July 15, 2008

Water Damage

Most of Illinois has experienced excessive rains, which have resulted in waterlogged soils and flooding. Logan County has certainly been no exception, with another round of four inches or more common. It is important to understand what is happening to plants growing in these conditions, and what to expect later. It is a wait-and-see situation. Many herbaceous plants are experiencing injury symptoms now. Visible injury symptoms on trees and shrubs may not occur for a year or more. Following is a discussion about flooded and water soaked plants, based on an article done by Rhonda Ferree several years ago.

Injury symptoms, which vary according to several factors, include decreased growth of shoots and roots, decreased transpiration rate, yellowing leaves, twisting of leaves, leaf drop, death of roots, increased susceptibility to attack by predators and pathogens, absence of fruiting, and death.

The main reason injury occurs is related to oxygen availability in the soil. In flooded or waterlogged soils, oxygen diffuses slowly and reduces in concentration to a few percent or zero. As oxygen is excluded from roots, there is decreased aerobic root respiration, root growth, transpiration, and translocation.

Although survival is directly related to species' tolerance of waterlogged soils, other factors are important—including the soil type; the time, duration, and depth of the water; the state of the floodwater; and the age and size of woody plants.

Tolerant species, such as baldcypress, littleleaf linden, redtwig dogwood, mulberry, silver maple, and willow, can live on sites in which the soil is saturated for indefinite periods during the growing season.

Moderately tolerant species, such as green ash, hawthorns, honey locust, pin oak, red maple, river birch, sweetgum, and sycamore, can stand saturated soil for a few weeks to several months during the growing season, but these species die if waterlogging persists or reoccurs for several consecutive years.

Weakly tolerant species, such as American holly, balsam fir, black walnut, burr oak, catalpa, hackberry, Douglas fir, eastern cottonwood, and red oak, can stand relatively short periods of soil saturation—a few days to a few weeks—during the growing season, but they die if waterlogging persists for longer periods.

Intolerant species, such as American beech, black locust, crabapples, eastern hemlock, flowering dogwood, paper birch, pines, redbud, spruces, sugar maple, tuliptree, white oak, and yews, die if they are subjected to short periods of 1 or 2 weeks of soil saturation during the growing season. White pines and burning bushes are among the most sensitive, with saturation for as little as two days can cause root death, followed by plant death.

Unfortunately, little can be done to prevent damage to plants growing in waterlogged soils. If a woody plant shows injury symptoms, such as leaf drop, do not immediately replace it. Some plants will show initial injury symptoms and then recover. Many woody and herbaceous plants, including turf areas, will not recover. Be patient. Whether your plants are simply waterlogged or actually growing in flood areas, it will take a while to see the full extent of plant damage.

Posted by John Fulton at 9:25 AM | Permalink |

July 9, 2008

Tomato Diseases

It seems like the tomato is the one plant that just about everybody tries to grow. Some people grow large amounts, while others plant one or two in containers. At any rate, the calls and samples have started coming in to the office already. Most of the samples have spots, brown leaves, and dropping leaves, or all of the above. Several diseases hit tomatoes, but two of the more common ones are early blight and seporia leaf spot. Blossom end rot seems to have been running rampant on early tomatoes as well.

Early blight, also know as Alternaria leaf spot, can affect plants at any stage of development. All above ground parts are susceptible. The most characteristic symptom of early blight are spreading spots, ¼ to ½ inch in diameter that form on lower or older leaves. These spots have dark edges and they are usually brown to black in the center. These spots frequently merge forming irregular blotches. Concentric rings often form creating a 'target' or 'bulls-eye' effect. Affected leaves develop yellow areas around the lesions. Spotted leaves soon turn yellow, whither and drop off. The fungus may cause lesions on the fruit around the stem end and shoulder. The lesion is usually dark brown to black, up to an inch in diameter, and with distinct concentric rings.

