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- Southeast - Fall 2020
Mary Ferguson, Singh, Raghuwinder, Strahan, Ronald E., Fontenot, Kathryn, Fields, Jeb S., Kirk-Ballard, Heather
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The LSU AgCenter Soil Testing and Plant Analysis Laboratory is the only laboratory that incorporates the latest Louisiana-specific soil fertility research in its recommendations system. Kits include directions for gathering soil samples, a soil test request form, a sealable plastic bag and a pre-addressed, postage-paid box.
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When extension agents get calls about insects, it is often because one is, or appears to be, injuring a plant. However, the reality is that roughly 99% of insects are not “pests.” In fact, if you know what to look for, you may see insects that are helping to keep pest insects under control.
Many people have seen aphids on their vegetable or ornamental plants. These are sometimes called “plant lice.” They suck sap out of plants and excrete a sugary substance called honeydew. We often see sooty mold growing on that honeydew.
There are a number of beneficial insects and even some fungi that help manage aphids.
We sometimes see aphid “mummies.” The aphids have holes in them and look like they have been blown up like a balloon. This is caused by parasitoid wasps that lay eggs in the aphids. The eggs hatch, and the larvae feed on the insides of the aphids. The larvae pupate and become adults, which make holes in the mummies as they exit.
The larvae of some lady beetles (“lady bugs”) and of green lacewing insects also feed on aphids. Note that the larvae
of these insects do not look like the adults, so you might not recognize them. Both look sort of like tiny alligators. Lady beetle larvae are often black and orange, while lacewing larvae are brownish. If lacewing insects are present, you may also see their eggs, which are each perched on a “stalk.”
Like aphids, thrips are common insects, though they are often not noticed because they are so small. Some are problematic because they feed on flowers and thus affect flower appearance or fruit development. Some also spread plant viruses, like the tomato spotted wilt virus.
The minute pirate bug is one insect that preys on thrips. Like thrips themselves, minute pirate bugs are not easy to see with the naked eye, but with a hand lens, they can be observed to be black and white in color. Based on work done in Florida, it was found that having one minute pirate bug for every 40 western flower thrips was enough to provide adequate control.
If you have grown tomatoes, you very well may have seen tomato hornworms at one time or another. If you see white cocoons on the back of a hornworm, let that hornworm stay. The cocoons are those of a parasitoid wasp. These wasps lay eggs in the hornworms. After eggs hatch, larvae emerge from the hornworms and spin cocoons on their backs. The wasps will pupate in the cocoons, emerge as adults and, it is hoped, go lay eggs in other hornworms.
The final beneficial insect I will mention is the spined assassin bug. The adults of this insect are brown and readily seen with the naked eye. This is one of several different assassin bugs, which often hold other insects with their forelegs while feeding on them.
People sometimes inquire about buying beneficial insects for the garden. While this may be helpful in some cases, it is a more practical strategy for an enclosed structure like a greenhouse.
In the garden, one of the main things to do to encourage beneficial insect activity is to avoid using broad-spectrum insecticides when possible.
The pyrethroid class of insecticides includes those with active ingredients like pyrethrins, permethrin, bifenthrin, lambda cyhalothrin and esfenvalerate. These insecticides are some of the most effective options we have for some insects, like leaf-footed bugs and plant-damaging stink bugs. However, they are broad-spectrum and may kill insects that we would rather not kill as well.
Some insecticides have a narrower target range. We have a number of options for caterpillar pests. Insecticides with the active ingredients spinosad or Bacillus thuringiensis subspecies kurstaki are generally effective on caterpillars when they are small.
Spinosad is also effective on some other insects like thrips and citrus leaf miners. Spinosad can still negatively affect bees if they come in contact with it before it dries, so, as with any insecticide that can harm bees, wait and spray it in the late afternoon or evening when bees are no longer active.
Insecticidal soap (often called “potassium salts of fatty acids”) or horticultural oil products can help keep numbers of soft-bodied pests like aphids, thrips and spider mites low. Good coverage of plant surfaces, including the undersides of leaves, is essential when using these because they work on direct contact with the insect or mite.
These insecticides are generally more effective when pest numbers are few and insects are small, so try to keep a close eye on plants so that you will spot problems before they get out of control.
