Kansas State University

–by Raymond Cloyd – Horticultural Entomology

Squash bug, Anasa tristis, females have laid eggs and various stages of the nymphs are present feeding on squash and pumpkin leaves. Squash bug adults are flattened and 1/2 to 3/4 of an inch in length. Adults are dark-brown and have wings with brown-to-black and orange markings along the outer edge of the body (Figure 1). Females lay red-orange eggs on the leaf underside and top of leaves. Nymphs emerge (eclose) from the eggs in seven to 14 days and undergo five instars (stages between each molt) before maturing to adults. First instar nymphs that emerge from eggs have a red head and thorax (middle section) and pale-green abdomen (Figure 2). Second instar nymphs have a black head and thorax and a pale-green abdomen (Figure 3).

Figure 1. Squash bug adult (Raymond Cloyd, KSU)

Figure 2. Young squash bug nymphs (Raymond Cloyd, KSU)

Figure 3. Young squash bug nymphs (Raymond Cloyd, KSU)

Nymphs tend to gather near the eggs after emerging. Older nymphs (3^rd to 5^th instar) are gray (Figure 4) and tend to distribute themselves over the entire plant (Figure 5). Nymphs are 3/16 of an inch long and cannot fly because they do not have fully-developed wings.

Squash bug nymphs and adults use their piercing-sucking mouthparts to withdraw plant fluids from leaves, stems, vines, and fruits. Damage to leaves appears as small, yellow specks that eventually turn brown (Figure 6).

Figure 4. Older squash bug nymphs (Raymond Cloyd, KSU)

Figure 5. Older squash bug nymphs on the stem (Raymond Cloyd, KSU)

Figure 6. Feeding damage caused by squash bug (Raymond Cloyd, KSU)

Below are the plant protection strategies that you can implement to mitigate problems with squash bugs and prevent subsequent plant damage.

1. Check plants for the presence of eggs, nymphs, and adults on leaf undersides at least once per week during the growing season.
2. Destroy eggs, and remove (handpick) nymphs and adults, placing them into a container with soapy water to kill them. Handpick every three to four days.
3. Place a floating row cover over plants to protect them from squash bug nymphs and adults.
4. Position wooden boards throughout the garden, turning them over daily to collect squash bugs hiding underneath. You can kill the squash bugs by placing into a container of soapy water.
5. Apply a contact insecticide when the nymphs are present. The smaller nymphs are easier to kill than the larger nymphs. Contact insecticides are less effective against adult squash bugs because adults have a thickened waxy cuticle (skin) that insecticides cannot adhere to and penetrate. Adults are also protected from insecticide sprays by the leafy plant canopy. Weekly applications of contact insecticides may be required to maintain populations below levels that will prevent plant damage. Thorough coverage of the leaf undersides is important to manage squash bug populations.

For more information on how to manage squash bug populations refer to the following extension publication:

Squash Bug (MF3308 July 2016)

https://www.bookstore.ksre.ksu.edu/pubs/MF3308.pdf

–by Raymond Cloyd, Horticultural Entomologist

Japanese beetle, Popilla japonica, adults are present throughout Kansas feeding on many plants in landscapes and gardens including: roses (Rosa spp), littleleaf linden (Tilia cordata), oak (Quercus spp.), Virginia creeper (Parthenocissus quinquefolia), crabapple (Malus spp.), and grape (Vitis vinifera). The plant protection strategies that need to be implemented to manage Japanese beetle adult populations are limited and have been for many years. The primary stra tegy involves spraying contact insecticides to kill adults, which will reduce plant damage.

Japanese beetle adults are 3/8 to 1/2 of an inch long, metallic green with coppery-brown wing covers, and approximately 14 tufts of white hair along the edge of the abdomen (Figure 1).

Figure 1. Japanese Beetle Adults Feeding On Leaf (Raymond Cloyd, KSU)

Japanese beetle adults 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, an d grapes (Figure 2).

Figure 2. Japanese Beetle Adults Feeding On Grape Leaf (Raymond Cloyd, KSU)

Japanese beetle adults produce aggregation pheromones that attract males and females to the same feeding location, which enhances mating (Figure 3).

Figure 3. Japanese Beetle Adult Males And Females Mating (Raymond Cloyd, KSU)

Adults can fly up to five miles to locate a host plant; however, adults 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, in general, do not feed on tissue between leaf veins. Consequently, feeding on tissue between the leaf veins causes the lace-like or skeletonized appearance (Figure 4).

Figure 4. Japanese Beetle Adult Feeding Damage On Leaf (Raymond Cloyd, KSU)

Adults are primarily active on warm days, feeding on plants exposed to full sun, which may be 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 as food sources are depleted. Japanese beetle adults will also feed on flowers (Figure 5),

Figure 5. Japanese Beetle Adults Feeding On Rose Flower (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 includes proper irrigation, fertility, mulching, and pruning that are important in minimizing plant stress, which may decrease susceptibility to Japanese beetle adult feeding. Furthermore, removing weeds attractive to Japanese beetle adults such as smartweed, Polygonum spp., may help to alleviate infestations. Physical control such as hand removing or collecting Japanese beetle adults before populations are extensive may minimize plant damage. The best time to remove or collect adults is in the morning when ambient air temperatures are typically cooler. Adults can be 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, fall into the liquid, and are subsequently killed. The procedure may reduce plant damage when conducted daily or every-other-day, for up to four weeks.

The use of Japanese beetle traps in landscapes or gardens is not recommended since the floral lure and synthetically derived sex pheromone (Figure 6)

Figure 6. Floral Food Lure (Bottom) And Synthetically-Derived Sex Pheromone (Top) Associated With Japanese Beetle Trap (Raymond Cloyd, KSU)

may attract more adults into an area than would occur normally. In addition, Japanese beetle adults ma y feed on plants before reaching the traps, which increases potential plant damage.

Spray applications of contact insecticides will kill Japanese beetle adults. However, repeat applications are required, especially when high numbers of adults are present. A list of active ingredients in commercially available insecticide products for use against Japanese beetle adults is presented in Table 1. It is important to understand that these insecticides may also directly harm many natural enemies (parasitoids and predators) and repeated use can lead to outbreaks of other pests including the twospotted spider mite, Tetranychus urticae. Furthermore, these insecticides are directly harmful to pollinators including honey bees and bumble bees. Therefore, apply insecticides in the early morning or late evening when bees are less active.

For more information on how to manage Japanese beetle refer to the following extension

publication:

Japanese Beetle: Insect Pest of Horticultural Plants and Turfgrass (MF3488 March 2020)

https://www.bookstore.ksre.ksu.edu/pubs/MF3488.pdf

Table 1. Active ingredients in commercially available insecticide products for use against Japanese beetle adults.