Two-year-old potted ‘Tosa Buntan’ pummelo (C.grandis (L.) Osbeck) trees grown in a plastic house (PH) were used in this trial. The trunk 15 cm above the graft union was strangulated with 1.6 mm diameter wire at a tension of about 30 Kgf. cm every month from August to November 1990. The duration of the strangulation treatment was 2 months for each treating time. Defoliation was severe and many leafless flowers sprouted at the upper part from the strangulation position (UP) during the winter season. All flower buds were thinned and defoliated previous shoots were pruned in early March 1991. New leafy flower buds resprouted at the UP. The number of flower buds and fruit set were higher at the UP than at the lower part (LP) . The recovery degree of girdle formed after the release of wire ring by mid-May was high in all treatments except for August treatment. Leaf number and area at the UP in mid September increased as the strangulation time was delayed, nonetheless, both were highest in control trees. The photosynthetic rate at the UP was the lowest in the control trees in mid-September and the highest in late November except for November treatment. Total sugar and carbohydrate contents in late August were increased as the strangulation time became early. On the contrary, nitrogen content was decreased and C/N value was increased as the treating time became early. November treatment produced larger fruit, while other treatments did not differ with the control trees. Coloration of fruit rind was improved in treated trees; however, no significant difference in TSS and acid contents was observed among treatments. The numbers of inflorescences and flower buds were higher in the treated trees than in the control trees and fruit set was not affected in the second year. Yield was lower in strangulated trees in the first year, but it was higher in the second year. Thus, the total yield in two years excluding the August treatment was 19-25% higher in strangulated trees than in the control one.

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By the application of a mixture of charcoal with pyroligneous acid (charcoal 4: pyroligneous acid 1; Sannekka E, Miyazaki Midori PHARMS....IMC), the stalk number and length surpassed those of the control plots in both spring and ratoon crops, and the total dry matter weight and cane yields at the final f arvest were significantly higher in the ratoon crops. The sugar content and yield of the Sannekka E (SE) treated crops were much higher than those of the control crops in both cropping types. CGR and LAI showed significant changes throughout the growth stages by SE application. The highest stalk and sugar yields were obtained by the application of SE of 400 kg/la in both cropping types. Therefore, it is suggested that SE application affects significantly cane and sugar yields.

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The relationship was investigated between fruit weight of loquat (Eriobotrya japonica LINDL. cv. Mogi) and some factors such as the number of days to ripening, heat summation from flowering to ripening, number of seeds, seed weight, number of leaves on the bearing shoot and the climatic conditions. The fruit weight was the largest, when the number of days to ripening and the heat summation from flowering to ripening was 150-180 days and 2, 000-2, 100°C day-degrees, respectively. Also, the number of seeds and seed weight quadratically correlated with fruit weight. The temperatures for 31-60 days after flowering, 31-60 days before ripening (DBR), 0-30 DBR and 0-60 DBR quadratically correlated with fruit weight. Consequently, the most influential factor affected fruit weight was the seed weight after a multiple linear regression analysis was conducted. The temperatures for 31-60 DBR, the number of days to ripening and heat summation from flowering to ripening were the secondary influential factors related to fruit weight.

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After the burst of ethylene production, changes in mechanical properties of banana [Musa (AAA group, Cavendish subgroup) “Giant Cavendish”] pulp were detected by the application of a stress-relaxation technique, which suggested that the decrease in the viscosity and elasticity of the pulp was the major physical factor for the pulp softening. The amount of starch and pectic and hemicellulosic polysaccharides of the cell walls decreased and the amount of soluble sugars increased, while the cellulose content did not change. Gel filtration chromatography revealed more clearly that the partial degradation of pectic polysaccharides preceded the conspicuous decrease in the amounts of sugars. These results suggest that the sequential degradation process of pectic and hemicellulosic polysaccharides and starch is the main cause of pulp softening.