Before using any insecticide, make sure it is labeled for the plant on which you intend to use it, and follow label instructions.
Mary Helen Ferguson
Associate Extension Agent, Tangipahoa Parish
Aphid mummies on pepper leaf.
Photo by Mary Helen Ferguson
A ladybeetle larva, which is a
beneficial insect in the garden.
Photo by Raj Singh
Lacewing eggs on pepper leaf.
Photo by Mary Helen Ferguson
Lacewing larva.
Photo by Mary Helen Ferguson
Minute pirate bug.
Photo by Mary Helen Ferguson
Assassin bug captures a squash
beetle, which is a pest insect.
Photo by Mary Helen Ferguson
In the fall, October is traditionally one of the driest months in Louisiana. Turfgrass and lawns will suffer in the drought and heat with weeds, insects and diseases jumping at the opportunity to bring a weakened plant down.
How do plants combat a shortage of water coupled with temperatures approaching 100 degrees? Plants’ first line of defense is closing pores on the leaves and stems, preventing further water loss, followed by wilting. Eventually, plants drop their leaves in an effort to survive and go into dormancy to conserve everything they have. Ultimately, with no relief, some plants will die.
There are things we can do to help. First, select plants that can tolerate drought. Plants differ in their use and requirements for water. Some are tougher than others. Succulent plants, especially sedums, cactus, yuccas, aloe vera, crown of thorns and kalanchoe plants are some great examples.
Unlike turfgrasses, ornamental native grasses are great drought-tolerant plants. Mostly grown for beautiful foliage, many display gorgeous flower spikes called plumes. Some commonly used ornamental grasses for Louisiana landscapes are zebra grass (Miscanthus sinensis Zebrinus); pampas grass (Cortaderia selloana); fireworks fountain grass, (Pennisetum setaceum Fireworks), which is a Louisiana Super Plant; pink muhly grass (Muhlenbergia capillaris); and panic grass or switchgrass (Panicum virgatum).
In general, many native plants tend to be the most drought-tolerant plants for the landscape because they are adapted to our climate. No one can predict just how long droughts and heat will occur. So, we can plan and plant for just this occasion. If things continue as they are and climate change occurs, we will continue to see swings in temperatures coupled with decreased water availability in the years to come.
Choosing drought-tolerant plants and native plants is a good place to start. Where you plant them is also important. Plants that are growing under the canopy of a large tree are the first to wilt because they are no match for the extensive root system of trees, so avoid planting there. Turfgrasses tend to especially suffer.
Incorporate organic matter into your soil, use mulch, weed regularly, and supplement with additional water during droughts to help. The best time to water during a drought and hot weather is the early morning and late evening to help prevent evaporation and allow the plants several hours without sun to take up the water into their system. Infrequent but deep water is best. Use soaker hoses or drip irrigation for watering.
Dr. Heather Kirk-Ballard
Assistant Professor of Consumer Horticulture
Pink muhly grass. Photo by Allen Owings.
As crazy as this may sound, preparation for the fall garden begins in August. Yes, in sticky, hot, miserable August, we can start dreaming of cool-season crops. A few vegetable seeds can be planted into trays for later planting, and the ground needs to be prepared. Check out this veggie section for a few tips on growing a wonderful fall garden.
Remove weeds completely down to the roots.
If you see transplants next to a vegetable crop, those seeds were started in August.
Plant transplants or start seed:
Beets, broccoli, Brussels sprouts, cabbage, Chinese cabbage, cauliflower, collards, lettuce, kohlrabi, kale and Swiss chard.
The crops listed next should be seeded directly into the garden:
Beets, endive, carrots, English peas, snow peas, mustard, onions (seeds, mid-to-late September), parsley, snap beans (early September), radishes, rutabaga, spinach and turnips.
Garlic toes are planted in mid-to-late September. Shallot sets can be planted all month long.
These crops can be direct-seeded or planted by transplant:
Kale, parsley, spinach, leaf lettuce, celery, Swiss chard and endive.
These crops should be direct-seeded:
Mustard, turnips, radishes, beets, onions (early to mid-October to create sets for later) and carrots.
In south Louisiana, continue to plant transplants of:
Cabbage, cauliflower, broccoli, kale and Swiss chard.
