Plant Health: Insects and Integrated Pest Management (IPM)
Integrated Pest Management (IPM) is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interaction with the environment. This information, in combination with available pest control methods, is used to manage pest damage by the most economical means, and with the least possible hazard to people, property, and the environment.
IPM is not a single pest control method but, rather, a series of pest management evaluations, decisions and controls. In practicing IPM, growers who are aware of the potential for pest infestation follow a four-tiered approach. The four steps include:
- Set Action Thresholds
Before taking any pest control action, IPM first sets an action threshold, a point at which pest populations or environmental conditions indicate that pest control action must be taken. Sighting a single pest does not always mean control is needed. The level at which pests will become an economic threat is critical to guide future pest control decisions.
- Monitor and Identify Pests
Not all insects, weeds, and other living organisms require control. Many organisms are innocuous, and some are even beneficial. IPM programs work to monitor for pests and identify them accurately, so that appropriate control decisions can be made in conjunction with action thresholds. This monitoring and identification removes the possibility that pesticides will be used when they are not really needed or that the wrong kind of pesticide will be used. - Prevention
As a first line of pest control, IPM programs work to manage the crop, lawn, or indoor space to prevent pests from becoming a threat. In an agricultural crop, this may mean using cultural methods, such as rotating between different crops, selecting pest-resistant varieties, and planting pest-free rootstock. These control methods can be very effective and cost-efficient and present little to no risk to people or the environment. - Control
Once monitoring, identification, and action thresholds indicate that pest control is required, and preventive methods are no longer effective or available, IPM programs then evaluate the proper control method both for effectiveness and risk. Effective, less risky pest controls are chosen first, including highly targeted chemicals, such as pheromones to disrupt pest mating, or mechanical control, such as trapping or weeding. If further monitoring, identifications and action thresholds indicate that less risky controls are not working, then additional pest control methods would be employed, such as targeted spraying of pesticides. Broadcast spraying of non-specific pesticides is a last resort.
This section will focus on insects and IPM. THe next section will address diseases and IPM.
Insects are neither good nor bad. They simply are. However, their actions can be positive for palnt health or negative. The goal in IPM is to maximize beneficial insect plant interactions while minimzing destructive insect plant interactions. Insects are a food source for some, pollinate plants, remove waste and area a natural predator. They can also be destructive to plants and spread diseases. Taske the ladybug for example. Ladybugs are beneficial insects that play a major role in keeping down populations of insects that feed on plants. Perhaps most importantly, ladybugs are predators with an insatiable appetite for aphids. A ladybug can eat up to 5,000 aphids over its lifetime! They can also help to rid your garden of other soft-bodied insects such as mites, mealybugs and leafhoppers, along with insect eggs and even ants. For this example, if you have aphids, releasing ladybugs into the garden is much more beneficial than spraying to eliminate the aphids, particularly as spraying must be repeated several times to kill all stages of the insect life cycle.
Signs of insect infestation include damage to the parts of the plant including defoliation, leafmining, stem boring, eggs, scars, distortions and color changes.
The most common insect pests in this area are mealy bugs thrips, aphids, spider mites, web worms, and gall. While the Emerald Ash Borer is a particular pest, many ash trees have already been destroyed and ash trees are not popluar in this area dus to the high chance of reinfection.
IPM Management of Insects Common to This Area
IPM management includes addressing cultural practices, biological control and, if needed, chemical treatment.
Mealy Bugs:
Mealybugs are soft, oval, wax-covered insects that feed on many plants in garden, landscape, and indoor settings. Usually found in colonies, they are piercing-sucking insects closely related to soft scales but lack the scale covers. Like soft scales, they can produce abundant honeydew and are often associated with black sooty mold. Mealybugs are favored by warm weather and thrive in areas without cold winters or on indoor plants. Adult females of most mealybugs lay 100-200 or more eggs in cottony egg sacs over a 10- to 20-day period. The young mealy bug has not deveopled its wax coating but quickly does so when it settles to feed. Mealybugs suck sap from plant phloem, reducing plant vigor, and they excrete sticky honeydew and wax, which reduces plant and fruit quality, especially when black sooty mold grows on the honeydew.
