Abstract Sweet corn was planted 3 Jul at the O’Neall Memorial Farm, Lafayette, Indiana. Plots consisted of four rows, 30 ft. long, 30 in. apart, and were arranged in a RCB design with four replications. Insecticides were applied via a Hahn HiBoy sprayer and propelled by CO2 using 3 hollow cone nozzle tips per row, one over the top and one directed at each side of the ear zone. Sprays were delivered in 17.5 gal waterlacre at 28 psi. Sprays were applied beginning at row tassel on 20,26, and 30 Aug and 3 Sep. On 11 Sep, 25 ears per plot were harvested and evaluated for damage and the number of caterpillars present was counted. Ears with damage confined to the terminal inch were considered marketable. Ears with no visible insect feeding were rated as clean. Results are presented as percentage of damaged ears based on 100 ears examined ant, counts of caterpillar species per 25 ears.
Field and laboratory experiments were conducted to study the effect of soil applied (Carbofuran) Furadan on watermelon and cantaloupe yields. Yields were significantly (p≤ 0.05) greater when Furadan was used than when it was not. The observed yield increases may have been due to factors other than just the insecticidal properties. Other systemic insecticides demonstrated no similar increase in yield. Yield increases were also evident even when plants were grown in sterile soil. Yield increase was due to a significant increase in the first harvest of watermelon and the first three harvests of cantaloupe. Numbers of fruit and average wt/fruit were increased for watermelon at the first harvest. Midwest growers usually receive the highest price per pound of watermelon at the first harvest. This significant increase in early harvest more than pays for the application of the chemical.
Cornfields in three counties in Iowa were scouted from 1979 through 1982 for four major corn insect pests. Black cutworms caused economic damage in 10 of 151 fields scouted over the four years of the study. Eight of those 10 damaged fields occurred in 1981, a year of severe cutworm outbreak in Iowa. No fields were observed with damaging infestations of wireworms. All fields scouted had some whorl feeding by European corn borers, but only eight of 100 fields scouted surpassed the economic threshold. Corn root worm adults exceeded the economic threshold of 1 beetle per plant in 112 of 118 fields scouted over 3 years, with an overall mean density of 4.2 beetles per plant. Eighty-three percent of those fields with soil insecticide check strips had root ratings exceeding the 2.5 economic threshold in the untreated areas. Corn is the most important crop grown in Iowa, with about 5.5 million ha planted annually. Approximately 40% of this total is corn following corn (Becker and Stockdale, 1980). Corn grown in Iowa is subject to attack by a number of insect pests in various degrees of severity. The more important pests include the northern and western corn rootworms, Diabrotica barberi Smith and Lawrence and D. virgifera virgifera LeConte; the black cutworm, Agrotis ipsilon (Hufnagel); the European corn borer, Ostrinia nubilalis (Hubner); and several genera of wire worms. Black cutworms are a sporadic, but sometimes devastating, pest of corn. The larvae cause damage by severing seedling plants. The amount of damage varies considerably from year to year. In 1979, about 92,000 ha were treated to control black cutworms in Iowa. Iowa extension entomologists estimate that approxi mately 400,000 ha in Iowa had economically damaging levels of cutworms in 1981, a cutworm outbreak year throughout much of the state (D. E. Foster, pers. comm.). Iowa extension recommendations are for treatment when two to three percent of the plants are wilted or cut and small worms are present (Stockdale et al., 1982). Wireworms have been an important pest of corn in the past, infesting as many as 53% of fields (Bigger and Decker, 1966). Wireworms have dramatically declined in importance because of changing rotation practices by farmers (Turpin and Thieme, 1978). Wireworms cause damage to corn by tunneling into seeds or the base of seedling plants, resulting in death or injury to the plant. European corn borers infrequently reach sufficient densities to cause economic damage, which for the first generation is estimated to be 35% of the plants showing leaf feeding with larvae present (Stockdale et al., 1982). More than 72,000 ha 1 Journal Paper No. J-10939 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Projects No. 2250 and 2559. 2 Department of Entomology and Nematology, University of Florida, Everglades Research and Education Center, Belle Glade, Florida 33430. 3 Department of Entomology, Iowa State University, Ames, Iowa 50011. Accepted for publication 23 July 1985. This content downloaded from 40.77.167.6 on Thu, 22 Sep 2016 07:34:19 UTC All use subject to http://about.jstor.org/terms 270 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Table 1. Number of cornfields in scouting program with economic damage by black cutworms (>3% plants cut) and first-generation European corn borer (>35% whorl feeding). Number of fields scouted in parentheses.
