REVIEW OF SUNFLOWER INSECT PEST PROBLEMS IN NORTH DAKOTA IN 2008 JANET J. KNODEL1, LAURENCE D. CHARLET2, PATRICK B. BEAUZAY1, AND THERESA GROSS2 1 Department of Entomology, Hultz Hall, North Dakota State University, Fargo, ND 58108 2USDA, ARS, Northern Crop Science Laboratory, 1307 18th St. N, Fargo, ND 58105 Introduction The major insect pest species that cause economic losses to sunflower producers in North Dakota are red sunflower seed weevil, Smicronyx fulvus Le Conte (Coleoptera: Curculionidae), banded sunflower moth, Cochylis hospes Walsingham (Lepidoptera: Tortricidae), and sunflower midge, Contarinia schulzi Gagné (Diptera: Cecidomyiidae) (Knodel et al. 2007). New emerging insect pests include the longhorned beetle, Dectes texanus Le Conte (Coleoptera: Cerambycidae), sunflower seed maggot, Neotephritis finalis (Loew) (Diptera: Tephritidae), sunflower bud moth, Suleima helianthana (Riley) (Lepidoptera: Tortricidae), and lygus bug, Lygus species (Hemiptera: Miridae). Sunflower moth, Homoeosoma electellum (Hulst) (Lepidoptera: Pyralidae) migrates occasionally into the northern Great Plains production region and can cause severe yield losses. Results of the 2008 sunflower survey are reported for insect pests in North Dakota. Insecticide efficacy studies are summarized. Materials and Methods 2008 Sunflower Survey in North Dakota. The National Sunflower Association organizes an annual sunflower field survey. In September and October 2008, sunflower fields were surveyed in six states (North Dakota, South Dakota, Minnesota, Kansas, Colorado and Oklahoma) and one Canadian province (Manitoba). The purpose of the survey is to assess yield, plant population, sunflower class (oil or confection), cultural practices, weed species and intensity, insect damage, bird damage, stalk lodging, and diseases. Approximately one field was surveyed for every 10,000 acres in each state and county based on 2008 sunflower acreage as determined by the Farm Service Agency USDA and other state estimates. A total of 77 fields was surveyed in North Dakota in 2008. Insect sampling was conducted by sampling the interior of each field at a distance of 50 feet from the field margin. For longhorned beetle, five stalks were split and examined near the stalk base for larval presence. Larvae are cannibalistic and there is typically only one larva per stalk. Data were recorded as percent of infested stalks. For sunflower midge, five sunflower heads were rated for damage using the Bracken Scale (Bracken 1991), and the average rating was recorded. For sunflower seed maggot and sunflower bud moth, ten consecutive heads were examined and percent head damage was recorded. Photographs of typical injury symptoms associated with these insects were supplied for the surveyors. For red sunflower seed weevil, banded sunflower moth, and lygus bug, five heads were sampled using the following procedure: 1. Using a utility knife, a 1/8 pie-shaped wedge was cut from each head. 2. Seeds were manually rubbed from each wedge into a plastic bucket. 3. Steps 1 and 2 were repeated until a minimum of 100 seeds from 5 heads were collected. 4. Seed from all five heads were placed in a small paper bag. 5. Bags were labeled (county, date, sample #) and sealed. 6. Bags were mailed to the USDA-ARS Sunflower Insect Laboratory in Fargo, ND to determine percent seed damaged by each insect. Insecticide efficacy trial for seed-feeding insect pests of sunflower. The efficacy of insecticides and insecticide + adjuvant combinations were evaluated for control of banded sunflower moth and red sunflower seed weevil in sunflower research plots at the North Dakota State University Prosper Research Site near Amenia, North Dakota. Sunflower was planted on 15 May. Plots were 4 rows wide by 30 ft long and buffered by 10 ft between plots. Row spacing was 30 inches. Plant population was 18,000 plants/acre. The experiment evaluated the efficacy of 14 different insecticide and insecticide + adjuvant treatments, plus one untreated check in a RCB design with four replications. All treatment applications were applied at plant growth stage R4-R5.6 (average R5.3) on 1 Aug using a tractor mounted CO2 boom sprayer at 40 psi, 10 gpa, 30 inch nozzle spacing, Tee-Jet 8002 nozzles, and 18 inches above the canopy. Plots were sprayed between 8:00 a.m. and 10:30 a.m. CDT with an average wind speed of 2.0 mph. Temperature was 77 F and relative humidity was 47%. Plots were harvested on 26 Sep by removing at random a total of ten heads from the center two rows of each plot. Heads were dried, head diameters measured, heads threshed individually, and seed weight per head was determined. A subsample of 200 seeds per head was removed and the number of seeds damaged by banded sunflower moth and red sunflower seed weevil was counted. All data were subjected to ANOVA and means were compared using