Septoria leaf spot can also affect plants at any stage of development. Numerous small, water-soaked spots first appear on the lower leaves. These spots soon become circular to angular with dark margins and grayish centers often bearing one or more tiny black bodies called pycnidia which are spore-bearing structures. Individual lesions are seldom more than ⅛ inch in diameter and are usually quite numerous on an infected leaf. Heavily diseased leaves turn yellow, wither and drop off in large numbers, starting at the base of the plant. Defoliation can be severe during prolonged periods of warm, wet weather.

As for what to do, here is the checklist: First, keep ripe fruits picked off the plants. Second, don't work around tomatoes when they are wet. Next, you can try and improve air circulation, but if your tomatoes are severely affected you won't want to lose any more leaves. And the final step for this year is to try a fungicide. Mancozeb is probably the recommended one, but it is very hard to find. The other options are Daconil and maneb, which are easier to find but probably won't give you as good of control. The final step for future years is to practice at least a three year rotation, with good sanitation in the garden.

Blossom end rot is a non-pathogenic disease that is very common during extended dry periods. It begins as light tan water-soaked lesion on the blossom end of the fruit. The lesions enlarge and turn black and leathery. This can drastically lower the yield and lower marketability of the fruits. Fluctuating soil moisture supply during the dry periods, and low calcium levels in the fruit are the major causal factors. Control of blossom end rot consists of providing adequate moisture from fruit formation to maturity, and use of mulch (grass clippings, plastic, straw, shredded newspapers, or plastic) to conserve moisture. Avoid frequent shallow watering. Water deep and then wait five or more days before watering again. Proper mulching increases the number of days between watering, and evens out the moisture supply.

Posted by John Fulton at 2:19 PM | Permalink |

June 30, 2008

Japanese Beetles

Everyone who thought we had escaped the Japanese beetle attack this year may have to rethink that. The beetles are running a week or two behind schedule, due to the cool spring. A few beetles have shown up in the area. Whether these are local hatches or tag-a-longs from southern areas doesn't much matter. They are coming.

Japanese beetle adults have a 1/2 to 3/4 inch long body with copper colored wing covers and a shiny metallic green head. A key characteristic is prominent white tufts of hair along their sides. They also have an overwhelming appetite for your favorite rose. Adults feed in herds on many deciduous trees, shrubs and vines such as linden, Japanese maple, sycamore, birch, elm, and grape. They generally do not feed on dogwood, forsythia, holly and lilac. Japanese beetle adults feed on flowers and fruits and skeletonize leaves by eating the leaf tissue between the veins. Feeding is normally in the upper portions of trees. Beetles prefer plants in direct sun, so heavily wooded areas are rarely attacked.

Adults can be with us until mid August. The life cycle is similar to a June bug, only it runs a few weeks later. After mating females lay eggs in turf which hatch into grubs in August. Grubs feed on plant roots until cold weather drives them deeper into the soil. Adults emerge in summer of the following year.

The bacterial control, milky spore sold as Doom or Grub Attack, is frequently recommended to control Japanese beetle grubs. In our area milky spore is generally not recommended, since it controls only Japanese beetle grubs and not our predominate lawn grub, the annual white grub. Also Japanese beetle grubs must already be infesting the turf for milky spore to work effectively. Pesticides commonly used for lawn grub control will also control Japanese beetle grubs.

Controlling Japanese beetle grubs does not significantly reduce the number of adult beetles the following year. The beetles are good fliers and easily fly a couple miles in a single flight. Evidence suggests that adult beetles are attracted to previously damaged leaves. Therefore reducing feeding damage now can result in less feeding damage in the future.

Generally pesticide sprays of cabaryl sold as Sevin can reduce damage for up to two weeks, but four to seven days is more likely. Sevin is toxic to bees. Synthetic pyrethroids can also be effective, but tend to break down quickly with extreme heat. These would include permethrin and bifenthrin. The Japanese beetle repellent made from Neem has not been shown to be effective. Picking beetles off by hand every couple of days may be just as effective as spraying. When disturbed, the beetles fold their legs and drop to the ground. Covering plants with floating row covers can protect prized roses and ripening fruit. Japanese beetle traps are not recommended since they can actually increase damage by attracting more than they kill.

