By Peter Murphy

BRASILIA, Sept 14 (Reuters) - With drought causing plants
to shed leaves, coffee trees in world top grower Brazil will
fail to reach their full productive potential in the 2011
harvest, agronomists told Reuters on Tuesday.

Leaves produce the energy the trees need to form the coffee
fruit, but agronomists said the more foliage they lose, the
less they will be able to produce. And, they warned, the rains
must come soon to avoid significant losses to the crop.

"The plant can (abort) some of its production because of
insufficient photosynthesis and an imbalance in the ratio of
leaves to fruit," said agronomist Emerson Tinico of the
Cooparaiso cooperative in Minas Gerais, the Latin American
country's top coffee state.

"There are leaves falling from the trees and this will
affect production," he said. But, he cautioned, it was too soon
to predict a smaller-than-usual harvest at this early stage if
less-afflicted regions manage to compensate.

Coffee futures shot up to their highest in 13-1/4 years in
New York last week, due to concerns that dry weather could
persist well into the usual flowering period, which spans late
September to December since the blossoms appear in waves.

The December arabica futures contract <KCZ0> closed Tuesday
at $1.953 per lb, up 6.15 cents or 3.25 percent.

Agronomists at cooperatives in coffee regions from near
northern Sao Paulo to robusta-growing Espirito Santo said they
were worried the drought could deal a blow to the crop if the
rains, which usually return in late September, did not arrive
soon.

"There are plants losing leaves and with a burnt
appearance. It is a generalized problem," agronomist Joaquim
Goulart of the world's largest coffee cooperative, Cooxupe,
told Reuters.

He said even if rains returned now, the trees would not
make a full recovery because they had gone months without
rain.

"With no moisture reserves in the soil, the plants are
feeling the effects," he said.

NO RAIN FORECAST

Data from weather forecaster Somar shows long strings of
zeros for the rain forecast in Brazil's coffee zones and there
is still no sign of notable showers in sight apart from a
sprinkle in two areas that would have little or no impact.

"The latest forecasting models still show another cold
front between the 22nd and 25th but they don't indicate
significant rainfall in the coffee areas," Somar said in a
coffee weather bulletin on Tuesday.

Whatever the weather, the next harvest in the world's top
coffee grower is already certain to be smaller than this year's
47.2 million 60-kg bag crop, due to a cyclical dip in output
every other year. The last small crop, in 2009 for example,
produced 39.4 million 60-kg bags.

Faring better are farms in northern Espirito Santo, the
main robusta growing state, which have been protected by
irrigation during the flowering phase. Flowering is already now
well advanced as it occurs weeks earlier than for arabica.

But if the La Nina weather anomaly, which has formed and is
behind the dry conditions in the region, manages to keeps rain
at bay for long enough, Espirito Santo too will eventually
suffer.

"Producers are irrigating constantly and this is causing
the ponds to dry up. If it doesn't rain by November when the
beans are filling out, they will be very small," said
technician Delson Schramm of the Cooabriel cooperative.

"Even with irrigation the plants don't develop as well as
with rain," he said.
(Reporting by Peter Murphy; Editing by John Picinich and Lisa
Shumaker)