The shelf life of pesticides is a frequent topic of concern for gardeners. You'll often get such questions as, "How long is a pesticide good for, and how long should I keep a pesticide?" Expiration dates are seldom found on the label.

In general, pesticides are manufactured, formulated, and packaged to specific standards. However, when stored improperly, they can break down, especially under conditions of high temperature and humidity.

Dry formulas such as wettable powders (WP) or granular (G) can become caked and compacted. Emulsifiable concentrates (EC) can lose their ability to form emulsions. Some pesticides can actually become more toxic, flammable, or explosive as they break down.

Pesticide formulations that contain low concentrations of active ingredients generally lose effectiveness faster than more concentrated forms. Sometimes, a liquid pesticide develops a gas as it deteriorates, making opening and handling containers quite hazardous.

Certain pesticides have a characteristic odor. A strong odor in the storage area may indicate a leak, spill, or improperly sealed container. It may also be a clue that the pesticide is deteriorating, because the smell of some chemicals intensifies as they break down.

Pesticide containers, including fiber and metal drums, pails, bottles, cans, bags, boxes, over packs, and liners, have an important effect on storage and shelf life. If stored for long periods, these containers may eventually corrode, crack, break, tear, or fail to seal properly. The label may become illegible as well.

If stored in a cool, dry area out of direct sunlight, pesticides will generally have an extended shelf life. Protection from temperature extremes is important because heat or cold can shorten a pesticide's shelf life.

At temperatures below freezing, some liquid formulations separate into their various components and lose their effectiveness. High temperatures cause many pesticides to volatize or break down more rapidly. Extreme heat may also cause glass bottles to break or explode.

The best way to ensure avoidance of shelf life or storage problems is to only buy what is needed for one season.

Before storing chemicals, read the label and follow the guidelines listed. Store different groups of pesticides, such as herbicides, insecticides, and fungicides, in separate locations within a storage area to prevent cross-contamination from fumes and vapors, as well as accidental use of the wrong type of pesticide.

Never store chemicals near any type of animal feed. Always store chemicals out of the reach of children, preferably in a locked cabinet.

Spring weather promotes the growth of trees, flowers, and lawns. It also promotes diseases that turn around and attack the plants. None is probably more devastating and noticeable than shade tree anthracnose.

Anthracnose affects most of the major shade trees. However, while symptoms appear similar, different fungal organisms affect different plants.

The disease causes spots or lesions on leaves, flowers, twigs, and branches. In most cases, the disease starts out with small, irregular-shaped spots on the leaf. Spots enlarge and leaves may curl, die, and fall off. Lesion colors range from tan to brown to olive green to black. Many trees appear defoliated or sparsely leafed out. Symptoms are noticeable during the latter part of May and into June.

Trees usually affected include ash, birch, catalpa, dogwood, elm, hickory, linden, maple, oak, poplar (including cottonwood and aspen), tulip, and walnut. However, no tree gets hit as much as the sycamore, which has lived with the disease since records have been kept. Just looking at a sycamore should give gardeners a clue as to the amount of damage to expect on other plants.

The color of the leaf lesions varies. Dogwood exhibits a dark purple color. Elms show a gray to black color, while lindens are light brown with some yellow.

Ash, maple, and sycamores are most often the hardest hit. Ash trees start with tan to brown lesions on the leaflets, usually at the margins or along the veins. Leaves curl, become distorted, and fall. Maple infections vary. Japanese maple shoots may turn black and shrivel. Purple or brown streaks develop along the veins of Norway maples, including the "Crimson King" varieties. Greenish brown to reddish brown spots develop between the veins of sugar maples. Spots merge as they get larger, and leaves curl.

Sycamore anthracnose appears the most serious, though the trees recover more easily than any others. Leaves develop brown lesions along the veins. Entire leaves then turn brown, curl, and fall. Sycamore anthracnose also attacks twigs and young shoots—girdling them and causing them to die back and drop.

Anthracnose thrives and develops when spring temperatures are cool and moisture is adequate. Disease symptoms are increased as warmer temperatures occur.

Trees seldom die as a result of anthracnose. Most have the ability to produce new sets of leaves. Since environmental conditions are different in June and July, anthracnose fungal spores seldom infect new leaves and twigs.

However, reproducing new leaves does limit the tree's growth and reduces the food reserves. Repeated infections over the years can reduce the plant's vigor and make it more susceptible to other disease or insect problems.

Control is difficult. Protective fungicide sprays are usually too late and too costly to provide any acceptable control except on small trees.

Sanitation is crucial for good control. Rake up fallen leaves and branches. Leaves may be composted to kill the disease spores if the compost pile reaches 140 degrees or higher. If the compost pile decomposes on the cool side, it's better to burn, bury, or discard the leaves and twigs.

Fertilize the tree in mid- to late October according to guidelines found in the Master Gardener notebook and Horticulture Fact Sheets available at your local U of I Extension office.

