Summer leafroller control: Scouting will save you money!
Editor’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.
Scout to determine need for control measures
The availability of several excellent obliquebanded leafroller control materials has growers asking advice for proper timing and sequencing of these materials, but before insecticide applications are undertaken, growers are best advised to first determine whether such applications are necessary. Due to the difficulty in scouting for overwintered obliquebanded leafroller larvae in early spring, obliquebanded leafroller insecticides are routinely recommended as part of an early spring spray program on farms with historical leafroller damage. As larvae mature in late spring, though, their presence is far easier to detect, and 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 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 are surviving.
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 from within the trapped orchard, 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. 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.
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 also 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 2 percent of the terminals were infested should be monitored in the summer, but controls may not be warranted. Higher levels of shoot infestation are cause for concern and control measures are likely needed to prevent fruit injury. This investment of time could result in saving several sprays.
Obliquebanded leafroller GDD model
|
Event |
Action |
|||
Tight cluster |
Majority of larvae have emerged from shelters |
Examine fruit buds for larval activity |
|||
0 DD° = biofix | |||||
|
Chemical Class |
Life-stage |
Optimal Spray Timing for OBLR |
Residual Activity |
Mite Flaring Potential |
Guthion, Imidan |
OP’s |
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 |
Spintor, Entrust |
Spinosyn |
Larvae |
Biofix + 400-450 DD |
7-10 days |
L |
Rimon |
IGR |
Eggs, |
Biofix + 100-200 DD |
14+ days |
M* |
Proclaim |
Avermectin |
Larvae |
Biofix + 400-450 DD |
7-10 days |
L |
Intrepid |
IGR (MAC) |
Eggs, Larvae, |
Biofix + 350 DD |
14+ days |
L |
Esteem |
IGR (juvenoid) |
Eggs, Larvae |
Biofix + 100 DD |
10-14 days |
L |