I have been reading about IPM and am somewhat confused as to whether it is biological pest control. If so, it must be difficult to buy and manage the beneficial insects before the pests get overwhelming. Is there a different explanation?
Answer by RICK DONNAN
No, while IPM may include biological agents such as beneficial insects, it is a much wider range of techniques to sensibly manage pest and disease problems, in part by reducing the risk that they get into and spread through your crop. This is done to avoid resorting to what used to be the common use of ‘calendar spraying’, often using harsh chemicals, leading to environmental damage and pesticide resistance.
The NSW Department of Primary Industries (DPI) defines IPM as:
‘The use of multiple tactics to contain pests and diseases to tolerable levels’.
The following are the basic tactics used. They can be integrated in many different ways, but the overall aim is to reduce or preferably eliminate dependence upon harsh chemicals.
While rarely an option, if planning a new greenhouse check whether there are endemic pests or diseases in the area. In an existing greenhouse, you may consider changing to a less vulnerable crop if you have a major pest or disease problem (possibly coming from a nearby farm).
The main aspect of moving into IPM is to keep track of your problems and potential problems. This involves regular monitoring of the status of your pests and diseases. Usually, a specific person does a weekly inspection of specific plants and sticky traps. They record the number of disease symptoms, and pests and beneficials. This information is then used to determine what to do to keep potential problems under control. It helps to have all your staff aware and to report where they see any possible problems.
Where flying pests are a problem it is possible to screen the greenhouse to keep them out. The mesh must be of a suitable size to block the problem insect. All vents must be covered and it is best to have an air lock at the door as this is often the easiest access for the entry of pests. The finest mesh can exclude thrips, however, this also has the effect of halving the air flow through the vents. This can be helped through increasing the mesh area by ‘concertinaing’ the mesh frame.
This is critically important and goes much wider than the commonly known ‘footbaths’. (I visit greenhouses where the owner pours disinfectant into an obviously dry and unused footbath just before we enter—what a poor example for staff.)
To manage, so as to reduce pests and diseases, starts with setting up a ‘clean zone’ around your greenhouses and production area. This is quarantined from the other areas of your farm. Part of its function is to manage the access of plants, material, people and vehicles into the clean zone.
Because weeds are a common and severe source of pests and diseases, every greenhouse should have a weed-free zone around it at least five- and preferably 10-metres wide. Flowering weeds are particularly to be avoided as they provide shelter for many pests.
Leaving piles of plant debris in or near the greenhouse is a definite no-no. When removing infected plants from the greenhouse they should be bagged on the spot and not dragged past and infect other plants. Thorough clean-up and disinfection between crops is essential for the health of the new crop.
Culture control options
When working, start with crops of young and clean plants, then move on to the older possibly infected plants.
How the crop is worked can be important to help reduce the spread of disease. That is, should staff use fingers, knives, secateurs, and how do they keep them clean? Great care needs to be taken if the crop has a highly contagious disease such as bacterial canker.
When assessing the results of monitoring, if you think a spray is necessary, decide whether to spot spray or to do the whole greenhouse. Use the softest chemical to do the job. Follow the label, which often suggests that you spray a second time slightly later to catch those pests that have hatched since the original spraying. To reduce the risk of the build-up of pesticide resistance, the next time you spray for that pest it should be with a product from a different chemical group (not merely a different trade name).
The range of biological agents such as predatory insects is steadily increasing and their use becoming more widespread. Suppliers can provide much detail upon how to use them and which chemicals can be safely used with them, and which cannot. One aspect of this that can cause problems, is if you get young plants from a propagator. You need to be aware of their spray progam because the residual may kill off your beneficials.
Monitoring is essential so that the numbers of beneficials are adequate to do the job. Too late to be introduced and they can be overwhelmed by the pests. To help in this regard, it is sometimes possible to keep a population of predators within the greenhouse through the use of ‘banker plants’. These are of two types: one provides pollen to feed them until needed; the other hosts a population of a similar but harmless pest to keep them fed until the real pest arrives. Ω
PH&G March 2016 / Issue 165