|Mcpherson, R - UNIVERSITY OF GEORGIA|
|Culbreath, A - UNIVERSITY OF GEORGIA|
Submitted to: Tobacco Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 1994
Publication Date: N/A
Interpretive Summary: Twelve cultivars of flue-cured and burley tobacco were transplanted on early and late dates in 1992 and 1993, and were evaluated weekly for thrips, aphids, and tomato spotted wilt virus infection. Planting date was inconsistent for aphids due to a cool spring in 1992 as compared to 1993. Cultivars I-514, TI 1396, Polalta, NC 2326, and KY 14 supported large populations of aphids. Numbers of thrips were higher in all early planted tobacco during both years, and higher in cultivars K-326, TI 1396, and NC 2326 than other cultivars. Large thrips population densities did not correlate with high incidence of tomato spotted wilt. Cultivars TI 1406, Tenn 86, and KY 14 with high incidence of spotted wilt infections had low numbers of thrips and cultivars TI 1223, TI 1396, K-326, and Polalta had low numbers of thrips and cultivars TI 1223, TI 1396, and Polalta had low incidence of spotted wilt infections but large thrips populations. There was no effect of planting date on incidence of tomato spotted wilt virus. Cultivars I-35, TI 1223, TI 1396, TI 1586, and Polalta have resistance to spotted wilt virus under large thrips population densities indicating the potential for breeding resistant cultivars.
Technical Abstract: Field experiments were conducted in Georgia during 1992 and 1993 to evaluate the impact of planting date and tobacco cultivars on the abundance of thrips, primarily Frankliniella fusca (Hinds), and tobacco aphids, Myzus nicotianae Blackman, and the incidence of tomato spotted wilt virus (TSWV), a disease vectored by thrips. Twelve cultivars of flue-cured and burley tobacco, Nicotiana tabacum L., were planted in mid-April and early May and monitored every 1-2 weeks for the presence of thrips and aphids and the incidence of TSWV. Planting date had inconsistent effects on aphid population densities. More aphids were present in the later-planted tobacco in 1992 and in the early-planted tobacco in 1993. Cooler weather patterns in 1992 delayed the aphid population increases until later in the season. Significant cultivar differences were observed, with I-514, TI 1396, Polalta, NC 2326, and Kentucky 14 having higher aphid population densities. Thrips populations were largest in the early-planted tobacco both seasons. K 326, TI 1396 and NC 2326 had larger thrips populations than the other entries. However, thrips population densities were not correlated with TSWV infection. The entries with higher TSWV infection rates, i.e., TI 1406, Tenn 86, and Kentucky 14, had relatively low thrips populations. Conversely, the more resistant lines, i.e., TI 1223, TI 1396, K 362, and Polalta, had low levels of TSWV infection although thrips populations were relatively high. Planting date did not influence the rate of TSWV infections among the entries. Each cultivar had a virus infection rate similar for both planting dates. There appears to be host plant material resistant to TSWV infection in the presence of known insect vectors.