Extension Educator, Local Food Systems and Small Farms
Extension Educator, Horticulture
April 30, 2008
Cedar apple rust is caused by a fungus that attacks two different groups of trees. The first group is apples and crabapples, and the second is juniper and eastern red cedar. In order to survive, the fungus must "move" from one group of host to the other.
On juniper, or eastern red cedar, small (3/8 to 1 and 3/16 inches in diameter) galls develop throughout the tree on needles and small twigs. When mature, these galls swell considerably and repeatedly produce orange, jello-like horns during rainy spring weather. As spring rains subside, the galls die, which may cause death of the twig from the gall to the tip.
On susceptible crabapples and apples, tiny yellow spots appear on the leaves after infection in the spring. As the spots mature, they become yellow/orange and swollen with a red border, and develop tiny black dots in the center of the lesion. By mid-summer, small cup-like structures with tubes are visible on the undersides of mature leaf lesions. The fungus may also infect fruit and tender twigs of very susceptible crabapple and apple varieties.
The entire life cycle takes about two years, with a year on each host. The apple phase is easily recognized on the leaves and fruit by just about anybody who has grown apples. The teliospore phase on the cedars is quite striking, but is noticed much less frequently. Fungicides in spray programs do a good job of controlling the apple phase, while the cedar phase is best controlled by buying resistant varieties. Some homeowners cut the galls off before they break out into the "orange blob," but the result is the same: you're going to likely lose the tips on those branches.
April 30, 2008
Everyone seems to have been waiting for warmer temperatures and the appointed date to begin broadleaf weed control programs. Well that time will come, believe it or not. For most of the broadleaf products to work, the temperature has to be over 55 degrees. These chemicals do work better when it is warmer and the weeds are actively growing. The first item of business is to know what type of weeds you want to control. This will make a big difference in what product or products you select.
The main products used for broadleaf weed control in lawns are 2,4-D, MCPP, dicamba, a combination of those three products, and triclopyr. Let's start with the triclopyr since it's probably the easiest to discuss. Its place in weed control is for hard to control weeds and woody plants. It also improves control of violets. It can be added to one, or more, other chemicals to provide broad spectrum control. Some blends now contain trichlopyr, so check the label.
2,4-D is the old standby. It is good on carpetweed, chicory, dandelion, lambsquarters, plantains, and wild carrot. MCPP is good on chicory, lambsquarters, and white clover. Dicamba is good on black medic, chickweeds, chicory, dandelion, dock, henbit, knotweed, lambsquarters, pearlwort, purslane, red sorrel, thistles, white clover, wild carrot, and yarrow. The combination of all three products will pick up all of those listed for the individual products, plus a few more such as mallow, speedwell, and wild onion. The combinations are sold under many different trade names so check the active ingredient list for ones you need.
My annual disclaimer for application of these types of products is: "Beware of potential drift from these products." Not only can the spray move under windy conditions while you are spraying, but particularly with dicamba, the products can drift as a vapor for up to two weeks after spraying with hot and humid conditions.
April 28, 2008
Recent cold temperatures have affected many yard and garden plants and may continue to do so for the next month, says David Robson, University of Illinois Extension horticulture educator. For most of Illinois, the average date of the last spring frost is between April 15 and April 25. Yet here we are with still a chance of damaging cold temperatures the last week of April. This is why planting dates between May 1 and May 15 are given. Now, plants that are already in the ground will have to withstand Mother Nature's chill.
Flowering plants generally are the hardest hit, with fruit trees suffering most as the temperatures keep dropping.
On perennials and woody landscape plants, cold temperatures can affect their emerging leaves, adds Martha Smith, U of I Extension horticulture educator. Cold injury shows up first as blackened edges around some leaves. Other leaves may have a twisted or distorted appearance, often confused with weedkiller injury. Cold injury can be seen throughout the entire plant from top to bottom and side to side, as opposed to the more localized chemical injury.
Some leaves may look shredded or in tatters. This can be blamed not just on the cold temperatures, but also on blowing soil particles that destroy the tender emerging tissue.
Robson and Smith give this overview of cold injury and what you can do to protect your plants.
Temperatures right at freezing (32 degrees Fahrenheit) seldom cause as much damage as those that dip below 28 degrees, especially on fruit plants and flowers. Cells freeze at lower temperatures, rupturing the cell walls and causing the plant to collapse. The centers of flowers turn dark brown to black. Once that happens, the flower won't be capable of producing fruit.
