Tea Fields Research Articles

Relationship between the occurrence of the predacious coccinellid Pseudoscymnus hareja and the mulberry scale Pseudaulacaspis pentagona across tea fields in Shizuoka Prefecture

Relationship between the occurrence of the predacious coccinellid Pseudoscymnus hareja and the mulberry scale Pseudaulacaspis pentagona across tea fields in Shizuoka Prefecture

Evaluation of Spray Drift from Tea Field during Pesticides Application

感水紙を用いて茶園における農薬散布時のドリフトを調査し，以下の知見を得た。1)オープンソースの画像処理プログラムImageJを用いて感水紙の液斑を自動抽出することが可能であった。また，ImageJのAnalyze Particlesコマンドを用いて，個々の液斑の面積や液斑の被覆面積率を容易に求めることができた。ただし，自動2値化で得られた液斑面積は視覚判断による液斑よりも大きめに抽出されるので，補正係数0.7411を用いて補正する。2)散布方法やノズルの違いにかかわらず，ドリフトした液滴の99％が直径200μm未満， 80％が直径125μm未満であった。3)ノズルの違いに関しては，手散布および乗用型防除機ともに，散布粒子の大きいノズルのほうがドリフトは少なかった。しかし，葉面付着程度には差は見られなかった。4)手散布と乗用型防除機の比較では，乗用型防除機のほうがブームノズルと樹冠面との距離を近く保てるため，ドリフトが少なかった。5)乗用型防除機の飛散防止カバーは粒子径が小さいノズルでは効果が見られたが，ドリフト・リスクを小さくするためには，粒子径の大きなノズルを使用することが望ましい。6)ドリフト率の値を用いて，他のドリフト試験の結果と比較したところ，茶園においては散布ノズルと樹冠面との距離を近くすることが可能なので，ドリフト率が約1/10と非常に小かった。

Distribution of the coccinellid Pseudoscymnus hareja as a predator of the mulberry scale Pseudaulacaspis pentagona in tea fields in Shizuoka Prefecture

Distribution of the coccinellid Pseudoscymnus hareja as a predator of the mulberry scale Pseudaulacaspis pentagona in tea fields in Shizuoka Prefecture

Research on the Natural Enemies of the Mulberry Scale, Pseudaulacaspis pentagona (Targioni), in Tea Fields in Shizuoka Prefecture, Japan

静岡県の茶園に生息するクワシロカイガラムシの土着天敵類の発生実態を明らかにするため，2002年と2003年に数カ所の茶園において，葉層下に設置した黄色粘着トラップに捕獲された天敵類の種類とその数を調べた。その結果，チビトビコバチ，サルメンツヤコバチ，ナナセツトビコバチ，クワシロミドリトビコバチ(仮称)，および二次寄生蜂のマダラツヤコバチの５種の寄生蜂と捕食性タマバエDentifibula sp.，ハレヤヒメテントウ，キムネタマキスイ，およびヒメアカホシテントウの３種の捕食性コウチュウ類がトラップに捕獲された。寄生性天敵では，チビトビコバチの捕獲数が最大で，次いでサルメンツヤコバチや捕食性タマバエの捕獲数が多く，羽化調査の結果と同様にチビトビコバチが第1優占種であった。捕食性コウチュウ類では，ハレヤヒメテントウの捕獲数が他種より圧倒的に多く，本種がコウチュウ類の優占種であった。チビトビコバチは年間5～6回の明瞭な捕獲ピークが，サルメンツヤコバチとナナセツトビコバチでは年間３回の捕獲ピークが，捕食性タマバエとハレヤヒメテントウでは，やや不明瞭であるものの年間３回程度の捕獲ピークが認められた。さらに，チビトビコバチ，サルメンツヤコバチ，ナナセツトビコバチ，および捕食性タマバエでは，寄主のクワシロカイガラムシの幼虫ふ化ピーク日または雄成虫のピーク日と各天敵のピーク日との関係をまとめた。クワシロカイガラムシ幼虫または雄成虫の捕獲数とチビトビコバチの成虫捕獲数との関係を各世代毎にプロットしたところ，寄主－捕食寄生者間のモデルに示されたような震幅を拡大しながらの左回りの挙動を示した。このことから，チビトビコバチが，天敵として寄主の密度抑制に深く関与していることが示唆された。

