Peach Twig Borer Control in Peach with Success – 2001

Diane G. Alston and Carin A. Miller

Department of Biology, Utah State University

Objective: To evaluate and demonstrate the efficacy of Success (spinosad; Dow AgroSciences) for control of peach twig borer (Anarsia lineatella) in peach.

Brief Background on Success: Success is a mixture of two spinosyn factors that are produced by an actinomycete bacterium, Saccharopolyspora spinosad, under aerobic fermentation conditions. It has a novel mode of action that causes rapid excitation of the insect nervous system. It targets chewing insects and is registered on more than 16 crops. It is considered a "soft" insecticide with good environmental safety, low toxicity to non-target and beneficial arthropods, and can be a nice fit for an integrated pest management (IPM) or resistance management program.

Methods: The trial was conducted in a 1 acre, 11-yr-old ‘Suncrest’ peach orchard at the Utah State University research farm in Kaysville, UT. A delayed-dormant (calyx-green to first pink) treatment of Superior oil + Thiodan 3EC at 0.67 qt/acre was applied to the entire orchard on 5 April 2001 for control of early-season peach twig borer larvae.

Adult peach twig borer was monitored with one pheromone-baited trap to determine biofix (first consistent moth catch) and to follow seasonal flight patterns. Timing of treatments was based on biofix and a degree-day (DD) model. The first cover spray timed for 28% egg hatch of the first summer generation was applied at 400 DD after biofix. The second cover spray timed for 51% egg hatch of the second summer generation was applied at 1460 DD after the first generation biofix. Treatments were applied with an air blast sprayer at a rate of 70-80 gal of dilute spray per acre.

Success was applied to the entire orchard at a rate of 6 oz per acre on 15 June (400 degree-days after biofix) and 31 July (1460 degree-days after biofix). No other insecticides were applied to the orchard during the growing season. Mating disruption (Isomate-P Pheromone; Biocontrol Limited) dispensers were applied on 22 June for control of greater peachtree borer (Synanthedon exitiosa).

Three hundred peach fruits were randomly sampled from across the entire orchard to determine peach twig borer injury levels at harvest on 15 August 2001.

Results:

Fruit Injury

No injury from the insect was detected in any fruit in 2001. As a comparison, in this orchard in 2000, 9% of fruit had peach twig borer in plots not treated during the summer with insecticides. No fruit injury was observed from any other arthropod pests.

Peach Twig Borer Pressure

Peach twig borer populations as measured by pheromone trap catch (Fig. 1) were similar in the study orchard (labeled as Success Trial) to populations in representative grower orchards in Utah County (labeled as Payson, Genola, Santaquin, and West Mountain) early in the season, with a flight peak in early June. However, later in the season, three Utah County sites (Santaquin, West Mountain and Genola) had a second flight peak in early August, and the Payson orchard had a flight peak in mid August. In comparison, both the Success trial and a second Kaysville Success-treated orchard (labeled as Kaysville Success) had very little flight activity starting in the middle of July and continuing through the rest of the season.

Conclusions:

Success is an excellent alternative to a standard summer insecticide program, such as Thiodan (endosulfan) or Guthion (azinphosmethyl), for control of peach twig borer in peach fruit. It is critical to control early-season peach twig borer larvae that tunnel in peach shoots with a delayed dormant or other insecticide program (e.g., Bt at bloom). It is important to reduce spring peach twig borer densities in order to use only two summer sprays timed with the degree-day model and insect phenology. No secondary pest problems or phytotoxicity from Success have been observed after two years of use in this orchard.

Success is a "soft" insecticide with a nice fit into IPM programs and for use when resistance to other insecticide classes has occurred. Success has low toxicity to non-target arthropods and should not lower the densities of beneficial arthropods in an orchard. It also has low environmental toxicity and reduced concerns for worker safety as compared to standard broad-spectrum insecticides.