Insect Management

Prepared by Anne L. Averill and Martha M. Sylvia

Essential Points!

• Start scouting bogs early May.  Black-headed fireworm, green spanworm and winter moth larvae may be active early but larvae are difficult to see until mid-May.  Always gauge levels of pest caterpillars in their early stages!  As the caterpillars of many species grow larger, they cling more tightly to the vine or hide in daytime and are harder to pick up in daytime sweep netting.
• Immature cranberry black bug and blunt nosed leafhopper appear as tiny green/yellow nymphs in mid May.  These must be discerned from harmless springtails (Collembola).  Be aware that most pests can be very patchy or in coves or edges, particularly scale, black bug, cranberry weevil, spongy moth, black-headed fireworm, and brown spanworm. Thorough assessment of total acreage is essential.  
• Vaccinium scale can be detected in spring by walking the bog and looking for off color or weak areas. Carefully look for live scales on the oldest parts of the uprights.
• Keep an eye on Cranberry Fruitworm.  Management with Altacor has reduced populations, but there may be pressure.   Cultivars with the earliest fruit sizing up may be hard hit with egglaying. Be aware that there may be two peaks of fruitworm egglaying: a large one in late June, early July with a second smaller peak towards the end of July.  
• Be careful with advanced growth.  Be aware that the new growth and early flower buds on newer cultivars, sanded areas, and renovations may be magnets for pest insects.  Cranberry weevil, in particular, can move to beds with advanced vine development.  Feeding on new growth and egg-laying is of concern. All insect activity could be moved 2 weeks forward.
• Sweep netting.  Using a 12” net and 180° sweeps into the vine, sweep netting should be conducted at least once a week.  A sweep set consists of 25 sweeps across the bog.  The insects in the net should be properly identified, counted, and recorded.  Conduct 1 set of 25 sweeps for each acre.  For larger pieces (more than 20 acres), at least 1 sweep set/2 acres is advisable.  In multiple-acre pieces, calculate the average number of each insect in all of your sweep sets.  Treat only after the average numbers of each insect in your series of sweep sets exceeds these values, and after other external concerns have been considered including cost of application, expected returns, weather, etc. 
   
   

In sweep net sampling, the average numbers of a pest that we use to trigger a management measure is only a guide.  It serves as an indication that an insect pest is being sampled at numbers that we consider high and worthy of attention.  Significant pressure by cranberry weevil and particularly by black-headed fireworm and Sparganothis fruitworm should be attended to in the spring; infestations are harder to manage in the summer.  

Reducing inputs to cut production costs. Key insect management practices should be the last ones eliminated to save money. It is seldom advisable to skip the first cranberry fruitworm spray (initial spray in IPM-based programs when most pinheads have set and berries have begun to size up) unless late water has been held. This first spray targets the largest portion of the population.  Sweep netting in early to mid-May is important to detect spongy moth and black-headed fireworm.  Finally, walk the bog both early and late in the season to inspect for injury from scale and fireworms to detect pests that have long term impacts.

Pheromone traps. Traps can be used for timing management of black-headed fireworm and Sparganothis fruitworm and should be up by June 1.  Use 1 trap/10 acres.  Place on upwind side of bog.  Check and clean traps weekly, recording number of moths captured.  Change bait every 3 weeks. 

Based on pheromone trap catches… 

• For black-headed fireworm: treat summer generation with Altacor or Intrepid and apply 2 weeks after onset of moth flight (~6/20), and again 10 days later. For Sparganothis fruitworm: if treating with Altacor or Intrepid, apply 3 weeks after the moth flight begins (~late June), and again 10-14 days later. If using Delegate, apply 10-14 days after peak moth captures, (~mid-to-late July); vines wet with Delegate spray pose high risk to bees, time the spray to allow drying by morning. Dried residues are considered safe.
• For Sparganothis fruitworm: if treating with Altacor or Intrepid, apply 3 weeks after the moth flight begins (~late June), and again 10-14 days later. If using Delegate, apply 10-14 days after peak moth captures, (~mid-to-late July). Vines wet with Delegate pose a risk to honey bees. Dry residues are considered safe. Time spray to allow for drying by morning.

BEES!!!  Most insecticides are toxic to bees, especially direct applications.  Do not apply or allow to drift to cranberries in bloom or nearby blooming plants/weeds if bees are foraging.  Bumble bees may be equally vulnerable to sprays applied at bloom; populations will dwindle over time if they are not protected. 

Bee protection is complicated

If possible:

• Leaving some beds of untreated flowers allows dilution of pesticide concentration experienced by bees. Even for pesticides considered bee-safe (fungicides, Altacor, Intrepid), unbroken areas of treated mass bloom may result in risk for colonies.
• Expanding the number of days pre-bloom that many insecticides are applied may reduce residues in pollen. Bee-toxic Sevin, Diazinon, and Actara are absorbed by the plant and move systemically into developing flowers and contaminate the pollen.
• Research in other crops has shown that the combined effect of some insecticides/fungicides (tank mixes of Altacor/Indar, Altacor/Proline, and Altacor/QuadrisTop) impact honey bee colony health.

