Leading Tree Fruit Physiologists Talk About Need For Future Funding

This year’s Cornell 2014 In-Depth Fruit School focused on physiological principles and their application to fruit production and included presentations from leading tree fruit physiologists — including John Palmer of Plant and Food Research in New Zealand, Ted DeJong of the University of California-Davis, Alan Lakso of Cornell University, Duane Greene of the University of Massachusetts, Jim Syvertsen of the University of Florida, and R. Scott Johnson of the University of California-Davis.

“These are six people I look up to,” Terence Robinson of Cornell University said as he introduced the day’s speakers. Robinson served as moderator for the event.

Here are some highlights from the presentations:

John Palmer
Palmer’s presentation highlighted the research he’s conducted over the course of his career. But, what Palmer stressed most was how growers need to improve the consumer’s eating experience by targeting an apple’s dry matter.

“You can ruin a market by giving them something that doesn’t taste good,” Palmer says. “There are concerns with [getting] high yields but neglecting eating quality. The challenge is to increase and maintain yields and eatiblity.”

Dry matter consists of carbohydrates — including starch and sugars — and acids. Fruit quality is determined by the amount of carbohydrates that accumulate in the fruit.

“The packaging of dry matter into a fresh fruit form is one of the most critical parts of fruit growing,” he says.

Palmer says that a fruit with high dry matter concentration must be harvested at the proper stage of maturity and then stored in an optimal condition where firmness and acidity are conserved.

A key challenge for growers will be to use dry matter concentration as a fruit quality index and then use that index to control and manipulate optimal fruit quality.

Ted DeJong
DeJong’s presentation focused on pruning cuts, blossom thinning, and growth potential in peaches in California.

Warm springs will likely result in smaller fruit sizes and smaller yields, and because of this, DeJong recommends early fruit thinning practices to increase fruit size and yield. This allows the tree to better use its resources and nutrients to the remaining fruits.

“Growers should be thinning early and hard in a warm spring,” he says.

DeJong cautions growers to be mindful of growth potential and the repercussions for missing the thinning window.

“If you miss that growth potential window, you’ve missed it,” says DeJong.

Alan Lakso
Light distribution in the tree is a cause of variability within the canopy, Lakso says. Spurs need light the first month after bloom and he says orchard yield is determined by light interception by spurs.

He recommends maintaining an open canopy to increase light distribution.

“Excessive shade during the season reduces leaf photosynthesis ability irreversibly, even if re-exposed,” Lakso says.

Lakso also says that summer pruning should be avoided because it reduces the tree’s function and light interception and can lead to poor fruit sizing.

“The canopy responds to full light differently,” he says.

Duane Greene
“I challenge you to re-visit blossom thinning,” Greene says. “It can aid in the prevention of biennial bearing of varieties and increase return bloom.”

Green’s presentation focused on the Fruit Growth Model that he developed with the help of Alan Lakso, Terence Robinson, and Phil Schwallier. The fruit growth model was designed to aid growers in calculating the effectiveness of chemical thinning. Generally, Green says, more than one application of blossom thinning is needed.

Greene recommends tagging spurs that are a good representation and distribution on the tree. Those tagged spurs will be used in the growth model for predictions of the entire block of trees. For precision’s sake, Greene suggests growers measure between 50 and 80 spurs.

During research, the team found the fastest growing fruit on the spur was most likely to remain on the tree. Greene and his contributors selected three fruit on seven trees for calculating purposes and found the results to be 99% accurate. Fruit that slows to a 50% growth rate or less will stop growing and abscise. He says fruit will grow between 0.6 and 0.9 millimeters a day.

Greene says measurements should be made after a thinning spray between 4 and 6 days after application. Growers might wait a few more days if cold weather follows a thinning spray.

Jim Syvertsen
Syvertsen’s presentation focused on water and irrigation issues as he’s studied them in Florida.

“Water is the most important plant growth regulator,” says Syvertsen.

Water, he says, performs three basic functions: it mediates environmental effects on growth and metabolism; correlates growth of different parts of the plant; and integrates growth and metabolic activity in the cellular level. He says that the effects of plant growth regulators can be attributed to a plant’s ability to control water budgets.

Syvertsen says the focus should be on root efficiencies, not root growth, saying, “We’re not growing carrots.” Maximizing root efficiencies will help the plant absorb the nutrients needed.

R. Scott Johnson
Johnson’s research focused on how to get nutrients into the tree as efficiently as possible and how to evaluate the need for nutrients.

He says there is a need for better root densities, especially in peaches, to absorb and supply the tree with nutrients.

Based on his research, there is a need to apply nitrogen in the ground for peach tree roots. However, he says a fall spray of foliar urea is an effective way to supply the tree with some nitrogen.

Johnson also recommends combining the urea spray with a sulfate spray in peaches.

“We still haven’t found any physiological disorders in peaches,” Johnson says in regard to calcium applications. He says foliar sprays of calcium offer no benefit to peaches.

Stressing the Need For Funding
During each presentation, these leading physiologists stressed the need for funding in order to continue the study of tree fruit physiology.

“It’s a shame that taxpayers are withdrawing funds for research. This research can’t be completed with grants alone,” Lakso says.

DeJong says physiologists now spend a majority of time writing grants to continue research. He notes that only 5% of submitted research proposals will receive funding from the USDA.

“Before we can do anything, we have to have funds. It’s going to change things. We don’t have near the thinking time that we need,” DeJong says.

Green agreed by noting, “Not one of us would trade being in the field — interacting with people and asking questions to get answers.”

John Palmer opened his presentation with what he calls John’s Law of Modern Science: “Law No. 1: No money equals no research. Law No. 2: No money equals no researchers,” he says, advising growers to put a focus on funding for research in order to improve the industry.

Johnson told the growers in attendance, “Use your influence to get whole plant physiologists back in research at land grant universities. There is a great need for plant physiologists. I don’t think molecular biologists will solve these plant and nutrient issues,” he says.

Hamlyn Jones of the University of Dundee in Scotland joined the six presenters in a wrap-up panel. His thoughts summed up the great need for research and education.

“The future of fruit growing depends on the training we give young growers and scientists,” Hamlyn says. “They need a broad understanding of physiological, molecular biology, and engineering.”