EFFECT OF UMBELLIFERAE (APIACEAE) PLANT WATER EXTRACTS ON COLORADO POTATO BEETLE (LEPTINOTARSA DECEMLINEATA SAY) FEEDING AND DEVELOPMENT

Maria Wawrzyniak, Robert Lamparski
Department of Applied Entomology, University of Technology and Agriculture, Bydgoszcz, Poland

ABSTRACT

The present research aimed at defining the effect of selected Umbelliferae plant water extracts on Colorado potato beetle feeding and development. Under lab and field conditions water extracts from the following plants were analysed: fennel (Foeniculum capillaceum Gilib.), garden angelica (Archangelica officinalis Hoffm.), common caraway (Carum carvi L.), garden lovage (Levisticum officinale Koch.) and coriander (Coriandrum sativum L.). It was found that the extracts tested affected the feeding effectiveness and the development potential of beetle significantly. Under lab conditions there was observed an inhibition of larva and beetle development and a decrease in feeding effectiveness of all the extracts tested. The highest antifeedant activity was shown by the extracts from Carum carvi and Archangelica officinalis. The extracts studied also decreased the number of larvae incubated and affected the pupation process. Under field conditions all the extracts analysed limited oviposition by Colorado beetle females on potato plants significantly. The overwintering beetles and larvae were most affected by the extract obtained from Coriandrum sativum.

Key words: Leptinotarsa decemlineata, Umbelliferae, plant extracts.

INTRODUCTION

Chemical pest control involves a regular introduction of new insecticides coupled with the prevention of pests from resistance development. At the same time natural environment and human health protection measures are considered [23]. Therefore plant protection policy over the last years has shifted from pest killing to population development control, dealt with a new branch of science, chemical ecology, which describes the interspecies rules and relationships controlled by chemical agents. Chemical ecology covers compounds affecting the behaviour of insects: antifeedants, repellents, attractants, arrestants [25].

Antifeedants are described as substances inhibiting feeding and oviposition, which do not kill the pest directly but limit its development potential considerably and act as a fagodetergent or fagorepellent over test and permanent pest feeding on the plant. Their great advantage is a selective action against parasites, pest predators as well as pollinators. These substances can change pest physiology processes, e.g. by disturbing instinct activity chain, which condition feeding. Antifeedants of natural origin are foremost different plant substances, found in abundance in tropical plants [3,4]. Plant substances acting as antifeedants are found in all the compound groups of secondary plant metabolism. However the most effective insect feeding inhibitors come from terpenoids, alkaloids, quinones, glycosides, saponins, flavonoids, complex esters and essential oils [6]. There is a high potential for finding antifeedants in plants, however, only a few substances have been found so far and so the possible applications of antifeedant plants in pest control seem to be considerable. Before it is possible, extensive research must be made to find plants whose extracts show activity towards different species of harmful insects. With that in mind, the most harmful potato pest, Colorado beetle, has been researched by many authors around the world [7,8,13,14,17,19] and in Poland [5,11,12,15,26,27,29,31,32,33,34]. The literature available does not seem to offer enough data on the effect of extracts from different plants on feeding and development of this pest whose abundance exceeds much the economic harmfulness threshold each year. All that calls for a permanent protection of potato fields with chemicals, which increases the risk of environmental contamination and development of resistant beetle lines. Colorado beetle is a pest which develops resistance to all the pesticides known, including photostable pyrethroids [16].

The research hypothesis assumed that the compounds of secondary metabolism found in Umbelliferae plants can effect insect population. The aim of the present paper was to define the effect of water extracts obtained from selected plants of Umbelliferae family on Colorado beetle feeding and development.

MATERIAL AND METHODS

The 2003-2004 study involved a lab experiment made at the Department of Applied Entomology and a field experiment – in potato fields of the Mochełek Experiment Station of the University of Technology and Agriculture in Bydgoszcz. Field observations involved winter beetles, eggs and larvae of Colorado beetle, collected from potato plantations for lab experiments. Similarly, to obtain eggs and beetles of summer generation, insects were incubated in the lab.

The experiment tested 10% water extracts obtained from 5 species of Apiaceae family.