Fisher’s Protected LSD at the 5% significance level. To satisfy the assumption of homogeneity of variance, banded sunflower moth and red sunflower seed weevil damage count data were transformed prior to analysis using log (X+1). Insecticide efficacy trial for longhorned beetle Dectes texanus. Efficacy of insecticides was evaluated for control of Dectes texanus in sunflower research plots at a cooperator site near Linton, North Dakota. Sunflower was planted on 18 June. Plots were 5 rows wide by 25 ft long and buffered by 10 ft between plots. Row spacing was 30 inches. The experiment evaluated the efficacy of four different insecticide treatments, plus one untreated check in a RCB design with four replications. All treatment applications were applied at the 10- 12 leaf stage on 23 Jul using a CO2 backpack sprayer with 10 ft handheld boom at 40 psi, 20 gpa, 30 inch nozzle spacing, Tee-Jet80015 nozzles, and applied 18 inches above the canopy. Plots were sprayed from 6:30 p.m. to 7:30 p.m. CDT with an average wind speed of 3 mph. Temperature was 84.6 F and relative humidity was 37%. Treatments were evaluated on 17 Sep by randomly sampling a total of 10 stalks from the center three rows of each plot and recording the number of infested stalks. Data were subjected to ANOVA and treatment means were compared using Fisher’s Protected LSD at the 5% significance level. 2 Results and Discussion 2008 Sunflower Survey in North Dakota. In North Dakota, the percent infested stalks by Dectes texanus averaged over 5%. North Dakota’s population of Dectes texanus has more than doubled since the 2003 survey. The area with the highest percent of infested stalks was located in the south central part of North Dakota. The highest number of Dectes texanus in the entire survey area was reported in Kansas with over 50% of the plants infested. Bracken ratings for sunflower midge damage have been low from 2003 through 2008 with an average rating of <1 (light bract damage) in North Dakota (Fig. 2). Sunflower midge damage ratings were also low in all states surveyed in 2008. The sunflower seed maggot and sunflower bud moth are two new insects that were added to the sunflower survey in 2007 and 2008, respectively. For sunflower seed maggot, percent heads damaged decreased from 6% in 2007 to 2% in 2008 (Fig. 3). Damage to heads from sunflower bud moth was low (average of 3.9% heads damaged) in North Dakota (Fig. 4). However, field reports indicated that sunflower bud moth damage was high in the northern Red River Valley and damage by sunflower bud moth was severe in Manitoba, over 20% heads with damaged, in 2008. Seed damage from red sunflower seed weevil (Fig. 5) and banded sunflower moth (Fig. 6) was low (<2%) in North Dakota in 2008. Seed damage caused by sunflower moth was also very low (<0.5%) as this moth did not migrate in high densities into North Dakota during 2008 (Fig. 7). It is important to understand that seed damage does not directly correlate to adult population densities in the field. For example, adult banded sunflower moths were economically important in 2008 in the northern tier of North Dakota, and the majority of sunflower fields required a well- timed insecticide spray to reduce seed damage. Likewise, red sunflower seed weevil was present at economic population levels in the southern tier of North Dakota, and many of the sunflower fields were treated with an insecticide. Brown spot caused by lygus bug is only a problem on confection sunflowers and seed damage was very low (<0.3%) in North Dakota in 2008 (Fig. 8). In 2007, seed damaged by lygus bug in North Dakota had a higher value with an average rating of 3.2%. 3 Figure 1. Longhorned beetle map 2008. Figure 2. Sunflower midge map 2008. 4 Figure 3. Sunflower seed maggot map 2008. Figure 4. Sunflower bud moth map 2008. 5 Figure 5. Red sunflower seed weevil map 2008. Figure 6. Banded sunflower moth map 2008. 6 Figure 7. Sunflower moth map 2008. Figure 8. Lygus bug (brown spot) map 2008. 7 Insecticide efficacy trial for seed-feeding insect pests of sunflower (Table 1). AGI 06020 had the largest head diameter compared to all other treatments and was the only treatment with head diameter significantly larger than the untreated check. The low rate of HGW86 had the smallest head diameter and was the only treatment with head diameter significantly smaller than the untreated check. For banded sunflower moth damage, all insecticide treatments had significantly less damage than the untreated check. AGI 06020 had significantly less banded sunflower moth damage than any other treatment. Steward EC and both rates of HGW86 had significantly more banded sunflower moth damage than most of the other insecticide treatments (pyrethroids). Steward EC and HGW86 have different modes of action than pyrethroids, and may not be as effective in controlling banded sunflower moth.