Damage to the first tea shoots by leaf beetle, Demotina fasciculate Baly (Coleoptera: Chrysomelidae) in tea fields in Shizuoka Prefecture, Japan

Damage to the first tea shoots by leaf beetle, Demotina fasciculate Baly (Coleoptera: Chrysomelidae) in tea fields in Shizuoka Prefecture, Japan

Development and Characteristics of the Walking-type Fertilizer Applicator with Boom Type Blow Heads for Tea Field

歩行作業による茶園施肥作業の軽作業化および高能率化を目的として，パイプ噴頭を備える台車式の歩行型施肥機を試作した。また有効作業量や，心拍数増加率等の作業特性について手押し式および動力付施肥機と比較検討したところ，以下の結果を得た。(1) 台車式施肥機は，左右に旋回する2本のパイプ噴頭により，２うね同時施肥と，一方のうね端で旋回動作を要しない作業法を実現することができる。(2) 台車式施肥機は，従来の歩行型施肥機より作業速度がやや遅いものの，作業幅の拡大により，有効作業量は0.89ha/hとなった。手押し式施肥機は0.71ha/h，動力付施肥機は0.58ha/hであり，台車式施肥機の作業能率の高さが示された。(3) 台車式施肥機の通常作業時の心拍数増加率は20％～52％となり，手押し式施肥機の43％～93％や動力付施肥機の45％～69％より低く，作業負担は小さかった。(4) 作業速度が同一であれば，台車式施肥機の心拍数増加率は手押し施肥機や歩行動作と同等であり，動力付施肥機より低かった。一方，有効作業量を同一にして心拍数増加率を比較すると，台車式施肥機の心拍数増加率が有意に低くなった。(5) 以上より，パイプ噴頭を有する歩行型台車式施肥機は，作業幅拡大により有効作業量が大きく，また作業速度がやや遅いことにより結果として作業者への作業負担が軽減できることが明らかとなった。

A Supplement to the Insect Fauna of Tea Fields in Japan with Some Newly Described Species.

A Supplement to the Insect Fauna of Tea Fields in Japan with Some Newly Described Species.

Occurrence of Green Flatid Planthopper, Geisha distinctissima (Walker) in Tea Fields in Shizuoka Prefecture and Efficacy of Pesticides against Green Flatid Planthopper

We conducted a questionnaire survey with the technical adviser of the farm co-operative and farmers for assessing the occurrence of Green Flatid planthopper Geisha distinctissima (Walker) in tea fields. The survey distinctly revealed that the planthopper was present throughout the Shizuoka prefecture. It is believed that the population of G. distinctissima has increased during these past several years.Among the 7 insecticides investigated, DMTP was the most effective pesticide against the nymphs and adults of this planthopper, irrespective of the disposal method.

The Salty and Strong Wind Damage in The tea Fields at Kagoshima and Okinawa Prefectures due to Typhoons in 2004

The Salty and Strong Wind Damage in The tea Fields at Kagoshima and Okinawa Prefectures due to Typhoons in 2004

Probing behavior of the tea green leafhopper on different tea plant cultivars

The probing behaviors of the tea green leafhopper, Empoasca vitis (Gothe), on 9 tea cultivars were studied using video-text Direct Current-Electrical Penetration Graph, i.e., DC-EPG. The following 7 types of waveforms produced by the leafhopper stylet probing were determined: A, stylet pathway formation; S, salivation when stylets pierce into and stay in phloems; C, active ingestion before stylets reach phloems; E and F, passive ingestion in phloems; R, the insect resting with its stylet inserted into the leaf tissue and NP without probing. The 9 tested tea cultivars were categorized into 3 groups by the cluster analysis according to the number of probes per insect, waveform durations, or duration per probe of various waveforms on different tea cultivars. Waveforms S, E and F correlated to the main feeding activity of the leafhopper and may provide valuable information on predicting the resis-tance level of the tea plants to the leafhopper. The resistance level of the 9 tea cultivars to the leafhopper was ranked based on the durations of waveforms S, E and F, as well as the duration per probe including various waveforms. The ranking order of the resis-tance was: Longjingchangye > Hangdan > Zhenghedabaicha > Qianmei 601 > Hongyafoshuo > Zhongcha 102 > Zhongcha 302 > Longjing 43 > Anjibaicha, which corresponded to the resistance level determined by the population density (infestation) of the leaf-hopper on the 9 tea cultivars in the tea fields. Our study suggests that this simple and convenient DC-EPG technique might have great potential as a reliable tool to predict the resistance of tea cultivars to the tea leafhopper.

