|ชื่อเรื่อง||:||การพิสูจน์สาเหตุของโรคหงอย อาการพุ่มแจ้ และอาการตายเฉียบพลันของลำไยและการป้องกันกำจัด|
|อ้างอิง||:||http://elibrary.trf.or.th/project_content.asp?PJID=RDG4220026 , http://research.trf.or.th/node/1050|
1. Plant parasitic nematodes causing the longan decline and possible improving treatment. To study the effect of nematodes, longan seedlings were grown in the soils containing plant parasitic nematodes taken from declined orchards with flooding in the rainy season and the orchard sited in upland area. The seedlings grown from seeds were allowed to grow in the pots for 2, 5 and 12 months. Then the seedlings were removed from the pots to compare the growth rate with the seedlings grown in the autoclaved and methyl bromide fumigated soils. It was pointed out that the seedlings from the pots contained at least 1,000 nematodes per 500 g of soil showed a stunting symptom, small amount of root, reduction in leaf sizes and height as compared with the seedlings grown in the soil without nematodes. The finding indicated that the nematode might play an important role in causing a decline in longan. For the reason, another set of pot experiment was set up in the greenhouse to reconfirm of the previous finding by growing the normal and declined air layering plantlets in the soil containing nematodes. In this experiment the tested pots were kept in the greenhouse for 20 months and the samples of soils were taken in every 5-8 months for nematode counting. Similar results were obtained in the later experiment that the nematode was one of the factors that generate the declined symptoms in longan. The sign of decline was expressed on tested plantlets 5 months after they were left in the pot containing nematodes. In contrast, when normal plantlets were grown in fumigated soil for a period of 13-17 months, the leaf length was longer than initial measurement while no change was recorded on leaf width. Furthermore, when declined plantlets were grown in declined nematode soil, the leaf sizes were reduced in 5-6 months after transplanting. But no changes of leaf sizes were observed when declined plantlets were grown in fumigated nematode soil. A number of R. reniformis nematodes, which were added to all tested pots, were decreased in all treatments in 5 months later. Among the tested treatments, application of 50 g of urea fertilizer in one square meter area was considered to be the best treatment to reduce the nematode numbers. Likewise, adding 500 g of chicken manure and 25 g of urea per one square meter was the best method to improve the declined trees grown in nematode soil. Another experiment was carried out to isolate the fungi borne in chicken, bat and cow manures. The results showed that there were different kinds of fungi associated with these manures especially Paecilomyces sp. The Paecilomyces sp. was reported to be the parasite of some plant parasitic nematodes. In comparison, there were no fungi associated with commercial pellet chicken manure and pellet chicken manure plus fertilizer. Adding none modified animal manures will increase the beneficial microorganisms like Paecilomyces sp., Fusarium sp. and Humicola sp. to the soil. Therefore, it is recommended to use animal manures to help to improve the decline of longan. The microplot experiment was also designed to study on the association of nematodes with longan decline. Investigation was aimed to reduce number of plant parasitic nematodes in the orchard conditions. The results revealed that the initial count of the number of nematodes of 100-500 per 500 g of soil were insufficient to generate the declined symptoms in the orchard conditions. Because there were no trees in the tested microplots apparently expressed the declined symptoms. Correspondingly, the numbers of nematodes were decreased in all applied treatments including control. However, applying chicken manure together with urea was significantly reduced the numbers of nematodes when compared with the numbers observed at the beginning of the study. Trees supplemented with cow and chicken manures, urea fertilizer, ZnSO4, CuSO4, and boric acid twice a year gave a better growth, increased in leaf sizes and total weights of shoot and root when compared with control. The program of soil amendment was set up to get rid of nematodes before replanting by removing of the old trees and root systems. After that the non-hosts of nematodes like peanut, velvet bean and zinnia were grown and amended with chicken manure and urea fertilizer. A drastically decreased in number of nematodes by 80% were noted on the treatment of planting peanut in two consecutive crop seasons. 