– Amaryllis Worm / Lily Borer
– Powdery Mildew
– Pumpkin Fly
– Blackspot on Roses
– Coddling Moth
AMARYLLIS WORM or LILY BORER
November means that it’s time to keep a eye out for the dreaded “amaryllis worm”. These Lily borers are yellow and black worms that rapidly eat the leaves and bore down into bulbs of plants such as the amaryllis, agapanthus and clivias. They multiply rapidly and do great harm – not only to the leaves, but also to the bulb and its embryo buds. Once spotted, be sure to take action as soon as possible. It is absolutely necessary to spray a suitable systemic insecticide to rid the bulbs of these pests. Usually 3 repeat applications are required when a serious infestation such as this is evident. Be sure to stop by Blackwood’s Home of Gardening for expert advice.
The wet weather means that it’s also time to watch out for fungal diseases like powdery mildew on cucurbits (the pumpkin family). Powdery mildew is one of the most common and easily recognized plant diseases. Almost no type of plant is immune, however some are more susceptible than others. As the name implies, powdery mildew looks like powdery splotches of white or gray, on the leaves and stems of plants. There are actually several types of powdery mildew fungi, but they all look basically the same. You may not notice a problem until the top surfaces of the leaves turn powdery, but powdery mildew can also affect the lower leaf surface, stems, flowers, buds and even the fruit. Although powdery mildew is unattractive, it is rarely fatal. However it does stress the plant and severe or repetitive infections will weaken the plant. If enough of the leaf surface becomes covered with powdery mildew, photosynthesis is impaired. Infected leaves often fall prematurely. This can be a particular problem on edible crops, since insufficient photosynthesis can diminish the flavor of the fruit or vegetable. If buds become infected, they may not open and mature at all.
Once your plants are infected,
- Remove and destroy all infected plant parts
- Improve air circulation by thinning and pruning
- Don’t fertilized until the problem is corrected. Powdery mildew favors young, succulent growth
- Don’t water plants from above
- Apply a fungicide: There are many fungicides available. Check the label to be sure they are safe and effective on the type of plant that is infected. Most fungicides will need repeat applications every 7 – 14 days, for continuous protection. Always follow the label instructions for both application and waiting period before harvest.
Curcubits (the pumpkin family) are the principal hosts for the pumpkin fly. Ensure that you put bait out for these. Pumpkin flies lay clusters of eggs into the developing fruit. When these hatch, the young maggots start eating the flesh, destroying the fruit, causing it to be aborted, or making unsightly hollows in the fruit. When the maggots mature, they leave the fruit and fall to the ground. Here, they bring head and posterior together, then release, ‘springing’ to a new site, where they pupate in the soil.
The life cycle can last as little as three weeks under favourable conditions. The initial ‘sting’ in the fruit leaves a puncture mark surrounded by a sunken area. In baby marrows, this makes the fruit unsightly. The degree of damage to pumpkins and butternuts depends on the fruit’s stage of development. If the fly ‘stings’ butternuts and pumpkins at a fairly advanced stage, it may simply make a lesion that degrades the fruit. When young fruit are attacked, they usually turn yellow and stop growing.
It’s possible to stop the pumpkin fly problem in its tracks by killing off the early hatchlings that made it through winter. And if you bait the crop just before flowering as well as during early flowering, you could slow down the pest dramatically.
BLACKSPOT ON ROSES
Blackspot is a nasty fungus that manifests itself on rose bushes as black spots on leaves, progressing to black spots fringed with yellow rings on both sides of the leaves. As they develop, the spots enlarge. Eventually, as the disease spreads, the entire leaves will go from green to yellow and then drop to the ground. With time, the entire rose bush may become defoliated. Leaves less than two weeks old are the most susceptible to this disease. Defoliation brought on by blackspot is a problem during November, as it is at it’s worst during this wet, humid weather. It needs about 7 hours of these conditions to germinate and then symptoms will begin to appear on rose foliage within three to ten days. From then on spores are produced every three weeks. If unchecked, blackspot can affect the entire rose garden leaving an unattractive appearance of many ‘bare-naked’ plants. But it can be avoided with some preventative measures such as a good systemic fungicide, a keen eye and diligence.
Once you have discovered that your rose bushes are infected it is best to prune off the damaged parts of the plant and gather the diseased foliage. Dispose of this diseased material in bags or burn it. Do not add to the composter, as the fungus shall only return to haunt you when you recycle the soil back into the garden. It is vital to do an end of season cleanup so the spores will have no where to hide over winter. After having removed the diseased parts from your rose bushes it is necessary to apply a preventative formula to minimize further attack.
If you are growing apples or pears, it’s also time to spray them for coddling moth. The coddling moth lays eggs singly, generally on the upper surface of leaves, or on the fruit. Egg hatch occurs in 6-20 days depending on prevailing temperatures. Newly hatched larvae seek fruit, which they enter to feed and develop. Larvae discard their first bites of epidermis, then either feed beneath the surface or tunnel directly to the center of the fruit. They deliberately feed on the seeds of the fruit. As larval development nears completion, they eat out an exit tunnel, which they plug with frass. The larvae then leave the fruit and construct thick silken cocoons under loose bark or in some other protected spot.
Predators and parasites feed on coddling moth, but these natural enemies cannot keep this pest from reaching damaging levels.
November also means that it’s time to check for whitefly – they love the heat of summer and remember when spraying, try and get the spray in from under the plant as the little flies sit underneath the leaves. These are sap-sucking insects that are often found in thick crowds on the undersides of leaves. When infested plants are disturbed, great clouds of the winged adults fly into the air. Both nymphs and adults damage plants by sucking the juices from new growth causing stunted growth, leaf yellowing and reduced yields. Plants become weak and susceptible to disease. Like aphids, whiteflies secrete honeydew, so leaves maybe sticky or covered with a black sooty mold. They are also responsible for transmitting several plant viruses.
Host plants include more than 250 ornamental and vegetable plants. Citrus, squash, cucumber, beans, geranium, poinsettia, potato, cucumber, grape, tomato and hibiscus are commonly infested.