Easter lilies have been the most important crop in Humboldt and Del Norte counties of California (CA) and Curry County, Oregon (OR), USA since the early 1940s. This is the only area of the United States where Easter lily (
Essential oils (EOs) are complex mixtures of volatiles, mainly products of plant secondary metabolism. Common components include terpenes, mono- and sesquiterpenes, and phenolic compounds, such as phenylpropanoids. They are generally biodegradable, have low toxicity to mammals and do not accumulate in the environment (Figueiredo et al., 2008). Chitwood (2002) reviewed the research on the effect of EOs on plant parasitic nematodes. Effects reported in several papers utilizing a variety of EOs against root-knot nematode included mortality of juveniles; and inhibition of mobility, hatching, infection and gall formation.
Since the review by Chitwood (2002), additional research with EOs on plant parasitic nematodes has shown promising results. A number of papers have looked at EOs fractionated into their component parts. For example, Faria et al. (2013) working with fractions of EOs for management of the pinewood nematode,
Seasonal weather patterns greatly affect quality and size of bulbs even in the absence of nematode pests. For example, “Nellie White” bulbs produced one year can be more than double the size of those produced in another year (Roberts et al., 1985). Trials conducted at the Easter Lily Research Foundation (ELRF) Station rotate through four different fields. Therefore, in addition to weather variation, there is additional variability in soil characteristics and nematode population levels. Even the standard products utilized by growers have shown year-to-year variability working better in some years than others (L.J. Riddle, pers. comm.).
The primary objective of this study was to evaluate preplant treatments of Easter lily bulblets with commercially prepared formulations of four EO products to an untreated control (UC), and a chemical standard to determine their value in the management of lesion nematode, and the subsequent growth of bulbs. A secondary objective was to evaluate the effectiveness of the organophospate nematicides ethoprop and fosthiazate used either alone, or in combination with a reduced rate of phorate.
During two years of field trials conducted at the ELRF Research Station in Brookings, OR, commercially prepared formulations of four EO products were compared to an UC and a standard chemical treatment for management of
Description of treatments and abbreviations used in text and tables.
Bulblet dip (d), | ap, pp | ||
---|---|---|---|
Preplant | At planting (ap), or | Rate | |
Abbreviationa | Treatment (FU) | Post plant (pp) | kg a.i./hab |
FUPH9 | Yes | Phorate (ap) | 9 |
FUET13 | Yes | Ethoprop (ap) | 13.4 |
FU | Yes | none | None |
FUDUPH9 | Yes | DuoGard (d) Phorate (ap) | 9 |
FUDU | Yes | DuoGard (d) | None |
FUEF4PH9 | Yes | EF400 (d) Phorate (ap) | 9 |
FUEF4 | Yes | EF400 (d) | None |
FUEF3PH9 | Yes | EF300 (d) Phorate (ap) | 9 |
FUEF3 | Yes | EF300 (d) | None |
FUPH5FO | Yes | Phorate (ap) Fosthiazate (ap) | 4.5–4.4 |
FUPH5ET8 | Yes | Phorate (ap) Ethoprop (ap) | 4.5–7.8 |
FUFO2X | Yes | Fosthiazate (ap) (pp) | 4.4–4.4 |
FUCIPH9 | Yes | Cinnamite (d) Phorate (ap) | 9 |
FUCI | Yes | Cinnamite (d) | None |
CIPH9 | No | Cinnamite (d) Phorate (ap) | 9 |
CI | No | Cinnamite (d) | None |
PH5FO | No | Phorate (ap) Fosthiazate (ap) | 4.5–4.4 |
PH5ET8 | No | Thimet (ap) Ethoprop (ap) | 4.5–7.8 |
FO2X | No | Fosthiazate (ap) (pp) | 4.4–4.4 |
PH9 | No | Phorate (ap) | 9 |
ET13 | No | Ethoprop (ap) | 13.4 |
UC | No | None | None |
Notes: aFU = Preplant treatment of 1,3-Dichloropropene at 428 kg a.i./ha plus metam sodium at 407 kg a.i./ha; bkg a.i./ha is expressed as the amount of product that was actually applied.
