Broccoli yield response to cabbage looper and varietal preferences of lepidopterous pests of broccoli

Respondents of the 1986 Broccoli Growers Survey grew an average of 6.2 acres of broccoli in Fall 1986; popular varieties were Green Valiant (87.5% of respondents), Packman and Emperor (62.5%). Less than 5% of tobacco land was converted to broccoli production by 62.5% of the growers. Before heading, 2.4 insecticidal sprays were applied for worms at $20.51/acre. During heading, 2.4 insecticidal sprays were applied for worms at $19.40/acre. Under normal growing conditions, a nine-day mean of 8.4 and a 15-day mean of 12.1 cabbage looper larvae/plant did not significantly reduce yield in the Spring and Fall respectively. However, means of 7.4 and 11.1 cabbage looper larvae/plant reduced yield (head weight) under drought conditions. Harvest date was not affected by the above cabbage looper levels. In Fall 1986, a reduction in yield occurred when plants had 50% or more defoliation and harvest date was significantly delayed at 100% defoliation. In the drought stressed Spring 1987 planting, a stimulation in yield occurred at 25% defoliation and 75% defoliation was needed to significantly reduce yield, but there was no difference in harvest date. The imported cabbageworm was the most abundant pest of broccoli in Montgomery Co., VA. Based on counts of all immature stages of the insects for three seasons, Packman and Southern Comet varieties were less preferred compared to Green Defender. Laboratory studies indicated that imported cabbageworm larvae developed faster to the fifth instar on Packman broccoli than those reared on Green Defender, Southern Comet or Emperor. Difference in amount consumed between varieties was not detected. Pupae reared on Southern Comet weighed significantly more than those reared on Packman.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Entomology

Department dc:contributor.department

Entomology

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1988

Author dc:creator

• Vail, Karen M.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10919/109907

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/109907