Flowers on the outside of the plant and those closest to the ground freeze first. Soil temperatures are not yet sufficiently warm to provide any insulation.
Flower buds are protected more than fully opened flowers and can tolerate colder temperatures. However, once the flower is showing color, cold damage is likely to take place.
The good news is that most fruit trees tend to produce an extraordinary amount of flowers. If half to three-quarters of the flowers are lost due to a cold snap, it is still possible to have a crop.
On the negative side, pollinating insect activity from bees and wasps is reduced at colder temperatures. Bees are seldom active at temperatures below 55 degrees. Flowers may be open, but unless the bees pollinate them, no fruit will develop.
Strawberries in bloom can suffer more than fruit trees. Check the flowers—if the center is dark, the fruit has been hit with a cold spell.
So how can you protect fruit plants from cold night temperatures?
On a strawberry bed, you can lightly cover the flowers with loose straw, or you can cover the planting with bed sheets or light blankets. Carefully lay the cloth material on plants to prevent damaging the tender shoots.
Avoid using plastic because it conducts cold directly to the plant tissue that it touches and provides little or no insulation. If you must use plastic, think along the lines of a greenhouse or a tent. Support the plastic sheeting with braces to keep it off the plants.
Small plants and fruit trees can be covered with several sheets or light blankets during the cold evenings to trap heat from the ground. Just make sure you remove the coverings during the day. If you are able to cover your fruit tree, a 100-watt incandescent light bulb placed in the tree, under the cover, will add a small amount of heat.
Sprinkler irrigation can also be considered. Water freezes at 32 degrees by releasing heat, and water melts at 32 degrees by absorbing heat. At this temperature, both actions are occurring and maintain a 32-degree temperature. To be effective, sprinkling irrigation must be constant throughout the cold period until air temperature rises above 32 degrees. This method does have some risk for fruit trees since ice can build up if temperatures dip below 28 degrees; the added weight may cause branch breakage. Sprinkler irrigation is more practical for strawberries.
Encouraging air circulation prevents the cold from settling. For some areas, you could put a fan outside to have a breeze blow across the plants. Make sure the fan is supported so it doesn't topple over.
Trees and Shrubs
Most of our ornamental plants haven't fully leafed out, or they are just starting to leaf out. Many plants initially produce flowers; cold temperatures can kill the flowers that plants initially produce, resulting in fewer seeds. This seed loss won't cause any noticeable injury to the plant.
Ornamental plants in bloom may turn black and abort the flowers, causing flowers to fall off the plant. However, most shrubs and trees should continue to leaf out.
New growth may be damaged as cells expand and break. The results are brown or black-colored leaves that will drop by early summer.
Most woody plants have secondary and tertiary buds if something happens to the initial growth. If the primary buds are damaged by cold, these buds will take over, and the plant will continue to leaf out.
Nothing can be done to protect mature trees and shrubs. Most of these plants will continue to produce new leaves as temperatures climb; these new leaves will appear typical. Damaged leaves may turn yellow and fall. But in most cases, the damaged leaves will remain on the tree.
Keep in mind that heat rises, while cold settles on the ground. The canopy of trees may be several degrees warmer than the ground, giving the plants a little extra warmth.
Some vegetables including broccoli, cabbage, lettuce, peas and spinach aren't bothered by the cold unless temperatures drop into the low 20s for an extended time. Others plants including tomatoes, peppers, asparagus and rhubarb are more susceptible to the cold.
Vegetable plants may take on a light yellow or purple color because the cold temperatures affect nitrogen and phosphorus uptake. However, as temperatures rise, the typical green color should develop.
Gardeners can cover transplants for the night with a milk jug, a clay flower pot or any type of bucket weighted down with a brick or large stone. Incorporating manures into the vegetable garden before planting helps generate some heat. And, mulching with black plastic can also provide some insulation for the plants.
Rhubarb that is wilted and limp from the cold should not be eaten. Remove those stalks and wait for new growth. If leaves and stems are stiff and erect, the stalks are safe to eat.
Asparagus shoots will become distorted and twisted. But, the spears are safe to eat.
Vegetables that appear sickly from cold injury may never fully recover even if they don't die. It might be better to sacrifice those plants to the compost pile and buy new, healthy ones once the air and soil temperatures start to rise.
