HPIPM:Western Corn Rootworm SC

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Order	Coleoptera
Suborder	Polyphaga
Infraorder	Cucujiformia
Superfamily	Chrysomeloidea
Family	Chrysomelidae
Subfamily	Galerucinae
Tribe	Luperini
Subtribe	Diabroticina
Genus	Diabrotica

Scientific Name

Diabrotica barberi

Common Name

northern corn rootworm

Author: Whitney S. Cranshaw

Field Biology and Identification

Western corn rootworm adults are 6-8 mm (1/4-5¦/16 inch) long, yellow beetles with black stripes on the outer egdes of the wing covers. Larvae are 12 mm (1/2 inch) long when full grown. They are thin, white, legless larvae with brown head capsules and a brown plate on the last abdominal segment, found in the soil near corn roots.

Adults feed on corn silks and tender leaves from late July to mid-September. They also are attracted to blossoms of some plants, such as squash. Eggs are laid in late summer, and are the overwintering stage. Rootworm larvae are restricted to corn for their development. After hatching in June, the larvae feed on corn roots for about one month before pupating in July. There is one generation per year.

Plant Response and Damage

Under normal, low, densities, silk clipping by adults is not sufficient to decrease kernel set: plants are usually able to compensate for silk loss. Larval feeding cause the greatest damage, by reducing the plant's ability to take up water, deverting food reserves away from the ears, and by weakening the support provided by the root system, thus increasing lodging. Late planting tend to be more at risk, because beetles are more numerous later in the season, and are attracted to the smaller plants, and problems worsen when sweet corn follows a corn crop.

Resistant Varieties

None in sweet corn varieties.

Biological Control

Soils rich in organic matter may increase the populations which support an important natural enemy of rootworm larvae, predatory mites.

Cultural Control

Crop rotation is effective in decreasing rootworm populations since the larval stages can only develop on corn. After hatching, rootworm larva soon starve unless corn is nearby

Chemical Control

Corn Rootworm larvae: when corn is rotated, soil treatments are not needed. Regular spraying that eliminates corn rootworm adults also will eliminate the need for soil treatment the next season. Treatments are banded at planting.

Adults: Most materials labelled for corn earworm will control adult rootworm beetles: when corn earworm treatments are used, rootworm adults are also controlled. When insecticides are not used, adult beetles may develop in very high numbers on later sweet corn plantings. Treatment with insecticides can reduce adult beetle numbers but the beetles actively fly and may reinfest treated areas of a field. Pollination may be disrupted when an average of five or more beetles are present at ear tips

Product List for Western Corn Rootworm:

Insecticide	Product per acre	Remarks
Fortress 2.5GR	6 oz/1000 row ft
Aztec 2.1G­­R	6.7 oz/1000 row ft	A combined organophosphate/pyrethroid product, with activity against cutworms.
Capture 2ER,1	5.12 - 6.4 fl. oz.	1 day. Maximum 0.2 lb (AI)/acre/season.
Counter 15GR	8 (15G) oz/1000 row ft	May be applied banded or in-furrow at-planting or banded at cultivation.
Counter 20CRR	6 (20CR) oz/1000 row ft
Fortress 2.5GR	6 oz/1000 row ft
Lorsban 15G	8 oz/1000 row ft	Has some activity against cutworms.
Lorsban 4E-HF1	2.4 fl oz (30 inch rows)	2 pt per acre, rate per 1000 ft depends on row spacing. Pre-plant, planting time , or cultivation treatments. Has some activity against cutworms.
Mocap 10G	10.5 oz/1000 row ft	Planting time treatment, but avoid contact with seeds to avoid germination losses.
phorateR,2	6 - 8 oz/1000 row ft	Avoid contact with seed.
RRestricted use pesticide 1Labeled for chemigation 2Generic active ingredient, several formulations.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.