S121 Identifying Caterpillars in Corn and Sorghum
Total Page:16
File Type:pdf, Size:1020Kb
Identifying aterpillar in Corn and Sorghum Gerald E. Wilde, H. Leroy Brooks, and Kermit O. Bell INTRODUCTION aterpillars (the larvae or immature stages of moths and butterflies) To carry out the sequence of steps in identification, begin at the first are among the more important pests of field crops. Proper identifica- illustrations for the crop from which the caterpillar was collected and decide tion is necessary for good management of these insects. This factsheet is designed which alternative fits the specimen best. You need to magnify some to help you identify the common caterpillars collected on corn and sorghum. characteristics 10-20X with a hand lens or other means. Each choice is The identifying characters used are found on full-grown or nearly full-grown illustrated by one or more drawings of the characteristics described. Defini- caterpillars and may not occur on newly hatched or young caterpillars. Also, to tions of terms used are given to help you use the descriptions, and the labeled make the factsheet easier to use, some of the less common soil-inhabiting cut- drawing of a caterpillar in Figure 1 will help you become familiar with a worms are omitted. For their identification, you should refer to other publica- specimen. tions (Rings and Musick 1976; Capinera 1986). Loopers can be identified to When you reach a point where you identify a caterpillar, go to the pho- species using Eichlin and Cunningham (1969). tograph for that species and its description. If the picture and description fit Caterpillars can be separated from the immatures or larvae of other groups the caterpillar you are looking at, the identification is probably correct. If such as beetles by their prolegs (with hooks) on abdominal segments 3 to 6 and the picture and description do not fit the caterpillar, you may have misidentified 10, but the prolegs may be absent on abdominal segments 3 and 4 (see Fig. 1). the specimen or it may be a species not included in this factsheet. The char- The only larvae closely resembling them are those of some sawflies, which usu- acteristics used in this factsheet apply to both live and preserved caterpillars, ally have prolegs on all abdominal segments, but no hooks are present on the but body color characteristics given in the description do not apply to alcohol- underside of the prolegs. preserved specimens. Kansas State University Agricultural Experiment Station and Cooperative Extension Service side view PRESERVATION OF SPECIMENS ou can preserve specimens collected in the field for future identification Yin two ways. The best way is to put live caterpillars into boiling water 1 2 3 4 for 3 minutes. Then let them cool and put them into 70% ethyl alcohol or 4 pairs of prolegs on abdomen, rubbing alcohol. Another less desirable method is to put live caterpillars in sorghum head. directly into 70% ethyl alcohol or rubbing alcohol. This results in 1 2 3 4 5 Sorghum Webworm discoloration and makes identification more difficult. (Photo 10) 5 pairs of prolegs on abdomen. SUMMARY side view his fact sheet should allow you to identify caterpillars collected from Long hairs present on body T corn and sorghum. If you are unable to do so or think you have a Short hairs segments. species not included in the fact sheet, ask your local or state research and present on body extension personnel for assistance. segments. REFERENCES Capinera, J.L. 1986. Field key for identification of caterpillars found on side view field and vegetable crops in Colorado. Bull. 535A, Coop. Ext. Serv., Colorado State Univ., Fort Collins, 13 pp. O’Day, M., A. Becker, A. Keaster, L. Kabrick, and K. Steffey. 1998. Corn insect pests: A diagnostic guide. Manual 166, Outreach & Ext., Univ. Missouri, Columbia, 48 pp. Sparse covering of Thick covering of long hairs on body. long hairs on body. Steffey, K.L., M.E. Rice, J. All, D.A. Andow, M.E. Gray, and J.W. Van Cattail Caterpillar Woolybear Duyn (eds.). 1999. Handbook of corn insects. Ent. Soc. Amer., (Photo 3) (Photo 16) Landham, MD, 164 pp. Contribution no. 99-488-E from the Kansas Agricultural Experiment Station. bottom Hooks on view of Head 1st Abdominal Segment bottom of OR proleg prolegs in Thorax Abdomen Hooks on almost bottom of complete 1 2 3 4 5 6 7 8 circle. 