Fennel (Foeniculum capillaceum Gilib.) fruit contains 3-4% of essential oil, including carvone, limonene, phellandrene, terpinene – substances water-insoluble and multi-phenolic acids (caffeic and chlorogenic), flavonoids, e.g. vicenin, coumarin compounds e.g. esculetin, umbelliferone and scopoletin, as well as mineral salts and protein compounds [10,22], well soluble in water.

Garden angelica (Archangelica officinalis Hoffm.) in all its parts contains essential oil. The main components of the oil are water-insoluble terpenes and odorous compounds, lactone in character. The second important group is usually made up of water-soluble coumarin compounds and furanocoumarin compounds, and numerous organic acids, phytosterols and their esters, flavonoids [10,22].

Common caraway (Carum carvi L.) fruit contains essential oil with carvone and limonene (terpenes) as well as fat oil, protein compounds, sugars, mineral salts and well water-soluble flavonoids, organic acids and coumarin [10,22].

Garden lovage (Levisticum officinale Koch.) roots contain essential oil including lactones and other terpene-derivatives. There also occur polyphenolic acids, coumarin compounds and sugars, choline, phytosterols, organic acids and mineral salts [10,22].

Coriander (Coriandrum sativum L.) fruit includes numerous terpenes, as well as flavonoids, coumarin compounds, phytosterols, polyphenolic acids, fat oil, protein compounds and carbohydrates [10,22].

Plant-dried material was purchased from herbalist’s shops and ground, and then poured with cool water for 24 h at the ratio 1:10. Having been filtered through filter paper, the extract obtained was assumed as a 10% extract.

Laboratory experiments

Laboratory experiments defined the effect of the extracts on Colorado potato beetle feeding and development. To determine the effect of the plant extracts studied, weighted potato leaves were immersed for about 3 seconds and, after drying, put onto the Petri dishes. Each dish, filled with leaves, was provided with one couple of beetles or 10 previously weighted L3 larvae. The experiment was 48 h long and involved the replacement and supplementing of feed. The test and control combinations (untreated dry leaves) were set up in 4 replications. After 48 hours the remaining leaves and insects were weighted again. With data obtained the following were defined:

• weight of food eaten by larvae and beetles (calculations factored in weight losses due to evaporation at 20°C and 80% RH),

• larvae body weight changes,

• effectiveness of food intake by larvae (calculated from the ratio of the consumed food weight to the larvae weight gain),

• absolute deterrence index (BWD) according to the formula [9]:

BWD = [(K – T) : (K + T)] x 100

where:
K – weight of food consumed in the control,
T – weight of food consumed with extract added.

In case of no feeding at all, BWD approaches 100%, while BWD which equals 35 accounts for about 50% feeding reduction as compared with the control.

Analyzing the effect of extracts on Colorado potato beetle, the following were observed:

• female fecundity – beetle pairs were fed with potato leaves treated with the plant extracts studied; the number of eggs laid per female was noted,

• development of larvae from eggs treated with the extracts tested – eggs oviposited on potato leaves in the field were covered with extracts with a brush and left on Petri dishes. The test was made in 4 reps and the control involved non-treated eggs. In each combination incubating larvae were counted, assuming that the eggs from which larvae did not incubate – died off as affected by the extract,

• effect of the extract on the effectiveness of Colorado potato beetle pupation – L4 larvae, after 48 hours of feeding on leaves treated with extracts, were placed in the box filled with sand where pupation occurred; beetles were counted and weighted.

Field study

The effect of Umbelliferae extracts on the abundance of egg deposits, larvae and imagines of Colorado potato beetles was analyzed.

The effect of extracts on potato beetles and larvae

The observations were made on 5 x 5 m potato plots (20 plants per replication) prior to the treatment and 2 and 6 days latter. Each plant extract was tested in 4 reps. Four potato rows were randomly selected from each plot. The plants were sprayed with 1 dm³ of extract per plot (400 dm³·ha^-1). The reaction of the insects to the water extracts applied was evaluated with the use of the Henderson-Tilton formula:

Efficacy % = 1 – [(K1 x A2) : (K2 x A1)] x 100

where:
K1 – number of insects per control plot prior to the treatment,
K2 – number of insects per control plot after the treatment,
A1 – number of insects per test plot prior to the treatment,
A2 – number of insects per test plot after the treatment.

