A tiny thrips adult on a peach

Unfortunately, after a year of limited yield, yet minor pest activity, this season is already becoming an interesting one. I have had several reports of thrips causing considerable “silvering” damage (see example below). With the severity and extent of the damage we have seen in certain places, I just wanted to alert everyone to this potential problem and provide some advice on how to mitigate it.

“Silvering” damage from thrips feeding

The key species of thrips found in southeastern peach orchards are the Western flower thrips. These thrips are small, slender, winged insects with amber or yellowish-brown to dark brown females that are approximately 1 mm long, and the males are smaller and light yellow. Thrips have rasping mouthparts that are used to pierce into plant tissues and ingest the sap. Western flower thrips populations begin to increase in abundance in orchards just prior to peach bloom and have up to 5 generations a year, with several different generations active in orchards at any given time. However, Western flower thrips are generally only a threat to peach production during bloom or just before harvest. 

During bloom, the adults and larvae feed on flower parts, as well as developing fruitlets beneath the shuck which results in russeting or shallow brown scars (see image below). 

As the fruit develops and begins to color prior to harvest, adults move from other host plants (usually weeds or grain crops) to the peach trees to feed on new leaves and ripening peach fruit. At high populations, thrips will feed on young, succulent leaves, causing the leaves to wrinkle and curl as they mature (see image below). 

In addition, adults and larvae will feed on the cells of the fruit skin, which causes “silvering” of the fruit (see image below). 

L to R: Russetting, leaf curl, and silvering

Right now, we are primarily seeing the curling leaves and silvering of the fruit. Sadly, at this timing, there are not a lot of options to manage Western flower thrips in peaches. While we obviously cannot fix the damage that already occurred, by monitoring the fruit we can assess whether a chemical application is needed to stop further damage from taking place. 

Visually inspect the fruit and count the number of adult thrips on 10 fruits per 5 sites in an orchard, particularly focusing on fruit from lower 1/3 of canopy. If there are 5 adult thrips per 50 fruits plus considerable silvering, then a chemical treatment may be needed.

With varieties that being picked and/or are going to be harvested soon, our best options for thrips management are going to be Delegate WG (7 oz/acre) or SpinTor 25C (8 fl oz/acre), which both have 1 day PHI for peaches and nectarines (7 days for plums). Another option would be Exirel (20.5 fl oz) which has a 3 day PHI.

With varieties that still have time before harvest, there are chemistries that can help suppress thrips populations, but also have longer PHI periods. Additional options include Assail 30SG (8 oz/acre) which has a PHI of 7 days, Closer SC (5.75 fl oz/acre) or Brigade WSB (32 oz/acre) which both have PHIs of 14 days. And if there is a variety that is a way off from being harvested, but there is a risk of mites and thrips, Agri-Mek SC (4.25 fl oz) has been shown to suppress thrips, but also has a PHI of 21 days. Please make sure to always read the label prior to making any application to check current rates and restrictions.

Thrips quickly and readily develop resistances to insecticides. If pressure from thrips becomes severe enough to warrant insecticide applications, it is important to rotate the classes, utilizing different Modes of Action.

Good luck everyone! If there is anything I can help with or clarify, please let me know.

Here’s to a great rest of the season!


Thrips management options:

Trade Name*Rate/acrePHI (days)
Delegate WG7 oz1
SpinTor 25C8 fl oz1
Exirel20.5 oz3
Assail 30SG8 oz7
Closer SC5.75 fl oz14
Brigade WSB32 oz14
Agri-Mek SC4.25 fl oz21
*Always check the label for current rates and restrictions.

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