Cultural Practices
Because of their wax coating, mealybugs are very difficult to manage with insecticides. Fortunately most species have natural enemies that keep their populations below damaging levels in outdoor systems such as landscapes and gardens. The best approach to managing mealybugs is to choose plants known to be less prone to problems, inspect plants for mealybugs before bringing them onto your property, and rely on biological control and cultural practices to keep mealybug numbers in check. Mealy bugs can not move fast so infectations usually come from new plants or unclcean tools. Clean tools often and disinfect with alcohol occasionally. If found on new plants return to the nursery from which it came. It is not worth the effort to control mealy bugs once in the garden. Regularly inspect mealybug-prone plant species in your landscape or indoor plantings for mealybugs. If you find an infestation, physically remove the insects by handpicking or prune them out. Toss out older “grandmother” plants that may be a source of infestation for new plants. Check pots, stakes, and other materials for mealybugs and their egg sacs and dispose of any infested items. If mealybugs are somewhat exposed, it may be possible to reduce populations on sturdy plants with a high-pressure or forcible spray of water. Repeat applications at several-day intervals may be necessary. Avoid unnecessary applications of nitrogen fertilizer on plants with mealybugs. High rates of nitrogen coupled with regular irrigation may stimulate tender new plant growth as well as mealybug egg production.
Biological Control
Natural enemies include a number of species of parasitic wasps that lay their eggs in or on developing mealybugs. Naturally occurring predators of mealybugs include lady beetle, green and brown lacewings, spiders, minute pirate bugs, and larvae of predaceous midges. Preserve naturally occurring biological control agents by avoiding use of broad-spectrum insecticides for any pests in the area. Also keep ants out of mealybug-infested areas and plants because ants protect mealybugs from their natural enemies.
Chemical Treatment
Nonchemical methods usually provide sufficient control for outdoor plantings in gardens and landscapes. Home and garden insecticides are not very effective for mealybugs, especially on larger plants. The mealybugs’ waxy coating repels most contact insecticides, and their habit of aggregating in hidden locations makes them hard to reach.
For houseplants, greenhouses, and interiorscapes where it is not physically possible to remove mealybugs and where biological control may not be feasible, spot treatment may be used to suppress populations of aboveground feeding mealybugs. On small infestations on houseplants, a 70% or less solution of isopropyl (rubbing) alcohol in water may be dabbed directly on mealybugs with a cotton swab to kill them or remove them. Test the solution out on a small part of the plant 1 to 2 days beforehand to make sure it does not cause leaf burn (phytotoxicity). In some cases, a much more diluted solution may be advisable. Where infestations are extensive, a 10-25% solution of isopropyl alcohol can be applied with a spray bottle. You will need to repeat this procedure every week (to control all stages of the larvae) until the infestation is gone. Insecticidal soaps, horticultural oil, or neem oil insecticides applied directly on mealybugs can provide some suppression, especially against younger nymphs that have less wax accumulation.
Scale
Scales are sucking insects that insert their tiny, strawlike mouthparts into bark, fruit, or leaves, mostly on trees and shrubs and other perennial plants. Some scales can seriously damage their host, while other species do no apparent damage to plants even when scales are very abundant. The presence of scales can be easily overlooked, in part because they do not resemble most other insects. Adult female scales and immatures (nymphs) of most species are circular to oval, wingless, and lack a separate head or other easily recognizable body parts. Some scale species, when abundant, weaken a plant and cause it to grow slowly. Infested plants appear water stressed, leaves turn yellow and may drop prematurely, and plant parts that remain heavily infested may die. The dead brownish leaves may remain on scale-killed branches, giving plants a scorched appearance. If the scale produces honeydew, this sticky excrement, sooty mold, and the ants attracted to honeydew can annoy people even when scales are not harming the plant.
Cultural Practices
Many species are usually well controlled by beneficial predators and parasites (natural enemies). Exceptions are when natural enemies are disrupted by ants, dust, or the application of persistent broad-spectrum insecticides. Preserving (conserving) parasites and predators (such as by controlling pest-tending ants) may be enough to bring about gradual control of certain scales as natural enemies become more abundant.