Planting stock was “Nellie White” bulblets hand graded from scale bed production of the previous year’s crop and weighed approximately 7 g each. For all treatments, bulblets were dipped for 1 hr at 12°C in a freshly made fungicide solution of 0.72 kg a.i. pentachloronitrobenzene (Terraclor 400, 40% PCNB, Uniroyal Chemical Company, Middlebury, CT), 0.95 kg a.i. tetramethylthiuram disulfide (42-S Thiram, Gustafson, Plano, TX), 0.81 kg a.i. carboxin (Vitavax-34, Gustafson, Plano, TX), 0.052 kg a.i. thiophanate-methyl (SysTec, Regal Chemical Company, Alpharetta, GA), and 1% M-Pede (Dow AgroSciences Indianopolis, IN), per 379 liters of water and planted within 24 hr of treatment. For EO treatments, the products were added to the fungicide dip solution. Following treatments, levels of nematodes in bulblets were reduced compared to UC but not eliminated.
Bulblets were planted in October each year in a field that is managed to maintain a population of
Two trials were conducted in consecutive years in a randomized complete block design with three replicates of 75 bulblets each per treatment. Plots were one row (1.02-m) wide by 6-m long. The circumference of each harvested bulb was measured and means per plot presented. Additional variables analyzed were percent survival, weight of foliage from five randomly selected plants, a visual rating of roots from 1 (poor) to 10 (excellent) as a measure of root health, and weight of bulblets from the same five plants. Following harvest, soil and root samples were transported to the University of California Davis Cooperative Extension Nematode Diagnostic Laboratory. Within one week, nematodes were extracted from soil using a modified semiautomatic elutriator and sugar flotation technique (Byrd et al., 1976). Nematodes were extracted from roots cut from the base of five bulbs per replicate. Roots were washed, weighed and placed in an intermittent misting chamber for 72 hr. Extracted nematodes were identified, then counted using a stereoscopic microscope. Because the soil nematode population in the UC in Trial 1 was double that in Trial 2, results were evaluated for each trial separately using analysis of variance followed by LSD testing at
In the first trial, 13 treatments, including all EO treatments, but not the standard FUPH9 had a greater bulb circumference than UC (
Effect of treatments on bulb circumference and root health.
Bulb circumference (cm) | Root ratinga | |||
---|---|---|---|---|
Treatment | Trial 1 | Trial 2 | Trial 1 | Trial 2 |
FUPH9 | 14.0 | 13.6* | 5.7 | 4.3 |
FUET13 | 14.1 | 14.3* | 6.3* | 3.7 |
FU | 14.1 | 14.2* | 4.3 | 5.7 |
FUDUPH9 | 14.6* | 14.3* | 4.7 | 4.3 |
FUDU | 14.7* | 14.4* | 4.3 | 5.3 |
FUEF4PH9 | 14.5* | 14.1* | 5.2 | 5.3 |
FUEF4 | 14.9* | 14.6* | 3.3 | 6.3* |
FUEF3PH9 | 14.6* | 14.2* | 4.0 | 6.3* |
FUEF3 | 14.7* | 14.2* | 4.3 | 5.3 |
FUPH5FO | 14.6* | 13.6* | 7.0* | 7.3* |
FUPH5ET8 | 14.6* | 13.7* | 5.3 | 7.0* |
FUFO2X | 14.2 | 14.0* | 6.3* | 6.8* |
FUCIPH9 | 14.5* | 14.1* | 7.3* | 6.0* |
FUCI | 14.7* | 14.0* | 6.7* | 5.7 |
CIPH9 | 14.6* | 13.0 | 7.0* | 4.8 |
CI | 14.5* | 12.2 | 7.0* | 3.0 |
PH5FO | 14.4* | 13.5 | 7.7* | 4.7 |
PH5ET8 | 13.9 | 13.1 | 6.3* | 4.3 |
FO2X | 13.7 | 13.6* | 6.3* | 4.7 |
PH9 | 13.1 | 13.3 | 4.7 | 5.7 |
ET13 | 13.4 | 13.6* | 5.3 | 4.3 |
UC | 13.4 | 12.8 | 4.0 | 3.7 |
LSD | 0.927 | 0.744 | 1.990 | 2.085 |
Notes: Data are means of three replicates. *Significantly different from UC at p ≤ 0.05; aroot rating was subjective on a scale from 1 = poor to 10 = healthy looking.
