This article will discuss the redberry mite in blackberries, as the time to begin operations for its control is rapidly approaching.
Redberry mite is a serious pest of commercially produced blackberries in Santa Cruz and Monterey counties in California. Redberry mite activity prevents berries from ripening uniformly, causing from one to many druplets to remain as a bright red cluster on the otherwise black and fully ripe fruit. Affected druplets never do ripen, causing the entire fruit to be inedible and unmarketable.
Varieties of blackberry, such as Ollalieberry, which bear fruit in the early part of the season, from late May to the beginning of July, tend to have less redberry mite damage and are less of a concern. However, later bearing varieties such as Chester, Triple Crown, Navaho and Apache do get redberry mite and an absence of control can lead to significant losses.
Horticultural oils, such as Golden Pest Spray Oil, when used at the rate of 1.2 to 2% volume oil to volume water carrier, should begin to be applied after the blackberry reaches green fruit or when you see the first pink fruit. Follow the first application with two to three more applications, spaced 2 or 3 weeks apart. These applications will give significant control of redberry mite, while causing less harm to fruit yield than the traditional lime-sulfur or sulfur sprays.
The minimum amount of water carrier for oil applications should be 50 gallons per acre.
The potential for phytotoxicity of oil product or oil product mixes has not been fully evaluated for all blackberry varieties in all growing areas. Small plot tests are prudent to determine safety margins of particular blackberry varieties for specific environmental conditions in different growing areas.
There are several insecticides mentioned for control of redberry mite in this article. Before using any insecticides, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
Blackberry growers should note that the moderate rains taking place in ambient temperatures of 65 to 75 degrees F as they are now are excellent conditions for outbreaks of downy mildew. The most recent outbreak was in the spring of 2005 and resulted in significant yield reductions on susceptible varieties.
Downy mildew is caused by the fungal pathogen Peronospora sparsa. This pathogen infests almost all of the proprietary blackberry varieties, Ollalieberry, and is devastating to Boysenberry. Conversely, varieties such as Chester, Arapahoe, Apache, Navaho and the other so called “Native American named varieties” are fairly resistant, with very little disease appearing even in the most amenable conditions.
Downy mildew first appears as a yellow discoloration on the upper leaf surface, followed by a red to purple discoloration which is oftentimes framed and limited in growth by leaf veins, giving the lesions an angular appearance. These blotches will appear as light pink or tan areas on the leaf underside, often accompanied by whitish spore masses (see photos below). As favorable conditions persist and the disease advances, these lesions expand to cover the whole leaf, and eventually the whole leaf turns brown. Severely infested leaves may fall off the plant.
Infested flowers often result in fruit which is crumbly and not sound, while fruit infested with downy mildew at the green stage will shrivel and dry out. Fruit infested at the mature stage takes on a dull pallor, followed by similar shriveling and drying out. Downy mildew affected fruit will sometimes split into two parts.
The downy mildew pathogen is understood to overwinter as fungal mycelium in the plant roots, crowns and canes. As new shoots emerge in the spring, the pathogen follows the growing point, infesting stems and new leaves. Given the right conditions of moisture and temperature, these infested leaves are then the primary sites for further infestation of the plant.
Practices which limit the duration of periods of moisture around susceptible blackberries will reduce risk of disease. Removal of weeds and excess suckers around the base of fruiting canes allows more air circulation and may limit disease establishment and spread.
The dryness of covering hedgerows with macro-tunnels is unrivalled in reducing the incidence and severity of downy mildew disease in blackberries.
The fungicide often recommended for use in controlling downy mildew is Aliette (fosetyl aluminum) used as a foliar application. Growers planning on using Aliette should bear in mind the restriction of not being able to harvest fruit for 60 days after application of this material.
Although not fungicides, phosphorous acid fertilizers are successful in limiting downy mildew in blackberries. Growers should be certain that they are purchasing products containing phosphorous acid, as opposed to phosphoric acid which does not exhibit the same capability of limiting downy mildew. Additionally, all products sold as nutrient solutions must state the phosphorous content in terms of phosphoric acid equivalents, even if they only contain phosphorous acid. Products such as Phosgard, Nutriphyte and Fosphite all contain phosphorous acid.
