Disease Control Prevent The Spread Of Disease In ...Recycling irrigation water and recirculating...
2
68 Greenhouse Grower March 2016 Production Disease Control Prevent The Spread Of Disease In Irrigation Water Water-mold pathogens cause significant crop losses and reduce floriculture crop quality. Take measures in your greenhouse to prevent the spread of diseases like Phytophthora and Pythium. by MARY HAUSBECK and WEI ZHANG P HYTOPHTHORA and Pythium are water molds that are difficult to control, especially under warm, wet conditions. Thick-walled oospores survive be- tween crops on plant containers, benches, floors, and in potting media or soil. Spores include lemon-shaped sporangia, thick-walled chlamydospores, and swimming zoospores. The lemon- shaped spores called sporangia form on the surface of roots, crowns, and other plant tissues. Sporangia may be dislodged from infected plants by irrigation water, drain- age water, or windblown rain. In water, sporangia release many swimming spores called zoospores, which spread the disease. Pythium And Phytophthora: Water Mold Cousins Pythium nibbles the feeding roots of plants, resulting in stunt- ed growth and death. It can be introduced to the greenhouse via plant plugs or other prefinished plant material, or it can hiber- nate on dirty plant containers, benches, and walkways. Although Pythium can be a problem on many annuals and perennials, it seems to favor geraniums and poinsettias. Sanitary conditions that favor good plant growth and minimize stress make the plant less vulnerable to attack by a root rot. Two types of Phytophthora (Phytophthora nicotianae and P. drechsleri) are usually found in floriculture crops and can cause root, crown, and foliar blights. Symptoms include brown-black cankers at the soil line and diseased roots. P. nicotianae can infect snapdragon, fuchsia, verbena, bacopa, vinca, African violet, and dusty miller, while. P. drechsleri may infect poinsettias. Recirculating Irrigation Water Can Spread Pythium and Phytophthora Phytophthora spread occurs from zoospores that move through water. Disease occurrence within nurseries and green- houses often follows drainage patterns, but windblown rain may allow Phytophthora to spread across a nursery. The cycle of plant infection and zoospore production occurs many times within a single growing season. Thus, low levels of infection early in the season may result in a rapid epidemic, if the disease is not imme- diately controlled. Many physical and chemical treatment options have been proposed to disinfect contaminated irrigation, including treat- ment with substances (chlorine, ozone, surfactants, antimicro- bial compounds, biological control agents, ultraviolet light, and sedimentation), and physical removal (filtration). Treatment Methods For Contaminated Irrigation Water Recycling irrigation water and recirculating nutrient solutions are beneficial, but can also increase the spread of waterborne pathogens. There are several methods currently available for disinfesting contaminated irrigation water, including the use of antimicrobial compounds such as copper and hydrogen peroxide. Commercial algaecides contain copper sulfate, chelated cop- per, or sodium carbonate peroxyhydrate as their active ingredi- ents. Previous studies show that increasing copper ion concen- trations in nutrient solutions reduces disease caused by some Phytophthora spp. Without adequate treatment options for irrigation water, water mold pathogens can continue to cause significant crop losses and reduce floriculture crop quality. One effective strategy to prevent crop losses is to limit pathogen numbers in critical transmission routes or points within a production system, such as in irriga- tion water. Sand filtration has been proposed as an inexpensive treatment to remove the water molds, including Pythium and Phytophthora, from contaminated water, but variable results have been observed. Spores of water molds are negatively charged, and interactions between spores and the sand filter Treatment Zoospores per ml of water 11/7 11/19 11/24 12/31 Inoculated control 1.4 2.3 0.0 0.04 Uninoculated control 0.0 0.0 0.0 0.0 Carbon 0.0 0.5 0.02 0.0 Sand 0.1 0.1 0.0 0.0 Diseased plant 0.1 0.02 0.0 0.02 Terrazole 35WP 0.0 0.1 0.02 0.0 Table 1. Average Pythium zoospores per ml of water sampled from irrigation holding tanks.
