Photo Gallery of Insects and Mites on Ornamental Plants
Twobanded Japanese weevils are resistant to several insecticides commonly used in the home garden including Sevin, malathion and diazinon. Fortunately they are susceptible to Orthene insecticide which is labeled for home use and has the advantage of being systemic and not very toxic to humans. Commercial growers and landscapers can use the pyrethroids Mavrik, Talstar or Tempo 2 for control of these insects. Ornamentals and Turf Insect Information Note No. 34 provides more information on the biology and control of the twobanded Japanese weevil.
The blackheaded fireworm, Rhopobota naevana, is the immature stage of holly bud moths. These insects overwinter as eggs. In spring the newly-hatched larvae feed on opening buds, but older larvae rolling the leaves and feeding on them cause most of the damage. These caterpillars produce a noticeable amount of silk that holds the leaf together and protects the caterpillar. Mature caterpillars drop from the plant to pupate in the mulch under plants. Moths emerge from the pupal stage in June and lay eggs (one per leaf) on the underside for the second generation. The blackheaded fireworm is considered a general feeder because it also infests apple, cherry, blueberry, holly and other ornamentals. If persons choose to treat these caterpillars with pesticide, they will need to use plenty of pressure by pumping up the sprayer to force the pesticide into the rolls. They may consider using Orthene because of its systemic action although Sevin should work well, too, if the shrubs are sprayed thoroughly. Likewise Mavrik or Talstar will also provide good control if the coverage is thorough.
From time to time, large, brown beetles with conspicuous antennae that buzz around porch lights alarm people. These are the adult stage of grubs called Prionus root borers. These are roundheaded borers that grow to three inches long and feed in the living roots of oak, pecan, chestnut, pear and various other plants. Females lay their eggs in the soil in groups around the bases of trees. Tiny grubs hatch and feed on the bark of roots before they bore in. Over the next three to five years, the grubs bore inside the roots and sometimes completely hollow them out. They also move through the soil from root to root, causing many injuries to the roots. Sometimes shrubbery is killed as the borers cut the plant off from the inside at the ground line. Imidacloprid (Merit) or another soil insecticide should provide some control of Prionus
root borers in the soil. A beetle captured a few years ago laid hundreds of eggs. These beetles are attracted to lights during the summer. Consequently, destroying the adults as they gather at the porch lights or on the window screens at night would have to have some impact on the local population. Since they are attracted to lights, it would probably help to hang a lighted electric bulb in the yard a short distance above a pan of soapy water. Many kinds of insect pests are attracted to lights and will drown as they fly into the reflection of the bulb in the water. The water will have to be changed on a fairly regular basis to avoid an unpleasant mess. Some entomologists think this method is as effective as the bug zapper lamps for controlling insects at night.
North Carolina has many species of leafhoppers, and leafhoppers are sometimes quite abundant. Aside from their direct damage to ornamental plants, leafhoppers are also important because of the diseases they transmit to shade trees, fruit trees, vines and even grasses! Unfortunately, except for a few really distinctive types of leafhoppers, the rest can be quite difficult to identify to species. On most of the samples we receive, leafhoppers are represented only by their injury (the tiny chlorotic spots) because leafhoppers are skittish and agile. They often jump from plant samples as the samples are cut. Naturalis-O, a naturally occurring parasitic fungus, is labeled for leafhopper control. The active ingredient is Beauveria bassiana, a fungus that only infects insects. Neem oil extract, Triact, is also labeled as are soap and pyrethrins. Orthene is another choice for leafhopper control as it is somewhat systemic, it is effective as a contact insecticide, and it is relatively safe for people to use. However, because leafhoppers migrate readily from place to place, it is almost impossible to get long-term control without a lot of spraying! The North Carolina Cooperative Extension Service publication Insect and Related Pests of Flowers and Foliage Plants provides information on one of our most abundant leafhoppers, the potato leafhopper.
The following information was obtained when scouting container nurseries in Wake County, North Carolina. Pest development will be more advanced south and east of Wake County, and less advanced north and west of the county.
Wild carrot (Daucus carota) and horseweed (Conyza canadensis) are in flower. Remove plants from the nursery before they go to seed. Horseweed, in particular, is a common weed in overwintered nursery stock and in field plantings. (References: http://www.auburn.edu/~deancar/wfnotes/q_a_lace.htm and http://www.ipm.ucdavis.edu/PMG/WEEDS/horseweed.html).
Summer annual weeds continue to germinate. Crabgrass, eclipta, phyllanthus, spurge, and others are germinating and growing rapidly after emergence. These weeds can have several generations per year; we are into the second (or third) now. The longer these weeds are allowed to remain in pots or fields, the greater the seed set and the greater the future weed pressure.
Based on this summer's research, the following preemergence herbicides are ranked by their efficacy on Eclipta:
Good: OH2, Rout, Regal OO
Fair: Surflan, Snapshot, Gallery
Poor: Factor, Ronstar, RegalStar, Pennant, PrePair
Summer thundershowers and heavy irrigation during very hot weather can wash away some of the preemergence herbicides. Watch for weed emergence -- if species are coming up that should be controlled by your preemergence herbicide program, your next application may need to be applied before it is called for on the calendar schedule.
Leafminers: Magnolia leafminers (Phyllocnistis magnoliella) were found on Sweet Bay magnolia. As they grow these tiny leafminer caterpillars burrow through the leaf tissue. This burrowing causes the formation of unsightly tunnels, which are visible on the underside of the leaf. Any leaf tissue beyond these tunnels will eventually die. (Reference: http://ipm-www.ncsu.edu/insect_notes/Ornamentals_and_Turf/not09.html)
Azalea Lace Bugs: Keep an eye out for a bronze stippling on the leaf surface of azaleas. Continue to monitor plants in July for second generation nymphs. (Reference: http://www.ces.ncsu.edu/Insects/O&T/shrubs/ort039e/ort039e.htm)
Japanese beetles: Japanese beetles are still flying (and eating). Peak emergence of Japanese beetles occurs in July so continue scouting susceptible species such as roses, crape myrtle, grapes and fruit trees for damage. Watch for the lacy network of leaf veins left by adult feeding. (Reference: http://www.ces.ncsu.edu/Insects/O&T/flowers/orn_t44/not44.html)
Many caterpillars are now showing up in turfgrass across the state. These include armyworms, cutworms, and sod webworms. Inspect suspicious-looking brown areas and use a soapy water drench (two tablespoons of liquid dishwashing detergent in two gallons of water per square yard) to bring caterpillars out of hiding. Chinch bugs are beginning to damage St. Augustinegrass in a few isolated areas. Look for damage from this pest to begin to appear following the hot weather.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on July 12, 1999 by Stephen J. Toth, Jr.