Effectiveness of In-Furrow Insecticides for Thrips Control in Peanuts, 2017

The objective of this study was to evaluate the effectiveness of in-furrow insecticides for managing tobacco thrips, the dominant early season pest of peanuts in Alabama. This study was conducted at the Wiregrass Research and Extension Center, Clanton, AL. Peanut, GA O6-G, was planted on 9 May in single and twin rows (two rows with 9 inch between an overall 36 inch spacing). Eleven treatments, including the untreated check, were arranged in an RCB design with four replications. Peanut plots were 40 ft long with four treated rows per plot and 25 ft alleys. At-plant in-furrow liquid insecticides were applied on 9 May using a CO₂ powered backpack sprayer with nozzles mounted to spray in-furrow at 3 mph 15 psi at 10 gpa using size 35 orifices for twin rows and size 52 orifices for the single rows. Ground-driven applicator boxes were used for applying granular insecticides. Thrips damage ratings were determined on 18 Jun by examining 10 random peanut terminal leaves using a 10-point damage rating (DR) system: 1 = no damage; 2 = 10% of emerging leaves infested or damaged; 3 = 20% of emerging leaves infested or damaged; 4 = 30% of emerging leaves infested or damaged; 5 = 40% of emerging leaves infested or damaged; 6 = 50% of emerging leaves infested or damaged; 7 = 60% of emerging leaves infested or damaged; 8 = 75% of emerging leaves infested or damaged; 9 = 90% of emerging leaves infested or damaged; 10 = 100% of emerging leaves infested or damaged + dead plants. Peanut plots were inverted on 24 Oct and picked on 28 Oct using a two-row peanut combine that weighed pod yield for each plot. The average DR and yield are reported in Table 1. Data were analyzed using ANOVA and means were separated using Fisher’s protected least significant difference (LSD, P < 0.05).

Year 2017 was marked by extremely wet weather. There were statistically significant differences between treatments for thrips DR (Table 1). The untreated peanut plots had the highest damage rating. Reduced rates of in-furrow insecticides in twin rows resulted in high thrips foliar damage rating. There was no effect of insecticide treatment on peanut yields in this test. This was possibly due to excessive rainfall and compensatory plant growth. No phytotoxicity was observed from any of the insecticide treatments.¹

Footnotes