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Extension > Yard and Garden News > February 2013

Thursday, February 28, 2013

Pest Management Continues to Evolve - Biological Controls

Karl Foord - Extension Educator, Horticulture

At a recent conference on high tunnel horticulture we received an update on biological control from Carol Glenister, the president of IPM Laboratories. IPM Laboratories supplies and supports the successful use of healthy beneficial organisms for the biological control of pests.

nhm ac uk

Photo 1: Parasitoid Wasp Encarsia formosa

ipm UC Davis

Photo 2: Parasitoid Wasp Encarsia formosa

Encarsia Biological Services AU

Photo 3: Life cycle of parasitoid wasp Encarsia formosa

Forestry Images

Photo 4: View of a leaf surface with evidence of parasitoid wasp Encarsia formosa activity

Photo 5: Parasitoid wasp Eretmocerus spp.

Photo 6: Small lady bird beetle Delphastus spp.

Carol has coined the term "guardian plants" that function in the following ways: 1) are more attractive to the pest species than the crop being grown i.e. 'indicator' or 'trap' plants, 2) provide forage for natural enemies of the pests i.e. 'habitat' plants, and 3) provide forage for non-pest prey species that serve as an additional food source for natural enemies or serves as a reproductive site for natural enemies i.e. 'banker' plants.

Biocontrol Cornell

Table 1: Parasitoids

The indicator plants let you know the pest is present and the habitat and banker plants provide resources that encourage the natural enemies to remain and thrive on site.

Biocontrol Cornell

Table 2: Predators

Biocontrol Cornell

Table 3: Pathogens

In natural populations the predator numbers shadow the prey numbers, but the prey species always reproduce more rapidly so there is often a delay in control. If the control comes after the prey has damaged our plants then the predator hasn't benefited our production system. If the two-spotted spider mites are finally controlled by the predatory mites but your tomatoes performed poorly during the battle, there is little cause for celebration. The key is to have predator numbers in sufficient quantity early in development to keep prey damage below an acceptable threshold.

This means knowing what pest you expect to encounter, placing the proper indicator plants, monitoring for pest activity, getting predator species in a timely fashion, providing habitat plants and tracking pest and prey activity and numbers.

Natural enemies such as the following are presently being used to control whiteflies in greenhouses; two parasitoid wasps (Encarsia formosa Photos 1 - 4, and Eretmocerus eremicus Photo 5), and a small lady bird beetle (Delphastus catalinae) Photo 6. Note the incredibly small size of these insects - less than 1 mm in length.

In one experiment Lantana was used as a guardian plant among herbs such as oregano and lemon verbena, and the Encarsia formosa wasp was used as the prey species. The ratio of whitefly pests found on Lantana to those on the herbs was 79 to 1. The whitefly pest was drawn to the trap plant where it met its demise at the "hands" of the Encarsia wasp. This experiment can be viewed in greater detail at

There is a great deal of research being conducted in this area, especially on the functioning of these bio-control organisms in outdoor environs. Consider the number of organisms functioning as parasitoids, predators, and pathogens as noted in Tables 1 - 3.

This is a fascinating research arena and one worth tracking advancements.

Friday, February 1, 2013

February 1, 2013 Issue

In this month's issue:

Tomato Blossom End Rot - Facts & Control

Pavement Ants in Homes During Winter

Tomato Blossom End Rot - Facts & Control

Karl Foord - Extension Educator, Horticulture

In anticipation of spring tomatoes, please consider your tomato systems and avoid one of the scourges of gardening - tomato blossom end rot.

Michelle Grabowski

Photo 1: Blossom End Rot

Michelle Grabowski

Photo 2: Blossom End Rot

Symptoms of blossom end rot

Water soaked areas at the blossom end of the fruit usually appear when the fruits are one third to one half full size (Photo 1). This enlarges and darkens as the fruit matures (Photos 2 & 3).

Michelle Grabowski

Photo 3: Blossom End Rot

These large sunken lesions dry out flatten and become black and leathery. Typically the first fruit are most severely affected, and later developing fruit can be unaffected.

Causes and the role of calcium

Blossom end rot is a "physiological disorder" induced by a localized calcium deficiency in the fruit. The incidence of the disorder is usually not due to a lack of calcium in the soil, but rather due to factors affecting the uptake and translocation of calcium.
On a cellular level calcium is a critical component of cell walls (a structural nutrient). So when calcium is limiting cell walls cannot form properly and rapidly growing parts of the plant suffer breakdown. As a structural component calcium once incorporated into a cell wall is not mobile within the plant.

At the plant level, the end of the fruit is an area of rapid growth and has a high need for calcium as do other rapid growth areas like meristems. If 90% of the calcium that a mature fruit contains is already in the fruit by the time it is ½ - ¾" in diameter then the critical time for calcium uptake is early in the development of the fruit.

