David Doll0 commentsNovember 18, 2023Insects

Carpophilus Beetle: What We Know

Authors: David Doll and Zubair Shahzad Carpophilus beetle (Carpophilus truncatus) is a small insect that causes severe damage to almond kernels. The insect overwinters within the soil, and emerges infesting the almonds at hullsplit. They are quite mobile and able to fly up to 3 miles/5km to find a suitable host. Humid conditions increase the emergence and rate of development, leading to multiple generations within a season. More on Carpophilus beetle can be found here. Damage is highly dependent on the variety, harvest timing, and weather conditions. Soft-shell varieties with poor shell seal are most susceptible. Within Australia, the worse damage is reported on Nonpareil, with minimal damage reported on Monterey, Price, and Carmel. Infestation rates increase when harvest delays occur as the nuts are exposed to multiple generations. Rain between hull-split and harvest often increases damage as it results in a faster rate of insect development and harvest delays. Effective management depends on both chemical and cultural practices. In severely infested fields, operations have reported success of applying clothianidin at 1% hullsplit. Early harvest has been shown to reduce exposure and corresponding damage. Nonpareil harvest completion should be targeted by the end of August in the northern hemisphere/February in the southern hemisphere. Winter sanitation is critical to reduce Carpophilus beetle populations. Mummies serve as the initial food source for the beetles as they exit the soil. Operations should target <5 mummies per tree after sanitation. Nuts should be destroyed as soon as possible after winter shaking as the beetle emerges from the soil as it warms. Current trapping methods do not have a lure specifically for C. truncatus. General lures for Carpophilus beetles are available and can be used within bucket traps. Although not providing species level population dynamics, it can provide insight on the emergence of carpophilus beetles

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David Doll2 CommentsApril 5, 2018Insects

Put Leaffooted Bug Monitoring on Your To-Do List

Written By Kris Tollerup, UC IPM Advisor for the San Joaquin Valley Unlike many of the moth pests, we do not have an effective lure that acts to attract leaffooted bug (LFB) to a monitoring trap of some sort.  An LFB lure could be used in almond beginning at mid-March for detecting the pest when they first begin moving into the crop.  Unfortunately, development of a lure remains elusive; researchers out of the University of California, Riverside have worked on the issue for several years now.  They have recently identified compounds used by LFB for sexual and aggregation communication, but synthesis of the compounds has proven quite difficult. This means that good-old visual scouting provides the only viable option.  About this time (mid-March – early April) leaffooted bug begin moving into almond from their overwintering sites.  A caveat to this is that the recent cool weather may have slow their movement and caused some individuals to re-aggregate.  For instance, during early March, we observed signs that LFB had begun to disperse from overwintering sites; however, stopped short and reformed aggregations on nearby citrus trees.  This likely occurred due to cool, wet weather. With warmer weather certainly coming soon, begin monitoring in locations that historically have sustained damage and notably locations near pomegranate and riparian areas.  The bug typically prefers the sunny side of the tree and will rest on nuts on the outside area of the canopy.  Take about 15 seconds to visually inspect about 100 nuts per tree; monitoring 15 to 20 trees in a 5 to 10-acre area. Moreover, the University of California, Pest Management Guidelines recommends monitoring by examining nuts on the ground and in the tree for gummosis.  Keep in mind that gummosis from LFB or other stink bug feed appears clear while gummosis from other

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David Doll4 CommentsMay 13, 2017Diseases, Horticulture