Dissipation of carbofuran and carbaryl on Oolong tea during tea bushes, manufacturing and roasting processes

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranol-N-methylcarbamate) and carbaryl (1-naphthyl-N-methylcarbamate) are insecticides widely used in tea plantations. The objective of the present study was to evaluate the dissipation of carbofuran and carbaryl during the growth periods of Oolong tea, processing and roasting. Analysis of the residual insecticides was carried out using high-pressure liquid chromatography with a post-column fluorescence detector. Results showed that in the tea field carbofuran dissipated faster then carbaryl. Manufacturing processes of Oolong tea further reduced the carbofuran and carbaryl contents. The persistence of carbofuran and carbaryl was decreased with increasing roasting temperature. From the results, we conclude that the presence of carbofuran and carbaryl in tea can be reduced by proper field management, manufacturing and roasting processes.

Insecticide susceptibility of Demotina fasciculate Baly collected in tea fields

Insecticide susceptibility of Demotina fasciculate Baly collected in tea fields

Characteristics of Non-allophanic Andosols and Yellow Soils of the Tea Fields in Mie Prefecture

Characteristics of Non-allophanic Andosols and Yellow Soils of the Tea Fields in Mie Prefecture

Effects of tillage in hillside tea field on the soil and root system

Effects of tillage in hillside tea field on the soil and root system

Long-Term Fluctuation of Populations of Kanzawa Spider Mite, Tetranychus kanzawai Kishida, in Commercial Tea Fields for Last Thirty Years in Shizuoka Prefecture, Japan

Long-Term Fluctuation of Populations of Kanzawa Spider Mite, Tetranychus kanzawai Kishida, in Commercial Tea Fields for Last Thirty Years in Shizuoka Prefecture, Japan

Assessment of replacement cost of soil erosion in Uva high lands tea plantations of Sri Lanka

The Uva High lands tea plantations in Sri Lanka represent intermediate zone on agroclimetic classification. This study was conducted to assess the runoff, soil loss and subsequent nutrient losses from Vegetative Propagation (VP) and Old Seedling Tea (OST) plantations of Passara region of Uva high lands in Sri Lanka. Four experimental soil erosion measurement units were installed 2 each for both land categories of 25 m length and 4 m width during 2010-2011 for one successive year, from these land uses were quantified the following standard methodologies. The annual runoff soil loss of old seedling tea fields were recorded as 25.52 tons/ha/yr and VP fields were calculated as 3.41 tons/ha/yr respectively of Uva regions in Sri Lanka. Loss of N was recorded as 29.34 and 4.80 kg/ha/yr from seedling and VP tea fields respectively. Loss of P of seedling tea field was observed as 2.10 and P from VP field was 0.92 kg/ha/yr. Loss of K was calculated as 182.4 kg/ha/yr of seedling field and K was assessed in VP as 13.6 kg/ha/yr. Total loss of organic matter was evaluated as 319.01 and 60.03 kg/ha/yr seedling and VP tea fields respectively. Subsequently, Total replacement (onsite) cost of one hectare seedling tea fields was recorded as Rs. 18011.45 and the replacement cost of VP field was Rs.8270.89 with the labor charges for spreading fertilizers and repairing and maintaining costs.

