Biocontrol insect abundance on leafy spurge stems, Cache Valley, Utah. - By Eric Bingham

Leafy Spurge Perennial plant whose stems produce 140 seeds which remain viable for 8 years. Rhizomatous roots can reach 18 feet deep and spread 15 feet per year. Latex sap is an irritant. Reduces rangeland by 50-75%. Causes more than 120 million dollars of reduced business to the midwest each year.

Leafy spurge biocontrol Leafy spurge biocontrol includes: – Apthona flava – Apthona nigriscutis – Apthona lacertosa – Oberea erythrocephala

Cache Valley leafy spurge Biocontrol was first released here in the early 1990s This meadow has been periodically monitored ever since then.

My research questions Are biocontrol insects more abundant on flowering or nonflowering stems? Are biocontrol insects more abundant on the hillside or on the meadow?

Methods Weekly monitoring of 400 randomly selected spurge stems: – 100 meadow flowering plants – 100 meadow nonflowering plants – 100 hillside flowering plants – 100 hillside nonflowering plants Measured: – Plant height – Inflorescence diameter – Type of insects present – Type of insect damage (if present) – Presence or absence of seeds

Results – leafy spurge Nonflowering stems were more common than flowering stems Nonflowering

Results – leafy spurge The spurge was more dense on the meadow than the hillside Flowering stems were taller than nonflowering stems Meadow plants were taller than hillside plants Meadow plants had larger inflorescence diameter than hillside plants MeadowHillside CharacterMeanSDMeanSD Stem Density (stems per square meter), July Height of flowering stems (cm), week of June Height of nonflowering stems (cm), week of June Inflorescence diameter (cm) on flowering stems

Results - Oberea The Oberea were more abundant on the flowering stems The Oberea damage was more abundant on the nonflowering stems

Results – A. lacertosa A. lacertosa were most abundant on the meadow nonflowering plants. A lacertosa damage was most abundant on the hillside flowering plants

Characteristic being compared Type of ANOVA FdfP Stem density between meadow and hillside – transformed as natural log [stem density] way6.951, Plant height2-way Effect of habitat (meadow vs. hillside) , Effect of condition (flowering vs. nonflowering) , Interaction of habitat and condition 1.431, Inflorescence diameter on flowering stems between meadow and hillside 1-way18.161, Oberea per stem2-way Effect of habitat (meadow vs. hillside) 0.261, Effect of condition (flowering vs. nonflowering) 9.291, Interaction of habitat and condition 1.611, A. lacertosa per stem2-way Effect of habitat (meadow vs. hillside) 0.041, Effect of condition (flowering vs. nonflowering) 0.291, Interaction of habitat and condition 1.011,760.32

Discussion question Why were the Oberea insects significantly more abundant on the flowering stems, but their damage was so much more abundant on the nonflowering stems?

Conclusions Negligible difference in biocontrol insects between the meadow and hillside Negligible difference for A. lacertosa on flowering versus nonflowering stems Oberea occur more abundantly on flowering than nonflowering stems Oberea damage occurs more abundantly on nonflowering than on flowering stems Knowing occurance and damage trends can influence biocontrol protocols

Acknowledgments 1- Ted Evans 2- MSSST program and Holly Godsey 3- Committee members: Dave Chapman, Louisa Stark, Barb Nash 4- Emma and Amber Bingham