Integrated Pest Management (IPM)

Those of us who work in industries that use chemicals have a responsibility to try and reduce that use any way we can ! IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. It's common in the nursery industry to have a kneejerk reaction when encountering a pest or disease. I prefer to ask, "how big a problem is this ?" . Bringing out the "big guns" and using chemical insecticides and fungicides at the first sign of a problem may well do more damage to the overall health of your crops by killing non-target beneficial organisms. Working to enhance the overall health of the plants increases their natural capacity to resist attack and a few losses for this greater gain is well worth it.

Damping off is the biggest propagation challenge. It's when the young seedling keels over for no apparent reason and is due to attacks from a range fungal organisms. The best defense is air flow. A constantly damp, still environment is detrimental to soft young shoots so keep your seedling trays up off the ground where possible and avoid over watering. Overwatering often does a lot more harm than under-watering. Think about what happens in nature....a good soak then nothing for while, its not a regular light sprinkle which is possibly the worst approach resulting in weak shallow roots and the perfect environment for fungi. The liverwort in the seed tray in this image is a dead give away that it's too damp as liverwort needs plenty water to colonise.

There are some good preventative measures to reduce fungal attacks. Among the suite of non-chemical agents is a product called Trichodry that contains Trichoderma. Thricoderma are naturally occurring fungi that protect by outcompeting the bad ones that would otherwise grow. They not only parasitize and feed on bad pathogenic fungi but they enhance healthy root growth. What more could you want ! A spray form combined with Plant Soap which acts as a food source for the Trichoderma can be used regularly at the most vulnerable stages of growth. They're wonderful organisms but remember, chemical fungicides will kill the good fungus so commit to prevention and the environment ! For info on Trichoprotection see McHort Bio-control Leaflet

Powdery mildew is one of the more common and easy to spot fungi resulting from high humidity and lack of air flow and is a good indication that your growing environment needs adjustment. It's rarely fatal though it can disfigure young leaves if the infection is bad enough. Dilute baking soda spray, Excel or other mineral oils, or dilute milk spray combined with moving the plants into the sun and breeze will all reduce the infection.

Aphids can reproduce at a staggering rate simply by popping out millions of clones asexually so the trick is to not let the numbers build up ! Regular sprays alternating between Neem Oil (an extract of the Neem tree) and Excel Oil (a mineral oil that blocks the insects breathing holes) usually does the trick. You'll find that aphids will attack the weakest plants and often good strong growing plants will not be too badly affected so if you're having lots of problems with aphids it might be a sign that you need look at the general health of your growing environment including the growing medium.

Root mealy bug can be a very detrimental critter as it chews away at the roots of plants unseen until the plant shows signs of decline. If you can't work out why your plants are looking sickly upturn the container and lift it off to see the roots, mealy is instantly obvious by the fuzzy white patches made by their waxy secretions. If its only affecting a few plants you can remove all the soil and repot in fresh soil. Alternatively mix Neem granules into your potting mix as a deterrent. Another approach is increasing the numbers of natural predators like Hypoaspis mites which can be purchased to sprinkle over your crops. See McHort Bio-control Leaflet  or Bioforce for information and purchase of Hypoapsis mites aka Hypo-Mite™

Leaf mealy bug has the same fuzzy white look as root mealy and commonly attacks young cabbage trees but is quite easy to control with a spray of Excel Oil or a solution of methylated spirits and water mixed in equal parts and dabbed on to the bugs with a brush.

Photo by Tony Wills

Sciarid fly or fungus gnats can be a major nursery pest but most of the time its when the young plants are already under stress and the flies are around in very large numbers. They feed on algae and decaying plant matter so its good to avoid the build up of these as the maggots will chew at the small root hairs of your plants too. The adults look like tiny sand flies  and they flick their wings as they walk around. The maggots are also eaten by Hypoapsis mites so keeping these numbers up is always a good thing. The adult flies can be knocked out of the air by spraying Plant Soap that gums up their wings but they quickly arrive again when their numbers are high. I tend to just accept whatever losses might result and prick out some extras to cover it as the alternative of using a toxic insecticide drench seems a little heavy handed in relation to the actual number of seedlings affected. If you are only growing small numbers of plants the best defence is wonderfully simple, just cover the surface of the growing medium with small to medium sized sharp grit and this seems to deter them. Its when the surface of your growing medium is constantly wet that they really get excited !

Liverwort (Marchantia) is one of the worst nursery pests there is. It smothers the young seedlings faster than they can outgrow it and spreads at a rate of knots !  Its success is due to the same strategy as aphids, the ability to fruit and to clone. The little gemma cups on the thallus are full of tiny vegetative propagules (gemules) that splash out in the rain and start growing where they land. Once the seedlings are big enough and are moved outside the sun usually takes care of it but in the shade house it is in its element ! Thankfully the solution is simple....baking soda. Sprinkled on lightly like icing sugar on a cake it kills liverwort, hornwort and mosses within about 24 hours ! Its really important though to water in after application to get the process going but also to get the baking soda off the young seedlings as it will have a detrimental affect if left to sit on the leaves. Use this method at your own risk as it can kill softer young seedlings and I always trial it on a small patch if using it on a particular plant for the first time. If your seed trays are on the ground liverwort is a much greater problem as its propagules are splashed from the ground onto the seed trays so bear this in mind when designing a nursery.


left: Liverwort after treatment with baking soda

In general, even though the seedlings need to be kept watered, the surrounding environment should be kept relatively dry and free of organic matter which will reduce the dampness and the spread of moss, algae and liverwort and reduce your pest and disease problem significantly .  A 50:50 mix of plain white vinegar and water is a great non toxic way to kill all of these (though baking soda definitely is number one for liverwort). The vinegar can be used as a spray or scrubbed on to problem areas. 

Its tempting to overwater young plants when you are worried about them drying out but even when the surface of the growing medium is dry there can still be plenty of water for the roots lower down. When first pricked out make sure they are watered regularly but in a couple of weeks they will be settling in and you can ease off a little on the daily watering.