Scale insects - Scale insects still remain mobile so if seen they can be sprayed with Chess WG at the higher off-label approval rate or SB Plant Invigorator for plants awaiting sale in the garden centre and all edible crops. Look at yew and bay trees, which seem to be most affected.
Leaf miners - Leaf miner can be found on some crops, particularly herbaceous perennials. Spray with Dynamec, Decis or Toppel 10 if seen.
Ceanothus and Viburnum - While I mentioned this last month, it is one of those problems that need repeated attention. These two subjects are being damaged by Phoma spp., which causes branches or tips to die back. Ensure a regular spray of either Scotts Octave or Signum to control the spread of the disease. In the case of Viburnum, do not trim the plants any later than July or you will remove the flower buds that are just starting to develop.
Left-over plants - Drench old/unsold plants that haven't had any vine- weevil control in the compost in September with Intercept 70WG or nematodes. Egg laying will occur any time now and the larvae start developing around six weeks after that.
Ash leaf gall - A reddish colour and leaf edge curl are symptoms of ash leaf gall sucker. Spray with Gyro or Hallmark with Zeon Technology if the symptoms start to show up. Use a wetting agent to get good pesticide penetration.
Escallonia - Don't forget to spray the foliage in July and August with a magnesium chelate such as Librel Liquid Mg. This will avoid the yellow lower leaves often seen on these plants mid-summer. They can be added to most pesticide sprays as a tank mix.
Pest and disease resistance - Resistance to pesticides by both pests and diseases does occur but there are a few simple rules that you can carry out to delay this natural process. Try to use a different pesticide group in rotation in your pest and disease control programmes. The UK Pesticide Guide (now online) is a valuable source of information on this subject and lists the product group under the active ingredient name. Check out your aphid, spider mite and whitefly programmes as these are the pests that seem to gain resistance more frequently. Botrytis, Septoria and downy mildew have also shown resistance to some fungicides and need care in the programme planning.