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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Transgenic Cotton on Cabbage Looper, Tobacco Budworm and Beet Armyworm (Lepidoptera: Noctuidae) Larval Mortality and Development and Foliage Consumption in the Laboratory.

Authors
item Henneberry, Thomas
item Jech, Lynn
item De La Torre, Theresa

Submitted to: Southwest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2001
Publication Date: April 1, 2002

Interpretive Summary: Transgenic cotton has had a major impact on pest management in Arizona and southern California. The key pest, pink bollworm, is highly susceptible and over 6 years of commercial use for infestations has averaged < 1.0%. Less is known about other lepidopterous pests since they occur sporadically. We developed laboratory assays to estimate the potential of Bt for control of tobacco budworm, cabbage looper, and beet armyworm that are common cotton pests. Tobacco budworm larvae were highly susceptible to feeding on Bt leaves or flower buds with 100% and 96% mortality occurring within 4 days, respectively. Average mortality for cabbage looper was 95% and 57% for beet armyworm after 8 days feeding on Bt leaves and 47% and 37% mortality following feeding on flower buds for four days. Larval growth of cabbage looper and beet armyworm feeding on Bt leaves was lower compared with those feeding on non-Bt cotton leaves and larvae consumed significantly less Bt leaf area per feeding day compared with DPL 5415. The Bt technology then is as effective for tobacco budworm control as it is for pink bollworm control. Reduced feeding of beet armyworm and cabbage looper larvae feeding on Bt cotton also suggests high suppression of these species in Bt cotton cultures. However, a leaf-age effect showed that both species also consumed less leaf tissue and weighed less on old (7th to 9th node) vs. new (15th to 17th node) leaves of both DPL 5415 and Bt cottons. Leaf-age effects on larval mortality and pupation were variable.

Technical Abstract: Tobacco budworm larvae, Heliothis virescens (F.), were highly susceptible to feeding on Bt leaves or flower buds with 100% and 96% mortality occurring within 4 days, respectively, compared to an average mortality of 95% for cabbage looper, Trichoplusia ni (Hubner), and 57% for beet armyworm, Spodoptera exigua (Hubner), after 8 days on Bt leaves and 47% and d37% mortality on flower buds for four days. Larval weights, used as a measure of growth, of cabbage looper and beet armyworm after 7, 10, or 14 days of feeding on Bt leaves were lower compared with those feeding on non- Bt cotton leaves. Beet armyworm, cabbage looper and tobacco budworm larvae consumed significantly less Bt leaf area per feeding day compared with DPL 5415. However, a leaf-age effect showed that both species also consumed less leaf tissue and weighed less on old (7th to 9th node) vs. new (15th to 17th node) leaves of both DPL 5415 and Bt cottons. Leaf-age effects on larval mortality and pupation were variable.

Last Modified: 8/27/2014
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