Spring Is Ideal For ProGibb LV Plus® Application

  • Feb 26, 2021

ProGibb LV Plus® (gibberellic acid; GA) —a low volatile organic compound formulation designed to increase avocado fruit size and yield — is approved for use on avocado, including in certified organic orchards. According to the California Avocado Commission’s March 2020 grower survey, which examined growers’ experience with using GA, an increasing number of growers are using GA and to date no users have reported any negative effects of GA application.

Because spring is the ideal time to apply ProGibb LV Plus®, we are sharing application best practices.

Timing

  • Apply the foliar spray during the cauliflower stage of inflorescence development, when 50 percent of the inflorescences on 50 percent of the bloom is at this stage
  • If you are unable to time the application as noted above, it is better to make a slightly late application as it will have better efficacy than an application that is too early
  • Do not apply when the majority of trees are in full bloom as the applications will be ineffective

Spray Volume and Dilution

  • The maximum allowable dose is 25 g active ingredient/acre for all modes of application; doses above or below this are not effective
  • If applied like a pesticide spray, focus on spraying the developing inflorescences and avoid run-off
  • For ground applications, use 12.5 fluid ounces of ProGibb LV Plus® in a spray volume of 100 gallons of water/acre and avoid run-off
  • For aerial applications, use 12.5 fluid ounces of ProGibb LV Plus®  in 75 gallons of water/acre

Spray Solution pH

  • The ideal final pH of the spray solution is 5.5 – 6.0, thus the pH of water should be adjusted accordingly

Wetting Agent

  • Widespread Max® or Silwett L-77® at a final concentration of 0.05 percent is ideal as a wetting agent; similar organosilicone type surfactants can be used as well

Grower Experiences with GA

According to the Commission’s GA grower survey, growers who did not utilize GA cited their uncertainty about whether it could be used for organic production as the primary reason. It is important to reiterate ProGibb LV Plus® is National Organic Program compliant and is registered with the Organic Materials Review Institute.

From 2018 – 2020, the majority of California avocado grower GA applications were aerial, while the remaining one-third of growers applied GA by ground. For those making ground applications, all respondents used 100 gallons per acre spray volume in 2018 and 2019, and 20% said they used less than 100 gallons in 2020. 

Twenty percent of users have tank mixed something other than the recommended surfactant with GA in each of the three years. Boron, phosphites, and micronutrients (manganese, zinc and iron) are the commonly reported tank mixes. It should be noted the use of boron in combination with GA is not recommended on a large scale because both GA and boron are bloom/fruit set enhancers and it is unknown if they work synergistically or antagonistically.

In 2018, about 60% of users reported leaving some trees untreated for comparison, but in 2019 and 2020 only 40% reported leaving untreated trees. It is always best practice to leave some trees untreated for comparison so you can determine whether the product is effective under your treatment conditions. It also is a precautionary step in the event something should go wrong with the application.

For those who applied GA in 2018, 40% reported a yield increase and 60% reported the yield remained the same at harvest in 2019. However, for 2019 applications, 60% reported a yield increase and only 40% reported that yields stayed the same. In 2018, some applications may have been made too late because the SLN registration was not available until the end of March. Increased fruit size was reported by about 50% of users following both the 2018 and 2019 applications.

The majority of users (86%) reported satisfaction with GA and plan to continue using it on their groves. For those who were not satisfied with the results, the lack of a response and the difficulty of application timing were cited as the reasons.

For more complete information concerning ProGibb LV Plus®, read “ProGibb LV Plus® Plant Growth Regulation to Increase Fruit Size and Yield of Avocados” in the Summer 2018 issue of From the Grove or “Application Instructions for ProGibb LV Plus® Plant Growth Regulator“ in the Spring 2019 issue of From the Grove.

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