Environmental Problems From Tea Cultivation in Japan and a Control Measure Using Calcium Cyanamide

ABSTRACT A field experiment, involving lime N (calcium cyanamide, CaCN2) fertilization as a control measure, was conducted to study environmental problems induced by long-term heavy N application in Japanese tea fields. Long-term tea cultivation caused serious soil acidification. Seventy-seven percent of the 70 tea fields investigated had soil pH values below 4.0, and 9% below 3.0, with the lowest value of 2.7. Moreover, excess N application in tea fields put a threat to plant growth, induced serious nitrate contamination to local water, and caused high nitrous oxide loss. Compared with the conventional high N application treatment (1100 kg N ha−1) without lime N, the low N application (400 kg N ha−1) with calcium cyanamide effectively stopped soil acidification as well as achieved the same or slightly higher levels in tea yield and in total N and amino acid contents of tea shoots. The application of calcium cyanamide could be a suitable fertilization for the prevention of environmental problems in tea cultivation.

Aluminium in tea plantations: mobility in soils and plants, and the influence of nitrogen fertilization

The levels of extractable aluminum (Al) in soils of tea plantations, Al concentrations in tea leaves and the impact of nitrogen fertilization on these two parameters were investigated. In addition, the properties of soils from tea plantations were compared to those from soils of adjacent non-tea fields to evaluate the effect of land use conversion (from non-tea soils to tea soils). Exchangeable Al (extracted in 1 mol l(-1) KCl) ranged from 0.03 to 7.32 cmol(c) kg(-1) in 94 tea fields and decreased rapidly with increasing soil pH. In comparison with non-tea soils, tea soils had a significantly lower pH and exchangeable Mg(2+) concentration but higher organic matter contents and exchangeable K(+) concentration. Contents of extractable Al were not different (P > 0.05) between these two soils. The concentrations of Al in mature tea leaves correlated significantly with exchangeable Al in soil samples taken at a depth of 20-40 cm and with exchangeable Al saturations in soil sampled at depths of 0-20 and 20-40 cm. In the pot experiment, nitrogen fertilization significantly increased extractable Al levels but decreased soil pH and the levels of exchangeable base cations. Nevertheless, the levels of Al in mature leaves and young shoots were significantly reduced by the application of large amounts of N fertilizer.

Relationship between the seasonal prevalence of the predacious coccinellid Pseudoscymnus hareja (Coleoptera: Coccinellidae) and the mulberry scale Pseudaulacaspis pentagona (Hemiptera: Diaspididae) in tea fields: Monitoring using sticky traps

The relationship between the seasonal prevalence of the predacious coccinellid Pseudoscymnus hareja and the mulberry scale Pseudaulacaspis pentagona in tea fields was investigated using sticky traps set inside tea bushes. Crawlers (newly-hatched larvae) and winged adult males of P. pentagona and adults of P. hareja were captured in large numbers. The number of trapped P. hareja adults reached a peak 0 to 15 days (average: 6.9 days) after the peak in the number of P. pentagona crawlers in each tea field. P. hareja adults captured in this period are considered to have visited tea fields to prey on P. pentagona larvae and to deposit their offspring (larvae), which primarily consume P. pentagona larvae. Another relatively lower peak in P. hareja adults was found 0 to 14 days (average: 6.6 days) after the peak in the number of P. pentagona adult males. P. hareja adults trapped in this period are suggested to be those that had spent their larval period feeding on P. pentagona larvae and male pupae in tea fields. Thus, the seasonal occurrence of P. hareja adults in tea fields is associated with that of P. pentagona larvae as the main prey of P. hareja larvae.

集団茶園系のノンポイントソースによる硝酸負荷の実態―静岡県牧之原台地における事例―

The authors measured the nitrate concentration of river water from a catchment basin of the collective tea fields in the Makinohara plateau in Shizuoka prefecture, from June 2002 to May 2003. About 1,000 kg · ha-1 · y-1 of nitrogen fertilizer has been used in the tea fields for about 30 years. The annual average NO3-N concentration and pH were 24.4 mg · l-1 and 4.9, respectively. NO3-N concentration decreased as a result of a comparatively small amount of precipitation, and repeated. The total annual nitrogen outtlow from the tea fields was 428 kg · ha-1 · y-1. The ratio of nitrogen load to the amount of applied nitrogen fertilizer was 79.2 %. NO3-N load was affected by discharge from the tea fields.