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Control of pecan scab during the wet summer of 1965, in north Florda

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Title:
Control of pecan scab during the wet summer of 1965, in north Florda
Creator:
Large, John R.
Publisher:
Big Bend Horticultural Laboratory, University of Florida
Language:
English

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Source Institution:
University of Florida
Rights Management:
Copyright Board of Trustees of the University of Florida
Resource Identifier:
145505427 ( OCLC )

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BIG BEND HORTICULTURAL LABORATORY
Monticello, Florida I

March 23, 1966 _yt

Big Bend Hort. Lab. Miimeo Report BB3L66-3 I


CONTROL OF PECAN SCAB DURING THE WET .SUMMER OF 1965, IN NORTH FLORIDA

by JOHN R. LARGE1


An evaluation of fungicide formulations and experimental fungicides
for control of pecan scab was made in Jefferson County in the Big Bend Horticultural Laboratory orchard of Mahan, Schley and Moore varieties. In 1965 environmental conditions were highly favorable for disease development, the rainfall from January 1 to September 9 was 54405 inches, which was 10.57 inches above normal (43.48 ins.).

The orchard was sprayed 6 times, April 14,' May 14, June 25, July 9
and 26 and August 8th with a 35 gpm hydraulic sprayer at 450 psi. Insecticide was used in the June, July 9th and August applications.

Data were taken August 18 on green nuts of the three varieties. A
scab index figure (range 0-4), as used by Diener and Garrett (1), was calculated from 50 nuts per tree from each of seven trees of Mahan, four trees of Schley and three Moore trees. Data were recorded as: Clean - no scab on the shuck; Class 1 -trace to 10%; Class 2 - 11 to 25%, Class 3 26 to 50% and Class 4 -4 - 51 - 100%. The number of nuts in each class was multiplied by the class number. The resultant figures were summed-and divided by the number of nuts to give the scab index for each tree. The mean, of 7 replications for Mahan, 4 replications for Schley and 3 replications for Moore, was calculated for each treatment (Table 1). These data are also presented as the percentage of nuts with heavy, light or no (clean) visible scab infection. The figures under light infection represent means of the data from classes 1 and 2 and under heavy infection from classes
3 and 4. The nuts with heavy shuck infection are usually worthless and frequently drop before harvest. Nuts with light infection are usually poorly filled and of poorer quality than nuts free from scab.

Results of the 1965 experiments are shown in Table 1. Du-Ter as a wettable powder or as a liquid at high (1 1/2 lbs. or 19.6 oz.) or low rates of application (1/2 lb. or 6.2 ozs.) was the most effective of the fungicides tested for controlling scab. Dodine (Cyprex) at 1/2 lb./lO0 compared with Zineb + Oil, 2 lbs. + 1 qt./lOO, but these two chemicals were not as effective as bordeaux mixture. Nuts sprayed with Captan 2 lb./l00 or Captan, 4 applications followed by 2 applications of Dodine, 1 lb./l00 were only a little better than the nuts from unsprayed trees.


lAssociate Plant Pathologist, Big Bend Horticultural Laboratory,
Monticello, Florida.
150 cc








-2



Du-Ter at 1/2 lb./lO0 was more effective than Dodine at this concentration. Further investigations of Du-Ter is warranted to determine the minimum effective dosage and phytotoxicity on pecan varieties. Phytotoxicity again developed on Moore trees sprayed in April with Dodine (Cyprex) 1/2 lb./lO0. No phytotoxicity was noted on Moore trees sprayed with Du-Ter.

Grateful acknowledgement is made to the American Cyanamid and ThompsonHayward Companies for experimental materials.


LITERATURE CITED

1. Diener, U. L. and Frank E. Garrett. 1965 Control of Pecan scab in 1964 in Southwest Alabama. Proc. Southeastern Pecan Growers Assoc. 58: 73-74.








, Table 1. Control of Pecan


-3
Scab in North Florida in 1965.

