Kansas State University

–by Dr. Raymond Cloyd

Insecticidal soaps are classified as biorational or “reduced risk” insecticides and are used in certain situations because they leave minimal residues, are less toxic to humans, and are short-lived in the environment because they degrade rapidly. A soap is a substance derived from the activity of an alkali such as sodium (hard soap) or potassium (soft soap) hydroxide on a fat. In general, fats are a blend of particular fatty acid chain lengths. Soap is a general term for the salts of fatty acids. Soaps may be combined with fish, whale, vegetable, coconut, corn, linseed, or soybean oil. For example, “Green Soap” is a potassium/coconut oil soap that was used widely as a liquid hand soap in public restrooms. It is now available as a hand soap or shampoo, and has been shown to be effective, as an unlabeled insecticide, in controlling soft-bodied insects.

Fig 1. Insecticidal Soap Product (Author–Raymond Cloyd, KSU)

Commercially available insecticidal soaps containing the active ingredient, potassium salts of fatty acids (Figure 1), are used against a variety of soft-bodied insect and mite pests including aphids, scales, mealybugs, thrips, whiteflies, and the twospotted spider mite, Tetranychus urticae. The young life stages (nymphs, larvae, or crawlers) are most susceptible to soap applications. Soaps have minimal activity on beetles and other hard-bodied insects although this is not always the case as certain soaps have been shown to kill hard-bodied insects such as cockroaches. Soaps are effective only when insects or mites mite activity as soap residues degrade rapidly; especially under sunlight (ultraviolet light).

The mode of action of soaps is still not well-documented; however, soaps may kill insect and mite pests in one of three ways. First, soaps may work when fatty acids penetrate through the insect’s outer covering (cuticle) and dissolve or disrupt cell membranes. This interferes with cell integrity causing cells to leak and collapse, destroys respiratory functions, and results in dehydration and death of an insect or mite. Second, soaps may act as insect growth regulators interfering with cellular metabolism and the production of growth hormones during metamorphosis. Third, soaps may block the spiracles (breathing pores), which disrupts normal respiration.

There are varieties of fatty acids; however, only certain fatty acids have insecticidal properties, which is associated with the length of the carbon-based fatty acid chains. Most soaps with insect and mite activity are composed of long chain fatty acids (10 or 18-carbon chains) whereas shorter chain fatty acids (9-carbon chains or less) have herbicidal properties, so using materials that have short chain fatty acids can kill plants. For example, oleic acid, an 18-chain carbon fatty acid, that is present in olive oil and other vegetable oils, is very effective as an insecticidal soap.

Insecticidal soaps may directly and indirectly harm beneficial insects and mites. For example, one study showed that insecticidal soap was directly harmful to the predatory mite, Phytoseiulus persimilis. Another study reported that applying an insecticidal soap at a 4% application rate resulted in 80 to 99% mortality of the predatory mite, Neoseiulus (=Amblyseius) cucumeris.

Fig 2. Dishwashing Liquids (Author–Raymond Cloyd, KSU)

There is a general misconception that any soap or laundry detergent can be used as an insecticide. This is not true. As already mentioned, only a few select soaps have insecticidal properties, but many common household soaps, laundry detergents, and dishwashing liquids including Palmolive^Ò, Dawn^Ò, Ivory^Ò, and Joy^Ò (Figure 2), which are unlabeled insecticides, may have some activity on soft-bodied insects when applied at a 1% or 2% aqueous solution. However, reliability is less predictable than soaps (potassium salts of fatty acids) that are formulated and registered as insecticides.

Examples of various dishwashing liquids on insect and mite pests are provided below:

1) Palmolive^Ò, Dawn^Ò, Joy^Ò, Ivory^Ò, and Dove^Ò reduced the numbers of sweet potato whitefly,

Bemisia tabaci; green peach aphid, Myzus persicae; cabbage aphid, Brevicoryne

brassicae; and twospotted spider mite on a variety of vegetable crops.

2) Dawn Ultra^Ò dishwashing liquid was effective on the German cockroach, Blattella

germanica, causing 100% mortality.

3) Ivory^Ò liquid dishwashing soap applied at 0.4 to 3.0% concentrations controlled spider mites,

aphids and psyllids.

4) Ivory^Ò liquid dishwashing soap at 1 and 2% concentrations was effective in controlling

aphids, spider mites, psyllids, and thrips.

5) New Day^Ò dishwashing detergent applied at 2.0 ml/L provided 95% mortality of silverleaf

whitefly, Bemisia argentifolii (=Bemisia tabaci biotype B), nymphs.

