— by Dr. Jeff Whitworth and Dr. Holly Davis
Last week’s newsletter included the links to the 2018 KSU Insect Management Guides except we inadvertently omitted the 2018 Sunflower Insect Management Guide, which can be found here: https://www.bookstore.ksre.ksu.edu/pubs/mf814.pdf
— by Dr. Jeff Whitworth and Dr. Holly Davis
Very small grasshopper nymphs were first detected this past week. Grassy areas, waterways, and field borders will have the small grasshoppers first and thus should be monitored weekly to determine grasshopper densities.
— by Dr. Jeff Whitworth and Dr. Holly Davis
Most alfalfa monitored in north central Kanas in the last week has started flowering and swathing seems to be well underway. Alfalfa weevil infestations, which we sampled throughout NC KS, never did exceed an overall 30% infestation level (using the cut stem bucket shake method). This year, any time larval numbers started increasing, a sub-freezing cold spell came through and killed many newly hatched larvae.
Since alfalfa fields were not treated for alfalfa weevils they are currently a great place for many beneficials. Uncut fields sampled in the last week had healthy populations of pea aphids as well as a few spotted alfalfa aphids.
However, as beneficial populations increase, these aphid populations are rapidly declining. Presently there are many lady beetles, both larvae and adults, and more adults will be active very soon as there are also many pupae. There are also significant numbers of parasitic wasps parasitizing these aphids as indicated by many mummies.
Additionally, there are a few green lacewings present. All this beneficial insect activity results in aphid populations declining significantly in the fields we sampled. On 11 May, pea aphid populations averaged 50-60/stem, dropping to 6-7/stem on 16 May. Hopefully, after swathing, the beneficials will still be present in sufficient numbers to continue providing aphid control but fields should still be monitored. For more information relative to alfalfa insect management, please refer to the 2018 Alfalfa Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf809.pdf
— by Dr. J.P. Michaud — Hays, KS
In 1982, Stroyan distinguished a subspecies of Metopolophium festucae, sensu stricto, as M. f. cerealium based on morphological characters. Whereas the former subspecies infests various wild grasses and is only incidental on grain crops, the latter is a potentially significant pest of cereals, especially wheat. Although this aphid complex has been present in North America since the 1970s, it was not until 2011 that significant M. f. cerealium infestations of wheat (as well as barley and oats) were discovered in the Pacific Northwest. The winged adults are pale yellowish with dark markings on the dorsal surface (Fig. 1), whereas apterae are pale yellow, similar in color to sugarcane aphids, but with a more elongate body shape (Fig. 2).
Fig. 1
Fig 2
On the morning of May 17, 2018, we collected a number of winged M. f. cerealium using a sweep net in wheat plots on the Agricultural Research Center-Hays. Other aphids present included Sitobion avenae and Rhopalosiphum padi, but all three species were present in low numbers, and were attended by the usual complex of aphid predators. It should also be noted that apterous M. f. cerealium were not found, so the winged forms are most likely very recent migrants. It is quite possible that existing biological controls will maintain this new aphid below economic levels along with all the other species present in wheat, but farmers should be vigilant for possible outbreaks in particular fields, especially later-maturing varieties that will give the aphids more time to feed and increase their numbers. It is also possible for these aphids to move to spring oats and barley after winter wheat matures.
— by Dr. Raymond Cloyd
It is time to be aware of the presence of pine tortoise scale, Toumeyella parvicornis, on pine trees. We have already received samples of pine tortoise scale with the crawlers (nymphs) emerging from the eggs. Pine tortoise scale feeds on many different types of pines, including: Scots, Austrian, and red. Immature females are round, brown, and wrinkled in appearance (Figure 1),
Fig 1. Pine tortoise scale on branch of pine tree (Author–Raymond Cloyd, KSU)
and overwinter on twigs (Figure 2).
Fig 2. Pine tortoise scale females on the twig of a pine tree (Author–Raymond Cloyd, KSU)
Eggs are laid underneath the body of adult females. In general, eggs hatch into red crawlers (nymphs) from May (RIGHT NOW) through June (Figure 3).
Fig 3. Pine tortoise scale crawlers emerging from eggs of females (Author–Raymond Cloyd, KSU)
The crawlers eventually find suitable locations and start feeding. Crawlers can spread to other pines via wind currents or by attaching to birds. Females can produce up to 500 crawlers within a generation. Males, like most scale species, develop into winged individuals that fly and mate with females. Males do not feed and eventually die. In Kansas, there is typically one generation of pine tortoise scale per year.
Pine tortoise scale feeding results in yellowing of needles, stunted needle growth, and under extensive populations can result in death of pines. Young pine trees, in general, are more susceptible to pine tortoise scale than older (mature) trees. In addition, foliage closer to the ground tends to support higher populations of pine tortoise scale than foliage higher in the tree canopy. Pine tortoise scale also produces copious amounts of honeydew, a clear sticky liquid that serves as a growing medium for black sooty mold. Entire pine trees may appear black from black sooty mold under heavy infestations of pine tortoise scale.
A forceful water spray applied twice per week will quickly dislodge/remove the crawlers and mature females from infested pine trees. Insecticides that are useful in suppressing populations of pine tortoise scale crawlers include: acephate (Orthene), acetamiprid (TriStar), bifenthrin (Talstar), cyfluthrin (Tempo), dinotefuran (Safari), imidacloprid (Merit), insecticidal soap (potassium salts of fatty acids), and horticultural oils (petroleum, mineral or neem-based). These insecticides must be applied when crawlers are active…which is RIGHT NOW…in order to obtain maximum suppression of pine tortoise scale populations and alleviate future problems.