Flowers and Ornamentals
Bulbs generally are the only flowers blooming right now, and they can tolerate some freezing temperatures. But, the shoots of other spring flowers can be susceptible to cold injury. The vast array of perennials such as hostas and peonies can be protected with bed sheets or light blankets. Again, remember to remove the covering during the day. Plants in containers can be moved inside a garage or shed for the evening. If you don't have space inside, you can move the containers closer to the house where the ambient heat may keep them a couple degrees warmer than the open.Robson and Smith say that the damage from cold injury depends on how cold it gets, the length of the cold spell, and the type of plants involved. Homeowners who have some prized plants may want to take precautions. Other may decide to take a wait-and-see attitude and watch for damage in the next week or so.
April 21, 2008
Master Gardener Plant SaleThis Saturday the annual Master Gardener Plant Sale will make its annual appearance. The sale will be from 9 to noon in the Fair Exhibition Building. Enter the fairgrounds through the south gate by the caretaker's trailer. I know they have been busy this year with several varieties of daylilies, rhubarb, hostas, geraniums, and many more. The group does the annual sale as a fundraiser for their many activities, and to help beautify the community.
April 21, 2008
April 21, 2008
Early in the spring, there are many pest that become active. Many of these are timed by the saucer magnolia blooms, according to Orton's "Coincide" book. The past couple of weeks, when the magnolia blooms were in the pink-bud stage, spruce spider mites became active. These mites are one of the major downfalls of spruce in our area.
The spruce spider mite, along with other spider mites that attack evergreens, are active in the spring and fall. This is opposite of the two spotted spider mite that is active during the heat of the summer. Heavily attacked trees often lose branches, and can even be killed. Even the loss of branches can render an evergreen worthless in the landscape.
To determine if you have spruce spider mites, hold a piece of white paper under a branch and shake it. The mites will look like moving dust specks on the paper. They will also leave a green streak if rubbed on the paper, and that's a good way to distinguish them from dust or plant material. If mites leave a red streak, they are predatory mites. These predatory mites eat the bad mites, so high numbers will control your problem. Many times, there will be some fine webbing, like spider web, visible on the needles as well.
Spruce spider mites can be controlled with sprays of acequinocyl, bifenthrin, cyfluthrin, insecticidal soap, or summer oil spray. The soap or oil sprays will require a second application about a week later to give good control. These mites normally remain active until mid-May, but the cool conditions thus far may extend their life cycle this year.
Other spring pests are also indicated by the saucer magnolia. During the bloom stage, going on now, the ash plant bug, fall cankerworm, spring cankerworm, Fletcher scale, leaf crumpler, eastern tent caterpillar, juniper webworm, and Zimmerman pine moth are susceptible to control. As we get to the petal fall stage, European pine sawfly, Gypsy moth, hawthorn mealybug, honeylocust pod gall, and willow aphid become susceptible to control.
Some plants are great indicators of insects. The plants and insects develop at the same temperatures. It just took somebody like Mr. Orton to put it all in print.
April 16, 2008
This time of year we are getting quite a few questions about certain lawn weeds. The questions are generally related to identification and then what to use to get rid of the stuff.
Each year, these winter annual weeds run number one and two in the early spring. This year is seems like chickweed is running slightly ahead. Winter annual weeds can actually germinate in the fall, carry through the winter, then get going very early in the spring. They also are done by the heat of the summer, leaving seed to germinate again later in the fall. Right now chickweed stands out in yards because it is quite abundant, and has a lighter green color than grass and most other weeds. I can't begin to tell you how to identify it, it gets even harder when there is common chickweed and mouse-ear chickweed. Henbit is easier to identify since it has purple flowers and smells like mint. As for control, that gets a bit easier.The straight 2,4-D that is used on dandelions seems to act like a fertilizer for chickweed and other problem weeds. Combinations that contain 2,4-D, MCPP, and dicamba are rated very effective on chickweed, henbit, red sorrel, purslane, white clover, and others. These combinations are sold under several different trade names. You can find these at most hardware, discount, and lawn and garden stores. Just check the label under active ingredients and check for two long chemical names and dicamba. You can also check to see that it says it will control chickweed and henbit. This group of chemicals is effective in the 50 degree range and up. As with any chemical control, read and follow label instructions very carefully. There will be some cautions on these product labels concerning injury to sensitive plants that you should be aware of. This is because dicamba can drift as a vapor for a few weeks after you apply it if the weather gets hot and sunny.
April 16, 2008
Many have been asking about the Master Gardener Plant Sale for this year. The group has been busy working to prepare for the plant sale. This year's date is Saturday, April 26, and the sale will be from 9am to noon (or sell out) in the Exhibition Building at the Fairgrounds. They plan to have perennials, annuals, houseplants, vegetables, and a few shrubs.
