October 23, 2006

ENTOMOLOGY

2006 pest summary.  Management of internal worms [codling moth (CM), oriental fruit moth (OFM)] in apples continues to be the greatest challenge for West Virginia fruit growers. Although both species have been responsible for fruit injury and loss, the predominant species varies by orchard. However, the number of growers experiencing fruit injury and the level of injury has increased. Although a few early season problems have occurred, most of the fruit injury is beginning to appear in late July or early August, which would be due to second generation CM and third generation OFM. Biofix (beginning of moth flight) was 11 and 10 days earlier in 2006 vs. 2005 for OFM and CM, respectively. In addition, pheromone trap captures at the WVU KTFREC were higher in 2006 than in 2005 for OFM and 1^st and 3^rd generation CM. In general, control has been weak with pyrethroids and where less than maximum rates of organophosphates [Azinphos-methyl (Guthion) and Imidan] have been used.  

Rosy apple aphid populations survived prebloom sprays in quite a few orchards, to subsequently build up to levels causing fruit injury in the early postbloom period. Especially weak were alternate-row-middle programs of pyrethroids or Lorsban, with the first half applied at green tip to half-inch green and the second half at pre-pink to pink. Complete sprays of these materials at half-inch green were more effective. The best control was provided by prebloom applications of Assail or Calypso at pink, with these products also performing quite well as rescue treatments at petal fall at higher rates.

European red mites were not a widespread problem, however, there were some high populations requiring treatment after mid-June, when conditions had become quite dry and hot prior to the 5-6 inches of rain the last week of June. A few locations required treatment in July, and control was generally good, except where threshold levels were already too high when treatment was initiated. Populations of the black ladybird beetle, Stethorus punctum, which have been scarce in recent years were more numerous in some orchards. Populations of predatory mites, especially Amblyseius fallacis, were also more numerous in some locations.

Leafrollers [tufted apple bud moth (TABM), redbanded leafroller (RBLR)] have generally become much less of a threat in most orchards, however, localized hot spots still exist where fruit injury occurs. Sprays of Intrepid targeted against the first generation of TABM or second generation of RBLR have generally been very effective in significantly reducing the second and third generations of these pests, respectively.

Stink bugs, especially brown stink bug, continue to be very abundant late season in most peach orchards and many apple orchards. Overall, fruit injury was less than in recent years, which may have been due in part to increased late season use of pyrethroids in orchards where injury had occurred in past years.

PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC

RBLR = Redbanded leafroller; STLM = Spotted tentiform leafminer; OFM = Oriental fruit moth; CM = Codling moth; TABM = Tufted apple bud moth; DWB = Dogwood borer; LPTB = Lesser peach tree borer; PTB = Peach tree borer; AM = Apple maggot.

PLANT PATHOLOGY

Peach leaf curl control that is virtually 100% effective can be achieved by a single fungicide application during the dormant season. A dilute application should be made under calm conditions anytime after most (no less than 90%) of the leaves have fallen and before hard freezing weather sets in. Thorough coverage of each bud is essential for controlling the leaf curl fungus. If leaf curl was severe in your peach or nectarine blocks in this year, make fungicide applications this fall and next spring before bud swell. Treatments with copper compounds are recommended where bacterial spot has been a problem. In orchard blocks that have been intensively scouted and where the grower knows with certainty that the disease is entirely absent from the block for a period of two or more years, this spray can be omitted until the disease begins to recur.  See the 2006 Spray Bulletin for fungicides and rates of application.

Phytophthora root rot can be managed with mefanoxam (Ridomil Gold EC and Ridomil 5G) and will aid in the control of crown, collar, and other root rots caused by Phytophthora spp. on both bearing and non-bearing apple trees. Ridomil 5G can be used in nonbearing orchards only. Applications should be made on a preventative schedule before symptoms appear, especially in orchards where conditions are favorable for disease development. This would include any young blocks of trees on M.26 rootstock. Ridomil should not be expected to revitalize trees showing moderate to severe disease symptoms. Ridomil is not registered for use as a preplanting dip treatment. For best results, make one application at the time of planting or in the spring before growth starts. Make another application in the fall after harvest. Ridomil is highly specific and will not control other agents causing similar tree decline symptoms, including but not limited to other fungal root rots, graft union necrosis (tomato ringspot virus) and vole damage. 

Dipping the roots of nursery-grown trees into a solution of the fungicide Aliette prior to planting may reduce, but not eliminate, Phytophthora inoculum on infested rootstocks. To use, thoroughly mix Aliette at a rate of 3 lbs/ 100 gallons of water, in the desired volume of water and dip the entire root system for 30 to 60 minutes in the mixture prior to planting.

Apple scab urea application.  A 5% solution of urea (46-0-0) in water may be applied to apple trees as leaves begin to fall in the autumn (42 lb. urea in 100 gal. water, applied at 100 gallons/acre). This should be done as late as possible to prevent the urea from being translocated into the tree. However, it should be early enough to have most of the leaves still on the tree. Note that trees sprayed with urea may defoliate more quickly than unsprayed trees. Urea may also be sprayed on the leaves on the ground, after all the leaves have dropped. The ground spray can also be done in the spring.

READ THE LABEL CAREFULLY AND USE THE CHEMICALS IN ACCORDANCE WITH LABEL CAUTIONS, WARNING AND DIRECTIONS. REQUEST A MATERIAL SAFETY DATA SHEET (MSDS) FROM THE MANUFACTURER FOR EACH PRODUCT YOU USE.

The West Virginia University Cooperative Extension Service, U.S. Department of Agriculture, West Virginia County
Boards of Education and County Commissions Cooperating.  Equal Opportunity / Affirmative Action Institution