Summer leafroller control 2008: Gather the information needed to make a sound management decision
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EmailEditor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
A review of the 2008 season, thus far
The increased availability of several excellent leafroller control materials in the past several years has resulted in reduced obliquebanded leafroller pressure in Michigan apple orchards. Early season use of Rimon and Proclaim for codling moth control in 2007 provided excellent leafroller control. Many growers have incorporated two additional materials into their 2008 first generation codling moth management program, Altacor and Delegate. Both also provide excellent leafroller control at these early timings. Individuals that have survived these treatments are just beginning to pupate and emerge as adults. It is time to begin to gather the information needed to make sound decisions relative to summer generation obliquebanded leafroller control. Scouting for obliquebanded leafroller should include monitoring adult activity with pheromone traps and sampling for larvae. As larvae mature in late spring their presence is relatively easy to detect. Visual inspections for larvae or signs of their presence can save growers the cost of unnecessary, and often expensive, summertime insecticide applications. In other words, a key piece of information growers need in order to make a good economical decision for summer leafroller control is the extent to which larvae survived the early season treatment. With the excellent control provided by the new compounds registered in recent years, fewer and fewer overwintering larvae are surviving.
Monitoring with pheromone traps
Moth captures in pheromone traps provide valuable information to the scout and grower, including the establishment of biofix, but are not a reliable indicator of leafroller abundance or potential damage. Obliquebanded leafroller traps have a large active space, potentially catching moths that originate not only from within the trapped orchard, but also from neighboring or more distant orchards, and native habitats. Thus, high moth catches may or may not indicate that the orchard being monitored has a leafroller problem. On the other hand, very low catches of less than five per week strongly hint that obliquebanded leafroller is not a problem. In either case, assessing larval activity is highly recommended to determine if a treatment is warranted.
Assessing larval abundance to determine the need for control measures
Scouting orchards for surviving obliquebanded leafroller larvae in growing terminals is the best way to judge whether intervention in the summer is likely to be needed. Larvae are green with brown to black head capsules and are about 25 mm long when fully grown. Often, a scout will detect signs of leafroller activity rather than the actual larva. The name leafroller comes from the larva’s habit of rolling leaves to form a shelter. These feeding sites are most often found at the tips of growing shoots. Larvae will use silk webbing to attach two leaves or a leaf and fruit together to form a shelter. The presence of webbing is a good clue that leafrollers are around. Orchards in which less than two percent of the terminals were infested should be monitored in the summer, but controls may not be warranted. Inspect the undersides of leaves within the fruiting canopy, especially where fruit are clustered. Higher levels (less than two percent) of shoot infestation by overwintering larvae are cause for concern and control measures are likely needed to prevent fruit injury.
Table 1. Obliquebanded leafroller GDD model and insecticide timings
| DD° base 42 (Post Biofix) | Event | Action | |||
| Tight cluster | Majority of larvae have emerged from shelters | Examine fruit buds for larval activity | |||
| 0 DD° = biofix ("*"*"*"*"*"*"*"*~> | |||||
| Compound Trade Name | Chemical Class | Life-stage activity |
Optimal Spray Timing for OBLR | Residual Activity | Mite Flaring Potential |
| Guthion, Imidan | organophosphates | Larvae | Biofix + 400-450 DD | 10-14 days | L - M |
| Lannate, Sevin | Carbamates | Larvae | Biofix + 400-450 DD | 5-7 days | M - H |
| Asana, Warrior, Danitol, Decis | Pyrethroids | Larvae | Biofix + 400-450 DD | 7-10 days | H |
| Deliver, Dipel, Crymax | Bt’s | Larvae | Biofix + 450 DD | 5-7 days | L |
| Altacor | Anthranilic Diamide | Larvae | Biofix + 400-450 DD | 14 days | |
| Spintor, Entrust | Spinosyn | Larvae | Biofix + 400-450 DD | 7-10 days | L |
| Delegate | Spinosyn | Larvae | Biofix + 400-450 DD | 14 days | |
| Proclaim | Avermectin | Larvae | Biofix + 400-450 DD | 7-10 days | L |
| Intrepid | IGR (MAC) | Eggs, Larvae, Adults (sublethal) |
Biofix + 350 DD Residue over eggs |
14+ days | L |
| Esteem | IGR (juvenoid) | Eggs, Larvae | Biofix + 100 DD Residue under eggs |
10-14 days | L |