April 16, 2008
Nuisance Tree Fruit Removal
Nuisance fruit removal is a term used for removing sweet gum balls, maple seeds, and crabapples. It really applies to fruit that is a nuisance.
There are several products available to eliminate nuisance fruit. The most common is ethephon, and it is used as a foliar spray to reduce or eliminate undesirable fruit or seeds. Some of the trade names include Florel and Ethrel. The product is effective at eliminating much of the fruit without affecting leaf growth and color, and it does not harm other plants that get some spray drift on them. It also does not affect the actual flowering of the treated trees.
With ethephon, the key is in the timing. The application must be made during flowering, but before the fruit set in. For most flowering trees there is a 10-14 day window of opportunity. Sweet gums are a little tricky since there are no showy flowers involved, so effective sprays should occur just as new leaves begin to emerge. Sprays should leave leaves wet, but not to the point of dripping. Good coverage of the tree is needed, so keep in mind the size of the tree when you are weighing this option.
This product is a growth regulator that naturally occurs. Its natural production is stimulated by stress, so make sure you aren't treating a tree that is under stress from drought, high temperatures, diseases, or other environmental stresses. Treating stressed trees can cause severe injury to the plant such as leaf loss or scorching.
There are also injection products available (mainly through commercial applicators), but the cost is considerably more. The other side of the coin with some of the injection products is that they may not remove as much of the nuisance fruit. In the end, weigh your options and decide what may work best for you.
April 8, 2008
Also with some warmer weather comes the swarms of insects that raise that perennial question of "Are they ants or termites?" Swarming time for both insects is about the same time, and they are really looking to start new colonies because they have outgrown their old ones. This is the reason for the winged insects, the wings allow the ants or termites to cover larger areas to start their new colonies. The differences between ants and termites are several.
Let's start with the body color. Termites are always blackish in color, while ants may be black or other colors. If you have winged insects that are not black, you don't have termites.
Next, look at the body shape. Ants have a constricted "waist" while termites don't have that classic hour-glass figure. Antennae and wings are the other two body parts to look at. Antennae on ants are elbowed, basically in an "L" shape, and those on termites are straight. Both ants and termites have pairs of wings, but termite wings on the same side will be of equal length, while ant wings are of different lengths on the same side.
April 8, 2008
A common home invader this past week has been the millipede. Millipedes are hard shelled animals that are worm-like with many segments. They also curl up when disturbed. Most body segments have 2 pair of legs, except for the 3 behind the head. Adults are 1-2 inches long and can be brown, tan, or gray.
Most millipedes are scavengers. They feed on decaying organic matter such as leaves, compost, and grass clippings. They may sometimes injure small, young plants by feeding on the roots and tender plant parts, but this is rather rare.
When they enter the home in large numbers, they can become quite a nuisance. They do not bite, feed on clothing, or cause any real damage. They are simply a nuisance. Control of millipedes in the house is best accomplished by running the vacuum cleaner.
Most insecticides are not very effective against millipedes. The best way to prevent them from entering the home is to remove and discard accumulations of leaves, rocks, boards, and other trash from around the foundation of the house. Also, keep shrubbery and flower beds free of leaf mulch during the warm months.
Foundation sprays of permethrin or bifenthrin may have some effectiveness, but they may not provide satisfactory control. To apply these sprays, spray the foundation of the house and the adjacent foot of soil. In severe cases, you may need to expand the soil treatment area (and maybe spray the entire yard).
April 8, 2008
Pest Season Comes Again
With the warmer weather, we're becoming more active. There are also many nuisance pests becoming more active as the temperature climbs, and we destroy their resting places by cleaning off flower beds and raking up piles of leaves. Let's start with the Asian ladybugs. Right now they are alternating between resting and sunning. These are the beetles that overwintered as adults, and are looking for a place to stay and something to eat. The place to stay is on the side of something in the sun (in order to warm up), and the something to eat is soft bodied insects such as aphids. Without aphids present, these ladybugs will chew on about anything.The best control in the home is a vacuum cleaner. If you have numbers too large for that control, area sprays of an aerosol flying insect killer will knock down the ones it hits. If you are terribly bothered, try a perimeter spray of the foundation, door areas, and window areas on the home with a pesticide that will last for a while. Color test the material on siding first, and hope for the best. The pesticides are effective, but they are sometimes overwhelmed by the number of ladybugs that you are trying to control. Permethrin and bifenthrin are probably the most commonly used pesticides for perimeter sprays.