9 prolegs in 10 complete Hooks on bottom of prolegs circle. in half circle or curved band. Prothorax Metathorax Prolegs Mesothorax Hair side view Fig. 1. Side view of caterpillar showing structures used in fact sheet. DEFINITIONS Abdomen—Portion of the insect behind the true leg-bearing segments. Head dark brown. Usually 9 or 10 abdominal segments are apparent on caterpillars. European Corn Borer Head light brown. Breathing pore—Structure through which caterpillar breathes. Located (Photo 6) Webworm (Photo 14) on prothorax and segments 1-8 of abdomen. u opea Co o e g top view Larva—Immature growing form quite different in appearance than adults Body with some Body with no color, with of the same species. color; V-shaped or without distinct spots; sutures on top of V-shaped sutures on top Mesothorax—Second segment behind the head. It has a pair of true legs. head almost meet. of head widely separated. Metathorax—Third segment behind the head. It has a pair of true legs. Lesser Cornstalk Southwestern Corn Borer (Photo 8) Borer (Photo 11) Microspines—Numerous tiny spines or thorns on the skins of some larvae. Visible ONLY with magnification, best at 20X or more. side view Proleg—A fleshy leg-like projection found on the underside of some abdominal segments of caterpillars. Tiny microspines on back No tiny Prothorax—The first body segment behind the head. It bears the first and side between hairs, microspines on magnification necessary. pair of true legs and a breathing pore on each side. back and side Corn Earworm between hairs. Reticulation—Pattern of narrow lines looking like threads of a net. (Photo 4) Segment—A portion of an insect separated from adjacent, similar parts by an indentation. The head usually appears as one segment, the next three segments make up the thorax, and the last several segments constitute the abdomen. Suture—A dividing line or crease separating parts of an insect’s surface. Thorax—The parts of an insect just behind its head and consisting of three leg-bearing segments. Distinct spot 4 or more distinct whitish or yellowish above breathing spots down center of back. pore on first Variegated Cutworm DESCRIPTIONS OF COMMON CATERPILLARS abdominal (Photo 13) ON CORN AND SORGHUM segment. Yellowstriped Double row of triangular dark No distinct Armyworm—Body generally greenish to greenish-brown with light stripes Armyworm spots on back below which runs spots as on sides and back; each proleg with a brownish or dark band on outer side. (Photo 17) a whitish or yellowish line. described in Head with reticulation. Mature length 1 1/2 inches. Yellowstriped Armyworm any figures Black cutworm—Body greasy gray to brown, lighter on underside; skin (Photo 17) to the left. with irregularly sized granular structures visible under magnification. Head brown with heavy dark markings and some reticulation. Mature length top view 1 1/2 inches. OR OR Cattail caterpillar—Body with moderately dense long hairs and usually with some yellowish-orange to orange markings. Head brown with dark OR spots. Usually found late in season. Mature length 1 3/4 inches. Corn earworm—Body usually with stripes; colors highly variable, with V-shaped sutures on top of head meet or almost meet. tints ranging from reddish-brown to yellow to green; dark tint in stripes V-shaped sutures on top of due to presence of tiny, dense, dark microspines or thorn-like projections head widely separated. of the skin; presence of microspines separates the corn earworm from other caterpillars. Head yellowish without spots. Mature length 1 1/2 inches. Dingy cutworm—Body grayish with broad, faint, lighter brownish band Sutures on head top view along back; faint inverted V-shaped pattern on top of each segment when bordered by brown bars viewed from rear without magnification. Head brown with dark markings Head with markings (only markings on top of 1 and some reticulation. Mature length 1 /4 inches. other than those head); body pale or bordering sutures; cream colored. European corn borer—Body cream to pale gray, sometimes with pinkish body with at least Pale Western Cutworm tints and faint stripes. Head dark brown. Mature length 1 inch. some markings. (Photo 9) Fall armyworm—Body colors usually shades of brown, but variations occur ranging from greens to nearly black; body with 4 distinct spots on top of the 8th top view abdominal segment. Head with distinct reticulation. Mature length 1 1/2 inches. Lesser cornstalk borer—Body slender, greenish to bluish-green, with brownish markings on top of prothorax. Head brown. Mature length 3 /4 inch. Four spots equal in size Front pair of spots half the on back of each diameter of back pair on Pale western cutworm—Body cream to grayish-cream with abdominal segment; each abdominal segment; semitransparent skin. Head light brown with sutures bordered by brown breathing pore on prothorax breathing pore on 1 bars. Mature length 1 /4 inches. oval, about 1 1/2 times as prothorax elongate, about long as wide. twice as long as wide. Sorghum webworm—Body with yellowish to reddish-brown stripes and Dingy Cutworm (Photo 5) Black Cutworm (Photo 2) covered with fuzzy hair. Head brown. Mature length 3/4 inch. Southwestern corn borer—Body white with a group of 8 rounded spots Top of head with top view on larger forward part of each segment and 2 spots on smaller rearward distinct reticulation part of each segment; late-season or overwintering larvae are without spots.