Date of Award

2006

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Horticulture

Advisor

M. Susan Erlich

Second Committee Member

Christa R. Schwintzer

Third Committee Member

Constance Stubbs

Abstract

This thesis investigates two potential pest management strategies for Pywbaka yiburni Paykull), a non-native viburnum leaf beetle. A kaolin, wettable powder, SurroundWP, was tested in 2003 and 2004 as a barrier spray during container production of V. dentattlrm plants to determine if it would affect P .M'btlmi larval leaf damage, adult leaf damage and oviposition, and plant growth. The effect of added N (nitrogen) in the form of Osmocote Plus (15-9-12) was also tested. In 2003 three levels of N were used (no added N, 42 g ft3, 84 g ft3) and in 2004 two levels were used (21 g fY3, 84 g ft'3). Percent leaf N was assayed during both growing seasons, leaf damage was visually estimated, and egg cases were counted at the end of the season. Measurements of plant size were taken at the beginning and end of the season. SurroundWP significantly lowered the amount of leaf damage by larvae and adults. It also lowered the number of egg cases except in unamended plants in 2003, which had few egg cases whether they were sprayed or not. SurroundWP did not affect plant growth. In 2003 N use increased significantly the amount of leaf damage by adults and the number of egg cases when compared to no added N, but increasing the amount of added N further (from 42 g ft3 to 84 g ft-3) did not significantly increase leaf damage. Egg cases did not increase except on unsprayed plants. Nitrogen addition increased plant growth significantly when compared to no added N, but increasing the N level from 42 g fi3 to 84 g ft-3 did not increase growth except in sprayed plants. Increases in the leaf N content of the plants with added N paralleled the increases in leaf damage and egg cases. In 2004, increasing the amount of N from 21 g ft" to 84 g ft-3 had no effect on leaf damage, but significantly increased egg cases and plant growth on both unsprayed and sprayed plants. An increase in leaf N content with additional N amendment paralleled the increase in egg cases and plant growth. These results suggest that commercial growers of susceptible Vibtlmtlm species in areas where P. viburni is found could benefit from the use of SurroundWP barrier spray if N amendment is kept to a minimum. These measures by themselves or in conjunction with other IPM tools could minimize the economic effects of leaf beetle damage to container grown viburnum and help slow the spread of the beetle with infested nursery stock.

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