2018 ASHS Annual Conference

A novel hydrophobic plant cuticle supplement (HydroShield) was developed by the authors and patented by Oregon State University. HydroShield is at least 90 μm thick and simulates xerophytic plant cuticles, slowing the movement of water out of leaves and fruit. 'Sweetheart' sweet cherry trees in the Dalles were subjected to 0.61 gal per hour drippers (no HydroShield) as a check, 0.61 gal per hour plus 3 applications of 1% HydroShield, 0.53 gal per hour (13.1% reduction) plus 3 applications of 1% HydroShield, and 0.42 gal per hour (31% reduction) plus 3 applications of 1% HydroShield. Trees were sprayed to the point of run-off with a Rears mistblower applying 100 gal of water per acre at a maximum speed of 2 mph. Trees were irrigated daily for 4 hours from 05/12/17 till harvest. Soil moisture was monitored using a neutron probe. At harvest, fruit cracking, yield and quality were evaluated for the different treatments. No differences in fruit quality or yield were observed between the different treatments. In Milton-Freewater, 'Gala' apples were sprayed to the point of runoff with 1% HydroShield plus 1% Cuevo® at 'pink stage' of bloom and again two weeks later and other trees were sprayed on the same days with 1% Cuevo only as an check. Fruit size was measured 7 times on the same 5 fruit on 5 trees each for both treatments over the growing season and again at harvest. Fruit sprayed with 1% HydroShield plus 1% Cuevo were significantly larger by 10.6% (P<0.001) than those fruit sprayed only with 1% Cuevo. In addition, 'Braeburn' apple trees were sprayed twice with 1% HydroShield at fruit set and again 2 weeks later. Trees were irrigated twice weekly for 15 hours total with four drippers per tree. Irrigation treatments included: - a check with drippers emitting 1 gal per hour, dripper emitting 0.75 gal per hour plus HydroShield and drippers emitting 0.5 gal per hour plus HydroShield. Soil moisture was monitored at depths of 10, 20, 30 and 40 cm in the soil profile. At harvest yield per tree was estimated and fruit size and quality were evaluated for all treatments. There were no significant differences observed in the yield or fruit quality between the different treatments. Soil moisture was not significantly impacted by either of the reduced irrigation regimes compared to the untreated check. A similar trial on wine grapes using own-rooted Clone 8 'Cabernet Sauvignon' was irrigated according to deficit irrigation practices and there were no differences in yield of fruit quality between those vines that received 1 gal per hour and those that received either 0.75 gal or 0.50 gal per hour plus 4 applications of 0.5% HydroShield. Soil moisture of the 1.0 gal and 0.75 plus HydroShield were similar at all depths in the soil profile. The 0.5 gal per hour soil moisture at 40 cm started drying up towards the end of the growing season. Whether or not this results in a problem in subsequent years remains to be seen. Precipitation in the Pacific Northwest occurs predominantly in the winter months and this is expected to recharge the water table but multiple years of testing are required to confirm this. Where wine grape fruit quality was concerned, only titratable acidity (TA) was significantly higher in grapes that received 0.75 gal per hour compared to the check and 0.5 gal per hour treatments. Results to date indicate that HydroShield has the ability to reduce water usage in apples, sweet cherries and wine grapes without negatively impacting yield or fruit quality. A 25% reduction in irrigation water plus HydroShield did not affect soil moisture content in 'Braeburn' apples, or 'Cabernet Sauvignon' wine grapes. A 13% reduction in irrigation water in 'Sweetheart' cherries also did not affect fruit quality or yield. A 50% irrigation reduction in 'Braeburn' apples and 31% irrigation reduction in 'Sweetheart' sweet cherries also did not affect yield, fruit quality or soil moisture content. A 50% reduction in irrigation water under deficit irrigation of 'Cabernet Sauvignon' did not affect yield or fruit quality in year one but may have an impact on the soil water table in subsequent years, which may result in lower yields and altered fruit quality. The research is ongoing.