Abstract

A field trial was established in cabbages to determine the efficacy of AzaMax^®, a commercial formulation of 12 g/L azadirachtin (derived from neem kernels) against diamondback moth (Plutella xylostella (L.) Lepidoptera: Plutellidae), cabbage white butterfly (Pieris rapae (L.) Lepidoptera: Pieridae) and heliothis (Helicoverpa armigera (Hübner) Lepidoptera: Noctuidae). Results demonstrate the effectiveness of 0.5 L/ha, 1 L/ha, 2 L/ha and 3 L/ha of AzaMax^® alone and in combination with a crop oil and a commercially available Bacillus thuringiensis (Bt) formulation. A comparison of the efficacy of AzaMax^® with that of fipronil was also investigated.

Keywords

organic, Plutella, neem, AzaMax^®

Introduction

Azadirachtin is a natural insecticide derived from the kernel of the neem tree (Azadirachta indica Juss). Azadirachtin has significant potential as a commercial insecticide, but stability problems have always restricted its performance and use in commercial formulations. Recently, Trifolio-M GmbH developed a method to extract azadirachtin directly from neem tree (A. indica) kernel. This process produces a very stable form of azadirachtin due to significant reductions in destabilising impurities. The powdered azadirachtin extract is commercially available as NeemAzal Technical and is used in various formulations for the control of a wide range of pests throughout the world. It has now found a niche within organic cropping situations as alternative chemistry to the use of Bt sprays.

NeemAzal Technical has the following specifications:

Through a joint venture between Organic Crop Protectants Pty Ltd (OCP) and EID Parry of India, OCP are developing the use of a 12 g/L formulation of NeemAzal Technical for the control of various crucifer pests in Australia, Tradename AzaMax^®.

Materials and methods

A field trial was conducted in the Dandenong region of Victoria with various treatments (Table 1) from early February to mid March to compare the efficacy of AzaMax^®, fipronil and a commercial Bacillus thuringiensis formulation. The target crop was Savoy Cabbage (Planted 31/1/00 – Harvested 1/4/00). All lepidopteran species that were present in any significant numbers were evaluated. The trial was set out as a randomised complete block design with four replicates. Plot size was 4 rows wide by 5 metres long. All assessments were made within the middle of each plot. Insect assessments were carried out immediately before each application of the treatments and 8 days after the final application.

Assessments were carried out by counting the number of diamondback moth (DBM), cabbage white butterfly and heliothis larvae on five randomly selected cabbage plants from the middle of each plot. The larvae were differentiated as: small <4 mm, medium 5-8 mm, large >8mm.

Treatments were applied using a gas operated hand-held sprayer with hand wand boom attached incorporating TX – 8 hollow cone nozzles (application 1) or five TX – 12 hollow cone nozzles (applications 2-6). One 1.25 m pass was made over the top of each row of cabbages at a pressure of 300 kPa, walking at 1 m/second. Total volumes of 290 L/ha (application 1) and 490 L/ha (application 2-6) were applied respectively. Details of application dates and spraying conditions are provided in Table 2.

Table 1. Insecticide treatments and rates for a field trial of of AzaMax^®, fipronil and a commercial Bacillus thuringiensis formulation against pest Lepidoptera on Savoy Cabbage, Dandenong, Victoria, Australia, 2000

* Regent 200SC contains 200g/L fipronil and is a Registered Trademark of Aventis Corp, ^ -DiPel Forté DF contains Bacillus thuringiensis subspecies. kurstaki, strain HD-1 and is a Registered Trademark of Sumitomo Chemicals.

Table 2. Application dates and spraying conditions for field trial of of AzaMax^®, fipronil and a commercial Bacillus thuringiensis formulation against pest Lepidoptera on Savoy Cabbage, Dandenong, Victoria, Australia, 2000

Results

Diamondback moth

Results of DBM control are summarised in Figure 1 and represent cumulative mean numbers of larvae. A high to very high population of DBM was detected during the trial. Standard treatments of fipronil and Bt and AzaMax^® @ 3L/ha provided good control of all sizes of larvae.

AzaMax^® applications of 0.5 L/ha and 1.0 L/ha did not provide adequate control of DBM under the high pressure experienced during the trial. AzaMax^® @ 2 L/ha was not significantly different from AzaMax^® @ 3L/ha at the 95% level of probability.

Figure 1. Cumulative mean numbers of DBM larvae/per 5 Savoy Cabbage plants in a field trial of AzaMax^®, fipronil and a commercial Bacillus thuringiensis formulation, Dandenong, Victoria, Australia, 2000.

Heliothis

A small population of heliothis developed midway through the trial. Results of heliothis control are summarised in Figure 2. AzaMax^® at application rates of 0.5, 1.0, 2.0 and 3.0 L/ha all controlled heliothis under a low infestation situation.

Figure 2. Cumulative mean numbers of Heliothis larvae/per 5 Savoy Cabbage plants in a field trial of AzaMax^®, fipronil and a commercial Bacillus thuringiensis formulation, Dandenong, Victoria, Australia, 2000.

Cabbage white butterfly

A very small population developed mid way through the trial. Results of cabbage white butterfly control are summarised in Figure 3. All treatments provided similar levels of control of all larvae sizes excluding AzaMax^® @ 0.5 L/ha which provided significantly poorer control when the total number of larvae were counted. No significant difference was detected for the level of control provided by AzaMax^® at application rates of 1.0, 2.0 and 3.0 L/ha.

Figure 3. Cumulative mean numbers of cabbage white butterfly larvae/per 5 Savoy Cabbage plants in a field trial of AzaMax, fipronil and a commercial Bacillus thuringiensis formulation, Dandenong, Victoria, Australia, 2000.

Discussion

AzaMax^® did not perform as well as Bt or fipronil under high populations of DBM. However the 3 L/ha rate of AzaMax^® did offer similar levels of control to the standard treatments. There is evidence to suggest from this trial that AzaMax^® will control heliothis and cabbage white butterfly, however its efficacy under medium to high pest pressure needs further investigation.

AzaMax^® did not appear to enhance the efficacy of Bt in this trial probably because the antifeedant effect of azadirachtin was antagonistic to the ingestion of the Bt.

From this trial it appears that AzaMax^® has significant potential as alternative chemistry for the control of DBM and other lepidopteran pests of crucifer crops. Furthermore its activity against other pests including aphids and thrips makes AzaMax^® a very versatile product within Integrated Pest Management systems that utilise highly selective insecticides.

There is a definite need for a product like AzaMax^® in organic production systems within Australia due to the lack of any alternative control options for DBM and other lepidopteran pests. Currently growers are forced to use Bt sprays on a regular basis, which will eventually cause resistance to develop and potentially jeopardize the life span of Bt in conventional agriculture.

Acknowledgements

Agrisearch Services Pty Ltd for conducting the Field Trial