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DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

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Page 1: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

ENTOMOLOGlA SINICA Vol .8, No. 2, June 2001 , pp .175-182 175

DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA : TEPHRITIDAE) IN YUNNAN PROVINCE *

YE Hui Institute of EcorOgY and Geobotany , Yunnun University, Kunming , 650091 , China (Received May 22, 2000; accepted Sep. 1, 2000)

Abstract The Oriental fruit fly, Bactrmra dorsalis Hendel (Diptera: Tephritidae) , is a serious pest insect for vegetables and fruits in Yunnan Province. The trap experiments located in 12 counties of Yunnan indicated that, the geographical distribution of Oriental fruit fly there could be plotted as three distribution zones. To the south of Guan- nan, Yuanjiang and Rulin is the annual distribution zone. In this region, the Oriental fruit fly completed 4 - 5 gener- ations per year, and infested the local vegetables and fruits all the year around. To the north of Luku, Dayiao and Qujing is the zone without the insect, where the Oriental fruit fly was not trapped and no fruits infested by the fly were found during the present study. The region between the above two zones was the seasonal distribution zone for the in- sect. The fruit fly occurred only during May to December in this area, and completed 2 - 3 generations in this period. The peak abundance of the oriental fruit fly took place from June in Jinghong to October in Yiaoan, along the altitude graduates from the south to the north. In elevation, the Oriental fruit fly was trapped at altitude of 500 - 2300 m above sea level, in which high trap catches appeared between 500 - 1 OOO m. It is proposed that the variations of the fruit fly distribution in altitude and latitude are principally correlated with local temperatures and host plants.

Key WO& Bactrocera dorsalis Hendel, population distribution, Yunnan

1 INTRODUCTION

The Oriental fruit fly, Buttrocera dorsalis Hendel (Diptera: Tephritidae) , infests more than 150 species of fruits and vegetables worldwide and is considered as a dangerous pest in most countries (Vargas and Janmes 1990) . Many studies have been conducted on the Oriental h i t fly, including aspects of infestation rate, host range, and population dynamics (Christenson and Foote 1960, Bess et al . 1963, Wong et al . 1983, Vargas 1989, Zhang et al . 1995). In the insect pest control, pheromone trapping has been extensively used ( Narayananet et al . 1989, John et al . 1990, Zhang et al . 1995) . The sterile male tactic has also been developed to erad- icate the fly in local areas (Langley et al . 1972) . However, quarantine inspection and treat- ment is still the principal method used to prevent the movement of this fly into uninfested areas both within and between countries (Toshiyuki et al . 1980, Zhang et al . 1995) .

In Yunnan Province in southwestern China the Oriental fruit fly is also regarded as a very serious agricultural pests (Zhang et al . 1995). In this region, tropical fruits like mango, peach, pear, citrus and papaya play a very important role in the local agricultural economy. However, fruit production in Yunnan has increased little in recent years due largely to infesta- tions of the Oriental fruit fly (Zhang et al . 1995) . In Yuanjiang district of Yunnan, for exam- ple, more than 30% of the annual mango production has been lost due to this fruit fly (Zhang et al . 1995) , This fly has proved difficult to control for many years, and thereby seriously hinders

* The project supported by Natural Science Foundation of Yunnan.

Page 2: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

176 ENTOMOLOGIA SINICA Vol. 8, No. 2 , June 2001

Localities

further development of tropical fruit production in Yunnan. An integrated pest management program for the Oriental fruit fly was developed by the Yun-

nan provincial government in the late 1990' s . As one of the first steps in this program, a re- search project was initiated to obtain knowledge on the geographical distribution and seasonal oc- currence of the Oriental fruit fly in Yunnan.

2 MATERIALS AND METHODS

Altitude Latitude Longitude T' T1 T' I n m

A field experiment was carried out during 1997 - 1998 in 12 counties that cover the current distribution of the Oriental h i t fly in Yunnan (Table 1 ) . In each county, 2 - 3 fruit orchards were selected, representing the principal cultivated fruit species grown in that county. Five to six pheromone traps were placed throughout each orchard. Traps were placed on the fruit trees at a height of 2 m . The trap was made from a plastic bottle, 20 cm long and 8 cm in diameter. The bottle was open at the top and contained water mixed with insecticide in the bottom. A phero- mone lure was suspended from inside each bottle, near the center. The lure consisted of a small wood ball soaked with Methyleugenol and Cue-lure, which is commercially produced by the In- stitute of Jingtang Pheromone. During one-year collection period of this experiment, the lures were replaced at 1-month intervals. The fruit flies were attracted by the lures and entered the traps. When the flies fell into the water, they were quickly killed by the insecticide. The traps were emptied and the dead flies were counted at 2-week intervals. In addition, extensive investi- gations were conducted in vegetable gardens that were near to each of the orchards in the study. Injured fruits from these gardens and orchards were taken to the laboratory and the fruit flies that emerged from the injured fruits were identified.