2. Effect of water management on longan decline symptoms. In orchard situation, some other factors beside nematodes may involve in these unhealthy looking symptoms. Considerable factors involved with water management and occurrence of witches’ broom on the trees. Therefore, water requirement by longan was studied in the pot experiment by giving the 2 months old seedlings with 3 different water levels. The treatments comprised of too much water, sufficient water and insufficient water. After 3 months, the results distinguished that the best growth came from too much water treatment but the seedlings were died 20% due to root rotting. In insufficient water, stunting growth was observed and the seedlings were died 15%. However, in contrary, sufficient water gave a better growth, good branching and no seedling death. Conclusively, the stresses like lacking of water and too much water may create stunting growth and root rotting causing some death to longan plants. Giving longan with sufficient water should bring into practice in order to obtain a better growth and healthy trees. 3. Witches, broom combined with plant parasitic nematodes as contributed agents to longan decline. Air layering longan plantlets of Daw cultivar were grown in the pots containing the nematode soil from declined orchard. The young shoots of tested plantlets were then infested with longan mite. In control treatment, the plantlets were grown in autoclaved soil without mite infestation. Thirteen months later, 20-50% leaf curl developed on plantlets infested with longan mite. When leaf sizes among the treatments were compared. The plantlets treated with both nematodes and longan mite visually showed the clear symptoms of decline. The nematodes combined with longan mite produced smaller leaves as compared with the leaves obtained from plantlets grown in fumigated soil and in nematode soil alone. It may be ascribed that trees having mite infestation for a long period of time and also grown in the soil containing high level of nematodes, these two factors may have caused decline of longan trees. 4. Relationship of mite's toxin and witches' broom symptoms. The crude extracts from curled and normal shoots were trial on the thin layer chromatography (TLC). It was found out that crude extract from curly shoots was some how different from the one obtained from normal shoots. Anyway, we were not able to point out whether the different had come from longan mite or not. When macerated mite was compared with crude extract of curly shoots, there were similar spots appeared on the TLC. It was presumed that only trace amount of toxic substance presented in the crude extract. Attempt to purify the substance was too difficult due to its complexity nature. Up to this point, the certain nature of the substance was not able to clarify yet. Furthermore, in the future study, detection of tentative toxin should be thoroughly ascertained with Gas Chromatography (GC) or High Performance Liquid Chromatography (HPLC). The trials of several treatments with crude extract from curly shoot were performed with the seedlings. Seedlings of all inoculation methods failed to develop the symptoms of witches’ broom as occurred in the orchard. Meanwhile, 20-75% of the seedlings developed the witches’ broom symptoms when infested with living mite. Therefore, only living longan mite had a mechanism to cause the witches’ broom in longan. 5. Experiments on a quick decline syndrome and tree death. As following of the case, trees grown in association with mushrooms for 2-3 consecutive years had shown the symptoms of decline for at least 45% and died for 6%. The evidence of finding presumed that the ground mealybugs (Paraputo sp.) that fed on roots and mushrooms were the causal agents of the death of longan. The protruded mushrooms were classified into 2 species. One was Phlebopus portentosus and the second one was longan mushroom, Boletus dimocarpicola. Both of them are edible and quite preferable for a local consumption as their delicacy taste. More extensive study was put on declined tree with mushrooms by digging up the soil and inspected at the trunk base and root system. Both trunk base and root system were covered with fungal rhizomorphs or thecae. Inside the theca tunnels, there were a number of ground mealybugs feeding on the trunk base and root. The tree died in this case may be because the direct effect of ground mealybugs feeding on longan root. To determine the actual cause of the incidence, 5-10 young stage of ground mealybugs were released on roots of 3 months old longan seedlings. After 2 weeks, the tested seedlings showed the wilting symptom and then drying by 67%. The experiment was terminated at one month. Similar trial was done by releasing 40 young and mature stages of mealybugs on roots