Fly Swatters

Intermittent rains over the past week covered most of the state, triggering apple maggot fly emergence in all monitored regions. Although captures on both baited and unbaited monitoring spheres have begun to build and we expect that the AMF risk period will be earlier than normal, few areas face an immediate threat of widespread AMF damage.

Fortunately, the very warm soil temperatures of June, followed by bouts of rainfall in early July, will likely impact the duration of AMF emergence as well as the timing. In addition to the expectation of a light AMF population this season, ideal soil conditions should inspire rapid eclosion; it is unlikely that AMF emergence will persist far into the season.

In a season such as this, growers are strongly encouraged to monitor the buildup of AMF within their orchards. In areas where AMF are active early, monitoring through use of sticky spheres offers early warning of building threat and allows proper timing of necessary treatments, while areas with light populations may not require regular coverage. Treatment thresholds based on trap captures have been developed over the course of decades of study in Massachusetts and New York. For unbaited sticky spheres, we recommend a cumulative treatment threshold of 2 AMF per trap. For spheres baited with fruit volatiles, a cumulative treatment threshold of 5 AMF per trap is recommended.

If these thresholds are reached, an application of Guthion or Imidan is advised. We do recommend use of a reduced rate of either material as the first AMF cover, as a half-rate controls early, moderate AMF populations quite well. In the past several years some growers have opted to use Lorsban for early-season AMF control; this material does offer some knockdown of low AMF populations (with simultaneous control of leafhopper and woolly aphid), but Guthion or Imidan will surely offer more reliable AMF control.

If an insecticide application is made, all flies should be removed from the monitoring spheres and accumulation of AMF toward the treatment threshold returns to zero. As emphasized in last week’s message, sticky spheres should be cleaned of all debris every 2-3 weeks, as the traps’ ability to capture AMF is reduced by ~25% for every week of exposure without maintenance.

Miner Heat Wave

The weather of early July has accelerated leafminer growth, and in the earlier-developing regions of the state, tissue feeding mines of the second generation have begun to appear, suggesting that it is getting late for any treatment targeting this season’s LM crop. If treatment is necessary and pending, then an application of Provado or SpinTor will still offer reasonable control of the second generation, as long as the majority of mines are still sap-feeding. Vydate and Lannate are also labeled options and, though not highly recommended, can offer control of more fully developed larval miners.

Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, Wes Autio, and Duane Greene except where other contributors are noted. Edited by Dan Cooley. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.