David Doll2 CommentsSeptember 22, 2011Insects

Late Season Leaf Defoliation due to Web Spinning Spider Mites

A few farm visits and phone calls have been coming in over the concern of late season spider mites. In these orchards, mite populations have flared up, causing defoliation. These growers have been asking is they should spray for mite control. As always, the answer depends, but here are some thoughts to consider when making this decision: 1. Since harvest has been delayed, and many trees have experienced longer periods of water stress than normal. Tree stress attracts mites, which creates hot spots within weaker areas of the orchard. 2. Tree defoliation caused by mites rarely causes significant effects on next year’s crop. If defoliation occurs, some leafing out may be triggered by an irrigation. It is still advised to apply a post harvest irrigation even if the tree is defoliated. Damage is more significant on younger trees as loss of leaves in the fall reduces the amount of overwintering carbohydrates. 3. An application of a miticide should only be made in attempts to curb the population until cooler weather. In many cases it is not possible to control a flare up, but rather the application “buys time” until cooler temperatures/ less stressful conditions arrive. An application should be considered if the “hotspots” are starting to defoliate and the mites are moving outward into the orchard. 4. If mites are present, but very little defoliation is occurring, the best strategy is to “wait it out.” Some later season defoliation may occur, but the “damage done” would be minimal, thus not worth the time and expense of the spray. 5. Miticides to apply should target the adults stage. These include the products Acramite (bifenazate), Vendex (Fenbutatin-Oxide), and Desperado (Pyridaben/Sulfur). 6. It is very difficult to get effective coverage with a miticide spray due to the hydro-phobic nature of the webbing. Drive slow and use the proper rates

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David Doll0 commentsJuly 14, 2011Insects

Timing of Hull-split sprays for Navel Orange Worm

Written by Walt Bentley, UC IPM Specialist, San Joaquin Valley. Hullsplit of Nonpareil almond, the most susceptible cultivar to navel orangeworm (NOW), is almost 2 weeks behind schedule in the central San Joaquin Valley.  Interestingly, the development of the second generation of NOW is not behind schedule with eggs being laid during the first week of July (see figure below).  This presents an interesting situation.  I believe many of these eggs will result in suicidal emerging larvae, not being able to infest the nut meat until hullsplit occurs.  This, however, doesn’t mean we are home free concerning NOW infestation.  It points to the importance of timing sprays to the development of the susceptible stage of the nut (initiation to 5% hullsplit).  Such timing will optimize the effects of any insecticide applied with the residual remaining through the complete second generation egg laying.  I believe a good portion of the early second generation eggs will hatch and be unable to infest the nut.  The remainder of the generation, that can reach the nut meat, will be shorter in time duration than normal.  If sprays are timed correctly, excellent chemical control should be achieved.  The same scenario that could optimize control of NOW in Nonpareils may result in making later splitting varieties such as Carmel, Sonora and Price more susceptible.  This is a scenario that we see from time to time.  Here the third generation eggs may be timed to Carmel hullspit resulting a greater potential for infestation.  Try to focus on early harvest of any late soft shell variety.  It may still be a good idea to monitor egg traps to see how NOW egg laying coincides with the hullsplit of these later soft shell varieties.  This can give you an idea if additional chemical control may be needed. 

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David Doll0 commentsJune 3, 2011Insects

Diagnosing Leaffooted Plant Bug Damage – Video

Still working out a few glitches with taking and editing videos, but here is the latest edition focusing on the identification of damage caused by Leaf Footed Plant Bug. More information regarding control can be found at the UC IPM website. Also note that a new chemistry, Clothiandin (trade name Belay, Valent) has been registered and has been reported by a few independent consultants to do a good job in knocking down adult populations. Being a second generation neonicotinoid, it has been reported to reduce disruption of some beneficials within the orchard systems in comparison to pyrethroid insecticides. Enjoy!

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David Doll2 CommentsJanuary 11, 2011Horticulture, Insects

Bee Health and Pollen Sourcing: Does mixed source pollen improve bee health?

