Downy mildew on cucumber.
Photo: Dr. Don Ferrin, LSU AgCenter.

Squash Mildew

Erin is already looking forward to growing spring vegetables and sent this question, “How can I stop mildew in cucumbers and squash leaves that stunts their growth?”

Dr. Don Ferrin wrote in a publication, “Downy Mildew of Cucurbits” about treatments, “Disease control relies primarily on the use of fungicides since resistant varieties are available only for cucumbers and some melons (but not watermelons). Fungicides are most effective when they are applied before the onset of disease, and they must be applied repeatedly if environmental conditions are suitable for disease development. Because this pathogen can develop resistance to fungicides quite readily, it is important to follow label instructions regarding their use.”

AHA examined the AgCenter’s “Disease Management Guide” for fungicides suitable for mildew control:

• Bonide Fung-onil Multi-purpose Fungicide
• Ferti-lome Broad Spectrum Landscape & Garden Fungicide
• GardenTech Daconil® Fungicide
• Hi-Yield Vegetable, Flower, Fruit and Ornamental Fungicide
• Scotts Ortho® MAX® Garden Disease Control

Here are some copper fungicides:

• Bonide Copper Dust
• Bonide Garden Dust (also contains an insecticide)
• Bonide Liquid Copper Fungicide
• Bonide Dragoon Dust with Copper
• Concern Copper Soap Fungicide
• Liqui-Cop Copper Fungicide Garden Spray
• Natural Guard Copper Soap Fungicide
• SA-50 Southern Ag Liquid Copper Fungicide

Copper fungicides can be used for organic gardening but should not be mixed with liquid fertilizers. Another caution regarding copper fungicides is to avoid water with a pH less than 6.5, or the copper treatment will be less effective. Finally, copper fungicides can stain masonry and concrete.

A Mediterranean gecko.
Photo: Nathan Smith.

Mediterranean Gecko

A homeowner sent a picture an animal that he thought was venomous and wanted AHA to confirm his concern. The animal in question looks like the one in this image.

This critter is a Mediterranean gecko, a harmless, exotic lizard established in the Gulf coast of the United State. It does feed on insects and could be beneficial. It can be a nuisance in the home when it looks for a warm place to go, but it is otherwise harmless and non-venomous.

Sidewalk heaving by oak trees in New Orleans.
Photo: NOLAmusings.com.

Sidewalk Heaving

Before Dan Gill retired as an AgCenter horticulturist, he shared some information with AgCenter horticulture agents in Louisiana. This note would be helpful to homeowners. He received an email from Kathy B. who asked,“Hi Dan, I have a large oak tree in my front yard located approximately three feet from the side walk. There is one root which is pushing up between breaks in the sidewalk and making the sidewalk uneven and hazardous. If I replace a section of the sidewalk and grind the root down will the tree be harmed?”

Gill offered these helpful comments, “Yes, the tree will be harmed. Roots do two main things for a tree:

1) They absorb the water and minerals the tree needs from the soil. Removing large roots like the one damaging the sidewalk will reduce the tree's ability to absorb water and this may negatively affect its health and vigor (although this is not a matter of life and death).

2) Roots hold the tree up. The only things that keep a tree from falling on your house in a storm are the roots. Cutting major roots weakens the roots system and increases the chances of a tree going over in a storm.

If possible, repair the sidewalk without cutting or grinding down the root. If this is not possible, you will just have to accept the negative consequences it may have on the tree.”

Filamentous algae.
Photo: aquaplant.tamu.edu.

Filamentous Algae

Homeowners may be seeing stringy algae growing in their garden ponds this winter. Dr. G

Greg Lutz, a fisheries and pond specialist with the AgCenter, made these useful comments, ““[Filamentous, slimy algae] gets started on the pond bottom during the winter months when the water is clear, then grows into big clumps as the water warms up. The unusually cold weather we have been having has caused many ponds to get very clear, and this creates ideal conditions for the filamentous algae as the winter progresses.

The best approach in terms of cost, labor and effectiveness is to use copper sulfate crystals to limit the growth of the filamentous algae. This product is available at most big feed and seed stores or farm co-ops. Tell your clientele to observe a limit of no more than 5 pounds of crystals per acre, per treatment. The crystals should be sprinkled or broadcast directly onto the clumps of filamentous algae - a little goes a long way. When roughly 5 pounds per acre (that would be 2.5 pounds in a half-acre pond, 10 pounds in a 2-acre pond, etc. etc. etc.) have been applied - even if only 1/4 or 1/3 of the algae in the pond has been treated, no more copper sulfate should be applied. After 8 days another treatment with the same number of crystals can be applied. There is usually little or no fish mortality when people stick to this strategy, but clientele should be made aware that there is always some risk of killing fish when treating aquatic vegetation. Are there more efficient ways of dealing with filamentous algae? In some cases, there probably are, but I have found over the years that it’s better to have folks knock this stuff back gradually rather than hit it hard and then blame us when they kill some fish.”

The AgCenter has a downloadable publication entitled, Management of Recreational and Farm Ponds in Louisiana, and this publication is a handy reference for any landowner with a pond.