Dr. Chris Marble (UF IFAS, Apopka) presents nursery weed management research — hand weeding every two weeks cut labor costs 40–65%, rice hulls at one inch killed 95%+ of emerged seedlings, and early LEAP project data showed a liquid boom covering 17 acres with one employee vs. a granular crew of three covering 1.3 acres.
Marble covers non-chemical control strategies, rice hull mulch performance (fertilizer placement effects, outdoor degradation rates, suppression mechanisms), substrate stratification that eliminated liverwort for 20+ weeks, herbicide rotation principles using the 2017 Southeast Pest Management Guide, two new bare-ground products (StrataCor and SureGuard Extra), and USDA-funded equipment efficiency comparisons including drone application. Paul Bartley joins for Q&A on mulch weed control mechanisms.
Speaker: Dr. Chris Marble, Associate Professor of Horticulture, University of Florida IFAS, Mid-Florida Research and Education Center, Apopka, FL
Moderator: Dr. Shimat Joseph, UGA
Series: Getting the Best of Pests (GTBOP) — Green & Commercial
Webinar Date: March 12, 2026
Duration: 45:13
CEU Categories: 10 (Private Applicator), 21 (Plant Agriculture), 24 (Ornamental and Turf), 27 (Right-of-Way), 32 (Regulatory)
0:00 Introduction — Dr. Chris Marble
1:00 Non-Chemical Weed Control Options in Nurseries
2:00 Hand Weeding Frequency Study Design
4:00 Cost Savings from More Frequent Weeding
7:00 Cleanup Protocols for Heavily Infested Blocks
9:30 Training Crews — Which Weeds to Pull, Which to Leave
10:30 Early Post-Emergence Activity of Pre-Emergent Herbicides
12:50 Rice Hull Mulch — Properties and Grower Questions
15:30 Fertilizer Placement Effects with Rice Hulls
18:00 Rice Hulls on Already-Emerged Weed Seedlings
20:00 Rice Hull Performance Outdoors — Seed Placement Study
22:00 Moisture Deprivation as the Weed Control Mechanism
23:00 Rice Hull Degradation Rates and Depth Recommendations
24:20 Substrate Stratification for Liverwort and Bittercress
27:20 Developing a Herbicide Rotation Program
30:00 New Bare-Ground Herbicides — StrataCor and SureGuard Extra
31:00 LEAP Project — Herbicide Application Equipment Efficiency
34:00 Liquid Application Volumes and Canopy Penetration
36:00 Granular vs. Liquid Equipment Economics
37:30 Drone-Based Granular Application
39:00 UF Weed Management Training Course
40:00 Q&A — Substrate Stratification and Pot Temperature
43:00 Q&A — Rice Hulls vs. Wood/Bark Mulch Mechanisms
Q: How much can a nursery save by weeding more often?
Weeding every two weeks instead of every eight reduced costs by 40–60% across multiple sites (65% at the Florida site). Workers pulled only large weeds likely to seed — cotyledon-stage seedlings were left for the next pass. Over 24 weeks, seed bank pressure dropped steadily in frequent-weeding blocks.
Q: Can rice hulls be applied over pots with small weeds already emerging?
At one inch of rice hulls, survivability of cotyledon-stage eclipta and Phyllanthus dropped by 95% or more. Bittercress and oxalis at the same depth were controlled at nearly 100%. Weed-free pots at application are ideal, but one inch of hulls kills most small seedlings present.
Q: How long do rice hulls last outdoors?
About 40% of the applied layer remained after 12 months under Florida conditions. Rice hulls matched standard pre-emergent rotations for the first six months; after that, herbicide treatments outperformed as the hull layer degraded. Marble recommended rice hulls for crops finishing in six to eight months.
Q: What is substrate stratification, and does it work on liverwort?
Coarse bark on top with fertilizer placed below. Liverwort needs both moisture and nitrogen — stratified containers eliminated liverwort for over 20 weeks and reduced bittercress by 40–60%.
Q: How does herbicide application equipment compare in efficiency?
LEAP project data from four nurseries: granular application used three employees for five hours to cover 1.3 acres at $5,500 chemical cost. A liquid boom covered 17 acres with one employee in six hours at about half the chemical cost. A drone applied granular herbicide over a half acre in three minutes.
References:
- “Frequent Hand Weeding Saves Money” — Barker and Neal, 2016
- 2017 Southeast Pest Management Guide
- UF IFAS Weed Management Training Course (four weeks, English and Spanish)
- LEAP Project — contact Dr. Marble for collaborator opportunities
Presented by the UGA Center for Urban Agriculture
Getting the Best of Pests (GTBOP) Webinar Series
ugaextension weedcontrol nurseryproduction ricehulls pestmanagement
Adapted from GTBOP Archive Summary for YouTube distribution
Source: GTBOP_Archive_Summary_2026-03-12_NurseryWeedControl.md