TABLE 4.1. Trees Sprayed per Minute at Various Rates of Travel

1.5

2.0

2.5

132

176

220

13.2

17.6

22.0

11.0

14.6

18.3

9.5

12.6

15.8

8.2

11.0

13.7

7.4

9.8

12.3

6.6

8.8

11.0

6.0

8.0

10.0

5.5

7.3

9.2

5.1

6.8

8.5

4.4

6.0

7.3

3.8

5.0

6.3

3.026426.422.019.016.514.713.212.011.010.28.87.5

Determining High Volume Spray
Requirements Based on TRV

The spray volume required for uniform coverage of an
orchard depends on the total fruit and foliage surface
available. One way good coverage can be obtained is to
use high-volume (HV) dilute sprays of 200 to 400 gallons
per acre (gpa) to thoroughly wet all target surfaces to a
point where excess spray liquid drips to the ground. This
is important where absolute coverage of all surfaces is
required (for example, oil sprays for mite control and for
certain plant growth regulators). Underdosing does not
occur because all parts of the tree are thoroughly wetted.
Overdosing does not occur because any excess material
runs off. Obviously, if the spray volume used isexces-
sive, then much is lost to the ground as drip. For trees
with a full canopy of foliage, a dosage volume of about .7
gallon per 1,000 cubic feet TRV will usually reach the
drip point. Early in the season however, sprayers should
be calibrated to deliver between 0.25 and 0.35 gallon per
1,000 cubic feet TRV to avoid excessive runoff. (An
apple tree at green tip has approximately one-fifth the
surface area it will have at full leaf.) If applying sprays
calibrated for dilute application and not reaching the drip
point, the dosage will be less than adequate and control
will be reduced. If the drip point is greatly exceeded,
control will be adequate, but pesticide use will be
excessive both in terms of cost and unnecessary
environmental contamination.

Determining Concentrate and Low
Volume Spray Requirements Based on
TRV

Good coverage can also be obtained using low
volume (LV) sprays of 25 to 60 gpa with which a fine
mist of spray droplets are uniformly deposited over all
target surfaces without reaching the drip point. LV
spraying is now the standard in the fruit industry because
it requires less labor, time, and pesticide than HV sprays.
However, without a visible gauge to determine when
enough material has been applied, such as the drip point
for HV sprays, dosage for LV sprays can be controlled
only by adjusting the pesticide concentration in the spray
tank. An LV rate of 0.09 gallon per 1,000 cubic feet

TRV provides adequate coverage in most orchards under
most conditions. Applying less than this amount may
give less consistent results under variable orchard
conditions because few airblast sprayers are designed for
very low volumes. Applying more than this rate
generally leads to excessive pesticide use and higher spray
costs. See Table 4.2 for suggested spray volumes.
This dosage volume can be used to calibrate the
sprayer to deliver a spray volume suitable for a three-
dimensional orchard target defined by TRV. The
conversion to gpa for sprayer calibration is made using the
following formulas:

Pesticide Concentration Factors

Adjusting the spray volume as described above
improves the overall efficiency of the spraying operation.
However, major reductions in pesticide use and cost
savings are not realized until pesticide concentrations are
also adjusted to control dosage. Recommendations for
LV TRV spraying differ substantially from those provided
on most pesticide labels. The reason for this is that many
testing procedures do not use LV sprays, and very few use
TRV calculations. Most recommendations are calculated

26

1998 New Jersey Commercial Tree Fruit Production Guide