In all of Louisiana, direct-seed:
Beets, Swiss chard, spinach, kale, radishes, mustard, carrots and turnips.
Continue to plant:
Shallots and garlic in the first part of the month.
Onion seed may be planted for transplants from mid-September through mid-October. Keep the soil moist because seed coats are hard. It may take two weeks for onion seed to germinate to a stand. Some people start the onion seed directly in the garden (planting it thick) and later pull up and transplant into final spacings. Other people start their onion seed in germination mix in trays. I prefer the germination mix in trays because it is easier to plant and maintain on a bench rather than in the ground. However, I have also seen gardeners sow the onion seed directly into the row at proper spacing. But to me this is risky especially in clay soils.
Transplant the onion sets into the garden from mid-December through the end of January. Several drills of seed may be planted on one row. Leave 6 to 8 inches between drills. I like a spacing of 4 to 6 inches between bulbs.
Pay special attention to weed control in direct-seeded onions. Control winter weeds before the onset of wet soils and cool weather. Consider planting onion plants in black plastic mulch. The mulch controls weeds, enhances growth and keeps the onion bulbs cleaner. You will also need to watch out for cutworms and thrips. For the cutworms use Dipel dust or Sevin dust on the ground. Thrips can also be controlled with spinosad, neem oil or horticultural oils. You know you have thrips when you see gray discoloration on the foliage.
Fertilize plants sparingly prior to planting in the ground. This will prevent excessive growth. The thinner the set is, the more resistant it will be to bolting when the temperatures drop. If your onions begin to bolt or bloom, pinch the blooms off to continue to increase the bulb size. About 2 to 3 pounds of 0-20-20, 7-21-21 or 8-24-24 per 100 feet of row are sufficient. Side-dress onions in the spring just before they bulb. Side-dress two additional times at two- to three-week intervals.
Dr. Kathryn Fontenot
LSU AgCenter Extension Vegetable Specialist
Bulbing onions after harvest. Photo by Kiki Fontenot
The Louisiana Super Plants program identifies superior plant material for Louisiana landscapes. Louisiana Super Plants have undergone rigorous trials at multiple LSU AgCenter locations across the state of Louisiana and have been vetted and approved by the Louisiana green industry. Louisiana Super Plants are considered university tested and industry approved.
As the summer winds down, we begin to look forward to fall and all the wonderful woody plants that thrive in the landscape. We generally recommend most woody plants be planted in the fall or late winter. This allows these plants to establish roots well before our extremely hot summers. In addition, many fall landscapes highlight amazing color provided by shrubs and trees. It is a perfect time to go get some Louisiana Super Plants to enhance your landscape.
The fall of 2020 inductions include two amazing woody plants that are well known throughout Louisiana and are popular among gardeners, landscapers, nursery growers and naturalists.
American beautyberrry (Callicarpa americana) is a native woody shrub that grows throughout the state of Louisiana. They are often found in wooded areas but can be grown as specimen plants in the landscape. While sometimes considered an understory plant, American beautyberry prefers part sun or dappled shade to thrive. American beautyberry is adapted to many soils. It can thrive in moist and drier areas but prefers acidic soils. The lime green opposite-leaved foliage provides an excellent contrast to the vibrant and eye-catching purple fruit that surround the stem at leaf nodes.
While the late summer onset of fruit is often a deep purple, forms are available in a variety of attractive colors of white, pink, burgundy and more. Birds, especially songbirds, love the large berry clusters. As a result, these are the perfect plants for someone interested in attracting wildlife to the landscape as this plant will attract birds in late summer and fall while offering a marvelous pop of color. American beautyberry is a very low-maintenance landscape plant, only needing light thinning if desired. Sheering will remove the flowers and fruit. Try planting many together to create an attractive native screen or hedge. Inconspicuous flowers fill the branches in midsummer and begin to develop green berries, which ripen into the vibrant colors in late summer to early fall.
The baldcypress (Taxodium distichum) is the state tree of Louisiana and is already iconic throughout the state. These native trees are prominent and can be observed growing throughout Louisiana and the entire southeastern U.S. They do well in moist soils and flooded areas; however, they are also adapted to dry soils, allowing them to thrive in almost any Louisiana environment. Baldcypress trees thrive in very hot humid environments, with faster growth during hot growing seasons, making it a perfect fit for Louisiana summers. Baldcypress is a deciduous conifer, which means it is one of the few cone-bearing plants that loses its leaves in the fall. At maturity, a baldcypress will grow up to 50 to 70 feet tall and as much as 25 feet wide.
