Dec 4, 2008
Growers Plan To Replant Some Orchard Sites Lost To Plum Pox

Tim Weiser plans to plant 7 acres of stone fruit next spring, and some of his neighbors are planting, too.

That’s a big deal in Adams County.

Adams County, the biggest producer of stone fruits in Pennsylvania, was the hot spot where plum pox was discovered in September 1999. This “first ever in the U.S.” discovery spurred state and federal governments to implement an aggressive eradication program.

Weiser Orchards, York Springs, Pa., was the third farm to lose all its peaches, plums, nectarines and apricots. Trees were ripped out in 2002, and for six years Tim has been buying stone fruits to keep his farm market supplied. Vegetable and field crops grow on the 44 acres he lost to plum pox.

But next spring, he gets to start again.

As a result of the discovery of plum pox in Pennsylvania, several growers lost their orchards or the right to plant new ones. In all, 1,614 acres of peaches, plums, apricots and nectarines were destroyed and thousands more acres were quarantined. Finding one plum pox-positive tree put a 10-mile circle on a quarantine map. Besides leading to tree removal, it meant no new plantings of these stone fruits could take place in those areas.

Grower Jim Lerew gets the credit for bringing plum pox to the world’s attention. It was not found initially through government survey work but by the eyes of a grower who – three years before the diagnosis – knew something was wrong with his peaches. When he brought samples to a peach meeting at Rutgers in 1999, a scientist who had been to Europe recognized the disease, which has devastated the industry there and infects some 100 million trees.

The diagnosis brought in state and federal officials – and the quarantine. In March 2000, four Adams County growers received orders to destroy their trees: The Lerew Brothers lost 150 acres, Jim Lott at Bonnie Brae Fruit Farm in Gardners lost 227 acres, Peters Orchard in Gardners lost two-thirds of its peaches and Tim Weiser lost all of his – except 16 trees of a sport variety he was nurturing at another location.

Adams County contained nearly half of Pennsylvania’s 6,500 acres of stone fruits (excluding cherries), and it is home to Adams County Nursery, owned by the Baugher family. In 2000, that fruit tree nursery complied with the eradication program and destroyed 150,000 trees and lost the use of some land and propagation material. To save the business, the Baughers moved their stone fruit operation to Delaware.

Tree testing has been going on intensively since 1999. In 2006, the state agriculture department collected 216,688 samples and found six that tested positive for plum pox. In 2007, it tested 220,164 samples and found zero infected trees.

It was the first year in eight years of surveys that no infected trees were found in the state. In the first year, 2000, 399 infected trees were found in 52,562 samples.

Last year was also the third year of negative data in several discrete quarantine areas. The total quarantined area in Pennsylvania is less than 50 square miles now – and many previously quarantined areas are open for replanting.

Planning to replant

So, now Tim Weiser is going to replant and get back to growing stone fruits.

His neighbors at Peters Orchards and Bonnie Brae started replanting last year.

Scientists and Extension leaders in Pennsylvania saw the replant day coming and welcomed it as an opportunity.

“All new orchards offer the opportunity for a ‘fresh start,’” they wrote in a paper called “Replanting stone fruit in sites previously affected by plum pox.” They put together guidelines that growers can follow as they get the opportunity to do it all over.

John R. Peters, son of John F. and grandson of founder John B., who gave the name to the multi-generation, multi-family John B. Peters Inc., said growers in the peach business have to stay current on new varieties. Peach orchards turn over faster than apple orchards, so many of the lost orchards were relatively young. They don’t need or intend to make major changes.

“We were fortunate,” he said. “Some of the growers lost all of their peaches. We lost about two-thirds but we had some orchards 15 miles away. Losing the trees disrupted our business, but we still had peaches to sell. We have less volume now, but we still have our markets.”

They sell wholesale and through their own retail market. The Peters – there are seven cousins in John R.’s generation involved in the business – grow about a thousand acres of fruit, mostly apples. Some of the plum pox sites were replanted to apples and some went into row crops during the six years since their stone fruit trees came out.

Weiser intends to make a few changes from what he used to do.

First of all, he’s not going to plant any mid-season peach varieties. There are plenty of those in the ground already, he said, and he’ll continue to buy them from other growers. He will plant early and late varieties that stretch out the season for his farm market.

He’s going to plant a mix of yellow- and white-fleshed varieties of both peaches and nectarines. He’s going to plant plums and apricots, and also apriums, the apricot-like cross between an apricot and a plum.

“We’ve got a real market for them,” he said.

When he lost his original orchard, he lost pluots, the plum-like fruit that results from “the other way” cross between a plum and an apricot. The pluots, he said, were hard to manage, and he won’t plant those again. Apriums work better for him. He’s also looking closely at other crosses being developed at Floyd Zaiger’s Nursery in California, where the stone fruit crossbreds were created.

The orchards Weiser lost in 2002 were pretty modern, he said – good varieties growing with trickle irrigation. They were in their sixth and seventh years, just coming into mature production.

“It was like we took $300,000 and put it in a hole and buried it,” he said.

The state and federal government cooperated in a program that compensated growers for costs of removal and lost income.

“I don’t intend to plant for wholesale again,” he said – another lesson learned.

