Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Potato tuberworm (PTW), Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is one of the most important pests of potatoes in tropic and subtropic regions. We examined the role of tuber age, periderm (the outer cork layer of tubers) as well as internal tuber factors in the expression of resistance to PTW in a resistant hybrid potato clone, Q174-2(S. tuberosum x S. berthaultii Hawkes, compared to a susceptible commercial potato cultivar, cv. Allegany. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Larval production increased with tuber age on both susceptible and resistant potato clones, suggesting that bud sprouts may enhance fitness by providing food and shelter for first instars prior to tuber entry. Removal of tuber periderm led to a significant increase in larval survival on Allegany and Q174-2, although proportional survival on Allegany and Q174-2 was similar to that on intact tubers, suggesting the involvement of internal rather than external periderm factors in tuber resistance of Q174-2. Weights of larvae reared on Q174-2 were consistently less than those of larvae reared on susceptible potato tubers in both intact and peeled tuber assays. Although the expression of periderm-mediated tuber resistance declines with tuber age, such resistance could significantly reduce preharvest field infestations by PTW and constitute an important component of sustainable PTW management, particularly for fresh market crops and for those potato crops stored for several months or less in the absence of refrigeration.
Publications
- Dogramaci, M. & W. M. Tingey. 2009. Host resistance and influence of tuber surface on larval performance of potato tuberworm (Lepidoptera: Gelechiidae). J. Pest Science. 82: 109-114.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Potato tuberworm (PTW), Phthorimaea operculella Zeller, has become a serious threat to potato production in the Columbia Basin region of Oregon and Washington and in 2005 was found in Idaho. Despite intensive insecticide application, severe defoliation has occurred in recent years indicating insensitivity of potato tuberworms (PTW) to insecticides. We examined dose responses of potato tuberworms from a Columbia Basin field population (CBFP) and a laboratory colony from Colorado (COLC) to three commonly used field crop insecticides (esfenvalerate, methamidophos and fipronil. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Despite being reared in isolation for >30 years, the COLC was resistant to field-labeled rates of all three insecticides used in this study. The CBFP was also resistant to esfenvalerate and fipronil at field rates but was relatively susceptible (40% mortality) to methamidophos. At 10x field rate of fipronil, COLC was very susceptible (>90% mortality) but CBFP was not significantly affected. CBFP was also more resistant to esfenvalerate than COLC. None of the COLC survived a 500x field rate of esfenvalerate; the same dose killed only 10% of the CBFP. This study provides baseline information about PTW insecticide resistance indicating that the Columbia Basin field population was highly resistant to esfenvalerate and fipronil. However, further studies are needed to detail the resistance mechanism of PTW against other commonly used insecticides used to manage PTW in solanaceous crops.
Publications
- Dogramaci, M. & W. M. Tingey. 2008. Comparison of insecticide resistance in a North American field population and a laboratory colony of potato tuberworm (Lepidoptera: Gelechiidae). J. Pest Science. DOI 10.1007/s10340-007-0178-5. 81: 17-22.
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