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We investigated the development of the inflorescence of castor-oil plants in order to know the process of determination of the number of dichasia of a inflorescence and the number of fruits per dichasium. The dichasium primordia differentiated on the inflorescence axis in ascending order. The differentiation of the dichasium primordia was finished by the differentiation of the flower primordium (the topmost dichasium) at the apex of the inflorescence axis. It took a short period to finish the differentiation of dichasium primordia. For instance, it took a period corresponding to P.I.1 or 4 days in the plants which have five leaves in total before inflorescence on the main stem. In a dichasium, flower primordia differentiated in order of the flowering order of the dichasium. The differentiation of new flower primordia did not last till the anthesis stage. In this study, it was finished at the stage a period corresponding to P.I.2 or twelve days before the start of anthesis. The highest order flowers of a dichasium at this stage were the first order in the topmost dichasium, the third order in the second dichasium, the fourth order in the lowest female dichasium and the fifth to sixth order in the lowermost dichasium (male dichasium) . It was shown that all differentiated flowers did not bloom usually.

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1. Rooted cuttings of fig tree cvs. Masui Dauphine and Horaishi were treated with 0, 20, 40 and 60 mM NaCl solutions for 6 weeks at 30/25°C. With the increase of the NaCl concentration, shoot growth was markedly inhibited and the accumulation of Na and Cl ions into leaves and stems increased; however, no salinity injury was caused by any of the treatments. This suggests that fig trees be endowed with some tolerant mechanisms to high saline conditions. Photosynthetic rate showed a negative correlation with both the Na and Cl contents in the leaves. Growth inhibition under saline conditions appears to be caused by the ecrease of photosynthesis.
2. Rooted cuttings of ‘Masui Dauphine’were treated with 0, 20, 40, and 60 mM NaCl solutions for 6 weeks, and then irrigated with tap water for the following 30 weeks at 30/25°C. During the NaCl treatment, tree growth and the photosynthetic rate were reduced more conspicuously with the increase of the salinity level. After the discontinuation of the salinity treatment, photosynthesis recovered gradually, but shoot growth stopped until the 24th week in all the plots. At 20 and 40 mM a larger number of flower buds were formed on the new shoots with the resumption of growth.

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Possibility of seed multiplication for photoperiod-sensitive rice varieties was examined under the subtropical climatic conditions of Ishigaki Island, Okinawa, Japan. When sown in July and transplanted to paddy fields in August, relatively strongly photoperiod-sensitive varieties which headed until November 20th after being sown in May in the plant quarantine greenhouse at Tsukuba city, Ibaraki, produced seeds with a short growth duration. Strongly photoperiod-sensitive varieties which headed after November 20th at Tsukuba gave fully sterile seeds.

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Plantains [Musa (AAB group, plantain subgroup) Horn type plantain, ‘Tundoc’] were used for physical and chemical analysis during fruit softening. After the ethylene treatment, changes in the mechanical properties of the pulp were analyzed by a stress-relaxation technique, suggesting that the decrease in viscosity and elasticity of the pulp was a crucial physical event in pulp softening. Sugar content of the starch, pectin and hemicellulose fractions from the plantain pulp decreased during ripening, while that of the cellulose fraction remained unchanged. The decrease in the pectin and hemicellulose contents followed the same pattern as that of firmness parameters, while the starch content decreased rapidly. The results suggested that cell wall polysaccharides, pectin and hemicellulose are the chemical components responsible for the changes in firmness rather than starch in plantain pulp.

