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Step 1: Determine the LC₅₀ value from the chemical's SDS sheet – 4 mg/L (96 hours) for rainbow trout.
Step 2: Determine the LC₅₀ value for your system. Take the volume of your system in liters and multiply it by the LC₅₀ (96 hr) value. Let's use a 2,000-gallon (7,580 L) system as an example.
Step 3: Take the pyrethrin concentration and determine how much pyrethrin is being mixed. The label recommends mixing 1–2 fluid ounces of AzaMax with every gallon of water in compressed sprayers, which is between 2–4 Tbsp/gallon. In a 2,000 gallon system, the entire crop can be sprayed with 0.75 gallons of mix, which at the highest application rate is around 3 Tbsp (or 1.5 fluid ounces).
The label tells us that the product contains 0.35 g of azadirachtin per fluid oz. Convert g to lb:
0.35 g azadirachtin/ounce ÷ 454 g/lb = 0.0007716 lbs pyrethrin/fluid ounce
0.0007716 lbs pyrethrin/fluid ounce X 453,592 mg/lb = 350 mg pyrethrin/fluid ounce
Step 4: Determine how much pyrethrin is being applied to the system.
1.5 fluid ounces/system X 350 mg pyrethrin/fluid ounce = 525 mg pyrethrin/system
Step 5: Compare application concentration to LC50 of your system.
525 mg pyrethrin/system is much smaller than the LC50 value for a 2,000-gallon system 30,320 mg/system from step 2). This means that this product is SAFE to use in your aquaponic system. Even if a product is generally safe, limiting exposure to the water and organisms is still critical.
Mites: Mites are a very common pest, affecting hundreds of plants. These small arthropods are very small, often measuring less than 1 mm in length, and have sucking mouthparts. Damage to plants by mites includes brown stippling on leaves, upturned leaf margins, stunted plant growth, and webbing between plant structures (spider mites). Symptoms can mimic those of viral infections, particularly those caused by the broad mite, so identification should be done under a microscope. Mites typically have a 10-to-14 day life cycle and thrive in dark, humid conditions. Treatment options include neem oil and predatory insects such as ladybird beetles, lacewings, pirate bugs, predatory thrips, mites, and big-eyed bugs. Common types include Spider mite, Broad mite, Russet mite, and Cyclamen mites.
Aphids: A primary nemesis of most vegetable gardeners and plants, aphids can be very destructive to plants. Aphids are typically pear-shaped with two tail-like protrusions at the bottom of their abdomen (Figure 19a). The life cycle is very short, ranging from 10 days to three weeks. Their reproduction capacity makes them a particularly hard insect to control. Aphids can reproduce sexually or asexually and can switch between the two depending on the environment (Van Emden and Harrington 2017). Most aphids