A well-timed and thorough spray of horticultural (narrow-range) oil during the dormant season, or soon after scale crawlers are active in late winter to early summer, can provide good control of most species of scale. Provide plants with good growing conditions and proper cultural care, especially appropriate irrigation, so they are more resistant to scale damage. You can prune off heavily infested twigs and branches, if they are limited to a few parts of small plants. In areas with hot summers, pruning to open up canopies can reduce populations of black scale, citricola scale, cottony cushion scale, and possibly other scales by increasing scale mortality from exposure to heat and parasites. Consider replacing problem-prone plants.
Biological Control
Scales are preyed upon by small parasitic wasps and many predators, including certain beetles, bugs, lacewings, and mites. Ant control, habitat manipulation, and pesticide management are the key natural enemy conservation strategies. If ants are abundant, selectively control them. Grow a variety of flowering plants to help attract and support natural enemies. Adults of predatory bugs, lacewings, lady beetles, and parasitic wasps live longer, lay more eggs, and kill more scales when they have plant nectar or pollen and insect honeydew to feed on. Avoid creating dust because it interferes with natural enemies. For example, rinse small plants when foliage becomes dusty. Depending on the scale species and the extent to which biological control has been disrupted, it will take several months of conservation efforts (such as controlling ants and dust and avoiding application of persistent insecticides) or until the next season or longer before scale populations are reduced by biological control. If current levels of scales are intolerable, spray insecticidal oils to reduce scale populations while conserving natural enemies.
Ant control is critical. See how to do this in other sections.
Chemical Treatment
Where plants can be sprayed, complete spray coverage of infested plant parts with horticultural oil at the proper time provides good control of most scales. Horticultural oils (e.g., Bonide Horticultural Oil and Monterey Horticultural Oil) are specially refined petroleum products, often called narrow-range, superior, or supreme oils. Other nonpersistent, contact sprays for garden and landscape plants include insecticidal soap (Safer Brand Insect Killing Soap Concentrate II), neem oil (Bayer Advanced Natria Neem Oil Concentrate, Green Light Neem, Garden Safe Brand Neem), canola oil (Bayer Advanced Natria Multi-Insect Control), and other botanical (plant-derived) oils.
These insecticides have low toxicity to people and pets and relatively little adverse impact on the populations of pollinators and natural enemies and the benefits they provide. To obtain adequate control, thoroughly wet the infested plant parts with spray, typically shoot terminals and the underside of leaves. More than one application per growing season may be needed, especially if the targeted pest has more than one generation a year. Thorough spray coverage is especially critical when treating armored scales and oak pit scales as these scales are generally less susceptible to pesticides than soft scales.
Thrips
Thrips, order Thysanoptera, are tiny, slender insects with fringed wings. They feed by puncturing the epidermal (outer) layer of host tissue and sucking out the cell contents, which results in stippling, discolored flecking, or silvering of the leaf surface. Thrips feeding is usually accompanied by black varnishlike flecks of frass (excrement). Certain thrips are beneficial predators that feed on other insects and mites. Be aware that the presence of thrips does not mean that damage will result from their feeding. Large numbers of thrips in traps, or adults in flowers feeding on pollen, do not necessarily indicate that control action is needed. Treatment is only neededd if the insect is causing extensive damage.
Cultural Practices
Grow plants that are well-adapted to conditions at that site. For example, plants adapted to grow in full sun can be stressed when planted in shady conditions and may be more susceptible to thrips damage. Provide appropriate cultural care to keep plants vigorous and increase their tolerance to thrips damage. Keep plants well irrigated, and avoid excessive applications of nitrogen fertilizer, which may promote higher populations of thrips. Old, spent flowers can harbor thrips, so their removal and disposal is sometimes recommended. However, the general benefit of this practice in landscapes is unknown; and old blossoms also commonly shelter beneficial predators of thrips.
