ORNAMENTALS - Kansas State University

Horticulture 2014 Newsletter
2021 Throckmorton Plant Science Cntr.                No. 30 July 29, 2014
Manhattan, KS 66506    (785) 532-6173

Video of the Week: Planting a Fall Garden

                                        ORNAMENTALS
Correction!

We mentioned last week that a cultivar of Eastern Redcedar, ‘Taylor’, was selected in Clinton,
OK by nurseryman Steve Bieberich. That is incorrect. It is actually a release from the Nebraska
Statewide Arboretum and was found in a pasture near Taylor, NE. We apologize for the
mistake. (Ward Upham)

Leaf Scorch on Maples

                                              Leaf scorch is starting to show up primarily on
                                              maples around the state. This is not a disease but
                                              rather a physiological problem associated with
                                              damaged roots, storm damage, limited soil area, or
                                              hot, dry winds. Moisture is lost so quickly from the
                                              leaves that roots can't absorb and transfer water
                                              quickly enough to replace what is lost. Though
                                              scorch is usually associated with droughty periods,
                                              it can appear even when the soil is moist.

                                               Scorched leaves turn brown or, in some cases, turn
black from the edges and between the major veins. If severe, the leaf may drop. Leaves may be
affected over the entire tree or may be affected only on one side. White pines are also prone to
this condition due to the delicacy of the needles.

Though scorch can be due solely to the weather, the condition of the roots of plants can make
them much more susceptible to this condition. Shallow soils such as those over hardpan or rock
lead to a limited root system that may not be able to absorb all the water needed. Trees may be
more sensitive to scorch this year because of the heavy rains some areas received in June.
Though soils were recharged, in many cases so much rain was received that oxygen was driven
from the soil resulting in root damage. That root damage is now making it more difficult for
trees to provide all the water needed for the leaves. Also, root damage due to disease, insects,
poor drainage or construction can cause poor water uptake.

To help alleviate damage due to dry soils or limited root systems, water once per week for

recently transplanted trees of every two weeks for large trees if there is no rainfall. Mulching
small trees or shrubs will help conserve moisture. (Ward Upham)

                                           FLOWERS
Peony "Measles"

                                                 The weather this summer has resulted in many
                                                 peonies catching the "measles." This is a disease,
                                                 also known as red spot, that causes distinct,
                                                 reddish-purple spots on the upper leaf surfaces.
                                                 These spots often coalesce and become large,
                                                 reddish purple blotches on the upper leaf surfaces
                                                 but are a light brown color when viewed from the
                                                 underside of the leaves. The spots on stems will
                                                 merge and form streaks that are reddish brown.

                                              Sanitation is the best control for this disease.
Remove all diseased tissue, including stems, at the end of the growing season. Mulch that
contains plant debris should also be discarded and then replaced with fresh mulch. Reducing the
source of the inoculum will reduce the chances of another severe outbreak next year. (Ward
Upham)

                                              PESTS
Cicada Killer Wasps

                                                 These large (1-1/3- to 1-5/8-inch long) wasps fly
                                                 slowly above the ground. Cicada killers have a
                                                 black body with yellow marks across the thorax
                                                 and abdomen. Wings are reddish-orange. Although
                                                 these wasps are huge, they usually ignore people.
                                                 Males may act aggressively if they are threatened,
                                                 but are unable to sting. Females can sting, but are
                                                 so passive that they rarely do. Even if they do
                                                 sting, the pain is less than that of smaller wasps
                                                 such as the yellow jacket or paper wasp and is
                                                 similar to the sting of a sweat bee. The cicada
killer is a solitary wasp rather than a social wasp like the yellow jacket. The female nests in
burrows in the ground. These burrows are quarter-size in diameter and can go 6 inches straight
down and another 6 inches horizontally. Adults normally live 60 to 75 days from mid-July to
mid-September and feed on flower nectar and sap. The adult female seeks cicadas on the trunks
and lower limbs of trees. She stings her prey, flips it over, straddles it and carries it to her
burrow. If she has a tree to climb, she will fly with it. If not, she will drag it. She will lay one egg
per cicada if the egg is left unfertilized. Unfertilized eggs develop into males only. Fertilized
eggs develop into females and are given at least two cicadas. Cicadas are then stuffed into the

female’s burrow. Each burrow normally has three to four cells with one to two cicadas in each.
However, it is possible for one burrow to have 10 to 20 cells. Eggs hatch in two to three days,
and larvae begin feeding on paralyzed cicadas.

Feeding continues for four to 10 days until only the outer shell of the cicada remains. The larva
overwinters inside a silken case. Pupation occurs in the spring. There is one generation per year.

