I had planned to talk about the increased number of pests in the garden due to our very temperate weather through March & April but this week as the weather is cooling down and we have had a light frost, the infestation of aphids and white cabbage moth in particular will soon disappear. Although there will still be a need to deal with the progeny from the cabbage moth over the next few weeks. So perhaps it would still be a good idea to discuss the management of these pesky caterpillars.
The eggs of the cabbage moth are usually laid on the underside of the leaves; are quite small and white. These can be removed by simply rubbing them off. The eggs hatching result in small green munching caterpillars. Just as the eggs can be removed by hand so can the caterpillars. Picking them of can be a very effective pest management strategy in a small garden but can be a time consuming task in a large garden or with a very heavy infestation. Exclusion fabrics and decoys can be effective deterrents but if you have a garden bed of eaten brassicas these strategies come a bit late.
If they are eating your plants at this stage, you will need to consider some type of organic chemical control. Dipel is a biological control that is highly effective against most species of caterpillars. It is a bacterial stomach poison for all caterpillars, which is mixed with water and sprayed onto foliage. It is ingested by the feeding caterpillar, which dies 3-5 days later. It is totally safe to beneficial insects, bees and mammals. The active ingredient Bacillus Thuringiensis is broken down by sunlight within a few days. In my view dipel is a very good option as it has very little impact on any other insects, One or two applications at this time of year should resolve the infestation as cabbage moths disappear in the cooler weather. We have been regularly using dipel during the summer as the hotter it got and stayed the more the moths thrived. At one point Helen got totally over them and ran briefly out into the garden wildly spraying from a can of fly spray... needless to say the moths thought that was a bit silly -! Not even one looked a little bit sick!
We have had some well needed rain across the region, although the amount appears to have been quite variable. Our garden had 7mm and while this might sound very little to those outside the region, here where we have been in drought for nearly a year (total rainfall 450mm since April 2017) any amount of rain is significant. It was wonderful to go into the garden after the overnight rain to see the soil dark and damp and the plants glowing. There is nothing more nourishing than some long awaited rain.
Bronwyn Richards has cared for animals and has been growing vegetables successfully all her adult life. She is principle gardener for Wynlen House Farm