Nuclear Sdence and TechiMlogy, Vol.6, No. 2 (2016). pp. 47-51
Electron-beam irradiation as a quarantine treatment against red mite on exported cut flower of Chrysanthemum
Doan Tlii The, Ngnyen Thi Ly«, Vo Thi Kim Lang, Cao Van Chung Research and Deireiapmen, Centirr for Radiation Technology, 202A Sti-ee, 11, Linh Xuan W ,
Thu Due DistiicI, HCM. City 'Email: nguyenly2408l^gmail.com (Received 04 September 2015, accepted 20 June 2016)
dose incieased. The hatchmg rate of eggs al 300 Gy was 4.25% and no laivae F, survived during
Keyword,: C A , y . « t e ™ „ , £ t e » . o „ S c ™ , Irradiation, Quarantine tieameni Redmlte vety limited in the volume compared with Japan's Chrysanthemum flower imports. To improve the value export, we need not only new types of flowers and application of advanced cultivation techniques but also quarantine treatments [I].
I. INTRODUCTION Viemam has a tropical monsoon climate.
This condition is suitable for many kinds of flowers. The area of cut flower production in Vietnam inceased 2.3 times, the output value gisw 7.2 times fi-om 2005 to 2015, reached 6,500 billion VND. However, the flower export value is only $ 60 million out of more than $ 30 biUion for the export of argricultuial products, forestiy and fisheries. This figure is insignificant compared to the total trade of 130 billion USD of the flower in the world. There are countless varieties of Chrysanthemums.
Beside traditional yellow, other colours such as white, purple, and red are available. In Vietnam, the planting area of Chrysanthemum has increased year by year and now estimated occupadng about 30% of the total cut flower area in Vietnam. Export value of Chrysanthemum to Japan is approxunately 194 thousands USD per year. However the figure is
Cut Chrysanthemums axe subjected to restrict for plant pest quarantine especially red mites. Therefore, they are treated by using tradition chemical such as methyl bromide or insecticide solution before shipment to intemational markets. However, methyl bromide will be phased out because it is ozone depleting substance [2] and unsafe for workers and the environment to addition, the ftanigation can not treat a large quantity of flowers simultaneously and takes several hours to complete the tteatment. Therefore, alternative methods to replace methyl bromide fumigation arc required. The method that can treat a large number of flowers is irradiation treatment [3]. There are three pnmary types of 02016 Viemam Atomic Energy S«,ie,y and V.emam A , „ » c Energy Ins.im.e
ELECraON-BEAMIWtADIATIONASAQIJARAOTINETRSftSMEjn-AGAINST RED MITE irradiation c^iahle of phytosanitaiy treatment
such as gamma, electron beam and X-ray. In this study, eletron beam were used to irradiate insect pests infesting cut flowers. Deg)ite reduced penetration, eletion beam processing allows for much faster and more precise processing than other treatment options [4].
Additionally, the efBciency of electron beam processing often means that no warehousing of product is necessary before treatment significant advantage for cut flowers.
Moreover, the most significant advantages of eletron beam processing are that the technology does not require the use of radioactive isotopes.
This significantiy reduces a nmnber of security concerns, simphfies pennitting and regulatory requirements, and eUminates the costly and complicated processes of acquiring, transporting, instalUng, and eventually replacing radioactive sources [5]. At the doses required for phytosanitary tireatments, electricity based process^ such as electron beam are also more cost-effective than cobalt- 60 [6].
n . EXPERIMENTAL Materials
Red mites, thiips and leafininers were investigated on Chrysanthemums in ward 8, Da Lat city. Lam Dong provmce to asses the level of theu damage. Red mites the most infected pests were collected, transferred to die biology laboratory of Research and Development Center for Radiation Technology and reared on leaves of Chrysanthemums (28 ± 2"C temperature, relative humidity of 80 ± 5%).
Direct investigaHon of the main harmful insects on cut flowers
Chrysanthemums which were blooming on one farm at 5 points diagonaUy were collected and observed by stereoraicroscope.
Ten consecutive plants at tiie point and two
leavM fer s j ^ ^ 1 ^ nyere jnvestigaied tiw UKects such as r e d n o ^ tiirips and leafininers..
After that, tl» ^lab^ were put in separate plastic b a ^ aad tia^ifered to tbe laboratoiy. | Time for iiive^l^tiofii was during JanuaryJ Calculating tS^ ptqm^cm density of insect b / ; the formula:
Density (msect/leaf) = total investii insect/total investigated leaf.
Assessing insects infestmg in flowers was expressed by symbols as fiillowing: ^ - No appearance
+ There is damage but no significant damage (<
1 msecl/Ieaf or 1 insect/long stem (5 -7 cm) ++ There is average appearance and average damage (1-4 insects/leaf) or long stem (5-7 cm) +++ There is common appearance, sigoificant and heavy damage (over 4 head/ leaf) or long stem (5-7 cm).
Irradiation treatment
The red mites were isolated fiom most ' infected leaves, reared on the same object and tiieir developmental stages were observed U "'•
laboratoiy conditions. Different development^ j stages of red mite (eggs, l"" mstars, 2°" instais, 1 3"" instars, and adult) on detached leaf were ) irradiated witii doses ranging from 0-400 Gy by i electi-on beam accelerator UERL-10-15S2, ip MeV at Research and Development Centw for Radiation Technology wifli parameter Fsyn '=
70 Hz, V = 4.2 m/mm. Fricke dosimeter were used to measure absorbed dose. Aft«
irradiation, flie samples were held at standa^
rearing condition (28-3rC, 80-85% RH) tb observe mortality rate, survival rate of nynqil^
and female adult reproduction.
