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Extension Entomology

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Alfalfa Update

— by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevils are cool weather insects, thriving when temperatures are between 50-75°F and thus mostly affect alfalfa prior to the 1st cutting. That has been the case for about the last two weeks in north central KS. Temperatures have been on the cool side and the alfalfa has not been growing as well as most producers would like.  However, alfalfa weevils have been very active to the point where there are many pupae and even pupal webbing with holes indicating the adult weevils have already emerged and dispersed.  Infestations as of 6 April were composed of very small 1st instar larvae to larger, more mature 3rd instar larvae, as well as pupae, and newly developed adults.  Also, lady beetle larvae were quite common in most alfalfa fields, but no aphids were detected.

Alfalfa weevil feeding damage

 

Alfalfa weevil feeding damage – close

 

Alfalfa Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Much of the alfalfa in northcentral Kansas that could be swathed has been in the last week.  The cool damp weather has kept the adult alfalfa weevils in the fields.  They are congregated under windrows in the cut fields where they do a little feeding on the stems, resulting in characteristic spots of epidermis removal, called ‘barking’.  As these windrows are picked up there will be the characteristic striping across the fields where the windrows held back the regrowth underneath, plus provided the weevils with a protected site to continue feeding.  Fields not yet swathed also have significant populations of adults but this should not impact the foliage prior to cutting.

AW adult and barking

Windrows

Pea aphids are also present in both cut and uncut fields, but lady beetles and green lacewings are also, so would not expect pea aphid populations to have a negative impact on alfalfa.

Pea aphids adult and nymph

greenlacewing

pinkspotted lady beetle

Sevenspotted lady beetle

Potato leafhopper adults are already present in all alfalfa fields we checked over the past week.  This is earlier than usual for these pests as they typically don’t migrate into the state for another month, between the 2nd and 3rd cutting.  Some of these populations already exceed the treatment threshold with just adults, so hatching nymphs will just increase the populations further.  These potato leafhopper populations need to be monitored throughout the rest of the growing season.

PLH adult and nymph

Winter Grain Mites

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

This time of year there is usually considerable interest in winter grain mites and this year is no exception.  A little refresher relative to winter grain mites:

  • Adults can be seen by the naked eye, but they are tiny.

winter grain mites_size

  • They have dark colored bodies with distinctive red legs and a red spot at the rear of their back, which is an anal pore.

Winter grain mite_close

  • There are 2 generations per year.
  • Adults will be actively feeding in the fall and spring and overwinter and oversummer as eggs.
  •  This feeding will continue as long as temperatures are cool (not cold), i.e. they are most active from 40°F to 70°F.

Feeding activities usually peak about this time of year and will cease during winter, when temperatures usually are just too cold.  This 1st generation deposits eggs in November and December and these eggs will hatch in late February to March.  This is about the time wheat is breaking dormancy, thus another time for grower concern.  Under dry conditions winter grain mite feeding may cause plants to take on a silvery appearance because mites penetrate individual plant cells and remove the plant juice, resulting in this silvery look.  Serious feeding, again in dry conditions, may result in yellowing of plants but, more commonly, just the tips. Under good growing conditions this feeding will not even be noticed.  Hot weather causes adult populations to quickly decrease.

Winter grain mite feeding

In summary, mite feeding activity will be terminated by cold weather in winter and hot weather in the spring, both of which cause eggs to be deposited into the soil to withstand the unfavorable conditions.  Winter grain mite feeding is only noticeable when wheat is under moisture stress, is reversed by adequate moisture, and rarely, if ever, results in any impact on yield.

Here Comes The Asian Ladybird Beetle!

–by Raymond Cloyd

This is the time of year when the Asian ladybird beetle, Harmonia axyridis adults start entering homes and becoming a nuisance. The Asian lady beetle is a native of Asia and was introduced into the southeastern and southwestern portions of USA to deal with aphids on pecan trees. However, the Asian ladybird beetle has spread rapidly to other portions of the USA. The Asian ladybird beetle is a tree-dwelling ladybird beetle, more so than the native species of ladybird beetles, and is a very efficient predator of aphids and scales.

Images1 (45)

During fall and early winter, when the weather is cooler, Asian ladybird beetle adults start aggregating on the south side of buildings and entering homes. The beetle does this because in their homeland of China they inhabit tall cliffs to overwinter. There are very few “tall cliffs” in Kansas—so the next best thing is a building.

The Asian ladybird beetle can be easily distinguished from other species of ladybird beetles by the presence of a pair of white, oval markings directly behind the head, which forms a black M-shaped pattern. Adults are 1/4 inch long, 3/16 inch wide and yellow to dark-orange colored. In addition, their body is usually covered with 19 black spots. Adults can live up to 3 years. Female beetles lay yellow, oval-shaped eggs in clusters on the underside of leaves. The eggs hatch into larvae that are red-orange and black in color, and shaped like a miniature alligator. The larvae are primarily found on plants feeding on soft-bodied insects such as aphids and scales. They eventually enter a pupal stage. Pupae can be seen attached to plant leaves. The adults emerge from the pupae and start feeding on aphids. Adults can be found on a wide-variety of trees including apple, maple, oak, pine, and poplar.

Asian ladybird beetle adults are a nuisance pest because they tend to aggregate and overwinter inside buildings in large numbers. The beetles release a pheromone that attracts more beetles to the same area. Although the beetles may bite, they do not physically harm humans nor can they breed or reproduce indoors. Beetles are attracted to lights and light-colored buildings, especially the south side due to the warmth provided when they bask in the sunlight. The beetles then work their way into buildings through cracks and crevices. Dark-colored buildings generally have fewer problems with beetles (so now is the time to paint your house). Adult beetles will feed on ripening fruit such as peaches, apples, and grapes creating shallow holes in the fruit. Large numbers of beetles feeding on fruit may cause substantial damage so that the fruit is less appealing for consumption.

Beetles may be prevented from entering homes by caulking or sealing cracks and crevices. Beetles already in homes can be physically removed by sweeping them or vacuuming. Be sure to thoroughly empty the vacuum bags afterward. Do not kill the beetles. Just release them outdoors underneath a shrub or tree away from the house. Commercially available indoor light traps can be used to deal with beetles indoors. The traps need to be placed near the center of a room and they are only effective at night in the absence of competing light. In addition, they work best when room temperatures are 75°F or higher.

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If crushed, the beetles will emit a foul odor and leave a stain. The dust produced from an accumulation of dead Asian ladybird beetle adults behind wall voids may incite allergies or asthma in people. Although there are some sprays available, the use of insecticides is not recommended for indoors.

Homeowners that want to avoid dealing with overwintering beetles entering their homes can hire a pest management professional to treat the points of entry on the building exterior with a pyrethroid insecticide. The treatments need to be made in late September or early October before the beetles enter the building to overwinter. Beetles that are feeding on fruit can be “controlled” with insecticides commonly labeled for use on fruit trees.

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