David Doll0 commentsMay 18, 2010Insects

Peach Twig Borer and May Spray Timing

Peach Twig Borer (Anarsia lineatella) (PTB) is a long time pest of almonds, being first reported in California in the 1880s. It was considered to be the worst pest of almonds until the arrival of the Navel Orange Worm in the 1940s. Today, it still remains an important pest because of its direct damage to the nuts, damage and feeding on green and new shoots – killing terminal growth, and the preference of PTB damaged nuts by navel orange worm. PTB can be found overwintering as a worm (larva) in a tiny cell (hibernaculum) within the crotches of one to three year old wood. They may also survive in pruning wounds and bark cracks. Larvae emerge around bloom and migrate up the twigs and branches where they tunnel inside the branch, killing the terminal shoot. This loss of terminal shoots and subsequent delay in growth can be very problematic for young orchards. Figure 1: Damage to terminal branches caused by Peach twig borer. PTB adults begin to emerge around late March/ early April. Adults are gray in color and are about a 1/4 to a 1/2 inch in length. The adults lay eggs on twigs during May and June which give rise to the second flight of moths in Late June/Early July. Second generation moths then repeat the cycle, causing damage and laying another generation of eggs. Figure 2: Peach twig borer larva causing damage inside an almond fruit/hull. Nuts become more susceptible to damage as they near harvest. Feeding on green nuts by PTB makes them more attractive to NOW. Branch damage, although problematic on young trees, is not considered an issue on mature trees. Cultivars differ in their susceptibility to nut damage, Merced and Thompson are the most susceptible, followed by Nonpareil, Fritz, Price, and Ne Plus Ultra.

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David Doll1 CommentMay 2, 2010Insects

Managing Orchard Ants – time to scout for activity!

Pavement and Fire ants can cause significant damage to the almond crop. Feeding throughout the year on seeds of grasses and broadleaves, ants are only problematic once the almonds are shaken to the ground. Ants can completely hollow out the nut, leaving only the pellicle behind. Damage increases the longer the almonds are on the ground. Within the San Joaquin Valley, the southern fire ant has a wider distribution and usually causes more damage than the pavement ant. Pavement ants are found in the northern San Joaquin Valley and into the Sacramento Valley. Within Merced County, we have both the Southern Fire Ant and the Pavement Ant. Recently, Merced County has had infestations of the Red Imported Fire Ant (RIFA), a third problematic ant for almond growers, requiring quarantine actions to control this invasive pest. Please see Guide to Identifying Orchard Ants to help identify ants. Ants tend to be problematic on drip or sprinkler irrigated orchards. Within flood irrigated blocks, ants are limited to tree berms. Moist, cool temperatures increase above ground activity of ants; hot temperatures drive the ants deeper into the colony. Varieties with a tight shell seal are more resistant to ant damage, or with shell splits less than 0.03 inches wide. Shell seal can vary greatly year to year depending on crop load, nut size, and horticultural practices. The orchard should be surveyed for ant colonies 2-3 days after an irrigation in the months of April – May in order to determine if a treatment is needed. Once the temperatures increase, problematic ant surface activity decreases, giving an inaccurate count of the population. In scouting for ants to determine if treatment is necessary, choose five survey areas per orchard, each about 1000 sq. ft., including the soil area from mid-alley to mid-alley beneath trees. Count the number

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David Doll2 CommentsMarch 2, 2010Insects

Fungicides and Bee Health

I have had a lot of questions/concerns regarding bee health and bloom fungicides sprays. Even though bloom is nearing its end, I thought I would try and answer a few questions I have received – and finally had some time to research and formulate an answer to these questions. Do fungicides applied during bloom affect bee health?The short answer is “We don’t know.” Research has shown that fungicides that are applied around or at bloom do adhere to the pollen, and are brought back to the hive during the process of pollination. The fungicides then inhibit the growth of different fungi within the bee hive, decreasing the the microbial diversity of the bee’s food source. As of the Almond Board of California 2009 Research Proceedings, it is unknown whether or not the fungi affected benefit or harm the overall health of the hive. Which Fungicides are transported back to the hive?Researchers at the Carl Hayden Bee Research Center in Tuscon AZ found five commonly used fungicides in the bee bread (food source) of hives placed in almond orchards. These fungicides include Chlorothalonil, Cyprodinil, Fenbuconazole, Iprodione, Boscalid, and Pyraclostrobin. The amounts of fungicide appear to vary by orchard and timing of application – BUT – this data was only based on hives placed in three orchards with two or three samplings- for now. Also, it is not known which fungicides target which fungi, if they negatively affect bee health directly, and if they have a negative impact on the entire hive by reducing the quality of the food source. The research group headed by Dr. DeGrandi-Hoffman will be looking into these questions through this year. What about Pristine (Pyraclostrobin-Boscalid) applications?Essentially, we don’t know exactly how this fungicide affects fungal growth in the hive. In vitro studies from Dr. DeGrandi-Hoffman’s lab indicates

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Franz Niederholzer1 CommentJanuary 18, 2010Insects

New pesticides are effective on Peach Twig borer in early sprays

Author: Franz Niederholzer, UC Farm Advisor Sutter-Yuba Counties Peach twig borers (PTB) are a key pest of almonds. Nuts damaged by PTB are preferred feeding sites of navel orangeworm (NOW). At a recent almond IPM meeting in the San Joaquin Valley, a leading independent PCA told the audience that a good NOW program included PTB control. Talk with your PCA and review reject sheets and moth traps to decide if PTB control is needed in your orchard. Dormant, delayed dormant, or bloom sprays (See this article about insecticides at bloom), with the proper pesticide, give effective PTB control when applied properly (every-row spraying and proper sprayer speed). Other effective timings include a spring or summer spray(s) timed using moth trapping data and degree days. Recently registered pesticides give excellent PTB control in research by Dr. Frank Zalom, UC Davis Entomology Department, in the Sutter/Yuba region (see table below). These materials are less toxic to operators and wild life, especially those that live in water. Consider these new materials as part of a PTB control program in your orchards. Organo-phosphate pesticides (Lorsban, diazinon, etc.) and pyrethroids (Asana, Warrior, Brigade, Baythroid, Mustang, etc.) are very effective on PTB, but can harm fish and other life in local streams if the pesticide moves to the water in drift or water runoff from rain or irrigation. Including a new pesticide in your PTB program in dormant to bloom also helps avoid pest resistance to organo-phosphates and/or pyrethroids.