In the first trial, no treatments had greater survival than UC, and one treatment had lower survival (
Effects of treatments on survival and growth of Easter lilies.
Foliage Weight | Bulblet Weight | |||||
---|---|---|---|---|---|---|
Bulb survival (%)a | (5 plants) (g) | (5 plants) (g) | ||||
Treatment | Trial 1 | Trial 2 | Trial 1 | Trial 2 | Trial 1 | Trial 2 |
FUPH9 | 98 | 96* | 111.3 | 129.3* | 2.9* | 2.7 |
FUET13 | 96 | 87 | 137.3* | 117.3* | 2.7 | 2.4 |
FU | 94 | 93 | 93.3 | 102.7* | 2.1 | 3.1* |
FUDUPH9 | 100 | 95 | 103.3 | 96.7* | 2.4 | 2.8* |
FUDU | 93 | 97* | 142.0* | 122.0* | 3.3* | 2.9* |
FUEF4PH9 | 96 | 91 | 124.0 | 91.3* | 3.2* | 3.0* |
FUEF4 | 95 | 100* | 100.7 | 110.7* | 2.3 | 2.7 |
FUEF3PH9 | 95 | 89 | 122.0 | 132.0* | 3.6* | 2.7 |
FUEF3 | 98 | 95 | 118.7 | 104.0* | 2.6 | 4.4* |
FUPH5FO | 94 | 91 | 126.3 | 111.3* | 2.2 | 3.3* |
FUPH5ET8 | 96 | 94 | 128.0 | 104.0* | 2.3 | 3.3* |
FUFO2X | 96 | 96 | 120.3 | 119.3* | 2.2 | 2.7 |
FUCIPH9 | 72* | 94 | 133.3* | 107.3* | 2.5 | 3.2* |
FUCI | 96 | 96* | 118.7 | 96.0* | 3.2* | 2.9* |
CIPH9 | 95 | 85 | 147.7* | 73.3 | 3.3* | 1.5 |
CI | 94 | 87 | 122.7 | 56.7 | 2.2 | 1.5 |
PH5FO | 96 | 90 | 142.0* | 95.3* | 2.0 | 2.6 |
PH5ET8 | 91 | 86 | 132.0* | 65.3 | 1.9 | 1.9 |
FO2X | 92 | 88 | 109.7 | 103.3* | 1.7 | 3.3* |
PH9 | 90 | 92 | 91.3 | 88.7* | 2.0 | 2.4 |
ET13 | 92 | 90 | 106.0 | 97.3* | 1.6 | 2.6 |
UC | 95 | 87 | 95.0 | 52.7 | 1.5 | 1.3 |
LSD | 13.785 | 9.287 | 36.157 | 33.182 | 1.251 | 1.436 |
Notes: Data are means of 3 replicates. aBulb survival out of 75 planted per replicate; *significantly different from UC at p ≤ 0.05.
