Extension Educator, Local Food Systems and Small Farms
Extension Educator, Horticulture
July 29, 2010
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 and lace bugs. 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, bifenthrin, or permethrin, 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 predicted 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 that fertilizer will help the trees as well.
July 29, 2010
As we enter August, we usually don't think of fall - at least not quite yet. However, a quick trip through Southern Illinois this weekend showed the heat of the season has caused insects to develop faster than usual. The fall webworms are out in force, and they are one of the more visible fall defoliators.
Let's begin by listing some of the culprits. Fall webworms, Eastern tent caterpillars, Tussock moth larvae, Walnut caterpillars, Cecropia moth larvae, and a host of others are all considered fall defoliators. What is defoliation? It is simply removing the leaves from a plant. This group of insects accomplishes the feat by eating leaves.
What does fall defoliation do to a tree or shrub? It does two things. First is removes the leaf tissue so that less food is made for the plant. Second, the insects, their webs, or their damage can be unsightly. In the end, damage happening to a tree or shrub in mid-August is usually cosmetic. Unless you have new transplants or plants that aren't healthy to begin with.
Most fall defoliators come to us as the larval stage (read caterpillar) of a moth. When we talk about controls of the larvae, the fact that they are larvae of moths or butterflies makes them susceptible to the use of B.t. products such as Thuricide. Other control options include the standbys such as Sevin, Othene, malathion, bifenthrin, permethrin, and others.
The way that insects live also dictates some of the control do's and don'ts. Fall webworms live inside a "web" all the time. They actually expand the webbing as they need to have more leaves to eat. They are usually worst on fruit and nut trees. You can even clip the nest (and the branch it is around) off the tree and burn it. I guess this tells you that defoliation caused by the insect isn't that great of a threat to the tree or you wouldn't cut the branch area off. If you want to spray fall webworms, you need to get the spray through the web. This may be a little harder than you think. If you don't have enough pressure, the spray just runs off the webbing.
In the case of Eastern tent caterpillars, they hatch out of a common nest. They then leave the nest to feed, but generally return in the evening to congregate in the area of the nest. They are not covered by webbing, and the time they are congregated is a great time to spray since they are usually in one area on the trunk or main branches of trees.
In summary, control of fall defoliators isn't usually justified from the plant's standpoint. Forested areas have heavy pressure from this group in insects every year, and the trees are still thriving. The exception is newly transplanted or struggling plants. If appearances are important, consider a control spray.
July 29, 2010
July 22, 2010
Questions are beginning to come in regarding grub control. As a reminder, the date should be 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 22, 2010
The population of syrphid flies swelled enormously this past week. 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 15, 2010
A new training program for Master Gardener trainees will be offered in Lincoln at the U of I Extension Office beginning on September 22 and concluding December 1, with no class the week of Thanksgiving. The classes will be held weekly on Wednesdays from 9:00 a.m. until approximately 4:00 p.m. Cost for the training will be $100 per person for those volunteering time through the Logan County group, with supplemental funding of approximately $50 per person being sponsored by the Logan County Master Gardeners. Non-compliance with the volunteer service requirement will result in a bill to recoup the actual cost of the training. The cost to those from other Master Gardener programs will be $150.
Participants completing all ten sessions will then be considered interns with the expectation of 60 hours of volunteer service be completed within program guidelines within the next two years. After the internship, the expectation is 30 hours of volunteer service and 10 hours of in-service education minimums. If you are interested in joining, Don Miller in the Logan County Extension Office will serve as the coordinator. His contact information is firstname.lastname@example.org or (217)732-8289.
July 15, 2010
As predicted earlier in the season, fungi have really kicked in on shade trees and ornamentals. Anthracnose is easily seen on good quality maples, and apple scab is rapidly defoliating both crabapples and production apples not in a regular spray program.
Both diseases fall into the category of "preventable but not curable," but don't despair. Assuming the trees have enough stored energy, they will leaf out next year and begin all over. The disease may hit or not, depending on the weather conditions, but odds are at some point in the year you will see it again on susceptible varieties.
July 15, 2010
Septoria leaf blight is attacking tomatoes again with a vengeance. For a review, 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.
July 15, 2010
The crickets, millipedes, earwigs, spiders, ants, and many others that find their way inside are a real nuisance. A foundation spray is the best line of defense, and you would select a material such as permethrin or bifenthrin to begin with. Then spray the foundation and the adjacent foot or two of soil or plant material with the spray mixture. Both these products are cleared on most types of plants. Foundation treatments should be applied every 7-15 days depending on the temperatures. The materials break down quicker in hot weather.
Foundation treatments won't prevent everything from getting in the house, and they certainly won't kill things already in the house. For insects already in the house, you have a few options. The first is mechanical control. This is fancy language for something like a flyswatter, shoe, vacuum cleaner, flypaper, or glue boards. The next is chemical control. This basically means aerosol cans inside the house. The most common ones are for flying insects or ants, although many of the flying insect killers now have permethrin in them and can last quite a while.
July 15, 2010
July 15, 2010
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. Treatment of burrowing areas with a pyrethroid insecticide or carbaryl (Sevin) may reduce problems.
July 15, 2010
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. Rust spores can easily be tracked into homes. Other turf diseases such as dollar spot and brown patch are also prevalent.
Low fertility (in particular nitrogen) and high temperatures slow down turf growth, allowing rust to develop. 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. Fungicides are rarely suggested on home lawns for rust control. Focus on the listed cultural practices described above.