A study conducted by Ramesh Sagili at Oregon State University looked at pollen sourcing and the effects on bee health. In this study, equal amounts of single-source pollen and multi-sourced pollen were packed into the comb cells of six frame hives. Each week, 100 newly emerged paint bees were introduced to the hive, while 20 nurse bees were removed from the colony for a protein estimation of the hypopharyngeal gland. This gland produces special food that is necessary for the development , metamorphosis, and pupation of the larvae. They also measured the brood area occupied by the eggs, larvae, pupae, pollen, and honey. Figure 1: Mean hypopharyngeal protein content of 20 nurse bees. What did they find?Analysis of the hypopharyngeal gland protein content yielded interesting results. Not only did they find a statistically lower gland protein content within the single-source pollen packed hives(Figure 1), but they also detected statistically lower amounts of crucial enzymes within the proteins isolated from single-source pollen packed hives (Figure 2). Differences brood size was also apparent; colony growth measurements were significantly lower within the single-source pollen packed hives (Figure 3). So what does this mean? Figure 2: Concentrations of two enzymes found within the hypopharyngeal protein of 20 nurse bees  Findings from this study suggest that pollen from a diversity of sources will benefit hive health. Beekeepers should keep this in mind when determining the feeding regime for the hives. It doesn’t stop there, however, as growers should attempt to incorporate alternative pollen sources within their orchard system to help increase hive health. Strategies may include placement of hives next to hedgerows or vegetative strips, or leaving an area of clover, or some other cover crop, un-mowed during and after the pollination period. It would be best to leave the un-mowed area outside of the orchard

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David Doll2 CommentsNovember 16, 2010Diseases, Insects

Preparing for the Dormant Period

Just returned from a field day meeting held near Firebaugh discussing pest and disease management strategies for the upcoming dormant season. I thought I would highlight a few points from the talks by Walt Bentley (UC IPM), Mario Viveros (Emeritus UCCE Farm Advisor – Kern County), and myself – David Doll (UCCE Farm Advisor – Merced County). I apologize for the brevity of the entry as I am preparing for a field trial due to be fumigated next Monday. Navel Orange Worm (NOW): Winter sanitation is critical to help reduce the overwintering population of NOW. In general, no more than two mummies per tree should be left in the tree. With some growers, complete removal of the mummies is performed. Most growers remove mummies. This is easily done on younger trees. As the trees mature and become larger in size, the task of sanitation becomes difficult, resulting in more mummies remaining within the upper canopy. This may explain why many growers see more NOW damage in mature blocks. Even though the trees may appear to be clean, a closer look usually reveals mummies still hanging in the tree. Peach Twig Borer (PTB): Scouting for hibernacula should be performed. There are several treatment options and timings for PTB. These include dormant oil sprays, bloom sprays with reduced risk products, and May sprays. See the PTB page on the UC IPM website for more information. Mites: European Red Mite and Brown Almond Mite will overwinter as eggs around the base of spurs. Spur sampling, which should also be done for scale, can help determine if treatment is needed. An oil spray outlines at the Mite page on the UC IPM website will suffice for most locations. Scale: The dormant period is the easiest time to treat for scale. Spur sampling can help determine the treatments needed. Check here for

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David Doll0 commentsAugust 24, 2010Insects

Collecting a Harvest Sample – Is It Worth It?

Taking a harvest sample is simple, but time consuming. Never-the-less, it should be done because damage is hidden by the handling that occurs during sweeping, pickup, and processing. In some cases, we have found 4% more damage in harvest samples than what was indicated in the grower’s processor report.  In other words, when we found an estimated 5% damage/reject level in the harvest sample, the processor indicated a 1% rejection level. The 4% discrepency is most likely due to damaged nuts lost during the steps of harvest. Another reason for performing a harvest sample is to account for the damage that does occur in the field. Often times processors lump all worm damage together, not separating out NOW, PTB, OFM, or other worms. Ant damage often does not show up because the chewed out pellicles are blown out the back of the pick-up machine. Gummy nuts due to deficiencies, feeding, or other conditions are all lumped together. Collecting a harvest sample is easy. In each block of concern, collect 500 nuts from the ground after shaking but before pickup and place them in a paper bag. Two samples of 250, or 4 samples of 125 nuts from differing areas of the block can also be collected, but try to keep the total number of nuts per block at 500. Store the bags in a freezer until they can be cracked out. Once able to crack out the almonds, check for signs of pests and disease. Pictures of damaged nuts can seen in a previous post or at the UC IPM website. A hand-sheller can be helpful in processing many samples. It can take 60-90 minutes for each sample depending on size. 500 nuts split into 4 125 nut samples should suffice for a 40 acre block. So, is a harvest

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David Doll0 commentsJuly 26, 2010Insects

