Resistant Rootstocks as a Sustainable Defense Against Peachtree Borer in Southeastern Peach Orchards

Commodities

Practices

The peachtree borer, Synanthedon exitiosa (Say) (Lepidoptera: Sesiidae), is a serious tree-infesting pest of stone fruit (genus Prunus), particularly in peach orchards where trees of all ages are vulnerable. Larvae feed on the cambium and inner bark of host trees, causing loss of vigor and productivity in older trees and mortality in young trees. Growers have historically relied on managing the peachtree borer with the organophosphate pesticide, chlorpyrifos. However, the EPA continues to challenge the use of chlorpyrifos due to risks to human health, leaving growers with fewer options for management of these pests. Rather than relying on insecticidal treatments, there is potential for resistant rootstocks to mitigate the damage caused by this pest. Preliminary research has shown that peachtree borer females prefer to oviposit on peach rootstocks over similar plum rootstocks, indicating non-preference for plum. In a controlled trial orchard, peachtree borer damage will be monitored in plantings of peach and plum rootstocks at standard and elevated graft heights to evaluate the influence of both rootstock type and 'high-budding' on oviposition preference. Additionally, potted Prunus rootstocks will be evaluated using gas chromatography-mass spectrometry to identify volatile compounds that may serve as attractants to peachtree borer females for oviposition and to identify properties that vary among Prunus rootstock cultivars. Identifying chemical cues and verifying resistance in the field will provide the basis for a long-term, sustainable management strategy for peachtree borer. Exploiting these natural resistance traits in rootstocks will broadly reduce the reliance on chemical insecticides in peach orchards.

1. Determine whether plum rootstocks and elevated grafting heights (i.e., 'high-budding') reduce peachtree borer infestation compared to peach rootstocks and standard grafting practices.
2. Compare volatile organic compound profiles emitted by Prunus rootstock cultivars to identify compounds known to elicit ovipositional responses in peachtree borer females and to characterize differences in volatile profiles among Prunus rootstock cultivars.