Extension Educator, Local Food Systems and Small Farms
Extension Educator, Horticulture
July 29, 2009
People are beginning to complain about leaking sap coming from trees. Actually this has been going on for a week or so. What happens is a fine mist of sap coats things beneath a tree. This is actually called "honeydew," which is a secretion of sucking insects such as aphids. What makes matters worse is a fungus begins growing in the honeydew, making it turn black.
There are two ways to deal with the problem. The first way is to spray the entire tree with a product such as malathion or bifenthrin to kill the insects. The second way is to move anything portable from under the tree. If you opt for the first option, you need to make sure you can spray the entire tree. The kind of weather normal for this time of year will increase aphid numbers at a very great rate.
The end effect on the tree isn't all that great as long as adequate moisture is available. This means a shot of water when it stays dry for a week or more. We'll also be coming up on lawn fertilization time in about a month, so the added nutrients will help the trees as well.
July 29, 2009
With the numbers of aphids increasing in gardens, on trees, and in fields, that brings us to a couple of predators that we are familiar with. One is the Asian lady beetle, and the other is the syrphid fly. Both of these increase populations greatly when their food source, in this case aphids, increases.
We are all familiar with the Asian lady beetle. It is actually a beneficial insect since it eats aphids. It is also a nuisance pest when it gets all over the side of your house, or flies around your light over the kitchen table. The vacuum cleaner is the best control in the house, and think twice about treating them outside since they are helping you keep from having black, sticky lawn furniture.
Syrphid fly is a generic name given to an entire group of flies. There are some differences in appearance and color, but the yellow and black color is the major one in our area. The other names for syrphid flies are hover flies or flower flies. They tend to hover around your arms and face when you have been perspiring, and land to lap up the sweat. They are also commonly found on flowers, hence the flower fly name, and do a good job of pollinating.
Syrphid flies are actually beneficial insects. They help pollinate, larvae feed on dead organic matter, and the larvae are predators of aphids. They cannot sting, but their mouthparts can usually be felt when lapping up sweat from sensitive areas. You may feel a slight pinch.
July 29, 2009
July 22, 2009
We have discussed the timing of grub control treatments in past columns. As a reminder, the date would have been early August for annual white grubs. Treatment times for Japanese beetle grubs should probably be late August this year. Knowing when to treat grubs is one thing, and knowing what product to use is another.
Many grub control treatments are combined with fertilizer products, and this is the appropriate time to apply a fall fertilizer treatment. It seems each year provides more "stand alone" treatment options as well. Diazinon used to be the product of choice for many homeowners, but the cancellation of home horticulture uses of the product created confusion in selecting a product. The other wild card was the use of diazinon helped eliminate mole problems (by driving them to the neighbor's yard) since the product killed grubs and reduced earthworm populations. Many of the products currently used do not affect earthworm populations, and on the whole that is a good thing since earthworms greatly benefit lawns. There are now some "soft baits" available for mole control that are effective.
Current recommended products include halofenozide (Mach 2), Heterorhabditis bacteriophora (Cruiser), imidacloprid (Merit), and trichlorfon (Dylox). Many of the chemicals have other brand names in addition to the ones listed in parenthesis. It is also recommended to drench treated areas with a half inch of water within 30 minutes of application, and this is especially important with liquid applications. Application just ahead of a rain is usually best. Granular applications buy a few days of time, but still need to be watered into the root zone where grubs are active. The products with Merit will take three weeks or so to activate. Some reputable sources also list carbaryl (Sevin) granules as an option for grubs from green June bugs and Japanese beetles. Carbaryl does reduce earthworm populations to some degree.
In good growing seasons, it normally takes at least 10 grubs per square foot of lawn area to justify treatment. In less favorable seasons, this number can be reduced to six to eight grubs per square foot. As your gasoline bill for the lawn mower can attest, this has been a good growing season to date.
Consider many factors when selecting a product. These would include combination with fertilizer, effectiveness, species controlled, cost, and the effect on the environment. The Cruiser product is actually a nematode, and would be the most environmentally safe. It also costs about $55 to treat about 3000 square foot of lawn. The other organic product sometimes mentioned for control of the Japanese beetle grubs is milky spore. This product is a bacteria which takes several years to become very effective and can cost around $35 for 2500 square foot of lawn. You can't apply any other controls with milky spore since you need high populations of grubs to increase the bacteria populations to high levels and provide transmission between grubs.
Good luck as you decide your attack plans against grubs. The choices are many, and the attainment of the "perfect" lawn is a goal many strive for. Remember, you can live with some grubs. However, too many can be devastating to a lawn. With Japanese beetle populations at very high levels in many areas, odds are great there will be grubs to battle.
July 14, 2009
Well not a week has passed, and an insect similar in appearance to the Japanese beetle has made its annual appearance. No, you don't have monster Japanese beetles. That insect is the Green June Bug. These beetles are much larger than either June bugs or Japanese beetles. Most people are concerned that they have bumble bees because of the buzzing sound the beetles make when flying.