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In the sparsely populated areas of Papua New Guinea, namely, Telefomin, Lumi, Nuku and Sowam areas, traditional cultivations and cropping patterns were surveyed over a period of 3 months in total from 1991 to 1993. In this report a part of the results is described with emphasis placed on analyzing the rational diversity of traditional cultivation systems in the study areas. In Telefomin, a humid area at a high altitude, the land was cleared without using fire. Some broadleaf trees remained after the clearing to protect the soil surface from raindrop erosion and the soil was mulched with fallen leaves of the trees. Main food crops consisted of taros and bananas. In Lumi, a hilly area with a relatively high humidity, the land was fully cleared to dry the garden. The crops were diversified and the main food crop was sago. In the relatively dry and undulating Nuku area at the foot of mountains, some trees remained after the clearing and were used as support for yam's vines and for protecting soil from erosion. Sowam area is located on the coast and is connected by road to the provincial capital. Cash crops were cultivated in permanent gardens. The gardens in the shifting cultivation systems were used relatively intensively and the crops were highly diversified. The results of the analysis are as follows. 1. Cultivated crops were selected according to the natural conditions. 2. In taking account of the need to preserve the natural forest, the garden environment was modified to make it more suitable for cropping. 3. Protection measures from soil erosion were taken to sustain the productivity of crops to achieve self-sufficiency. 4. In areas where crops were not diversified, a large number of varieties of a few crops were cultivated to maintain the self-sufficiency in food supply and to satisfy the feed habits of the inhabitants. 5. In the study areas, the diversity of crops was inversely proportional to the varieties of a crop, but proportional to the accessibility to cities or the existence of sago palms as a source of food.

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Development of shoot and root under different air temperature conditions was examined to enhance the young plant growth in sugar cane. The number of set roots was not influenced by different as in the air temperature in the range of 15°C to 30°C. The relationships between the development of shoot roots, and tillers and the increase of leaf number on the main stem depended on the air temperature conditions. Plant length was longer at higher air temperatures in the range of 15°C to 30°C. There were fewer leaves on the main stem, and fewer shoot roots and tillers emerged when the young plants were grown at 15°C compared to 20°C to 30°C. No distinct differences in the number of leaves, shoot roots and tillers which emerged during the 40 day period after planting were observed in the temperature range of 20°C to 30°C. Therefore, it was considered that vigorous young plants with a higher growth activity and larger number of tillers could be obtained by using the setts from the middle or higher nodes and by maintaining the air temperature at 20°C or higher in sugar cane. Furthermore, the effect of the air temperature on the photosynthetic rate per leaf area was studied at the active-tillering stage and the late growth stage in sugar cane plants treated with different quantities of water. Optimum air temperature required for the increase of the photosynthetic rate per leaf area decreased from the active-tillering stage to the late growth stage along with the seasonal changes in air temperature in sugar cane plants growing in the temperate zone of Japan. Moreover, water requirement to maintain a higher photosynthetic rate per leaf area decreased with the progression of the growth stages as well as with the seasonal changes in air temperature during the growth of sugar cane in that zone.

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Tropical regions are characterized by hot/humide climates and/or alternate dry and rainy seasons, resulting in somewhat different ecological situations from those in temperate areas, including more frequent and incessant emergence of pests, e. g. ca.25 life-cycles/year of diamond backmoth in Thailand as compared with 10 to 12/year in middle-Japan. Also socio-technological status, e. g. irrigation and mechanization, in agriculture is variable among tropical countries. All these circumstances will significantly influence use of pesticides.
Generally the climatic conditions there affect behavior of pesticides to different degrees : Evaporation, photolysis, hydrolysis, and microbial metabolism will change, to accelerate degradation : Adsorption to soil organic matter tends to decrease slightly at higher temperature.
Although temperature dependence of toxicity in aquatic organisms varies with pesticides, their toxicity in tropical organisms may be assessed based on the data onto similar or adjacent species and varieties living in temperate areas.
Taking into account hot and humide climate, as well as a relatively higher number of untrained workers handling pesticides in tropical and developing countries, safety precautionary steps have to be followed as much as possible during fotmulation, storage, transportation and application. Thus, people concerned should be well trained. Ideally, significantly hazardous pesticides (e. g. Ia and Ib of WHO classification) should be avoided, by which simpler personal protective cloths are generally enough, which is more practical there.
Code of Conduct on distribution and use of pesticides stipulated by FAO (1985) and ensuing PIC procedures (1989) are most appropriate to be pursued to achieve safe and effective use of pesticides.
Developed countries should assist developing countries to the maximum possible extent in establishing necessary legislative mechanisms in transferring all available technologies and know-bows including education and training of staffs and general public.

