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Copyright 2005, Board of Trustees, University
of Florida







Herbicides and Leatherleaf Fern'2

R. H. Stamps and D. D. Mathur
IFAS, University of Florida
Agricultural Research Center-Apopka
ARC-A Research Report RH-81-19


I.F.A.S- Univ. of Fiorid


In spite of efforts to prevent contamination of ferneries and control
weeds mechanically, weeds continue to be a perennial problem in leatherleaf
fern (Rumohra adiantiformis [G. Forst.] Ching) beds. Crop competition,
dense and vigorously growing leatherleaf fern, is one of the cheapest and
most effective methods of weed control available to fern growers. Herbicides
could also be useful weed management tools, especially when crop competition
is low; however, no herbicides are presently registered for use on leatherleaf
fern. Crop competition is particularly low when beds are newly planted and
after heavy harvesting of fronds.
This report presents a summary of two years of screenings of herbicides
for potential use on leatherleaf fern. Table 1 lists names and manufacturers
of herbicides that were evaluated and found to be nonphytotoxic.


Table 1. Names and manufacturers of herbicides evaluated
to be nonphytotoxic.z


and found


Common name
Alachlor
Dipropetryn
Metolachlor
Napropamide
Oryzalin
Oxadiazon


Prodiamine
Propachlor
Simazine
Thiobencarb


Trade name
Lasso II
Sancap
Dual
Devrinol
Surflan
Progrow Ornamental
Herbicide I and
Ronstar
Rydex
Ramrod
Princep
Bolero


Manufacturer
Monsanto
Ciba-Geigy
Ciba-Geigy
Stauffer
Elanco

Scotts
Rhone-Poulenc
U. S. Borax
Monsanto
Ciba-Geigy
Chevron


ZHerbicides with phytotoxicity ratings less than 1 on a scale from 0
(no damage) 10 (death). Check tables 3-6 for rates, formulations
and combinations.

The authors gratefully acknowledge Shuman Farms for their cooperation and
assistance in these studies.
No herbicides are registered for use on leatherleaf fern. Mention of a
herbicide does not constitute a recommendation by the authors. Mention
of a commercial or proprietary product does not constitute an endorsement
by the authors.


~ -- ----- --


~------






Materials and Methods


Herbicide screenings were conducted in a commercial fernery near DeLeon
Springs, Florida. The soil type was Apopka fine sand containing 2.1% organic
matter and soil pH was maintained between 5.8 and 6.8. The test area was
covered with 73% shade polypropylene fabric. Plots were 8' x 12' and contained
approximately 72 plants each. The fern were planted in April 1979. Fern yield
data were determined from harvests on March 12, 1980, August 14, 1980, October
22, 1980, April 15, 1981, and September 10, 1981. All plots, including
untreated controls, were hand weeded immediately prior to herbicide application.
Granular herbicide formulations were hand broadcast. Wettable powders and
emulsifiable concentrates were applied in water at 200 gal/acre through a wide
angle flat spray nozzle at 20 psi pressure. Herbicides were reapplied 4, 8,
12, and 18 months and weed control and phytotoxicity ratings were made 1, 2,
3, 4, 8, 12, 15, 18, and 24 months after initial application for screening
I, II, and III. Screening IV treatments were reapplied 5 and 11 months and
weed control and phytotoxicity ratings were made 5, 8, 11, and 17 months after
initial applications. Screening IV yield data was not taken March 12, 1980.
Weed control and phytotoxicity were rated visually. Weed control was rated
from 0 100% as compared to controls and phytotoxicity was rated from 0
(no damage) 10 (death). Tables 3 6 list herbicide treatments that averaged
less than 1 on the phytotoxicity ratings. Reported weed control ratings are
based on the following scale: Excellent = 90-100%, good = 80-90%, fair = 60-80%,
and poor = less than 60%. Aisles between the raised fern beds were kept weed-
free by applying contact and residual herbicides as needed.
Results and Discussion
Predominant weed species present during these studies are listed in Table 2.

