Winter Moth Update

Here is a new Pest Alert from Heather Faubert with URI Cooperative Extension.

To Fruit Growers:
Now is a good time to check your blueberry buds and see how well your insecticide applications worked to control winter moth caterpillars. I’m seeing mixed results – some applications worked well and in other locations, repeat spraying has been necessary.

Blueberry plants with frass, dead caterpillars and a dead caterpillar. You may need to tease open buds a little to look inside to see frass or caterpillars.

Blueberry buds with caterpillars, frass and dead caterpillars. Tease open buds to see frass or caterpillars inside.

 

Look now for insect frass (droppings) and caterpillars. The caterpillars are still rather hard to see, so if you find more than a little bit of frass in blueberry buds, consider applying an insecticide again. Caterpillars are about mid-way through their life cycle. Starting soon, as caterpillars become larger, people will start noticing holes in leaves and frass dropping from trees.

DiPel or other Bt insecticides should be effective now and kills only caterpillars so there is no harm to bees. Since it is before bloom, other labeled insecticides can still be used.

If you have questions, bring sample buds to the RI Fruit Growers Association Twilight Meeting for small fruit growers at Sweet Berry Farm, 915 Mitchell’s Lane, Middletown on May 13 at 5:30 pm.

Meeting topics will include winter moth, spotted wing drosophila, blueberry and raspberry pruning. Speakers will be Sonia Schloemann from UMass and Heather Faubert from URI. Meeting cost: free for RIFGA members, $20 for non-members. Membership is $40 per farm.

Heather

Winter Moth Update

Here is a new Pest Alert from Heather Faubert with URI Cooperative Extension.

frass & larvae in apple blossom

frass & larvae in apple blossom

To Fruit Growers:

Eggs on monitored trees in other towns have hatched, It is too late now, in most areas, to spray an insecticide to stop winter moth caterpillars from entering buds, except maybe in cooler areas, such as Little Compton.

On April 23 I observed many winter moth caterpillars inside of unsprayed apple and pear flower buds. Once caterpillars are inside buds they are protected from insecticide until buds open. For apple trees, the next opportunity to apply an effective insecticide is at Pink, when flower buds have separated, but before blossoms open.

frass in blueberry bud

frass in blueberry bud

This week I intend to pry open many sprayed apple and blueberry buds to see if winter moth caterpillars are inside. When looking for winter moth caterpillars, mostly what you look for is the caterpillar frass – caterpillar poop. When caterpillars are small they can be very difficult to find. Frass in blueberry buds is black, but frass in apple buds tends to be brown or orange-brown.

larva with frass in blueberry bud

larva with frass in blueberry bud

Once the blossoms are open, check for evidence of sufficient larva to warrant treatment. If needed, the Organic Materials Review Institute (ORMI) has approved the use of DiPel or another Bt (Bacillis thuringiensis) as well as Entrust and Neemix.

Winter moth caterpillars

Heather Faubert of URI Extension

Heather Faubert of URI Extension

Here is a Pest Alert from Heather Faubert, URI Cooperative Extension

To Fruit Growers:

Winter moth caterpillars started hatching on Sunday, April 19th. Many blueberry and apple growers sprayed insecticide over the weekend, protecting flower buds from winter moths. Today we are getting heavy rain and there are still many winter moth eggs to hatch. Will insecticide applied over the weekend last through all winter moth eggs hatching? Good question! Rule of thumb tells us that pesticides last for up to 2 inches of rain. Following this rule, winter moth caterpillars should continue to be killed after today’s rain. I admit I am worried about apples and blueberries having sufficient insecticide coverage after today, especially in areas with high populations of winter moths.

So what to do – if you haven’t sprayed yet, I suggest you apply an insecticide Tuesday or Wednesday. If you did already spray and you know you had a high winter moth population last year, consider applying another insecticide Tuesday or Wednesday. If you don’t think you have a lot of winter moths – if you didn’t have problems last year – I think you don’t need to spray.

Winter Moth & LarveaOnce winter moth caterpillars are inside buds, you can’t control them with an insecticide until close to bloom – probably in early May. When flower buds expand but before blossoms open (apple and blueberry ‘pink’ bud stage), winter moth caterpillars move around and are once again susceptible to insecticide applications. At this time, organic approved Bt insecticides such as DiPel DF or Agree WC are also effective controlling winter moth caterpillars. Other organic treatment options include Entrust SC Naturalyte Insecticide and Neemix.

The way to determine if a pre-bloom spray is needed is by inspecting your flower buds starting in about one week (April 27). You will need to dissect buds and see if there are winter moth caterpillars inside.

Send questions to Heather Faubert, URI Cooperative Extension via email to hhf@uri.edu or call the office at 401-874-2967 or Heather’s cell phone at 401-256-7438.