Washington Tree Fruit Research Commission

Research Reports

Re-evaluation of Host Usage By Apple Maggot in Washington (2004)

FINAL PROJECT REPORT
WTFRC Project #AE-02-217
YEAR 0/0
Organization Project #
Title:Re-evaluation of Host Usage By Apple Maggot in Washington
PI:Wee Yee
Organization:USDA-ARS, 5230 Konnowac Pass Rd Wapato, WA 98951 509-454-6558 / wlyee@yarl.ars.usda.gov
 PDF version of report

Objectives

2002
●          Determine trap catches of apple maggots on previously unrecorded, non-apple hosts, in western Washington.
●          Determine if apple maggots develop in these new hosts and the sites where this occurs.

2003
●          Further determine trap catches of apple maggots on previously unrecorded, non-apple hosts, in western Washington.
●          Further determine if apple maggots develop in these new hosts.
●          Determine longevity and fecundity of apple maggots from different hosts.

Significant findings

2002 Significant Findings
●          Adult apple maggots were collected on traps placed on a wide variety of previously unrecorded hosts in western Washington, including Asian pear, pear, and rose.
●          Asian pear, Pyrus serotina, was confirmed to be a new apple maggot developmental host in Washington in 2002.
●          Fly pupae were recovered from Asian pear, pear, plum, rose, and native cherries in 2002.

2003 Significant Findings
●  Adults developed from pupae collected from bitter cherry, Prunus emarginata;  this is a new host for the apple maggot.
●  Adults developed from pupae from common pear, Pyrus communis; this is a new Washington state record; pupae were collected from pear at three disparate locations.
●  Pupae were collected from Asian pear for a third straight year, confirming that this host is consistently used.
●  Plums, Prunus domestica, yielded high numbers of pupae that will probably be apple maggots; pupae were also collected from spreading cotoneaster, Cotoneaster divaricatus.  Rearing the adults out in the winter and spring of 2004 will confirm whether these are apple maggots – studies are still in progress.

Methods

2002-2003 Methods:
  1. Sticky yellow traps were placed in Asian pear, pear, rose, cascara, plum, and other trees in Cowlitz, Clark, and Skamania Counties from July through September 2003.  Cultivated and native wild cherries were also trapped.  Traps were placed in apple, hawthorn, and crabapple trees, the known hosts in Washington, for comparative host use purposes.  Several sites 100 km apart were surveyed to establish that infestations on non-apple hosts are not limited to just a few trees or localized sites.  Flies were removed from traps every 1 to 3 weeks and identified.
Representative fruit from all trapped trees were collected and brought into the laboratory. Larvae dropped from the fruit into a moist vermiculite/peat moss/sand mixture. After 1-2 weeks at room temperature, the pupae were placed in a 3-4 °C refrigerator where they will be held for 5-6 months. Flies will be brought up to room temperature (25-27 °C) for emergence.  After emergence, flies will be maintained on a diet of 20% yeast and 80% sugar.  Longevity and fecundity of flies from new hosts will be compared with those of flies from known hosts (apples and hawthorn).  Wax domes will be used as oviposition sites to collect eggs.  After all flies die, they will be positively identified as apple maggot using wing band patterns, ovipositor lengths, and male reproductive morphology (Bush 1966, Westcott 1982).

Results

 Adult apple maggots were trapped on many non-apple hosts in 2002 and 2003, although not all appeared to be developmental hosts.  Five of these - Asian pear, common pear, bitter cherry, spreading cotoneaster, C. divaricatus, and plum – appeared to be or were developmental hosts (Table 1).  Many fruit fly pupae (some clearly were the western cherry fruit fly, Rhagoletis indifferens Curran) were collected, but only those that emerged as adults could be confirmed to be apple maggots.  Asian pear (cv. ‘20th Century’ and ‘Kosui’) was a developmental host in all three years from 2001-2003, and was a host at 3 of 4 sites.  Common pear (cv. ‘Bartlett’) was a host at 4 of 7 sites and native bitter cherry (feral) was a host in 2002 at 2 sites (80 km apart) out of 13 total sites.  Cotoneaster was a host at 1 of 6 sites (C. microphilus and C. horizontalis were not infested), and plum, Prunus domestica  (cv.‘Green Grange’) was a host at 3 of 6 sites.  In at least 2003, these hosts were less infested than the known hosts.   Other fruit produced fruit fly pupae that resembled apple maggot (i.e., rose maggot, Rhagoletis basiola [Osten Sacken] from rose), but most pupae from other hosts failed to emerge, and thus these were unconfirmed or non-hosts (Table 1).  Flies from all the newly identified hosts had similar ovipositor lengths (0.91-1.07 mm) as flies from apples (Westcott 1982).  Flies that developed in new hosts were as large as flies from apples, but the longevity and fecundity of flies from these hosts have not been determined.  Adult flies from the new hosts are expected to emerge, after 5-6 months storage at 3 ºC, in winter and spring 2004.  Longevity and fecundity will be determined at this time.

