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April 22, 2013

Drought effects linger for specialty crops, but cold helped

WEST LAFAYETTE, Ind. - While it might have seemed that the winter would never end, the prolonged cold was good for Indiana's specialty crops compared with last year's early spring, Purdue University horticulture specialists say.

Last year at this time, plants started to develop much earlier than normal because of summerlike temperatures, which left the crops vulnerable to a late freeze. This year, fruit trees, grapes and berries are benefiting from temperatures closer to normal, said Purdue horticulture professor Peter Hirst. It's still too early to know exactly how well they are recovering from the drought and what the 2013 growing season will bring, but the future looks promising for all these crops. Still, there are some lingering effects from the drought that could hinder some plants this year.

* Fruit trees. The fact that winter weather lasted so long is a good sign for this year's fruit tree crops, said Purdue horticulture professor Peter Hirst.

Temperatures below 40 degrees delay crop development, which was ideal for early spring. "Early plant development, and especially early flower development, puts crops at a much higher risk of cold damage from spring frosts,” Hirst said.

The residual effects of the drought are expected to be minimal and might actually benefit fruit growers, Hirst said.

"Fruit crops, especially apples and peaches, were very light last year due to a very warm spring, early flower development and a frost," he said. "Because crops were so light last year, we expect the trees to have produced a lot of flowers; we should see very heavy flowering and the potential for good crops this year."

If this is the case, Hirst said growers would need to pay special attention this spring to chemical thinning, which reduces the number of blooms per branch. This allows the tree to focus its resources on the remaining blossoms and produce larger fruit.

* Grapes and berries. The mild, normal-length winter was kind to grape and berry crops, said Purdue Extension horticulture specialist Bruce Bordelon, and no winter injury is expected. Some effects of the 2012 drought, however, may linger into this year's growing season, including lower fruitfulness and increased damage from chronic diseases or minor pest problems.

"The buds for grapes and berries were established last year during the drought and hot period, so there is a chance we may be less fruitful than normal," Bordelon said.

Grape producers should resist the urge to prune heavily after the drought, instead waiting until shoots begin to grow so they can see whether plants are producing three clusters or one. If they are producing only one cluster, growers might want to prune more conservatively and consider double pruning, especially for early varieties.

Double pruning is the practice of leaving spurs longer than normal during pruning - more than 10 buds on the branch rather than the normal 3-4. This leaves more buds and more chances for a full crop in the event of damage from a late frost. After the risk of frost, growers then prune a second time, reducing the spurs to three buds.

For berries, growers' options are more limited.

"Basically, we're in that situation where we don't know what kind of year it's going to be, and there's no really easy way to tell," Bordelon said. "There isn't much we can do anyway - we can't water to make up for last summer. We just have to wait and see."

Another problem that growers should watch for this year is increased damage from pests such as grape root borer, raspberry crown borer and strawberry root weevil, or chronic diseases such as black root rot in strawberries or trunk disease in grapes. In normal years, adequate moisture and fertile soils keep plants from showing severe damage by these pests and diseases, but plants may show more damage this year due to the added stress of drought, Bordelon said.

If plants show pest damage or begin to die, growers will want to identify the cause and consider treating for the pests, even though they may not have worried last year.

Ultimately, Bordelon said, it's all about good risk management practices. During last year's late frosts, growers who made larger investments in protecting their crops came out of the frost and drought with better crops.

"Last year, there were a handful of growers who had the capability to run overhead irrigation for frost protection," he explained. "One grower had a significant investment in horizontal well structure, lots of flow capacity, and he could run sprinklers over 20 acres at a time - and he ended up having 80 percent of a crop. On his other farm that did not use irrigation, he wasn't able to harvest anything.

"It's all about the risk management approach. Growers should carefully consider the risks associated with fruit production and weigh the cost of risk management practices - such as irrigation, or wind machines for frost protection - against the potential losses that could occur." 

Writer: Jessica Merzdorf, 765-494-8402, jmerzdor@purdue.edu

Sources: Peter Hirst, 765-494-1323, hirst@purdue.edu

Bruce Bordelon, 765-494-8212, bordelon@purdue.edu 

Related website:
Purdue Department of Horticulture and Landscape Architecture

Ag Communications: (765) 494-2722;
Keith Robinson, robins89@purdue.edu
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