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JULY 22, 2002 VOLUME 27, ISSUE 5
CODLING MOTH (apples, walnuts)
► WALNUT HUSK FLY (walnuts)
►EUTYPA DIEBACK (apricots, cherries)
CODLING MOTH (Apples, Walnuts)
WALNUT HUSK FLY (Rhagoletis completa)
Codling moth is the most serious insect pest problem for many apple and walnut growers.
Damage from the second flight of codling moth will be present at harvest as interior feeding damage. Our codling moth computer model and pheromone trap catches appear to be very well correlated this year with renewed trap activity beginning at about 1060 degree-days
(DD), so that the predictions listed below should provide the best timing for control measures that I can provide. For those calculating their own DD, I am using an April 11 biofix for all locations. Conventional insecticides should be applied at 200-250 DD following the second flight biofix for apples or 250 DD for walnuts. Insect growth regulators should be applied earlier – see the latest University of California Pest Management Guidelines available at most local Cooperative Extension offices or at www.ipm.ucdavis.edu
if you have Internet access. If you are using pheromone mating disruption, be sure that your product is still effective and that no codling moths are being caught in traps. Some cooler locations may still be within the damage period for the 1B flight. The attached information is only for the 2 nd flight – confirm 1B flight status with your Pest Control Adviser. The appropriate spray timing for conventional sprays (in the absence of computer predictions) is 14 to 17 days after the beginning of a flight in our climate and when previous spray residuals are no longer effective.
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CODLING MOTH (continued)
Location 2 nd Flight Biofix 200 DD 250 DD
(1060 DD from (1260 DD from (1310 DD from
1 st Flight Biofix) 1 st Flight Biofix) 1 st Flight Biofix)
Hollister July 11 July 24 July 27
Ausaymas July 1 July 10 July 13
San Juan Bautista July 13 July 28 July 30
Watsonville August 3 August 18 August 22
Santa Cruz July 30 August 14 August 18
Morgan Hill July 5 July 14 July 17
San Jose July 5 July 15 July 18
Pajaro August 10 August 24 August 28
Salinas August 3 August 18 August 21
King City July 4 July 14 July 16
WALNUT HUSK FLY
Walnut husk fly (WHF) trap counts, in orchards with a past history of severe WHF damage, rose dramatically beginning about July 1 and were reaching trap saturation (250-400 flies per week) by July 11. The first stings from WHF egg-laying occurred in the Southside area of
San Benito County by early July in the ‘Payne’ variety. If you have a past history of severe early WHF damage, you should already have on your first bait spray after confirming your population level. Other locations with light damage in the past should be checking traps now or placing new traps. The traps utilized are the yellow sticky rectangles with ammonium carbonate superchargers. Sprays should continue until about three weeks before anticipated harvest. Varieties will vary in susceptibility – ‘Payne’ is susceptible earlier while ‘Chandler’ seems to become susceptible later in the season than other varieties. Control is extremely important for in-shell varieties like ‘Hartley’ because of shell-staining but early damage to
‘Payne’ walnuts can result in kernel damage such as mold, dark kernels and shrivel.
Check our University of California Pest Management Guidelines for Walnuts for additional information. It lists Nu-Lure bait plus malathion, esfenvalerate (Asana) or chlorpyrifos
(Lorsban) as effective control measures. Bait sprays have been effective when applied at three-week intervals. Full coverage sprays without bait for codling moth control have not always been adequate for WHF control in the past. We currently have no recommended control for WHF in organic orchards although research is continuing and we hope to have some solutions in the near future.
EUTYPA DIEBACK OF APRICOT AND CHERRY TREES
Eutypa dieback disease is the most serious disease problem impacting the long-term survival of apricot trees in the Central Coast. While brown rot may impact this season’s crop and kill twigs

for next season’s crop, it does not kill trees and is controllable with fungicides. Gophers and oak root fungus ( Armillaria ) kill some trees but never to the extent that Eutypa does throughout the district. Cherry trees in our area also have an increasing amount of Eutypa.
Eutypa lata is a fungus disease that infects fresh pruning wounds during rainy weather.
Eventually, the disease spreads from the site of infection to girdle the limb and that branch dies – usually in late spring or summer. Limb death is often so sudden that the dead leaves remain attached to the limb. Other symptoms are darkened bark, amber-colored gumming, discolored hard wood (when viewed in cross-section) and roughened, cracked bark.
Two methods for preventing Eutypa infections have been developed. One is to prune at the traditional time (October to February) and attempt to protect the wounds from infection by chemical or physical means. The other method is to prune in the summer after harvest when the wounds are least likely to become infected.
After years of observation and research, I feel that the second method holds the greatest potential. Pruning after harvest from late July through August results in little re-growth from pruning cuts and few Eutypa infections. Long-term weather records for this area show August to be the driest month. Wounds remain susceptible for two to six weeks and September rainfall in some years might result in infections but certainly not like what might occur later in the fall or winter. Lack of available labor in the summer seems to be the main drawback of this method.
Mechanical topping as practiced in the San Joaquin Valley may be one alternative to the labor shortage.
Chemical and physical control methods hold some promise. Certain fungicides painted on fresh wounds have shown some benefit as wound protectants in the past but at much higher than the label rates for spraying. Drying out wounds with a propane torch has also shown some benefit.
Paints and tree seals have not been effective in past trials but there are newer products that may yet yield some positive results. Very few people have adopted any of these methods due to the extensive labor involved but for large cuts they may be useful.
If you already have existing Eutypa infections, at least prune out the infected limbs at this time.
Try to cut at least one foot below any sign of infection. Large wounds are highly susceptible to
Eutypa infection when cuts are made in the fall or winter.
William (Bill) W. Coates Univ. of Calif. Cooperative Extension
Farm Advisor, Fruit and Nut Crops 335 West Street
San Benito, Santa Cruz , Santa Cruz Hollister, CA 95023 and Monterey Counties
(831)637-5346 phone Mail: P.O. Box 1956
(831)637-7111 FAX Hollister, CA 95024-1956 bwwcoates@ucdavis.edu
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