Transcript of Disease Control Prevent The Spread Of Disease In ...Recycling irrigation water and recirculating...
68
Greenhouse Grower March 2016
ProductionDisease Control
Prevent The Spread Of Disease In Irrigation WaterWater-mold pathogens cause significant crop losses and reduce floriculture crop
quality. Take measures in your greenhouse to prevent the spread of diseases like
Phytophthora and Pythium.
by MARY HAUSBECK and WEI ZHANG
PHYTOPHTHORA and Pythium are water molds that are difficult to control, especially under warm, wet conditions. Thick-walled oospores survive be-tween crops on plant containers, benches, floors,
and in potting media or soil. Spores include lemon-shaped sporangia, thick-walled
chlamydospores, and swimming zoospores. The lemon-shaped spores called sporangia form on the surface of roots, crowns, and other plant tissues. Sporangia may be dislodged from infected plants by irrigation water, drain-age water, or windblown rain. In water, sporangia release many swimming spores called zoospores, which spread the disease.
Pythium And Phytophthora: Water Mold CousinsPythium nibbles the feeding roots of plants, resulting in stunt-
ed growth and death. It can be introduced to the greenhouse via plant plugs or other prefinished plant material, or it can hiber-nate on dirty plant containers, benches, and walkways.
Although Pythium can be a problem on many annuals and perennials, it seems to favor geraniums and poinsettias. Sanitary conditions that favor good plant growth and minimize stress make the plant less vulnerable to attack by a root rot.
Two types of Phytophthora (Phytophthora nicotianae and P. drechsleri) are usually found in floriculture crops and can cause root, crown, and foliar blights. Symptoms include brown-black cankers at the soil line and diseased roots. P. nicotianae can infect snapdragon, fuchsia, verbena, bacopa, vinca, African violet, and dusty miller, while. P. drechsleri may infect poinsettias.
Recirculating Irrigation Water Can Spread Pythium and Phytophthora
Phytophthora spread occurs from zoospores that move through water. Disease occurrence within nurseries and green-houses often follows drainage patterns, but windblown rain may allow Phytophthora to spread across a nursery. The cycle of plant infection and zoospore production occurs many times within a single growing season. Thus, low levels of infection early in the season may result in a rapid epidemic, if the disease is not imme-
diately controlled. Many physical and chemical treatment options have been
proposed to disinfect contaminated irrigation, including treat-ment with substances (chlorine, ozone, surfactants, antimicro-bial compounds, biological control agents, ultraviolet light, and sedimentation), and physical removal (filtration).
Treatment Methods For Contaminated Irrigation Water Recycling irrigation water and recirculating nutrient solutions
are beneficial, but can also increase the spread of waterborne pathogens. There are several methods currently available for disinfesting contaminated irrigation water, including the use of antimicrobial compounds such as copper and hydrogen peroxide.
Commercial algaecides contain copper sulfate, chelated cop-per, or sodium carbonate peroxyhydrate as their active ingredi-ents. Previous studies show that increasing copper ion concen-trations in nutrient solutions reduces disease caused by some Phytophthora spp.
Without adequate treatment options for irrigation water, water mold pathogens can continue to cause significant crop losses and reduce floriculture crop quality. One effective strategy to prevent crop losses is to limit pathogen numbers in critical transmission routes or points within a production system, such as in irriga-tion water. Sand filtration has been proposed as an inexpensive treatment to remove the water molds, including Pythium and Phytophthora, from contaminated water, but variable results have been observed. Spores of water molds are negatively charged, and interactions between spores and the sand filter
TreatmentZoospores per ml of water
11/7 11/19 11/24 12/31
Inoculated control 1.4 2.3 0.0 0.04
Uninoculated control 0.0 0.0 0.0 0.0
Carbon 0.0 0.5 0.02 0.0
Sand 0.1 0.1 0.0 0.0
Diseased plant 0.1 0.02 0.0 0.02
Terrazole 35WP 0.0 0.1 0.02 0.0
Table 1. Average Pythium zoospores per ml of water sampled from irrigation holding tanks.
