Bean and pea weevils

Credit: Carolyn Herriot

This is when I reach for the neem oil spray. I have found that applied in time repetitive sprays with neem oil will control weevils to the point where seedlings can outgrow further damage. Simple preventative methods like this are often enough to keep pests at bay.

TIP: Dilute neem oil according to instructions in warm water to dissolve it, and spray while still warm to keep the oil in solution.

Nematodes: This problem arises every year in my garden, so it’s time for the next stage of treatment, which is biological. If you have troubles with cutworms, whitegrubs, leatherjackets, wireworms or weevils you can use beneficial nematodes as a non-toxic biological control.

Nematodes are naturally-occurring, microscopic organisms that live in soil. Some, referred to as beneficial, prey on soil-borne insect larvae. They carry bacteria in their intestines which are deadly to host larvae. Within 24 hours the bacteria kill the host, and then feed on the remains. These nematodes are safe to non-target organisms such as earthworms.

Nematodes are easy to apply using a watering can or hose end sprayer, and are readily available at local garden centres. Apply when the soil has warmed up (13°C – 25°C). After watering keep the soil moist for 2 weeks. In 10 to 14 days your troubles will be over! TIP: Make sure the date stamp is still valid as they only have a three month shelf life.

4 steps to effective IPM:

1. Identify the problem. Sometimes what we think is a problem is actually part of the solution. The arrival of pests often invites predators to come and feast on a new food source. Make sure you don’t mistake welcome guests for harmful pests.

2. Observe to see if the problem gets better or worse. We often don’t notice a problem until it’s too late. Monitoring a potential problem gives clues as to how to prevent the problem. By keeping attention on your garden you can identify problems sooner, allowing quicker intervention for preventation.

3. Decide if damage is a problem. Gardeners can tolerate a degree of pest damage without even noticing it. How much damage you can live with? How serious is the damage? For example, in spring the leaf cutter bee chews notches in the edge of Epimedium leaves to build a nest. Knowing this, I can happily live with some temporary unsightliness before new leaves emerge to take over.

4. Take action. Start with the least toxic controls, such as physical and biological, to see if they work. Common controls include sticky traps, spraying with water and hand removal. Biological controls include parasitic nematodes. Controls may be used alone or in combination for greater effect.

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