Michigan chestnut update – June 5, 2018
Growers are reporting tree mortality around Michigan.
Warmer than usual temperatures over the past weeks have driven degree-day accumulation to almost one week ahead of average. As buds broke and trees leaf out, a significant amount of winter injury was reported. Some older trees have died, but the majority of damage being reported is on small trees. Leaves are fully expanded and catkins are visible.
Potato leafhopper have arrived in Michigan orchards, but are at low levels. Chestnuts are sensitive to the saliva of potato leafhopper, which is injected by the insect while feeding. Damage to leaf tissue can cause reduced photosynthesis, which can damage trees and impact production and quality. Most injury occurs on new tissue on shoot terminals with potato leafhopper feeding near the edges of the leaves using piercing-sucking mouthparts. Many growers will utilize neonicotinoid insecticides applied as a drench or foliar application to control potato leafhoppers.
Adult potato leafhopper along chestnut midvein.
European red mite is active at low numbers. Affected leaves appear mottled, stippled or bronzed. Damaged leaves can become brittle, leading to early defoliation and reduced photosynthetic activity, which can lead to reduced nut size and return crop load in subsequent years as well as increased sensitivity to winter injury.
At this time, no treatment thresholds are established for mites in chestnut, but evidence from crops like cherry indicate some level of feeding is likely tolerable and higher populations can be tolerated as the season progresses through summer. European red mite appears to be the more prevalent mite species for chestnut producers, but keep an eye out for twospotted spider mites as well.
Rose chafer adults will be emerging soon. Rose chafers are considered a generalist pest and affect many crops, particularly those found on or near sandy soils or grassy areas. The adult beetles feed heavily on foliage and blossom parts of numerous horticultural crops in Michigan and can cause significant damage to chestnut orchards. Rose chafers can be particularly damaging on young trees with limited leaf area as they consume leaves in groups.
Neonicotinoids applied for potato leafhopper control will suppress rose chafers, but you may need to spot-treat with a pyrethroids or organophosphate insecticide to stop rapid defoliation of young trees.
Save the dates
Aug. 11 – The MSU Chestnut Research Program and the Ernie and Mabel Rogers Research Endowment are sponsoring an educational session at Rogers Reserve in Jackson, Michigan. The program will focus on applying pest management strategies in the orchard and in the processing facility: managing brown rot of chestnut, chestnut weevils, Asian chestnut gall wasp and Phytophthora root rot.
The event will feature Lucas Shuttleworth, world expert on brown rot of chestnut; Andrea Vannini, discussing brown rot and gall wasp of chestnut; Carmen Morales Rodriquez, discussing Phytophthora on chestnut; and Aroldo Mastrogregori, discussing processing chestnuts and using processing to manage insects and fungi. Stay tuned for more information.
Aug. 25 – MSU Extension and the Midwest Nut Producers Council will be hosting a Summer Farm Tour and Fundraiser in west central Michigan. Details to follow!
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This work is supported by the Crop Protection and Pest Management Program 2017-70006-27175 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.