70
Greenhouse Grower March 2016
Production Disease Control
surface are influenced by the physical and chemical properties of the water and sand.
Some greenhouse irrigation systems al-ready have a filtration unit. Using a screen or paper filters that remove large-sized soil particles and plant debris to keep the micro-emitters of irrigation lines clear. These installed filtration units are not likely to be effective to remove water mold spores, which are much smaller in size.
Filtration Research At Michigan State University
A preliminary greenhouse filtration experiment tested sand filtration media containing positively charged, nano-sized iron-oxide particles embedded on the sur-face. Results showed that Phytophthora zoospores were readily attached to the syn-thesized, nano-sized, iron-oxide surface coating of filter sand. The removal of motile zoospores was significantly less than that of the encysted zoospores. The results sug-gest that through controlling parameters of zoospores (e.g., encystment), solution chemistry (e.g., ion type), or filter media type, zoospore removal can be optimized.
Novel filter media are being tested in small-scale filter units in a greenhouse environment with spores of Pythium aphanidermatum. A trial tested poinsettias that were (A) untreated uninoculated or (B) untreated inoculated, and compared them with inoculated plants irrigated with systems containing (C) a sand filter or (D) an activated carbon filter, and inoculated plants irrigated with (E) an unfiltered system with the labeled rate of Terrazole 35WP added to the water or (F) an unfil-tered system that had diseased plants.
Zoospores were added to the pre-filter tanks and were passed through the fil-ters and irrigated onto the ebb-and-flow bench tops to initiate the experiment. Plants were irrigated twice daily for 15 minutes to increase disease pressure. Water was sampled from the holding tanks during the course of the study to determine the concentration of zoospores in solution (Table 1, page 68).
The trial concluded after two and a half months. The inoculated control displayed severe root rot and stunting (Figure 1). The sand filter, Terrazole treatment, carbon filter, and diseased plant treatment all had
significantly higher foliar fresh weight and plant height than the inoculated control treatment. These results suggest filtration may be useful in a greenhouse setting. GG
Dr. Mary Hausbeck ([email protected]) is a Professor and Extension Specialist in the Depart-ment of Plant, Soil and Microbial Sciences at Michigan State University (MSU) in East Lansing, MI. Dr. Wei Zhang ([email protected]) is an Assistant Professor in the Plant and Soil Sciences department at MSU. This research was funded in part by the American Floral Endowment and a Cooperative Agreement #58-8062-5-036 with the Agricultural Research Service under the Floriculture and Nursery Research Initiative.
A. Uninoculated Untreated
D. Carbon Filter
C. Sand Filter
B. Untreated Inoculated
F. Diseased Plant
E. Terrazole 35 WP
Figure 1. Rot on roots of (A) uninoculat-ed untreated versus poinsettias inoculated with Pythium and (B) untreated, or irrigat-ed with water treated with (C) a sand filter, (D) an activated carbon filter, (E) Terrazole 35WP/unfiltered, or (F) with diseased plants added to the system/unfiltered.
Put these Plant
managersto work in your
oPeration.
Excellence in PGR Technology
www.fine-americas.com
Always read and follow label directions. Abide,® Citadel,® Collate,® Concise,® Concise,® Configure,® Florgib,® Fresco® and Piccolo® are trademarks of Fine Agrochemicals, Ltd. Dazide® is a registered trademark of Find Holdings, Ltd., ARest,® Cycocel,,® Florel,® Sumagic,,® B-NINE,,® ProGibb,® Fascination® and Bonzi® are registered trademarks of their respective manufacturers. © 2014 Fine Americas, Inc.
Same active ingredient as ARest®
Same active ingredient as ProGibb®
Same active ingredient as Fascination®
Same active ingredient as Bonzi®
The only 4% paclobutrazol formulation
Same active ingredient as Cycocel®
Same active ingredient as Sumagic®
The only 2% 6-BA PGR for ornamentals
Same active ingredient as B-NINE®
Same active ingredient as Florel,® but more concentrated
®
®
®
®
®
