1995 Annual Report for ANE95-024
Biopesticidal Strategies for Insect Management in Cranberry
Summary
Results to Date
This project tests the effectiveness of biopesticides and trapping as methods of pest control for key pests of cranberry. The majority of insect pests affecting Massachusetts cranberry growers are contained in two complexes: the scarab root grubs (four species of beetles) and the foliage and fruit-feeding Lepidoptera (seven species of moths).
Through this project, we have developed a monitoring trap for the cranberry white grub which will soon be available commercially.
Our research indicates that none of the biopesticides currently available are effective against the cranberry fruitworm.
Tests with Spinosad were encouraging and will be continued.
Objectives
1. Management of the scarab grub complex, cranberry white grub (CWG) (Phyllophaga anxia), oriental beetle (OB) (Anomala orientalis), Hoplia modesta (HM), and cranberry root grub (CRG) (Lichnanthe vulpina).
A. Conduct sex pheromone studies:
Develop adult trap and monitoring guidelines,
Survey occurrence of adults on and off bogs, and
Evaluate mass-trapping options.
B. Evaluate biopesticides:
Bacillus thuringiensis Buibui,
Insect growth regulator, RH-0345, and
Heterorhabditis bacteriophora and Steinernema glaseri nematodes.
2. Management of lepidopteran pests with biopesticides:
A. At grower demonstration sites, evaluate B.t.-based products against foliage-feeding larvae; and
B. Evaluate tebufenizide (Confirm) against foliage- and fruit- feeding larvae.
Method and Findings
Scarab root grubs are highly problematic for MA cranberry growers because there are no management tools in place for any of the pests. Our approach to the scarab root grub complex is two-fold, involving development of monitoring traps for adults and evaluation of biopesticidal controls for larvae.
A monitoring trap is an excellent tool to determine pest identity and infestation levels for several reasons: larvae are aggregated, and thus, infestation levels are hard to accurately assess; sampling destroys the cranberry vine (a perennial); three of the four species of larvae cannot be grower-identified in the field; and work shows that each species responds differently to applications of various biopesticides.
For CWG, a major accomplishment is final development of a monitoring trap, which was tested this year by nine grower cooperators. The genitalia of several thousand adult male beetles caught in these traps were examined to determine capture levels of non-target, non-pest species of June beetles. We found nearly all beetles captured were the pest species, P. anxia. We are now moving to commercial production of the CWG trap. A third year of mass trapping of CWG at two sites was completed. Because this insect has a three-year life cycle, next year will be the indicator year for the effectiveness of this approach.
For CRG, the two major components of a likely sex pheromone from females (Z-7 16C alcohol and Z-7 16C aldehyde) isolated last year were used in field tests at varying ratios; 1,411 males were trapped in seven treatments at five sites, with no clear differences among treatments.
Regarding evaluations of biopesticides against grub larvae, both the insect growth regulator and B.t. Buibui that we have been working with have been withdrawn by the manufacturers. On the other hand, the nematode H. bacteriophora appeared effective against HM in 1996 and 1997 field trials. These nematodes, if available, can be recommended at a two million rate for HM.
The second group of targeted pests is the fruit-and foliage- feeding larvae of moths, which includes the two species responsible for the majority of insecticides applied to cranberry: Sparganothis fruitworm (SFW) (Sparganothis sulfureana) and cranberry fruitworm (CFW) (Acrobasis vaccinii). In research of SFW, three cranberry-registered (but not tested) formulations of B.t (Xentari, Mattch, and Crymax) were studied. Mortality after 8 days was 100 percent, ca. 25 percent, and ca. 38 percent respectively. Also with SFW, 100 percent mortality was observed on Spinosad-treated foliage. Preliminary tests with CFW were highly variable for all treatments and suggest that, for this very serious pest, none of the biopesticides currently available will be of value in management.
Biopesticides against species of spanworm, cutworm and gypsy moth were also evaluated and results are highly promising but show that B.t. recommendations will be based on additional work. There was ca. 70 percent mortality of false armyworm on Crymax-treated foliage and 100 percent mortality on Mattch-treated foliage (small larvae, 5-10mm). As soon as the larvae were a little bigger (12-18mm), mortality was half as high (ca. 30 percent with CryMax, and 38 percent with Mattch).Tests with Spinosad were impressive. All false armyworm, green spanworm, brown spanworm (Ematurga amitaria) and gypsy moth (Lymantria dispar) larvae were dead after feeding for 1-2 days on Spinosad-treated foliage. Separate dose-response lab assays on first and third-instar gypsy moth confirmed the efficacy of Spinosad as a leaf dip even at levels as low as 1/9th of field rate; efficacy of tebufenizide was also high against 1st-instar gypsy moth.
Reported November 1997.