Effect of extracts on egg lying by females

The observations followed the same method assumptions. Egg deposits were destroyed once they were counted. The number of egg deposits on plants treated in respective experimental combination was compared to the number of egg deposit on the control plants.

The results were statistically verified with variance analysis with a single classification in a completely randomized design. The significance of differences was determined with Tukey’s confidence semi-intervals at α = 0.05.

RESULTS

Effect of water extracts on potato beetle feeding

Beetle feeding
There was found a very strong effect of the extracts tested on the beetle feeding. The analysis of food consumption (Table 1) revealed that in respective experimental tests beetles consumed only from 0.65 to 9.5% of the potato leaf weight as compared with the control. The results coincide with the value of BWD (Fig. 1), and especially strong effect was found for Common caraway (BWD = 96) and for Garden angelica (BWD = 94) extracts.

Larvae feeding
The plant extracts studied also limited food consumption by larvae, however to less extent than by beetles. The weight of the food consumed ranged from as much as 37.5 to 60%, as compared with the control. For respective extracts there were obtained also lower values of BWD, yet still indicating larvae feeding inhibition. The highest BWD values (Fig.1) were found for common caraway (46) and fennel extracts (43).

The water extracts tested significantly limited Colorado potato beetle larva body weight gain. In the combination in which larvae were fed with leaves with fennel extract no body weight gain was noted, while in the other combinations the larva body weight gain ranged from 5 (garden angelica) to 13% (common caraway) as compared with larva body weight gain in the control (Table 1).

In all the experimental combinations there were found significant differences in the effectiveness of food consumption, that is the amount of food used per 1 mg of larva body weight. Having used the fennel extract, no larva body weight gain was recorded. Very high food consumption (from seven-fold to eleven-fold higher than the control) was demonstrated in larvae fed with leaves treated with extracts from coriander, garden lovage and garden angelica (Table 1).

Effect of the extracts tested on the development of Colorado potato beetle

Oviposition
It was shown that the water extracts studied (except for common caraway extract) significantly decreased the fecundity of Colorado potato beetle female. The number of eggs oviposited in the test combinations in which beetles were fed on leaves treated with extracts ranged from 16 to 30%, as compared with the number of eggs oviposited in the control, whereas in the combination which involved common caraway extract – it accounted for 75% (Table 2).

Larvae incubation
The plant extracts tested decreased the effectiveness of larva incubation (Table 2). From the eggs which were treated with the extracts from 70% (following the application of garden lovage extract) to 90-93%, larvae (in the tests with the other extracts) were incubated. The other eggs died off. The statistical analysis demonstrated that the differences between the number of larvae obtained in the control (97.5%) and the other combinations were significant.

Pupation
L4 larvae feeding with the plant extracts tested affected the pupation process. The number of beetles obtained in the extract combinations was significantly lower (except for the fennel extract test), than in the control (Table 2). However, the weight of these beetles did not differ from the control ones (garden lovage was the only one which resulted in a significant body weight gain).

Effect of Umbelliferae water extracts on the number of egg deposits, larvae and imagines of Colorado potato beetle on potato plants

Observations made after 2 days of potato plant treatment with the Umbelliferae plant extracts tested on all the plots on which extracts were used revealed a lower activity of Colorado potato beetle females. There were found significant differences in the number of egg deposits and the number of eggs oviposited between the control and respective combinations tested. Similar results were noted after successive 4 days. The lowest oviposition was observed on plants on which garden lovage and coriander extracts were applied (Table 3).

The results obtained for Colorado potato beetles differed. Two days after the treatment the number of beetles on the plants was mostly restricted by water extracts of coriander, fennel and garden lovage (Fig. 2). There were found significant differences between the effect of the three extracts and garden angelica and fennel extracts. After 6 days the strongest effect was found for coriander extract. Garden lovage, common caraway and fennel extracts decreased the number of beetles by about 50%.

The highest effect on Colorado potato beetle larvae, both 2 and 6 days after the treatment, was observed for coriander extract (Fig. 3). After 6 days also fennel and garden angelica extracts decreased the number of larvae by about 50% (the other extracts – by about 35%).

