Indiana Department of Natural Resources sent this bulletin at 05/11/2022 07:41 AM EDT
Weekly Review for May 11, 2022
This informal report by the Division of Entomology & Plant Pathology is a commentary on insects, diseases, and curiosities division staff encounter on a week-to-week basis. Comments and questions about this report are welcome and can be sent to your respective Inspector.
The weather was still cool and rainy but I did inspect a couple more greenhouses. The diseases I am seeing are Botrytis on geraniums, impatiens, Begonia, and New Guinea Impatiens. Powdery mildew showed up on dahlia and roses. The insect problems were the typical ones I see, such as thrips on sweet potato vine, spikes, petuia, and verbena. Aphids were on eggplant and roses.
One of the things I enjoy doing is talking to elementary school kids about insects, and I have done several talks over the last couple of weeks. Besides talking in general about insects and invasive insects, I take some samples of insects that have been processed for human consumption. I give the classes a chance to sample them, and usually most the kids will give it a try. In a couple of classes they even convinced their teachers to give it a try!
I finally found spongy moth egg hatch at Richland Center. That puts us about two weeks behind normal, but with a forecast full of 80-degree days things should catch up pretty quickly. The current plan is to treat our Btk sites May 19, weather dependent. Check out our website or Twitter account for updates and details.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
I have not seen many pests in the landscape or nursery environment so far this year. I observed one small population of eastern tent caterpillar, but for some reason I have not seen large amounts of this pest in my region in years. One interesting thing I have observed is reduced flowering in dogwoods this year. This is occurring in both the landscape and wooded areas. Not every dogwood is affected, but many seem like the are only flowering at about 50% of what they normally are. I have also observed reduced flowering on Fothergilla and serviceberry on my property. Yoshino cherries and Japanese weeping cherries seemed to bloom nicely this spring. I am thinking that the 73-degree temperature between Christmas and New Year’s may have affected the flowering of these trees.
During the past week I have primarily inspected greenhouses. Even the greenhouses have not had many pest issues so far. I have not observed any thrips activity during my inspection and only a few instances of aphids. Look for leaf curl and aphids feeding on the undersides of new growth. Remember, high nitrogen fertilization can promote aphid populations. Also look at the aphid population with a hand lens. If you see numerous aphids that appear to be brown and somewhat rounded, you are mostly likely looking at an aphid mummy, which is an indication that parasitic wasps are feeding on them.
The excessively moist conditions outside have resulted in greenhouses that may be remaining too moist as well. Some greenhouses have had an abundance of fungus gnats and shore flies. From a distance, fungus gnats and shore flies look similar in the fact that they hover around the soil layer. However, fungus gnats are more mosquito-like. Although smaller than a housefly, shore flies look similar, with distinct, round, clear markings on their wings. Fungus gnats are often associated with minor root feeding and can result in increased risk of root pathogen. Shore flies feed primarily on algae; however, both of these pests can be a nuisance to customers.
The cool, wet conditions in greenhouses have caused some Botrytis infections on susceptible plants. Look for ring-like patterns and fuzzy growth on infected leaves. Close examination with a hand lens will reveal a grape-like cluster of fruiting bodies. As temperatures wane, this problem may go away; however, be aware that, sometimes, botrytis can cause cankers at the base of susceptible plants if high infection levels are left untreated. I have also observed cankers at the base of basil plants in greenhouse environments. This could be a result of Fusarium or Rhizoctonia, but a lab diagnosis is necessary for proper identification. One thing I noticed is that this problem seemed to be on one particular variety and has occurred frequently in the same greenhouse.
During greenhouse inspections, I also observed nutrient deficiency on Gerbera daisy, clematis, and tomatoes. The cool, wet weather can cause nutrient issues as well. Sometimes certain varieties of plants just do not seem to be actively growing enough to take up the available nutrients or additional nutrients that are applied. Sometimes it seems plants just do not respond to supplemental fertilizations. Then, when temperatures warm up, nutrient issues go away. Interveinal chlorosis is often an indicator of iron deficiency, but remember that other micronutrient deficiencies can cause this symptom as well.
