MN Fruit & Vegetable IPM News - Vol. 1, No. 1

The tarnished plant bug (TPB) is an early-season pest of June-bearing strawberries. TPB damage strawberries by feeding on the flower buds, open blossoms, and developing green berries. Although TPB nymphs are often blamed for damaging the fruit, I have found that adult TPB are responsible for a majority of the damage. In 2001 and 2002, I caged strawberry plants (‘Mira’) and placed TPB adults in the cages at specific growth stages (vegetative, green bud, white bud, first blossom, peak blossom, green berry, and ripe berry). The results of these experiments indicated that most of the feeding damage occurred during the green and white bud stages (Table 1). For ‘Mira’ strawberry this is at approximately 400 DD, using a lower threshold of 32ºF for strawberry growth. At green and white bud stages, TPB adults are present, whereas nymphs are not. Through multiple years of sampling, I have found that TPB adults are present during the early growth stages of strawberry (vegetative, green bud, and white bud; Fig. 1), and TPB nymphs do not appear until late into blossom stage. Therefore, more emphasis should be given to early-season monitoring of adult TPB.

Table 1. Proportion of marketable berries harvested from caged strawberries infested at selected growth stages with adult TPB; 2001-2002
	2001	2002
Stage Infested	Marketable Berries (%)	Marketable Berries (%)
Vegetative	---	88.0±2.0bc
Green Bud	65.0±9.0c	88.0±2.0bc
White Bud	---	80.0±2.0d
First Blossom	85.0±2.0bc	93.0±2.0abc
Peak Blossom	95.0±2.0a	---
Green Berry	93.0±2.0ab	93.0±2.0ab
Ripe Berry	84.0±5.0ab	---
Check	95.0±2.0a	95.0±1.0a
P	0.001	0.0002

To validate my previous research, this year I am monitoring early-season TPB activity at both White Bear Lake and Mabel, MN. In White Bear Lake I placed six yellow sticky traps at the edge of a 4-ac field of ‘Jewel’, and six at the edge of a 4-ac field of ‘Annapolis’ on March 30. In Mabel, I placed 12 yellow sticky traps at the edge of a 6-ac field made up of ‘Mira’, ‘Brunswick’, and ‘Northeaster’, on March 29. Sticky traps are changed weekly, and counts of TPB are taken. The summary of this seasons’ sampling is shown in Fig. 2. On May 4, strawberries at Mabel were at the green bud stage, whereas strawberries at White Bear Lake were just showing buds at the crown level. The differences between the two sampling locations for TPB populations should provide an interesting comparison of TPB activity and its relation to unmarketable fruit.

Conclusions so far indicate the following: 1) monitoring at the onset of vegetative growth, using yellow sticky traps, will be an efficient method for detecting early TPB adult activity, and 2) management of adult TPB during the early strawberry growth stages (green and white bud) is recommended for maximizing marketable yield.

If you would like more information about my research, or information on where to buy yellow sticky traps, please contact me at woldx018@umn.edu, or, 612-624-9292.

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ACKNOWLEDGEMENTS

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@umn.edu
Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Division,jeanne.ciborowski@state.mn.us
Suzanne Wold-Burkness, Department of Entomology, University of Minnesota, woldx018@umn.edu

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Tuesday to Jeanne Ciborowski, 651-297-3217, jeanne.ciborowski@state.mn.us , MDA, 90 W. Plato Blvd., St. Paul, MN 55107-2094. You can access the Newsletter at the U of MN web site in htm. format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf. format at: www.mda.state.mn.us/biocon/fruitreports/default.htm

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association and the United States Department of Agriculture – Risk Management Agency (RMA) and the RMA Community Outreach and Assistance Partnership Program. These institutions are equal opportunity providers.

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Last Revised May 7, 2004.
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