Topic: Wireworms

[janebb]

I have a fairly new allotment which had been uncultivated for about a year.  It was very grassy and  full of old potatoes which had been left behind by the previous allotmenter. I have also been finding wireworms.

I don't really want to use chemicals if I can avoid it.  When digging (in the area I intend to use for potatoes) I found about a dozen wireworms. The area was about 6 foot by 12.   I cut the wireworms I found in half and left them to the birds to eat. 

Would this number of wireworms in this area count as a serious infestation which would affect the potatoes? Will picking them out by hand suffice or will I have to use chemicals if I want to grow potatoes this year?

[simon404]

There's some answers here (http://www.dgsgardening.btinternet.co.uk/wireworm.htm) but personally I wouldn't call what you've got a serious infestation for a new plot. Just keep killing them as you find them.  :)

[Marianne]

Hi jane,

Found the following for you.  Hope it helps a little !
 ;) :)

To control wireworms, remove previous crop residue to reduce alternative food sources for larvae. Because wireworms are attracted to grass cover crops, delay cover-crop planting until fall, and leave fields intended for sweet potatoes fallow in the summer. Control weeds adjacent to and within the field before and after planting. Deep plowing will also kill wireworm larvae. Because wireworms are inactive in the spring, plant fields as early as possible. As recommended for whitefringed beetle, harvest sweet potatoes as early as possible because the potential for damage increases with time.

Evaluating new fields for the potential for wireworm problems is difficult, but you should check for wireworms when plowing and discing, and you can set wireworm bait stations in the fall or spring when soil temperatures are above 45 degrees F. Soil-sampling using a 6-inch post-hole digger gives a more accurate estimate than baiting, but it is labor intensive. Use the following procedure to make and set wireworm baits.

Mix a 1:1 combination of wheat:corn or wheat:oatmeal as bait.
Wrap a fist-sized amount of bait in a nylon stocking.
Bury the wrapped bait 4 to 6 inches deep, placing it in random locations in the field to obtain representative samples. Place more bait stations in suspected trouble spots, such as next to weedy or low areas. Use at least one bait per acre--the more stations, the better.
Mound the soil above the bait, and cover it with clear plastic if the soil is cool.
Mark the locations of the bait stations with flags.
Wait 7 to 10 days, and then dig up the bait stations and check for wireworms. Very loose treatment thresholds that have been developed for potatoes are as follows:

0 wireworms/bait = no control needed
 
 0.5 to 2.0 wireworms = moderate chance of damage
 
 3 to 4 wireworms = high chance of damage
 
 5 or more wireworms = do not plant
 


If observations of wireworms in the field indicate that chemical treatment is warranted, broadcast soil insecticide applications are more effective than banded applications. See the table at the end of this publication for recommended soil insecticides. Soil fumigation will also kill wireworms if they are in the treated soil profile, but wireworms can burrow in the soil below the chemical residue.


--------------------------------------------------------------------------------

[gavin]

Hi Janebb - I'd just squash 'em as I see them;  the ones you miss may well damage some potatoes this year, but will mature and fly off to lay eggs in the grass the prefer (so no problem next year :) ).

I've heard of people cutting a few potatoes in half, and burying them scattered around the potato bed; stick a twig in each piece of bait, and you can go back and check how many wireworm you're still getting - and move them somewhere more to YOUR liking ;D

All best - Gavin