of 6 months old longan seedlings. The seedlings were turned wilt at 7-10 days and died 2 weeks later. The two seedling experiments provided supportive evidence that ground mealybug was the real agent that caused the death of longan. Later, the study of the association between the mushrooms and longan was carried out. It was determined that both organisms had related with each other in the form of mycorrhizal relationship. The ground mealybug of longan, Paraputo sp. is a sucking type insect. It belongs to Family Pseudococcidae, Order Homoptera. It took 29-55 days to complete a life cycle. The young and adult mealybugs fed on root under the encasement of fungal rhizomorph. Attempt to count revealed that there were 2-260 mealybugs fed on root sample surface of one inch long. Ants in the soil were occasionally seen to carry a young ground mealybug to disperse to the new root for new source of nutrient. In return, ants obtained honeydew secreted by the mealybugs. In order to get honeydew as a food, ants were observed to make a hive in the ground beside the trunk base of all ground mealybug infested trees. In the process of digging up of the soil for root inspection, ground mealybugs were disturbed. They were then dispersed on the ground surface. In this situation, the ants were tried to responsible by rushing to carry the mealybugs away from troublesome. About 9 species of ants were found in this complex relationship. The Pseudolasius sp. was the most common species, which observed in all inspected trees. Control of mushrooms and ground mealybugs in longan and mango by using chemicals together with different kinds of absorbent materials were trial in the orchard conditions. The result indicated that chlorpyrifos 90 ml and quintozene 60 ml mixed in 20 liters of water applied together with ground coconut exocarp absorbent at the trunk base was given a moderately controlled of ground mealybugs and mushroom mycelium. Although the two mentioned chemicals were able to stop the mealybugs and mushrooms in certain level but in severely attacked case; the tree will be no longer recovered. The biological control using Trichoderma sp. and Steinernema carpocapsae, nematode was also examined in the orchard conditions. The two organisms did not produce any effects on both ground mealybugs and mushrooms at all. 6. Diseases and insect pests of off-season longan. A current use of potassium chlorate (KClO3) to produce off-season longan caused some prevalence of certain disease and insect pests. Off-season crops might have served them the places to be harbored and furnished them some good sources of nutrients all year round. The major disease that ever observed at Phrao and Mae Tang, Chiang Mai was phytophthora blight and fruit drop caused by Phytophthora palmivora. The disease reduced the harvest by 40% in the heavily infected orchards. Contaminated soil samples collected from infected orchard were brought back to the laboratory for Phytophthora palmivora isolation. We were not able to isolate it from the samples probably due to the inappropriate medium used. Regarding to insect pests, three types of sucking insects, Ceroplastes pseudoceriferus, Depanococcus chiton and Colobesthes sp. were observed in the potassium chlorate using orchards. The two particular insects were also spread to the neighbor of none using orchards too. C. pseudoceriferus is belonged to the order Homoptera and family Coccidae. It was first noticed in the middle of 1999. Within a year, it had 2 cycles or generations. About three natural parasites were recognized to parasitize on them. The Anicetus nov. sp. near stylatus was considered as the most relevant species. The population of this natural enemy was prevailed in May and September. During these months it was able to parasitize on C. pseudoceriferus as high as 53-58%. The most appropriate time to control C. pseudoceriferus was suggested to do in June because it was in growth stage 1 or younger stage of star shaped which was quite susceptible to insecticide. In June, scarce amount of natural enemies of C. pseudoceriferus was observed. It was also easy to recognize C. pseudoceriferus at growth stage 1 than at crawler stage. At this stage, it had begun to stick on the host with no movement any more. At growth stage 2 in late October was another appropriate time to spray on this insect. Another significant insect found to confine on off-season longan in areas of Chiang Mai and Lamphun was wax scale insect (Drepanococcus chiton). It belongs to order Homoptera and family Coccidae. This wax scale attacked on young shoot, flower panicle and young fruit panicle up to mature stage. It caused the dryness or blight of these parts and mature fruit became