Suppress Nematodes, Upregulate Sugar Metabolism to Increase Yield and Improve Grape Quality

S. Kaan Kurtural PhD Senior Agronomy Information Technology Manager

Employ is a biochemical pesticide that is foliarly applied that can help plants overcome the effects  of nematode feeding in vineyards. In multi-year, multi-site trials Employ was shown to improve net leaf photosynthesis, plant water status, yield, sugar accumulation in berry as well as plant secondary metabolites such as anthocyanins in black skinned wine grapes. 

Employ is a second-generation αβ Harpin protein. These proteins are produced by many pathogenic bacteria that can signal the plant’s immune system to upregulate its defense pathways. This resulted in improved leaf photosynthesis therefore improved growth and amelioration of berry composition including greater amounts of phenolic biosynthesis. In replicated independent trials  (176PS23VINCA1) the results indicated a reduction of nematode populations in rhizosphere (Figure 1), increased leaf photosynthesis throughout the season (Figure 2), greater yield (Figure 3), higher Brix (Figure 4) and higher anthocyanins in berry skin (Figure 5) in wine grapes grown on susceptible Coudrec 3309 rootstock in California at two different sites.

Figure 1. Root knot and ring nematode counts in grapevine rhizosphere before and after Employ application 2023-2024
in Solano and Santa Barbara Counties in California (p<0.0001). 176PS23VINCA1

Figure 2. Improvement of net leaf photosynthesis over the growing season 2023-2024 with Employ application in Solano and Santa Barbara Counties
in California (p<0.0001). 176PS23VINCA1

The suppression of nematode feeding on roots of grapevines led to:

• 35% greater net leaf photosynthesis
• 30% greater yield per acre

Figure 3.  Effect of Employ on yield of grapevine 2023-2024 in Solano and Santa Barbara Counties in California (p<0.0001) 176PS23VINCA1

There is consensus that greater leaf photosynthetic activity would lead to higher sugar export from grape leaves during ripening. Likewise, due to nematode suppression and higher photosynthate export led to greater sugar loading in grape berries. 

Figure 4.  Effect of Employ on grape berry Brix in 2023-2024 in Solano and Santa Barbara Counties in California (p<0.0001). 176PS23VINCA1

There is a direct linear relationship between sugar accumulation grape berry and anthocyanin (color) formation in the skin.  Likewise, due to nematode suppression, and better sugar loading into the grape berry; higher skin anthocyanin was achieved in Cabernet Sauvignon and Pinot Noir berries (Figure 5).

Figure 5.  Effect of Employ on on grape  berry skin anthocyanin (mg/berry) 2023-2024 in Solano and Santa Barbara Counties
in California (p<0.0001). 176PS23VINCA1

Best use recommendations for Employ on Grapevine

Timing	Rate
Post-Harvest	2 oz/Acre
3-5 mm Berry	2 oz/Acre
Bunch Closure	2 oz/Acre
Verasion	2 oz/Acre

Field comparison of Untreated Control and Employ applied at 2 oz/Acre.