Prune and destroy injured and infested terminals when managing a few small specimen plants in the landscape. Avoid shearing plants, which is the clipping of dense foliage to maintain an even surface on formal hedges or creating specific shapes (topiary). Shearing stimulates thrips-susceptible new growth. Prune by cutting plants just above branch crotches and nodes instead of shearing off terminals. Any type of covering that excludes insects but allows light and air penetration can be used. With sturdy crops that do not grow too tall, floating row covers (vented polyethylene, spunbonded polyester, point-bonded polypropylene) can be placed on top of beds with no frames or hoops. The crop itself lifts the fabric as it grows. For plants that grow upright or have sensitive tips that might be damaged when pushing against covers, use hoops, plastic tunnels, or wire strung between posts to hold up covers. Wood, wire, or plastic frames covered with muslin, nylon, or other fine mesh can be used for several years.
Biological Control
Predatory thrips, green lacewings, minute pirate bugs, mites, and certain parasitic wasps help to control plant-feeding thrips. Where thrips are a problem, learn whether that pest has specific natural enemies important in its control. Taking a sample to the Horticultural Answer Line at the Botanical Garden may assist with this.
Chemical Treatment
Although thrips damage is unsightly, it does not usually warrant the use of insecticides in gardens and landscapes. Feeding injury typically does not become apparent until after tissue grows and expands. Thus, by the time damage is noticed on ripening fruit or distorted terminals, the thrips that caused the damage are often gone. No pesticide application will restore the appearance of injured tissue; plants will remain damaged until leaves drop, injury is pruned off, or new unblemished fruit is produced. Where plant viruses are a problem, insecticides typically do not kill thrips fast enough to prevent the transfer of virus from thrips to plants.
Aphids
Aphids are small, soft-bodied insects with long slender mouthparts that they use to pierce stems, leaves, and other tender plant parts and suck out fluids. Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
Aphids have many generations a year. So care must be continuous to control an aphid infestation. When the weather is warm, many species of aphids can develop from newborn nymph to reproducing adult in seven to eight days. Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.
Large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus. Some aphid species inject a toxin into plants, which causes leaves to curl and further distorts growth. Aphids may transmit viruses from plant to plant on certain vegetable and ornamental plants. Although aphids seldom kill a mature plant, the damage they do and unsightly honeydew they generate sometimes warrant control.
Cultural Practices
Check your plants regularly for aphids—at least twice a week when plants are growing rapidly—in order to catch infestations early, so you can knock or hose them off or prune them out. Many species of aphids cause the greatest damage in late spring when temperatures are warm but not hot (65°-80°F). For aphids that cause leaves to curl, once aphid numbers are high and they have begun to distort leaves, it’s often difficult to control these pests, because the curled leaves shelter aphids from insecticides and natural enemies. Many aphid species prefer the underside of leaves, so turn leaves over when checking for aphids. Ants are often associated with aphid populations, especially on trees and shrubs, and frequently are a clue that an aphid infestation is present. If you see large numbers of ants climbing your tree trunks, check higher up the tree for aphids or other honeydew-producing insects that might be on limbs and leaves. To protect their food source, ants ward off many predators and parasites of aphids. Managing ants is a key component of aphid management.
Where aphid populations are localized on a few curled leaves or new shoots, the best control may be to prune out these areas and dispose of them. In large trees, some aphids thrive in the dense inner canopy; pruning out these areas can make the habitat less suitable.
High levels of nitrogen fertilizer favor aphid reproduction, so never use more nitrogen than necessary. Instead, use a less soluble form of nitrogen and apply it in small portions throughout the season rather than all at once. Slow-release fertilizers such as organic fertilizers or urea-based time-release formulations are best.
Because many vegetables are susceptible to serious aphid damage primarily during the seedling stage, reduce losses by growing seedlings under protective covers in the garden, in a greenhouse, or inside and then transplanting them when the seedlings are older and more tolerant of aphid feeding. Protective covers will also prevent transmission of aphid-borne viruses.
Another way to reduce aphid populations on sturdy plants is to knock off the insects with a strong spray of water. Most dislodged aphids won’t be able to return to the plant, and their honeydew will be washed off as well. Using water sprays early in the day allows plants to dry off rapidly in the sun and be less susceptible to fungal diseases.