6) Ivory^Ò liquid dishwashing soap and Tide^Ò detergent were effective in reducing populations of

aphids; citrus red mite, Phyllocoptruta oleivora; psyllids; and greenhouse thrips, Heliothrips

haemorrhoidalis, on landscape plants.

However, dishwashing liquids and laundry detergents are primarily designed to dissolve grease from dishes and clean clothes; not kill insects and mites. The type of fatty acid, length of the carbon-based fatty acid chain, and concentration in many laundry and dish soaps is not known. In addition, the insecticidal effectiveness of these products may be compromised by the presence of coloring agents or perfumes, which often times leads to inconsistent results. Certain laundry and dish soaps will precipitate or solidify in “hard” water, thus reducing their effectiveness. Furthermore, these materials may cause plant injury by dissolving the waxy cuticle on the leaf surface. Registered, commercially available insecticidal soaps are less likely to dissolve plant waxes than household cleaning products. In addition, plants with pubescent (hairy) leaves may be more susceptible to injury from dishwashing liquids and detergents.

Dishwashing liquids and laundry detergents, like insecticidal soaps, lack any residual activity and thus more frequent applications are required. However, too many applications will harm certain plant types. Moreover, detergents are chemically different from soaps and may cause phytotoxicity (plant injury). In fact, many hand soaps are not necessarily pure fatty acids. Most importantly, these solutions are not registered insecticides. Soap companies do not intend for their products to be used as insecticides as they have not gone through the Environmental Protection Agency (EPA) registration process.

Although some dishwashing liquids and laundry soaps are active on insect and mite pests, they should not be used because they are not registered insecticides. Even more important is that a pest control company will generally stand behind a product when there is a problem. However, if a dish or laundry soap is used and plants are injured—there is no recourse.

–by Frannie Miller and Sarah Zukoff

The Asian Giant Hornet has created a buzz, since being found in the state of Washington/Canada border. These insects have been nicknamed “murder hornets” by the news media. It is important to remember none of these hornets have been found in the state of Kansas. These impressive hornets are similar to our US hornets in that they are not much more aggressive towards people unless their nest or food source is threatened. They do differ however by having a very potent, painful sting. Multiple stings by the Asian giant hornet would warrant medical attention even if the person were not allergic. The hornets build their nests each year underground in abandoned animal burrows or around the roots of trees making the nests hard to detect.

One cause for concern regarding their presence in the United States is their predatory nature towards honeybees. This hornet could devastate European honeybee colonies who have developed no defense mechanisms. Individual guard bees are no contest for the much larger hornet. Groups of hornets can go into a “slaughter phase” where they decimate an entire hive of bees. Then they will occupy the hive and feast upon the honeybee brood.

Japanese honey bees have developed a defensive mechanism to deal with the threat. They form a mass around the hornet and buzz their wings to create heat. The generated heat kills the hornet because the honeybees can survive at higher temperatures. Basically, a good depiction might be the thought of sticking the hornet in a honeybee microwave as illustrated in the cartoon.

Sadly, in all of the hysteria, many of our look-alike pollinators have been mistaken for the Asian Giant Hornet. Reports of panic killing of bumble bees, wasps, and others have been observed on various news and social media outlets.

The Asian Giant Hornet prefers mountainous valleys and has never been recorded from plains regions of any country. It has not been found in Kansas.

–by Frannie Miller

Harlequin Bug – This is an image of a Harlequin Bug. It feeds on cabbage, broccoli, cauliflower and kale. They injure the plants by sucking the plant juices causing white stipples on the leaves. In small plantings, one good way to control them may be by hand picking the adults and crushing the egg masses. If you want to find out more information about their life cycle or controls consult the Harlequin Buy publication at: https://bookstore.ksre.ksu.edu/pubs/MF3135.pdf

–by Dr. Raymond Cloyd

                Insect and Mite Pests of Vegetable Gardens (MF3480 February 2020)

This publication explains how to detect potential problems and how to identify pests in vegetable gardens based on the type of plant damage. A discussion of pest life cycles provides information that can be used to select appropriate plant protection strategies.

https://bookstore.ksre.ksu.edu/Item.aspx?catId=524&pubId=22539

–by Dr. Raymond Cloyd

The recent hot weather we are experiencing throughout Kansas is conducive to the development of the twospotted spider mite, Tetranychus urticae (Figure 1), resulting in extensive feeding damage to the leaves of horticultural plants in gardens and landscapes (Figures 2 and 3). Twospotted spider mite is a warm-weather mite with populations commonly active from late spring through early fall. Summer temperatures allow twospotted spider mite females to reproduce rapidly, which helps to overwhelm natural enemy (e.g. predators) populations by producing multiple generations throughout the season.