Watering may be necessary throughout the summer to reduce the tree's stress. Water thoroughly and deeply as opposed to small amounts daily. Make sure the tree is mulched with 2 to 4 inches of wood chips.

Weeds are a fact of life in the yard and garden. Cultural methods include hand pulling and cultivating; flaming using a hand-held propane torch; and reducing seed in the soil by using the stale seed bed method (intermittent tillage before planting), avoiding introduction of weed seeds (in manure and hay), and never allowing weeds to go to seed. Barriers such as fabric mulch and replacing soil with sterilized soil mixes in containers and raised beds can also control weeds.

Chemical control focuses on stopping weed seed germination by using a "pre-emergent" herbicide such as Preen^TM or by spraying existing weeds with a "post-emergent" material such as Roundup^TM. Always read and follow label directions, and be especially careful when using herbicides near desirable plants. Weather conditions, irrigation, and plant growth stage can affect success with herbicide products. Also, note any special application statements on the label.

Pre-emergent materials vary in their effectiveness against different weeds. Weeds controlled are listed on the product label. Timing the application before germination of seeds is critical. For example, crabgrass is an annual grassy weed which germinates in the spring when soil temperatures reach 60 degrees and above. Thus, timely spring application is needed for crabgrass control products to be effective. If they are applied too soon, the material may lose its effectiveness before the weeds germinate.

Winter annuals such as henbit and chickweed in turf germinate in the mid-fall as soils cool. These weeds grow slowly all winter and go to seed in the spring. A well-timed early fall application using a pre-emergent herbicide can prevent these weeds from establishing.

Post-emergent herbicides can be contact kill only or translocated into the plant's system, moving downward to kill underground root parts. Post-emergent materials can also be selective or non-selective in the types of weeds controlled. Selective materials usually kill either only grass or only broadleaf weeds—not both.

So what is the best approach? The answer depends on the weed and situation, but it can involve either or both cultural and chemical methods.

For lawns, both grassy and broadleaf weeds can be a problem. In addition to using timely pre-emergent materials in the spring and fall, selective post-emergent broadleaf materials such as 2,4-D and dicamba can be applied to turf without injury to grass. These materials are often sold with fertilizers as a dry product that sticks to leaves, but they can also be sprayed on as a liquid formulation.

In landscape and perennial beds, mulching, hand-pulling, and cultivating can be effective. Fabric mulches are useful, though over time, weed seeds can blow in and start growing in the mulch on top of fabrics. In new beds, an application of Preen^TM can be a valuable tool. Spot spraying with a post-emergent product such as Roundup^TM must be done with care in landscape beds because even a light breeze can blow the spray material onto desirable plants and damage them.

Vegetable gardens planted in rows can be mechanically cultivated or hoed by hand. Always remember that a young weed is more easily killed than an older weed. Preen^TM is also labeled for use in gardens but should only be used around transplanted vegetables and perennial crops such as asparagus and rhubarb. Carefully read the Preen^TM label before applying around edible crops.

Perennial weeds present a special challenge. Quackgrass, Johnsongrass, nutsedge, field bindweed, pokeberry, poison ivy, and Japanese honeysuckle are persistent perennial grass and broadleaf weeds. Hand pulling and hoeing often results in removing top growth and partial removal of the root system, and plants quickly sprout back. With some species, cultivating and rototilling can break up underground rhizomes and spread them farther.

Translocated herbicides such as Roundup^TM and 2,4-D are good tools to manage perennial weeds, but the applications should be well timed and the appropriate materials matched with the weed being controlled. Good timing involves spraying after the plants have begun growing and are actively sending storage nutrients to stems and underground plant parts for next year. So, a mid- to late summer application is ideal. Roundup^TM is a better grass than broadleaf herbicide; but at high rates, it will kill many broadleaf weeds. 2,4-D is only effective on broadleaf weeds.

With proper approaches and tools, weeds can be effectively managed in the landscape and in the garden.

The idea that the vegetable planting season is over after Memorial Day is just plain wrong.

The warm June soils are great for pumpkins, cucumbers, gourds, and squash.

They languish if planted in May, but they will zoom in June.

Green beans are short-season crops that can be planted weekly through July for an ongoing tasty harvest that ends with the frost.

Cabbage, kale and broccoli planted in June will love the cool fall weather. But, lettuce is not a good option. Lettuce grown in the heat of the summer is bitter and bolts--it sends up a flower stalk and then goes to seed.

If you have lettuce or radish seeds, save them to plant in late August and early September for a lovely fall garden.

As clients have questions, remember that the Watch Your Garden Grow website is filled with tips and information on vegetable gardening. Bookmark the site in your web browser: www.urbanext.uiuc.edu/veggies/

Tony Bratsch
David Robson
Martha Smith
Nancy Pollard