MAHAN VARIETY


Fungicide Conc. of Rate/lO0 gal. Mean Scab Infection - % Lbs.
Act. Chem. Scab Clean Light Heavy nuts harIndex vested
per tree

Du-Ter 20 20% WP 1 1/2 lbs. 0.02 98.3 1.7 .0 46.7

Du-Ter 20% WP 1/2 lb. 0.06 95.5 4.1 0.4 24.9

Du-Ter Flow. 2#/gal. 19.2 ozs. 0.02 98.1 1.9 0 56.7

Du-Ter Flow. 2#/gal. 7.6 ozs. 0.07 92.8 6.3 0.9 37.6

Dodine (Cyprex) 65% WP 1/2 lb. 0.96 49.0 44.3 6.7 18.0

Bordeaux 4-1 then 6-2 0.55 62.7 36.4 0.9 24.4

Zineb + Oil 2 lbs. + 1 qt 1.10 48.5 41.6 9.9 38.9

Captan 50% WP 2 lbs.(4 appl.)
then Dodine 65% WP 1 lb.(2 apple ) 2.06 20.4 43.1 36.5 12.9

Captan 50% WP 2 lbs. 2.34 21.1 31.3 47.6 15.8

Not sprayed 3.46 0.2 9.6 90.2 1.8

MOORE VARIETY

Du-Ter 20% WP 1 1/2 lbs. 0.02 98.1 1.9 0 54.4

Du-Ter 20% WP 1/2 lb. 0.01 99.1 0.9 0 28.3

Du-Ter Flow. 2#/gal. 19.2 ozs. 0.01 99.4 0.6 0 6.2

Du-Ter Flow. 2#/gal. 7.6 ozs. 0.03 97.6 2.3 0.6 33.0

Dodine(Cyprex) 65% 1/2 lb. 0.63 56.6 42.2 1.2 2.7

Bordeaux 4-1 then 6-2 0.41 74.3 24.6 1.1 17.7

SCHLEY VARIETY

Du-Ter 20% WP 1 1/2 lbs. 0.07 94.8 3.3 1.9 13.8
Du-Ter 20% WP 1/2 lb. 0.06 94.3 5.1 0.6 7.1
Du-Ter Flow. 2#/gal. 19.2 ozs. 0.03 97.5 2.52.5 0 13.2
Du-Ter Flow. 2#/gal. 7.6 ozs. 0.02 97.6 2.4 0 10.3
Bordeaux 4-1 then 6-2 O.31 79.9 24.6 0.6 15.7
Not sprayed 3.25 0 11.3 88,7 0




Full Text

PAGE 1

/00 i 63t ?~v /j'/3 ,.k? 3 BIG BEND HORTICULTURAL LABORATORY Monticello, Florida Harch 23, 1966 Big Bend Hort. Lab. Mirneo Report BBL66-3 CONTROL OF PECAN SCAB DURING THE WET_SUHMER OF 1965, IN NORTH FLORIDA by JOHN R. LARGE 1 An evaluation of fungicide formulations and experimental fungicides , for control of pecan scab was made in Jefferson County in the Big Bend Hort' icultural Laboratory orchard of Mahan, Schley and Moore varieties. In 1965 environmental conditions were highly favorable for disease development, the rainfall from January l to September 9 was 54.05 inches, which was 10.57 inches above normal (43.48 ins.). The orchard was sprayed 6 times, April 14 May 14, June 25, July 9 and 26 and August 8th with a 35 gpm hydraulic sprayer at 450 psi. Insect icide was used in the June, July 9th and August applications. Data were taken August 18 on green nutt:i of the three varieties. A scab index figure (range 0-4), as used by Diener and Garrett (l), was cal culated from 50 nuts per tree from each of seven trees of Mahan, four trees of Schley and three Moore trees. Data were recorded as: Clean no scab on the shuck; Class l trace to 10%; Class 2 ll to 25%, Class 3 26 to 50% and Class 4 4 51 100%. The number of nuts in each class was multiplied by the class number. The resultant figures were summed and divided by the number of nuts to give the scab index for each tree. The mean, of 7 replications for Hahan, 4 replications for Schley and 3 repli cations for Moore, was calculated for each treatment ( Table l). These data are also presented as the percentage of nuts with heavy, light or no {clean) visible scab infection. The figures under light infection represent means of the data from classes land 2 and under heavy infection from classes 3 and 4. The nuts with heavy shuck infection are usually worthless and fre quently drop befoI"e harvest. Nuts with light infection are usually poorly filled and of poorer quality than nuts free from scab. Results of the 1965 experiments are shown in Table l. Du-Ter as a wet table powder OI" as a liquid at high {l l/2 lbs. or 19.6 oz.) or low rates of application (l/2 lb. or 6.2 ozs.) was the most effective of the fungicides tested for contI"olling scab. Dodine (Cyprex) at 1/2 lb./100 compared with Zineb + Oil, 2 lbs.+ l qt./100, but these two chemicals we~e not as effect ive as bordeaux mixture. Nuts sprayed with Captan 2 lb./100 OI" Captan, 4 applications followed by 2 applications of Dodine, 1 lb./100 were only a little better than the nuts from unsprayed trees. 1 Associate Plant Pathologist, Big Bend HorticultuI"al Labo!'atory, Honticello, Florida. 150 cc

