Midwest Tree Fruit Spray Guide - Iowa State University Extension ...

Step 1
Calculate feet row/acre
43,560 sq ft/acre = feet of row/acre
between row spacing (ft)
Step 2
Calculate cubic feet of TRV/acre.
Feet of row/acre (from Step 1)
x tree height (ft)
x cross-row limb spread (ft)
= cu ft of TRV/acre
Step 3
Select density factors from Table 3.
Select the density factor that best indicates
the canopy density of each separate
orchard or block.
Step 4
Calculate TRV gallonage/acre
cu ft of TRV/acre tree density
(from Step 2) x (from Step 3)
1,000
= gallons of dilute solution applied per acre
= TRV gal/acre
Table 3. Determining density factors using tree density estimates.
0.70 gal/1,000 cubic feet Trees extremely open light visible through entire tree, less than 15 scaffold limbs per tree,
young trees
0.75 gal/1,000 cubic feet Trees very open 18 to 21 scaffold limbs per tree, light penetration throughout the tree,
healthy spurs within the tree canopy
0.80 gal/1,000 cubic feet Trees well pruned adequate light in trees for healthy spurs throughout trunk and scaffold
limbs, many holes in foliage where light can be seen through tree
0.85 gal/1,000 cubic feet Trees moderately
well pruned
MIDWEST FRUIT TREE SPRAY GUIDE
6
EXAMPLE
An orchard has rows spaced 20 feet apart, tree height
is 14 ft and the cross-row limb spread is 12 ft. The tree
density is 0.85.
Step 1
43,560 square ft/acre / 20 ft
= 2.178 feet of row/acre
Step 2
2,178 x 14 ft x 12 ft
= 365,904 cubic feet of TRV/acre
Step 3
Density has been given as 0.85.
Step 4
(365,904 x 0.85) /1,000
= 311 TRV gallons/acre
For additional information on calculating TRV gal/acre
refer to the Ohio State Extension Bulletin 892 Orchard
Spray Rates: How to Determine the Amount of Pesticide
and Water to Use in Your Orchard by C. Welty.
reasonable spur population within canopy, tree thick enough that light
cannot be seen through the tree
0.90 gal/1,000 cubic feet Trees minimally pruned spurs inside canopy are weak due to limited light, very few holes where
light can be seen through the tree
1.00 gal/1,000 cubic feet Trees unpruned extremely thick, no light visible anywhere through tree canopy,
trees more than 20 feet high
Spray Tank pH
Several pesticides break down rapidly in alkaline
water. In a matter of hours (or in extreme instances
only minutes), 50 percent or more of the active
ingredient may be hydrolyzed to yield a less active
compound. Captan, Carzol, Dimethoate, Imidan,
Kelthane, and Malathion are examples of compounds
that are especially vulnerable to alkaline hydrolysis.
To ensure the maximum effectiveness of pesticide
applications, check the pH of spray mixes in the spray
tank and add buffering agents, if necessary, to adjust
the pH to neutral (7). Buffercide, Buffer-X, Unifilm B,
and LI 700 Acidiphactant are examples of such
buffering agents.
Pesticide Compatibility
Pesticide compatibility in the spray tank is usually
not a problem with newer pesticides. Compatibility
of some materials may depend upon solvents and
emulsifiers used by the manufacturer. Emulsifiable
concentrate formulations are more likely to cause
compatibility problems than wettable powders. If
wettable powders are mixed with emulsifiable
concentrates, incompatibility may result. Compatibility
problems are often noted with lime, copper (Bordeaux),
or oil products are used in a mix. Be aware of spray tank pH
as noted above.
Read the comments section in this spray guide for notes on
compatibility problems and read the pesticide label before
tank mixing products.
Standard Protectant Program
versus Extended Protectant Program
The standard protectant program requires that fungicide
application begin at green tip and the interval between
sprays should not exceed 7 days through primary scab
season (green tip through first or second cover). This is
in contrast to the extended protectant program (see
page 8) that could be used when a sterol inhibiting
fungicide in combination with an effective protectant
fungicide could be applied on a 10-day or longer interval.
The loss of the curative activity from the sterol inhibitors
means we must rely primarily on fungicides with protectant
activity. The strobilurin fungicides (Sovran and Flint) have
limited curative activity (possibly 48 hr) and cannot be used
effectively in an extended protectant program. In addition,
we may be experiencing reduced sensitivity and eventual
resistance in the scab fungus to the strobilurins.