July 2018

The past few years seem to have shown an increase in a critter that starts the season as a beneficial insect, and by harvest is a pain in the neck.  They’re an economically damaging pest of stone fruits, especially peach, nectarine and apricot.  Earwigs chew holes into ripening fruit and reduce fruit quality, harvestable yield and economic value.  The orchard environment is conducive to earwigs: irrigated ground, plenty of food, and humid cover. Once the fruit softens, they will enter not only through existing openings but will chew their own holes, leaving deep pits. Their feeding introduces bacteria and decay fungi that can render the fruit inedible.  Earwig damage is usually easy to diagnose because they leave behind black dots of excrement (frass) on the fruit surface.

The adult earwig is readily identified by a pair of prominent appendages that resemble forceps at the tail end of its body. Used for defense, the forceps are somewhat curved in the male but straighter in the female. The adult body is about 3/4 inch long and reddish brown. Most species have wings under short, hard wing covers, but they seldom fly. Immature earwigs look like adults except they’re smaller and lack wings.

 

Contrary to popular myth and despite their ferocious appearance, earwigs generally don’t attack humans, although they are capable of biting if trapped in clothing or sat upon.

Earwigs feed most actively at night and seek out dark, cool, moist places to hide during the day. Common hiding places are under loose clods of soil, boards, or dense growth of vines or weeds.  They’re often found inside peaches due to split pits or damage caused by birds or other bugs.

Female earwigs dig cells in the ground in the fall and winter where they lay masses of 30 or more eggs. Eggs hatch into small, light brown nymphs and remain in the cell protected and fed by their mother until their first molt. Second-instar nymphs may forage at night but still return to the nest during the day. Third- and fourth-instar nymphs are darker and forage on their own. Generally there is one generation per year.

European earwigs feed on a variety of dead and living organisms, including insects, mites, and growing shoots of plants. They are voracious feeders on soft-bodied insects such as aphids and insect eggs and can exert significant biological control under some circumstances.  European earwigs can cause substantial damage to seedling plants and soft fruit as well as to sweet corn.

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Stink bugs are generally native to our region and are notable examples of locally migratory insects that live on a broad complex of plant hosts. Principal hosts found along the orchard edge or resident within herbicide strips include mullein, mustard, dock, plantain, milkweed, mallow, morning glory, thistles, and vetch.

 

Adults usually migrate into the orchard once other host plants dry out. Irrigated tree fruit become very attractive to the stink bug complex during drought conditions, leading to late season feeding damage in pear, apple and peach orchards. Stinkbugs have a proboscis (mouth part) that acts like a hypodermic needle.  They pierce the fruit skin and draw out the cellular contents of the fruit flesh, leaving behind dry cell walls that appear as corking when peeled.

 

As you might suspect, stink bugs derive their name from the production of pungent and offensive chemicals released when they are disturbed. Relatively mild winters and softer (more species specific) insecticide programs help in fostering their overwintering success.

 

It’s important to note that stink bug feeding differs dramatically among stone fruit, apple and pear.  Catfacing injury to peaches by stink bug is very similar to that of lygus, another type of plant bug.  On apple, fruit damage appears as shallow, circular, light brown to white spongy pockets in the fruit flesh, usually from 3/16” – 3/8” in circumference, and 3/16”– 5/15” in depth. Stink bug feeding can easily be mistaken for bitter pit. Typical feeding injury tends to be on the stem end or sides of the fruit, as those parts of the fruit surface are easier for the insect to stand on, and most likely to be covered by foliage, which provides protection as the bug feeds. On apple, stink bug feeding and cork spot are distinguishable by several differences in the depressions on the apple surface. With stink bug feeding, the edge of the depression on the fruit surface is gradual instead of abrupt, as observed with cork spot. The corky flesh is always immediately beneath the skin in stink bug injury, and often separates from the skin. Stink bug injury always has a small puncture near the center of the feeding depression.  You’ll need to have a magnifying glass! 

 

Stink bugs are very difficult to manage for a number of reasons. They have a broad host range, including many crops and broadleaf weeds. They are highly mobile, frequently moving between weed hosts and fruit trees. They tend to be more active in the evening and during the night. Insecticide applications made during the day may not come in direct contact with the insect, which reduces the effectiveness of the materials.  The classes of insecticides that have good activity on stink bugs are pyrethroids and neonicotinoids.

 

Stink bugs are fast and good at hiding.  They will move to the backside of a limb or fruit as you approach.  Take an early morning walk when it’s cool and they aren’t moving as fast, look inside the dense parts of the tree.  If you have a lot of alfalfa and/or other legumes as part of your cover crop, take a close look there.  Use a sweep net if you have one. Plant bugs like legumes!  Don’t let your cover crop dry out!!!

 

Greater peach tree borer aka crown borer is easy to overlook since it doesn’t show up at harvest by damaging fruit.  Instead it shows up slowly during the summer as weak and stressed or dying trees.  Make sure it’s part of the “list” of things you look for as you walk the orchard.  Inspect for damage at the soil line.

 

Pheromone mating disruption is the most common and effective means of controlling this pest in our area.  Mating disruption does have limitations and you need to know them.  If trunk drenches are your choice of control use a material with maximum residual and efficacy.  Adult emergence usually occurs in late June to early July.  Trunk sprays need to be applied shortly after this emergence.   One treatment will probably not protect you for the season. This moth has an extended emergence and flight time.  Using traps (in a non-disrupted block) will allow you to monitor the population in your orchard.

 

Calcium is an extremely important mineral in many plant processes:

·         maintains the strength of stems and stalks

·         regulates the absorption of nutrients across plasma cell membranes

·         functions in plant cell elongation and division

·         functions in plant structure and permeability of cell membranes

·         nitrogen metabolism

·         carbohydrate translocation

Calcium is a secondary nutrient even though the concentration of calcium in the plant is as great as nitrogen or potassium. Calcium is nontoxic, even in high concentrations, and serves as a detoxifying agent. Calcium is a critical component of the cell wall and acts as the cement that binds the cell walls together. Calcium is one of the most significant factors of firmness with a direct correspondence to the storage and shelf life of fruit. Seed viability is also directly related to calcium concentration.

 

Calcium deficiencies can be observed as bitter pit in apples, blossom end rot in tomatoes and chilies, leaf tip burn in lettuce, internal brown spot in potatoes and softer, non-marketable fruit. In general, shorter fruit shelf life.

 

There are several causes of calcium deficiency that show up in fruit and vegetables even though soil and weather conditions seem perfect. With the application of nitrogen fertilizers, nitrogen is moved through the pipeline in the plant approximately 20 times faster than calcium. Calcium is the slowest moving nutritional mineral in the plant. High amounts of nitrogen are frequently applied in an attempt to maintain yields. This large nitrogen boost causes the plant to grow faster than the calcium can move within the plant, thus inducing calcium deficiencies in the growing points and fruit. A second reason for calcium deficiency is the passive movement of calcium through the xylem (water conducting tissue) by transpiration. Leaves have a much higher rate of transpiration than fruit, causing a lower calcium concentration in the fruit. This makes leaf calcium concentrations and appearance a poor indication of calcium levels in the fruit. One can have adequate or even high concentrations of calcium in leaf tissue analyses and still have calcium deficiencies in the fruit.  On fruit that is sensitive to calcium deficiency, start early with calcium applications (pre-bloom) and continue through the season with as many applications as you can manage.

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