Richard C. Funt, Thomas E. Wall, and B. Dale Stokes
Controlling weeds during the first (establishment) year in raspberries is extremely important. Young, newly transplanted raspberry plants grow most rapidly in a weed-free environment. Herbicides reduce weed pressure in raspberry plantings and labor costs. When herbicides are properly selected and applied at the optimal rates, plant growth can be enhanced. However, raspberry transplants can be damaged if they are subjected to improper herbicide selection and application rates. Mechanical cultivation, which may be done several times over the season, can also cause reduced plant growth and death.
In previous studies, pre-emergent herbicides applied over the top of newly transplanted raspberries, bare root and dormant, were found to control many annual weeds and allow good plant growth (1). New technology allows tissue-cultured raspberry plants to be shipped to growers as dormant or growing plants, either as plugs or as nursery-matured plants. Tissue cultured plants are generally more vigorous than bare-rooted plants, and as plug plants, are easier to transplant mechanically. Thus, this study was designed to test currently labeled and newly released herbicides on plug or nursery-matured plants to achieve weed control over a long period of time.
The objectives of this study using greenhouse and field trials were to determine:
Experiment 1 – Indoor Study
Dormant tissue-cultured 'Jewel' black raspberry (Rubus occidentalis) plugs were planted into 4-inch (10 cm) peat pots containing a soilless mixture (Premier Pro-mix) of peat moss and perlite on Dec. 1, 1995. At planting, each plant received 100 ml of 100 ppm 20-20-20 (Peters) solution. Group A treatments were applied immediately after planting (Table 1). The same treatments were applied 10 days later (Group B) as a delayed application to test the effects of herbicides on newly emerged leaves. Herbicides were applied using a pressurized system at 40 psi with a set of two nozzles to equal a 20 gallon/acre rate. The following herbicides were used in this study: Surflan (Oryzalin 4AS) and Poast (Sethorydim 1.5EC), pre-emergent and post-emergent systemic grass herbicides respectively, which have been recommended for growers for several years (4); Gallery (Isoxaben 75 DF) and Prism (Clethomin 2EC), pre-emergent and post-emergent grass herbicides respectively, which have been recently released on the market (4).
Table 1. Leaf Appearance, Number of Shoots, Shoot Dimensions, and Shoot and Root Weights of Greenhouse-Grown 'Jewel' Black Raspberries Treated with Various Herbicide Regimes, 1996. |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant Appearance | Shoot Dimen. (mm) |
Shoot Wt. (g) |
Root Wt. (g) |
Total Wt. (g) |
||||||||
| Herbicide Treatments and Application Rates (per acre) | Good | Damaged | Final Leafz | No. of Shoots |
Caliper | Length | Fresh | Dry | Fresh | Dry | Fresh | Dry |
| Group Ay | ||||||||||||
|
1.17 1.33 0.66 0.83 0.20 1.00 0.50 |
0.17 0.00 0.50 0.33 0.00 0.17 0.33 |
2.5 2.7 3.7 2.7 2.2 1.8 2.0 |
2.6 0.8 0.2 0.5 1.2 1.4 1.0 |
2.3 4.8 2.8 2.2 2.2 2.8 2.4 |
11.2 17.5 7.0 4.5 9.8 31.2 11.5 |
3.0 2.9 0.6 0.5 2.6 5.2 2.7 |
0.4 1.2 0.1 0.1 0.4 0.8 0.2 |
19.0 19.7 8.9 16.5 12.8 21.8 17.7 |
3.4 3.4 1.7 2.9 2.4 3.6 3.1 |
22.0 22.6 9.5 17.0 15.5 27.0 20.4 |
3.8 6.1 4.4 2.9 3.3 4.9 4.1 |
| Significance (Spray vs. Control)x | NSw | NS | NS | ** | NS | NS | NS | NS | NS | NS | NS | NS |
| Group Bv | ||||||||||||
|
1.17 1.33 1.33 1.17 0.16 0.50 0.67 |
0.17 |
2.5 2.5 2.7 2.2 1.8 2.0 2.3 |
2.6 0.8 1.0 1.0 1.0 1.1 0.6 |
2.3 2.4 3.1 2.8 1.9 2.4 2.4 |
11.2 14.0 7.6 17.0 10.0 16.0 15.2 |
3.0 1.4 1.5 1.5 0.9 3.0 2.4 |
0.4 0.6 0.4 1.4 0.2 0.8 0.6 |
19.0 16.0 21.1 22.2 17.1 22.2 20.4 |
