David Doll5 CommentsJuly 1, 2016Insects

Airblast v/s Electrostatic Rigs: Is there a Difference?

Hull-split sprays have began across the southern valley. These sprays are made to protect the crop from the infestation by Navel Orangeworm (NOW). During this time, it is common to receive questions regarding spray coverage. A common question received is about the comparison of electrostatic versus air-blast sprayers. A spray trial was conducted at the Nickels Soil Lab near Arbuckle, CA to compare the coverage and NOW control of an axial fan/air-blast and electrostatic spray rig.  Sprays were applied between 9:30 – 11:45 PM, when temperatures were below 75oF and relative humidity above 65%, to minimize evaporation and maximize spray coverage.  The replicated trial consisted of three treatments: Axial fan, air-blast sprayer (John Bean Spraying Co., 500 gallon tank, 36” fan, PTO driven; 143 gpa, 1.75 MPH, 170 psi system pressure) Air-shear, air-blast sprayer with electrostatic droplet charging (Progressive Ag, Model 2250, PTO driven; 50 gpa; 3.3 MPH and 30 psi system pressure). Air-shear, air-blast sprayer without electrostatic droplet charging (Progressive Ag, Model 2250, PTO driven; 50 gpa; 3.3 MPH and 30 psi system pressure). Eighth leaf ‘Fritz’ trees were sprayed with Delegate WG insecticide at hull-split timing. Applications included a molybdenum tracer to help determine spray deposition. Results: The spray coverage and NOW control results from the study (1 Day After Treatment) can be found in the table and summarized into four points. Sprayer Treatment Hull Mo Deposition – Upper canopy (15-20 ft) % NOW survival Upper Canopy (15-20 ft) Hull Mo deposition – Lower Canopy (5-7’) % NOW survival Lower Canopy (5-7’) Standard Axial-Fan/Airblast Sprayer 0.06 a 1.64% a 0.09 a 0.19% a Electrostatic Sprayer with electrostatic charge 0.05 a 3.20% b 0.18 1.01% b Electrostatic Sprayer w/o electrostatic 0.07 a — 0.15 b – Different letters indicate different statistical groupings at p<0.05. -Results pooled with those from

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Jhalendra Rijal0 commentsFebruary 15, 2016Insects

Monitoring and management of San Jose scale and other insect pests during the dormant season

This is the time of the year to assess the seasonal activities of certain insect pests in the orchard and make treatment decisions for the delayed-dormant spray. This evaluation provides guidance for planning in-season pest management activities. Insects that can be evaluated using dormant spur sampling includes tiny insects (Scales: San Jose scale, European fruit lecanium; non-webspinning mites: brown mites, European red mites), and overwintered worms (oblique-banded leafroller, oriental fruit moth, peach twig borer). Although dormant spur sampling does not cover navel orangeworm damage evaluation, it is critical to know how much percentage of the mummy nuts are infested with navel orangeworm larvae and follow the proper winter sanitation (see details here). Scale is a bit different in its lifecycle in comparison to other insects. It is a tiny insect that sucks the plant juices from the plant parts such as spurs, branches, fruits and foliage. SJS females are sac-like, legless insects that are covered by the protective shield, made up of waxy secretion. Since they don’t have legs to move, they are permanently attached to the host plant tissues and feed. Because of the protective cover, often, spray coverage is not sufficient to knock down the population especially in large and dense trees. SJS female and her offspring produce several thousands of progenies in one season. Feeding by a large number of scales can cause significant damage to fruit spurs and scaffolds, leading to reduced tree growth and productivity. In severe cases it can cause death of the new spurs and tree limbs in severe cases. So, knowing the density and/or activities of scales and the natural biocontrol activities on spurs is important for making a treatment decision. Spur sampling during the dormant season Use spur sampling (follow the UC IPM guidelines) Take 100 spurs randomly taken from 35-50 trees (inside/outside/high infestation area)

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David Doll1 CommentJanuary 18, 2016Insects

Bloom Bt for Peach Twig Borer Control

Written by John Edstrom, UCCE Farm Advisor Colusa County, Emeritus Hopefully, the central valley will finally receive drought relief from recent El Niño driven storms. The resulting wet soil conditions, however, can prevent orchard access for many orchard operations including dormant sprays. Without dormant insecticide sprays, peach twig borer (PTB) populations can increase dramatically and threaten next years crop. Worm reject levels were troublesome and costly to many almond growers this past season and point to the need to control PTB. Besides kernel damage, twig borer feeding also kills young buds and shoot tips after bloom and deforms young tree scaffold limb development . Fortunately, growers have a very safe alternative to dormant sprays using Bacillus thuringiensis (or Bt) to control PTB during the bloom season without harmful side effects to applicators or the environment. Other insecticidal materials claim to be safe to bees but may negatively impact bee colony health. Bt has no adverse affects to any stage of honeybees or the health of the hive.  Bt is a natural bacterial based insecticide that is toxic only when ingested by lepidopteran larval stage pests and is completely safe to beneficial predators and parasitoids. Bt is exempt from pesticide use regulations and so is particularly useful near urban or environmentally sensitive areas. The bloom Bt control strategy has proven effective since its was developed in the 1990s during a time when regulations were restricting the use of the highly toxic organophosphate spray materials. Bt is a perfect fit for almond IPM programs. Its only down side is that multiple applications are needed for complete control. Fortunately, Bt products are inexpensive and can be tank mixed with fungicides applied for blossom and leaf diseases around bloom, so the total costs are comparable or less than standard insecticides. Generally, two sprays are