Table 1 Data of geography, climate and annual captures in 12 trapping localities in 1997 - 1998,Yunan.

Jinghong

Yuanjiang

Guangnan

Eshan

Ruli

Anning

Qujing

Baoshan

Yao'an

Luku

Da'yiao

Bingchuan

550m

501m

1160m

1 lOOm

790m

1804m

2000m

1 lOOm

2350m

930m

2 5OOm

1 438m

22"00 ' N

23'21"

23'54 ' N

24"20 ' N

24004 ' N

24'40"

25"21' N

25'30"

25'1 1 ' N

25'03 ' N

26'02 ' N

25'50 ' N

100'46 ' E

101'59'E

195'20 ' E

102'24 ' E

9794 ' E

102'20 ' E

104023 ' E

99'10'E

lOl"O5 ' E

99'02 ' E

100'10'E

lOO"34 ' E

22.0

23.7

16.7

18.9

20.5

14.7

14.5

15.5

15.2

15.0

14.6

17.9

16.5 4.2

16.5 3 . 8

8.6 - 5 . 2

8.7 - 4 . 4

13.2 1.2

7.1 - 6 . 4

7.0 - 6 . 4

8.2 - 3 . 5

7 .9 - 5 . 2

9.0 0 .6

7.8 - 4 . 8

- 6 . 2 -

2142

4295

42

176

1813

156

82

- 54

- 0

0

June

J ~ Y

July-Aug . July- Aug .

June

Sept . -0ct .

Sept . -0ct.

Sept . -0ct .

Oct . Aug . -Sept.

- -

5

5

3 - 4

3 - 4

4 - 5

2 - 3

1 - 2

1 - 2

1 - 2

2 - 3

0

0

T' : Average annual temperatures( T ) . T' :Average temperatures for the coldest month( T ) .T' : Daily minimum temper- atures( 't ) .I : Average annual captures from 4 orchards in the same locality. II : Month of peak fly abundance. m : Num- ber of generation per year. * :Shortage of some trapping data due to trap set damages.

Page 3: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

Ye H: Distribution of the Oriental fruit fly 177

3 RESULTS AND ANALYSIS

3.1 The geographical distribution of Oriental fruit fly in Yunnan was developed from data col-

lected in the current investigation as well as from past publications (Fig. 1 ) . Three zones were plotted to represent the distribution of this fly in Yunnan . Zone 1 represents the region where the Oriental h i t fly was not trapped during the present study. Zone 2 is a relatively narrow region located in central Yunnan where the Oriental fruit fly was trapped only during the period from June to December. Apparently, the Oriental fruit fly cannot survive the winter months in zone 2 (Zhang et al . 1995) . Flies found in zone 2 result from flies that migrate in from zone 3 , begin- ning in late spring. In late autumn, as temperatures decrease, the flies in zone 2 either migrate out of the area or die. Therefore, zone 2 represents a region of seasonal occurrence during the warmer months of the year. Zone 3 covers almost the entire area of southern Yunnan. Many fruits and vegetables are grown year-round in southern Yunnan, and thus this fruit fly can easily find suitable hosts throughout the year. As evidence of this year-long occurrence is the fact that Oriental fruit flies were collected each month during the present study in Zone 3. Therefore, it is clear that zone 3 serves as the main reservoir of the Oriental fruit fly in Yunnan.

Topographically, central Yunnan is a plateau with an average elevation of 2 OOO m above sea level. Numerous mountain ranges are found in Yunnan , covering 90 % of the land. Two large mountain ranges slope gradually from central to southem Yunnan, where there occurs a plain and small hill complex with an average elevation of about 500 m. Steep valleys are found between the mountain ranges that commonly dip to elevations of about 300 m. The Oriental fruit fly was trapped between elevations of 200 m to 2 300 m . The largest collections of Oriental fruit fly in the present study were made between elevations of 200 m to 1 000 m. At elevations above 1 000 m , the average number of flies collected per trap progressively decreased (Table 1 ) . Very few Oriental fruit flies were collected at elevations above 2 350 m . Apparently, elevations above 2 400 m do not support this fruit fly in Yunnan Province. Flies were found at elevations below 2 400 m as long as suitable host plants were found. Meanwhile, no trap catches were recorded in past data at elevation above 2 400 m (Zhang et al . 1995) . Apparently there was no lower eleva- tional limit for this fruit fly in Yunnan.

