David Doll0 commentsJanuary 12, 2017General, Horticulture, Weeds

Dormant Practices and Wet Weather

Over the past week, a lot of rain has fallen across California. Orchard access should be limited during periods of wet soil to reduce soil compaction as well as stuck equipment. Limiting access, however, creates challenges in performing a variety of orchard operations, including the list below.   Winter Sanitation. Removal of almond mummies from trees is critical for Navel Orangeworm management (NOW). Many operations usually wait for the first rains to help with leaf drop and to help “loosen” the mummies. In wet years, however, it becomes difficult to winter shake the trees as orchard conditions remain too wet for access of shakers. Furthermore, the “window” to winter shake is limited on the late end as fruit bud loss increases as trees enter delayed dormancy and buds swell (Mid to late January, depending on location). To manage this limited access, operations should consider poling crews. If these aren’t available, and sanitation is not performed, a spring timed (usually late April through early May) insecticide can reduce overwintering NOW. This strategy is not as effective as winter sanitation, but is better than doing nothing. Insecticide sprays targeting NOW in the dormant period are NOT effective due to NOW pupae being inside of the almond mummies. Planting bare root trees. Hand planting crews have an easier time than machine planting due to limited field access. If planting delays occur, trees should be placed into cold storage at the nursery as soon as possible to reduce the risk of leaf out and weakened trees. Keep trees in cold storage until ready to plant. Unless there is no other option, do not take delivery of trees in bins or plant them in a temporary location at the farm. On delivery, check tree roots to make sure they are healthy and living (should be

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Jhalendra Rijal0 commentsDecember 22, 2015Insects

Role of Winter Sanitation for Navel Orangeworm Management

Written by: Jhalendra Rijal, Area IPM Advisor, UC-Cooperative Extension (San Joaquin, Stanislaus, Merced) Navel Orangeworm (NOW) is a primary pest of almonds, pistachios, and walnuts, with other significant crops hosts such as fig, citrus, pomegranates. This pest was first introduced in southern California in 1942 potentially from Central and/or South America. Because of the wide host range, this pest was quickly spread to the entire Central Valley within 5-7 years of its first introduction, established and had become a major production threat in almond and other nut crop production. Adults are greyish-brown moths (about ½ inch long) with grey markings on wings. Eggs are laid in mummy nuts or in the nuts with initiation of hull-split. Tiny first instar larvae bore into the nutmeat and all stages of larva feed on nuts producing large amount of webbing and feces (i.e. frass). Larvae are white to pink with a reddish-brown head, and with a typical crescent-shaped markings on the second segment of the body just behind the head. The mature larvae (5th instar) can grow upto ¾ inch in size. Besides direct damage on nuts, NOW larval damage can lead to fungal infections, such as the mold that produces aflatoxin, known to cause carcinogenic and mutagenic effects on human. The larvae overwintered in mummy nuts that are in trees or on the ground. Among non-chemical ways of reducing NOW populations or damage include early harvest and winter mummy removal (i.e. sanitation).  Winter Sanitation of orchards during the winter is the most effective way to reduce the damage in upcoming season. Mummy nuts should be removed from the trees before bud swelling stage (late January/early Feb.) by shaking the trees or by hand polling. The nuts should then be destroyed on the orchard floor by discing or flail mowing by March 15. UC IPM

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Franz Niederholzer6 CommentsJanuary 22, 2013Horticulture

What is Dormant?

I see what seems like a lot of leaves still left in some orchards around the Sacramento Valley, even after a wet and windy end to 2012.  Aldrich trees look to have the most leaves remaining.  This observation got me thinking about questions I’ve heard regarding leaves, dormancy, chilling and bloom timing/duration.  These questions include: Are trees with leaves remaining in January less dormant or somehow different than trees that are defoliated or naturally bare by January? Doesn’t spraying trees with zinc in the fall make them dormant faster? They don’t have leaves… Do trees with some leaves left in the canopy in January accumulate less chilling than trees with no leaves in December?

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David Doll3 CommentsJanuary 5, 2012Irrigation

It’s Been Dry – Should I Irrigate? Part 2

I have had many inquiries about applying an irrigation since we have been lacking adequate (if any) rainfall. At this time of the year, with bloom 5-6 weeks away, the answer is “yes.” As bloom approaches, it is important to have adequate moisture within the soil to a depth of at least 30 inches to promote root growth during the first root flush. Research in peaches suggest that this first root flush occurs about two weeks prior to bloom. Irrigation sets should not last longer than 24 hours and should target around 0.5 – 0.75 acre inches of applied water. After the application, the water should have time to infiltrate the soil, about 3-4 days, before the next irrigation is applied. Following these practices will help reduce the saturated soil conditions that favor soilborne diseases such as Phytophthora. After each irrigation, check the depth of the added moisture. Once moisture reaches four to five feet, application of water can be discontinued. Rainfall will only help refill the soil profile. Keep in mind that at this point, we will need more than five inches of rain to refill the moisture in most soils without supplemental irrigations. If it rains within the next two weeks, irrigate before the rain event with another 0.5 to 0.75 inches. This will help increase the effectiveness of the rainfall. If there is no rain in the two weeks, plan for another irrigation. This may be a good time to apply a pre-emergent herbicide. An irrigation will “water in” the herbicide, but the effect will be limited to the wetting pattern of the irrigation system. Four weeks ago, the answer to this question was a “no.” Attempting a poor excuse for why I changed my mind — I thought we would have received some rain by now.