PAGE 2

-2Du-Ter at l/2 lb./100 was more effective than Dodine at this concen tration. Further investigations of Du-Ter is warranted to determine the minimum effective dosage and phytotoxicity on pecan varieties. Phyto toxicity again developed on Hoare trees sprayed in April with Dodine ( Cyprex) l/2 lb. /100. No phytotoxicity was noted on Moore trees sprayed with Du-Ter. Grateful acknowledgement is made to the American Cyanamid and Thompson Hayward Companies for experimental materials. LITERATURE CITED l. Diener, U. L. and Frank E. Garrett. 1965 Control of Pecan scab in 1964 in Southwest Alabama. Proc. Southeastern Pecan Growers Assoc. 58: 73-74.

PAGE 3

_ . .......... _ , I -3Table l. Control of Pecan Scab in North Florida in 1965. MAHAN VARIETY Fungicide Cone. of Rate/100 gal. Mean Scab Infection % Lbs. Act. Chem. Scab Clean Light Heavy nuts harIndex vested per tree Du-Ter 20 20% WP 1 1/2 lbs. 0.02 98.3 1.7 .o 46.7 Du-Ter 20% 1 1 1P 1/2 lb. 0.06 95.5 4.1 0.4 24.9 Du-Ter Flow. 2#/gal. 19.2 ozs. 0.02 98.l 1.9 0 56.7 Du-Ter Flow. 2#/gal. 7.6 ozs. 0.07 92.8 6.3 0.9 37.6 Dodine ( Cyprex) 65% WP 1/2 lb. 0.96 49.0 44.3 6.7 18.0 Bordeaux 4-1 then 6-2 0.55 62.7 36.4 0.9 24.4 Zineb + Oil 2 lbs. + 1 qt 1.10 48.5 41.6 9.9 38.9 Captan 50% \ 1P 2 lbs.(4 appl.) then Dodine 65% WP l lb. (2 appl.) 2.06 20.4 43.l 36.5 12.9 Captan 50 9 0 WP 2 lbs. 2.34 21.1 31.3 47.6 15.8 Not sprayed 3.46 0.2 9.6 90.2 1.8 MOORE VARIETY Du-Ter 20% WP l 1/2 lbs. 0.02 98.l 1.9 0 54.4 Du-Ter 20% WP 1/2 lb. 0.01 99.l 0.9 0 28.3 Du-Ter Flow. 2#/gal. 19.2 ozs. 0.01 99.4 0.6 0 6.2 Du-Ter Flow. 2#/gal. 7.6 ozs. 0.03 97.6 2.3 0.6 33.0 Dodine ( Cyprex) 65 9 0 1/2 lb. 0.63 56.6 42.2 1.2 2.7 Bordeaux 4-1 then 6-2 0.41 74.3 24.6 l.l 17.7 SCHLEY VARIETY Du-Ter 20% HP 11/2 lbs. 0.07 94.8 3.3 1.9 13.8 Du-Ter 2096 WP 1/2 lb. 0.06 94.3 5.1 0.6 7.1 Du-Ter> Flow. 2#/gal. 19.2 ozs. 0.03 97.5 2.52.5 0 13.2 Du-Ter Flow. 2#/gal. 7.6 ozs. 0.02 97.6 2.4 0 10.3 Bordeaux 4-1 then 6-2 0.31 79.9 24.6 0.6 15.7 Not sprayed 3.25 0 11.3 88.7 0


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