Three treatments in the first trial, including the standard, but none in the second trial had a lower level of lesion nematode in soil at harvest than UC (
Effect of treatments on densities of
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---|---|---|---|---|
Soil (n/1,000 cm)3 | Roots (n/g) | |||
Treatment | Trial 1 | Trial 2 | Trial 1 | Trial 2 |
FUPH9 | 16.7* | 16.7 | 51.6* | 16.5* |
FUET13 | 116.7 | 33.3 | 42.2* | 7.3* |
FU | 283.3 | 133.3 | 131.2 | 70.5* |
FUDUPH9 | 300.0 | 16.7 | 72.9 | 10.6* |
FUDU | 283.3 | 66.7 | 63.9* | 53.0* |
FUEF4PH9 | 116.7 | 33.3 | 29.3* | 15.5* |
FUEF4 | 183.3 | 66.7 | 194.5 | 63.8* |
FUEF3PH9 | 183.3 | 0.0 | 140.7 | 46.4* |
FUEF3 | 333.3 | 50.0 | 250.9 | 33.9* |
FUPH5FO | 66.7 | 33.3 | 29.7* | 0.5* |
FUPH5ET8 | 150.0 | 50.0 | 56.9* | 31.5* |
FUFO2X | 33.3* | 0.0 | 18.3* | 0.4* |
FUCIPH9 | 33.3 | 16.7 | 21.2* | 45.2* |
FUCI | 250.0 | 100.0 | 224.3 | 44.3* |
CIPH9 | 350.0 | 33.3 | 230.8 | 175.2 |
CI | 333.3 | 66.7 | 150.6 | 121.4 |
PH5FO | 16.7* | 33.3 | 16.4* | 53.7* |
PH5ET8 | 200.0 | 50.0 | 72.7 | 103.3 |
FO2X | 83.3 | 16.7 | 75.0 | 29.7* |
PH9 | 250.0 | 166.7 | 117.7 | 120.7 |
ET13 | 200.0 | 50.0 | 355.0 | 116.8 |
UC | 266.7 | 133.3 | 256.2 | 157.4 |
LSD | 319.6 | 135.136 | 185.75 | 72.328 |
Notes: Data are means of three replicates. *Significantly different from UC at p ≤ 0.05.
Based on the overall frequency of statistically significant results (
In both trial 1 (
Of the criteria evaluated, bulb circumference and root rating are the most important to growers. Trial 1 did not reveal any significant correlation between nematodes present in roots or soil and the growth characteristics evaluated. In Trial 2, there was good correlation between nematodes present in roots and bulb circumference (
Bulb circumference is the most important criteria for marketing bulbs. Based on this, all four of the EO treatments (DuoGard, EF400, EF300 and Cinnamite) significantly improved bulb circumference when used in combination with the fumigant. Addition of an organophosphate did not provide an increase in bulb circumference. Using either a fumigant or organophosate treatment alone did not consistently increase bulb circumference. The two most effective chemical combination treatments were fumigant plus phorate with fosthiazate, and fumigant plus phorate with ethoprop.
In the Easter lily cropping system, severe pest pressure resulting from both nematode infested soil and infected planting stock results in growers typically using a dual nematicide application consisting of a dual preplant fumigant treatment followed by an organophosphate at planting. Even the standard products utilized by growers have shown year-to-year variability working better in some years than others (L.J. Riddle, pers. comm.), as they did in the present trials. In previous trials testing CI (but not the other EO products), CI had shown good but inconsistent results when used alone (unpubl. data) and was again tested alone in these trials. Because of the previous inconsistent results with CI, we chose to test all the EO products in combination with a fumigant, or fumigant plus organophosphate to see if they could provide an improvement over or replace a component of the standard treatment.
Recent research has also shown that EOs have activity against insects and plant disease organisms and may also promote plant growth in the absence of pests (Gupta et al., 2011; Pingsheng et al., 2007). In a field trial, Abo-Elyousr et al. (2009) found that a mixture of EOs was less effective than oxamyl at controlling root-knot nematode on tomatoes but provided a significantly greater increase in yield than did oxamyl. It is likely that similar plant growth interactions are occurring in the present trials. However, the reductions in nematode populations that were obtained in our trials indicate that nematode control is an important component of the improvement in plant growth that was achieved as a result of the EO treatments.
In spite of the inherent variability in physical and biological factors, our trials demonstrated that the EO products improved bulb circumference, foliage weight, root health and reduced nematode pressure over the UC in multiple treatments in both years of the trials. In spite of the variability that naturally occurs in field trials conducted over multiple years, our results were fairly consistent. When used with FU but not in combination with PH9, EO products performed similarly to FUPH9 in both trials. Thus, these products show potential for use in conjunction with a preplant fumigant. This is an important finding for producers to meet their overall goal of reducing pesticide use.