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Integrated Cranberry Crop Management Cranberr y for Wisconsin Crop Management Newsletter University of Wisconsin-Extension Volume XXIV Issue 5 August 1, 2011 Cranberry Girdler Management Tim Dittl, Agricultural Scientist, Ocean Spray Cranberries, Inc. Biology & Life History eventually kill the vines beyond the point of attack. Damage from larvae can often Cranberry girdler can be a sporadic but times go undetected but usually can be serious soil insect pest for growers in Wis- This Issue: found in August and continuing into Sep- consin. Although this insect is found to oc- tember. The most notable damage is gen- cur in all growing areas located throughout Cranberry 1 erally found the following spring after the the state, girdler is not necessarily a pest on Girdler winter flood has been removed and the all cranberry acreage therefore, careful moni- Management plants start to grow out. Often times, the toring of your marsh is essential in order to foliage drops off leaving areas or patches of Observations 3 detect any potential problems. dead vines where weed species can soon From the Field— Cranberry girdler belongs to the Pyrali- takeover. Injury from girdler is easily diag- Cira dae family, also known as pyralid, grass, wax nosed by looking for the presence of larvae Observations 4 or snout moths of the order Lepidoptera and chewing on the underground horizon- From the Field- (moths and butterflies). These complexes of tal stems and runners during the summer Sojka moths are also referred to as sod webworms months. and are widely known to be pests of culti- Scouting for Girdler and Economic vated and wild grasses. Girdler overwinters as full-grown larvae in a cocoon buried in the Thresholds leaf litter on the beds. In the spring, larvae Pheromone baits specific to capturing complete their development, pupate and girdler moths are commercially available to start to fly as adult moths in June. Adult ac- growers and should be used to help monitor tivity periods generally occur from early June seasonal adult flight activity. Traps should be to mid-August; peak flight normally occurring placed out in early June in suspected hot during the last week in June or first week in spots or areas that have had a history of gir- July depending upon your location. Fortu- dler. In addition to using pheromone traps nately, there is only one generation per year. the sweep net can also serve as a monitoring Cranberry girdler larvae damage the vines tool however, adult moth activity can best by attacking the roots and chew through the gauged by walking the fields and observing bark of the underground stems and runners the amount of girdler moths that you “kick sometimes completely severing the vine. up”. If you determine that indeed they are More often, larvae will gnaw or ‘girdle’ the girdler (fruitworm moths may look similar), bark completely around the runners or carefully monitor your weekly trap counts. stems. Depending on the severity of attack, Currently, no economic thresholds have been established for girdler adults; however, larval feeding can weaken and reduce the based on experience, if average counts ex- vigor of the vine limiting production. Above ceed 50 moths/trap (particularly if peak flight ground foliage eventually becomes red or brown and under severe infestations, may See Cranberry Girdler Management p. 2 An EEO/Affirmative Action employer, University of Wisconsin-Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements Volume XXIV Issue 5 August 1, 2011 Page 2 Cranberry Girdler Management (continued from p. 1) is sustained), keep a close eye out for any potential, sub- at a later stage when their mandibles can process sequent larval activity. Remember too that trap counts woody substrate. If grasses can be prevented from can be greatly influenced by the weather. growing in a bed, particularly during July and August when the eggs are laid, then the girdlers will also be If vines start to show stress, become discolored or prevented from establishing themselves in great exhibit signs of dieback during the months of July or Au- numbers. In the lab, when given a choice between gust, carefully check the underground portion of the reed canary grass and cranberry, most larvae were plants for girdling or chewing. The best way to do this is found in the roots of the grass. In a no-choice situa- by following the upright(s) in question back to runner tion where neonates were given access to grass portion of the plant to determine if there is any damage plants only or cranberry only, nine times as many and/or presence of larvae. Larvae are generally white to neonates survived on the grass than on cranberry, cream-colored with a brown head and reach a little over and most were in the roots. Apart from grasses that a half inch long. Food waste, excrement or “frass” (little are generally the preferred host plants, girdler is also brown pellets) from the larvae is often times found in known to attack cranberry, Sheep Sorrel and Doug- association with feeding. fir plantings. Control Strategies Chemical control tactics have been employed Viable management strategies for the control of gir- in the past but with limited success. Currently, the dler are somewhat limited. However, by employing the only product labeled for Cranberry girdler in Wis- use of multiple control tactics, one will hopefully be able consin is the relatively new insecticide Belay®. Re- to keep this pest in check. The use and practice of the cent studies and evidence suggests that Belay® ap- following control options should help suppress girdler plied as a post-bloom soil application at the 12 fluid populations and hopefully reduce or even prevent them oz/acre rate will help control girdler larvae feeding from causing economic plant injury. underground. Spot treatments of affected areas Cultural practices are by far the most important within a bed or treating whole beds may be sufficient methods for suppressing girdler infestations. Sanding will while broadcast applications on the entire marsh help bury overwintering pupae in the soil and hinder the often times may not be necessary. Timing of applica- adult moths from emerging the following year. Routine tions is made approximately 2-3 weeks following sanding every three to five years should help prevent gir- peak flight as first signs of girdler larvae appear, nor- dler from becoming established as a major pest problem. mally between July 21 and August 10. A degree-day Flooding has also proven to be very effective against gir- model developed by the University of Wisconsin is dler larvae. A deep flood over the top of the vines for a also available to assist with the timing of this applica- period of 24-48 hours in the later parts of August or tion. Note that only one application of Belay® at early September will help drown the larvae. Try and the 12 oz/acre rate is allowed in Wisconsin. Please choose a period of time that will be generally cool and refer to the supplemental label for cranberry for cloudy or even during a rain event versus sunny, warm further use instructions. weather to help protect the fruit from scald conditions. Young green berries will not hold up as well to flood con- ditions versus berries that are more mature and starting to color. References to products in this publication are for Other more recent research suggests that weed your convenience and are not an endorsement of one control may also be an important factor in reducing gir- dler populations. Newly hatched cranberry girdler larvae product over similar products. You are responsible for (aka neonates) need and prefer soft, succulent plant tissue using pesticides according to the manufacturer's cur- at or below ground level to feed on to enhance their sur- rent label directions. Follow directions exactly to pro- vival rate. In the cranberry bed, grasses are probably cru- cial for their survival. Young larvae can become estab- tect the environment and people from pesticide expo- lished on grass crowns or roots then move to cranberry sure. Failure to do so violates the law. Page 3 Cranberry Crop Management Newsletter OBSERVATIONS FROM THE FIELD Theresa Cira Lady Bug IPM, LLC Pheromone baited traps are used during bloom as a way to monitor the adult flight of cranberry pests. The traps consist of a lure scented with a chemical in a sticky white cardboard tent. The intended purpose of the phero- mone scent is to attract the males of pest moths however there is always a variety of creatures to be found in the traps. Some other moth species are also drawn in by the pheromones and the traps are like a giant buffet for preda- tory insects and spiders who then can wind up getting stuck in the sticky traps themselves. We have even found tree frogs taking advantage of the trapped insects for an easy lunch. Additionally many insects meet their demise in the trap simply because they landed to rest on the sticky surface. The following descriptions are just a small example of the variety of insects and other arthropods we find in the traps in the field. In the Cranberry Fruitworm traps we have seen Bilobed Loopers otherwise known as Megalographa biloba (Lepidoptera: Noctuidae). These moths have two char- acteristic camel hump like bumps along their backs and a white splotch on each of its two brown front wings. The cat- erpillars are light green with black shiny eyes and a white strip along their side. They are known to eat alfalfa, cabbage, dan- delion, barley, sage, and tobacco, among other plants.

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