Cranberry Insect Pests Commonly Encountered in Massachusetts

Previously Common Insects but Seldom Seen Now

Chemistry Families of Cranberry Insecticides

• Diamide-based compounds. Altacor, Exirel and Verdepryn are newer chemistry insecticides registered in the diamide class of chemistry and provide a new mode of action compared to all other classes. They cause paralysis of the insect by sustained contraction of the muscles. It has excellent activity against our key lepidopteran pest (cranberry fruitworm). Altacor also has long residual activity and is safe to key natural enemies. Exirel and Verdepryn in comparison have high bee toxicity and cannot be used during bloom. For all these compounds, a good chemigation system, under 6 minutes, is likely necessary to get good efficacy. Target eggs and tiny larvae, these compounds will not manage larger caterpillars effectively.
• Bacillus thuringiensis (B.t.) based products. Examples labeled in cranberry are Dipel, Xentari, Crymax and Biobit. These compounds are most effective when applied multiple times and in low gallonage against small caterpillars feeding on foliage. Thorough coverage is essential. Well-timed chemigation systems are critical for good efficacy (6 minutes or less rinse time). Early attention to infestation is critical. Caterpillars stop feeding after eating compounds but may take several (3-10) days to die. Use aerial application or low-volume ground applications when possible to improve performance.
• Insect growth regulator products. (Intrepid (methoxyfenozide), Confirm (tebufenozide) and Rimon (novaluron)). Growth regulators are caterpillar-specific, need to be eaten to work, and conserve natural enemies and pollinators. These compounds are most effective when applied multiple times and in low gallonage against small caterpillars feeding on foliage. Intrepid is restricted use and is Zone II restricted. Coverage and well-timed chemigation systems are critical for good efficacy (6 minutes or less rinse time); excessive chemigation washout will remove active material. A spray adjuvant should be used. 6 hours drying time following application is required. New vine growth is not protected. Larval death may not be observed until a week or more has passed. Pollinator safe!
• Spinosyn-based products. These include Delegate and Entrust (an organic formulation). Delegate is more active and provides longer residual control than Entrust; Delegate is the compound of choice. Spinosad-based products are fast-acting nerve poisons but are still reduced-risk compounds. Allow 7 days between applications. These compounds are the better choice (compared to Intrepid) once the caterpillars have reached a larger size. For Delegate, only use lower rates if rinse time is 4 minutes or less. Keep in mind that spinosyn products can be toxic to natural enemies and are highly toxic to bees. Sprays made when bees are actively foraging must be avoided (this includes Entrust, even though it is an organic formulation!). Wet residues are toxic, dry ones are considered safe. If treating during bloom, be sure that overnight conditions are such that evening chemigation applications will dry by morning.
• Neonicotinoid products. Neonicotinoids affect the nervous system of insects but have low human toxicity. They are the most toxic insecticides to bees. Do not apply during bloom. There are a number of neonicotinoid compounds registered in cranberry including Actara (thiamethoxam), Assail (acetamiprid), Scorpion/Venom (dinotefuran) and Admire (imidacloprid). While these compounds could help manage our insect complex, you should be informed before you use them.
• Organophosphate and carbamate products. Organophosphate and carbamate products are in an older class of chemicals and are nerve agents acting on the enzyme acetylcholinesterase. These compounds are generally acutely toxic to bees, wildlife and humans. Do not apply during bloom. Diazinon, Imidan, Orthene and Sevin remain in use although much reduced. Sparganothis fruitworm, cranberry weevil, tipworm and leafminers are resistant to this chemistry.
• Pyrethroids. (Fanfare, Danitol, Pyganic) Pyrethroid insecticides are an older class of chemicals and disrupt nerve signals by disrupting the sodium channel (sodium channel modulators). These compounds are acutely toxic to aquatics. They have low human contact toxicity but high oral toxicity. Do not apply during bloom.

NOTE:  Restricted Use Insecticides (Actara, Diazinon, Fanfare, Intrepid, and Scorpion/Venom)  
A private applicator certification is required to purchase, handle and apply these compounds to your bog.

Reflooding Options

1. Late Water Flood – Starting April 10-20, hold water for 30 days to manage cranberry fruitworm, southern red mite, spongy moth, and cutworms. See Late Water section.
2. Spring Flood – mid-late May, 24-hour reflow manages false armyworm and blossomworm, 48 hours necessary to impact black-headed fireworm and yellow-headed fireworm. Care must be observed as these floods must be completed before roughneck stage or likely to increase fruit rot and seriously reduce the crop.
3. Summer Flood – Mid-May to mid-July kills all insects, especially cranberry root grub and white grub, but with the loss of crop and impact on following years as well.
4. Fall Flood – Sept. 20-30. Flooding within this time for 1 week every third year discourages girdler and blossomworm. A 3- or 4-week flood at this point will manage cranberry fruitworm. These floods are best done when fruits have been removed. Research shows that this flood timing may negatively impact vine health.

Organic Options for Insect Management

Organic production may not be a profitable unless there is low to moderate insect pressure and a good water supply. Cranberry fruitworm, black-headed fireworm and cranberry weevil pose the greatest threats to viability.   Certifiers work under standardized USDA rules. Growers who wish to be certified organic need to go through Bay State Organic Certifiers (www.baystateorganic.org). All inputs must be listed with OMRI (Organic Materials Review Institute; www.omri.org).  Some products are listed as A (allowed) others as R (restricted).  The restricted products have certain conditions attached to them that have to do with the generic materials in the product (amounts or frequency of application, etc.).  OMRI also has a Generic Materials List.  Three years of no synthetic chemical applications (transition period) are necessary before a crop can be certified organic.

Cultural Practices

Use of cultural practices (sanding and water floods) is the most effective strategy in organic management.

• Late Water - Holding late water is an excellent choice to reduce cranberry fruitworm pressure; however, moths may move into late water-treated beds from other areas of infestation.  False armyworm, blossomworm, spongy moth, and southern red mite may be managed with late water. See Late Water Section.
• Fall Flood - May be used to reduce cranberry girdler populations.  Flood for 10-14 days as soon as possible after harvest.  May also impact vines to some degree.  Warmer water temperatures enhance effectiveness.
• Sanding - If you can sand, populations of most insects should be less abundant.
• Winter Flood - If you can maintain a good winter flood, populations of most insects should be less abundant.

Options cleared for organic management on cranberry, but efficacy has not been quantitatively assessed