August 2024 Hort Tips

Thursday, August 1, 2024

Fall Pecan Field Day Scheduled for September 19

Becky Carroll, Senior Extension Specialist

Plan to join us at the Fall Pecan Field Day on September 19, 2024. The past few fall field days have focused on native pecan production but this year we will visit an improved pecan orchard owned by OSU retired pecan researcher, Dr. Michael Smith.

The orchard is in Pawnee County at Michael Smith’s Cedar Creek Pecan Farm at 364839 E. 5200 Rd, Cleveland, OK 74020. Check-in will begin at 2:30 p.m.; Program at 3:00 p.m.

A follow-up email will be sent to registrants with additional directions.

Mike’s orchard was first planted in 1993-94. Kanza and Pawnee are the predominate cultivars in the 32-acre orchard. Topics will include establishment, weather setbacks, irrigating from ponds, nutrition, clover cover crops, and other management practices.

We will also focus on timely topics of harvest equipment maintenance; wildlife depredation; weevil trapping and control; 2024 disease update; and drought stress effects.

Participants are encouraged to bring a lawn chair to get comfortable and enjoy a nice fall afternoon! And, if the weather turns off wet, we will have an alternate site and will email you with any changes.

There is no charge to attend, but registration is needed to be able to plan for dinner. Be sure to register by September 16 at Register me!

Cedar Creek Pecan Farm, Oklahoma State University Pecan Management, Pawnee County Extension, and the Oklahoma Pecan Growers Association welcome anyone interested.

For more information, contact becky.carroll@okstate.edu or (405) 744-6139.

Garden Accessibility

David Hillock

The American Horticulture Therapy Association offers the following advice on creating an accessible garden.

Site Selection. Choose a site that is relatively level, offers good sun exposure and water drainage. A source of water and tool storage should be nearby.

Garden Design. Design the garden to meet the specific needs of the primary gardener. Certain pointers will help make the garden wheelchair accessible:

Paths should be 36” wide to accommodate a 28” wheelchair; the maximum slope should be 5%; path surfaces should be firm and of a non-slip material; at sharp corners, paths should widen another 12” to provide adequate turning radius.
Raised beds can eliminate bending. Add a wide lip to the top of the bed to create seating. Seated gardeners will find an 18” working height comfortable, while those in wheelchairs will do better with a 24” high bed. If beds are accessible from both sides, they may be 4’ wide, but reduce the width to 2’ if accessible only from one side.
Standup Gardens. This is a portable gardening system 32” wide by 4’ long and 10-12” deep placed 32” off the ground, providing the same ease of working in your garden as working at your kitchen counter.
Vertical Gardening. Vertical planters can be hung at a convenient level to reach or hanging baskets can be placed on pulleys to lower for maintenance.

Tools. Look for ergonomically designed tools with such features as larger or softer handles, wrist supports, light weight design or pistol grips which make them easier to use.

PawPaw

Casey Hentges, Associate Extension Specialist

Bailey Singleton, Extension Assistant

You may have heard of a pawpaw, but few have had the privilege of eating one. The pawpaw tree is a large, native tree that can grow about 25 feet tall. Its native range is from Florida to Texas and north into New York and Southern Ontario. Because it is hardy to zone 5 and prefers slightly acidic soil, these trees are well suited for eastern Oklahoma. Young trees prefer being established under the shade of mature trees but will continue to grow in order to get more sun exposure. The edge of an established tree line is an option for planting because it will provide some protection while the tree is young. If found in the wild, they usually have suckered into a “pawpaw patch” especially in low lying areas that have ample moisture.

Pawpaws that are in full sun often have a pyramidal form with branches lower on the trunk. Some trees have more of an open branch structure and this is likely because they receive more shade.

Pawpaws are sometimes referred to as the Indian Banana because they were a major component in the Native American diet. While the trees are native, they have a very tropical appearance and flavor to their fruit. At the end of summer, they produce large green, potato-like fruit clusters hanging in the trees. Most people have not tasted a pawpaw because they have a short shelf life. The fruits are ripe right before they are about to fall off the tree. When a fruit is cut into, it has a bright yellow flesh with large dark seeds inside. Do not eat the skin or the seeds. The flavor of a pawpaw is described as a mix between a banana and a mango.