A number of birds such as grackles, cardinals and meadowlarks feed on adult beetles. Two native predator insects and a couple of introduced parasites may help to keep Japanese beetle populations in check. Protect natural enemies by keeping the use of conventional pesticides to a minimum. Although damage looks devastating, Japanese beetle feeding rarely kills plants. Therefore, confine control of beetles to shrubs and small trees near main building entrances and other important landscape locations where damage is obvious. Protecting a prize rose bush, or a newly transplanted linden tree is a good idea.

Posted by John Fulton at 3:08 PM | Permalink |

June 30, 2008

Potato Leafhopper

In keeping with the insect theme, potato leafhopper numbers have exploded this last week. This is the small wedge-shaped, light green insect that seems to just fog around security and patio lights. They are not only a nuisance, but they can cause damage to a wide variety of plants.

Potatoes are the first plant that comes to mind when we talk about potato leafhoppers (must be something about the name), but many other plants ranging from beans to trees can be affected. You may be wondering what kind of damage a few little leafhoppers can do, especially since they suck sap from plants and aren't that big in size.

Leafhoppers suck sap and then inject a toxin back into the plant. Along the same lines as humans getting a mosquito bite - it's the extra that's injected back in that causes the injury. Symptoms of leafhopper damage start as yellow "v" shaped areas on the tips of leaves. These areas turn brown or black and then fall out leaving a "v" shaped hole on the tip of the leaf. This is a symptom, but not the only injury. Large numbers of leafhoppers can kill potato and other plants.

Controls for leafhoppers are warranted with very low numbers. In alfalfa fields, it is recommended to treat when 2 leafhoppers are caught in a sweep net in alfalfa over a foot tall. Garden treatment options for potatoes include: Sevin and rotenone as common insecticide choices available to homeowners. Most trees and shrubs can be treated with Sevin, permethrin, or bifenthrin.

Posted by John Fulton at 3:06 PM | Permalink |

June 26, 2008

Anthracnose Continues

A lot has happened in a week with our trees. The maples continue to show increasing leaf drop. Sycamores have been hit with a vengeance, and leaves have been falling like rain for the last week. Other good quality hardwoods, such as ash, are also showing symptoms.

The symptoms are dead material between the leaf veins, along the leaf edges, or dead tips of leaves. There are also times when the disease affects buds and twigs. In the leaf stage, the disease only affects leaves currently out. If damage to leaves results in enough dropped leaves, the tree will shoot another set within four to six weeks. All we're out is the energy the tree spent in pushing out another set of leaves. Of course, we also had a freeze that caused the loss of leaves on many trees. What I'm getting at is trees have spent quite a bit of energy already this year. We need to do what we can to replace nutrients and keep moisture available.

Moisture will be needed to with keep those affected trees in a vigorous growing condition. Usual watering rates are an inch a week, and rainfall can supply part or all of that. Fertilizer applied to lawn area or trees is the other part of the equation. Fertilizer should be applied at the lawn rate (supply one pound each of nitrogen, phosphorus, and potassium per 1000 square foot of drip area), if you haven't fertilized the lawn area around the trees. This would translate to about 10 pounds of 10-10-10 fertilizer or eight pounds of 12-12-12 or 13-13-13 per 1000 square feet.

Posted by John Fulton at 9:10 AM | Permalink |

June 26, 2008

Oystershell Scale

It is time to take action against the notorious oystershell scale, because the eggs are now hatching into young crawlers that are extremely susceptible to insecticide applications. However, as the scales mature later in the season, they are more difficult to control because they form an impenetrable protective covering. Oystershell scale has a wide host range, including ash, birch, dogwood, elm, hemlock, maple, poplar, privet, walnut, and willow.

