Corn Borer Egg Masses Research Articles

Trichogramma parasitoids for control of Lepidopteran borers in Taiwan: species, life‐history traits and Wolbachia infections

AbstractTrichogramma, polyphagous endoparasitoids of lepidopteran eggs, are used against a variety of crop pests throughout the world including those of sugar cane and corn in south‐eastern Asia. Their ability to be easily and economically reared on factitious hosts and their wide host range have contributed to their widespread use in pest control. The overall aim of this study was to select strains for eventual release in crop areas for control of lepidopteran borer pests of sugar cane and corn. To this end, we identified common Trichogramma species emerging from corn borer egg masses throughout south‐western Taiwan, compared their life‐history characteristics, assessed their thermal limits and identified the Wolbachia infection status of collected Trichogramma parasitoids. Trichogramma ostriniae was the most commonly collected species on corn, with occasional detection of T. chilonis and an unidentified species designated as T. sp. y. Although the sex ratio varied widely between sites, Wolbachia infection was detected only at a single site in one species (T. ostriniae). Wolbachia‐infected T. ostriniae were tolerant to high temperature stress. Trichogramma chilonis had lowest fecundity of the three species tested, and a Wolbachia‐infected T. ostriniae strain had lower fecundity than an uninfected strain. Given the limited availability of distribution and historical data for Trichogramma species in Taiwan, the current study provides a baseline for future work and also highlights the importance of accurately identifying species when establishing colonies of natural enemies for biocontrol.

Efficacy of inoculative releases of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) against European corn borer Ostrinia nubilalis (Lepidoptera: Crambidae) in field corn

We evaluated the egg parasitoid Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) to control European corn borer [Lepidoptera: Crambidae: Ostrinia nubilalis (Hubner)] in Weld corn in 2001 and 2002. Inoculative releases of 75,000 T. ostriniae/ha occurred in New York and Virginia in 5–10 cornWelds per state when corn was at mid-whorl. Incidence of egg mass parasitism, number of stalk tunnels, incidence of ear damage, and whole-plant yield were evaluated. Parasitism of European corn borer egg masses ranged from 0 to 75% in release plots and was greater in release plots than in control plots. Individual comparisons between paired release and control plots showed no reductions in either stalk or ear damage. However, when data were combined across both years and Welds, stalk and ear damage were signiWcantly reduced in New York. In Virginia, no signiWcant diVerences were detected using data obtained from one year. There were no diVerences in yield between release and control plots. Low densities of European corn borer, drought conditions in 1 year, and a larger plant canopy in Weld corn are possible reasons why T. ostriniae releases provided less control than has been observed in previous trials in sweet corn. Additional research focused on improved timing and frequency and number of releases is warranted.

Oviposition Behavior ofOstrinia nubilalis(Lepidoptera: Crambidae) in Response to Potential Intra- and Interspecific Interactions

Abstract Oviposition behavior is an important mechanism for establishing spatial distribution and mitigating potential interactions among community members. We studied the oviposition behavior of the European corn borer, Ostrinia nubilalis Hubner, in the presence of conspecific larvae, the aphid Rhopalosiphum maidis (Fitch), and corn pollen to determine whether these potential interacting factors affect the distribution of European corn borer egg masses laid on sweet corn in field cages. We found that ovipositing females in the field differentiate between adjacent corn plants in response to conspecific larvae. We also found that European corn borers laid significantly fewer egg masses on plants with large aphid colonies compared with adjacent plants with few aphids. Furthermore, fewer egg masses were laid on the top one third of the plant where the aphid colonies were located. We also tested for a fitness advantage of European corn borer’s oviposition behavior in response to aphids and found that neonate ...

Inheritance of an oviposition behavior by an egg parasitoid.

A quantitative genetic study revealed genetic and environmental sources of variance in percentage parasitism of European corn borer egg masses and secondary sex ratios by Trichogramma nubilale. Full and half-sib groups of T. nubilale were obtained from a nested mating design, which permitted the partitioning of the variance of T. nubilale parasitism of European corn borer egg masses into additive genetic variance, maternal/dominant variance and environmental variance. A mother-daughter regression of the percentage of an egg mass parasitized allowed a determination of the direction of a potential response to selection in the event of maternal effects. No or very little additive genetic effects were associated with the percentage of eggs within a mass parasitized and secondary sex ratios, but a significant amount of the variance for both traits had a maternal and/or dominant genetic source. The relationship between mothers and daughters in egg mass parasitism was positive, and 55.4% of the progeny of a given mother had behaviors that resemble their mother. Most of the variance had an environmental and/or unknown genetic source implying potentially high phenotypic plasticity associated with all these traits. The presence of maternal effects and phenotypic plasticity could have multiple and complex effects on progeny characters and potential responses to selection.

