Rebound Of Obliquebanded Leafroller In Tree Fruits

Obliquebanded leafroller populations have been relatively low in apples and cherries since the 2012 “crop loss” year, but recent trapline data suggests a possible rebound. We set a June 6, 2016, biofix for obliquebanded leafrollers at the Trevor Nichols Research Center in southwest Michigan, which was followed by two weeks of higher than normal adult flight. The first summer generation larvae are expected over the next week in southwest Michigan, and increasing thereafter. At the Northwest Michigan Horticulture Research Center, high numbers of adults were caught over the last week, and biofix was set as June 17.

 

Obliquebanded leafrollers are a threat to apples as a direct pest; the larvae feed on leaves and fruit in summer (July) and fruit in fall (September). In cherries, obliquebanded leafrollers do not feed much on fruit, but they can cause damage to cherry leaves, which can result in defoliation. The greater concern of obliquebanded leafrollers in cherries is the threat as a contamination pest, as they can be found in cherry tanks if present in trees at harvest. Despite the fact the larvae are easily visible either in the tank or at the processor, Michigan State University Extension advises growers to take precautionary measures to prevent these insects from infesting harvestable fruit and contaminating cherry tanks. Growers with problem orchards risk having tank-loads rejected at the processor if obliquebanded leafroller larvae are present.

 

Organophosphate-resistance was documented in obliquebanded leafrollers in Michigan apples in the early 2000s, and more recently in cherries in 2014. Pyrethroid and carbamate resistance have also been documented. However, there are several new insecticide chemistries that are efficacious against obliquebanded leafrollers labeled for apples and cherries. However, optimizing the timing of insecticide applications should take into account the residual activity, recommended degree-day target and pre-harvest intervals (see table below).

 

Growers should use traps to set a biofix by using MSU’s Enviro-weather system. After adult emergence, growers should begin monitoring for summer generation larvae. Growers should look at 10 fruit clusters and 10 terminals on five trees per orchard each week and should apply an insecticide if three larvae per tree are found.

 

For cherries, the insecticides we recommend for obliquebanded leafroller control at pre-harvest time are Delegate, Altacor, Belt, Exirel and Voliam flexi. For organic growers, we recommend Entrust. All of these insecticides have shown to be excellent against obliquebanded leafrollers. Because of their slower activity, Bt’s may not eliminate canopy infestation sufficiently to prevent contamination from a pre-harvest spray.