Eggs hatch into young, creamy white to brown crawlers that are active from May through June. The crawlers locate a place to settle and then use their piercing–sucking mouthparts to remove plant fluids, which causes leaf yellowing, plant stunting, and possibly death. Branches or twigs totally encrusted with oystershell scale eventually die.

Posted by John Fulton at 9:09 AM | Permalink |

June 26, 2008

Gardening Reminders

Posted by John Fulton at 9:07 AM | Permalink |

June 16, 2008

Garden Walk

The Logan County Master Gardeners will present their "Thru the Garden Gate" garden walk this Saturday, June 21 from 9:00 a.m. until 3:00 p.m. Six area gardens will be featured on the walk this year. Tickets are $8 in advance or $10 at the gardens. Advance tickets are available at the Logan County Extension Office, Graue, Inc., Lincoln Antique and Furniture, or any Logan County Master Gardener.

Posted by John Fulton at 11:04 AM | Permalink |

June 16, 2008

Soldier Beetles

For those of us with linden trees, that are now pollinating, we probably have seen the soldier beetles. They look like pale lightning bugs, without the light. Following is some in-depth information on the beetles to give us a little clearer picture of what they do.

Soldier beetles, also known as leatherwings, get their name from the soft, cloth-like wing covers, which when brightly colored are reminiscent of uniforms. These beetles are elongate, soft-bodied and about 1/2 inch long. Colors of soldier beetles vary from yellow to red with brown or black wings or trim. A common and easily-spotted species is the Pennsylvania leatherwing, which is yellow with one large black spot on each wing.

Soldier beetles resemble lightning bugs but do not have light-producing organs. Another group of beetles that may be confused with soldier beetles are the blister beetles, which are pests, but blister beetles have a square-shaped head and a very visible "neck."

Adult females lay their eggs in clusters in the soil. The larvae are velvety, covered with dense bristles, and have antenna-like projections on their head. Most larvae are carnivorous, feeding on insects in the soil. Larvae overwinter in damp soil and debris or loose bark. The adults are also predators, eating caterpillars, eggs, aphids, and other soft-bodied insects. They will alternatively eat nectar and pollen if no insects are around. They do not damage plant foliage. Adults are often found on flowers such as goldenrod, where they lie in wait for prey, feed on pollen and mate.

Posted by John Fulton at 10:46 AM | Permalink |

June 16, 2008

The "To Do" List

Young bagworms are present at this time. Spray after eggs have all hatched (guessing this week) to control them. Sevin, Thuricide, or one of the pyrethroids will work.

Pruning evergreens is done about the end of June. This applies to both broadleaf and traditional evergreens. Pine, juniper, yew, arborvitae, spruce, holly, rhododendron, azalea, and other evergreens should all be pruned around the end of June. This keeps new growth from getting too rank this growing season, but still allows new growth that does occur to harden off before the cold month this fall and winter. Pruning can be done for shaping or size containment.

Check tomato plants for signs of septoria leaf blight. If you see brown areas between the veins and along tips of leaves, especially on the lower leaves, you may want to start a fungicide spray program. This is the disease that has caused leaves to drop off of plants the last couple of years, and it is present very early again this year. Fungicides such as mancozeb, maneb, or Daconil will have provide some control of the fungus.

Also on tomato plants, if you haven't mulched them yet you may want to do so. The mulch evens out soil temperature and moisture. This is a great assistance when preventing blossom end rot on the fruits as they begin to form. You may use straw, grass clippings, or any commercial mulch material. Apply about four inches deep and hopefully this will help prevent those leathery bottom tomatoes.

Keep spraying, or dusting, cucurbits and potatoes. Different things on each, but the potato leaf hopper populations have increased, and the beetles that transmit the wilts on cucurbits are present. Sevin and bifenthrin are the mainstays for these programs.

Japanese beetles will soon be emerging. Protect your favorite roses or apple tree with a cover spray of permethrin, bifenthrin, or Sevin liquid.

Posted by John Fulton at 10:45 AM | Permalink |