Fig 1. Close-up of twospotted spider mite adults.

Fig 2. Twospotted spider mite feeding damage on euonymus bush leaves (Auth–Raymond Cloyd, KSU)

Fig 3. Twospotted spider mite feeding damage on tomato leaves (Auth–Raymond Cloyd, KSU)

The management of twospotted spider mite populations involves maintaining plant health by avoiding ‘stress,’ implementing sanitation practices, and/or using pesticides with miticidal activity (miticides/acaricides). First, prevent plants from experiencing moisture ‘stress’ by maintaining proper watering and mulching practices, which will be helpful in minimizing potential problems with twospotted spider mite populations. For instance, inadequate moisture or over fertilizing plants, especially with water-soluble nitrogen-based fertilizers, can enhance development and reproduction of twospotted spider mites.

It is important to monitor for twospotted spider mite populations regularly by shaking plant parts (e.g. leaves, branches, or twigs) onto a clipboard with a white sheet of paper, and then look for the mites crawling around (you can actually see the mites). You can crush the mites on the white sheet of paper to determine if they are a pest or not. For example, plant-feeding spider mites typically leave a green streak when crushed whereas predatory mites leave a red streak.

A quick and effective method of managing twospotted spider mite populations is applying a forceful water spray throughout the plant canopy at least twice per week during the season. Forceful water sprays will dislodge eggs and the motile life stages (larvae, nymphs, and adults). Be sure to direct forceful water sprays toward the leaf undersides where all life stages (eggs, nymphs, larvae, and adults) of the twospotted spider mite are located. The removal of plant debris and weeds eliminates alternative hosts and overwintering sites.

There are a number of pesticides with miticidal activity available to professionals for suppression of twospotted spider mite populations outdoors, including: abamectin (Avid), acequinocyl (Shuttle), bifenazate (Floramite), etoxazole (TetraSan), hexythiazox (Hexygon), potassium salts of fatty acids (M-Pede), and horticultural oils (petroleum, mineral, or neem-based). Homeowners do not have as many options. In fact, the only “true miticide” still available is hexakis or fenbutatin-oxide, however, this active ingredient cannot be purchased alone as the active ingredient is typically formulated with another pesticide (insecticide) such as acephate (Orthene). However, homeowners can apply commercially available insecticidal soaps (potassium salts of fatty acids) or horticultural oils. Always read the label and apply miticides before twospotted spider mite populations are extensive and causing damage. Moreover, be sure to rotate miticides with different modes of action to avoid twospotted spider mite populations developing resistance. If possible, target ‘hot spots’ or localized infestations of twospotted spider mites, which will reduce the potential for resistance developing. Be sure to thoroughly cover all plant parts with spray applications; especially when using pesticides with contact activity. Some miticides such as abamectin (Avid) and etoxazole (TetraSan) have translaminar activity, which means the material penetrates into leaf tissues and forms a reservoir of active ingredient within the leaf. This provides residual activity even after spray residues have dried. Mites that feed on leaves will ingest a lethal concentration of the active ingredient and be killed.

It is important to note that many pesticides used to suppress other insect pests encountered on plants in landscapes and gardens may be harmful to the natural enemies of twospotted spider mite; consequently, resulting in an inadvertent increase in twospotted spider mite populations or secondary pest outbreaks.

–by Dr. Raymond Cloyd

Green June Beetles: lots still flying around. This has been one of the best…or worst years…depending on your perspective.

Japanese Beetle Adults: many are feeding on fruit trees and roses.

Bagworms: time is running-out in regards to applying insecticides…you have about two to three more weeks…and then it is too late.

Mosquitoes: with all the rain and moist conditions, mosquitoes (adults) are very prevalent.

Milkweed Aphids: many milkweed plants are literally covered with the milkweed aphid. Simply use a forceful water spray to dislodge them from plants.

Squash Bugs: eggs have hatched and nymphs are looking for suitable feeding sites…on the leaf underside.

–by Dr. Raymond Cloyd

We have a new extension publication available entitled, Scale Insect Pests

This new extension publication provides information on the biology, scale types, plant damage, and offers strategies for managing specific types of scales. There are color images of the scale insect pests found in Kansas and surrounding states. The extension publication is available from the following website:

https://www.bookstore.ksre.ksu.edu/pubs/MF3457.pdf

— by Dr. Raymond Cloyd

Japanese beetle, Popilla japonica, adults are present in most regions of Kansas feeding on different plant species, including: roses, Rosa spp.; littleleaf linden, Tilia cordata; and Virginia creeper, Parthenocissus quinquefolia, among many other plant species. The ways to manage populations of the adult stage of Japanese beetle are limited, and have been for many years, with the use of insecticides still being the primary strategy. Japanese beetle adults are one of the most destructive insect pests of horticultural plants in landscapes and gardens. Furthermore, the larva or grub is a turfgrass insect pest in home lawns, commercial settings, and golf courses.