There is a fungicide and several other products mentioned for control of downy mildew in blackberries in this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
With the potential of the new fruit fly, Drosophila biarmipes, to become a problem in the Watsonville- Salinas fruit production district, it is important for growers to know what they might do to control it. The pesticides Malathion and Pyganic offer a measure of control against adult flies, and will need to be applied frequently, meaning once every week to 10 days.
Another pesticide which has been used with significant success in other areas of the country suffering fruit fly infestations is GF120 Naturalyte Fruit Fly Bait. Since it is a bait, GF120 is used differently than other pesticides, and it is worthwhile reviewing this with applicators and growers.
Being a bait means that GF120 draws the target pest to it, instead of having the pesticide delivered to the pest. This means that coverage and distribution is far less important with GF120 than with regular pesticides.
Indeed, this is the case because in most cases the application rate of GF120 plus water carrier is less than one gallon per acre. Obviously, it will not be possible to apply GF120 with an airblast or rowcrop sprayer because the rate is so low. One must use equipment which can apply very low rates, such as the hand held sprayer pictured below, to apply this material. There are also automated sprayers in use in the Central Valley for olive fruit fly control specifically for application of this bait.
Distribution of GF120 means applying a spot (around 2-3 milliliters) of the material (see second photo below) over fairly widely spaced intervals in the field. In the trial conducted this past winter, it was found that every thirty feet on each side of a raspberry hedgerow was sufficient to reach the rate required by the label.
While there are no restrictions on the label concerning contact of GF120 with berry fruit, it is suggested to avoid contacting the fruit with the bait as it does not taste very good. In raspberries, spray to the base of the hedgerow some two to three feet off of the ground. This seems to be where most of the flies are found anyway, so this serves a second purpose. In strawberries, it is probably best to spray between the plants during the early part of the season when the canopy has yet to close and then towards the midtier where there is less fruit when the plants are larger.
Mixing of GF120 is important. While soluble in water, it takes significant agitation to go into solution, more so than most other pesticides. It is vital that GF120 be properly mixed, because unsuspecting applicators could end up applying the bulk of the active ingredient in the first run of the application and water on the rest. Additionally, it is very thick when not well mixed and clog the lines. Once properly mixed, it does not come out of solution.
Finally, the label for GF120 recommends re-application every one to two weeks, depending on weather conditions. Rain will wash the bait off and sun breaks it down over time. Our experience in macro-tunnels informs us that the bait lasts longer in the protection of the tunnels, but even so, it is advisable to re-apply every three to four weeks.
There are several insecticides mentioned for control of fruit flies in this article. Before using any insecticides, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
Please be informed that this year's Annual Strawberry Production Meeting for the Central Coast will be held on February 5 at the Elk's Lodge in Watsonville, the same place as last year.
Follow the link below for the announcement and agenda:
Raspberry sawfly, Monophadnoides geniculatus, is an uncommon pest in raspberries on the Central Coast of California. I recently had a question concerning this pest, so it something worth discussing.
Raspberry sawflies are not flies, but actually wasps. The larvae, since they are fixed on the leaves and damage them, draw our attention as pests. Larvae are usually found on leaf undersides, are ½ of an inch long, light green in color, and have a brown stripe down the back. Larvae generally occur in groups, so a closely spaced group of punctures and holes in the leaves should be a signal to look for raspberry sawfly.
Being very mobile, the adults are seen far less. The adult wasps are flattish and have a thick body roughly ¼ of an inch long. Female adults also have a yellow white band across the back of the abdomen.
In almost all cases, sawflies do not merit control, since in a light to moderate infestation, sawfly larvae will make a few holes in the leaves and not compromise fruit yield. However, more severe infestations, of the sort that we have not yet seen on the Central Coast, have the potential of eating all the leaves and seriously damaging the plant.
Probably the most important point of this writing is that growers do not confuse raspberry sawfly larvae with more damaging moth larvae, since chemicals used to control them can be different.