Impact of Psyttalia fletcheri Parasitoids on Bactrocera cucurbitae Coq. and

1
Impact of Psyttalia fletcheri Parasitoids on
Bactrocera cucurbitae (Coq.) and Bactrocera
dorsalis (Hendel) Infesting Papaya Ernest J.
Harris1, Renato C. Bautista2, Roger I. Vargas3,
and Eric B. Jang3 1US Pacific Basin
Agricultural Research Center, USDA-ARS, 2727
Woodlawn Drive, Honolulu, HI 96822 USA 2Plant
Pest Control Branch, Plant Industry Division,
Hawaii Department of Agriculture 1428 South King
Street, Honolulu, HI 96814-2512 USA 3US Pacific
Basin Agricultural Research Center, USDA-ARS,
P.O. Box 4459, Hilo, HI USA
Experimental Sites
What do our findings indicate ?
Rationale for Our Study ?

• The catch, CPTDs, from February 2004 to June
  2005 show the highest level of oriental fruit fly
  populations lt800 CPTPD in both sites in July
  2004. The CPTDs of melon fly populations in Laie
  showed six peaks lt500 CPTPD (March and November
  2004 and April, May, June and July 2005). The
  upsurge in fruit fly populations in Laie was due
  to melon fly infesting cucurbit crop remnants
  left in the field by 4-5 farmers renting the farm
  land near the wild ivy gourd. In Laie, protein
  bait traps in ivy gourd caught 3.95 fold higher
  numbers of melon fly than the protein bait traps
  in papaya. In Kuhuku, the protein bait traps in
  papaya caught 4 fold higher numbers of melon fly
  than the protein bait traps in ivy gourd. The
  protein bait traps in Kuhuku papaya caught 10
  fold higher numbers of oriental fruit fly than
  the protein bait traps in Laie papaya. Oriental
  fruit fly and melon fly females were caught at
  all trap sites in protein bait traps. The farmers
  shifted to non cucurbit crops in mid 2005 after
  finding out how severe fruit fly infestations in
  cucurbits can be without high use of costly
  pesticide control measures.
• (2) The number of P. fletcheri parasitoids
  recovered from puparia infesting papaya in Laie
  was very low. No emergence of P. fletcheri from
  papaya fruits was recorded. Seven hundred and
  seven F. arisasnus parasitoids were recovered
  from a total of 2,927 papaya puparia in Laie that
  produced 1,189 oriental fruit fly and 31 melon
  fly. This evidence shows that melon flies moved
  from ivy gourd into papaya infesting them at a
  low level. The significant numbers of F.
  arisasnus produced came from oriental fruit fly
  infesting papaya its primary host in the natural
  habitat.

