the operating pressure and travel speed used in the test.
This written record will save valuable time during the
spray season when the sprayer calibration may need
adjustment.

Travel Speed Adjustments.The greater the
distance between the sprayer and the spray target, the
slower the travel speed should be. The same is true for
the density of the foliar canopy. Thus, where a travel
speed of 3 mph might be adequate for coverage during the
prebloom period or when spraying from every row
middle, operating at 2 to 2.5 mph will improve coverage
when spraying from alternate row middles or when tree
canopies become more dense. Spraying in the wind is
not advisable but is sometimes necessary. Here again, a
slower travel speed than usual is recommended to
maintain coverage in the tops of trees. Under low
humidity conditions, spray droplets evaporate quickly,
reducing their mass and making it more difficult for them
to be deposited in the tops of trees. Spraying in the early
morning or late evening, when humidity levels are
usually higher, can overcome this problem.

Alternate Row Middle (ARM) spraying.
Conventional sprays are applied from both sides of the
tree rows, with the sprayer traveling down each aisle with
both sides of the sprayer open. Alternate row middle
(ARM) sprays are applied from only one side of the tree

row, or every other aisle, alternating between the odd- and
even-numbered row middles with each successive spray
treatments. Carefully done, ARM sprays offer the
advantages of reduced costs for labor, chemicals, and fuel
and closer timing when conditions are critical.
ARM spraying should not be attempted in orchards
where conventional spraying has not given consistent
control of most pathogens and insect pests. The sprayer
should be matched to the tree canopy in that the sprayer
should be able to cover 100% of the side being sprayed
and about 75% of the side not being sprayed. Trees
should be well pruned to allow spray droplets to penetrate
into and through the tree canopy. Travel speeds should
never exceed 3 mph, even under calm conditions. ARM
spraying programs have been most successful when a
conventional application (both sides) is made at the start
of the season and then followed at regular intervals with
ARM treatments. ARM spray intervals need to be shorter
than where both sides of the tree are sprayed. Where
conventional spraying recommendations call for sprays at
7-, 10-, or 14-day intervals, the intervals for ARM sprays
should be reduced to 3-5, 7, or 10 days, respectively. Be
prepared to shorten the spray interval or even to apply a
complete spray (both sides) when using plant growth
regulators, or when conditions are highly favorable for
disease development, or when precise timing is essential.
Do not use ARM methods to apply streptomycin for fire
blight control.

Sections Adapted from University of Maryland Cooperative Extension.

TABLE 4.4. Total Gallons per Minute Sprayed on Both Sides, Using Different Row Spacings
and Gallonage Rates per Acre, at Speeds of 1 1/2, 2, 2 1/2, and 3 Miles per Hour

30

32

34

1.8

2.0

2.1

2.3

2.4

2.6

2.7

2.9

3.1

3.2

3.4

3.6

3.6

3.9

4.1

4.5

4.8

5.1

5.4

5.8

6.2

5.9

6.3

6.7

6.8

7.2

7.7

9.0

9.6

10.2

13.5

14.4

15.3

18.0

19.2

20.4

27.0

28.8

30.6

36.4

38.8

41.2

1998 New Jersey Commercial Tree Fruit Production Guide

31