3.4 3.5 4.0 3.0 3.2 4.2 3.8 |
22.0 17.4 22.6 23.7 18.0 25.2 22.8 |
3.8 4.0 4.9 5.6 3.4 5.5 5.8 |
| Significance (Spray vs. Control) | ** | NS | NS | ** | NS | NS | NS | NS | NS | NS | NS | NS |
| Significance (All Trials) | ||||||||||||
|
** NS NS NS NS NS |
NS ** NS NS NS NS |
NS NS ** NS NS NS |
NS NS NS NS NS NS |
** NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
NS NS NS NS NS NS |
| z Average number of good and damaged leaves
after first spray. Final leaf color evaluated on Feb. 26, 1996. Rating scale:
1 = good/green; 2 = light green; 3 = brown; 5 = dead. y Group A plants treated on Dec. 1, immediately after transplanting. x Orthogonal contrasts from analysis of variance. w NS, *, ** = nonsignificant or significant at P = 0.05 and 0.01 levels, respectively. v Group B plants treated on Dec. 11, 10 days after transplanting. |
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Plants were grown indoors (near Wilmington, Ohio) under fluorescent lighting with daily temperatures ranging from 60 to 80°F (16 to 27°C). Plants were evaluated for leaf damage on Dec. 11, 1995, for Group A; Dec. 21, 1995, for Group B; and Feb. 26, 1996, for both groups, by counting leaves that had light green color to dark dry brown condition with 1 = dark green, 2 = light green, 3 = brown edges, 4 = brown all over, 5 = dead. Shoots greater than 1 cm were removed, measured for length and caliper, and weighed to obtain both fresh and dry weights. Roots, which included some growing medium which would not separate from the roots after washing, were weighed both fresh and dry. Dry weight was obtained by placing plant parts in a drying oven at 125°F (51°C) for 48 hours.
Experiment 2 – Field Study
Dormant tissue-cultured 'Jewel' black raspberry plugs and nursery-matured plants were transplanted onto a raised bed on May 20, 1996, in a field near Wilmington, Ohio. Herbicide Treatments 2, 3, 4, 5, 6, 9, and 10 were applied two days later after 0.2 inches (5 mm) of rainfall (Table 2). Straw mulch was applied to a depth of 2.5 inches (6.3 cm) to Treatments 2 and 3. Herbicides were banded over the rows with a pressurized CO2 system at 40 psi and a set of 2 nozzles (8002) to equal a 20 gallon/acre rate. The chemicals used in the treatments were the same formulations as in Experiment 1.
Table 2. Time of Application for Various Herbicide Regimes Applied to Field-Grown 'Jewel' Black Raspberries, 1996. |
|||
|---|---|---|---|
| Time of Application | |||
| Treatment and Application (per acre) | May 22 | July 8 | October 2 |
| Cultivated Control |
X
|
X
|
X
|
| Surflan (4 qt)) + Straw Mulch |
X
|
--
|
X
|
| Gallery (1.3 lb) + Straw Mulch |
X
|
--
|
X
|
| Surflan (2 qt) + Straw Mulch |
X
|
--
|
X
|
| Surflan (2 qt) |
X
|
--
|
X
|
| Prism (16 oz) + Surflan (2 qt) + Gallery (1 lb) |
X
|
X
|
--
|
| Prism (16 oz) + Dash (16 oz) + Surflan (4 qt) + Gallery (1.3 lb) |
--
|
X
|
--
|
| Prism (16 oz) + Dash (16 oz) + Surflan (4 qt) + Gallery (1.3 lb) + Stinger (6 oz) |
--
|
X
|
--
|
| Surflan (4 qt) + Stinger (6 oz) |
X
|
--
|
X
|
| Gallery (1.3 lb) |
X
|
--
|
X
|
| z Karmex (2 lb) was used with Surflan
(4 qt). No straw was applied in October. y Surflan AS (4 qt) was used with Gallery (1.3 lb). |
|||
On July 8, 1996, the control group was hand weeded, and Treatments 6, 7, and 8 were applied (Table 2). Where straw had been removed by wind, straw mulch was replaced. Plots were visually rated on July 8 for types of weeds, number of certain weeds, percent of soil without weed cover, and number of dead plants. Calcium nitrate [Ca(NO3)2] was applied at 6 lbs per 100 ft of row (2.7 kg per 30m). Stinger (Clopyralid 3EC), a selective post-emergent broadleaf herbicide, was applied to emerged weeds in Treatment 8.