The baldcypress is known for attractive pyramidal shape with lacy green needles. These needles turn a wonderful rust color in the fall prior to dropping, where they provide natural mulch and serve as protection for a host of wildlife. Baldcypress provides some of the best fall color seen throughout the state of Louisiana. Additionally, baldcypress is desired for its ornamental bark. When grown in wet conditions, baldcypress will form “cypress knees,” which provide additional aesthetics for ponds. A host of aquatic, avian and ground-dwelling wildlife rely upon these trees for nesting, food and shelter throughout the year. Baldcypress makes a great addition to any landscape, natural area or public space throughout the state and provides a conceptual connection to nature and the great state of Louisiana.
For more information on Louisiana Super Plants, please contact your local LSU AgCenter extension office or visit www. LSUAgCenter.com/SuperPlants.
Dr. Jeb S. Fields
Assistant Professor and Extension Specialist
Hammond Research Station
American beautyberry
Baldcypress
Storm drain clogged by leaves and lawn debris. Photo by Heather Kirk-Ballard
Louisiana usually stays warm well into the fall, and lawns continue to grow until nighttime temperatures dip into the 50s. So be sure to mow and water your lawn, as needed, to keep it healthy.
More than likely, however, it is time to put up your fertilizer spreader. Fertilizing warm-season grasses during the fall with high nitrogen (summer-type) fertilizers or winterizing fertilizers containing high levels of nitrogen are not recommended for Deep South lawns.
Stimulating fall growth of St. Augustinegrass, centipedegrass and zoysiagrass with nitrogen leads to increased large (brown) patch disease and winter kill. Bermudagrass may be fertilized into September, but I would not make any more applications of high percentage nitrogen-containing fertilizers after late August on St. Augustinegrass, centipedegrass or zoysiagrass.
If you would like to extend the green color in home lawns this fall, apply foliar iron spray or spreadable iron granules. This will give you a nice flush of green color without increased growth.
I’m sure that you have heard of winterizer fertilizers. Potassium (the last number in the analysis on fertilizer bag) is the nutrient associated with winter hardiness and increased disease resistance with turfgrass. There is an advantage to having the correct amount of potassium in the soil. Get a soil test before applying high potassium fertilizer, however, since there is no advantage to applying excessive amounts of this nutrient. If a soil test indicates that potash is lacking, choose a potassium containing fertilizer with zero or a very low percentage of nitrogen (the first number on a fertilizer bag) during the late summer or early fall since we are not trying to stimulate growth for the reasons discussed above. If a soil test calls for adding potassium, you can apply during September while temperatures are still warm, and the lawn is still growing (very slow growth occurs as day lengths get shorter by late September and October).
An important fact to consider if you bag your lawn clippings - the removal of grass clippings from lawns can severely deplete the soil of potassium. Grass leaves and stems contain very high levels of potassium. Keep in mind that when a lawn is mowed appropriately, it is better to leave clippings to decompose on the lawn as a good source of turf nutrients, including potassium. Clippings from a lawn that is mowed regularly have only a small role in the overall buildup of thatch in turfgrass.
Fall is the best time of the year to get your soil tested by the LSU AgCenter Soil Testing Lab.
Soil testing really is the first step to a beautiful lawn next spring and is the best way to determine exactly what your lawn needs to become thick and healthy. If you haven’t tested your soil in the past several years, do it now.
To test your soil, submit a pint of soil to the LSU AgCenter Extension Service office in your parish. The pint should be a composite of soil samples collected from several different areas in the lawn. You only need to go about 4 inches deep. Also, to simplify the soil sampling and submission process, there are pre-addressed submission boxes with sampling instructions at several garden centers throughout the state. There is a small fee for testing.
The sample results will be sent to your home mailbox and email in less than two weeks. An LSU AgCenter extension agent can help you interpret the results from the soil sample. The sample results may indicate that lime is needed to increase soil pH. If so, fall/winter is a good time to apply lime, since it takes several months to activate in the soil. Elemental sulfur may be recommended to reduce soil pH in alkaline soils.
