Think about the need for a dormant spray

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					In This Issue * Need a Dormant Spray?? Maybe Not!! * Peer Training on Avoiding Water Contamination and Pesticide Drift (Volunteers requested) * Other Meetings * Fall Checklist
Need a Dormant Spray? Maybe Not! You can determine whether on not you need the traditional dormant spray for scale insects, European red mite, peach twig borer and prune aphids. The decision to apply a dormant treatment should not be automatic but one of sound judgment based on monitoring. Lets review the importance of the four pests a dormant spray controls and control options. Scales: Usually we are talking about San Jose scale (SJS) although other scale insects can occur such as European fruit lecanium (EFL). High populations of SJS cause shoot dieback, scale on the fruit, and an unthrifty tree. Is a damaging level of scale present?: If you have been applying annual dormant insecticide/oil treatments, chances are very good scale has not built to damaging levels in your orchard; a dormant spray for scale is likely not needed. If you have not been applying a dormant spray, the beneficial parasites Aphytis melinus and Prospaltella sp. probably occur keeping the scale insects in check. Again chances are, scale is not a problem and a dormant spray this year is likely not needed. But, how do you make sure? Use IPFP‟s “Best Management Practice” (BMP) of monitoring. The IPFP project developed a monitoring technique to determine scale levels and need for treatment. It involves fruit spur monitoring for scale if you find 10% of a dormant spur sample with live scale, a dormant spray is advised. Any U.C. farm advisor working with prunes can explain this technique. Also watch for winter meeting announcements. Several will be held to demonstrate and explain the technique.

If you have potentially damaging scale, what are the dormant treatment options? Oil alone in the delayed dormant period (as buds swell) can give good control of low, “border line” scale populations. High scale populations require inclusion of an insecticide with the oil for adequate control. What are other treatment options if I do not put on a dormant treatment? Although dormant is the preferred timing for scale control, a second option is treating in May with oil or an insecticide. European Red Mite (ERM) Do I need to worry about ERM? ERM is not a web-spinning mite and is not the mite that causes leaves to drop off the tree; those mites are two-spotted and/or Pacific mites. There is no documented evidence ERM causes economic damage to prunes. In fact ERM is an important food source for beneficial insects in the spring. So, there is no reason to control this mite with a dormant treatment. Note, twospotted and Pacific mites are not controlled with a dormant treatment. Peach Twig Borer (PTB) Is a damaging level of PTB present: PTB can cause shoot dieback and damage to fruit. We have observed 30 or more orchards for five or more years and have only seen one orchard where PTB damage was high enough to prohibit the grower from “fresh pick”; PTB damage to the dry product was not sufficient to score. So, if you have been applying an insecticide/oil dormant spray for a number of years, you do not have PTB built up in your orchard. A dormant spray for this pest this year is likely not needed. How do you make sure? Use BMPs. Examine your orchards‟ historical grade sheets. Has PTB caused problems in

the past? If not, a dormant spray for this pest is not likely needed. What are the dormant treatment options? Either organophosphate (OP) or pyrethroid insecticides combined with oil have been traditional treatments. Success (Spinosad) has been effective when applied during the dormant season. Every other year dormant treatment has been an effective program against PTB. Other treatment options: You can also control PTB with one or two applications of Bacillus thuringiensis (BT) applied during bloom, or in May. This latter treatment option requires using the BMP monitoring technique developed by the IPFP project. That is, looking at 1200 fruit at 400 degree-days after the PTB biofix is determined from PTB pheromone traps. If 2% of the fruit have PTB damage there is a damaging population and treatment should be applied then. If you are not familiar with this monitoring technique any U.C. prune farm advisor can assist you. Prune Aphids These include leaf curl plum aphid (LCPA) and mealy plum aphid (MPA). LCPA curls leaves. Do I need to worry about aphids? Heavy populations of LCPA cause small fruit to distort and drop. Shoots also become deformed. MPA secretes honeydew and heavy populations cause fruit cracking. The dormant insecticide/oil treatment is very effective against these aphids; dormant oil alone gives little control. Not all orchards get aphids if not dormant sprayed. About 50 % of unsprayed IPFP orchards were found to have a spring aphid problem of various magnitude. Consequently about 50 % of all prune orchards require a dormant spray for aphid control.

How do you predict an aphid problem? Use BMPs. Examining your orchards‟ history of this pest; it‟s a very good way of knowing how important this pest is. For example, if a dormant treatment has been applied in the past and aphids still occur in some areas or in general at a low level, this suggest a more serious aphid problem will occur if the dormant treatment is omitted. Another way is to use the IPFP monitoring technique. Use the dormant spur sample for scale mentioned above. If you see one aphid egg while examining dormant spurs, an aphid problem is indicated and treatment is suggested. Both BMP techniques, orchard history and monitoring, are excellent ways of assessing the likelihood of an aphid problem next spring. What are dormant treatment options? To help minimize insecticide runoff, the IPFP project has developed a BMP for aphids. Rates of Diazinon or Asana as low as 25% of the commonly recommended rate, when combined with oil, can be used to effectively control aphids in the dormant season. IPFP is working on another potential BMP for aphids (research not concluded yet), this recommends applying the dormant spray early, as soon as the leaves are off, to avoid winter rains and

