1995

PECAN FUNGICIDE EVALUATION

Dr. John Starkey, Cooperator

Joe D. Janak, C.E.A., Anthony Netardus, C.E.A.

Victoria County, DeWitt County

Thomaston, TX (Pct. #2)

SUMMARY:

The new pecan fungicide, Enable, performed equally well in controlling pecan scab to the fungicide Super Tin when both were applied at their label rates. A mixture of both fungicides applied at half their rates provided an increase in scab control in a year with minimal scab infestations.

PROBLEM:

Controlling the fungal disease pecan scab can be a severe problem on pecan trees especially during wet years. Recent grower information has shown that the fungus has shown resistance to some currently used fungicides. New fungicides are needed to control pecan scab.

OBJECTIVE:

To evaluate the effectiveness of "Enable", a new fungicide labeled to control pecan scab.

MATERIALS/METHODS:

In a young pecan orchard, pecan trees, most of which were the Kiowa variety, were divided three ways with every group of 10 trees receiving a different fungicide treatment. (The first application of fungicides, Orbit and Super Tin, were applied on April 6-7, 1995 before this demonstration began.) The second, third and fourth applications of fungicides, applied April 20, May 7 and June 17, 1995 consisted of an evaluation of Enable (8 oz/ac) in comparison with Super Tin (15 oz/ac) plus a mixture of both at half rates. Plots were replicated with evaluations taken from two replications on July 14 and three replications on Sept. 27, 1995.

Pecans leaves and nuts were evaluated on July 14 and September 27, 1995 for scab and aphid infestations. Evaluations consisted of rating five compound leaves on ten trees per replication. Leaves and nuts were rated on a scale of 0 - 5 with 5 representing a heavy scab infestation. Pecan aphids were evaluated on the same scale.

RESULTS/DISCUSSION:

Four factors affected this demonstration negatively. First, the initial Orbit/Super Tin fungicide application on April 6-7, 1995 probably reduced beginning year scab populations. Second, the spring and summer of 1995 were dryer than normal reducing scab occurrence. Third, there was no untreated check to evaluate in comparison to the treatments; and fourth, 12 of the 45 trees were suspected to be varieties other than Kiowa.

Still though, there was some difference between the ratings of the fungicides. The combination of Enable and Super Tin appeared to provide nearly twice the control of scab (See Table 1). There appeared to also be a slight trend to decrease aphid numbers when both fungicides were used together.

Table 1. Evaluation of fungicides on pecans for scab control. Dr. John Starkey, Cooperator, Victoria/DeWitt County, TX. 1995

TREATMENT	RATE OZ/AC	July 14, RATINGS (a)			Sept. 27, RATINGS (a)
		LEAF	NUT	APHIDS	LEAF	NUT	APHIDS
ENABLE	8	17	0	21	31	51	17
ENABLE + SUPER TIN	4 8	9	4	20	16	34	13
SUPER TIN	15	15	0	23	35	36	15

(a) Evaluation of 50 compound leaves, 0 = No scab, 250 = Heavy scab

ECONOMIC ANALYSIS AND IMPACT:

No economic data is available due to no comparison to an untreated check.

CONCLUSION:

Enable fungicide at 8 oz/ac controlled pecan scab equally to Super Tin fungicide at 15 oz/ac when applied during a dryer than normal spring and summer. Both fungicides when mixed at half these rates and applied together provided an increased control of scab when compared to their individual treatments.

Comparison in another year against an untreated check with higher scab potential may increase the variance, showing the true value of these fungicides.

ACKNOWLEDGEMENTS:

Appreciation is expressed to contributing chemical companies, to Dr. Jerrel Johnson - Extension Pathologist and to Dr. and Mrs. John Starkey for helping with this demonstration.