Extension Educator, Local Food Systems and Small Farms
Extension Educator, Horticulture
June 30, 2009
Preserving insect enemies that reside in your garden will help control some insect pests, but sending additional enemies into the area may not be so useful. Many gardeners buy packages of "beneficial insects"—insects that feed on pests. Then they release the beneficial insects into the garden to control aphids and other crop-destroying insects. Most of the time people get much less out of these releases than they expected.
Three of the most common beneficial insects sold for this purpose are lady beetles, praying mantises and green lacewings. Two of these insects often do not do much good.
A common problem with mail-order lady beetles is that they fly away soon after being released. Because most of them will not stay in a backyard garden, only community-wide releases are likely to provide much benefit. Praying mantises are fascinating to watch, but they are not useful or efficient predators. Putting green lacewing eggs in the garden is really the most promising strategy, and even that has questionable value.
Already established populations of beneficial insects are likely to provide better results than introducing purchased insects. The following are some simple principles to help preserve any beneficial insects already living in your garden.
§ Learn how to recognize beneficial insects.
§ Minimize insecticide applications. Most insecticides kill beneficial insects along with the pests. For example, microbial insecticides that contain different strains of the bacterium Bacillus thuringiensis are toxic only to caterpillars, certain beetles or certain mosquito and black fly larvae.
§ Maintain ground covers, standing crops and crop residues. To survive the winter, many beneficial insects require the protection offered by vegetation. However, preserving ground covers and crop residues can also help certain pests. Evaluate this strategy according to its overall benefits and drawbacks.
§ Provide pollen and nectar sources or other supplemental foods. Plants with very small flowers make good sources of nectar for adults of certain beneficial wasps. Seed mixes of flowering plants intended to attract and nourish beneficial insects are sold at garden centers and through mail-order catalogs.When attempting to preserve beneficial insects, keep in mind that these natural enemies will never completely eliminate a pest. When a pest population becomes low, the beneficial insects often leave the area and search for more abundant prey. If you need 100 percent control, natural enemies alone usually do not provide enough control. However, natural enemies will reduce the pest population to moderate levels, which are acceptable in many cases. One other point to remember is that natural enemies take time to do their work. Insecticides have nearly immediate effects on pest populations, but natural enemies need time to search for prey or hosts.
June 30, 2009
Cucurbits are basically everything in the squash and melon families. There are several potential insect problems with them, and today's column attempts to help minimize or prevent these problems. The first group of insects is the cucumber beetles. These can be green, black and yellow striped, or black and yellow spotted. The importance of the beetles is not that they eat small holes in the leaves, but that the beetles can transmit a bacterial wilt to the plants as they eat. The first thing you see is you have a plant that suddenly wilts on various runners, or the entire plant. The best means of controlling this disease is a good beetle control program. Current homeowner recommendations would include these products with the days to harvest restrictions in parenthesis: carbaryl (0), bifenthrin (3 days), or rotenone (1 day).
Of course, Japanese beetles love cucurbits as well. Their damage is direct leaf feeding. Remember they feed in groups, so once they get started you will have a battle on your hands. The carbaryl and bifenthrin are both good control measures.
Squash bugs are the next problem to discuss. Squash bugs are usually dark gray to black in color and like a long stink bug. Their eggs usually hatch mid-June to mid-July. Best control timing is when the eggs first hatch. Non-restricted products are sabadilla (1 day), which is an organic product that might be a little hard to find, and bifenthrin (3 days to harvest). One last note, if the squash bugs get past their early growth stages then physically removing them is about the only control method available.
The last insect problem on cucurbits is squash vine borers. These borers usually drill into the new runner areas and kill off individual runners at a time. The adult of these larvae are red and black clear-winged moths. Scout your plants and look for the adults, as well as entrance holes and the chewed-up plant material. Treat as soon as early damage occurs and use one of the following products for homeowners: carbaryl, bifenthrin, or rotenone. Days to harvest restrictions have already been covered (and these would also apply to pumpkin blossoms).
June 30, 2009
If you haven't checked for bagworms yet, now would be a good time. Small bags have been noticed in the county for the last few weeks. Re-treatment may be necessary in some cases. Carbaryl (Sevin) will work on the smaller sized bagworms, while the B.t. products, such as thuricide, may be required for the larger ones.
Remember bagworms frequently start in the tops of trees. Bagworms are the larvae of clearwing moths that don't fly too well. If you control the bagworms well, you may not have high populations for a few years.
