Squash Vine Borer

photo credit: Dr. Alan Windham, Univ. of TN Extension Plant Pathologist

Squash vine borer (SVB) damages squash, gourds, and pumpkins. Cucumbers and melons are usually not attacked by the SVB.

The adult SVB is a clear-winged moth. The 1 inch long adult moth is commonly mistaken for a wasp. Its abdomen is ringed with orange and black. Females lay oval brownish eggs on plants in late May or early June. The borers tunnel into stems near the soil and feed on the plant. Excrement is visible near points of entry on the stem when larvae are feeding. Heavy feeding causes the infested vine(s) to wilt and die.

Select a variety which is SVB tolerant. Also, cover emerging plants with row covers to reduce possible damage. Remove row covers when the plants begin to bloom to permit insect pollination. Stagger new plantings every 2-3 weeks to avoid SVB populations.

Some gardeners cover the main stem with pantyhose to prevent egg laying by adults. Infested stems can be split and larvae removed. Add a spade-full of moist soil over damaged stems to encourage new root growth. Insecticides must be applied prior to borers entering into the stem.

Insecticides containing carbaryl, bifenthrin, spinosad, or permethrin are effective against SVB. Apply an insecticide every 5-7 days. Please read the pesticide label before applying.

Eastern Tent Caterpillar (crabapple, cherry, peach)

photo credit: Dr. Frank Hale, Entomologist, University of Tennessee
The Eastern tent caterpillar is frequently the first insect that I receive calls about in the spring. Eggs overwinter on wild cherry trees and move on long silken treads to tasty landscape tree foliage nearby. Larvae and caterpillars consume lots of leafy matter over the next month.

Dirty white webs form in limb crotches beginning in late March when wild cherry leaves are developing. Larvae leave the web on warm sunny days to consume leaves of ornamental crabapple, peach and cherry. They remain in the web during cloudy or rainy weather.

Large landscape trees are damaged temporarily, and new foliage grows back rapidly. However, newly planted or young trees may lose most of their 1-2 year old foliage and have no reserves to grow new shoots.

In March and April, many different insecticides are labeled including horticultural oil, Sevin (Carbaryl), Bt (Dipel), Orthene, Malathion, and insecticidal soap. Always read the pesticide label for all precautions. For example, the label on Orthene states “may cause foliar injury to flowering crabapples”.

Best of Perennial Veronicas for Gardens

photo: Veronica spicata 'Royal Candles' (not evaluated in CBG study)

Chicago Botanic Garden (CBG) has published the results of a 10-year study of speedwells (Veronica and Veronicastrum) in its 33rd issue of Plant Evaluation Notes, “A Comparative Study of Veronica and Veronicastrum".

Seven speedwells received good-excellent ratings for their overall performance, including Veronica ‘Fairytale’, V. ‘Giles Van Hees’, V. austriaca ‘Ionian Skies’, V. longifolia ‘Blue John’, V. spicata ‘Baby Doll’, V. spicata ‘Ulster Blue Dwarf’, and V. wormskjoldii. These top-rated speedwells exhibited strong growing and excellent flower production throughout the evaluation period. The lack of any serious pest or disease problems, along with good winter survivability, contributed to their high ratings. Additionally, 18 taxa received four-star good ratings for similarly strong performances.

Speedwells are generally easy to grow and prefer sunny locations in moist, well-drained soils. Plants grown in less light will not bloom as profusely and may become lax or open in habit. Crown loss or plant death may occur in wet soil conditions in winter.

Many speedwells require a midsummer shearing after the first bloom to promote a healthy new basal foliage and to encourage late summer flowering. Deadheading of spent blooms produces many new bloom spikes later in the summer. By selecting the best cultivar(s), you may avoid potential foliar diseases, including powdery mildew, downy mildew, leaf spots, and foliar rust.

Generally, plant disease pressure is more severe here in the Southern Appalachian Region than in the Midwest. Read the entire 8 page CBG report (Issue 33, 2010) authored by Richard G. Hawke.

Japanese Apricot Blooms in Winter

Japanese apricot (Prunus mume) is a beautiful reminder that the worst of winter may be behind us. On days barely above freezing, the light pink fragrant blossoms open, rarely in great numbers. Cold nights freeze the blossoms but other buds will open during the next warmup.