Fall herbicide applications were applied on Oct. 2, 1996, to Treatments 2, 3, 4, 5, 9, and 10. Kamex (Diuron 80WP) was mixed with Surflan in Treatments 2 and 9. Surflan was mixed with Gallery in Treatments 3 and 10.
Statistical Design and Analysis
In Experiment 1, there were two groups (Groups A and B) of application times (10 days apart). These were arranged in a completely randomized design with border plants. Within each group there were seven treatments including a control. Within each treatment, there were six single-plant replicates. A general linear model analysis program was used to contrast differences among treatments within a group, and between treatments in groups (2A vs. 2B, etc.).
In Experiment 2, herbicide treatments were arranged in a split-plot design with plant type as subtreatments. There were four plug plants or nursery-mature plants in each sub plot. An analysis of variance was done for the dependent variable (2). Treatments were separated using least significant difference tests.
Experiment 1 – Indoor Study
Where herbicides were applied on the day of planting (Group A), there were no significant differences between treatments and the control in all variables except for the number of shoots (Table 1). The control had more than twice the number of shoots than all treatments except for Treatment 6. There was a significant difference between herbicide treatments applied at the second spray (Group B) and the control for plant appearance. Among the herbicide treatments, Treatments 6 and 7 had a better appearance than other herbicide treatments. Further, there was a significantly better appearance in Treatment 2A than 2B. Also 2A had a significantly greater shoot caliper than Treatment 2B. In the final leaf appearance, Treatment 4A had a significantly better appearance than 4B.
Experiment 2 – Field Study
There were significant differences among treatments for percent weed-free plots in 1996 (Table 3). Treatments 2, 3, 4, 5, 6, 9, and 10 had a fewer number of weeds as compared to the control and Treatments 7 and 8. There were no differences among treatments for Canadian thistle and those for the control group. The control and Treatments 7 and 8 had the highest number of weeds. The types of grasses and broadleaf weeds identified among all plots are listed in Table 4. Treatment 4 had the lowest number of plants as compared to the control and Treatments 2 and 7. There was a significant interaction in the number of tissue-cultured plants (low survival) as compared to the nursery-matured plants for all treatments.
Table 3. Weed Ratings, Number of Weeds, and Crop Plant Survival in Plots of 'Jewel' Black Raspberries Treated with Various Herbicide Regimes, 1996. |
||||
|---|---|---|---|---|
| Treatment | Weed Ratingz | Weeds (No.) | Thistles (No.) | Surviving Raspberries (No.) |
| 1. |
2.3 by
|
26.1 a
|
2.1
|
3.4 a
|
| 2. |
10.0 a
|
5.6 a
|
1.1
|
3.3 ab
|
| 3. |
9.5 a
|
13.2 a
|
4.2
|
2.8 abcd
|
| 4. |
9.7 a
|
9.8 b
|
6.3
|
1.8 d
|
| 5. |
9.8 a
|
7.8 b
|
1.7
|
2.3 bcd
|
| 6. |
9.9 a
|
9.5 b
|
3.1
|
2.0 cd
|
| 7.x |
1.1 b
|
30.0 a
|
4.1
|
2.8 abc
|
| 8.x |
2.0 b
|
27.0 a
|
1.1
|
2.5 bcd
|
| 9. |
9.7 a
|
10.0 b
|
2.3
|
2.6 abcd
|
| 10. |
9.6 a
|
12.5 b
|
5.0
|
2.6 abcd
|
| Significancew | ||||
| Treatment |
*v
|
NS
|
NS
|
*
|
| Plant Typeu |
NS
|
*
|
NS
|
NS
|
| Treatment X Plant Type |
NS
|
NS
|
NS
|
NS
|
| z Visual rating performed on June
26. Rating scale: 1 = complete weed coverage to 10 = very few weeds actively
growing. y Means with the same letter are not significantly different by LSD (P ≥ 0.05). x Treatments 7 and 8 were designed to determine the effect of delayed residual plus a selective systemic herbicide. Therefore, they were not applied until after this evaluation was performed. w Significance of F-values from analysis of variance. v NS, *, ** = nonsignificant or significant at P = 0.05 and 0.01 levels, respectively. u Plant type refers to original nursey stock used to established the planting (i.e., tissue-cultured plug plants vs. nursery-matured plants). |
||||
Table 4. List of Weeds Observed Among Plots. |
||
|---|---|---|
| Types | Common Name | Scientific Nomenclature |
| Grass | Crabgrass | Digitaria sanguinalis |
| Barnyardgrass | Eclinochloa cues-galli | |
| Goosegrass | Eleusin indica | |