Japanese beetle adults are 9/16 of an inch long, metallic green with coppery-brown wing covers, and about 14 tufts of white hair are present along the edge of the abdomen (Figure 1).

Fig 1. Japanese Beetle Adults Feeding On Leaf (Auth–Raymond Cloyd, KSU)

Adult Japanese beetles emerge from the soil and live up to 45 days feeding on plants over a four-to-six-week period. Adults feed on many horticultural plants including: trees, shrubs, vines, herbaceous annual and perennials, vegetables, fruits, and of course—roses. Plant placement in the landscape and the volatiles emitted by plants are factors that affect adult acceptance. In addition, Japanese beetle adults produce aggregation pheromones that attract males and females to the same feeding location. Adults can fly up to five miles to locate a host plant; however, they tend to only fly short distances to feed and for females to lay eggs.

Japanese beetle adults feed through the upper leaf surface (epidermis) and leaf center (mesophyll), leaving the lower epidermis intact. Adults avoid feeding on tissue between leaf veins, resulting in leaves appearing lace-like or skeletonized (Figure 2).

Fig 2 Japanese Beetle Adult Feeding Damage On Leaf (Auth–Raymond Cloyd, KSU)

They are most active during warm days, feeding on plants exposed to full sun throughout the day, which is likely why roses are a susceptible host plant because roses require at least six hours of direct sunlight to flower. Japanese beetle adults start feeding at the top of plants, migrating downward after depleting food sources. Japanese beetle adults will also feed on flowers (Figure 3),

Fig 3. Japanese Beetle Adults Feeding On Rose Flower (Auth–Raymond Cloyd, KSU)

chewing holes in flower buds, which prevents flowers from opening or causes petals to fall prematurely.

Managing Japanese beetle adult populations involves implementing a variety of plant protection strategies, including: cultural, physical, and applying insecticides. Cultural control is affiliated with maintaining healthy plants through proper irrigation, fertility, mulching, and pruning, which are important in minimizing ‘stress’, and may possibly decrease susceptibility. Moreover, removing weeds that are attractive to Japanese beetle adults such as smartweed (Polygonum spp.) may help to reduce infestations. Physical control involves hand-picking or collecting Japanese beetle adults from plants before populations are extensive. The best time to hand-pick or collect adults is in the morning when ambient air temperatures are typically ‘cooler.’ Adults can be easily collected by placing a wide-mouthed jar or bucket containing rubbing alcohol (70% isopropyl alcohol) or soapy water underneath each adult, and then touching them. Adults that are disturbed fold their legs perpendicular to the body, and fall into the liquid and are subsequently killed. This procedure, when conducted daily or every-other-day, for at least three weeks, particularly after adults emerge, may substantially reduce plant damage. A study reported that collecting Japanese beetle adults daily at 7:00 pm had the greatest impact on populations and reduced subsequent damage.

In general, the use of Japanese beetle traps (Figure 4) in a landscape or garden is not recommended since the floral lure and synthetically-derived sex pheromone may attract more adults into an area than would ‘normally’ occur. Japanese beetle adults may also feed on plants before reaching the traps, which increases potential damage.

Spray applications of contact insecticides will kill Japanese beetle adults. However, repeat applications are required; especially when populations are excessive. Several pyrethroid-based insecticides; such as those containing permethrin (Sevin^®), bifenthrin or cyfluthrin as the active ingredient, will suppress Japanese beetle adult populations. However, most of these insecticides will also directly harm many natural enemies (parasitoids and predators) and continual use will result in secondary pest outbreaks of other pests including the twospotted spider mite, Tetranychus urticae. In addition, these insecticides are directly harmful to honey bees and bumble bees. Therefore, applications should be conducted in the early morning or late evening when bees are less active. In general, systemic insecticides are not effective against Japanese beetle adults because they have to feed on leaves and consume lethal concentrations of the active ingredient. If extensive populations are present, plant damage can still occur.

PHOTO NOT AVAILABLE

The battle against Japanese beetle adults requires diligence, patience, and persistence, to prevent adults from causing substantial damage to plants in landscapes and gardens.