Table 2. Predominant weed species present during herbicide screenings
near DeLeon Springs, Florida.

Common name Botanical name
American burnweed Erechtites hieracifolia (L.) Raf.
Asiatic hawksbeard Youngia japonica (L.) D.C.
Burning nettle Urtica urens L.
Chickweed Stellaria media (L.) Cyr.
Common yellow woodsorrel Oxalis strict L.
Dayflower Commelina communis L.
Heartleaf drymary Drymaria cordata (L.) Willd.
Large crabgrass Digitaria sanguinalis (L.) Scop.
Phyllanthus Phyllanthus tenellus Roxb.
Yellow nutsedge Cyperus esculentus L.


-2-







Screening I. Most of the oxadiazon containing treatments gave acceptable
weed control during the first year while the fern beds were becoming established
(Table 3). During the second year, when the fern beds were well established,
all treatments except simazine at 1 lb ai/A gave satisfactory weed control.
None of the herbicide treatments decreased frond production compared to the
control. 'None of the herbicide treatments decreased fresh weight yields
significantly compared to the control with the possible exception of simazine
at 1 lb ai/A. Yield reductions from simazine applications have been found
in previous studies (1,2,3,4). It has been shown (4) that frond weight and
frond length are positively correlated. The weight difference between the
heaviest mean frond weight (0.58 oz) and the lightest mean frond weight (0.48 oz)
amounts to about a 1 inch difference in frond lengths which is not significant
commercially.
Screening II. The oxadiazon + thiobencarb and the oxadiazon + metolachlor
treatments gave acceptable weed control the first year (Table 4). All herbicide
treatments gave satisfactory weed control once the fern was well established
(year 2). The yield from the herbicide treated plots was generally greater
than from the control plot and the herbicides had little effect on the mean
frond weights.
Screening III. None of the herbicide treatments gave good weed control
the first year, but the second year they all gave very satisfactory control
(Table 5). Yields were higher for both parameters, number and weight, in the
herbicide treated plots than in the control plots. Frond weights were not
greatly affected by any of the treatments.
Screening IV. Even though the fern was well established and dense when
these screenings were started the dipropetryn and napropamide treatments
gave unacceptable weed control (Table 6). Yields and mean frond weights from
the herbicide treated plots were as high or higher than from the control plot.
Summary
1. Many of the treatments were effective in controlling weeds during the
leatherleaf fern bed establishment period (the first year after planting).
2. Most of the herbicide treatments were effective in controlling weeds once
the beds were well established.
3. None of the herbicides, with the possible exception of simazine applied
alone, reduced yields compared to the controls. In fact, herbicide
treated plots generally yielded higher than the controls.
4. None of the treatments seemed to significantly affect mean frond weights.









Literature Cited

1. Poole, R. T. 1979. Influence of preemergence herbicides on weed

control and yield of leatherleaf fern, Rumohra adiantiformis (G. Forst.)

Ching. Proc. Trop. Reg., Amer. Soc. Hort. Sci. 23: (In Press),

2. Poole, R. T., W. T. Scudder, and L. L. Loadholtz. 1978. Weeds in

leatherleaf fern. Univ. of Fla., Agr. Res. Ctr., Apopka, Res. Rep.

RH-78-5.

3. Poole, R. T. and W. E. Waters. 1974. Influence of several herbicides

on yield of leatherleaf fern. Proc. Trop. Reg., Amer. Soc. Hort. Sci.

18:279-282.

4. Stamps, R. T. and D. D. Mathur. 1982. Herbicides for weed control in

leatherleaf fern. HortScience 17: (In Press).







Table 3. Screening I. Weed control, yield, and average frond weights of leatherleaf fern.