If your lawn was full of winter weeds last spring, this fall is your first opportunity to reduce infestations with pre-emergence herbicides. Pre-emergence herbicides such as prodiamine, pendimethalin, dithiopyr, isoxaben, and indaziflam may be applied in mid to late September to help manage the first flush of winter weeds like annual bluegrass, chickweed and lawn burweed. Consider reapplication in early November. These herbicides work prior to the emergence of the weeds, so timing the application before the weeds germinate is critical. Atrazine can be applied on most southern lawns for annual bluegrass and broadleaf weeds in October except for bermudagrass. Atrazine could be applied on bermudagrass after the bermudagrass is dormant. MSM (metsulfuron) can be highly effective postemergence on broadleaf weeds such as white clover and lawn burweed.
Ron Strahan Ph.D.
Associate Professor, LSU AgCenter
Annual bluegrass is the most common grass infesting winter lawns.
Lawn burweed germinates in the fall and produces painful stickers in the spring.
Wild geranium is a common winter broadleaf infesting fall lawns.
Home gardeners are often distressed by the appearance of slime molds during extended periods of overcast skies and warm and wet weather, which is very common in Louisiana.
Slime molds appear as crusty or powdery coatings on any surface, including wooden planks used for making raised beds, garden mulch, lawns or even on the leaves and stems of different kinds of plants grown in gardens.
The encrusted cover is usually a powder buildup that wipes off easily. This dusty coating may appear in different colors, like ashy gray, brown, charcoal gray, dark red, purple or bright yellow. One slime mold is named as “dog’s vomit” because of its appearance.
During favorable weather slime molds may remain in your garden or turf for a few days to more than a week.
Slime molds are nonparasitic organisms that are classified as myxomycetes, a group of free-living amoeboid protists. Slime molds feed primarily on bacteria and other microorganisms.
Slime molds’ life cycles are a bit complicated and have two different stages, an amoeboflagellate stage and a plasmodium stage. After feeding on soil microbes, fungi and organic matter, the amoeboid cells during the amoeboflagellate stage grow and multiply to form a plasmodium stage with a greasy, viscous slimy appearance.
The greasy-looking slimy plasmodium may take on one of many colors or remain clear. It creeps upward on grass leaves, low-growing plant materials and ground covers to support itself up off the ground for better spore dispersal.
The plasmodium further bunches up and develops into a fruiting or sporangium stage. This stage is the most visible and is commonly noticed in gardens and lawns.
In this elevated stage, the mature spores are released for dispersal by wind, rain or other vectors. As grass and plants dry, the sporangia dry to a crusty or dusty “crud.” Slime molds tend to reappear in the same general areas when conditions become favorable again.
Slime molds are harmless to plants and turfgrass and do not cause any diseases on them. However, if the plant tissue is heavily covered with slime mold for more than a week or so, it can shade out the plant tissue. The plant tissue may turn yellow and become susceptible to secondary disease infection.
Control of slime molds is often not needed. They start disappearing with the onset of dry weather. Slime molds can be hosed or brushed off the plant tissue but avoid hosing or brushing off during wet weather.
Gardeners who desire to remove the slime molds by hand must wear disposable gloves as spores may cause irritation to sensitive skin.
Excessive thatch buildup in lawns favors slime mold development; therefore lawns should be dethatched at regular intervals.
If chemical control is desired, contact your local extension agent to find a product that can be used to manage slime molds in landscapes, gardens and lawn turf.
For information on slime molds, please call 225-578-4562 or email rsingh@agcenter.lsu.edu.
Dr. Raj Singh
Plant Pathologist and Director of Plant Diagnostic Center
Figure 1: Slime mold at base of a tomato plant grown in a raised bed. LSU AgCenter photo
Figure 2: Slime mold growing on the leaf blades of turfgrass. Photo by Raj Singh, LSU AgCenter
Figure 3: Slime mold growing on leaf surfaces of Greek oregano. Photo by Leigh Ann Cabaniss
Figure 4: Slime mold growing on the surface of wet mulch. Photo by Andre Brock, LSU AgCenter
Horticulture Hints Fall 2020 Southeastpdf / 1.22MB