Cogongrass, Biodiversity and Pine Decline

Nancy J. Loewenstein, Stephen F. Enloe, Sallie Martin and Ben Brunson Auburn University OBJECTIVES

• Impacts of cogongrass infestations on insect communities of southeastern pine forests • Influence of cogongrass management strategies on insect diversity and abundance • Influence of cogongrass on susceptibility of pines to pine decline

COGONGRASS, ITS MANAGEMENT AND INSECT BIODIVERSITY (STUDY 1)

• Study sites: – 10-year-old planted longleaf pine forests – one in Mobile county, one in Baldwin county, AL – Heavily infested with cogongrass (90-100% cover) – Sandy loam soils

• Treatments: – Prescribed fire – Glyphosate – Seeding with mix of native – Control

• Design: – Split plot with CRD – 10 X 10 m plots – 5 replicates per treatment – Non-cogongrass control

PRESCRIBED FIRE TREATMENT

• Block containing half of the plots was burned in March of 2010 • Good weather conditions to minimize fire severity

Still got a bit hot! NJL NJL burned unburned GLYPHOSATE TREATMENTS

• April, 2010 - 6 weeks post-burn, pre-flowering , regrowth 12-18” • 2.5% v/v

• October, 2010 – regrowth 18- 36” • 4.0% v/v

• both treatments applied with a single nozzle backpack sprayer at 55 GPA and 20 PSI SEEDING WITH NATIVE PLANTS

• Plots were lightly disked • Broadcast sown • April 2010 • Feb 2011 2010 SPECIES LIST

common sunflower Helianthus annuus 35% switchgrass 'Carthage' Panicum virgatum 32% purpletop tridens Tridens flavus 10% partridge pea Chamaecrista fasciculata 15% dixie ticktrefoil Desmodium tortuosum 2% largeflower tickseed Coreopsis grandiflora 2% grey headed coneflower Ratibida pinnata 2% blackeyed Susan Rudbeckia hirta 2%

25 PLS per acre …. $15.81 per lb .... $395 per acre

Seed source: Ernst Conservation Seeds OCTOBER 2010 • Coverage of native plants was not high •Cogongrass recovery was fairly strong

• Prompted retreating with glyphosate … reseeding in 2011

1=1-2.5%, 2=2.5-10%, 3=10-25%, 4=25-50%, 5=50-75%, 6=75-100% B=burned, G=glyphosate, S=seeded, U=unburned 2011 SPECIES LIST

Virginia wild rye Elymus virginicus 19% Indian grass Sorghastrum nutans 19% purpletop tridens Tridens flavus 12% broomsedge Andropogon virginicus 10% partridge pea Chamaecrista fasciculata 30% lance-leaved coreopsis Coreopsis lanceolata 2% perplexed ticktrefoil Desmodium perplexum 2% greyheaded coneflower Ratibida pinnata 2% blackeyed Susan Rudbeckia hirta 2% white wingstem Verbesina virginica 2% spurred butterfly pea Centrosema virginianum 1%

9 PLS per acre …. $22.9 per pound …. $206 per acre

Seed source: Roundstone Native Seed 2011 SPECIES RICHNESS 2011 COGONGRASS COVER 40 6 July 5

30 Class 4 20 Sown 3 July Natural October 2

Richness Species 10 1 Cogongrass Cover Cogongrass Cover 0 0 B BG BS BGS U UG US UGS B BG BS BGS U UG US UGS 40 October • Seeding increased diversity only when combined 30 with glyphosate treatment • Seeding alone did not reduce cogongrass cover 20 • Seeding may have helped reduce cogongrass cover on the plots that were burned and treated with Richness Species 10 glyphosate

0 B=burned, G=glyphosate, S=seeded, U=unburned B BG BS BGS U UG US UGS 1=1-2.5%, 2=2.5-10%, 3=10-25%, 4=25-50%, 5=50-75%, 6=75-100% INSECT COMMUNITIES

• Generalist predators (e.g., ants, predaceous and spiders) can serve as bioindicators of sustainability of forest management techniques

• Parasitic hymenoptera and hover flies (Syrphidae) respond to vegetation complexity and are useful indicators of landscape- level changes in vegetation

• Hereafter referred to as ‘Natural Enemies’

References: Maeto et al., 2009; Maleque et al. 2009 INSECT SAMPLING

• 5 pitfall traps (15 cm funnel traps) were placed in each plot • collected every 2 weeks between March and Oct of 2010 and 2011 • Sweep sampling conducted on the same schedule

sorting cleaning identifying

Back at the lab … NATURAL ENEMIES CAPTURED BY SWEEP SAMPLING

• No main effect of fire • Some significant treatment and interaction effects (treatments and fire) … a lot of variation Blue=cogongrass, red=glyphosate, yellow=seeded, • Awaiting results from non- purple=glyposate and seeding cogongrass controls

NATURAL ENEMIES CAPTURED BY PITFALL TRAPS

• No significant treatment effects Mostly fire ants

Mostly fire ants ROOT FEEDING BARK BEETLES ( spp.)

