2013 Annual Report
1a.Objectives (from AD-416):
1. To discover and evaluate new biopesticides against sweetpotato insects.
2. To develop relationship between sweetpotato root damage and insect population density.
3. To determine correlation between wireworm larval population and adult trap catch.
4. To detect sweetpotato weevil (Cylas formicarius) populations in quarantined counties of southern Mississippi by using pheromone traps.
5. To promote sweetpotato production practices through outreach activities (field days, growers’ meetings and field demonstration plots).
1b.Approach (from AD-416):
New botanical and other biological compounds will be extracted and evaluated against major sweetpotato insect pests. New and conventional sweetpotato varieties will be evaluated for root damage by insects. Root damage will be correlated with insect pest numbers collected by using different sampling methods. Seeds of corn, wheat and crimple oats will be used in bait treatments to collect wireworm larvae in sweetpotato fields. Relationship of adult beetles will be established with wireworm larvae captured in bait traps. Pheromone traps will be used to detect adult Cylas (C.) formicarius population in southern Mississippi. The knowledge gained through research will be dissipated through seminars, research publications, internet, presentations in professional meetings, on-farm demonstrations and workshops.
In 2012 a study on the effect of Prohexadion-Ca on yield and insect damage to sweetpotatoes was conducted. Four sweetpotato varieties, Beauregard, Covington, O’Henry, and Puerto Rican were planted in split plot, randomized complete block design with 4 replications in Alcorn State University (ASU) Extension/Research Demonstration Farm and Technology Transfer Center, Mound Bayou, MS. Prohexadione-Ca treatments (0 and 810 mg L-1 a.i.) were the main plots and cultivars were the subplots. Each plot consisted of 2 rows. Sweetpotato was transplanted to conventionally prepared raised beds at a rate of 10 plants per row, with 1.5 ft between plants within the row and 3.5 ft between rows. The control and treated plots were separated by 10 ft buffer. The experiment consisted of two regimens, irrigated and non-irrigated with 32 plots in each regimen. Drip irrigation was used in both fields as needed until the plants were established and then biweekly to irrigated field only. Pre-plant application of glyphosate (24 oz/acre) was made to burn down all weeds. Post-transplant weed control was accomplished by hoeing and gas powered push tiller. Prohexadione-Ca treatments were applied with a 5 gal backpack sprayer at 810 mg L-1 (140 g a.i. ha-1) mixed with 1 mL L-1 of crop oil concentrate and 1mL L-1 urea ammonium nitrate. Plants were sprayed until run off. Control plots were sprayed with water mixed with 1 mL L-1 of crop oil concentrate and 1mL L-1 urea ammonium nitrate. Treatments were applied twice during the season, 2 weeks and 6 weeks after transplanting.
Effect on plant parasitic nematodes: Soil samples were taken from 4 random places in each plot to detect any difference in relative abundance of plant parasitic nematodes among treatments.
Data Collection: Vine length of sweetpotato plants were measured after 90 days of transplanting by randomly selecting 4 plants in each plot. Sweetpotato roots were harvested, washed and graded into jumbo, US#1 and US#2. All roots were weighed and examined for any insect damage by counting the feeding scars on each root. Insect damaged roots were weighed for comparison.
Samples of sweetpotato weevil were collected from pheromone traps in the southern Mississippi region. Sweetpotato weevil pheromone traps were placed in Copiah County (Crystal Spring area) near ornamental sweetpotato research plots.Traps were also placed around sweetpotato research field in Claiborne County. Eight traps were installed at each location. A trap was fitted on a 4-ft cane just above the plant canopy and loaded with 120 micro gram of sweetpotato weevil lure. The pheromone was replaced every 4 weeks. Traps were checked every 2 weeks.
In our previous study wireworm adults especially Conoderus (C.) vespertinus have been significantly attracted to purple sticky traps. A new trap was designed with 4-wing purple sheets to collect live adult beetles through a funnel into the collection arena. Eight traps were installed around a sweetpotato research field in ASU Ext/Res Demo Farm and Tech Transfer Center, Mound Bayou, MS. Traps were checked twice a week for live C. vespertinus adults.
2013 was a continuation of the evaluation of Prohexadione-Ca on sweetpotato yield and insect damage. No sweetpotato weevil was detected in pheromone traps during 2012. In 2013 trapping continue in sweetpotatoes in Claiborne County, Mississippi with same lure concentration. We were unable to establish a laboratory colony of C. vespertinus due to low catch of adult beetles in 4-wing bucket traps. The 4-wing traps were reinstalled during 2013. Soil bait traps were installed to collect wireworm larvae. Toxicity bioassays will be conducted against collected wireworms with biological extracted compounds.