This month I would like to look at why vineyards attract the pest animals they do.  Hopefully, this will inspire some vineyard management practices that may make your next season a little easier with regard to vertebrate pest control.

First of all, rodents.  Rodents are drawn to your vineyard because of abundant vegetation.  This vegetation provides food, shelter from heat and cool extremes, and a hiding place as well as a predictable source of water.  For burrowing rodents such as gophers, ground squirrels and rabbits, cultivated or disked vineyard floors provide an abundance of stored food that was previously unavailable, as well as easy digging.

The winter time is when burrowing rodents are inconspicuous, spending most of their time underground maintaining food caches and building fat reserves.  This is in preparation for overwintering and the upcoming breeding season. The long and the short of it is, if you have these pests now, you’re going to have a lot more of them come spring time.

On the other hand, if you can successfully employ some of the available control measures now, you are really hitting the population on a larger scale.  Unfortunately, traditional methods such as baiting have limited effectiveness this time of year because of the reduced activity level of the animals.  This is when trapping becomes a viable option.  As a grower, you are more likely to have the time to undertake a trapping program in December or January than you are in say, April.

You may also take another look at the weed control and cover crop techniques you are using.  If you minimize the available vegetation you will minimize the rodent population as well.  This also goes for the insect and bird population as they are all tied into the same ecosystem.

Speaking of birds, what about them in the winter time.  Well, there much to talk about.  For the grape grower, bird damage is largely dependent on the seasonal weather changes which influence the migratory patterns of the birds.  In California, there is an ever increasing population of resident starlings to contend with.  But their habits change in the winter time, possibly giving some growers a false sense of security due to their absence.  

Finches or linnets can be somewhat controlled with “off season” trapping programs.  The same principal as rodent control applies here.  If you have a permit for cage trapping linnets (such as a Modified Australian Crow trap) use it to your advantage this time of year.  If you are able to reduce the supply of breeding birds come spring time, you’ll have less to deal with during the growing season and heading into harvest.

Next month we’ll begin to review the latest developments in chemical control and trapping for rodent control.