Green June Bugs are also called fig eaters. This is because they can eat soft fleshed fruits such as grapes, plums, peaches, and apricots. In their larval stage they are a grub, but don't do a lot of turf damage like the normal June bug. They tend to be in high organic matter places such as flower beds, gardens, compost piles, and under shrubs, so the grubs aren't turf pests.
As for control, there is probably none necessary unless you need to protect those soft fleshed fruits. Then you should follow the recommended spray program so you don't cause problems with the fruit later on. The Green June Bug doesn't sting or bite, so you can put them in the nuisance pest category. The main damage they can do is fly into you, and that can hurt. On the bright side, you are probably already protecting things of value from the Japanese beetles, so you may be covered.
July 14, 2009
The cicada killer wasps will return shortly. They are actually considered beneficial insects because they control cicadas and katydids. This wasp gets its common name due to the fact that it hunts and supplies its nest chambers with a cicada, which becomes a food source for the young wasp. Cicada killers are a nuisance pest, especially when nesting in large numbers in a play area or near the house. People get concerned because the cicada killers resemble giant yellowjackets.
Cicada killers are about 2 inches long and black to red, with yellow banded markings on the abdomen. The head and transparent wings are reddish brown. They are not dangerous, but they are intimidating. Cicada killers are solitary wasps, with the female digging a 6- to 10-inch burrow (1/2 inch in diameter) in the ground. A pile of soil typically surrounds the entrance. The female locates and stings a large insect such as a cicada or katydid and then brings it back to the burrow. She places the insect into a chamber and lays an egg on it; sometimes she puts two in a burrow but lays an egg on only one. She then covers the burrow, digs another, and repeats the process. The egg hatches into a grublike, legless larva that consumes the paralyzed insect. Full-grown larvae overwinter in the burrow, pupate in the spring, and emerge as an adult during the summer, usually in July and August.
Cicada killers are unlikely to sting a person. Wasp and bee stingers are modified egg-laying devices (ovipositors), so males are not able to sting. Females may sting if crushed, either by being stepped on with bare feet or grabbed with bare hands.
Cicada killers are more common in areas with bare soil, so mulching, planting ground covers, or putting down sod can reduce problems. Applying permethrin or Sevin (some suggest the Sevin dust gives better control) to the burrowed area should kill females in high traffic areas. Once females are gone, males leave. In home yards, sandboxes can be covered with a tarp when not in use, as this deters the wasps (and also keep cats out). Sand below swings, jungle gyms, or other playground equipment is a popular site for the cicada killer. Raking the sand may discourage the wasps, or you could use mulch instead of the sand. In extreme nuisance situations, treatment of burrowing areas with a pyrethroid insecticide or carbaryl may reduce problems.
July 14, 2009
July 9, 2009
This year has again seen rainfall exceed the norm. Saturated soils can wreak havoc on trees and other plants. 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. This results in less growth, yellow leaves, leaf drop, less fruit, and possible plant death.
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.
July 9, 2009
As grass growth slows, rust will be one of the lawn fungi we are dealing with. Rust appears as an orange or yellowish-orange powder (spores) on grass leaf blades, especially in late summer to early fall when the weather is dry. Rust typically develops on lawns growing very slowly. Overall, the turf may assume a yellow, red, or brown appearance. Close examination will reveal the pustules, which easily rub off on your hand. Rust spores can easily be tracked into homes.
Low fertility (in particular nitrogen) and low water availability slow down turf growth, allowing rust to develop. Seasons with excess rain may have rust outbreaks due to loss of available nitrogen. Cool nights with heavy dew and light, frequent rainfall add to the ideal conditions for rust to develop. Warm, cloudy, humid weather followed by hot, sunny weather also favors rust development on lawns. Kentucky bluegrass, perennial ryegrass, and tall fescue are all affected, depending on cultivars. Rust spreads through air, water, shoes, equipment, and sod. Rust may weaken turfgrasses and make them more susceptible to other problems.
Control rust through sound turf management. Begin by choosing a quality blend of turfgrass seed. Resistance to rust can vary according to the race of the disease present. Maintain lawns through sound watering, mowing, and fertilizing. If you are watering, water early in the day so the grass dries quickly. Manage problem thatch. Increase vigor with an early fall nitrogen application, but don't overdo it. Check soil phosphorus and potassium levels through soil testing. Also assure good airflow over the site and light penetration by pruning trees and shrubs in the area near the lawn.
When rust occurs at this time, improved growth conditions of early fall often get lawns growing more vigorously and the rust fades away. Early September is a key time for fertilization. If conditions are dry, irrigation is also needed to increase the growth rate of the lawn.
Fungicides are rarely suggested on home lawns for rust control. Focus on the listed cultural practices described above.
July 1, 2009
Earwigs have definitely been the insect of the week. They hide in damp places out of the sun during the day, and become more active at night. They do feed on a variety of many things, but are mainly scavengers. Inside the home, they definitely fit into the nuisance pest category.
Here is a link to the U of I fact sheet on earwigs http://ipm.illinois.edu/hyg/insects/earwig/index.html