June 30, 2009
This is the time of year to wrap up pruning chores on evergreens. This includes both needle-type and broadleaf evergreens. If you're wondering what a broadleaf evergreen is, that includes holly, rhododendron, and azalea. The logic behind pruning your yews at this time is to allow sufficient time for regrowth to become hardened off before winter, and to keep new growth from becoming too rank before the winter months.
Pruning evergreens is part art and part science, but mostly art. A few simple rules to follow make the job results much more pleasing. Upright growing evergreens, such as pines and spruces, should not have the main leader cut off. This will destroy the natural shape, and will make the resulting growth more susceptible to breaking off. If individual branches are being cut off, they should be cut back to a bud. This will allow the bud to become the new main branch. You can also control growth direction of branches in this way. If you are growing trees for cut Christmas trees, all bets are off, as you are only dealing with trees through the first seven years of their life or so.
Make sure you use the proper equipment. Individual pruning cuts are best done with bypass loppers or pruning shears. These make clean cuts without much damage to the remaining wood. The old anvil type shears and loppers cut to a point, then crush the remaining wood. For yews, junipers, and arborvitae that are trained to a certain size of shape, you will want to use hedge shears (electric or manual) that are sharp and properly tightened. Most of these types of shears can cut up to about a quarter of an inch in size.
When pruning evergreens, remember the dead zone. This is the area toward the center of the plant that doesn't receive much light. It also has few needles or active buds. Cutting into the dead zone will cause many years (or forever) of little green growth. Also remember to prune so that the base of plants is wider that the top. This allows sunlight to hit the bottom area as well, and keeps the bottom from dying up.
June 29, 2009
June 24, 2009
Many major tree diseases cause vascular system blockage. Verticillium wilt, oak wilt, and most of the canker diseases fall into the group. Usually a fungus "plugs the pipes" so there is reduced movement of water up and food down. This leads to dead areas above the blockage. Of course, if the blockage is on the main trunk you end up with a dead tree. It is often possible to see streaking of the wood, or a dark ring around the center portion of the branch or trunk with verticillium wilt, but a lab analysis is needed for definite confirmation. There are no cures for any of these diseases at this time. It is recommended to remove and destroy trees severely infected with verticillium, to help prevent transfer from root grafting. The list of trees affected by verticillium is very large, but good quality maples are very susceptible. There have been many affected trees this year, including maples and ashes. The only treatment is to water and fertilize to try and get new growth, and new water and food carrying tissues.
We have really had twenty-plus years of stressful weather. Just like us, trees like moderate weather. When we have extreme heat and cold, and no moisture or a flood, the trees are stressed. This stress makes them more susceptible to things that are always in the environment. Try to even out some of the extremes by watering when it is dry, fertilizing when you do the lawn (or just fertilize the tree), and mulching to even out the soil temperature in the root area. Remember that many diseases can be passed with pruning equipment, so disinfect your equipment between cuts.
June 24, 2009
Many pumpkins are already on their way, with seeds being sown a month ago. While this practice is great for producing pumpkins for pumpkin pie, it really doesn't work very well for producing the Halloween jack-o-lantern pumpkins. The Halloween pumpkins are best planted around Father's Day. This timing helps prevent the pumpkins from rotting before we get to the end of October.
Many different varieties are available, and they come in many sizes and shapes. The small pumpkins, ranging from two to five pounds, are called "pie" types. They are normally used for cooking and fall decorations, and include the Baby Bear variety. Intermediate and large varieties are primarily used for jack-o-lanterns. Many of the newer varieties have stronger side walls to aid in display and carving. The flesh of these varieties is generally poor in quality and not used for cooking. Processing pumpkins, that are canned commercially make poor carving pumpkins, and are more like a buff colored watermelon in appearance. The jumbo or mammoth varieties are mainly used for exhibition. These jumbos can weigh in the 900 pound range. For most homeowners, you might want to pass on these since moving a 900 pound pumpkin isn't for everyone. The other option is to try and grow one in place.
Pumpkins should be planted about now for carving or fall decoration. Vining pumpkins need at least 50 – 100 feet per hill, with the larger pumpkins requiring the larger area. Hills should be five to six feet apart and rows of hills should be 10 – 15 feet apart. Each hill should have about four seeds per hill, planted about an inch deep. The miniature varieties such as the Jack-Be-Little are sometimes grown in rows with seeds planted every eight to twelve inches, then thinned to about two feet apart in the rows. Fall decoration pumpkins should be cut from the vine before the vine dries in order to have a good stem attached to the pumpkin, but after the color is acceptable.