Almonds Exuding Clear Gum

Several calls about gummy nuts were received this week. Of concern are nuts that are oozing clear gum along the suture or side of the hull. There are many potential causes of clear gumming, which include bug damage, boron deficiency, and internal causes from an expanding kernel. Bug damage. Most people are aware of leaf footed plant bug damage. Feeding by this insect can kill the almond embryo when the insect inserts its needle-like feeding tube into the nut. This often leaves a small pin-prick hole which results in clear gum being exuded 3-10 days after feeding. Although the risk of the bug killing the embryo decreases after shell hardening, there can be some staining of the kernel. As the season progresses, feeding by plant bugs decrease, while stink bug feeding can increase. These insects do not have long enough mouth parts to feed on the kernel, but feed on the fruit instead. They often have several feeding points on a single nut. All of these may gum. Severe feeding by stink bugs may impact kernel quality, but the economic threshold of these insects is unknown. Boron deficiency. Too little boron can cause gumming. Usually a clear gum exudes out of the side of the nut or suture line. When cutting the nut open, the kernel is often discolored with copious amounts of gum. These nuts often drop from the tree, and if not, the gum can harden and misshape the kernels, impacting kernel quality at harvest. Another sign of deficiency is a low crop set. Tree boron status should be determined by hull analysis – which has been discussed previously.  This type of deficiency is common in areas that use clean surface water and have not applied any boron to the soil. Physiological- expanding kernels. Occasionally, almonds can gum for no apparent reason.

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Kris Tollerup0 commentsMarch 12, 2017Insects

Leaffooted Bug Aggregations Have Begun to Disperse

  Winter temperatures this 2016 / 2017 season were not cold enough to have any negative impact on overwintering populations of leaffooted bug.  Since mid-October we have monitored large populations on a ½ mile-long pomegranate hedgerow in the Parlier area.  Aggregations averaged about 206 individuals on 19 October with just over 50% of the individuals at the 4th and 5th instar stage.  Temperatures remained mild through November and by the month’s end aggregation size averaged ~30 individuals with 16 and 66% of the bugs at the 5th and adult stage respectively.  The decrease in aggregation size likely occurred due to new adults leaving and not adult or nymph mortality.  The temperature did reach a low of 27° F during the early morning hours of 20 December yet no adult or nymph mortality occurred. Our data suggest that female leaffooted bug began laying eggs on the pomegranate during early September and an entire generation was produced by the end of November.  As the temperatures cooled and the pomegranates began losing leaves and the fruit rotted and dropped, essentially all the adults left for more sheltered overwintering sites. In this case, several thousand of those individuals moved to a nearby palm tree and large Cyprus trees. We have closely monitored the aggregations on the Cyprus trees since mid-February and until early-March the aggregations have remained compact consisting of roughly 5 to 40 adults.  Temperatures have now warmed and we are seeing smaller aggregations, greater flight activity, and individuals on nearby citrus trees.  I interpret this increase in leaffooted bug activity as an indicator that the bugs have begun to disperse and will soon move into almond in search of food. Weekly monitoring should begin within the next seven to 10 days through May, and then every one to two weeks through June. 

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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 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 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 Doll0 commentsApril 6, 2015General

Mid-Spring Considerations/Update

The 2015 almond season is in full swing. Many orchards have went through their drop, fertilizer applications and irrigation have began, and pest management concerns are beginning to form. Below are some thoughts and considerations from recent field visits. 1. Crop development is ahead of schedule – by as much as a month. Kernel fill is beginning in many ‘Nonpareil’ orchards, meaning that ‘Butte’/’Padre’ orchards won’t be far behind. This timing is important as about 80% of the season’s nitrogen budget should be applied prior to kernel fill – which may occur as early as early May! Secondly, it indicates that at this point – “What you see is what you’ll maximally get” in regards to kernel size, and farming practices – more particularly irrigation practices – can only reduce crop size. 2. Peach Twig Borer’s (PTB) “May Spray” timing looks to be an April timing. In the Merced area, our traps picked up a biofix around March 15th, which means we will be approaching 300 DD in about 7-10 days. Keep in mind that the spring spray timing for PTB is 300-400 degree days after the biofix. It may also be possible for the May Spray to have some effect on NOW.  Frank Zalom (UC Davis Entomologist) has found through research trials that timing the spray to 100 DD post NOW biofix (egg traps) and around 400 DD post PTB biofix can provide good control of NOW and PTB at harvest. 3. Rain is predicted for Tuesday (the 7th). Hopefully some rain will fall in the valley to help with the multitude of water issues. This rain may also bring some potential for fungal disease – especially rust and scab. Consider an application if there has been a history of disease. This application can be made 1-2 days after the rain event and

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