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David Doll0 commentsJanuary 5, 2012Irrigation

It’s Been Dry – Should I Irrigate? Part 2

I have had many inquiries about applying an irrigation since we have been lacking adequate (if any) rainfall. At this time of the year, with bloom 5-6 weeks away, the answer is “yes.” As bloom approaches, it is important to have adequate moisture within the soil to a depth of at least 30 inches to promote root growth during the first root flush. Research in peaches suggest that this first root flush occurs about two weeks prior to bloom. Irrigation sets should not last longer than 24 hours. After the application, the water should have time to infiltrate the soil, about 3-4 days, before the next irrigation is applied. Following these practices will help reduce the saturated soil conditions that favor soilborne diseases such as Phytophthora. After each irrigation, check the depth of the added moisture. Once moisture reaches four to five feet, application of water can be discontinued. Rainfall will only help refill the soil profile. Keep in mind that at this point, we will need more than five inches of rain to refill the moisture in most soils without supplemental irrigations. This may be a good time to apply a pre-emergent herbicide. An irrigation will “water in” the herbicide, but the effect will be limited to the wetting pattern of the irrigation system. Four weeks ago, the answer to this question was a “no.” Attempting a poor excuse for why I changed my mind — I thought we would have received some rain by now.

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David Doll2 CommentsDecember 18, 2011Irrigation

Its been dry, should I water?

Although we have received a bit of rain this past week, some inquiries about applying a winter irrigation have been made. There is concern that since the soil is dry from lack of rains, that the trees will be stressed, negatively affecting the fruit bud. Briefly, an irrigation in December to alleviate water stress in dormant trees is not needed in most cases. In order for water to move into the tree’s branches, it needs the “pull” created by the leaves (transpiration). Without leaves, the water may move into the roots, up a few inches into the wood through capillary action, but not into the branches and buds within the mid to upper canopy of the tree. The only exception may be in a situation of extreme drought, in which the trees have had considerable seasonal stress and complete defoliation. This occurs rarely in California. There are other reasons to apply a winter irrigation. These include refilling the soil profile to help with irrigations scheduling in the spring, and watering in an applied pre-emergent herbicide.

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David Doll2 CommentsDecember 11, 2011Diseases, Insects

Dormant Spray Considerations for Almonds

Scab lesions on green wood of almond. Being one of the quieter times of the year, the dormant period is a prime time to assess orchard issues and begin applying strategies to reduce various diseases and insect pests. Surveying the orchard and sampling new growth and spurs can help identify problems of scab, San Jose Scale, Navel Orange Worm, and mites. If populations are high enough, dormant strategies can be applied to reduce the damage to the upcoming season’s crop. Scab. If a scab outbreak and the corresponding mid- to late-season defoliation were experienced this past year, a dormant/delayed dormant application of copper and oil should be considered. This spray is effective in reducing and delaying sporulation of scab twig lesions, thus reducing in-season disease incidence. It should be used in combination with properly timed bloom and petal fall sprays. Based on field observations, orchards with significant scab outbreaks in 2010 that followed the above recommendations had obvious suppression of the disease in 2011, and were able to keep the leaves on the trees until late November. Red Halos caused by San Jose Scale feeding/infestation in almond. Insect Pests. Spur samples should be selected throughout the orchard to determine the presence of San Jose Scale (SJS), European Red Mite (ERM), and Brown Almond Mite (BAM). Spurs should be pulled from a main scaffold with 100 spurs samples from the orchard. If 20% of the spurs selected are infested with scale, then a one-time oil application at 6-8 gallons per acre should be applied. If over 60% of the spurs are infested, the oil application should include an insect growth regulator that targets SJS. It is important to control SJS as high populations can kill spur wood, reducing crop load. Obvious signs of scale infestation include a red halo found on

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David Doll16 CommentsJune 22, 2009Horticulture

The Seasonal Patterns of Almond Production

When reviewing previous posts of this blog, I realized that not much information has been provided about the general biology of the almond tree. To cover this area, I decided to focus on the seasonal cycle of almond trees. In general, the season progresses in the following pattern: Dormant,Delayed Dormant, Bloom, Post-Bloom, Fruit Development, Harvest, and Post Harvest. Each period will be broken down and discussed. Dormant:As the temperatures from the late fall continue to drop, the tree enters a period of rest that lasts through December/Early January. At this time, the tree has dropped all of its leaves naturally or through an application of zinc, and is maintaining a low level of water use and starch consumption. This “low” flow of starch through the tree is needed as the catabolic breakdown of starch to sugar prevents the sap from freezing. This is, of course, only if the tree was able to develop enough starch reserves in the previous fall. In the rare occasion of low starch reserves, cold damage can occur leading to canopy and scaffold loss. Picture 1: A dormant spur. The cold temperatures that the tree is exposed to at this time helps with the development of the fruit buds. The tree requires a certain amount of moisture and chilling hours to come out of dormancy. Once the chilling hour requirement has been met, bud grown will begin with warmer temperatures. Chill hours are dependent upon the variety,but almonds generally need between 500 and 600 chill hours. In general, chill hours are the number of hours between the temperatures of 32-45 degrees Fahrenheit. Winter hours above 60 degrees are subtracted from the totals. Delayed Dormant:In late January/early February the tree begins to push a flush of fine feeder roots. These roots provide moisture and nutrients for the

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