Data analysis
Experimental data were analyzed of variance (ANOVA) using Sta^raphics 15.0 widl flie reUability P = 0.05.
DOAN THI THE, NGUYEN THI LY, VO THI KM LANO, CAO VAN CHUNG m . RESULTS AND DlSCUSSIOiV
Direct investigalioii of the main luniifid insects on cat flowers
The result showed that red mites were common, causing signiflcanl damage on Chrysamhemum (Table I). This kmd of pest focused on midribs and suck tissues of leaves
and flowers. If the leaves and flowers infested red mites seriously, they would have brown color and faU down. Under flie above rearing conditionii, the total life cycle of red mite wasl5 days. The common appearance stages on cut Chrysamhemum were eggs, 2"' instars and adults. In this study, red mites were chosen to be controlled by irradiation.
Table L Tie pcsls infesting on Chn'Santhemum cultivated in ward 8, Da Lat cily. Um Dong province
Effect of irradiaflon on development of eggs to adnlts
The data mdicated a posifive relationsMp between radiation dose and egg mortality.
Hatchmg rate of eggs decreased with the increasing absorbed dose (Table II). Mortality of 1-2-day-old eggs of the red mite were 10.56- 94.59; 97.14; IOO and 100% after treatment with doses of 0; IOO; 200; 300, and 400 Gy, respectively. At low doses less than 300 Gy, the number of eggs stiU hatched, but effects of
iiradiation were reflected by mortaUty in subsequent stages. No adults of the red mite developed from 1-2-day-old eggs exposed to doses more than 100 Gy. The increase m mortality of immature stages developing from irradiated eggs was usually observed in red mites. Similar results were also reported by Hu et al, 2004 [7]; Ignatowicz and Banasik- Solgala, 1999 [8].
Table n. The development of iiradiatcd eggs of red mites
Mean values withm the
Effect of irradiation on development of 2"' instars to adults
The obtained results in Table ID indicated the effects of irradiation on survival of 2"^
instars at subsequent developmental stages.
Mortahty of red mites that developed from
•• Slagefollosved by Ihe same letter are nol stgniflcan, different at P^.OS.
irradiated 2"' instars increased with the increase of radiation dose. The percentage of adults that developed from non-nradiated 2"' instars was 94.34%. Meanwhile, fliese rates were 78.13, ' ' • ' ^ ' .J''^ ™'' ""''• '" '^""^ " » ' developed from 2" instars Seated with dc .s of 100, 200
EI^CTRON-BEAM IRRADIATION AS AQtlAR^TONET^Ml^AGAINSTRS) MTTE 300, and 400 Gy, respectively. We did not
observe any female adult emergence fiwn hiadiated 2"* instars at dose 300 Gy. It could be conchided that flie dose of 300 Gy might be efficient to sterilize the red mites developed from irradiated 2"* instars. Similar result was also observed by Ignatowicz and Banasik- Solgala, 1999. However, Hu et al, 2004 r^orted that flie mortality of 2°^ mstaK was 100% at dose 100 Gy after 10 days of irradiation. This might be because the tenqierature for rearing were quite different in each experiments.
Effect tlf mi^m^^^ so sur^val and reproducODn of female aduH
'HK! mortality and fle number of e g ^ o^
hradiated female adulte showed in Table IV. The mortahty rate of Mmt increased after 15 dsQiSi and reached to 100% at dose 300, 400 Qy^
Viability of eggs laid % iiiathated femal^
(tecreased wifli the nrereaseof dose. Hatching^ca^
of eggs produced by treated red mite adufts at dose 300 Gy was 4.25%. However, the nmriber 1"
instars of Fi generation didn't develop to 2"^
instars during the observed time, ft can be estimated that 300 Gy was dose required te sterilize red mites by electron beam irradiation.
Table IV. Effect of irradiation on survival and reproduction of female adult Dose
(Gray) 0 IOO 200 300 40O
Number of red mites adults
58 45 47 53 57
Mortality rate
(%)
I6.49±4.31' 55.33 ± 7.92' 77.71 ± 7.45"
IOO ±0.00' lOOiO.OO'
Number of eggs/
/female adults 2759 ±23"
256 ±12.53' 187 ±10.15"
81.67 ±9.02' 43.33 ±4.73"
Hatching rate of egss (%) 93.6 ±1.46"
63.68 ± 5,78' 41.5 ±2.08' 4.25 ±2.91' 0±0.00' Mean values within same stage followed by Ihe
W. CONCLUSIONS All elecfron beam inadiation doses used in Ulis study impeded the development of immatiire stages of red mites and caused eventual deafli m comparison wifli the conti-ol.
The survived adults after radiation were not able to create new generations. The msect immatiire stages were more sensitive to iiradiation flian the adult ones. The pattem of tolerance to uradiation m red mites was eggs <
2" instare < adults. The mortality rate of red mite adults achieved 100% at dose > 300 Oy after 15 days. The number of eggs laid by irradiated females was considerably lower than in flie confrol, and decreasing with increasing radiation dose. The 2"' mstars ofF, generation were not observed in die tieatinent involving
'e letter are not significani differeni atP=0. OS.
irradiation of adults at 300 Oy. The dose of 30J, Gy might be efficient dose to sterilize red mites infected on Chrysanthemum. However, the effect of uradiation on red mite needed implementation on large scale confirmatory tests and flie quality of exported flowers after irradiation should be evaluated.
ACKNOWLEGEMENTS We are grateful to Vietiiam Atomic Energy Instihite for financial support and encouragement to this study. We also express our smcere tiianks to The Research and Development CenKr for Radiation Technology (VINAOAMMA) for flieir advice and cooperation in the conduct of this work and the
use of irradiation facilities. ; 50
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