Pyrethroid v/s Reduced Risk product usage for Hullsplit/May Spray

A few people have inquired about the differences between spray product choices for worm control during Hull Split and/or “May” Spray. I thought I would highlight some of the thoughts that the UC has developed over the years regarding this decision. Some of this may be redundant, but hopefully some new points will be brought to the table. Which product is best?Determining which product is the best treatment option for your orchard depends on budget, pest pressure, timing, and familiarity. Pyrethroid products are effective in knocking down adult moths and killing larvae that come in contact with the product. Persistence of the product within the field is not as long as the reduced risk products (about 2-5 days less), but they are useful for later hullsplit applications – around 2-5% for optimal timing. The downside with pyrethroids is the assumed mite flare up, knock down of orchard beneficial insects, and water run-off issues. A miticide should be tank mixed with the hull-split application if applying a pyrethroid. “Reduced risk” products (i.e. Entrust, Success, Delegate, Intrepid, Belt, etc.) target the eggs and larvae of the moths. They do not knock down adult populations as well as pyrethroids, but control developing larvae more effectively and selectively. These products tend to persist within the orchard a little longer, providing longer control and thus can be applied earlier than pyrethroid products (when blanks split). They have a minimal effect on beneficials, allowing the natural predators to help control mite populations, usually preventing a mite flare up, thus not requiring the tank mixing of a miticide.  These products are very effective but resistance to the mode of action may occur – so chemical class rotation is important if products are sprayed more than once per season. Water impacts appear to be minimal. Currently, a pyrethroid treatment is cheaper

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David Doll2 CommentsJuly 12, 2010Insects

2010 Hull Split time…

I feel that the majority of topics regarding hull split have been discussed in prior entries, so I thought I would briefly make a few points of considerations for 2010: 1). Navel Orange Worm (NOW)/ Peach Twig Borer (PTB): Both insects cause damage to almonds, often NOW damage hiding PTB damage. Both insects are susceptible to the same insecticides. The 2010 treatment window for the 2nd flight of PTB will be overlapping with hullsplit. This is good because we can make one spray for NOW and PTB. This is bad because in years were the 2nd PTB flight occurred during hullsplit, worm damage was higher.  If no PTB treatments have been made and no NOW/PTB treatments are scheduled, I would plan to make one within the coming week. Reduced risk products or pyrethroids will provide control for both worms. Related topics previously covered: Peach Twig Borer, Navel orange worm, and hull split insect management. 2). Apply pesticides slowly – do not exceed 2 MPH with spray rigs. 3). Hull rot: Hopefully nitrogen applications have ended. Plan to reduce water to 80% ET for the coming two weeks. By the last week of July, first week of august, resume full ET. This will help reduce hull rot. Please see the previous article on hull rot. 4). Mites: Haven’t been much of a problem this year, but keep in mind that the use of a pyrethroid at hullsplit will most likely cause a mite flare up by harvest. A miticide should also be applied at hullsplit if a pyrethroid is used. There are a few products available that can knock down high populations of spider mites should a flair up occur. It is critical that these products are applied before webbing appears. 5). Harvest: Hullsplit appears to be a week later this year, suggesting that harvest will be

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David Doll2 CommentsJune 22, 2010Insects

Speed doesn’t kill: Slow down your spray rigs!

As we prepare for hull-split, I thought I would take a minute to discuss spray rig speeds. It is easy to hurry with the hustle of applying a hull-split spray on a large number of acres, but attention should be payed to the ground speed in which chemicals are applied. The University of California recommends applying your sprays at a ground speed of 2.0 MPH to ensure adequate height coverage and canopy penetration of the spray. This recommendation has been based on numerous studies using ground rigs at varying speeds applying a water spray to water sensitive paper placed within the trees canopy. Figure 1 shows data from a recent trial conducted by Joel Siegel (USDA-ARS) conducted in pistachio. Figure 1: Spray coverage of a ground rig applying a water spray to water sensitive cards at 3 different ground speeds. Spray coverage for almond trees is based on the height and density of the tree. For the most part, if the height of the tree is under 10 feet, adequate spray coverage can be attained at almost any reasonable speed. For taller orchards, however, this is not true. As shown in figure 1, the difference of a 1/2 mph (2.0 mph v/s 2.5 mph) can reduce the coverage by 30% for trees 18′ or higher. Traveling at 3.25 MPH, less than 2% coverage was achieved at a height of 20 feet. This reduction makes the pesticide applied lose its efficacy due to low concentration and basically renders the application useless. It also increases the chance of resistance formation, loss of crop due to disease/insect damage, and tractor/rig damage. Many people say that their rigs are better than the ones used in the study and therefore they can go faster. I would doubt that statement unless they can clearly demonstrate it

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