Soil calcium and plant uptake

Calcium uptake is associated with water uptake. Thus anything that interferes with water uptake can create calcium deficiencies. Dry or wet soils interfere with water uptake in different ways but both can lead to calcium problems. The strongest sink for calcium is actively transpiring leaves because they are actively pulling water. Other plant structures are not transpiring near the degree that leaves are and thus function as poorer calcium sinks. A waxy cuticle develops on the fruit when it is ½ - ¾ "in diameter which reduces transpiration and thus weakens the fruit as a calcium sink.

The fruit is competing with leaf tissue for calcium so a higher fruit to leaf ratio reduces the relative strength of the leaf as a calcium sink allowing more calcium to be allocated to growing fruits. This adds to the logic recommending pruning of tomato sucker shoots.

Control of Blossom End Rot

Maintain even and adequate soil moisture; mulch aids in this process. Avoid poorly drained and cool soils. Avoid over- fertilizing with nitrogen which creates excessive vegetation. Avoid ammonium based fertilizers as ammonia inhibits uptake of calcium. Use nitrate as the main source of N in fertilizers. Choose cultivars that have fewer tendencies to demonstrate blossom end rot. Use soil test data to maintain proper nutrition and optimum pH in the 6 - 6.5 range.

Foliar applications of calcium

There seems to be disagreement about the effectiveness of foliar applications of calcium. The logic on the ineffective side is that calcium is immobile in the plant and will not translocate to the fruit from material sprayed on the leaves. The response is to spray on the fruit. However, a waxy cuticle develops on the fruit when it is ½ - ¾ "in diameter which reduces transpiration and perhaps direct absorption of sprayed calcium.

Often blossom end rot decreases as the season progresses. This could be due to weather effects, warmer soils, or a slowing of vegetative growth all of which would make it appear that early applications of calcium have been effective.

Perhaps foliar sprays applied on plants prior to the first cluster of fruit or directly on small fruit can be used to supplement calcium. Calcium nitrate and chelated calcium are the safest sources of calcium to be applied as a spray. However spray applications of calcium are no substitute for proper nutrition and water management.

If calcium is best allocated by the plants xylem water conduction system, then keeping this system functioning optimally is the best course of action.

Editors note: This article was developed from a presentation created by Dr. Carl Rosen and Michelle Grabowski and delivered by Dr. Carl Rosen at the Upper Midwest Regional Fruit and Vegetable Growers Conference.

Pavement Ants in Homes During Winter

Jeffrey Hahn, Asst. Extension Entomologist

Winter is not a time when you typically expect to encounter ants in your home. However, it happens more often than you might think. One of the more common ants found in homes and other buildings is pavement ants. This ant is 1/8th inch long and is reddish brown, although it can range in color from light brown to dark brown to almost black. With magnification you can see that this ant has a two-segmented petiole (the waist between the thorax and the abdomen) and two short spines projecting from the thorax.

Jeff Hahn

Photo 1: Pavement ant worker. Note the two-segmented petiole and two small spines on the abdomen.

Pavement ants like to nest in the soil under or besides objects, such as stones, bricks, sidewalks, and driveways. They can also nest under the concrete slabs of homes as well as in wall voids. They typically nest near a heating source which allows the ants to be active during winter. They can follow pipes that go through slab to move up into the living quarters of homes thorough expansion joints, under baseboards and floor registers. Sometimes large numbers of winged pavement ants are found which are the reproductives of the colony, i.e. females and males.

Pavement ants can infest foods; they like protein and grease, such as meats, cheese, dead insects, dry pet food, and peanut butter, as well as a variety of sweets. Other than that, pavement ants are mostly annoying and are not particularly damaging to homes.

If you are finding pavement ants in your home, try to determine from where they entering. If you can determine they are moving through a crack, e.g. in an expansion joint, try to seal it to help keep pavement ants out. If you are not able to find how they are getting into your home, then try baiting them.

Jeff Hahn

Photo 2: Pavement ant swarmers can be sometimes seen indoors. They are just a nuisance.

Select a bait that is effective for grease feeding ants and place it where you are commonly finding them. Don't be surprised if there is an increase in the number of workers that are around the bait. That's good, the more ants that take bait back to the nest, the more likely you can eliminate it. Don't spray the foraging workers. It doesn't have any impact on the colony and will also lessen the ability of the workers to take bait back to the nest.

If you are not successful in your efforts to get rid of pavement ants or you would rather have someone control them for you from the start, talk to a professional pest management service about treating your ants.

Not all ants found indoors during winter will be pavement ants. People can also potentially see carpenter ants, Pharaoh ants, yellow ants, and thief ants in their homes during the winter. Their habits differ as do the methods for treating them. If you have any doubt as to what kind of ant problem you have, get them identified them by an expert.

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