Try moving the potato
crop to a new bed each year Tamara. Crop rotation helps with soil borne pests as well as not depleting the soil of specific nutrients each year, causing an imbalance. If you have grown potatoes
there in previous years, then the reason for your smaller crop may be that certain nutrients are in less proportions.
As for the bugs, if they are not damaging the actual potato
, then it doesn't really matter, especially if the foliage is dying off anyway. Beats spraying poison into your food producing soil, when the plant is already finished. potatoes
are a great crop to use on a newly dug bed, so if you have been planning a new garden, even if it is an ornamental garden, potatoes
are a great soil breaker and improver. Maybe plant them there next crop and put sweetcorn or cucurbits or something in the spud bed.