Hort Update for the week of 4/13/07

Current Problems:	Major Symptom:
1. Freeze Damage	Dead & dry, brown or black leaves, flowers and buds.
Lawns
2. Field Speedwell	Low growing weed with small blue flowers.
3. Henbit	Square stemmed weed with purplish pink blooms.
4. Ground Ivy	Square stemmed weed with scalloped leaves.
Trees & Shrubs
5. Dothistroma needle blight	Needle browning in lower half of Austrian pines
6. Black knot on plum	Black woody mass encircling the stems of plums, cherries & almonds
7. Ash flower gall	Hard, blackish galls in seedless ash trees.
8. Bagworms	1.5 to 2.5” long brown bags attached to evergreens.
9. Zimmerman pine moth	Branch breakage in pine trees.
Miscellaneous
10. Red clover mites	Red specks (mites) crawling on windows and furniture.

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1. Freeze Damage- Wait and see the extent of damage, give plants a change to recover, and allow new growth to begin before taking action.

Trees & Shrubs-Leaf & Bud Damage If they were flowering or flower buds were showing color at the time of freezing temperatures– damage is likely. The extent of bud development at the time of freeze injury will determine the amount of damage. If they had begun to leaf or leaf buds were showing color – these were likely damaged. What to watch for? Damaged leaves may at first appear water-soaked, and may be darker in color. Within a few days the leaves will dry up, although they often retain their green color for several days. As partially damaged leaves open, browning or leaf tatter from wind blowing out freeze damaged areas may be seen. Freeze damage may appear to homeowners as insect or disease injury. Pesticides should not be applied to "control" the injury. Otherwise healthy and hardy trees and shrubs will develop secondary buds and releaf. Leafing may be delayed and stored food reserves used by the plant. If a terminal bud is damaged, some “odd growth” might be seen down the road. Managing damage plants: Avoid unnecessary pruning at this time so damaged plants do not have to use energy reserves into sealing pruning wounds as well as secondary bud development. Avoid fertilization so additional growth is not forced and additional food reserves used. Follow best management practices, including watering and mulching, and control pests as needed during the summer to avoid additional stresses. Bark Damage- Mark Harrel, Nebraska Forest Service Pest Specialist, is not expecting much damage to the bark/cambium layer. However, if there is damage it will not show up until later in the season. Plant Death- If a tree or shrub dies, it was probably not fully hardy to our area or had other “issues” that had greatly lowered the plant's food reserves. The freeze was “the straw that broke the camel’s back”.

Lawns- Information from Roch Gaussoin, UNL Turfgrass Specialist Kentucky bluegrass has the ability to “recover” rapidly when damage occurs. There may be some leaf tip burning. This can be mowed off, and is most likely to have occurred on lawns which had already been fertilized and had lush succulent growth with plant cells full of water. The ideal time to apply the first spring fertilization is April 20 to May 5. Lawns which had been “mowed low” (scalped) may have had exposed crowns. This, along with a thin stand of grass, may lead to some crown damage. New lawns seeded last fall are susceptible to damage due to low density, unestablished crowns with little stored carbohydrates. Lawns sodded last fall should be fine.

Herbaceous Perennials The extent of damage depends on individual plants and their hardiness zone, landscape microclimate conditions, the level of plant establishment and maintenance care by homeowners. Leave damaged foliage in place for now to act as protection against additional freeze/frost damage. As warmer weather returns, new growth begins, remove damaged growth. Give plants time to recover before digging up and replacing. Homeowners should leave winter mulch on plants as late in spring as possible (until new growth begins) to minimize damage from early spring freezes.

Fruit Trees & Small Fruits If the flower buds had begun to swell, damage likely occurred. Fruit crop yields will be affected. Strawberries: The first flower bud is called the primary bud or king berry. If it was damaged, secondary buds will develop, but fruit from these are not as large. Rhubarb: Rhubarb hit by a hard frost or freeze in late spring can still be eaten as long as the stalks are firm and upright. If the stems are soft and mushy, don’t eat them. Cut the damaged stalks off to allow new stalks to develop for eating.

