early fruit drop was increased in both vigorous and weak trees, and was closely correlated with the elongation of the terminal shoot. Similar results were observed in heavily pruned trees, that is, heavy pruning increased the elongation of the terminal shoot and early fruit drop.

リンゴの早期落果と新梢生長との関係

Early fruit drop of ‘McIntosh’ apple was enhanced by night temperatures of 25°C. The relationship between this fruit drop and shoot growth was investigated.Shoots grew more vigorously as the temperature rose, with fruit drop occurring simultaneously. It was concluded that early drop of fruit occurred because of competition with shoots for reserve substances. Shoot growth was inhibited by spraying with N-dimethylaminosuccinamic acid (SADH) and fruit set was increased. Shoot tipping treatment also increased the number of fruit retained through the “June drop” period. These two treatments increased fruit set by reducing competition between fruits and shoots.Spraying with BA markedly increased the number of shoots and the frequency of fruit drop. The increase in early drop of fruit was probably due to severe competition from shoots which was enhanced by BA.Spraying of GA4/7 increased fruit set at 50, 100 and 500ppm, whereas shoot growth was promoted at 500ppm of GA4/7, but inhibited at 50 and 100ppm of GA4/7.

リンゴの早期落果とエチレン生成及び離層形成との関係

Early fruit drop in ‘McIntosh Red’ apples was enhanced by 30 days of high night temperature (25°C) beginning on the 10th day after full bloom. A reduced rate of fruit enlargement for two days indicated the imminence of fruit drop; abscission occured 6 to 10 days later. The fruit drop process was divided into four stages stage A, potential fruit drop as indicated by the reduced rate of fruit enlargement; stage B, two days after potential fruit drop; stage C, four days after potential fruit drop; stage D, abscission. There was no difference in ethylene evolution between fruits of stage A and persistent fruits. However, the stage of fruit drop advanced from B to C, ethylene evolution increased. Few fruit at stage A had formed an abscission layer but those which had, evolved more ethylene than those which had not. These results suggest that ethylene evolution and abscission layer formation are not the primary factors causing the early drop of apple fruit but are part of the ageing process which occurs with the advance of the fruit drop process.

Compensation for early fruit drop caused by Dacus oleae (Gmel.) (Diptera, Tephritidae) due to an increase in weight and oil content of the remaining olives

AbstractThe experiments were carried out on two varieties of olive trees under irrigated and non irrigated conditions in Crete, Greece. Fruit drop, as it is caused by D. oleae, was simulated by picking up to 50% of all olives in either August or September from entire trees or from marked branches. From August up to harvest in November‐December, olives on treated trees and branches increased their weight by 5% over the untreated control. In Tsounati olives, especially, this compensation for fruit loss earlier in the season increased linearly with the amount of olives removed. At the same time, the bigger olives had a 5% higher relative oil content. Similarly, this compensation for oil increased with the proportion of olives removed. For olives removed in September, however, compensation through weight increase reached only a non significant 3%, as compared to about 5% for the increase in oil content. Overall, compensation was estimated at 10% for olives lost in August and 5% for those lost in September. It is concluded that 10% of the fruit drop attributable to the first generation of D. oleae in June‐July can be compensated for by the tree. By adding 1% for treatment costs early in the season, it is proposed to set the economic threshold for June‐July at 11% damage, a value which, under Chania conditions, is rarely attained. Consequently the intervention threshold can be lifted considerably over the current practice. This should reduce the amount of insecticide used, and hence alleviate the pressure on predators and parasites, especially those of scale insects.ZusammenfassungKompensation für frühen, von Dacus oleae (Gmel.) (Diptera, Tephritidae) verursachten Fruchtfall, durch Größenzunahme und höheren Ölgehalt der verbliebenen OlivenDie Versuche wurden an zwei Olivenvarietäten unter bewässerten und unbewässerten Bedingungen in Kreta, Griechenland, durchgeführt. Fruchtfall, wie er von D. oleae verursacht wird, wurde dadurch simuliert, daß im August oder September bis zu 50% aller Oliven ganzer Bäume oder einzelner Äste gepflückt wurden. Von August bis zur Ernte im November‐Dezember erreichten Oliven von behandelten Bäumen oder Ästen ein um 5% höheres Fruchtgewicht als diejenigen der unbehandelten Kontrolle. Besonders bei Tsounati‐Oliven nahm diese Kompensation linear mit dem Anteil vorzeitig gepflückter Oliven zu. Gleichzeitig wiesen diese größeren Oliven einen um 5% höheren relativen Ölgehalt auf. Auch diese Form von Kompensation nahm mit steigender Menge entfernter Oliven zu. Für Oliven, welche im September entfernt wurden, andererseits, erreichte die Kompensation durch Gewichtszunahme nur nicht signifikante 3% verglichen mit 5% für die Ölgehaltssteigerung. Gesamthaft wurde eine Kompensation von 10% für Olivenverluste im August und von 5% für solche im September errechnet. Es läßt sich folgern, daß 10% des Fruchtfalls, der der ersten D. oleae‐Generation im Juni‐Juli zugeschrieben wird, durch den Olivenbaum kompensiert werden kann. Nach Hinzufügen von 1%, entsprechend den Kosten einer Insektizidbehandlung, läßt sich so für Verluste im Juni‐Juli eine Schadenschwelle von 11% errechnen, ein Wert, der unter den Bedingungen in Chania nur selten erreicht wird. Das bedeutet aber, daß eine Behandlung erst bei höherer D. oleze‐Dichte als heute üblich, gerechtfertigt ist. Das Ansetzen einer höheren Schadenschwelle sollte dabei zu einem verminderten Insektizidverbrauch führen und so den Druck auf Räuber und Parasiten, besonders von Schildläusen, vermindern.

An Effect of Kinetin on the Translocation if 14C-Labelled Photosynthate in Citrus

This study indicates that the application of kinetin to a recently formed fruit enhances its ability to import photosynthetic assimilates. Cytokinins are known to influence .the transport of plant metabolites (Letham 1967), and in the case of vine shoots Shindy and Weaver (1967) have recently demonstrated an effect of the kinin 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine on the translocation of 14C_ labelled assimilates. The present paper reports an effect of kinetin (6-furfurylaminopurine) on the accumulation of14C-labelled substrates by citrus fruits (cv. Washington Navel). In such crops the newly formed fruitlet is often unable to compete successfully with adjacent expanding leaves for substrates and this is thought to result in early fruit drop (Haas 1949; Sauer 1954).