The spatial distribution of the Oriental fruit fly appeared to be strongly influenced by tem- perature. It was reported a lethal threshold temperature of 2 "c for the Oriental fruit fly ( Vargas 1989 ) . Average temperatures were, of course, markedly affected by elevation. For example, for each 100 m increase in elevation, average annual temperature decreased by an average of 0.5"c in Yunnan . Along this elevational gradient, the average trap catch declined gradually with in- creasing elevation ( Table 1 ) . Where elevations exceeded 2 400 m , daily minimum temperatures frequently fell below 0°C in winter, which was likely lethal to the Oriental fruit fly. Therefore, the average daily minimum temperatures, as well as elevation, appear strongly related to the dis- tribution of this fruit fly.

Average annual temperatures also changed with latitude. For exhple , for two sites with the same elevation (1 100 m) , the average annual temperatures were 18.9"c in Eshan (24'20'

The geographic distributions of the Oriental fruit fly

Page 4: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

178 ENTOMOLOGIA SINICA Vol. 8 , No. 2 , June 2001

Fig.1 Geographic distribution of the Oriental fruit fly in Yuanna. Zone 1 represents the same without the fruit fly distribution. Zone 2 is for the seasonal

distribution of the fruit fly. Zone 3 is corresponding to the annual distribution of the fruit fly.

N ) and 15.5% in Baoshan (25’30”) (Table I ) . In most localities within zone 2 , the average temperature for the coldest month was normally below 8°C , and the average daily minimum tem- perature during the coldest month was beneath 0°C . Such low temperatures help to explain why this fruit fly was unable to survive in zone 2 during the winter.

3.2 More than 100 plant species have been recorded as hosts for the Oriental fruit fly in Yun-

nan (Zhang et a1 . 1995). Of these, about 20 h i t s and vegetables, such as mango, pear, peach, grape, pineapple, plum, watermelon, were widely grown in Yunnan and were common host plants for this fruit fly.

Table 2 summarizes the major host plants infested by the Oriental fruit fly in each of the trapped counties. The host plants in zone 3 were mainly tropical fruits such as mango, bananas, papaya, pineapple, watermelon , and citrus. In zone 2 , the most common host plants included citrus, pear, peach, teak, plum, grape, and apple. Some vegetables, such as pumpkin and tomato, also served as host plants in zone 2. These vegetables were normally planted on a smal! scale around villages in zone 2. Some wild fruits like wild berries were also infested by this fruit fly. These wild bemea grew sparsely in the understory of different forest types. Overall, the Ori- ental fruit fly had greatest number of host plants in zone 3.

Host plants and their distributions

Page 5: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

Y e H: Distribution of the Oriental fruit fly 179

Table 2 The main host plants of the Oriental fruit fly in 13 trap counties in Yunnan, China.

Locality

Mongna

Jinghong

Heko

Yuanjiang

Eshan

Wuanding

Guangnan

Anning

Q u h

Baoshan

Yao’an

Da’ yiao

Luku

Host plants

Mong&wa id ica , Mwaceae nana , Carica papaya, Ananaa comsw , C W w laratw, Lycoper- sicon esculentum

M o d e r a indica , Mwaceae nana , Carica papaya, A n a m comsw , Litchi chinemk, Citrus li- m n i a , Citrullw laratw , Lycopersicon esculentwn

Carica papaya, Ananas comosw , Punica granatum, Citrus reticulata, Citrdlw hatw

Mongrrera indica , Citrus re t ida ta , Prunw persica , Ananaa comsw , Citrullw laratus, Lycoper- sicon esculentum

Mongryera indica , Citrus reticulata , Carica papaya, Ziayphw stativa, C i t d l w hratw , Lycoper- sicon esculentum

Ananas comosw , Citrus reticulata , Prunus persica , Punica granatum , Cimdlw laratus

Citrus reticulata , Prunw persica , P p pmhiu , Punica granatwn , Citrus grandis, h w ar- meniaca , Citrullw laratus, Eriobotrya japonica

Prunw persica , P p pashia , Vitk lanata , Citrus reticuluta , Malw pwnila , Capsicwn annu- um, Vitk lanata

Citrus reticulata, P p pcrshia , Prunw persica , Malw pwnila , Capsicwn annuwn , Vitk lanata

Citrus reticdata, P p pashiu , Prunw persica , Prunus salicina , Capsicum annuum Citrus reticulata , P y m pcrshia , Prunw persica , Malw pumila , C i a limonia , Citrus reticulata , P p pashiu , Prunw persica , Prunus salicina , Capsicum annuum

Citrua reticdata, P p pashin, Prunw armeniaca , Citrus grandis Prunw salicina , Capsicwn annuurn, Citrullw lanatw

I t is the fruit of the host plants that serves as the substrate for oviposition and larval devel- opment. The fruiting periods in Yunnan for some of the major host plants are presented in Table 3. In general, the fruiting period for most host plants occurred during the summer and autumn months (Table 3) . However, the actual period of fruiting varied by county and was related to lo- cal climatic conditions. In Jinghong (550 m) , for example, the occurrence of citrus fruit took place one month earlier than in Qujing (2 OOO m) . In tropical areas like Jinghong , one or more host plants produce fruit throughout all seasons of the year. Such overlap provides this fruit fly with a nearly continuous supply of suitable material for reproduction.