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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 Niederholzer4 CommentsJuly 17, 2015Insects

Good Spray Coverage: Watch the Air

Written by: Franz Niederholzer, UCCE Farm Advisor, Colusa and Sutter/Yuba Counties and Luke Milliron, UCCE Horticulture Intern Good spray coverage is vital to effective pest control.  Nowhere is this truer than for NOW control at hull split.  Excessive sprayer speed kills spray coverage, especially in the tree tops.  But is there a simple way to figure out how fast to drive a sprayer to deliver good coverage in the tree tops while getting across the orchard in a timely manner?  Yes, watch the air.  Since airblast sprayers use forced air from the sprayer fan to carry pesticides throughout the tree, if the air from the sprayer fan(s) reaches the top of the canopy, the pesticide spray should get there, too. The following is a simple way to evaluate sprayer air movement in the canopy tops at different ground speeds.  Free hanging surveyors tape makes a great air movement indicator.  Tie 12-24” of surveyors tape to the top of a length of PVC pipe threaded through the branches in the middle of the tree row into the tree tops.  [Another option is to use a pruning tower to get up in the tree tops and tie several lengths of tape onto the highest shoots.]  Fill the sprayer half full of water, turn on the pump, close the spray booms, and run the sprayer down the row at a set speed with the fan on at operating tractor RPMs.  Have someone record a video of the movement of the tape(s) in the tree tops with a smart phone or iPad.  Review the video after the spray moves past the pole.  Did the tape move at all?  If no, then the sprayer air didn’t reach the tape, and neither will pesticide.  The sprayer needs to drive slower, or you need a sprayer with a larger

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Franz Niederholzer0 commentsMay 29, 2015Insects

Navel orangeworm management at harvest: When, what, & how to get the best results

Franz Niederholzer, UCCE Farm Advisor, Colusa & Sutter/Yuba Counties; Emily Symmes, UC IPM Area Advisor, Sacramento Valley Almond nuts become vulnerable to navel orangeworm (NOW) damage at hull split.  In the south Sacramento Valley this year, Non-pareil hull split is expected in the last week of June, about the same time as last year, based on the prediction model developed by UC researchers (see it on-line at:  http://fruitsandnuts.ucdavis.edu/Weather_Services/almond_hullsplit_prediction/).  Protecting nuts from NOW (and peach twig borer) with hull split sprays and timely harvest are key to delivering a high quality crop to the huller and maximizing grower returns.  If you haven’t already, now is a good time to plan your hull-split spray(s). Non-pareil (NP) nuts split first – and have the most value.  Not surprising, the primary focus in NOW management is protecting NP nuts.  The worst NOW damage to NP nuts occurs if the nuts are still in the trees when 3rd generation NOW egg laying begins.  Harvest should occur when 100% of the nuts have split but the hulls are still green (see picture below). If this can be accomplished before 3rd generation egg laying, a significant portion of NOW damage to NP can be avoided.  Preconditioning of just-shaken nuts accelerates their drying and hastens pickup, reducing nut exposure to protein feeding ants and allowing irrigation ASAP before pollinizer harvest.  Careful orchard monitoring of NOW populations using egg traps and degree days indicate when egg laying should occur.  This can be supplemented with using pheromone traps to follow male flights.  In addition to timely harvest, properly timed and applied hull split sprays can help reduce the overall NOW population in the orchard and thus limit crop damage and income loss from current and future resident NOW generations. Once hull split occurs, growers can target different NOW generations depending

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David Doll0 commentsMay 23, 2015Insects

Webspinning Spider Mite Management in Almonds

Written by David Doll (UCCE Merced) and David Haviland (UCCE Kern) As summer approaches almond growers need to be monitoring for webspinning spider mites.  The most common species during the summer are Pacific and twospotted spider mite, though on occasion strawberry spider mite can be found. As adults, all three mites look and behave similarly, even though control of Pacific spider mite is more difficult to control. Webspinning spider mites overwinter in the orchard under rough bark and ground litter. During the spring, usually in March and April, migration will occur from these places into the lower areas of the tree.  These early-season populations are typically small, do not reproduce quickly, and often become prey to early-season natural enemies.   However, as temperatures warm in late May through September, the populations increase rapidly, particularly if natural enemies are absent. In favorable conditions, a lifecycle can be completed in 7-10 days, with 8-10 generations a year. Spider mites damage leaves by sucking cell contents and damage initially appears as a light stippling. As populations increase, mites and their eggs become more visible, and eventually “webs” will appear around spurs and leaves. Leaves with high populations will fall from the tree, reducing carbohydrate production.  If leaf loss becomes severe there is a potential for crop loss the following year. Spider mites are most problematic in orchards that are dusty or where the trees are stressed.  Stressing factors can include insufficient irrigation, nutrient deficiencies, or excessive crop load. The most important factor in spider mite management is biological control.  When natural enemies are abundant, miticides are not needed.  When natural enemies are absent, control with even the best miticides can be short-lived.  The goal is to find a balance that relies primarily on natural enemies supplemented by miticides as needed. The most important predators