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The brown planthopper (BPH), Nilaparvata lugens has long been an outbreak-prone insect pest of rice since the introduction of paddy farming into Japan. BPH is also known as a monsoonic migrants originated in tropical Asia. The BPH was a rice-monophagous minor herbivore in the tropical paddy ecosystems of subsistent phase. However, it raised suddenly as a key-pest of high-yielding rice varieties (HYV) spread into tropical Asia during the “Green Revolution” in 1970 s. The BPH outbreaks happened under the pest management with pesticides at International Rice Research Institute (IRRI) is an epitome of the BPH menace which is even now prevailing in tropical Asia. Pesticide use at IRRI farms started with γ-BHC against the rice stem borers in 1962. Since its first occurrence in 1964, BPH infestations magnified rapidly in spite of intensive control with diazinon and later with carbofuran. Eventually, IRRI farms were suffered by devastating outbreak of BPH in 1971-1976, until declining after sequential releases of BPH-resistant HYVs. Resurgence induced by pesticides, development of pesticide resistance, and biotype shifts in the BPH populations were attributed to the outbreak. Restraint of preventive use of pesticides was most effective to stop the BPH problems at IRRI. At present, the BPH density at IRRI farms is at far below the economic threshold level.
The pesticide input is often mistakenly associated with increased productivity of the tropical rice, which is largely attributed to HYVs, fertilizers, and irrigation. In general, potential yield losses due to the insect pests are estimated about 10-20% by the on-farm assessments. Except for massive infestations, less than 10% can be caused by insect damages in a normal year. However, the on-farm economic assessment revealed unprofitability of pest control with high input of pesticides. Expected returns are generally low on high levels of pesticide use, and no control is often the economically acceptable option, and biological control in association with varietal resistance has consistently proven more profitable than pesticide use in long-term experiments. This is the reason why pesticides that were employed as a modern high-yielding technology needed official subsidy.
In addition, the resurgence of BPH is the most expensive hidden cost of pesticide use. Population ecology of BPH and its natural enemies in the tropical paddy ecosystems demonstrated that pesticides readily led to explosive upsurge of BPH populations by destroying its natural enemy complex. High fecundity, short generation cycle, active dispersal, and tolerance to crowding are the biological properties of the BPH for its easy resurgence under the disruptive impact of pesticides to natural enemies. The BPH was initially uncurbed from natural enemies by pesticides used for controlling the other targeted insect pests such as stem borers. Escalated pesticide use against the upsurge of BPH infestations further promoted its resurgence. Eventually, such vicious cycle give rise to uncontrollable outbreaks of BPH, and disaster the rice production systems.
Indonesia is a prime example of the country where the BPH crisis led to the establishment of ecologically sound pest management program in rice. Pesticides were initially adopted as an essential component of “Green Revolution” package for high-yielding technology, and 85% of their cost was subsidised. As increase of pesticide use, resurgence and outbreaks of the BPH prevailed throughout the rice granaries in the country in 1975-1979. Stagnation of rice production made the country the world-biggest rice importer in this period. Forcible planting of the BPH-resistant variety IR 36 suppressed the BPH outbreak, and led to the rice self-sufficiency in 1985. However, the BPH menace revived when IR 36 was replaced with new varieties having improved eating-qualities and high profitability.

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For over 20 years repeated uses of the same herbicides, Paraquat resistant biotypes of Crassocephalum crepidioides, Solanum nigrum, Conyza sumatrensis and Amaranthus lividus in plantations and 2, 4-D resistant biotypes of Sphenoclea zeylanica and Fimbrystylis miliacea in rice fields are occurred in the South-east Asian Tropical Countries.
In the irrigated rice areas rapid changes from transplanting to direct seeded methods have been motivated by the introduction of effective herbicides and combine harvester, development of short culm and early maturing rice cultivars and high labour cost of transplanting. Changes on the rice planting method has caused a shift of weed population and flora. Tremendous increase in the grassy weeds such as Echinochloa crus-galli complex, Ischaemum rugosum, Leptochloa chinensis and weedy rice has been noticed. Effective weed control through integrated weed management (IWM) involving with ecological and biological control are discussed.

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