DISCUSSION

The present experiments revealed that the Umbelliferae water extracts tested affected the Colorado potato beetle feeding course and effectiveness as well as development potential significantly.

Natural substances contained in plants are a weapon which is alternative to traditional control of phytophagous insects. The substances were identified many years ago, investigating the properties of glycolalkaloids found in wild species of Solanum [28]. It is estimated that the plants can contain about 300 thousand compounds of secondary plant metabolism; only several percent of which have been known. A varied effect of respective plant extracts is mostly due to the content of active substances in plants. The quantitative and qualitative composition of these compounds changes a lot and depends on the plant development phase and environmental and climatic conditions as well as the solvent used [19]. It is not easy to evaluate which substance contained in the extract tested is more active. It happens that the isolated compound tested does not show the expected activity on its own. It is assumed that probably high extract effectiveness is a result of a synergetic interaction of its compounds. Of all the pharmacological components known so far, an active effect can be found mostly for numerous terpenes (compounds of low- water solubility) and coumarin compounds and flavonoids (well-soluble in water). All these compounds are considered to be active antifeedant substances [6].

All the extracts studied inhibited larvae and beetle feeding and decreased the effectiveness of food consumption considerably, indicating a possibly disturbed metabolism in larvae. The highest antifeedant activity was shown by the common caraway and garden angelica extracts. Basic components of common caraway are carvone and limonene representing terpenoids which are low water-soluble and therefore the antifeedant activity of that species was affected by coumarin and flavonoids, well-soluble in water [10]. Coumarin compounds, e.g. umbelliferone, umbeliprenin, ostenole as well as furanocoumarin, e.g. xantotoxin, xantotoxol, angelicin, imperatorin, bergapten, oxypeucedanin, archangelicain and apterin contained in the entire plant of garden angelica are an important group found in its composition. Similarly fennel, Colorado potato beetle feeding inhibitor, contains numerous coumarin compounds (esculetin, umbelliferone and scopoletin) [22]. The extracts studied also decreased both the number of incubating Colorado potato beetle larvae, which is an effect of their toxicity towards eggs, and the effectiveness of pupation due to the effect of extracts on larvae metabolism and as a result of larvae malnutrition.

Under field conditions all the extracts analyzed significantly inhibit egg oviposition by Colorado potato beetle females. Such inhibition can facilitate plant protection from their massive occurrence considerably, which must be due to the presence of aromatic compounds. The strongest oviposition inhibition was observed following the use of garden lovage containing water insoluble compounds but producing a specific odour – lactones sesquiterpens and numerous coumarin compounds, e.g. psoralene, bergapten, apterin and coumarin. The composition of coriander extracts, which also strongly inhibits oviposition and demonstrates the strongest effect on limiting the number of beetle and larvae on plants in the field, also includes considerable amounts of water insoluble borneol and strongly aromatic camphor, the product of its oxidation, as well as numerous amounts of coumarin: umbelliferone and scopoletin [22].

Umbelliferae plant extracts and their compounds were analyzed by many authors. Colorado potato beetles were found to be well controlled by furanocoumarin obtained from hogweed (Heracleum sphondylium L.) and wood angelica (Angelica silvestris L.) seeds [18]. A high activity of bisabolangelone isolated from Angelica silvestris L. seeds towards store pests [21], Colorado potato beetles [18], larvae of Noctuidae [24], large cabbage white [2]. Strong antifeedant properties of garden angelica, fennel and garden lovage towards large cabbage white caterpillar were reported by Abivardi and Benz [1] and Wawrzyniak [30]. The toxicity of garden lovage towards microorganisms is confirmed by Ożarowski and Jaroniewski [22] and towards store pests – by Nawrot [20], while a high effectiveness of garden angelica in limiting the number of large cabbage white eggs and larvae was found in Wawrzyniak [30] report.

CONCLUSIONS

1. Under laboratory conditions it was found that the Umbelliferae plant extracts studied

2. Field study revealed that

• the extracts obtained from garden lovage and coriander strongly limited oviposition,

• the extract from coriander showed also the highest activity towards overwintering beetles and larvae.

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Accepted for print: 16.11.2006

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