Functional Responses of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) to Ostrinia nubilalis (Lepidoptera: Pyralidae) Under Laboratory and Field Conditions

Laboratory tests and field experiments were conducted to determine the functional response of Trichogramma ostriniae Pang & Chen to its host, eggs of the European corn borer, Ostrinia nubilalis (Hubner), under different conditions. Individual female wasps were offered different densities of host eggs for 16 h at 17, 20, and 27°C. Field experiments were carried out in a sweet corn field that was divided into 6 plots of equal size (120 m2). Sentinel European corn borer egg masses were exposed to wasps for 3 d, from day 0 to 3 and day 4 to 7 after releasing wasps. Both the laboratory study and field experiments indicated that egg parasitism was positively correlated with egg density. However, this relationship differed significantly for the 3 temperatures in the laboratory study and varied considerably for the different days of exposures (days 0–3 versus days 4–7) and for different replicates (time of the year). The Gompertz equation and a modified disc equation were fitted to the laboratory data categorized based on temperatures. The results showed that female T. ostriniae might exhibit the type II or type III functional response depending on temperature. The field data suggested a type II functional response when data were pooled for all replicates.

Statistical study of Trichogramma brassicae efficiency in relation with characteristics of the European corn borer egg masses

AbstractThe efficiency of Trichogramma brassicae inundative releases in biological control of the European corn borer Ostrinia nubilalis was analyzed in seven plots of 504 plants, each situated in a corn field naturally infested by the European corn borer. Different strategies of Trichogramma releases were defined on the seven plots. These inundative releases were concluded to be highly efficient even on plots where there were either no parasitoid release or only one parasitoid release at the beginning of the egg mass laying period.

Control of European Corn Borer on Two Varieties of Peppers, 1992

Abstract Insecticide trials on bell and sweet peppers were conducted at Michigan State University Horticulture Teaching and Research Farm in 1992. Pepper seedlings were obtained from a local grower and transplanted into 6.1 m rows on 6 Jun, with 91.4 cm between row spacing and 35.6 cm between plant spacing. Five treatments were applied to both pepper varieties in a randomized block design with four replications. Treatments were applied to foliage using a hand held CO2 sprayer at 35 psi with a single nozzle at 40 gal/acre. Low corn borer activity led us to artificially infest our plots. European corn borer egg masses were obtained from the Corn Insect Lab at Ankeny, Iowa. Five randomly selected plants per replicate received ECB egg masses. The egg masses were pinned to the underside of the leaf through the mid rib, near a developing fruit. One egg mass per plant was attached 17 Aug and two egg masses per plant were attached 3 Sep. All treatments were applied on 18, 24, and 31 of Aug, and 6 Sep. Orthene 75 SP and MVP were sprayed on alternate weeks, beginning with Orthene 75 SP. Pepper fruits were destructively harvested on 18 Sep. Only peppers from the artificially infested plants were sampled, with no more than five fruit picked per pepper plant. Each fruit was cut open and inspected for ECB larvae. Fisher’s Protected LSD test at β = 0.01 was performed on the percent of pepper fruit contaminated with ECB larvae.

First Generation European Corn Borer Control on Sweet Corn, 1991

Abstract Excellency' sweet corn was planted 23 May. Treatments were arranged in a randomized complete block design and replicated four times. Treatments consisted of 40-ft single row plots with 30-inch row spacing separated by single border rows. Whorls of V6-stage corn were hand-infested with two black head stage European corn borer egg masses on 25 Jun. Whorls were treated 27 Jun. Granular formulations of insecticides were applied in a 14-inch band with a Noble insecticide applicator. Liquid formulations were applied in a 7-inch band with a COa pressurized backpack sprayer fitted with one 8004 Teejet nozzle delivering 32 gal/acre at 30 psi. Ten stalks per plot were dissected 8 Aug from one inch above the soil line to the tassel. Cavities were counted. Tunnels of at least one inch in length were considered one cavity.

Statistical analysis of occupancy rates for overdispersed populations by redistribution procedures: Application to the european corn borer EGG masses distribution

SummaryStandard statistical analyses of distributions of individuals from contingency tables are generally invalid if the individuals are not distributed independently of each other. In this paper, we discuss a method of testing hypotheses about classification category occupancy rates for overdispersed population or for population whose individuals are distributed by groups rather than lonely. These methods are based on population redistribution simulations and provide valid, exact and powerful tests in situations for which classical methods are not appropriate. Illustrations are given from the European Corn Borer eggs data.