Discussion

 Knowing the host use range of apple maggot is important because it determines which hosts need to be considered as potential sources of infestation in commercial orchards.   The apple maggot is a major threat to the apple industry in Washington.  Currently, it is restricted to western Washington, the Spokane area, and Ellensburg and sporadic catches occur in Yakima and Tri-Cities areas.  To delimit its spread and to eradicate its local populations, the Washington State Department of Agriculture runs an active apple maggot surveillance program.  Traps are normally placed in apple and hawthorn trees to detect fly presence.  If a fly is caught, the County Pest Control Board immediately sprays the trees with the organophosphate phosmet.  The results in this study suggest that traps may need to be placed in abandoned and unsprayed Asian pear, pear, bitter cherry, and specific shrubs such as cotoneaster in areas with apple maggots on previously known hosts.

 

In Washington, the apple maggot reportedly “has been found only on apple, crab apple and hawthorn” (Beers et al. 1993, Brunner 1996).  The results reported here clearly show the fly has a broader host range than this in Washington.  This is not surprising, as in other regions of the U.S. apple maggot attacks a wide range of hosts in the rose family (e.g., Bush 1966, Shervis 1970, Prokopy and Bush 1972, Prokopy and Berlocher 1980, Tracewski et al. 1987, Allred and Jorgenson 1993).  The finding of apple maggot usage of pear is important because of the large pear industry in central Washington.  Should apple maggots ever become established in this region, both apples and pears may be subject to attack by this fly.  This would make eradication efforts more difficult.  Fortunately, at this time, infestation of pear even in high apple maggot population areas seems relatively low.  Nevertheless, because apple maggots do use pear and other hosts in Washington, trapping efforts made by the state to delimit the fly’s spread may need to include alternate hosts.   

 


Table 1.  Numbers of fruit fly pupaea and adult Rhagoletis pomonella reared from various fruit collected in southwestern Washington State, 2001-2003.

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                                                                                                                                                                                                                                                                                                        Total Numbers

                                                                                                                                                                                                                                                                                    2001b                                                                                                               2002                                                                                                                                                                            2003

New Hosts in WA                                                        Pupae               Adultsc             Fruit                             Pupae               Adultsc                         Fruit                             Pupaed             Adultsc

Asian Pear                                                                                                                    161                                                      7                                                                        153                                          68                                                       0                                                                      216                                                      66                                                        -------

                                                                                                                                                                                                                                                                                                                                                                        ----                                          33e                                           16                                           

Common Pear                                                                                     24                                                        0                                                                                  332                                          36                                                        2                                                                      347                                                      32                                                        -------

Bitter Cherry                                                                                                    ----                                                      ----                                          2,807                           2                                                                      2                                                                      8,761                                       ------                           -------

Cotoneaster                                                                                                                 ----                                                      ----                                                120                                          1                                                                      0                                                                      3,224                                       5                                                                      -------

Garden Plum                                                                                                    ----                                                      ----                                          30                                                        0                                                                      0                                                                      419                                                      316                                          -------

Known Hosts in WA

Apple                                                                                                                                                   575                                                      13                                                        44                                                        33                                                        0                                                                      883                                                      459                                          -------          

Black Hawthorn                                                                                   100                                                      6                                                                      2,095                           371                                          65                                                        5,194                                                442                                          -------

Ornamental Hawthorn                           665                                                      3                                                                      ----                                                ----                                          ____                            12,079                         502                                          ------- 

Crab Apple                                                                                                                  187                                                      6                                                                        88                                                        100                                          ____                            379                                                      32                                                        -------

Unconfirmed or Non-Hostsf

Red Plum                                                                                                                                 ----                                                      ----                                          28                                                        6                                                                      0                                                                        -------                                      -------                          -------

