Phytosphere Research

Zoospore collection system for nursery plants

Various methods can be used to detect root-infecting Phytophthora species in plants. We decribe a method for testing leachate from container grown plants in our BMPs for Producing Clean Nursery Stock pages. The most practical methods for monitoring large numbers of plants in a nursery involves capturing irrigation that drains from the bottom of continers during irrigation and baiting that water with a Phytophthora -specific bait such as a green pear. This system allows for testing of relatively large blocks of plants at one time without requiring that the plants be moved from the benches upon which they are situated. Such testing can be done on a spot basis during an inspection, but more importantly, can be run by the nursery on an ongoing basis to monitor plants for infection. Drought tolerant plants growing in the nursery with frequent irigation and low evaporative demand will commonly not show obvious top symptoms even when root rot is extensive.

To run this test, we need two pieces of equipment:

Collection system (universal fit)

This page describes how to make a universal collection system that can be suspended under a variety of greenhouse benches. This is useful if you are running tests in multiple nurseries, which tend to have a wide variety of bench arrangements. As with many universal-fit devices, this collection system can be made to fit many different situations, but is not necessarily going to be the simplest or most efficient design for any given bench. If you are doing repeated tests in your own nursery, it will be simpler to design the collection system for the specific dimensions of your benches. Instead of suspending your custom-made collection system, it may be more convenient to make it free standing or cart-mounted to make it easier to slip under benches to be tested.

Materials needed:

Tools needed:

What to do:

vinyl flashing sheetsVinyl flashing, sowing grommets (inset and right) and placement of crease. Nylon cord with S hook can be tied through the grommet as shown for the four corners that will not overlap with other sheets (the high corners of the upslope sheet and the lowest corners of the downslope sheet).

cords and hooksConfiguration of cords that are not tied to the sheet corners. Note that all S hooks are pinched closed on one end so they will stay attached to the cords.

PVC connectorsConnectors used to join vinyl flashing sheets at seams. Bottom image shows marked cut lines and drill points on PVC molding.

Setting it up:

Attachment of cords to benchLeft - linking of two adjacent sheets using the PVC connector and attachment to bench. Right - attachment of cord from non overlapping corner (upslope) to bench.

attachment to potsCords can be hooked to containers if there are no places to hook on the bench top.

bench attachmentVariation of attachment due to supports in center of bench. Two sheets are linked together on the right side of the vessel, a sinle separate sheet is directed into the vessel from the other side. The vinyl flashing sheets can be used singly or linked together (2 or 3 sheets) to form a larger catchment area.

PVC pipe dam for downslope endSlitted PVC pipe dams are easier to slide onto the edge of the flashing sheet if you start with the end of the pipe at the corner and slide stright down as shown in top image. When installed, edges of pipes should be inside of the rim of the zoospre collection vessel (lower image).

Zoospore collection vessel

To optimize the detection of zoospores, this device takes two facts into account. First, zoospores swim upward, so they will therefore concentrate near the top of a water column. Second, debris that may contain sporangia or oospores tends to either float or settle to the bottom of a water column. A large amount of water will be leached out of the irrigated plants, so the objective of this vessel is to concentrate inoculum where it can be detected by the bait. To accomplish this, excess water drains from the middle portion of the water column rather from the top or bottom.

The other main design consideration is that the container outflow needs to be sized large enough to accomodate the maximum amount of water flowing into the vessel. A 1 inch (2.54 cm) PVC pipe has sufficient flow to handle peak drainage from a set of plants covering about 10.8 sq ft (1.5 sq m) of bench, which can be captured using the collection system above.

Materials needed:

Parts needed for zoospore collection vesselPVC fittings and pipe sections (all 1 inch diameter), pear exlusion device (black ABS), gasket, and 2 gallon beverage container needed to assemble the zoospoire collection vessel. Existing spigot has been removed from the container and a larger hole has already been made.

Tools needed:

What to do:

See this video to see how to construct this vessel. In short:

Top view of empty zoospore collection vesselTop view of the assembled zoospore collection vessel. Note rubber gasket to inside and pear exclusion device (black ABS ring) over the elbow that serves as the outflow.