| Giant Foxtail | Setaria faberi | |
| Fall Panicum | Panicum dichotomiflorum | |
| Broadleaf | Pennsylvania Smartweed | Polygonum pennsylvanicum |
| Dandelion | Taraxacum officinale | |
| Canadian Thistle | Cirsium arvense | |
| Northern Yellow Nutsedge | Cypernus esculentus | |
| Lambsquarter | Chenopodium albuina | |
| Red Root Pigweed | Amaranthus retroflexus | |
| Smooth Groundcherry | Pysalis subglabrata | |
| Black Nightshade | Solanum ptycanthum | |
In 1997, Treatment 3 had significantly fewer weeds than the control in the percent of ground covered with weeds (Table 5). All other treatments were not significantly different than the control. However, Treatment 3 was significantly greater than the control and other treatments (except for Treatment 4) for the percent of grasses in the plot. Broadleaf weeds ranged from 62 to more than 98 percent of weeds found in this experiment. Treatment 8 had the lowest number of surviving plants and number of shoots. Treatments 3, 4, and 10 had a significantly lower number of dandelion weeds as compared to the control and Treatments 2 and 7. There were no differences among treatments for Canadian thistle. Treatment 3 had the highest vigor rating and Treatment 8 had the lowest rating (Table 6). Treatment 2 was significantly greater in fresh and dry weight than any other treatment including the control. Treatments 3, 5, and 6 were significantly greater in fresh weight than the control and Treatments 7 and 8. There were no phytotoxic symptoms observed among the treatments.
Table 5. Weed Infestation Severity in Field-Grown 'Jewel' Black Raspberries Treated with Various Post-Plant and Fall-Applied Herbicide Regimes, 1997. |
|||||
|---|---|---|---|---|---|
| Proportion of Weed Types Present (%) | Weed Population (No.) | ||||
| Treatment | Weed Cover in Plots (%) | Grass | Broadleaf | Dandelion | Thistle |
| 1. | 47.1 az | 0.7 b | 99.3 a | 5.3 ab | 0.4 |
| 2. | 29.3 ab | 8.0 b | 92.0 ab | 7.4 ab | 2.4 |
| 3. | 7.0 b | 36.6 a | 62.4 b | 0.6 c | 0.0 |
| 4. | 25.0 ab | 15.0 ab | 85.7 ab | 1.0 c | 0.1 |
| 5. | 36.7 a | 5.8 b | 94.0 ab | 3.3 bc | 1.0 |
| 6. | 46.5 a | 4.4 b | 95.6 a | 2.9 bc | 0.0 |
| 7. | 52.9 a | 1.0 b | 98.7 ab | 10.1 a | 5.0 |
| 8. | 33.2 ab | 0.2 b | 99.4 ab | 2.4 bc | 0.2 |
| 9. | 38.6 a | 6.7 b | 91.6 ab | 4.7 bc | 0.0 |
| 10. | 25.8 ab | 1.4 b | 98.6 ab | 1.0 c | 8.4 |
| z Means with the same letter are not significantly different by LSD (P ≥ 0.05). | |||||
Table 6. Growth of Field-Grown 'Jewel' Black Raspberries Treated with Various Post-Plant and Fall-Applied Herbicide Regimes, 1997. |
|||||
|---|---|---|---|---|---|
| Plant Wt. (g)y | Plant Population (No.) | ||||
| Treatment | Vigor Ratingz | Fresh | Dry | Plants | Shoots |
| 1. | 4.3 abx | 57.6 ef | 33.4 def | 3.0 a | 14.7 ab |
| 2. | 4.6 ab | 335.8 a | 171.6 a | 3.0 a | 16.4 a |
| 3. | 6.5 a | 182.7 b | 91.0 b | 2.5 ab | 11.7 ab |
| 4. | 4.6 ab | 80.4 de | 43.7 cdef | 1.7 bc | 4.6 bc |
| 5. | 6.5 a | 138.0 bcd | 74.0 bcd | 2.5 ab | 11.7 ab |
| 6. | 3.8 bc | 158.2 bc | 81.6 bc | 2.4 ab | 12.8 ab |
| 7. | 4.1 b | 35.2 ef | 18.4 ef | 2.7 ab | 9.0 bc |
| 8. | 1.6 c | 1.8 f | 1.3 f | 1.1 c | 3.5 c |
| 9. | 3.8 b | 91.1 cde | 50.7 bcde | 2.4 ab | 9.7 abc |
| 10. | 3.9 b | 110.4 bcde | 61.2 bcde | 2.1 ab | 14.3 ab |
| z Vigor was determined visually
from a combination of plant height, thickness of cane, and leaf color. Rating
scale: 1 = lowest vigor; 10 = highest vigor. y Fresh and dry weights measured on dormant canes from 1996 growing season which were harvested in March 1997. Canes were dried at 135°F for five.days x Means with the same letter are not significantly different by LSD (P ≥ 0.05). |
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Indoors, the application of herbicides to dormant plug plants at planting appeared not to be phytotoxic. However, the control plants had more shoots than any of the herbicide treatments. When herbicides were applied 10 days after planting, Surflan-treated plants had a lower overall leaf appearance than those without Surflan. Perhaps these plants received low amounts of light and the leaves developed thinner cuticle (wax cover). There were no differences in either plant or root growth measurements between the control and herbicide treatments at the end of the study.