dirty. Finally, the dirty mature fruit became unmarketable. The biology of D. chiton was studied in the laboratory. It took 54 + 5.10 days for female to complete one life cycle. Eight generations was observed in one year. Cephaleta bruriniventris was detected to be the natural enemy of D. chiton. A trial in laboratory to select for the most effective chemical for controlling of D. chiton was carried out with stage 1 (crawler) insects. DC tron plus was the most effective chemical control result. In orchard conditions, carbaryl solution at the rate of 50 ml per 20 liters of water gave a good result to control of D. chiton at crawler stage. The carbaryl was able to kill 89%. In comparison, white oil and petroleum oil were controlled 79% of the insect. In the older stages 2 and 3, carbaryl was the most effective one followed by white oil and petroleum oil. The extract from neem was ineffective to use with wax scale. Good result was come from carbosulfan at the rate of 30 ml per 20 liters of water when used with the adult stage. This chemical effectively killed 67 and 86% within 3 and 5 days respectively. Petroleum oil did not work at all when used with the adult stage of wax scale. Thrips were considered to be the important insect pests of longan. They were condensed to harbor on the flower panicles causing dryness and premature dropping of the flowers. The survey to inspect the young shoots and flower panicles of longan in the orchards revealed that there were at least 5 species of thrips attacked longan. The species comprised of Scirtothrips dorsalis Hood, Thrips hawaiiensis Morgan, Haplothrips sp., Thrips coloratus Schmutz and Megalurothrips sp. At full bloom stage, the maximum of 234 thrips per panicle was noted. When fruit size was about 3-5 mm in diameter, the number of thrips was reduced to 8 per panicle. The thrips were begun to attack the longan flower at button stage. Therefore, it would be advised to spray at button stage with dimethoate 40% EC, 20 ml per 20 liters of water. This chemical was proved to be the most effective one. The new record of infestation of flatids (Colobesthes sp.) was observed in the orchard at Mae Our, Pasang district, Lamphun. It did feed on shoot, young shoot and fruit of longan. As they fed on tree parts, they excreted the honeydew. The honeydew had dispersed to any parts of longan including fruit panicle. The sooty mold was then come to cover up the fruit causing the loss of fruit quality. White oil mixed with carbaryl was recommended as the use to control flatids. Another new record was the Asian ambrosia insect, Xylosandrus sp. It belongs to order Scolytidae. It was confined in the longan orchards at Fang district, Chiang Mai. Considerable losses were observed due to the break up of immature fruit panicles. Because of no information available at the moment, our research team is now emphasizing on collecting the data of infestation and its characteristics of damage to be related to the control measure to be set up in the future. The damages due to ambrosia insect were categorized into the broken of the branches and the mycelium clogged up of vascular bundle causing wilting of branches. Heavy infestation also caused either the declining or death of tree. Intensive applications of potassium chlorate (KClO3) together with various formulas of fertilizers were practiced by a number of orchards at a moment. Regarding to this situation, the problems were existed when the growers gave too much water to each tree by making the ridges around the tree canopy to collect the water. It was noticed that the subsoil layers of most of longan orchards were composed of hardpans that caused the poor drainage of extra water. They may actually become predisposible for a rotting problem. In different locations, we have found the foliage of some trees quickly turned yellow and the trees soon died with dried leaves remained attach on the tree. In this case, the laboratory experiment had answered that because of too much of water and no any other causal agents that caused the death of trees.
จริยา วิสิทธิ์พานิช . (2546). การพิสูจน์สาเหตุของโรคหงอย อาการพุ่มแจ้ และอาการตายเฉียบพลันของลำไยและการป้องกันกำจัด.
กรุงเทพมหานคร : สำนักงานกองทุนสนับสนุนการวิจัย.
จริยา วิสิทธิ์พานิช . 2546. "การพิสูจน์สาเหตุของโรคหงอย อาการพุ่มแจ้ และอาการตายเฉียบพลันของลำไยและการป้องกันกำจัด".
กรุงเทพมหานคร : สำนักงานกองทุนสนับสนุนการวิจัย.
จริยา วิสิทธิ์พานิช . "การพิสูจน์สาเหตุของโรคหงอย อาการพุ่มแจ้ และอาการตายเฉียบพลันของลำไยและการป้องกันกำจัด."
กรุงเทพมหานคร : สำนักงานกองทุนสนับสนุนการวิจัย, 2546. Print.
จริยา วิสิทธิ์พานิช . การพิสูจน์สาเหตุของโรคหงอย อาการพุ่มแจ้ และอาการตายเฉียบพลันของลำไยและการป้องกันกำจัด. กรุงเทพมหานคร : สำนักงานกองทุนสนับสนุนการวิจัย; 2546.