Keep the pumpkin bed free from weeds by shallow hoeing, and make sure it is watered during extended dry periods. Major pests are squash bugs, cucumber beetles, and vine borers. Most often, frequent applications of an insecticide such as carbaryl will help protect the new runners from the vine borers and also control the beetles that transmit the wilt virus. Make sure no applications are made to open blooms, that attract the bees for pollination, by applying insecticides in late afternoon or early evening.
June 24, 2009
June 18, 2009
Have you noticed a sticky substance on the leaves of trees and shrubs, or have you recently parked your car under the boughs of a spreading maple only to discover it splattered with a sticky material?
If so, don't blame the tree. The substance is not tree sap, but an indication of an infestation of insects call aphids. Aphids, often called plant lice, seem to be infesting many plants this summer. They can be found on maples, peppers, cabbage, pine trees, bluegrass, apples and many other plants.
An aphid is usually specific to one plant or possibly a very few species. For example, the tomato aphid is found on tomatoes; the pine bark aphid is found on pine limbs and trunks; and the cabbage aphid infests cabbage, cauliflower and broccoli. However, some aphids are general feeders, such as the green peach aphid found on peach trees, peppers and potatoes.
Aphids are slow moving, winged or wingless, soft-bodied insects that vary in size and color. They multiply rapidly often producing young that mature in a week or less to produce even more aphids.
They also are very susceptible to disease and attack by parasites and predator insects. Therefore, an aphid population on a particular plant can increase rapidly or disappear just as fast.
Evidence of an aphid infestation includes curled leaves caused by aphid feeding, the presence of a sticky substance called "honeydew" with a sooty black mold growing on it and ash-colored skins shed by the aphids as they grow. Live aphids may have disappeared due to disease, lack of food or other factors.
A heavy stream of water will knock aphids off the plants. An insecticidal soap is an organic alternative. Heavy aphid infestations can generally be controlled by insecticide sprays including a few systemics. However, a few aphid species are resistant to some of these insecticides.
An infestation of aphids on healthy established shade trees generally does not need to be treated. The insignificant damage to the tree does not justify the cost of hiring a commercial sprayer who has the equipment to treat large trees. Heavy infestations on small or weak, ailing trees can be controlled with the above-mentioned insecticides.
Time and money is often better spent fertilizing and watering to insure good recovery and health. Avoid fertilizing trees and shrubs after July 15. Late summer fertilization can often stimulate lush growth that does not have sufficient time to harden off before winter sets in. The greatest response to fertilization is seen when it is applied in the fall or early spring.
June 17, 2009
Moss in lawns has been a frequent topic of conversation this year. Moss doesn't cause lawn decline, but tends to develop as lawns thin due to poor site or management factors. For example, moss may invade lawns with problems such as low soil fertility, poor soil drainage, compacted soils, excessive shade, poor air circulation, and high humidity. Poor lawn care practices are another source of moss problems. General neglect, irregular mowing, lack of fertilizer, and overwatering are common problems leading to poor turf growth that may lead to moss problems.
Moss can be temporarily eliminated by raking. Ferrous ammonium sulfate or ferric sulfate (iron sulfate) can also be used to control moss. The moss will temporarily burn away, but tends to return fairly quickly unless the site conditions and/or lawn care program is altered. Focusing on the reason you have moss is the best solution. Improving air circulation, reducing compaction, fertilizing properly, avoiding excess watering, selecting proper grass varieties, and mowing at the proper height are all considerations. Of course, the excess watering provided by Mother Nature is one of the main problems this year.
June 17, 2009
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. 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.
June 11, 2009
As if trees didn't have enough leaf problems with the diseases, herbicide drift has shown up in a big way this past week. All cases I have seen, the herbicides involved have been members of the growth regulator group. This group includes products such as 2,4-D and Banvel. Both products are used in agricultural production, right-of-way maintenance, and in home lawn care.
Leaf symptoms usually appear as some sort of abnormal growth. This can include twisting, cupping, elongation, and rolling. Since the chemicals are systemic growth regulators, they move throughout the trees (or shrubs or flowers) and then show the most damage on the newest growing points. Think of what a dandelion looks like after it has been treated with 2,4-D and you get the general idea.