In the field, the Surflan and Gallery treatments applied within several days after transplanting to weed-free soil provided good weed control and the best plant growth. The high rates of Surflan and Gallery (Treatments 2 and 3) plus straw mulch generally had the highest plant vigor and new shoots among the herbicides tested. High rates of Gallery, 1.3 lbs /acre alone (Treatments 3 and 10), had lower numbers of dandelion. Dow Elanco, the producer of Gallery, indicates that Gallery is a pre-emergent herbicide for broadleaf weeds such as dandelion, clover, and chickweed and may control them for up to eight months. Where Gallery was applied at 1.3 lbs/acre several weeks after planting (Treatment 7), dandelions were not controlled. Post-emergent control of dandelion and thistle in Treatments 8 and 9 could have resulted from Stinger. Stinger plus Gallery, applied in July, was not different from Gallery alone when applied in late May. The application of Stinger did not improve thistle control. However, raspberries showed leaf cupping and stress several weeks after it was applied. Applying Prism several weeks after transplanting provides similar grass control as the weeded control.
When herbicide treatments were delayed for several weeks after transplanting in July, broadleaf weed populations were significantly higher in the first year, and raspberry plant growth in the second year was reduced. Fresh and dry weights of the plants treated with Stinger plus other herbicides were less than that of the weeded control. There were no phytotoxic symptoms on any treatment regardless of whether they were applied alone or in combination with each other.
Erf and Funt (1) reported the greatest weed control using high rates of Surflan with no apparent phytotoxic symptoms on standard tip-layered transplants in Ohio. When Princep (Simazine 80%) was used on newly set transplants of 'Brandywine' purple raspberry, phytotoxic symptoms were observed. Trinka and Pritts (3) tested Princep and Devrinol (Napropamide 50DF) separately and found Princep to have similar symptoms on "Heritage" raspberry as to those observed in Ohio.
In New York, Trinka and Pritts (3) used straw mulch, which enhanced plant growth on newly transplanted tissue-cultured heritage plants. In this study, when straw mulch was combined with high rates of either Surflan or Gallery alone, plant growth was enhanced and was the highest as compared to other treatments including the control. Straw mulch improved weed control and soil moisture even when rainfall was adequate and trickle irrigation was used.
Uncontrolled weed growth during plant establishment inhibits raspberry plant growth and production into the second and third growing seasons. Using a combination of a pre-emergent herbicide and straw mulch immediately after transplanting can reduce weed populations and enhance raspberry plant growth even with adequate rainfall.
Surflan alone applied immediately after planting to a weed-free area at 4 qts per acre, or Gallery alone at 1.3 lbs per acre, provided good weed control and, when combined with straw mulch, enhanced plant growth. In most cases, weed control was not increased when Surflan and Gallery were combined. Nevertheless, dandelion control was improved with Gallery even though Gallery did not provide good grass control. Applying Surflan or Gallery immediately after planting, to a weed-free surface, provides better weed control than applying several weeks after planting since they are both pre-emergent herbicides. Surflan alone at 2 quarts/acre at planting, and again in early October, provides good growth and plant vigor. Prism can be mixed with Surflan plus Gallery to enhance post-emergent grass control without phytotoxicity in the raspberry plant. Nursery-mature plants had a higher survival rate than plug plants. Neither type of plant was affected adversely by any herbicide.
Grateful appreciation is extended to the Ohio Fruit Growers Society, the Ohio State University Vegetable Team, and Valent Corporation for their financial support.