When he had 44 acres, he sold peaches wholesale. After losing the trees, he bought about 3,000 half-bushels of peaches each year for his retail market. He figures there is about $4 more to be made from a retail basket of peaches than a wholesale basket.

Weiser intends to train the trees to a traditional open vase system, because he wants short trees easily harvested from the ground. The land is hilly and not well adapted for mechanization using platforms and is not ladder-friendly, either.

Since the trees were taken out, the land has been in corn and soybeans. This vacation from fruit should help, although the orchards he lost were on virgin sites when they were planted in the ’90s. Replant diseases and nematodes should not be a problem, he said.

“We shouldn’t need to fumigate before we plant.”

At Peters Orchards, soil tests showed that nematodes would not be a problem after six years in row crops.

The elapsed time has brought other changes for Tim Weiser. Now 58, a son has expressed interest in joining him in the fruit business.

“We’d like to build a new market,” he said.

He plans to gradually plant more stone fruits as he determines what sells best through the retail market.

Besides the stone fruits, they grow 140 acres of apples, 4 acres of blueberries and 20 acres of vegetables, plus pumpkins and chrysanthemums. Everything sells out of the 70- by 80-foot market building between June and December.

Recommendations

Penn State Extension specialists – as well as some from other institutions like Rutgers University in New Jersey – put their heads together to give growers some ideas as they make replant decisions.

Penn State nematologist John Halbrendt deals with site renovation and preparation issues. Pomologist Jim Schupp works with orchard design. Adams County has a team led by Extension educator Tara Baugher helping growers with orchard designs and tree styles like the perpendicular V that might lend themselves to mechanization in the future – machines like platforms for pruning, thinning and harvesting and mechanical fruit thinners.

At Rutgers, Jerome Frecon maintains a list of the best varieties for the area, both those with established records and those looking good in trials.

Schupp has recommendations for growers managing horticultural risks:

∑ Choose the best new varieties.

∑ Pre-order trees to make sure you get what you want, of the best quality and the best price. There is competition for good varieties and high grades of trees, so ordering and making a deposit two years ahead may be needed to reduce the risk of not having the trees you want to plant when you want to plant them.

∑ Choose a good orchard array and row placement. The best choices are north-south rows, planted in square blocks of 5 acres or more for best use of mating disruption in pest control, on fairly level sites and avoiding planting in old tree rows. Plant in the old drive rows instead.

∑ Provide irrigation for improved tree growth and establishment and to obtain larger fruit.

∑ Choose a system – open vase or V – that will work best given your labor and management system. Open vase has low establishment cost and permits most work to be done from the ground, without ladders. However, high-density systems like the V come into production earlier and are simpler to thin and prune, even though they need ladders or platforms from which to do the work.

Healthy orchards

While the government reaction to plum pox virus was massive and firm, growers often live with virus problems in their stone fruit orchards. Plant pathologist John Halbrendt took the plum pox “opportunity” to tell growers there are probably 40 other viruses that also damage their orchards and their fruit.

Some of these may be resident in roots and soil from previous orchards.

“A replant problem caused by a biotic agent is often referred to as a replant disease,” he wrote in a Penn State bulletin called “Important Steps to Replant Success.”

“Replant problems are caused by changes in soil conditions resulting from years of monoculture.

“The agents responsible include pathogenic fungi, bacteria, parasitic nematodes and viruses. Some organisms such as the fungus Armillaria and the root-lesion nematode are highly pathogenic and will infect healthy seedlings, while weaker pathogens often require conditions that predispose trees to disease such as cold injury, poor nutrition or wounds caused by nematode feeding. Several complex diseases require pathogen interaction such as virus transmission by dagger nematodes.

“A few diseases such as stem pitting and root rot are lethal, but most are debilitating, resulting in trees that simply cannot grow or yield to their full potential.

“Replant diseases are insidious because they may occur on sites where the previous orchard appeared healthy. This can happen because mature trees with an extensive and well-developed root system can tolerate a low level of disease, and pathogen populations can build up undetected. It is when the old orchard is removed and new trees are replanted that the pathogens overwhelm the small root system of the young trees.”

Another cause of replant problems is soil degradation from previous orchards. Years of herbicide application under trees reduces soil organic matter. Other kinds of chemical sprays can result in nutrient imbalances, pH reductions and soil residues. Old, decomposing tree roots can release allelochemicals.

“These problems are not easily recognized or corrected,” he said.

In a nutshell, Halbrendt recommends remediation of the soil and then the purchase of certified virus-free trees – and this advice applies whatever the reason an orchard is removed and a new one planted.

Orchard renovation begins with the removal of old trees, getting out as much of the old root debris as possible and then using herbicides if needed to control sucker re-growth from roots. He recommends subsoiling and taking at least two years between orchards, growing other crops to produce organic matter and choosing some, like mustards with fumigant properties, that suppress dagger and root lesion nematodes and soilborne fungi.

Because so many of the causes of “replant problems” are unknown, fumigation is often used as insurance.

Since fruit trees are harder to fertilize than annual crops, it’s a good time to incorporate fertilizer and lime. Growers should control weeds and be careful to eliminate virus and nematode hosts and reservoirs.

Leaving land fallow is not a good choice, he said.

For some growers, plum pox is turning into an opportunity to learn from experience and do everything right as they strive to plant the perfect orchard.




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