May 08, 2008

Zahrah Nasir shares some tips to keep insects and bugs from the garden

Q I am in urgent need of help. My roses, both potted and others have been invaded by small green insects. Similar things have also made new leaves on my two orange trees curl in to round circles. Last year I lost my six-year-old jacaranda tree to thick, thumb nail size white insects. This time they have targeted my 25-year-old kachnar which I do not want to lose. I live in Kohat. Please help.

A Phew! You have definitely been invaded by a horde of nasties. Let’s look at them in order. First your roses: some form of aphid I expect and I would advise that you thoroughly spray them with warm soapy water, remembering to wash the undersides of the leaves with this not just the top surface. Try to use pure soap if possible. Spray in an evening after the sun is off the plants to avoid any leaf burn. Once you have done this, make up a good size dose of garlic water by boiling a quarter kilo fresh garlic, skin included, in one litre of water (multiplying this as you deem necessary), let it stand overnight, strain through a fine muslin cloth and, again in the evening, spray your roses with this as this should knock out any remaining aphids.

Repeat the garlic water spray at weekly intervals if possible in order to prevent re-infestation or use at the first sign of any beasties putting in an appearance. Next your orange trees: leafhoppers are possibly the problem here and, unfortunately, I do not know of any organic method of control which is available in Pakistan.

Finally, your much loved kachnar: this sounds like a classic invasion of scale insects, very nasty things with a hard waxy coating that repels almost anything you spray on them so the answer here is to quite simply suffocate them to death! Do this by spraying them with either olive oil or some other very good quality cooking oil. You will probably need someone to climb your tree to do this and make sure to tell them to spray every insect in sight, above and below leaves, yet not to absolutely saturate the tree, or themselves, in the process.

Q I am a student of agricultural entomology at the University of Agriculture in Faisalabad and recently read your article on ‘aromatic artemisia’ which appeared in this magazine in December 2006 and which is also on the Internet. I want to test the insecticidal properties of this plant for use against trogoderma granarium (khapra beetle) for the research of my M. Phil degree. Can you kindly provide me with approximately one kg of the dried plant material from which to extract the necessary ingredients?

A As you will be aware from the above mentioned article, there are literally dozens of species of artemisia which are indigenous to Pakistan but, at a guess, I suspect you are looking for a supply of ‘artemisia absynthium’ known as ‘wormwood’ in English. This plant is reputedly beneficial in keeping slugs and snails out of gardens when planted around the boundary. Other members of this widespread species are considered to have a similar effect and I am still experimenting with them in my own garden.

Whilst your research subject is laudable and I wish you all the best with this, I wonder if you realise just how vast a quantity of fresh plant material is required in order to produce a kilo of the dried one? This would mean completely denuding my garden of every plant I have carefully cultivated over the years and I am not prepared to do this. I suggest that you venture out in to the rural areas around Faisalabad and search for artemisia plants to harvest, with permission from the appropriate landholders of course, from this locality. As you are not sure what the plants actually look like, perhaps you can arrange to take someone from the botanical department with you to help out.

Q Ants and ant hills keep appearing in our lawn. What is the best way to get rid of them?

A There are three possible solutions to this. 1. Keep on pouring kettles full of boiling water down the entrances to the ants’ nests, you will have to scrape away the anthills first to expose them. 2. Make up a bucketful of ‘pinky’ (potassium permanganate) solution and pour this down the entrance holes during bright sunlight and the ants will race out and burn up when the sun strikes them. 3. Scatter derris dust all around and in to the entrance holes every time you see any ant activity at all.

Q I have five alistonia trees outside my house. Recently lots of flat white two mm x two mm bugs have infested the trees and disturb the house also. We have sprayed to no avail. What do you suggest?

A Presumably you are referring to lagerstroemia indica (crepe myrtle or Indian lilac) trees as I cannot find any reference to ‘alistonia’ ones in my horticultural library. However, irrespective of the actual tree species, the bugs are some kind of scale insect and for their treatment please refer to the answer to the first question in this week’s column.

Q I have read a lot of good things about horticultural oil but no nursery or garden shop in Islamabad has heard of it. Where can I find it? Can I use cooking oil as horticultural oil?

A Horticultural oil, sometimes also called ‘white oil’ is a very high grade, pure, organic oil without any harmful chemicals included in the mix. I have never been able to locate a source in Pakistan and it is perfectly all right to use high grade olive oil, or similar top quality cooking oil, in its place.

Q Can you please give me tips to grow grass in my garden? Also, what are some names of evergreen plants suitable for growing in Karachi and which are easily available.

A Regular food, water and weeding should help you to maintain a reasonable lawn in the harsh climatic conditions of Karachi. There are so many species of evergreen plants suitable for cultivation in the city that it is hard to know where to begin and, as you haven’t mentioned the type of evergreen plants you want e.g. trees, shrubs, climbers, low growing or rockery plants, I suggest that the best thing to do is to visit a few of the local nurseries, explain exactly what you want to the people in charge and take it from there.


Send your gardening queries to zahrahnasir@hotmail.com.  Answers to selected questions will appear in a future issue of ‘The Review’. This will take time. The writer will not respond directly by e-mail.