In addition to the tropical flavor, their large, bold green leaves will add further appeal later in the fall as they turn bright yellow.

In order to grow pawpaw for the fruit, two plants are needed as they are incompatible to self-pollinate. In the spring you will see burgundy, brown flowers that are about 1”, when pollinated with a genetically different pawpaw, will eventually bare these fruit.

There are few pests that are of concern for growing the pawpaw, and in fact are actually a host plant for the zebra swallowtail butterfly, whose larvae feed only on young pawpaw foliage.

If you are looking for a new fruit to add to your garden, you might consider adding at least two pawpaw trees. View this YouTube video.

Managing the Heat and Drought in the Landscape

David Hillock

To survive the summer months, plants must have relief from hot, dry periods, especially this time of year. Here are some suggestions to help combat this challenge.

Evaluate your priorities. If irrigation is limited, some areas may need to be sacrificed for the good of others. Established trees and shrubs are a good example of plants that should be at the top of the list, as they are virtually irreplaceable. Established trees take many years to replace when one is lost. Perennials and seasonal plants might be your second priority. Well established bermudagrass lawns can tolerate quite a bit of drought if necessary and will recover once irrigation is resumed.
Identify the root zone of important plants. Do not water areas that are of no benefit. Trees and shrubs usually have roots that extend at least to the drip line or reach of the branches and often go well beyond that.
Apply water directly to the ground, if possible, to reduce loss of water through wind or evaporation. Applying water directly to the ground and root areas, keeping the foliage dry, can also reduce foliar diseases. Drip systems or a soft-spray head or water wand are generally more efficient than pop up sprays. Drip irrigation kits can be found at most home improvement and garden stores and are easy to install.
Water deeply once or twice a week, depending on the soil type, in the early morning or late evening. This will encourage deep roots. Avoid run-off so you do not waste water.
Mow grass a little higher. Taller grass shades the roots. Do not fertilize during droughts.
Mulch, mulch, mulch. Use 1 to 3 inches of organic mulch on landscape beds and around trees. Keep mulch away from direct contact with the base of plants to avoid rot. Some communities offer free mulch. Use it! It keeps the ground cooler, blocks weeds, and conserves moisture.
Plant natives or well adapted exotic plants. Native plants withstand our droughts and crazy weather quite well. Research those that do best in your area of the state. Natives from eastern Oklahoma may not do as well in western Oklahoma.

Controlling Winter Annual Weeds

David Hillock

If winter annual weeds, such as henbit and annual bluegrass, have been a problem in the past then you will want to apply a preemergence herbicide in late August through mid-September. Many of our winter annual weeds germinate in the fall or early winter and survive as very young plants until late winter or early spring when conditions are more favorable for growth. Waiting until you notice them is too late.

The key to effective control is timing. Preemergence herbicides must be applied well in advance of the expected germination time of the weeds to be controlled, for winter annual weeds this is by September 15. In addition, the products must be watered in to activate them. At least ½ inch of water either through rainfall or irrigation if no precipitation is expected, within a couple days after application is recommended. In some cases, the product needs to be incorporated into the upper surface of soil.

There are several products available in the garden centers that will effectively control germination of most winter annual weeds. Some are labeled just for turf areas, some labeled for both turf and ornamental areas, and some for vegetable gardens. There are several to choose from; choose one that is labeled for your site/situation and labeled to control the weeds you are targeting. Be sure to read and follow the label directions for the best results and to avoid damaging any desirable plants.

Note: if you plan to seed any areas this fall do not apply a preemergence herbicide!

Fall Webworms

David Hillock

The fall webworm, Hyphantria cunea, is most observed feeding in groups on the foliage of host plants from within a web constructed on branch terminals. Webs are most prominent in late summer or early fall, but in outbreak years their webs are noticeable earlier in the summer.

Fall webworms are found over most of Canada and the United States and into northern Mexico. They are present over all of Oklahoma but are more common in the east than the west.

Adults of the overwintering generation emerge during May or occasionally in late April. Egg laying occurs in late May and early June. Each female can lay 400 to 500 eggs in masses on the underside of leaves. Egg masses are covered with white hairs from the female’s abdomen and may have a pale green background color. Two races or forms of the larvae occur in Oklahoma, the blackheaded and redheaded forms. The redheaded form is more commonly encountered on pecan and persimmon in Oklahoma.