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2. Field Speedwell- Veronica agrestis. Low growing plants with tiny, scalloped edged leaves and small blue flowers with white throats. Tiny seed pods are heart-shaped. Stems are round, not square. This is a winter annual which germinates and begins growth during fall and completes its life cycle by blooming and seeding in early spring. Apply pre-emergent herbicides in September for effective control. Since it is going to seed now, post-emergent herbicides are not very effective. Combination herbicides with a 2,4-D base can be applied or try hand-pulling.

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3. Henbit- Lamium amplexicaule. Henbit is in the mint family so has square stems. Leaf edges are scalloped and leaves clasp the stem near the purplish pink flowers. A winter annual and so control is the same as for speedwell. Thin lawns are unable to compete well with winter annuals. Follow best management practices for turfgrass to increase a turf’s ability to compete with weeds.

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4. Ground Ivy (aka Creeping Charlie)- Glechoma hederacea. This weed is also in the mint family so has square stems. Leaves similar to henbit however leaves have petioles (unlike henbit). These weeds are perennials and will not soon die. They can be treated now with a combination herbicide; however, fall herbicide applications, in mid to late October, are most effective.

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5. Dothistroma Needle Blight- Browning of needles in the lower half of Austrian pine trees. On close inspection, needles will have turned brown from the tip down to a reddish-purple lesion or spot on the needle. These lesions can be found on other green needles as well.

Internet Resource- http://www.na.fs.fed.us/spfo/pubs/fidls/dothistroma/doth.htm

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6. Black knot - a black fungal mass in a hard knot wrapped around stems. Affects plants in the Prunus genus, including plums, cherries, almonds. Prune out the galls, going back at least 2-4" below each knot, or into healthy tissue. Lime sulfur applications in spring, combine with pruning, is the best control method. The knot takes 2 years to show up. The first season there is a canker, the 2nd year the black mass develops.

Internet Resource- http://ohioline.osu.edu/hyg-fact/3000/3011.html

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7. Ash Flower Gall- Appears as clusters of black galls on seedless (male) ash trees from last year. They are unsightly but not harmful to the tree. They are caused by the ash flower gall mite that attacks the male flowers, causing them to become deformed. Later this spring, it is likely new galls will form. Initially, they are small and green.

Internet Resource- http://www.oznet.k-state.edu/dp_hfrr/extensn/problems/Ash_Flower_Gall.htm

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8. Bagworms- Tightly woven brown bags 1.5 to 2.5 inches long and covered with brown needles. Most often found on evergreens. Right now the only treatment is pulling or clipping off the bags and destroying them. The next generation of bagworms will hatch out in June and this is the time to control them with insecticides.

Internet Resources- http://ohioline.osu.edu/hyg-fact/2000/2149.html

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9. Zimmerman Pine Moth - The larvae of this moth overwinters as a young caterpillar under bark scales. In April they begin feeding again and eventually bore into the wood around the base of branches. Masses of creamy or pinkish pitch at the junction of main branches and the tree's trunk indicate the presence of this insect. However, damage is often first noticed when branches break from wind or snow. Mid-April to early May is the usual time to treat. Most insects will become active when air temperatures are in the 40's F.

Internet Resource-http://www.ext.colostate.edu/PUBS/insect/05591.html

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10. Red Clover Mites- These small mites are often found on west and south facing windows and walls in the spring. These mites overwintered under siding and window frames. When temperatures warm up the mites become active. A wet washcloth or paper towel will control the pests on windows and walls. These nuisance mites do no damage to people, pets, or the house structure. Insecticides are not recommended for use indoors. An outdoor perimeter spray applied in the fall will help keep the mites from entering the home.

Internet Resource- http://ohioline.osu.edu/hyg-fact/2000/2095.html