Pests affecting your garden
1. Weeds.
Weeds may be few in variety in an arid region, but can be extremely abundant. The solution is to rigorously eradicate however tiny the weed appears to be. Most weeds are small plants (only 5 cm high in the 1st photo) that produce huge quantities of seeds, while still tiny plants (note tiny flowers in the enlargement = 2nd photo). Without rigorous sanitation of the weeds, your soil will become saturated with seeds and your problem will become difficult to bring back under control. In this situation, where the soil (for example, a pot) is covered in weeds, you should pick out the larger ones and then scrape the soil surface to knock over all the smaller ones, which can be dug in to the soil. But, you will have to repeat this several times as more seeds germinate. 2. Insects
a) Mealybugs.These are tiny plant sucking bugs (Homoptera), which are white and covered in waxy hairs. They are generally inactive, but if you knock them off the plant, they will show a surprising agility in clambering back up again. Can provide hours of innocent fun, if you have nothing better to do. The adult has wings, which is usually how they colonised the plant. However, they have a symbiotic relationship with ants, in which they provide excess plant sap to the ant in return for protection. The ants sometimes pick them up and carry them to a new plant. By sucking the plant sap, they cause stems to wilt and die and a heavy infestation can kill the plant. Because of the protecting ants (which keep off other predators), without you killing the mealybugs, their colony will rapidly increase to devastating levels. Some plants are more prone to attack than others and one of the worst is Hibiscus. But, Marigolds and Calendulas are also at risk. If seedlings have twisted leaves, you should turn over the leaves and carefully check for baby mealybugs. |
c) Scale insects are also plant bugs with a similar life to aphids and mealybugs. They are covered by a hard brown scale and so do not look like an insect. I have had them once attacking Hibiscus.
All 3 plant bugs can be treated with a systemic insecticide (which is absorbed by the plant leaves and so enters the plant sap). However, systemics are difficult to obtain here. Other remedies include spraying with dilute washing-up liquid. If there are only a few, I normally just squash them with my fingers (or between 2 leaves). Spraying is only necessary if you allow them to get out of control. |
e) Caterpillars. The main problem is the caterpillar of the silver-lined hawkmoth, which especially devastates Impatiens. It hides in the soil during the day and comes out at night. It is big and even 1 can cause great damage. It appears to be unkillable using any insecticide (I have tried many). At night, I chop it in half with scissors, but when it gets bad, I may be killing up to 100 per night. By that stage, your Impatiens have no future and you are wasting an hour every night.
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f) Spider mite. Not actually an insect, but an Arachnid. They are so tiny, that they are virtually invisible, but they cover the leaves with silk. They puncture the leaf cells one by one, so the leaf turns white and dies. Only a few plants seem to be at risk, but these include roses, Gardenias and especially Black-eyed Susy. You need to spray several times to get rid of them.
Photos shows spider mite on their web covering the underside of a flower of a miniature rose (so whole photo is only about 1 cm across). |
3. Snails. These may be very abundant, but since they are reluctant to climb, they are mainly a problem with seedlings. They can kill the seedling, if they eat through the stem. They also eat holes in the middle of leaves (unlike caterpillars, which eat from the edge of a leaf).
They eat at night and hide during the day. You can protect seedling using "slug pellets" (= metaldehyde), but when you are watering daily, these will not last long. Alternatively, search for the snails at night and squash them. |
4. Slugs. Since they do not climb, they are only a problem in flower beds, rather than pots. Because of their large size, they will rapidly devastate soft stemmed plants like petunias and Impatiens and so it is essential to eradicate them. Sprinkle slug pellets (metaldehyde) throughout the bed and repeat at least once 3 days later.
Like snails, they come out at night, but you will also see them crawling around leaving a slime trail early in the morning. |