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David Doll2 CommentsMay 2, 2015Insects

Stink Bug Damage within Almonds

Stink bugs are found occasionally in almonds. They feed on the almond hulls from late April through July, causing gummosis and kernel abortion. Typically, multiple feeding points are found on an almond and within an area of the tree, with few feeding holes extending into the kernel after shell hardening. Even without reaching the developing kernel, excessive feeding can still cause crop loss, kernel discoloration, as well as infections of the fruit by yeast, other fungi, and bacteria. There are several different species of stink bugs that affect almonds. Most common is the green stink bug, but the red-shouldered stink bug can also be found. These insects tend to move into the field during the spring when weed or crop hosts begin to dry up – which tends to be earlier in years of low winter rains. The green stink bug may also overwinter within the orchard. Eggs tend to be barrel-shaped and laid in clusters on hulls. There are currently no treatment thresholds for stink bugs. The decision to treat should be based on the appearance of damage and the extent of the damage. Monitor the orchard for gummosis and try to observe the pest to separate it from feeding that may be caused by leaf footed plant bug. Unlike leaf-footed plant bug, stink bugs aren’t as mobile and sprays can be very effective. Use of a broad spectrum insecticide should reduce populations. Data suggests that an application typically reduces populations enough that another treatment may not be needed for three years. More information can be found at the UC IPM Webpage for Stink Bugs.  

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David Doll0 commentsApril 17, 2015Horticulture, Insects

Early Nut Split – Nut Drop or Bug Damage?

A few samples and farm calls have yielded nuts that are splitting pre-maturely. These nuts tend to be yellow in color and are often found dropping from the tree during high winds. Sometimes, the nuts have gum along the suture, or gum “specks” on the outside of the hull. These nuts could either be a “June Drop” as the tree is balancing the crop load or it could be kernel death caused by leaf-footed plant bug. The nuts dropped  could be the last dropping period within almonds. These nuts, when cut open, would be brown at the base of the nut, indicating the death of the connective tissue. Gum may exude from the suture of the hull. More importantly, there would be no noticeable holes through the hull or in the shell, although some degradation of the shell cells may occur. In contrast, Leaf-footed plant bug would have a pin hole through the hull. This hole would often extend through the shell and into the kernel, causing a darkened spot at the point of entry and a shriveling of the kernel. Gum may appear on the exterior of the hull where the bug entered its mouth parts, but does not always occur. Although gumming is usually immediate (if it occurs), nut yellowing and subsequent drop — based on research — occurs 14-23 days after the point of feeding/damage, variety dependent. Gumming is not as frequent on younger nuts. Knowing the cause of drop can provide information relevant to treatment decisions. If the drop is due to leaf footed plant bug, a treatment may be warranted. It is important, however, to determine if the bugs are still within the orchards. Since the nut drop is visible several weeks post feeding, the bugs may have moved out of the orchard and the

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David Doll4 CommentsMarch 20, 2015Insects

Leaffooted Bug Advisory for Almonds

Written by Kris Tollerup and David Haviland University of California Cooperative Extension and UC Statewide IPM Program Pest control advisors need to be on the lookout for leaffooted bug. All indications are that 2015 has the potential to be a significant year for leaffooted bug damage to almonds.  This prediction is based on observations of very high populations of LFB during the fall of 2014 and a high overwintering survival rate due to mild winter weather.  During the past few days (~March 15th) multiple reports from across Kern County have been sent to UC Cooperative Extension offices that PCAs are starting to see movement into crops.  Although no known reports of leaffooted bugs have occurred in the mid and more northern growing areas, it would be prudent to begin monitoring now. Monitor for LFB at least once a week from mid-March through May, and then every one to two weeks through June.  The most effective monitoring method is to do a visual survey for the presence of bugs.  This can be done by using a long pole to knock branches in the upper tree canopy, causing the bugs to fly such that they can be seen or heard. Visual inspections should be coupled with inspections of the fruit by looking for gummosis on the almond hull.  However, by the time gummosis is seen, damage has already occurred.  Gummosis can also occur due to physiological damage.  Therefore, if the method is used, cross-section the area with gummosis to determine the presences of a pin-sized discolored wound caused by the penetration of the insect’s mouthparts.  Also inspect fruit on the ground for the presence of gummosis and a stinging wound to determine if LFB is the culprit.  Be sure not to confuse gummosis caused by LFB (clear to light amber color) with

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