The Adelaide Plains region, located just outside of Adelaide, South Australia, is the largest greenhouse growing region (1500ha) in the southern hemisphere. This region suffers from soil pest and disease issues that greatly reduce the yields and quality of the crops grown. Soil fumigation has traditionally been the main method to suppress these soilborne pests and diseases. Soil fumigation in past times has been very hit and miss, with prescriptive fumigation only in recent times becoming the most cost-effective method employed. This trial was undertaken to show the effective control of Root Knot Nematodes, utilising Strike 60 applied at 500kg/ha. This trial was part of a larger project that looked at not only the effects of soil fumigation but the effects of efficient water and fertiliser use on crops grown in fumigated greenhouse soil. Detailed soil pest and disease testing has previously never been undertaken at weekly intervals to see the effectiveness of nematode suppression. This work aimed to fill this information void.

Capsicums are grown in sandy loam soils covered by a climate-controlled poly greenhouse. All water, fertiliser, and temperature are controlled by using computer systems that monitor and dispense crop inputs and environments. Greenhouse 4, which was used for this trial, is representative of all 8 greenhouse structures on the farm. Greenhouse 4 is 2000 m2 in size. The last crop was chopped up and incorporated into the soil by using a rotary hoe. The area was then deep ripped by using a three tined ripper to break up the sub soil clay pan. Compost, gypsum and base fertiliser were applied to the soil and then incorporated by using a rotary hoe. The soil was watered until it was approximately 10% wet. The soil was sampled for pests and diseases by using the South Australian Research & Development Institute (SARDI) Predicta DNA panel tests (Figure 1). Thirty-five soil cores sampled along a full row of plants to a depth of 15cm were collected and sent for laboratory analysis.

The last crop was chopped up and incorporated into the soil by using a rotary hoe. The area was then deep ripped by using a three tined ripper to break up the sub soil clay pan. Compost, gypsum and base fertiliser were applied to the soil and then incorporated by using a rotary hoe. The soil was watered until it was approximately 10% wet. The soil was sampled for pests and diseases by using the South Australian Research & Development Institute (SARDI) Predicta DNA panel tests (Figure 1). Thirty-five soil cores sampled along a full row of plants to a depth of 15cm were collected and sent for laboratory analysis.

The fumigation rig applied the fumigant at a depth of 30cm.The soil was rotary hoed to a depth of 20cm, and then the soil surface was rolled to seal the fumigant into the soil. The fumigated soil was then watered for one hour with overhead sprinklers, until the top 50mm of soil was moist with a crust. This 50mm moist layer provided additional sealing of the fumigant. The watering seal was applied again 3 days later, repeating the sealing action for another 3 days duration. Watering was stopped at day 8 after the soil fumigation.

Soil samples were taken weekly for 5 weeks after planting, to monitor for soil pest and disease numbers. Specifically, Root Knot Nematode populations were monitored to see the effect of soil fumigation to decrease numbers to below economic damage levels. Soil pest and disease numbers were calculated from the SARDI tests by sampling at the base of the plants in the rows, 10cm out from the stem base. A combined test and a specific test for M. incognita were employed. Samples were again taken at 9 weeks after planting (date) and then again at the end of the crop at 38 weeks (date). The end of the crop information showed an increase in numbers.

Population numbers for three Root Knot Nematode species (M.incognita, M.javanica, and M.arenaria) before fumigation were above 220 / g of soil (Table 1). This number included eggs, juveniles, and adult nematodes. 14 days after the application of Strike 60, nematode numbers had collapsed to 16 / g soil. Numbers every week after planting showed a gradual overall decrease from 16 to 5 / g soil at 5 weeks after planting (date). There is variation in numbers (both up and down), due to sample not taken from the exact same position as the prior test. At 9 weeks after planting (date), nematode numbers decreased to 3/g soil. As expected, at the end of the crop, nematode numbers had increased dramatically to just under 1600 /g soil.

M. incognita nematodes were monitored as a separate pest, as they specifically infect Capsicum plants. Nematode numbers began at just over 100 / g soil and then decreased to undetectable levels after soil fumigation. They then increased to around 60 /g soil up to week 9 after planting. At the end of the crop’s life, nematode numbers peaked at ~2670 / g soil.

Prior to the use of soil fumigation, crop yields were averaging 7.5kg/m2 (75 MT/ha) for the capsicum crop. Soil fumigation with Strike 60 increased crop yields to 22.5 kg/m2 (225MT/ha) (Figure 6). Irrigations were reduced by a factor of 25%, and fertiliser use efficiency was improved by 30%. Crop wastage was reduced to 5% as compared to 30% without soil fumigation.

Root Knot Nematodes are the leading cause of yield decline of crops grown in greenhouse soil on the Adelaide Plains. The greatest damage is done to seedling roots during the first four weeks after planting. Once the damage is done, it retards the plant’s growth for the rest of the plant’s life. This trial has shown that the application of Strike 60 at 500kg/ha can drastically reduce the damage done to the Capsicum roots in the first 3 weeks after planting, thereby allowing the plants to have an improvement of 25% water uptake and 30% increase in fertiliser extraction. These improvements are then translated into higher crop yields and a decrease in crop wastage. The application of Strike 60 at 500kg/ha has allowed Root Knot Nematode numbers to be suppressed up to 9 weeks after planting. The suppression has provided major economic gains by increasing production and profitability per unit area of land.

Strike 60 applied at 500kg/ha has proven that it can suppress Root Knot Nematode numbers whilst delivering large increases in crop yields. It is recommended that the Strike 60 Label be amended to show the application rate of 500kg/ha untarped and broadcast applied for horticultural soils.