Dispersal and Survival of Early Instars of European Corn Borer (Lepidoptera: Pyralidae) in Field Corn

Cohorts of European corn borer, Ostrinia nubilalis (Hubner), from eggs infested on whorl-stage corn ( Zea mays L.), were intensively sampled through fourth instar in 1986 and through fifth instar in 1987. In both years, central plants in plots (4 by 2 m, 55 plants) were infested with European corn borer egg masses to simulate a first-generation infestation. In 1986, one egg mass was placed in each plot, whereas in 1987, plots received one, two, or four egg masses. In both years, >50% of the recovered larvae were on the infested plant. Mean dispersal distance increased linearly with time in both years. However, maximum dispersal distance was independent of time in both years. In 1987, egg mass density had a significant linear effect on maximum dispersal distance but no effect on mean dispersal distance. The radius encompassing 90% of the recovered larvae included the infested plant and two plants on either side within the same row. Mortality occurred mainly within the first 48 h: 75.7% in 1986 and 82.9% in 1987. A logistic regression showed that egg and larval survival were independent of egg mass density. The number of tunnels produced per larva found at 8 d after infestation (considered equivalent to scouting) was 0.592. Knowledge of European corn borer dispersal and survival could be used to improve sampling plans and the calculation of economic thresholds.

Estimation of european corn borer egg masses density by sampling of runs

SummarySpatial distributions of individuals may be considered in two ways: Firstly, individuals are situated on a continuum. Secondly, individuals are situated on discrete units, for example, insect eggs on plants. The aim of this paper is to show that sometimes, in the latter case, sampling methods based on infestation runs can be of interest in estimating population density. Analytical results are obtained under complete spatial randomness hypothesis and alternative hypotheses. Sampling procedures with limited cost are discussed and the European corn borer (ECB) case is mainly considered.

European Corn Borer Control in Sweet Corn, 1982

Abstract Insecticide treatments were applied to sweet corn in Fargo, ND. Each treatment was replicated 3 times in a completely randomized test. Plots consisted of 3 rows of sweet com approximately 27 m long. There were 2 guard rows on the edges of the field. Treatments were applied to the center row in each plot. Ten days prior to insecticide application, 25 plants in the center of each row were marked for treatment and infested with corn borer egg masses (in the black head stage) supplied by the Corn Insects Research Laboratory, Ankeny, Iowa. The treatments were applied in the whorl of the corn plants in late Jul. Analyses are based on data from examination of ears (harvest) and stalks (fall) for borer larvae. Analyses of variance and Duncans Multiple Range Tests were conducted with borer counts from ears, stalks and ears and stalks combined. Data were transformed by .

Fruit Insect Control, 1985

Abstract ‘Large Red Cherry’ peppers were transplanted 7 Jun, near Benson, NC. Single row plots 10 ft long on 60 in centers were arranged in a randomized complete block design replicated 4 times. Applications were made using a C02 pressurized backpack sprayer with a single hollow cone nozzle delivering 54 gal/acre at 60 psi. Fruit was harvested and plants were artificially infested with 2 European corn borer egg masses per plant on 30 Jul. Treatments were applied 2, 9, and 16 Aug. Fruit was harvested and the % of infested fruit recorded on 13 and 22 Aug.

Insect Control in Green Bell Peppers, 1984

Abstract Bell peppers were transplanted on 24 May, in 4-ft rows at the MSU Horticultural Experimental Station in Sodus, MI (Berrien Co.). Plots were arranged in a randomized complete block design with 4 replications (= blocks) per treatment. Each plot was 3 rows wide (12 ft) by 25 ft long. Treatments were applied on 25 Jun; 2, 12, 18, 25 Jul; 1, 8, and 15 Aug with a tractor-mounted boom sprayer at 30 gpa. Efficacy was determined by examining 2 plants from the center row of each plot. Entire plants were examined for corn borer egg masses, 2 leaves per plant were examined for aphids, and 5 mature fruit (mid season) or 10 mature fruit (harvest) from the center of each plot were examined for corn borer damage.

