Gardeners’ queries

Press, Volume CXVI, Issue 34129, 15 April 1976, Page 10

Gardeners’ queries

What is wrong with my < apple trees, the leaves of ■ which have all gone the colour j of the samples and then fallen off? They got a spray of lime sulphur about two or three times this season, with a good spray of oil during the winter. I have a glasshouse and wondered if I just put a propriety fumigation on this year instead of changing the soil- I changed the soil two years ago. — W.F. (Christchurch). The problem has been caused bv the presence of mites which Feed on the leaf surface causing i bronzy discolouration. Leaf fall' ?an occur when the mite infesta-i Lion is very heavy and particu- . larly if conditions are at the: »ame time verv hot and dry. I Winter oil. although of great benefit at the time of application a ill not prevent reinfestation luring the following months;) ime sulphur has only a very imited role in the control of n tes and its use is not recommended once the leaves are fully ipen on fruiting subjects unless perhaps in ton junction with colloidal sulnhur. The specific T»i«icide kelthane is recommended. two applications 10 days ipart trenerally being required n cases of severe infestation, so I sterilisation by chemical means can give verv good results providing the 10b is carried out exactly according to recommcn-, iations. It is absolutely essential j o ensure that the soil is I thorough! v aerated before any I subsequent plantings. What is the best method of sowing avocado seed, and can |

I they be grown outside here? • —R.W. (Christchurch). j There are several methods of germinating avocado but just which is the best is not known. One of the most common ones is to suspend the seed above a container full of water. The seed should be placed narrow end down but this position is not critical and the seed will germinate satisfactorily if laid on its side. Damp moss wrapped around the seed can also be used to start it into growth. A warm place is best. Avocados are intolerant of frosts above a few ; degrees and locally can be regarded as little more than potted foliage plants unless the, house is on the hills or bays [around Christchurch. Could you give me some suggestions for native shrubs that do not need frost protection but which will tolerate hot, dry conditions. — H.W. (Darfield). Native trees and shrubs tolerant to frost and hot. dry conditions include the following: hebes. flaxes. corokias. pittosporums. sophoras, dianella. plagianthus, most species and forms of hoherias. olearias, cassinias and cordylines. Could you please identify this very small off-white insect and tell me something of I life cycle? It has become extremely prevalent during 1 recent months on a variety of plants. It seems to like beans for breedina. It explodes into j the air if disturbed. What can be used to control it? — M.M. (Sumner). The pest is white fly, often regarded as a glasshouse problem. This year it appears to have thrived. Its mode of feeding is bv sucking the plant juices. Control is becoming more difficult. particular! v because there are three distinct stages in the: life cycle of this pest. The application of maldison at three to four-dav intervals until the problem has been controlled has, been suggested. Thoroughness of application is very necessary to ensure that the adults controlled as maldison is inefTcrt”aj against the voun? nymphs. Experiments using bloat oil at the rate of one per cent of the | sorav mixture is ar»parentlvl showing good resu’ts: it can be! applied with maldison. In this way a’l stages of '«-bjte fl'‘ are controlled to come degree, ’’’here ts the possibility of damage to ♦he o’ant from this control and therefore care is needed. Because nf th" number of ''<>eds host tho vbite fßes" should be completely- cleared from the vicinitv of susceptible