Biological Control
Natural enemies can be very important for controlling aphids. Usually natural enemy populations don’t appear in significant numbers until aphids begin to be numerous. Many predators also feed on aphids. The most well known are lady bugs, lady beetle adults and larvae, lacewing larvae, soldier beetles, and syrphid fly larvae. Naturally occurring predators work best, especially in garden and landscape situations. In some situations ants tend aphids and feed on the honeydew aphids excrete. At the same time, ants protect the aphids from natural enemies. If you see ants crawling up aphid-infested trees or woody plants, put a band of sticky material (e.g., Tanglefoot) around the trunk to prevent ants from climbing up. (Don’t apply sticky material directly to the bark of young or thin-barked trees or to trees that have been severely pruned, as the material may have phytotoxic effects. Wrap the trunk with fabric tree wrap or duct tape and apply sticky material to the wrap.) Alternatively, ant stakes or containerized baits may be used on the ground to control ants without affecting aphids or their natural enemies. Prune out other ant routes such as branches touching buildings, the ground, or other trees.
Chemical Treatment
When considering whether to apply insecticides for aphid control, remember that most larger plants can tolerate light to moderate levels of aphids with little damage. Larger aphid populations often rapidly decline due to biological control or when hot temperatures arrive. Often a forceful spray of water or water-soap solution, even on large street trees, when applied with appropriate equipment, will provide sufficient control.
If insecticides are needed, insecticidal soaps and oils are the best choices for most situations. Oils may include petroleum-based horticultural oils or plant-derived oils such as neem or canola oil. These products kill primarily by smothering the aphid, so thorough coverage of infested foliage is required. Apply these materials with a high volume of water, usually a 1 to 2% oil solution in water, and target the underside of leaves as well as the top. Soaps, neem oil, and horticultural oil kill only aphids present on the day they are sprayed, so applications may need to be repeated. Although these materials can kill some natural enemies that are present on the plant and hit by the spray, they leave no toxic residue so they don’t kill natural enemies that migrate in after the spray.
Many other insecticides are available to control aphids in the home garden and landscape, including foliar-applied formulations of malathion, permethrin, and acephate (nonfood crops only). While these materials may kill higher numbers of aphids than soaps and oils, their use should be limited, because they also kill the natural enemies that provide long-term control of aphids and other pests, and they are associated with bee kills and environmental problems. Repeated applications of these materials may also result in resistance to the material.
Spider Mite
Mites are common pests in landscapes and gardens that feed on many fruit trees, vines, berries, vegetables, and ornamental plants. Although related to insects, mites aren’t insects but members of the arachnid class along with spiders and ticks. Spider mites live in colonies, mostly on the undersurfaces of leaves; a single colony may contain hundreds of individuals (Figure 2). The names “spider mite” and “webspinning mite” come from the silk webbing most species produce on infested leaves (Figure 3). The presence of webbing is an easy way to distinguish them from all other types of mites and small insects such as aphids and thrips, which can also infest leaf undersides. Mites overwinter as red or orange mated females under rough bark scales and in ground litter and trash. They begin feeding and laying eggs when warm weather returns in spring. Spider mites reproduce rapidly in hot weather and commonly become numerous in June through September. If the temperature and food supplies are favorable, a generation can be completed in less than a week (Figure 5). Spider mites prefer hot, dusty conditions and usually are first found on trees or plants adjacent to dusty roadways or at margins of gardens. Plants under water stress also are highly susceptible. As foliage quality declines on heavily infested plants, female mites catch wind currents and disperse to other plants. High mite populations may undergo a rapid decline in late summer when predators overtake them, host plant conditions become unfavorable, and the weather turns cooler as well as following rain. Mites cause damage by sucking cell contents from leaves.
Cultural Practices
Be sure mites are present before you treat. Sometimes the mites will be gone by the time you notice the damage; plants will often recover after mites have left. Spider mites have many natural enemies that often limit populations. Adequate irrigation is important, because water-stressed plants are most likely to be damaged. Broad-spectrum insecticide treatments for other pests frequently cause mite outbreaks, so avoid these pesticides when possible. Best results are obtained by creating favorable conditions for naturally occurring predators, such as avoiding dusty conditions and insecticide sprays.
