Commercial Corn Fields Research Articles

Damage Potential of Adult and Larval Southern Corn Billbugs (Coleoptera: Curculionidae) on Field Corn in Eastern North Carolina1

Adult and larval damage potential of the southern corn billbug (SCB), Sphenophorus callosus (Olivier), was studied in small-plot enclosures and in commercial cornfields in eastern North Carolina from 1978 to 1980. In small-plot studies, corn at the two- and four-leaf stages showed damage by adult SCB at several insect densities, but more mature corn was not visibly damaged. Female SCB caused more damage than male SCB on three- to four-leaf stage corn. Damage by females tended to result in dead terminals, whereas feeding by males more often resulted in holes in the leaves. In small-plot studies, average plant height per plot was negatively correlated with average damage ratings per plot on three dates in 1980 on whorl stage corn. However, grain yield per plot at harvest was positively correlated with average damage ratings per plot on 9- to 10-leafstage corn. In commercial cornfields, larval SCB infestations were often associated with early death in corn plants. Of a total of 506 plants sampled at two sites in late July and early August 1980, 85.2% of plants dying early were infested with larval SCB, whereas nondrying plants had 10.0%SeB infestations. This early death was associated with a 42.4% yield decrease in paired comparisons of adjacent dying and nondying plants. The southern cornstalk borer, Diatraea crambidoides (Grote), was the only other insect found in large numbers in the lower cornstalk region. However, its presence was not well related to the incidence of early death.

Host Range of Southern Corn Billbug 1 (Coleoptera: Curculionidae) Adults and Larvae 2

ABSTRACTEnviron. Entomol. II: 954-957(1982) Host range of the southern corn billbug, (SCB), Sphenophorus callosus (Olivier) (Coleoptera: Cur­culionidae), was tested with 14 crop and weed species by artificially infesting plants with SCB adultsand eggs; field observations were also made. Of 14 species tested, only corn, Zea mays L., and yellownutsedge, Cyperus esculentus L., allowed completion of larval development, although adults fed on awider variety ofplants. Scirpus cyperinus (L.) Kunth (Cyperaceae) was found to be a new SCB larvalhost from field observations. Overwintered SCB adults were fed sections of greenhouse-grown cornand four weed species in the laboratory. Survival was highest on corn and yellow nutsedge and loweston common larnbsquarters, Chenopodium album L. SCB were able to produce mature eggs only iffedeither corn or yellow nutsedge. Many Sphenophorus spp. weevils are economic pestsofgrass crops (Satterthwait 1932). One species, S. cal­losus (Olivier), the southern corn billbug (SCB), is animportant pest ofcorn in eastern North Carolina. Webs­ter (1912), Metcalf(1917) and Satterthwait (1931) listednine genera (24 species) ofGraminae, Cyperaceae, andJuncaceae as hosts of SCB.Because of the restricted host range of SCB and itssedentary habits, early workers (Webster 1912, Metcalf1917) suggested crop rotation as a control measure.However, since that time, the eastern North Carolinaagroecosystem has changed greatly with respect tocropand weed species. This study was conducted to providemore information on the host range ofadult and larvalSCB in the current corn-soybeanagroecosystem ofeast­ern North Carolina so that the basis for continued useofcrop rotation as a management tactic could be eval­uated.Materials and MethodsAdult and Larval Host RangeDuring field studies of SCBbiology from 1978 to1980, observations were made on SCB adult feedinghabits in over 15 commercial corn fields (principally inWashington, Tyrrell and Hyde Counties, N.C.). Plantspecies on which adults were seen feeding were in­spected later for SCB eggs and larvae.Various grasses, sedges, rushes and related plantsgrowing in drainage canals and uncultivated areas nearthe above infestations ofSCB were sampled in late Julyto August; the period of greatest abundance of SCBpupae and teneral adults (Wright 1981). Specimens col­lected were preserved in alcohol orreared to adult emer­gence. Samples ofweevil-infestedplants were identified.Studies were conducted at the Tidewater ResearchStation (TRS), Plymouth, N.C., in 1978 to 1980 to de­termine the acceptability ofvarious plants for SCB adult

Flea Beetle Control in Sweet Corn, 1980

Abstract This trial was conducted in a commercial sweet corn field planted on May 5. Two row by 50 ft plots were replicated 5 times. All treatments were applied on May 9 as a 7 inch band over the row using a one row Gandy applicator and incorporated using a hand rake. Twenty plants per plot (10 plants per row) were evaluated for flea beetle damage on Jun 2.

Minimum Number of Insecticide Applications for the Control of the European Corn Borer on Sweet Corn in Quebec1

Field experiments were conducted at St. Luc, Quebec, from 1963 to 1965, to determine the relative effectiveness of 1, 2, 3, or 4 applications of DDT or carbaryl (Sevin®) in 2 commercial sweet corn fields. In all cases, the 1st application was made 5 days after the beginning of egg laying period and the others at weekly intervals, except for the single application of DDT or carbaryl, which was made 15 days after the 1st eggs were observed. In general, results were similar for the 3 years: the early variety was more infested than the late variety, DDT was slightly superior to carbaryl, the peak of egg laying always occurred between the 2nd and 3rd insecticide applications, and the date on which the single application was made varied each year from only 2 to 4 days from the date of maximum oviposition. The results of this 3-year study indicate that under the conditions of heavy infestations of the European corn borer, Ostrinia nubilalis (Hubner), in southwestern Quebec, 3 applications of either DDT or carbaryl would be recommendable for an early variety of sweet corn and 1 application for a late variety to obtain economical commercial control.