In Hawaii, the Mediterranean fruit fly (Ceratitis
capitata) Wiedemann, the oriental fruit fly,
(Bactrocera dorsalis) Hendel and the Solanaceous
fruit fly (B. latifrons) Hendel, are persistent
pests of fruits and vegetables. Voracious feeding
by the larvae causes fruit to decay, thus
rendering it unfit for human consumption.
Recently, an IPM program was undertaken jointly
by USDA-ARS, the University of Hawaii and Hawaii
Department of Agriculture to demonstrate the
potential of utilizing a package of control
tactics, including biological control for
suppression of fruit flies. The IPM program has
provided an opportunity to assess and to quantify
the potential impact of parasitoid augmentation
when utilized alone as a strategy for suppression
of fruit flies. In 2003, 2004, and 2005 open
field releases of Fopius arisanus and Psyttalia
fletcheri (egg and larval parasitoids
respectively) were made in Laie, Hawaii. Kuhuku,
HI served as a control site. The two North shore
sites are not identical but have comparable field
sizes, stands of fruit-bearing papayas, and
matching patches of wild vegetation of Coccinia
grandis (ivy gourd) infested by melon fly. Wild
ivy gourd serves as a major source of melon flies
that infest cultivated crops grown near our
experimental sites. The relative abundance of
melon fly and oriental fruit fly populations in
our experimental sites was monitored with a) male
lure and protein bait traps and b) emergence of
flies and parasitoids from from infested ivy
gourd and papaya fruits. The fruit fly trap data
(expressed as catch per trap per day, CPTD) were
supplemented with parasitoid emergence and host
pupal mortality data generated from ivy gourd and
papaya fruit collections. An update on the
progress of our research in papaya is
presented.
Experimental Sites
Kuhuku Control Site
Laie Release Site
Servicing male lure traps
Fig 1
Fig 2
Experimental Approach Small-scale field releases
of the fruit fly parasitoid F. arisanus and P.
fletcheri were carried out during the period
March to August in 2003, 2004 and 2005 in Laie
for augmentative biological control of Melon fly
infesting wild ivy gourd. Within a short distance
(0.5-3.5 km) from the release and control site, 3
orchards of papaya were monitored for melon fly
and oriental fruit fly populations with male lure
and protein bait traps. Also, fruit samples were
collected monthly to monitor fruit fly
infestation of papaya and parasitization of fruit
fly pupae by P. fletcheri and F. arisanus. Papaya
fruits that fell from the trees were sampled and
placed on the ground under a plastic box (0.5
m2)) to record emergence of flies and
parasitoids from papaya fruit samples. The
insects which emerged from papaya fruit were
caught in stickem inside a plastic bucket on top
of the emergence box. To improve the latent
effectiveness of the parasitoids released, they
were fed honey and males and females were held
together for 5-6 days before release to ensure
sexual maturity and mating before release. This
procedure insures that the parasitoids are ready
to search for and parasitize fruit fly hosts in
ivy gourd and papaya fruits immediately after
release in the field.
Placing fallen papaya fruit samples in field
emergence boxes
What May Be Gleaned From The Study The abundance
of melon fly and oriental fruit fly populations
can be monitored effectively with male lure traps
and the impact of parasitoid releases on fruit
fly infestation assessed by analyzing trends
in the recovery of both tephritid fruit flies and
parasitoids (P. fletcheri and F. arisanus) from
infested fruit. Fruit fly trap data and fruit
fly and parasitoid recoveries were identified by
habitat where the flies and parasitoids were
abundant and where the most damage was done to
cucurbit and papaya crops. Release of the
parasitoids effectively suppressed melon fly
infesting ivy gourd but the parasitoids were less
effective in competition against melon fly
infesting crop remnants in abandoned fields of
ripe cucurbits left unattended by growers.
Although, oriental fruit fly infested papaya,
when this fruit is harvested from the trees
promptly at the mature green stage, and fallen
fruit is removed and not permitted to accumulate
on the ground under the trees, infestation of
papaya by oriental fruit fly is greatly reduced
by cultural control. Augmentative releases of the
two parasitoids had major impact suppressing
melon fly infesting ivy gourd but little impact
on oriental fruit fly infesting papaya.
Fig 4
Fig 3
(3) In Laie from January 2003 to June 2005, the
number of oriental fruit fly and F. arisanus
parasitoid counts recovered from papaya showed 2
peak counts of 100, June to July 2003 and
June to July 2004. From September to October,
November to December 2003, and November to
December 2004 the oriental fruit fly and F.
arisanus counts recovered from papaya ranged
from 50 to 60. The most important counts recorded
were the numbers of unemerged and total pupae.
Three count peaks occurred. The first occurred in
September 2003, the second in June 2004 and the
third in November 2004. The high total numbers of
unemerged pupae recovered were due to pupae death
caused by parasitoid releases especially F.
arisanus . (4) In Kuhuku, September 2003,
October 2004 and January 2005 oriental fruit fly
counts recovered from papaya exceeded 100. In
November and December 2003, August, November and
December 2004, F. arisanus parasitoid counts
recovered from papaya did not exceed 50. Again,
the most important counts recorded were the
numbers of unemerged and total pupae. Three
unemerged pupae counts ranged in descending order
showed counts of 565, 180, and 102. Corresponding
total pupae counts were 682, 297, and 180. The
first count occurred in September 2003, the
second in June 2004 and the third in November
2004. The high numbers of unemerged pupae
recovered were due to pupal mortality caused by
wild F. arisanus parasitoids. No parasitoid
releases were made in Kuhuku.