Cicada killers are not dangerous, but they can be a nuisance. If you believe control is necessary,
treat the burrows after dark to ensure the female wasps are in their nests. The males normally
roost on plants near burrow sites. They can be captured with an insect net or knocked out of the
air with a tennis racket during the day. Carbaryl (Sevin) or permethrin may be used for control.
(Ward Upham)

Velvet Ants

                                            Adults of this insect are sometimes called
                                            "Cow-Killers" because of their powerful sting.
                                            These large (about 1-inch long), fuzzy red ants are
                                            not ants at all, but rather wasps. Velvet ant
                                            females are wingless (and resemble ants), while
                                            the males have blue-black wings and are usually
                                            found flying low above the ground in sandy areas.
                                            The female runs around searching for bumble bee
                                            nests in which to lay eggs. She will drop one egg
                                            beside each brood chamber. The young larvae will
                                            invade the brood chamber and feed on bee larvae.
                                            As mentioned earlier, velvet ants have very
                                            powerful stings. The best control is to avoid these
colorful and conspicuous insects. (Ward Upham)

Grasshoppers

                                              We have received a number of calls on
                                              grasshoppers recently. Permethrin (numerous trade
                                              names) is a good choice for vegetable crops
                                              because it is labeled for a wide variety of
                                              vegetables. However, keep in mind that hoppers
                                              can reinfest an area relatively quickly. Many times
                                              gardeners have not had an insecticide failure, but a
                                              reinfestation. Carbaryl (Sevin) can also be used for
                                              grasshopper control but can lead to mite outbreaks
                                              as it is very toxic to mite predators.

We often have gardeners who are interested in organic controls. Nosema locustae, a protozoan,
is the active ingredient in a number of products including Semaspore, NOLO Bait,
HopperStopper and Grasshopper Attack. These products are selective and will affect only
grasshoppers. This is a trait many gardeners find attractive. However, Nosema locustae products
may not be as effective in garden situations as they would be under large-scale rangeland
conditions due to potential reinfestations from outside the treated area. Also, these products have
other potential disadvantages:

- They are most effective against nymphal rather than adult grasshoppers. Also some
grasshopper species are less susceptible than others.

- Kill can take 3 to 6 weeks after ingestion.

- These baits are perishable and should be kept refrigerated until use. Pay attention to the
expiration date.

As mentioned above, reinfestations of uninfected grasshoppers can occur. These products are not
effective against adults. Try to treat the nesting area when hoppers are small and populations are
concentrated. Nosema locustae products are allowed in certified organic crop production.
Poultry including turkeys, guinea hens and chickens have also been used to help control
grasshoppers.

Regardless of method used, the trick is to treat early before the population has matured. Young
nymphal stages are much easier to control than adults and are also much less mobile. (Ward
Upham)

Spider Mites

                                    Hot, dry weather often means spider mites on tomatoes. Look
                                    for stippling on the upper surface of the leaves as well as some
                                    fine webbing on the underside of the leaves. These tiny
                                    arthropods (they are not true insects) are often difficult to see
                                    due to their size and their habit of feeding on the underside of
                                    leaves. If mites are suspected, hold a sheet of white paper
                                    beneath a leaf and tap the leaf. Mites will be dislodged and
                                    can be seen as tiny specks on the paper that move about.

                                  Spider mite control can be challenging. A strong jet of water
                                  can be used to remove the mites but may not be as easy as it
                                  sounds. A high-pressure directed spray is needed to dislodge
the mites. Since spider mites feed on the underside of the leaves, the spray is most effective if it
comes from below. This can be difficult to accomplish with a thumb over the end of the hose.
The only commercial product I have been able to find that is the Mite-Y-Fine sprayer from
miteyfine.com

Horticultural oils and insecticidal soaps (Safers, for example) can also be helpful. Spray early in
the morning when temperatures are cooler and plants have rehydrated. Resprays will likely be
needed. (Ward Upham)

Squash Vine Borer

                                               If you have squash or related plants that suddenly
                                               wilt and die, you may have squash vine borer. This
                                               insect will bore into the stems of squash, zucchini,
                                               pumpkins and gourds. Hubbard squash are a
                                               favorite, and butternuts are less likely to be
                                               attacked than other squash. Cucumbers and
                                               melons are usually not a target, although both can
                                               be affected by a disease that causes similar
                                               symptoms, known as bacterial wilt.

                                                The adult of this insect is a clear-winged moth that
resembles a wasp. The forewings are a dark metallic green but the rear wings are clear. The
abdomen is orange with black spots. The larva is cream-colored and rather wrinkled. Adults
emerge in the spring and lay eggs on or near
susceptible plants. Larva bore into the plant and feed for about a month as they move toward the
base. Mature larva will exit the plant, burrow into the soil and pupate where they remain until the
next year. Each plant can have numerous borers. If you suspect squash vine borer, split the stem
of a collapsed plant near where it enters the ground. Infested plants will be hollowed out and
mushy and may contain borers. Unfortunately, there isn't much you can do at this late stage.
Control measures should center on prevention.

Suggested preventative controls would include crushing the dull red eggs before they hatch,
excavating larvae from stems before they cause much damage or using insecticide applications.
Applications should begin when the vines begin to run (too late for that) and reapplied every
seven to 10 days for three to five weeks. Direct the spray at the crown of the plant and the base
of runners. Chemicals used for borer control in gardens are permethrin (Bug-No-More Yard &
Garden Insect Spray; Eight Vegetable, Fruit & Flower Concentrate; Lawn, Garden, Pet and
Livestock Insect Control; Lawn & Garden Insect Killer), bifenthrin (Hi-Yield Bug Blaster II,
Bug-B-Gon Max Garden Insect Killer) or carbaryl (Sevin), applied as sprays or dusts. Continue
on a 7 to 10 day reapplication schedule for 3 to 5 weeks. If plants wilt, look for the presence of
holes and ooze. However, in extreme heat, these plants will wilt in the afternoon even if
undamaged by this insect. (Ward Upham)

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