Where the products come from on your trees is generally a big mystery. They can drift during the actual spraying process (called spray drift), or they can come back up off the ground as a vapor and move with winds (called vapor drift). The difficulty with vapor drift is that it can occur for up to one and one-half weeks after the application, and then can drift for up to a mile and a half.
Different species of trees are more susceptible than others, and the full-size leaves are less likely to show symptoms. Red buds, oaks, and lilacs are among the most susceptible trees. Grapes and tomatoes are among the most susceptible garden plants.
If you do have damage from herbicide drift, the end results can vary. Generally, on established perennials, the damage is ugly leaves for at least part of this growing season. You can also have some "wave" to the ends of branches, and possibly the loss of some small branch ends. On younger stock, transplanted in the last year or so, the damage may be fatal. It usually takes several weeks to get an indication of the amount of damage done, but a year is even better.
As for treatment, water when the weather stays dry. Don't fertilize at this time. Remember that growth regulator herbicides make things "grow themselves to death." You have to walk a fine line between keeping the tree healthy and making matters worse.
June 11, 2009
Soldier beetles will be appearing shortly. They look like pale lightning bugs without the light, and are very common around pollinating linden trees. Since soldier beetles are beneficial, it is inadvisable to kill them. They feed on small insects such as aphids, however, they do qualify as a nuisance pest in much the same way as the Asian lady bugs. Weather-stripping and caulking will help keep them out of your house. A vacuum cleaner will safely remove soldier beetles that are found inside.
After some very severe infestations of bagworms the past few years, the calls have been coming in all year on the correct treatment times for bagworms this year. Year-in and year-out, the correct treatment time for bagworms is June 15. You can mark this date on your calendar fornext year and be within a few days of the correct treatment time. With a very cool spring, a week later may be a possibility, but this season's yo-yo temperatures really even out. The idea is to have all the eggs hatched before treatment. The traditional treatment has been Sevin, but the B.t. products such as Dipel and Thuricide have really taken the majority of the market. Many other products will work, but the B.t. products have several good points including safety to mammals and toxicity to larger bagworms. If you are in doubt about whether you have bagworms, check your trees and shrubs around June 15. You can actually see the small bags as the larvae build.
June 4, 2009
If you have been following a foundation spray program all year, keep it up. If you haven't been, it is probably time to start. The foundation spray program is your first line of defense against nuisance pests in the house. It cuts down on crickets, millipedes, spiders, ants, and many others that find their way inside. And, with the crickets singing, it's only a matter of time before they find their way into your abode.
To accomplish a foundation spray, 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.
June 4, 2009
As mentioned a week or so ago, fungal leaf diseases were present. They are now making their presence felt with a vengeance. These diseases infected trees and shrubs earlier, and they have continued to develop rapidly. Some trees are now to the point of being, well, leafless.
Anthracnose is the number one fungal disease of good quality shade trees, and apple scab is hitting apples and crabapples hard. To give a brief overview, these diseases are preventable but not curable. They are seldom life threatening to the tree or shrub, but they can make things look rather unsightly. Many shade trees losing a large percentage of their leaves will often set another set of leaves within four to six weeks. Apples and crabapples are less likely to set another set of leaves, but it sometimes happens.
Anthracnose has different stages depending on the time of infection. There is a bud stage, where buds are killed as they begin to open. Next is a leaf stage, which affects only leaves. This stage is the one we are commonly seeing, and it infects leaves and gradually consumes the leaf. And the other stage is the twig stage which affects smaller twigs on trees and shrubs. This is one reason why sycamore trees tend to have so many small branches break. The infection leaves a brittle scar on the branch which makes it susceptible to breakage.
As I mentioned, once infection has occurred it can't be cured. The prevention part needs to begin with a regular spray program similar to production apples. This means starting when the leaves are just out of the bud in the early spring. The same kind of timing applies to ornamental trees. The main harm caused is the loss of food produced by the lost leaves, and the loss of energy to set another set of leaves. Fertilizer application at the lawn rate, to supply a pound of nitrogen per 1,000 square foot broadcast, will help the tree as much as anything.
June 4, 2009
With the widely fluctuating amounts of rainfall, blossom end rot is definitely a possibility. The best solution is to mulch tomato plants to help even out the moisture supply, and help keep the roots cooler. This problem is caused by uneven calcium amounts in the plant. Addition of lime when you see the problem usually isn't as effective as evening out the moisture flow for the plant by mulching. Any material will do (grass clippings, straw, commercial mulch, etc.) with two inches being adequate and four inches being better.