An insect infestation

Credit: stevendepolo

Q: For 3 years, we have had an infestation of cutworm on our “Purple Majesty”, but not on any of our other 12 Salvias. It is weird because two of the other Salvias we grow are of the guaranitica species – the ‘Argentine Skies’ and ‘Black and Blue’ varieties – and they are not effected.

Also, we started to grow Scarlet Runner Beans last year. Previously, we never had any white fly issues. Last year, we sprayed them with a biological compound that wouldn’t be harmful to plants or birds – it worked okay and the white flies weren’t bothering any other plants nearby. However, this year it has been horrific! Not only have the white flies destroyed our Scarlet Runner Beans, but all of the surrounding Salvias – ‘Black and Blue’, ‘Subrotunda’, ‘Coral Nymph’ and ‘Argentine Skies’.

Will the whitefly go away if we never grow Scarlet Runner Beans again in the future?

Thank You!

Sometimes insects will show a preferential liking to particular plants. If this is the case, either you have to monitor the situation and control accordingly, or not grow the plant(s) again. Always make sure the plant(s) are given the best growing conditions whenever possible – remember stressed plants are likely to be prey for insect(s) or disease(s).

In this case, check your plants regularly (at least twice a week) especially when you know the particular insect is active. For cutworms, handpicking at night – especially done early in the season – will usually minimize a lot of damage. Also, keep unnecessary weeds from overgrowing in your garden ,which may enhance overwintering cutworms.

As for whiteflies, the same principles apply, except handpicking plus spraying is next to impossible. Monitor the plants using “yellow sticky traps” to detect early whitefly populations so that control measures can be utilized. Good cleanup at the end of the season will help reduce overwintering population. Crop rotation is always beneficial.