How to Manage Pests
UC Pest Management Guidelines
Several leafrollers in the family Tortricidae are present in strawberry and vegetable-growing areas of the Central Coast. Of these species, the garden tortrix is the most likely to be found feeding on strawberry fruit. The orange tortrix and apple pandemis are primarily foliar feeders. The light brown apple moth, an introduced species, was first detected in the San Francisco and Monterey Bay areas in spring 2007. The adults of all of these leafrollers have brown markings and the typical bell-shaped tortricid moth wings while at rest. Some leafrollers have only one generation in a year, but most leafrollers that feed on strawberry foliage have 2 to 4 generations a year, depending on species and location. When disturbed, these leafroller caterpillars wriggle vigorously.
The adult garden tortrix is a buff-brown moth that is about 1/4 inch (6 mm) long. Each of the forewings is marked with a dark brown diagonal stripe and a marginal spot producing a chevron pattern when at rest. A faint whitish line borders the anterior edge of the brown stripe. This character and the overall lighter color distinguish adult garden tortrix from orange tortrix. The slender caterpillars of the garden tortrix are nearly 1/2 inch (12 mm) long when mature. Caterpillars have light brown to green bodies and light brown heads. The head has a small, distinct dark brown spot on each side. Larvae and pupae overwinter in debris around the base of the plant.
Adult orange tortrix and apple pandemis moths are about 0.5 inch (12 mm) long. Orange tortrix moths have light brown forewings. Apple pandemis moths have a series of lighter and darker rust colored V-shaped bands with the center band on the forewings edged with white. Apple pandemis caterpillars are green with yellowish green or straw-colored head capsules. Orange tortrix caterpillars have straw-colored to greenish bodies with a yellowish head capsule and prothoracic shield.
In both appearance and behavior, the light brown apple moth is similar to the other leafroller species. Adults are light brown in color, about 1/4 to 1/2 inch (6 to 13 mm) long, and display variable patterns of dark brown on the wings. The caterpillar is pale to medium green and has a light brown head capsule. Fully-grown caterpillars are 1/2 to 3/4 inch (10 to 18 mm) long. Updated information on light brown apple moth and regulatory quarantine procedures in California can be found on the UC IPM Web site and at your county Agricultural Commissioner's office.
Most leafroller larvae, including the light brown apple moth, tie one or more strawberry leaves together with white webbing to create shelters. Larvae can also create shelters by binding leaves or the sepals of the calyx to fruit and may feed from these sheltered areas on the surface or internal tissues of fruit.
Early in the season, the garden tortrix serves a valuable function in breaking down and recycling old leaf and fruit litter. It generally does not cause significant damage when strawberry plants are small. However, as the population increases and the plant canopies close in, more ripening berries come in contact with trash where they may become exposed to the tortrix larvae. When this happens, larvae will often spin a nest in creases along the berry's surface and may chew small, shallow holes in the berry, incidental to their scavenging. Thus, as populations increase in late spring or early summer, significant fruit losses can result from both larval contamination and secondary rots invading the feeding holes. During late June and July, contamination of south coast fields just before the berries are sent to the processors can be a serious problem. Fruit damage can appear similar to that caused by other Lepidoptera larvae including corn earworm, armyworms, and cutworms.
The light brown apple moth is unique; its detection in strawberry fields will result in difficulties shipping fruit out of the quarantine area.
In areas with a chronic tortrix problem, it may be feasible to remove accumulated trash in spring around the plants to limit the potential for a large population buildup. This is especially important in summer plantings and second year fields where it is more likely for leafrollers to be present. Because it is difficult to distinguish the light brown apple moth larvae from other leafrollers in appearance and behavior, a preventive approach, consisting of sanitation, monitoring, and chemical treatments, targeting all leafrollers is currently suggested for strawberry fields within quarantine zones. This will ensure that no larvae will be present in harvested fruit. This approach will avoid shipment delays and possible loss of fruit marketability.
Remove dead vegetation from strawberry fields to reduce overwintering populations. Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use in organically certified strawberries. Sprays of Bacillus thuringiensis can be more effective if applied multiple times at close intervals, because it exposes survivors of previous applications to another dose of this material. Additionally, it can be helpful to lower water carrier volumes to concentrate the dose of the material ingested by the larvae.
There are several ways to monitor for leafrollers, including the light brown apple moth.
In the spring, before the commencement of harvest, begin monitoring by examining plants for larvae. Leaf rolls made by larvae are not hard to find and tend to consist of one or more (usually mid-aged) strawberry leaves webbed together. If a leafroller or the concomitant webbing is detected, it is recommended to search more thoroughly in the immediate vicinity of the initial find, because leafrollers often aggregate. Larvae in fruit can be detected during harvest. The infested fruit and larvae should be destroyed. Webbing under the calyx, frass, or holes in the fruit, all indicate leafroller activity. Fruits have to be observed closely, since early leafroller instars are exceedingly small and can hide under the calyx.
With all leafrollers, directed sprays that penetrate the foliage canopy at a sufficient volume are recommended. Because of the tendency to have overlapping generations, it is difficult to target a specific larval stage.
Garden tortrix larvae are particularly difficult to control with sprays, because they are located in the litter beneath the protective canopy of strawberry leaves.
|Common name||Amount per acre||R.E.I.+||P.H.I.+|
|The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.|
|(Success)||6 fl oz||4||1|
|MODE OF ACTION GROUP NUMBER1: 5|
|COMMENTS: Most effective against younger larvae. Rotate to an insecticide with a different mode of action after two successive applications. Maintaining proper pH of the spray tank water is critical for maximum efficacy.|
|(Coragen)||3.5-5.0 fl oz||4||1|
|MODE OF ACTION GROUP NUMBER1: 28|
|C.||BACILLUS THURINGIENSIS ssp. KURSTAKI#|
|MODE OF ACTION GROUP NUMBER1: 11|
|COMMENTS: Treat when armyworms are still small. To be effective, Bt must be applied no later than the 2nd instar.|
|(Intrepid 2F)||6-12 fl oz||4||3|
|MODE OF ACTION GROUP NUMBER1: 18|
|(Radiant SC)||6-10 fl oz||4||1|
|MODE OF ACTION GROUP NUMBER1: 5|
|COMMENTS: Rotate to an insecticide with a different mode of action after two successive applications (Success/Entrust have same mode of action). Maintaining proper pH of the spray tank water is critical for maximum efficacy.|
|F.||DIAZINON*||12.75 fl oz/100 gal water||3 days||5|
|MODE OF ACTION GROUP NUMBER1: 1B|
|COMMENTS: Do not allow this material to run off into surface waters.|
|+||Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|#||Acceptable for use on organically grown produce.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.|
UC IPM Pest Management Guidelines:
UC ANR Publication 3468