BACKGROUND

1
Irradiation to Control Quarantine Pests in Sweet
Potatoes Exported from Hawaii Peter A. Follett
USDA-ARS Pacific Basin Agricultural Research
Center, PO Box 4459, Hilo, Hawaii 96720

• BACKGROUND
• Hawaiis vegetable growers produce several
  unique varieties of sweetpotatoes Ipomoea
  batatas (L.) Lam., including a purple-fleshed
  type.
• Sweetpotato growers are unable to ship
  sweetpotatoes to the U.S. mainland without a
  quarantine treatment because of three quarantine
  pests. West Indian sweetpotato weevil (A),
  Euscepes postfasciatus (Coleoptera
  Curculionidae), and the sweetpotato vine borer
  (B), Omphisa anastomosalis (Lepidoptera
  Pyralidae), are federal quarantine pests, and the
  sweetpotato weevil (C), Cylas formicarius
  elegantulus (Coleoptera Curculionidae), is an
  actionable pest for California.
• Until recently, growers were exporting
  sweetpotatoes to the U.S. mainland using methyl
  bromide fumigation to control these pests.
  Irradiation was evaluated as an alternative
  treatment.
• Based on preliminary research and information on
  effective doses for related species, USDA-APHIS
  approved a high dose of 400 Gy to export
  sweetpotato from Hawaii to the U.S. mainland.
• This was the first time APHIS considered the
  high-dose approach for controlling a quarantine
  pest complex until research is completed to
  confirm a lower dose.

vine borer damage

• Various ages and life stages were irradiated to
  determine the most tolerant stage. Large-scale
  confirmatory tests focused on the most tolerant
  stage for each species. The required response was
  no production of F1 adults.
• Fig. 1. (A) Mean emergence of adults after
  treating immature sweetpotato vine borer of
  various ages with an irradiation dose of 100 Gy.
  (B) Mean emergence of adults after treating
  immature West Indian sweetpotato weevil of
  various ages with an irradiation dose of 75 Gy.
  Sweetpotato vine borer emergence at 49 d and West
  Indian sweetpotato weevil emergence at 44 d were
  significantly higher than the other age
  treatments (P lt 0.05 by Tukeys test) but not
  different from untreated controls (data not
  shown).
• RESULTS
• Radiotolerance increased with increasing age
  (Fig. 1, above).

B
A
Pupae
Pupae
Larvae
Larvae
Eggs
A
B
C
Table 1. Large-scale confirmatory tests
irradiating three sweetpotato quarantine pests
Stage
Target Measured
Controls Species
Treated Dose (Gy) Doses
(Gy) No. Tested F1 Adults No.
Tested F1 Adults ___________________________
__________________________________________________
___________________________ O. anastomosalis
pupa 150 135-148
30,282 0
6300 10,331 E. postfasciatus
adult 150
130-145 60,000
0 1550
10,543 C. formicarius adult
150 125-140
62,623 0
600 6,398 elegantulus ________
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