In addition, for any given host plant, the timing of fruiting can vary widely by cultivar or variety. For example, in Yuanjiang, there are more than 6 cultivated varieties of mangos, among them the differentiation of fruiting periods was from one week to one month. Where differ- ent varieties grow in the same region, such varietal differences in fruiting period can, in practi- cal terms, lengthen the time that reproduction and development can occur on a given host.

Page 6: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

180 ENTOM0UH;IA SINICA Vol. 8, No. 2 , June 2001

Table 3 Fruiting periods for the principal host plants of the Oriental fruit fly in Yunnan. Month

1 2 3 4 5 6 7 8 9 10 11 12 Host plant

P .pas& + + + + P . persica + + + P . granatum + + + V. hmm + + + + + + +

C.reticulata + + + M . indica + + +

E . japonica + + M.mm + + +

A . comosw + + + + C . lanatw + + + + +

L . escuknturn + + + + + + + + + + papaya

3.3 The total number of Oriental fruit flies collected per county per year varied greatly by local-

ity. In general, total trap catch increased with decreasing latitude (Table. 1 ) . For example, the annual catch at Jinghong (22'00' N ) averaged 2 142 adults per orchard during the 12-month pe- riod from spring 1997 to spring 1998, whereas the average catch at Qujing (25'21 ' N ) was 82 adults per orchard. In general, average annual trap catch per orchard was higher in zone 3 than in zone 2 (Table 1 ) .

The apparent correlation of latitude with the average annual catch per orchard suggests a re- lationship between fly abundance and the number of generations completed per year in each county. Number of generations per year ranged from 2 in Qujing to 5 in Jinghong , which was in- versely proportional to latitude (Table 1 ) . In Yunnan, the Oriental fruit fly appeared to com- plete 5 generations per year at latitudes less than 24"00'N, but only 2 or 3 generations per year were completed at latitudes greater than 24'40' N (Table 1 ) . These additional two generations per year at the more southern latitudes in Yunnan occurred during the winter and spring months, and are probably in large part responsible for the higher annual catch of fruit flies. Moreover, these additional two generations per year allow for the presence of adult Oriental fruit flies year- round. In those Yunnan counties that lacked the winter and spring generations, the average trap catch of adult flies appeared to be related in large part to when adult immigration first occurred in spring, as well as the numbers and kinds of host fruits that were available in summer and au- tumn. In addition, host fruits were often limited at the higher latitudes, and this may have also influenced the average trap catch at the higher latitudes compared with the lower latitudes (Table

Within the same climatic zone, the abundance and species of host plants is likely an essen- tial factor affecting population dynamics of the Oriental fruit fly. For example, at about the same elevation within zone 3, Jinghong is about 200 km south of Yuanjiang . Given this spatial differ- ence it would seem reasonable that more adults could be captured in Jinghong than in Yuan-

Abundance and fluctuation of the Oriental fruit fly

1 ) .

Page 7: DISTRIBUTION OF THE ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) IN YUNNAN PROVINCE

Ye H: Distribution of the Oriental fruit fly 181

jiang . However, the opposite occurred (Table 1 ) . This apparent contradiction may be partially explained by the fact that Yuanjing has 10 times more land area in mango production than does Jinghong, as well as the fact that mango is one of the most preferred hosts of the Oriental fruit

fly * The mean annual trap catch at a given locality was positively related to the estimated num-

ber of fruit fly generations per year and the amount of host fruit production. The largest number of flies collected per month occurred most commonly during the summer and autumn months (Ta- ble 1 ) . This seems reasonable that it is during the summer and autumn months when fruit is most abundant and when w m temperatures support rapid fly development. Nevertheless, the actual month of peak catch varied from south to north, as a result of temperature variation due to both latitude and elevation. For example, peak trap catches occurred in June at Jinghong in southern Yunnan , and during October in Qujing in northern Yunnan (Table 1 ) . Acknowledgments The author wishes to extend his great thanks to the Dr. Robert A . Haack working in USDA Forest Service, North Central Research Station for this scientific com- ments and English correction. Thanks are also given to LI Hong-xu working in Kunmig Forestry Station for his assistance in fieldwork.

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182 ENTDMOMGIA SINICA Vol. 8, No. 2 , June 2001