All entries for August 2013

Rothamsted suction trap captures for week ending 4th August

Writing about web page http://www.rothamsted.ac.uk/insect-survey/Bulletins/2013WebBulletin15.pdf

Trap data for the week ending 4th August have been released:

Cabbage aphid - numbers generally lower than the previous week but highest at Writtle and Hereford

Peach-potato aphid - numbers generally lower than the previous week but highest at Broom's Barn

Potato aphid - numbers lower than the previous week but highest at Dundee and Elgin

Currant-lettuce aphid - only one captured - at Rothamsted

Willow-carrot aphid - numbers lower than the previous week but highest at Dundee

Black bean aphid - numbers lower than the previous week but highest at Broom's Barn

Rosemary Collier : 11 Aug 2013 21:30 |  Comments (0) |  Close comments |  Report a problem

Carrot fly and hot weather

We would have expected the numbers of carrot fly captured on our traps at Wellesbourne to have increased again by now - to signify the start of the second generation. However, numbers remain low. This may be due to pupal aestivation because soil temperatures have been high for some time.

In some experiments we did many years ago, newly-formed carrot fly pupae were exposed to temperatures of 22-30^oC for various 5-10 day periods during pupal development. Exposure to temperatures of 24^oC and 26^oC caused some, and exposure to 28^oC and 30^oC caused all, of the pupae to delay development. Development was resumend when the temperature was lowered. Pupae were sensitive to high temperatures only for approximately 4-10 days after pupation.

Carrot fly eggs/newly-hatched larvae are also susceptible to hot/dry conditions and mortality is increased. We do not know how much irrigation would reduce the effects of hot weather.

Carrot fly pupae

Rosemary Collier : 09 Aug 2013 11:11 |  Comments (0) |  Close comments |  Report a problem

Cutworms

It seems that first generation turnip moths (cutworms) have now stopped flying at Wellesbourne. We captured male moths in pheromone traps between 13th June and 25th July - and this is at least 2 weeks later than 'normal'. It appears, therefore, that no more first generation eggs will be laid. However, there is still a risk from the larvae of eggs laid earlier on, and the cutworm forecast will continue to be updated until all these larvae are predicted to have reached the third instar, which will be towards the end of August.

Although it has been hot for several weeks, according to the cutworm model, the sporadic bursts of rainfall have reduced the risk of damage. However, in some locations there may have been insufficent rainfall to completely reduce the risk from batches of eggs that hatched in late June-early July and it would be interesting to hear whether there have been any incidents of cutworm damage?

Rosemary Collier : 09 Aug 2013 10:56 |  Comments (0) |  Close comments |  Report a problem

Update from Wellesbourne

Yesterday we found:

• 12 carrot flies (3 traps) - so still no increase in numbers to signal the start of the second generation. Pupal aestivation......?
• 6 cabbage root fly eggs on 15 plants (second generation appears to be over)
• No silver Y moths - but they are definitely around in quite high numbers at present as we are catching them in a light trap locally
• 15 bean seed flies, 33 pollen beetles, 6 flea beetles (3 traps)
• Butterfly numbers have increased - 19 small white and 9 large white in 3 traps
• 3 diamond-back moth in 3 traps - and reports of activity elsewhere in the country

Rosemary Collier : 09 Aug 2013 10:45 |  Comments (0) |  Close comments |  Report a problem

Update from Wellesbourne

Monday's sampling produced the follwoing counts:

• 12 carrot flies (3 traps) - the second generation appears to be even more delayed than predicted - perhaps there has been some significant pupal aestivation due to the high soil temperatures recently.
• 12 cabbage root fly eggs (15 plants) - probably signals the end of the second generation.
• 11 bean seed flies (3 traps)
• 29 pollen beetles, 9 flea beetles, 7 small white butterflies, 4 large white butterflies (3 traps)
• 18 silver Y moths (2 traps) - suggesting a recent influx of migrants

Rosemary Collier : 07 Aug 2013 13:37 |  Comments (0) |  Close comments |  Report a problem

Update from Rothamsted Insect Survey

The latest information on aphid captures by the Rothamsted Insect Survey has just been released. bulletin_14_2013.pdf

More detailed information on the pest aphids of vegetable crops is here. aphid_news20130802.pdf

In summary:

• Peach–potato aphid suction trap numbers are increasing in England, but remain scarce in Scottish samples. However, the number of potato aphids in Scotland increased markedly this bulletin week. 
• A total of 146 suction trap peach–potato aphids have been tested for insecticide resistance so far this year, and 140 have tested positive for MACE (these are resistant to pirimicarb) and 137 also tested positive for super Kdr (these are resistant to pyrethroids). 
• Yellow water trays placed by Broom’s Barn at twenty eight sites in sugar beet areas caught 19 peach–potato aphids and no potato aphids during the period 24/7–30/7, roughly the same as the previous week. 
• Pea and cabbage aphid numbers are increasing in central and southern England.
• The migration of willow–carrot aphid is now all but complete, with just some late stragglers north of the border.
• Currant–lettuce aphids were caught at four sites, and accumulated numbers are above the ten year means at four sites in central and southern England.

Rosemary Collier : 02 Aug 2013 17:21 |  Comments (0) |  Close comments |  Report a problem

Update from Wellesbourne

Yesterday we found:

• 10 carrot flies (3 traps)
• 88 cabbage root fly eggs (15 plants)
• 17 bean seed flies (3 traps)
• 7 silver Y moths (2 traps)
• 1 diamond-back moth (1 trap)
• 18 pollen beetles, 7 flea beetles (3 traps)

Rosemary Collier : 02 Aug 2013 08:46 |  Comments (0) |  Close comments |  Report a problem