European Corn Borer Control in Sweet Corn, 1983

Abstract Sweet corn was planted at the M.S.U. entomology field research farm on campus on 13 June. Plots were four rows wide by 50 ft long. The treatments were arranged in a randomized complete block design with three replications per treatment. Treatments were applied with a tractor-mounted boom sprayer at 30 gal/acre. The first treatment application coincided with the beginning of tassel formation in the whorl when the plants were about 18 in. tall. (Some plants showed beginning of green silk.) European corn borer egg masses were sampled on 5 plants approximately weekly, and treatments were applied at 4-day to weekly intervals, depending on number of egg masses. Treatment dates were 27 July, 5, 9, 12, 16, and 24 Aug. Damage ratings were taken at harvest on 26 Aug. Twenty ears per plot, from the middle two rows, were inspected for larvae and damage.

Insect Control in Green Bell Peppers, 1983

Abstract Seedling green bell peppers were transplanted in 5-ft rows on 1 June at the M.S.U. Hortic. Exp. St. in Sodus, Mich. (Berrien Co.). Plots were arranged in a randomized complete block design with four replications (= blocks) per treatment. Each plot was three rows wide (15 ft) by 15 ft long. Treatments were applied on 23 June, 7, 14, 21, and 28 July, 2, 11, 18, 25, and 31 Aug., and 13 and 23 Sept., with a tractor-mounted boom sprayer at 30 gal/acre. Efficacy was determined by examining two plants from the center row of each plot. Entire plants were examined for corn borer egg masses, two leaves per plant (mid season) or five per plant (late season) were examined for aphids, and three mature fruit (if present) from the center of each plot were examined for corn borer damage.

Control of First Brood European Corn Borer in Field Corn, 1982

Abstract ‘Funks 4252’ field corn was planted May 28 to 36-in rows at the Rosemount Agricultural Experiment Station, Rosemount, MN. Plots were 50 row-ft, separated by border rows, arranged in a randomized complete block with 3 replications. The center 10 plants in each plot were infested Jul 10 with European corn borer egg masses in the ‘blackhead’ stage of development at the rate of 1 egg mass/plant. Applications of insecticide were made Jul 15. Sprays were applied using a CO2compressed air sprayer delivering 20 gal/acre at 25 psi, directed into the whorl. Granular materials were dispensed as a 7-nn band over the plants. Evaluations of all infested plants were made Aug 4 using a 9 point leaf damage rating scale.

Foraging by a Predaceous Beetle, Coleomegilla maculata (Coleoptera: Coccinellidae), in a Polyculture: Effects of Plant Density and Diversity

Experimental studies in a greenhouse demonstrated that the foraging rate per individual of a predaceous beetle, Coleomegilla maculata , on egg masses of the European corn borer was significantly reduced by increasing density, but not diversity, of the plants on which it foraged. In higher-density plantings, the beetles apparently spent more time foraging on plants that contained no food, indicating a certain degree of randomness in the foraging behavior of the beetle. These data help explain why observed predation rates on European corn borer egg masses were higher in field plantings of com monocultures than the more densely planted corn-bean-squash polycultures. Since polycultures are nearly always more dense than their respective monocultures, intercropping may act to decrease the predation rate and abundance of certain insect predators or parasites.

Control of Insects of Snap Bean, 1981

Abstract ‘Stretch’ snap beans were planted Jun 2 in 36 inch rows at the Rosemount Agric. Exp. Stn., Dakota Co., MN. Plots were 18 row-ft, separated by border rows, arranged in a randomized complete block design with 3 replications. The center 5-ft of each plot was infested Jul 23 with 20 European corn borer egg masses in the “blackhead” stage of development. Insecticide applications were made Jul 24 using a CO2 compressed air sprayer delivering 50 gal/acre at 25 psi. Evaluations of potato leafhopper populations were made Aug 6 by randomly selecting 20 trifoliate leaves in each plot. Evaluations of European corn borer injury were made Aug 24 by examining all plants in the center 8-ft of the plots and recorded larval tunneling.

Aerial Sprays for Control of European Corn Borer in Snap Bean, 1980

Abstract Snap beans were planted Jun 10 at the Rosemount Agricultural Experiment Station, Rosemount, MN. Plots were 48 x 50 ft, arranged randomly in 3 replications along the flight path of the aircraft. Sprays were applied Jul 29 and Aug 5 with a fixed-wing agricultural aircraft delivering 5 gal/acre at 33 psi. Plots were infested with corn borer egg masses in the ‘blackhead’ stage Jul 25 at a rate of 22 egg masses/50 ft row. Evaluation of insecticide efficacy was done by harvesting 50 row-ft from each plot and examining plants for dammage pods and vines.