The fall webworm has been recorded on at least 88 species of shade, fruit, and

ornamental trees in the United States. The preferred hosts vary from one area to another. In Oklahoma, persimmon and pecan are most commonly infested and black walnut and hickory are also common hosts. Sycamore, birch, and redbud are often attacked in years of heavy infestations. Infestations on cottonwood, American elm, and bald cypress have been reported. The black‐headed form is sometimes common on sweetgum.

Damage is caused by the larvae feeding on the leaves. They rarely are heavy enough to defoliate trees except for young pecans and persimmons. On most forest and shade trees, the insect is detrimental mainly to the beauty of the host and is thus more of a nuisance than a threat to the health of the tree. Actual damage can occur on pecans as defoliation affects tree vigor, yield, and nut quality. The earlier defoliation occurs, the more harmful the damage.

Control is rarely warranted for fall webworm because it is usually a nuisance pest. However, control may be necessary to protect pecan yield and tree vigor.

Cultural control: Larvae and their webs may be cut out of small trees and destroyed, but larger trees with webs present high in the canopy should be treated with insecticide to achieve control.

Biological control: More than 50 species of parasites and 36 species of predators attack fall webworm in North America. These natural enemies occur naturally and likely contribute to regulating fall webworm populations in non‐outbreak years.

Chemical control: When using conventional insecticides that rely on contact, sufficient spray pressure is needed to reach and penetrate the webs of these caterpillars. Several insecticides will normally provide control if adequate spray penetrates the webbing. A biorational approach to managing webworms can include the use of Bacillus thuringiensis var. kurstaki, a bacterial insecticide, or products containing an insect growth regulator (e.g., tebufenozide, methoxyfenozide) that are specific to caterpillar pests. Either of these latter materials can be applied near the webbing area and the caterpillars will eventually expand their feeding into the treatment zone. However, products containing these insect growth regulators can only be purchased and applied by a licensed pesticide applicator.

(Source: Bagworm and Fall Webworm Management )

Pecan Developing Earlier Than Normal Years

Becky Carroll

Checking pecan development is key to determining several important management needs. We are about 10-14 days early this season and growers may miss important stages

For those with improved cultivars, crop load should be assessed to decide if nut thinning is needed. For large-fruited cultivars like Pawnee, 50% of the terminal shoots should be carrying a cluster. If the percentage of shoots is higher than 50%, crop thinning should be done. Identify an area in the middle of the canopy to count clusters. This webinar recording describes how to determine crop load.

If crop thinning is needed, nut development should be in the 50 to 100% embryo expansion and in the water stage. Cut the pecan in half lengthwise to view the ovule or embryo. The ovule expands from the bloom end to the stem end. Pecan Crop Load Management. At the Cimarron Valley Research Station, they began thinning Kanza trees on July 25. This is about two weeks earlier than the average thinning date.

What are we looking at?

The inside of a pecan.

Figure 1. Longitudinal Section of a Pecan with the Ovule About 50% Expanded.

The photo below shows the Kanza at about 90-100% expanded, Pawnee about 60% expanded, and Maramec about 30% ovule expansion. The Maramec ripen later in the season than Kanza and Pawnee.

Nut development on July 23, 2024 @CVRS

The inside of a pecan nut.

Crop Load Thinning video - explains why, when, and how to thin pecans. (Fun drone footage of crop thinning).

Another key stage to watch for is when the nuts advance from water to gel/dough stages. During the water stage, any weevil probing will result in nut drop but once they transition to gel, the nuts are susceptible to egg laying. This may be early this season as well. Start monitoring for weevil activity and check nut stages regularly.

Irrigation during the water stage will help make larger pecans. Once shells begin to harden, sizing is completed. Irrigation should be applied during the dough stage for best kernel quality and to fill out the kernels. Two inches of water each week during sizing and kernel fill is needed. If you have limited water, save the supply for filling time and reduce during sizing. It’s better to have small, well-filled pecans than large, wafery pecans.

If hickory shuckworm has historically been an issue, apply an insecticide at shell hardening to help with their control. Pecan scab infections after shell hardening are more cosmetic than detrimental.

Growers should use all their tools available for managing a pecan orchard or grove. Eyes on the crop are the most important tool of all. Growers can’t know the timing of needed management unless checking crop development.