Vegetable gardening is in full swing across southwest Louisiana. With the large variety of vegetables that are now planted, we are starting to see several different issues arising in the garden. Although the couple problems that we are starting to see (that will be discussed), neither one is detrimental in vegetable production if caught early on and treated properly.
One problem that we are starting to see quite a bit of is powdery mildew on vegetable foliage. Over the past couple weeks, I have received quite a few calls and have seen quite a few instances where squash, cucumbers, eggplant, tomatoes and snap beans have been covered with this fungus. One of the most obvious symptoms of powdery mildew is when vegetable plants actually have this fungus, the foliage (and possible fruit) will look like it is covered in a fine white powdery substance (it may or may not cover the whole leaf) and looks almost like dust. The mycelium of the fungus will have a tendency to form light mats and appear as white, grayish-white or tan colored patches on the leaves, buds, stems or even young fruit. Infected leaves will also appear chlorotic (have lost some of their green color) due to a lack of photosynthesis. Another symptom that occurs in affected foliage is that once the leaf is infected, the leaf itself will want to have a tendency to curl up and possibly drop (leaf drop can occur in more severe cases).
This disease, although is not a pretty site, is usually not fatal. It is more of a cosmetic issue that can affect the photosynthesis process which can ultimately affect the overall yield in the particular vegetables that have powdery mildew. One way to help prevent the disease is by possibly thinning out the foliage and letting more air circulate through the plant. Another way that you can decrease your chances of getting powdery mildew is by choosing resistant varieties and plant in sunny locations. You can protect the plants before they get powdery mildew by spraying potassium bicarbonate, sulfur or other fungicides on the foliage as a preventative measure. Once the plants are diagnosed with this fungus, treatment is pretty easy. There are several options that you can use in order to treat powdery mildew; you can use the suggested sprays that were listed above or you can use either mancozeb or chlorothanil, both offer good effects on the fungus.
Another issue that I am starting to see a lot of and get calls on is aphids that have infested the garden. These are small, delicate insects that are usually yellowish-green in color and can be wingless or have wings. These tiny insects can be found on the bottom side of the leaf as well as on the top side and the stalks of the plant. If you suspect that your garden has aphids, you can turn the vegetable leaves over and inspect the bottom side of the leaves. They are visible to the naked eye and can usually be seen crawling around; they will look like tiny green dots on the bottom sides of the leaves. These insects have piercing mouthparts that can penetrate into the leaf and suck out the juices causing the leaves to curl up and dry out. Controlling this insect shouldn’t be too much of a problem if caught before the problem gets too bad. Once you have identified the insect, you can control aphids with a light paraffinic horticulture oil or you can use malathion (depending on the severity of the infestation, it may take more than 1 treatment of either option you decide to use). Both products will do a good job and give you some nice coverage in controlling this insect.
One thing to remember when using any pesticide, whether it is a fungicide to control powdery mildew or malathion to control aphids, always read the pesticide label and make sure that you follow proper procedure when administering the pesticide. Properly managing your garden and inspecting for anything out of the ordinary will give you the upper hand and allow you to notice something as soon as it happens. If this is done and proper treatment (if necessary) is done, your garden should reward you with a plentiful harvest.
For more information, come by or call our office at (337) 788-8821 or you can visit our website at http://www.lsuagcenter.com.