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David Doll3 CommentsSeptember 8, 2009Insects

Taking a harvest sample for orchard IPM check-up

The collection and crack-out of a harvest sample is often forgotten during the bustle of the harvest. It is, however, one of the most important practices to employ as it provides a “progress report” of your season’s IPM program. A sampling of 500 nuts from orchard blocks that underwent differing pest management practices should be collected after shaking but before sweeping. These nuts can be stored in a refrigerator for 2-3 weeks until time is available to shell the kernels and inspect for insect damage. This sample will indicate what pests are in the orchard to help determine the management activities for the next year. Furthermore, it will serve as a record to compare with the huller/processor grade sheet. Insects that cause economic damage to almond kernels include navel orange worm (NOW) (Picture 1-2), ants (Picture 3), oriental fruit moth (OFM) (Picture 4), and peach twig borer (PTB) (Picture 5), and leaffooted plant bug (Picture 6). NOW actively chews and bores through kernels, often leaving behind webbing and excessive white frass. Ants feed on the kernel skin and can hollow out kernels, leaving behind piles of “sawdust” like frass. The OFM and PTB cause similar damage on almonds, causing shallow grooves on the kernel. The only difference is that OFM leaves behind small amounts of reddish brown frass. Damage by the leafooted pant bug is noted by dark spots on the kernels. Picture 1: Navel Orange Worm Damage to a mature almond. Picture 2: Webbing and excessive frass left by navel orange worms. Picture 3: “Sawdust-like” frass left by ants. Picture 4: Damage by Oriental Fruit Moth. Note the reddish frass left behind. Picture 5: Peach Twig Borer damage found on almond kernels. Note the lack of frass and shallow grooves. Picture 6: Darkened spots caused by the leaf-footed plant

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David Doll7 CommentsAugust 3, 2009Insects, Irrigation

Shothole borer damage on Almond – Varietal Differences in Response to Water Stress

The water crisis on the West side of the valley has presented opportunities to see problems not typically observed in almond production. Many of these issues tend to be directly related to tree stress caused by lack of water, failure of salt leaching due to decreased winter rains, and chronic water stress from prolonged drought. Typical observations of drought stressed trees range include yellowing leaves and leaf drop in mild cases, wilted new growth during moderate stress periods, and poor crop set, thinned canopy, and scaffold die back in chronic cases. A visit was made to an Aldrich-Monterrey-Nonpareil orchard located near Los Banos, CA. All varieties were on Nemaguard rootstock. This orchard has been under moderate drought stress for the past two years as determined by the use of a pressure bomb. This year, the grower was again short on water and had to water at about 80% evapotranspiration rate for the season. The grower was concerned about clear gumming coming from multiple wounds on his trees. Orchard observations included those listed above for orchards suffering from chronic drought stress: poor vigor, thinned canopies, and reduced crop load. On the affected trees, gumming was seen extending form the graft union up to the scaffolds. The issue was predominantly found on Aldrich trees, with some strikes on the Nonpareil, and very few, if any, strikes on the Monterrey. Upon seeing the damage (Picture 1), it was very clear that it was shothole borer, Scolytus rugulosus, an insect that invades and lays eggs in the branches/trunks of stressed trees. Borer insects are able to push their eggs through the bark and into the tree. A tree that is healthy enough to elicit a response then gums profusely in order to flush the egg out of the tree’s tissue (Picture 2). This gum

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David Doll1 CommentJune 27, 2009Insects

Hull Split is Approaching…

Hull split is approaching the the central San Joaquin Valley. In Kern COunty, hullsplit of almonds has been observed on the edges of blocks and tops of the trees, and will progress rapidly from this point forward. Hullsplit is a traditional time of making an application of insecticide to reduce navel orange worm damage and late season mite pressures. Blanks, or unpollinated or aborted fruit, will split first before the rest of the crop. So, as a grower, what do we need to keep in mind during hull split? 1. Insect pest management, which includes Navel Orange Worm and Spider Mites. 2. Water Management to reduce the incidence of hull rot. We will cover point 1 today, and the disease hull rot later this week. 1. Insect Pest Management practices for Hull split. Spider Mites: A miticide will be necessary if a pyrethroid was used within the orchard. Pyrethroids target both spider mites and predator mite populations. Once the predator mites are reduced, the faster reproducing problematic spider mites can flare up, causing tree defoliation. It is essential to include a miticide tank mixed if spraying a pyrethroid. If not using a pyrethroid, scouting the trees can give you an idea if you need to include a miticide. Scouting for mites is simple, should be done in the morning when it is cool, and can give a good idea about the ratio of predator mites to spider mites in your orchard. Please refer to the University of California Integrated Pest Management page for information on how to scout for mites: UC IPM Scouting for Spider Mites. There are several miticides to choose from at hull split. The most commonly used include Acramite, Envidor, Fujimite, Kanemite, Oil, Omite and Zeal. Each of these products can be effective, depending upon populations of

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