Dusty conditions often lead to mite outbreaks. Apply water to pathways and other dusty areas at regular intervals. Water-stressed trees and plants are less tolerant of spider mite damage. Be sure to provide adequate irrigation. Midseason washing of trees and vines with water to remove dust may help prevent serious late-season mite infestations.
In gardens and on small fruit trees, regular, forceful spraying of plants with water often will reduce spider mite numbers adequately. Be sure to get good coverage, especially on the undersides of leaves. If more control is required, use an insecticidal soap or oil in your spray.
Biological Control
Insects are also important predators—lady bugs, sixspotted thrips, the larvae and adults of the spider mite destroyer lady beetle, the larvae of certain flies, and various general predators such as minute pirate bugs, bigeyed bugs, and lacewing larvae.
Chemical Treatment
Spider mites frequently become a problem after applying insecticides. Such outbreaks are commonly a result of the insecticide killing off the mites’ natural enemies but also occur when certain insecticides stimulate mite reproduction. If a treatment for mites is necessary, use selective materials, preferably insecticidal soap or insecticidal oil. Both petroleum-based horticultural oils and plant-based oils such as neem, canola, or cottonseed oils are acceptable. There are also a number of plant extracts formulated as acaricides (a pesticide that kills mites) that exert an effect on spider mites. These include garlic extract, clove oil, mint oils, rosemary oil, cinnamon oil and others. Don’t use soaps or oils on water-stressed plants or when temperatures exceed 90°F. These materials may injure some plants, so check labels and/or test them out on a portion of the foliage several days before applying a full treatment. Oils and soaps must contact mites to kill them, so excellent coverage, especially on the undersides of leaves, is essential, and repeat applications may be required.
Web Worm
Webworms overwinter as larvae or pupae and emerge in early spring. Adults are small buff to smoky brown colored moths that are active at night. They may be readily observed flying out of the foliage during the day as you walk through the field. They consume large amounts of foliage by skeletonizing leaves, and can completely defoliate a field in a very short period of time. As they devour leaves, webworms spin a web, drawing leaves together or folding individual leaves together to form a tube in which they hide when disturbed.
Cultural Practices
It may be necessary to cut out the limbs covered by the webworks. Do not put into compost.
Biological Control
Numerous parasites and predators have been reported on webworms. However, it is doubtful that any of these agents are capable of regulating webworm populations.
Chemical Treatment
Oak Gall
Distorted, sometimes colorful swellings in branches, flowers, leaves, or twigs caused by gall wasps are especially abundant and varied on oaks. Oak gall wasps alternate between one sexual and one asexual generation each year. Several weeks or months after egg laying by the female wasp, a gall forms as one or more white larvae feed inside. Galls on woody parts and evergreen foliage can persist long after the wasp larvae have completed feeding and emerged from the galls.
Cultural Practices
Provide oaks with proper environmental conditions and good cultural care. No other management is recommended because gall wasps can be very difficult to control, and usually they do not seriously harm oaks.
Biological Control
There are natural predators to the gall wasp but they are usually ineffective and completely eradicating them.
Chemical Treatment
None have been shown to be effective.
Bag Worms
Evergreen bagworm, is a detrimental insect pest to landscape plants that often escapes detection until there is significant plant damage. Bagworms feed on many plant species, though are more prevalent and damaging on conifers. Most bagworm infestations result from stressed plants and a lack of management of lower, more manageable, populations. The telltale sign of a bagworm is the ice-cream cone shaped “bag” or pupal case. Bags are often mistaken as coniferous reproductive cones or other plant structures because the insect uses leaves or needles to construct the cases. This protective structure is used mainly by the larval stage but is also used to overwinter eggs. The bags range in size from ¼ inch to over 2 inches, as they enlarge as the caterpillar grows and matures. Mating occurs within the bag and 500 to 1,000 eggs are laid during fall before the female dies. These eggs will hatch in late spring to early summer.
Cultural Practices
One of the most reliable control methods, especially for low bagworm populations, is hand-picking. Since bagworms can feed and retreat into the bag multiple times, physically removing the bags eliminates the pest immediately. Bags can be picked off burned. Do not add to a compost pile. If trees are too tall to hand-pick the entire tree, removing as many as possible is still a good way to significantly reduce the population in one step. Handpicking should be done in fall, winter, or early spring prior to the eggs hatching to be most effective.
