Japanese Beetle

Beetle control in the garden is a constant battle during the month of July. They appear in large numbers seeming to eat everything in the vegetable and flower garden. Daily scouting for damaged plants and adult beetles helps win the war against them and salvage the plants. The first line of defense is to identify the enemy. Just which beetle is eating the specific species and is it eating different plants is clue to controlling the different beetles.

The life cycle of all beetles have four stages: egg, larva, pupa and the adult beetle. Japanese, Asiatic garden and Oriental beetles lay eggs on the soil, where they hatch into white grubs and feed on plant roots. Pupation takes place under the soil, too. The adult beetles emerge after pupation, rising out of the soil in large numbers, looking to feed and mate, and then females will lay the next generation of eggs back on to the soil. There is one generation per year for most of the garden pest beetles. The most common garden pest beetles are also lawn pests as white grubs feeding on grass roots, but grubs can also be found in the vegetable and perennial gardens. Control grubs in the lawn by using conventional grub control. Organic options are parasitic nematodes and Bt galleria. Milky spore disease will only kill the Japanese beetle grubs. Bag traps to catch and contain adult beetles are available. They are specific to each variety of beetle and use a pheromone lure as an attractant. Place the trap away from the garden to keep the beetles from finding your plants. The organic options are a good choice for the soils in a vegetable garden. Other natural control measures are already in the environment. Tiphia wasps feed on the grub stage killing them. Hand pick beetles and drop into a container of soapy water. Attract birds to the garden to feed on the beetles by providing lots of perching spots with sticks and plant supports. Place a saucer of water or birdbath in the garden to invite them for a visit and meal. Floating row covers can be used to keep beetles off until plants flower and need pollinators to reach the flowers.

Japanese Beetle in hand

Japanese Beetle

Japanese beetles are cosmopolitan feeders. They have over 300 different host plants, but prefer some over others. Roses, sunflowers and beans are favorites of this metallic green and cooper colored winged beetle. The white grub is C-shaped with a tan head. The adults are active during the day and hide nearby at night.  Japanese beetles were brought to New Jersey accidentally in 1916 from Japan, and have spread up and down the eastern states. They are steadily moving westward. Japanese beetle feeding results in ragged foliage and distorted flowers. They are even known to chew on fruits and vegetables. Their damage can be extensive, especially when there is a large population.

Oriental beetle retry

Oriental Beetle

Oriental beetle is a mottled tan and dark brown beetle, active during the day also. They are native to Asia and are in many eastern states. They feed on a wide range of plants, especially the blossoms. Oriental beetles are most active in the afternoon and early evening before it gets dark.

Asiatic Garden Beetle 2

Asiatic Garden Beetle

Asiatic garden beetle are cinnamon brown in color and a little smaller than Japanese beetles. As the name implies, they are native to Asia, brought here around 1920. These beetles feed at night and hide in the soil below plants during the day. Scraping through the soil below night damaged plants will reveal the sleeping beetles. Flooding the area with a good soaking will also bring them to surface for capturing and killing.

Favorite plants for Asiatic garden beetles  are basil and roses.

 

Squash beetle and damage

Squash Beetle

Squash beetle eggs

Squash Beetle eggs.

Squash beetles are another big pest in my garden. They are yellowish-orange with 14 black spots. Their life cycle is different than the other three beetles mentioned above.  Adults overwinter in leaf litter and under loose tree bark, flying to the garden during the end of June. Squash beetles lay their eggs on the underside of squash, pumpkin and cucumber leaves and hatching out into a yellow, spiny larval grub to feed directly on the leaves. The adult and larval stage can destroy a crop quickly. Monitor daily for adults and turn over leaves to look for eggs which can be crushed or removed with sticky tape. I find clear packing tape and blue painters tape wrapped around my hand with sticky side facing out works well without ripping the leaves. Less eggs means less larva and adults eating the plants.

-Carol Quish

frass on leaf

Frass left on leaf after beetle feeding. Frass is insect poop!

 

 

 

 

Last week, an adult Oriental beetle was spotted on some lettuce in our vegetable garden. This in itself is not really a big deal because, unlike Japanese and Asiatic garden beetles, these adults are not voracious feeders and don’t typically require control. It can be important for a couple of other reasons though, to note the annual emergence of this species. One is that it typically precedes the emergence of the Japanese beetle by 1-2 weeks, so it’s a heads-up to be on the lookout for them. The other is that the larvae or grub stage of the Oriental beetle can cause significant damage to the roots of cool season turfgrasses and some ornamental plants including those in pots.

Adult Oriental beetle on lettuce.  J. Allen photo.

Adult Oriental beetle on lettuce. J. Allen photo.

The adults are 3/8 to 7/16” long and have quite variable color and markings. They can range from light tan to dark brown and many have alternating dark and light line patterns on the wing covers (elytra). After emerging in mid to late June in southern New England, beetles feed and mate. Females lay eggs a few inches deep in moist soil in small groups for a total of 20-30 eggs per individual. If drought conditions prevail, egg-laying may be delayed as long as into September. Grubs hatch 18-24 days later under average temperature and weather conditions and feed on roots and organic matter near the soil surface. As grubs increase in size and grow through three instars or stages, the amount of damage done to host plants increases too. Third instar larvae overwinter deep in the soil (8-17”). They migrate upward and resume feeding when the soil warms in the spring. After feeding for 4-5 weeks, the grubs pupate and transform into adults, completing the annual life cycle.

If you are concerned (or know) that white grubs, the larvae of Oriental, Japanese and several other scarab beetles, are damaging your lawn or other plants, it is important to correctly identify the beetle species for selection of the most effective control strategies. Pheromone traps are available to monitor for the presence of adult male Oriental beetles. Because these traps only attract males, they do not have the potential to increase damage in the area as Japanese beetle traps can. Identification of white grubs to species requires a close look at their little rumps. Using a hand lens, inspect the pattern of ‘hairs’ on the lower side. The Oriental beetle grub has two parallel rows of small hairs down the middle.

How do you know if you have enough grubs to warrant a control product? For Oriental beetle, thresholds of 8-10 grubs per square foot of lawn are suggested. Peel back a one foot square section of turf and check the soil and roots for grubs. White grubs will be in a C shape. They’re going to be most numerous and problematic in sunny areas. Don’t forget about grub identification!

Management strategies include cultural practices, biocontrols and chemical insecticides. For both biocontrol and most chemical products, the early instar or youngest grubs are the most vulnerable and therefore the most easily controlled. More information on these can be found at these links: http://www.beyondpesticides.org/alternatives/factsheets/Grubs.pdf

http://www.ct.gov/caes/cwp/view.asp?a=2815&q=376940

Connecticut claim to fame: The Oriental beetle was first confirmed in the United States here in 1920. It didn’t appear to spread much until around the 1970s. Since then it has expanded its U.S. distribution to include most of the east coast and extending westward to Ohio.

If you need assistance with grub or beetle identification, or control tips, contact the UConn Home & Garden Education Center by phone at 860-486-6271 or by email at ladybug@uconn.edu.

By J. Allen