Japanese apricot is cold hardy in garden zones 5 thru 7. It is a small 10-12 foot tree, rarely bearing fruit. Plant in a full sun area of the garden, near decks and patios where you can visually enjoy the winter bloom from inside your warm home. The tree is likely to coax you outside.

Japanese apricot does not prosper in hot or dry locations. Plant in a moist, well-drained soil, mulch when needed, and prune to maintain an open branched tree. Over a dozen cultivars are available in white, pink, or red tones and single, semi-double or double blossoms.

Salt Damage on Trees

Winter 2010 lingers on across Tennessee, Virginia and North Carolina. The white coating of de-icing salts over streets and highways can damage many trees and shrubs. Salt spray and salt deposits may also leach into the soil and become equally damaging. Plant species vary in their sensitivity to salt injury.
Browning of the tips of needle and broadleaf evergreens is a typical symptom of salt injury. Needle loss can be an extreme result, with evergreen branches becoming progressively bare. Often, evergreens become so weakened and stressed that new spring growth does not slow the needle/leaf loss. Overall tree health gradually declines.

The following practices can minimize salt injury to trees and shrubs:
1. Applications of water will leach some salt out of the root zone. Plentiful spring rainfall will help in this leaching/cleansing process. As much as 6 inches of water is needed to leach about half the soluble salts. In addition, applying gypsum (calcium sulfate) displaces the sodium in the soil.
2. Plant trees in salt-prone areas that are less vulnerable to salt damage. All trees are affected by salt to some degree, but some species are more tolerant than others. A listing of the susceptible and resistant trees to salt (University of Tennessee Extension publication SP-610) appears below.
3. In future plantings, avoid setting salt susceptible tree species in areas where salt-laden brine and slush are likely to accumulate.
4. Plants that are injured and exhibit dieback should be watered, pruned and fertilized.
Fresh mulch may be applied to help reduce water loss during the normally dry summer ahead. Weakened or stressed trees are also more susceptible to disease and insect pests.

Table 1. Salt Susceptibility of Trees
Vulnerable to Salt
Red Maple - Acer rubrum
Sugar Maple - Acer saccharum
Mimosa - Albizia julibrissin
Serviceberry - Amelanchier spp.
American Hornbeam - Carpinus caroliniana
Dogwood - Cornus florida
Hawthorn - Crataegus spp.
American Beech - Fagus grandifolia
Yellow Poplar - Liriodendron tulipifera
Crapemyrtle - Lagerstroemia spp.
Magnolia - Magnolia grandiflora
Spruces (most) - Picea spp.
Eastern White Pine - Pinus strobus
Scotch pine - Pinus sylvestris
Lindens - Tilia spp.
Eastern Hemlock - Tsuga canadensis

More Tolerant to Salt
Norway Maple - Acer platanoides
Buckeyes - Aesculus spp.
Birch - Betula spp.
Hickories - Carya spp.
Ash - Fraxinus spp.
Ginkgo- Ginkgo biloba
Honeylocust - Gleditsia triacanthos
Black Walnut - Juglans nigra
Eastern Redcedar - Juniperus virginiana
Cottonwood/Aspens - Populus spp.
Cherries - Prunus spp.
Oaks (most) - Quercus spp.
Black Locust - Robinia pseudoacacia
Yews - Taxus spp.
Elms - Ulmus spp.

Big Begonias

The Benary 'Big Begonia' series are a hit, "begonias on steroids", some gardeners may say. Individual flowers are twice that of other bedding begonias. Colors are vivid with three cultivars currently available . 'Big Rose Bronze Leaf' is my personal favorite. (pictured)

Begonias grow best in well drained, humus-rich garden soil. Provide tender -loving care for the first 4 weeks in the spring, and plants will bloom non-stop through a long hot, dry summers into the first hard frost autumn.

Plant the Big begonias in full sun or partial sun (a minimum of 5 hours of sun recommended). Disease and insect pests are rarely an issue for these tough, non-stop flowering annuals. Do not plant begonias in the same garden spot more than 3 consecutive years to avoid buildup of soil pathogens.