Studies were conducted in commercial sweet corn fields in upstate New York to collect information for developing a sampling protocol for egg masses and larvae of European corn borer (ECB), Ostrinia nubilalis (Hübner). Information was collected on 1) aggregation of populations in portions of the field (e.g., aggregation along borders), 2) distribution of sample observations for a whole-plant sample unit, and 3) distribution of insects within the sample unit (i.e., the within-plant distribution of eggs and larvae). Analyses of data indicated that distribution of egg masses and larvae throughout a field was essentially random with no evidence to support the hypothesis that eggs were preferentially laid near field borders where mating and resting of female adults occurred. From data on dispersion of ECB on individual plants, a Poisson series is a reasonable model for characterizing distribution of ECB egg masses. Parameters of a variance-mean model for the small larvae indicate that these larvae are highly aggregated but that aggregation becomes less pronounced as larvae mature. Since control measures are most effective against egg masses and small larvae, a sampling protocol that utilizes characteristics of both stages should be employed. An index of ovipositional activity measured via incidence of egg masses on plants can be determined by inspecting plants for presence of either egg masses or small larvae. This can be accomplished by using a binomial-based sequential sampling plan.
Results are presented of experiments conducted during 1997, 1998, 1999 and 2000 in Indiana, USA, to develop a sampling programme for adult Western corn rootworm (WCR) in the maize/soyabean rotational system and to establish an economic injury level and an economic threshold based on WCR adult density estimates in soyabean for the potential damage created by WCR larvae in subsequent maize fields.
Corn root worm adult densities were monitored in 31, 43, and 44 Iowa cornfields in 1979, 1980, and 1981, respectively. The season after monitoring, plots with no soil insecticide were left in most fields. Root worm larval damage was measured in untreated areas, and yield was estimated in both treated and untreated areas of each field. Linear regressions indicated significant relationships between adult densities and larval damage and yield loss, but much of the variation in damage or yield loss was not explained by the model. Current economic thresholds did not accurately predict economic damage or appreciable yield loss >50% of the time. Addition of edaphic and agronomic variables improved the models, but 60% of the variation in yield loss was still unexplained. Value of adult sample information was determined by Bayesian analysis to be zero. A 6-fold increase in ability to predict when economic loss would not occur would be necessary for sampling to be worthwhile. The optimal strategy for managing corn root worms in Iowa in our study was not to sample for adults and always to treat corn following corn with a soil insecticide at planting time.
Abstract Cantaloupe, variety ‘Superstar’, was transplanted at the 3 leaf stage on 28 Apr. Experimental units (plots) consisted of one row 60 ft long, 15 plants per row. Rows were 6 ft apart, lined with black plastic mulch and trickle irrigated. Treatments were arranged in a RCB design, replicated 4 times. Soil insecticides were applied on the day the plastic was laid, 5 days before transplants were set. Foliar sprays were applied on a weekly basis starting 5 May, except for Admire 2F, which was applied on a 2 wk schedule. A total of 8 weekly applications was made. All liquid soil insecticides were applied with a R&D CO2 backpack sprayer, operating at 40 psi and delivering 30 gal/acre. Granular soil insecticides were applied via a Gandy box attached to the mulch laying machine. Foliar sprays were applied at 20 gal/acre at a pressure of 30 psi. Plots treated with Furadan 4F at a rate of 1 qt form./acre at planting, followed by alternating weekly sprays of Sevin 80S (1.25 lb/acre) and Thiodan 3EC (1 qt/acre) are designated in the treatment column as Furadan/Sevin/Thiodan. Beetle counts were taken on a per plant basis. Percentage of plants with bacterial wilt was recorded, 25 Jul, by checking for the presence of bacterial ooze. Yields (weight of melons) were taken over a 4 week period starting on 2 Jul through 2 Aug. For presentation purposes, this has been condensed into: early yield (2 Jul-14 Jul), secondary yield (16 Jul-2 Aug) and total yield (sum of early and secondary yields).
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