Italian Plum                                                                                                       -----                                                     ----                                          80                                                        0                                                                      0                                                                      -------                                      -------                          -------
Rose                                                                                                                                                                            95                                                        0                                                          394                                                      5                                                                      0                                                                      2,925                                       52                                                        ------- 
Quince                                                                                                                                                             1                                                                      0                                                          111                                                      1                                                                      0                                                                      86                                                                    0                                                                        -------
Snowberry                                                                                                                               237                                          0                                                            -----                                         ------                           ------                                       --------                                 -------                          ---------
Cascara                                                                                                                                                            7                                                                      0                                              3,885                                                   0                                                                      0                                                                      5,514                                       0                                                                      0

Blueberry                                                                                                                                 ------                           ------                                       87                                                        0                                                                      0                                                                      -------                                      -------                          -------

Red Huckleberry                                                                      ------                           ------                           120                                                      1                                                                      0                                                                      -------                                      -------                          -------

English Laurel                                                                                       ------                           ------                           ------                           -------              -------                                                  1,772                                       0                                                                                  0

Sweet/Sour Cherries                                         -------              ------                           808                                                      0                                                                        0                                                                      1,260                                       0                                                                                    0

Blueberries                                                                                                                   -------                          ------                           ------                           -------              -------                                                  877                                                      0                                                                                    0

Grapes                                                                                                                                                 -------                          ------                                    ------                           -------              -------                                                  1,118                                       0                                                                                  0

Skimia                                                                                                                                                  -------                          ------                                    ------                           -------              -------                                                  217                                                      0                                                                                  0

Yew                                                                                                                                                                 -------                          ------                           ------                           -------              -------                                                  115                                                      0                                                                                  0

Honeysuckle                                                                                                     -------                          ------                           ------                                    -------              -------                                                  184                                                      0                                                                                  0

Bush Cranberries                                                                      -------                          ------                           ------                           -------              -------                                                  320                                                      0                                                                                  0

Pyracantha                                                                                                                   -------                          ------                           ------                           -------              -------                                                  566                                                      0                                                                                    0

Holly                                                                                                                                                                -------                          ------                           ------                           -------              -------                                                  265                                                      0                                                                                  0

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-------, data not collected.

aIncludes only pupae that had the appearance of R. pomonella, but not all emerged as adults.

bFruit not counted in 2001.

cEmerged and confirmed as adult R. pomonella.

dIn cold and in diapause; emergence expected in winter-spring 2004.

eCollected from soil directly beneath an Asian pear

fCollected near known hosts.

Literature Cited

Allred, D. B. and C. D. Jorgenson.  1993. Hosts, adult emergence, and distribution of the apple maggot (Diptera: Tephritidae) in Utah. Pan-Pacific Entomol. 69: 236-246.
Beers, E. H., J. F. Brunner, M. J. Willett, and G. M. Warner.  1993.  Orchard Pest Management. A resource book for the Pacific Northwest. Good Fruit Grower, Yakima, WA, 276 pp.
Brunner, J. F.  1996.  Experience with apple maggot in the western United States, pp. 81-86.  In M.T. AliNiazee and L. E. Long [eds.], Biology and control of the cherry fruit flies: a worldwide perspective, Proceedings of the International Cherry Fruit Fly Symposium, 1995, The Dalles, OR.

Bush, G. L.  1966.  The taxonomy, cytology, and evolution of the genus Rhagoletis in North America (Diptera, Tephritidae). Harvard Univ. Bull. Mus. Comp. Zool. 134 (11): 431-562.
Prokopy, R. J. and G. L. Bush. 1972.  Apple maggot infestation of pear. J. Econ. Entomol. 65: 597.
Prokopy, R. J. and S. H. Berlocher.  1980. Establishment of Rhagoletis pomonella (Diptera: Tephritidae) on rose hips in southern New England. Can. Entomol. 112: 1319-1320.
Shervis, L. J., G. M. Bousch, and C. F. Koval. 1970.  Infestation of sour cherries by apple maggot: confirmation of a previously uncertain host status.  J. Econ. Entomol. 63: 294-295.
Tracewski, K. T., J. F. Brunner, S. C. Hoyt, and S. R. Dewey.  1985. Occurrence and development of Rhagoletis pomonella (Walsh) in hawthorns, Crataegus, of the Pacific Northwest (USA). Melanderia. 45: 19-25.
Westcott, R. L.  1982.  Differentiating adults of apple maggot, Rhagoletis pomonella (Walsh) from snowberry maggot, Rhagoletis zephyria Snow (Diptera: Tephritidae) in Oregon.  Pan Pacific Entomol. 58: 25-30.

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