Biological Control
The main biological control for caterpillars is Bacillus thuringiensis, subsp. Kurstaki, also known as Bt. This bacterial spore suspension is sprayed on the landscape plants and then the spores are ingested by the insect as they feed on conifer needles. The bacterium then releases a toxin inside the insect’s gut, killing it within a few days. Most gardeners are always looking for a safe preventative treatment, and Bt would qualify as one of the most effective, if applied every 7 to 14 days during the late spring while eggs are hatching. Many naturally occurring predators and parasites can be attracted to gardens and landscapes by planting a variety of flowering plants for pollen and nectar. This is an effective means to create a balanced ecosystem.
Chemical Management
Bagworm egg casings are notoriously impervious to sprays, and even the strongest insecticides have trouble penetrating the lining. For effective control, insecticide applications should be made prior to bags being attached onto landscape plants. One of the safer chemical control choices are products containing the active ingredient spinosad. This active ingredient is derived from the Actinomycete bacterium, Saccharopolyspora spinosa. This insecticide provides good control and is less hazardous to pollinators and other beneficial insects, though it is not completely harmless. Spinosad takes about 3 to 7 days from treatment to kill the caterpillar, and repeat applications may necessary.
Japanese Beetles
Japanese beetles can be present during late spring and early summer. Japanese beetle adults are metallic green or greenish bronze with reddish wing covers and several white spots near the abdomen tip and along the sides. They have 6 or 7 small tufts of white hair around the posterior (rear) abdomen, just under the wing covers. Japanese beetles are active during the the day and feed on many species of trees, shrubs and flowers, sometimes causing serious damage to roses, linden trees, grapes and others. After mating, females burrow a few inches into the soil and lay eggs, 40–60 during a summer. The grubs live underground for about a year, feeding on plant roots, molting as they grow. They descend 4–8 feet into the soil to overwinter. When fully grown, in late spring the larvae pupate for a few weeks. They emerge as adults in mid-June and crawl to the surface to fly, mate, and lay eggs. As adults, they live for about two months. They can fly up to 3 miles for food.
They are skeletonizers, feeding only on the soft parts of foliage, leaving only a lacy network of veins behind. Native to Japan, this insect is a serious pest of lawns, gardens, and crops in North America. They have multiyear population booms, which usually subside as natural predators and diseases arise to bring their numbers back into balance.
Cultural Practices
Hand-picking is an effective and environmentally friendly method of control on low-growing trees and plants. By targeting early or light infestations, you may prevent further feeding damage by limiting the amount of floral scents emitted by the host plant. Shake stems and branches with Japanese beetles over a bucket of soapy water. Beetles are typically sluggish and easy to capture early in the morning.
Be cautious when using Japanese beetle traps as they are very effective at bringing beetles in from areas well outside of your yard. Traps don’t catch all the beetles they attract, so nearby plants may be heavily damaged by feeding. If you decide to use a trap, place it at least 100 feet away from plants you want to protect. Dispose of trapped beetles frequently by dropping them into a bucket of soapy water.
Biological Control
No biological controls are commercially available for managing adult Japanese beetles. Two products are available for biological control of Japanese beetle grubs in the soil. Neither product is 100% effective.
- Milky spore (milky disease bacteria) is a long-term control technique that may slightly reduce grub populations in 2–3 years. Introduce milky spore into several spots in your yard in a grid pattern. Once in the soil, the spores will be present for many years. Milky spore requires specific temperature and moisture conditions to infect grubs.
- Species of Heterorhabditis and Steinernema nematodes will attack grubs but need to be applied up to three times annually during the grub stage. Soil moisture is critical for nematode survival.
Chemical Management
Neem oil is useful in deterring beetles from feeding if used at the first sign of damage and when infestations are light. These treatments are considered more pollinator-friendly than other insecticides but should still be used with caution.
References
University of California Agriculture and Natural Resources IPM Management
Missouri Botanical Garden
Missouri Department of Conservation