runoff. Another possible BMP technique IPFP is working on uses foliar zinc for zinc deficiency correction before October 1st. Coincidently, this spray causes early leaf fall eliminating a food source for fall-returning aphids. This has potential for reducing or eliminating aphid problems the next season. What are other treatment timing options if I do not put on a dormant treatment? During bloom, a single application of oil has given good control if it is applied when aphid eggs are hatching. Two applications of oil, one at five percent bloom and a second 10 days later greatly increases the chances of oil providing effective control. In the spring and early summer, use IPFP‟s BMP of tree monitoring to see if any aphid population is large enough to justify treatment; if more than 20% of the trees have a significant aphid population a treatment is justified (any U.C. prune farm advisor can assist you with the sampling technique). If this is the case, high rates of oil will significantly suppress, and many insecticide choices will control MPA. If LCPA is the problem then an insecticide with “fuming action” such as Diazinon is required.

The Bottom Line By following IPFP‟s “Best Management Practices” of monitoring and reviewing an orchard‟s history, a grower can easily determine his/her dormant treatment needs. In most cases there will be no need for a dormant treatment for SJS, EFL or PTB and there is no need to control ERM in prune orchards. In about half the cases, a dormant treatment will be needed to control aphids. To help the environment and avoid pesticide runoff into waterways, reduced rates, alternative materials, and/or alternative treatment timings can be used to control these pests.

Peer Training on Avoiding Water Contamination and Pesticide Drift I have been involved in helping plan a workshop on “Avoiding Water Contamination and Pesticide Drift.” Pesticides in ground and surface water are two of the most important issues facing agriculture. This training will give participants practical and effective tools to deal with these issues. Also, if a handler understands the “why” behind decisions and practices being implemented, he or she is more able/likely to do the “what” in the most effective way. Demonstrations, an onfarm tour, and other methods will be used so that participants will learn ways pesticides can contaminate water and how to reduce risks of contamination & exposure. A personalized checklist created by each handler/supervisor team will include decisions & steps they themselves decide are the best for their operation. This workshop is to take place on January 15th and the plan is to have volunteer peer (growers) trainers make the presentations since participants will get more out of the workshop if it was presented by their peers. Consequently volunteers are being requested. What kind of volunteer trainers are we looking for? The ideal volunteer peer trainer will be someone with practical pesticide experience. What’s in it for the volunteer trainer? Peer recognition. Building knowledge and training skills. A chance to benefit the ag community by training its membership in pesticide risk reduction to water quality. Lunch will be provided on the day the volunteers are trained and on the day they extend their training. Continuing Education Credit: For the training-of-trainers, 2 hours of

„laws & regs‟, and 3 hours of „other‟. For the „extension of training event: 2 hours of „laws & regs‟ and 2 hours of „other‟. Each trainer‟s employer can register one handler/supervisor team for the January 15, 2004 training free of charge. (Save $35). What commitments are volunteer trainers expected to make? Attend a 5 to 6 hour “training of trainers” event on January 8 where UC IPM staff will prepare trainers. Spend 1 to 2 hours with another trainer to prepare for “extension of training” event. Give 4 hours for an “extension of training” event on January 15 where trainer teams will extend their training to handlers & supervisors with support from UC IPM staff. After they have participated in the “extension of training” event, trainers will be prepared and encouraged to carry out their own independent events. If they decide to carry out their own events, UC IPM staff will be available to help them prepare. When / Where / Who: January 8: Training-of-Trainers at CSU Chico Farm January 15: Trainers train Handlers/Supervisors at CSU Chico Farm The enrollment application for this workshop will be mailed to you next month. If you are interested in volunteering to be trained on the subject on January 8th and to provide training on January 15th please contact me at (530) 538-7201 or Tim Stock, UC IPM Program, at (530) 752-6841. Other Meetings Two hours of continuing education credit is being offered by the Agricultural Commissioner‟s Office for participation

in a meeting on “Pesticide Laws and Regulations” at the Durham Memorial Hall from 8:30 am to 11:00 am on December 2nd, 03. Fall Checklist Preparation for Planting Next spring: Mark sick or dead trees now for removal. All leveling, ripping, backhoeing and fumigation in preparation for planting or replanting should be done now while the soil is warm and dry. Backhoe sights should be mounded at least 18 inches above ground level and allowed to settle over the winter. This will avoid settling after planting in the spring. If possible avoid Marianna 2624 (except where Oak Root Fungus exists) rootstock on replants since this is the most likely rootstock to result in bacterial

canker. Also a good fumigation job is essential on replants to help avoid bacterial canker.  Weed Control: Pre-emergent herbicides should be applied to the berms and orchard floor before winter weeds emerge. This will eliminated the necessity of including a contact herbicide in the spray.  Zinc Soil Treatments: If foliar sprays haven‟t helped your zinc deficient trees, and you only have a few trees involved try the ground application now by placing zinc sulfate in a circular trench 2—8 feet out from the trunk depending on tree size. Follow this by applying half as much ground sulfur in the same trench to keep the soil acid. Zinc sulfur rates are 10 lbs. per tree up to 8 inches per diameter, up to 50 lbs./tree for the largest trees.


				
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