50

45

40

35

30

25

20

15 Numberof insects 10

5

0 6/5/2011 7/3/2011 8/7/2011 9/4/2011 5/15/2011 5/22/2011 5/29/2011 6/12/2011 6/19/2011 6/26/2011 7/10/2011 7/17/2011 7/24/2011 7/31/2011 8/14/2011 8/21/2011 8/28/2011 9/11/2011 9/18/2011 9/25/2011 10/2/2011 10/9/2011 10/16/2011 10/23/2011 LOBLOLLY PINE DECLINE

• Increasingly important issue in Southeast • Caused by a complex of abiotic and biotic stressors • Stressed trees attract root-feeding bark beetles and weevils – – Hylastes porculus – – * – Dendroctonus terebrans – Hylobius pales – Pachylobius picivorus

* non-native

FUNGAL ASSOCIATIONS

• The bark beetles vector wood staining fungi associated with pine decline

– Leptographium terebrantis – Leptographium procerum – Leptographium serpens * – Grosmannia huntii * – Ophiostoma spp.

* non-native COGONGRASS AND PINE DECLINE (STUDY 2)

• Does cogongrass increase tree stress? • Does cogongrass impact bark population levels? • Does cogongrass increase susceptibility to pine decline?

• Study site 80 miles northwest of the 1st study • 13-year-old loblolly pine plantation • fertilized in 2006 and 2010 • thinned to 70 BA in 2009 • 10 plots with cogongrass, 10 plots without

INSECT SAMPLING

• Bi-weekly collections from panel and pitfall traps • Bark beetles and weevils identified and counted • 10% of pitfall insects “rolled” on select media to check for vectoring of fungi

PLOT AND TREE DATA • Tree vigor measurements for each plot – DBH – Height – Age – Growth Increment (5 and 10 year) – Basal Area – Crown Ratings – Foliage Sampling – Resin sampling (volume and terpene composition) • Presence of fungi on root samples – Root cores sampled from 2 roots from each of 6 trees per plot – Core is plated on media to test for presence of the 6 fungi listed in previous slide

INSECT COLLECTIONS - TOTAL

HS-Hylastes salebrosus BTB Other IG XF 3% 3% XP 3% HT- Hylastes tenuis 1% HPO 9% 5% HPO- Hylastes porculus GM 2% IG- Ips grandicolis

XCR BTB- Dendroctonus terebrans 9% XF- Xyleborus ferrugineus XP- Xyleborus pubescens XS 5% GM- Gnathotrichus materiarius

HP PP XCR- Xylosandrus crassiusculus 1% 2% XS- Xyleborinus saxesenii HT 5% HS 52% HP- Hylobius pales PP- Pachylobius picivorus Other- several Ambrosia species 68% of observed insects were species of interest POPULATION TRENDS

2000

1800 Hylastes salebrosus

1600

1400

1200

1000

of of insects Cogon 800 # Non-Cogon 600

400

200

0 POPULATION TRENDS

70 Pachylobius picivorous 60

50

40 Cogon 30 # of # of Insects Non-Cogon 20

10

0 FUNGAL ISOLATES DATA

BTB HPO HS HT HP PP Total Total Rolled 26 96 260 107 42 107 638

Total Fungal 7 7 17 7 17 6 61 Isolates

% Insects 27 7 7 7 10 6 10 Infected

BTB – Dendroctonus terebrans, HPO – Hylastes porculus, HS – Hylastes salebrosus, HT – Hylastes tenuis, HP – Hylobius pales, PP – Pachylobius picivorus • More trees from the cogongrass infested sites had fungus in their root systems

But … • Loblolly on cogongrass infested sites did not produce more resin, although resin analysis may reveal differences in resin composition • No outward signs of pine decline at this time … but, the trees are still young

PRELIMINARY CONCLUSIONS

• Ecologically based integrated treatment • Seeding alone had little impact on cogongrass cover • Seeding, when combined with burning and glyphosate treatments, may contribute to control and restoration efforts

• Response of insect communities (‘natural enemies’) to cogongrass and its treatment is as yet unclear

• Several root feeding beetles were found in greater abundance in cogongrass infested pine stands • ~10% were infected with the fungi associated with pine decline • more tree roots had fungal infections in infested plots • no overt signs of pine decline in the stands at this time

Acknowledgements

• Co-PI’s: • Dr. Lori Eckhardt - Forest Entomology and Pathology, AU … (Ben Brunson’s advisor) • Dr. David Held – Entomology and Plant Pathology, AU … (Sallie Martin’s advisor)

• Research Tech: Joe Borden • 2011 Plant Surveys: Gina Todia – Wetland Resources, Environmental Consulting

• Study sites: Tommy Swearingen, Austin Rainwater, The Westervelt Company

• Funding : USDA-CSREES-AFRI Biology of Weedy and Invasive Species Competitive Grant Program