Herbicide Rate in Weed control Yield (% of control) Mean frond
(formulation) Ib ai/A Yr 1 Yr 2 # bunches wt in Ibs weight in ounces


None
Oxadiazon (4G)
Oxadiazon (4G) +
simazine (4G)
Oxadiazon (4G) +
thiobencarb (8E)
Metolachlor (15G)
simazine (4G)
Simazine (4G)

Oxadiazon (4G) +
alachlor (15G)


Oxadiazon
simazine
alachlor


(4G) +
(4G) +
(15G)


Oxadiazon (4G) +
metolachlor (15G)


1+
1.5

1.5+


good

good

fair

fair
poor


Initiated 6/11/79
73(100)
excellent 85(116)


excellent

excellent

excellent
poor


71( 97)

82(112)

85(116)
73(100)


Initiated 10/10/79


Excellent


good


82(112)


Initiated 2/8/80


excellent

excellent


82(112)

74(101)


ZPounds active ingredient per acre.


64.6(100)
68.9(107)

64.8(100)

67.2(104)

73.4(114)
55.5( 86)


61.6( 95)


0.57
0.52

0.58

0.53

0.55
0.49


0.48


62.9( 97)

65.4(101)


0.49

0.57




ble 4. Screening II. Weed control, yield, and Orage frond weight of leatherleaf fern.

Herbicide Rate in Weed control Yield (% in control) Mean frond
(formulation) lb ai/A Yr 1 Yr 2 # bunches wt in Ibs weight in oz
Initiated 7/13/77

None 84(100) 65.2(100 0.50
Oxadiazon (4G) + 1 +
thiobencarb (8E) 4 good excellent 109(130) 85.1(130) 0.50
Oxadiazon (4G) + 1 +
propachlor (65WP) 4 fair excellent 104(124) 90.4(139) 0.56
Oxadiazon (4G) + 1 +
metolachlor (15G) 2 good excellent 113(135) 92.3(141) 0.52
Propachlor (65WP) 6 poor excellent 89.8(107) 70.8(109) 0.50
Initiated 11/5/79

Alachlor (15G) + 1.5 +
simazine (4G) 1.5 poor good 90 (107) 64.9(100) 0.46

ZPounds active ingredients per acre.


-0





Table 5. Screening III. Weed control, yield, and average frond weight of leatherleaf fern.
Herbicide Rate in Weed control Yield (% in control) Mean frond
(formulation) Ib ai/Az Yr 1 Yr 2 # bunches wt in Ibs weight in oz
Initiated 8/3/79
Controls (avg of 2) 69.5(100 55.0(100) 0.51
Oxadiazon (4G) + 1+
thiobencarb (8E) 2 poor excellent 84 (121) 73.2(133) 0.56
Oxadiazon (4G) + 2+
oryzalin (75WP) 1.5 fair excellent 79 (114) 74.4(135) 0.60
Oxadiazon (4G) + 2+
alachlor (15G) 1.5 poor good 102(147) 85.2(155) 0.53
Oxadiazon(4G) 2 poor excellent 88 (127) 75.4(137) 0.55

Initiated 11/15/79
Simazine (80W) + 1.5 +
oryzalin (75WP) 2 excellent 78 (112) 71.3(130) 0.59

ZPounds active ingredients per acre.







Table 6. Screening IV. Weed control, yield, and average frond weight of leatherleaf fern.

Herbicide Rate in Weed control Yield (% in control) Mean frond
(formulation) lb ai/A # bunches wt in Ibs weight in oz
Initiated 1/16/80
Control 80(100) 61.2(100) 0.49
Simazine (4G) + 1.5+
napropamide (10G) 4 excellent 93(116) 84.5(138) 0.58
Oxadiazon (46) + 2+
napropamide (10G) 4 excellent 89(111) 74.2(121) 0.53
Dipropetryn 80W) 1 poor 82(102) 61.9(101) 0.48
Napropamide (10G) 2 poor 86(108 76.8(125 0.57
Napropamide (10G) 4 poor 90(112) 69.2(113) 0.49
Initiated 6/11/80
Prodiamine (50W) 2 good 113(141) 102.4(167) 0.58

ZPounds active ingredients per acre.